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<meta name="theme-color" content="#b31b1b">  <title>Search | arXiv e-print repository</title> <script defer src="https://static.arxiv.org/static/base/1.0.0a5/fontawesome-free-5.11.2-web/js/all.js"></script> <link rel="stylesheet" href="https://static.arxiv.org/static/base/1.0.0a5/css/arxivstyle.css" /> <script type="text/x-mathjax-config"> MathJax.Hub.Config({ messageStyle: "none", extensions: ["tex2jax.js"], jax: ["input/TeX", "output/HTML-CSS"], tex2jax: { inlineMath: [ ['$','$'], ["\$","\$"] ], displayMath: [ ['$$','$$'], ["\\[","\\]"] ], processEscapes: true, ignoreClass: '.*', processClass: 'mathjax.*' }, TeX: { extensions: ["AMSmath.js", "AMSsymbols.js", "noErrors.js"], noErrors: { inlineDelimiters: ["$","$"], multiLine: false, style: { "font-size": "normal", "border": "" } } }, "HTML-CSS": { availableFonts: ["TeX"] } }); </script> <script src='//static.arxiv.org/MathJax-2.7.3/MathJax.js'></script> <script 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class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2503.01692">arXiv:2503.01692</a> <span> [<a href="https://arxiv.org/pdf/2503.01692">pdf</a>, <a href="https://arxiv.org/format/2503.01692">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> </div> <p class="title is-5 mathjax"> Hydrogenation of HOCO and formation of interstellar CO$_2$: A not so straightforward relation </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Molpeceres%2C+G">Germ谩n Molpeceres</a>, <a href="/search/?searchtype=author&query=Enrique-Romero%2C+J">Joan Enrique-Romero</a>, <a href="/search/?searchtype=author&query=Ishibashi%2C+A">Atsuki Ishibashi</a>, <a href="/search/?searchtype=author&query=Oba%2C+Y">Yasuhiro Oba</a>, <a href="/search/?searchtype=author&query=Hidaka%2C+H">Hiroshi Hidaka</a>, <a href="/search/?searchtype=author&query=Lamberts%2C+T">Thanja Lamberts</a>, <a href="/search/?searchtype=author&query=Aikawa%2C+Y">Yuri Aikawa</a>, <a href="/search/?searchtype=author&query=Watanabe%2C+N">Naoki Watanabe</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2503.01692v1-abstract-short" style="display: inline;"> Carbon dioxide (CO$_2$) is one of the most important interstellar molecules. While it is considered that it forms on the surface of interstellar dust grains, the exact contribution of different chemical mechanisms is still poorly constrained. Traditionally it is deemed that the CO + OH reaction occurring on top of ices is the main reaction path for its formation. Recent investigations showed that… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2503.01692v1-abstract-full').style.display = 'inline'; document.getElementById('2503.01692v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2503.01692v1-abstract-full" style="display: none;"> Carbon dioxide (CO$_2$) is one of the most important interstellar molecules. While it is considered that it forms on the surface of interstellar dust grains, the exact contribution of different chemical mechanisms is still poorly constrained. Traditionally it is deemed that the CO + OH reaction occurring on top of ices is the main reaction path for its formation. Recent investigations showed that in reality the reaction presents a more complex mechanism, requiring an additional H-abstraction step. Building on our previous works, we carried out a detailed investigation of such H abstraction reactions with the hydrogen atom as a reactant for the abstraction reaction. We found an unconventional chemistry for this reaction, markedly depending on the isomeric form of the HOCO radical prior to reaction. The favored reactions are t-HOCO + H -> CO + H$_2$O, c-HOCO + H -> CO$_2$ + H$_2$ and t/c-HOCO + H -> c/t-HCOOH. We estimate bounds for the rate constants of the less favored reaction channels, t-HOCO + H -> CO$_2$ + H and c-HOCO + H -> CO + H$_2$O, to be approximately 10$^{4-6}$ s$^{-1}$. However, these estimates should be interpreted cautiously due to the significant role of quantum tunneling in these reactions and the complex electronic structure of the involved molecules, which complicates their study. Our findings underscore the need for detailed investigation into the chemistry of interstellar CO$_2$ and pave the way for a reevaluation of its primary formation mechanisms in the interstellar medium. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2503.01692v1-abstract-full').style.display = 'none'; document.getElementById('2503.01692v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 3 March, 2025; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2025. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in MNRAS</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2502.10123">arXiv:2502.10123</a> <span> [<a href="https://arxiv.org/pdf/2502.10123">pdf</a>, <a href="https://arxiv.org/format/2502.10123">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> </div> <p class="title is-5 mathjax"> Modelling methanol and hydride formation in the JWST Ice Age era </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Jim%C3%A9nez-Serra%2C+I">Izaskun Jim茅nez-Serra</a>, <a href="/search/?searchtype=author&query=Meg%C3%ADas%2C+A">Andr茅s Meg铆as</a>, <a href="/search/?searchtype=author&query=Salaris%2C+J">Joseph Salaris</a>, <a href="/search/?searchtype=author&query=Cuppen%2C+H">Herma Cuppen</a>, <a href="/search/?searchtype=author&query=Taillard%2C+A">Ang猫le Taillard</a>, <a href="/search/?searchtype=author&query=Jin%2C+M">Miwha Jin</a>, <a href="/search/?searchtype=author&query=Wakelam%2C+V">Valentine Wakelam</a>, <a href="/search/?searchtype=author&query=Vasyunin%2C+A+I">Anton I. Vasyunin</a>, <a href="/search/?searchtype=author&query=Caselli%2C+P">Paola Caselli</a>, <a href="/search/?searchtype=author&query=Pendleton%2C+Y+J">Yvonne J. Pendleton</a>, <a href="/search/?searchtype=author&query=Dartois%2C+E">Emmanuel Dartois</a>, <a href="/search/?searchtype=author&query=Noble%2C+J+A">Jennifer A. Noble</a>, <a href="/search/?searchtype=author&query=Viti%2C+S">Serena Viti</a>, <a href="/search/?searchtype=author&query=Borshcheva%2C+K">Katerina Borshcheva</a>, <a href="/search/?searchtype=author&query=Garrod%2C+R+T">Robin T. Garrod</a>, <a href="/search/?searchtype=author&query=Lamberts%2C+T">Thanja Lamberts</a>, <a href="/search/?searchtype=author&query=Fraser%2C+H">Helen Fraser</a>, <a href="/search/?searchtype=author&query=Melnick%2C+G">Gary Melnick</a>, <a href="/search/?searchtype=author&query=McClure%2C+M">Melissa McClure</a>, <a href="/search/?searchtype=author&query=Rocha%2C+W">Will Rocha</a>, <a href="/search/?searchtype=author&query=Drozdovskaya%2C+M+N">Maria N. Drozdovskaya</a>, <a href="/search/?searchtype=author&query=Lis%2C+D+C">Dariusz C. Lis</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2502.10123v1-abstract-short" style="display: inline;"> (Abridged) JWST observations have measured the ice composition toward two highly-extinguished field stars in the Chamaeleon I cloud. The observed extinction excess on the long-wavelength side of the H2O ice band at 3 micron has been attributed to a mixture of CH3OH with ammonia hydrates, which suggests that CH3OH ice could have formed in a water-rich environment with little CO depletion. Laborator… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2502.10123v1-abstract-full').style.display = 'inline'; document.getElementById('2502.10123v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2502.10123v1-abstract-full" style="display: none;"> (Abridged) JWST observations have measured the ice composition toward two highly-extinguished field stars in the Chamaeleon I cloud. The observed extinction excess on the long-wavelength side of the H2O ice band at 3 micron has been attributed to a mixture of CH3OH with ammonia hydrates, which suggests that CH3OH ice could have formed in a water-rich environment with little CO depletion. Laboratory experiments and quantum chemical calculations suggest that CH3OH could form via the grain surface reactions CH3+OH and/or C+H2O in water-rich ices. However, no dedicated chemical modelling has been carried out thus far to test their efficiency and dependence on the astrochemical code employed. We model the ice chemistry in the Chamaeleon I cloud using a set of astrochemical codes (MAGICKAL, MONACO, Nautilus, UCLCHEM, and KMC simulations) to test the effects of the different code architectures and of the assumed ice chemistry. Our models show that the JWST ice observations are better reproduced for gas densities >1e5 cm-3 and collapse times >1e5 yr. CH3OH ice forms predominantly (>99%) via CO hydrogenation. The contribution of reactions CH3+OH and C+H2O, is negligible. The CO2 ice may form either via CO+OH or CO+O depending on the code. However, KMC simulations reveal that both mechanisms are efficient despite the low rate constant of the CO+O surface reaction. CH4 is largely underproduced for all codes except for UCLCHEM, for which a higher amount of atomic C is available during the initial translucent cloud phase. Large differences in the ice abundances are found at Tdust<12 K between diffusive and non-diffusive chemistry codes. This is due to the fact that non-diffusive chemistry takes over diffusive chemistry at such low Tdust. This could explain the rather constant ice chemical composition found in Chamaeleon I and other dense cores despite the different visual extinctions probed. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2502.10123v1-abstract-full').style.display = 'none'; document.getElementById('2502.10123v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 14 February, 2025; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2025. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted in A&A</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2411.19651">arXiv:2411.19651</a> <span> [<a href="https://arxiv.org/pdf/2411.19651">pdf</a>, <a href="https://arxiv.org/format/2411.19651">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202451505">10.1051/0004-6361/202451505 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Ice inventory towards the protostar Ced 110 IRS4 observed with the James Webb Space Telescope. Results from the ERS Ice Age program </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Rocha%2C+W+R+M">W. R. M. Rocha</a>, <a href="/search/?searchtype=author&query=McClure%2C+M+K">M. K. McClure</a>, <a href="/search/?searchtype=author&query=Sturm%2C+J+A">J. A. Sturm</a>, <a href="/search/?searchtype=author&query=Beck%2C+T+L">T. L. Beck</a>, <a href="/search/?searchtype=author&query=Smith%2C+Z+L">Z. L. Smith</a>, <a href="/search/?searchtype=author&query=Dickinson%2C+H">H. Dickinson</a>, <a href="/search/?searchtype=author&query=Sun%2C+F">F. Sun</a>, <a href="/search/?searchtype=author&query=Egami%2C+E">E. Egami</a>, <a href="/search/?searchtype=author&query=Boogert%2C+A+C+A">A. C. A. Boogert</a>, <a href="/search/?searchtype=author&query=Fraser%2C+H+J">H. J. Fraser</a>, <a href="/search/?searchtype=author&query=Dartois%2C+E">E. Dartois</a>, <a href="/search/?searchtype=author&query=Jimenez-Serra%2C+I">I. Jimenez-Serra</a>, <a href="/search/?searchtype=author&query=Noble%2C+J+A">J. A. Noble</a>, <a href="/search/?searchtype=author&query=Bergner%2C+J">J. Bergner</a>, <a href="/search/?searchtype=author&query=Caselli%2C+P">P. Caselli</a>, <a href="/search/?searchtype=author&query=Charnley%2C+S+B">S. B. Charnley</a>, <a href="/search/?searchtype=author&query=Chiar%2C+J">J. Chiar</a>, <a href="/search/?searchtype=author&query=Chu%2C+L">L. Chu</a>, <a href="/search/?searchtype=author&query=Cooke%2C+I">I. Cooke</a>, <a href="/search/?searchtype=author&query=Crouzet%2C+N">N. Crouzet</a>, <a href="/search/?searchtype=author&query=van+Dishoeck%2C+E+F">E. F. van Dishoeck</a>, <a href="/search/?searchtype=author&query=Drozdovskaya%2C+M+N">M. N. Drozdovskaya</a>, <a href="/search/?searchtype=author&query=Garrod%2C+R">R. Garrod</a>, <a href="/search/?searchtype=author&query=Harsono%2C+D">D. Harsono</a>, <a href="/search/?searchtype=author&query=Ioppolo%2C+S">S. Ioppolo</a> , et al. (15 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2411.19651v1-abstract-short" style="display: inline;"> This work focuses on the ice features toward the binary protostellar system Ced 110 IRS 4A and 4B, and observed with JWST as part of the Early Release Science Ice Age collaboration. We aim to explore the JWST observations of the binary protostellar system Ced~110~IRS4A and IRS4B to unveil and quantify the ice inventories toward these sources. We compare the ice abundances with those found for the… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.19651v1-abstract-full').style.display = 'inline'; document.getElementById('2411.19651v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2411.19651v1-abstract-full" style="display: none;"> This work focuses on the ice features toward the binary protostellar system Ced 110 IRS 4A and 4B, and observed with JWST as part of the Early Release Science Ice Age collaboration. We aim to explore the JWST observations of the binary protostellar system Ced~110~IRS4A and IRS4B to unveil and quantify the ice inventories toward these sources. We compare the ice abundances with those found for the same molecular cloud. The analysis is performed by fitting or comparing laboratory infrared spectra of ices to the observations. Spectral fits are carried out with the ENIIGMA fitting tool that searches for the best fit. For Ced~110~IRS4B, we detected the major ice species H$_2$O, CO, CO$_2$ and NH$_3$. All species are found in a mixture except for CO and CO$_2$, which have both mixed and pure ice components. In the case of Ced~110~IRS4A, we detected the same major species as in Ced~110~IRS4B, as well as the following minor species CH$_4$, SO$_2$, CH$_3$OH, OCN$^-$, NH$_4^+$ and HCOOH. Tentative detection of N$_2$O ice (7.75~$渭$m), forsterite dust (11.2~$渭$m) and CH$_3^+$ gas emission (7.18~$渭$m) in the primary source are also presented. Compared with the two lines of sight toward background stars in the Chameleon I molecular cloud, the protostar has similar ice abundances, except in the case of the ions that are higher in IRS4A. The clearest differences are the absence of the 7.2 and 7.4~$渭$m absorption features due to HCOO$^-$ and icy complex organic molecules in IRS4A and evidence of thermal processing in both IRS4A and IRS4B as probed by the CO$_2$ ice features. We conclude that the binary protostellar system Ced~110~IRS4A and IRS4B has a large inventory of icy species. The similar ice abundances in comparison to the starless regions in the same molecular cloud suggest that the chemical conditions of the protostar were set at earlier stages in the molecular cloud. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.19651v1-abstract-full').style.display = 'none'; document.getElementById('2411.19651v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 29 November, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">33 pages, 19 Figures. Accepted for publication in Astronomy & Astrophysics</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 693, A288 (2025) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2410.01373">arXiv:2410.01373</a> <span> [<a href="https://arxiv.org/pdf/2410.01373">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/ad8235">10.3847/1538-4357/ad8235 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Proposed importance of HOCO chemistry: Inefficient formation of CO$_2$ from CO and OH reactions on ice dust </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Ishibashi%2C+A">Atsuki Ishibashi</a>, <a href="/search/?searchtype=author&query=Molpeceres%2C+G">Germ谩n Molpeceres</a>, <a href="/search/?searchtype=author&query=Hidaka%2C+H">Hiroshi Hidaka</a>, <a href="/search/?searchtype=author&query=Oba%2C+Y">Yasuhiro Oba</a>, <a href="/search/?searchtype=author&query=Lamberts%2C+T">Thanja Lamberts</a>, <a href="/search/?searchtype=author&query=Watanabe%2C+N">Naoki Watanabe</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2410.01373v1-abstract-short" style="display: inline;"> With the advent of JWST ice observations, dedicated studies on the formation reactions of detected molecules are becoming increasingly important. One of the most interesting molecules in interstellar ice is CO$_2$. Despite its simplicity, the main formation reaction considered, CO + OH -> CO$_2$ + H through the energetic HOCO* intermediate on ice dust, is subject to uncertainty because it directly… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.01373v1-abstract-full').style.display = 'inline'; document.getElementById('2410.01373v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2410.01373v1-abstract-full" style="display: none;"> With the advent of JWST ice observations, dedicated studies on the formation reactions of detected molecules are becoming increasingly important. One of the most interesting molecules in interstellar ice is CO$_2$. Despite its simplicity, the main formation reaction considered, CO + OH -> CO$_2$ + H through the energetic HOCO* intermediate on ice dust, is subject to uncertainty because it directly competes with the stabilization of HOCO as a final product which is formed through energy dissipation of HOCO* to the water ice. When energy dissipation to the surface is effective during reaction, HOCO can be a dominant product. In this study, we experimentally demonstrate that the major product of the reaction is indeed not CO$_2$, but rather the highly reactive radical HOCO. The HOCO radical can later evolve into CO$_2$ through H-abstraction reactions, but these reactions compete with addition reactions, leading to the formation of carboxylic acids (R-COOH). Our results highlight the importance of HOCO chemistry and encourage further exploration of the chemistry of this radical. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.01373v1-abstract-full').style.display = 'none'; document.getElementById('2410.01373v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 2 October, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted in ApJ; 23 pages, 9 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2407.09730">arXiv:2407.09730</a> <span> [<a href="https://arxiv.org/pdf/2407.09730">pdf</a>, <a href="https://arxiv.org/format/2407.09730">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1021/acsearthspacechem.4c00150">10.1021/acsearthspacechem.4c00150 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Formation of S-bearing complex organic molecules in interstellar clouds via ice reactions with C2H2, HS, and atomic H </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Santos%2C+J+C">Julia C. Santos</a>, <a href="/search/?searchtype=author&query=Enrique-Romero%2C+J">Joan Enrique-Romero</a>, <a href="/search/?searchtype=author&query=Lamberts%2C+T">Thanja Lamberts</a>, <a href="/search/?searchtype=author&query=Linnartz%2C+H">Harold Linnartz</a>, <a href="/search/?searchtype=author&query=Chuang%2C+K">Ko-Ju Chuang</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2407.09730v1-abstract-short" style="display: inline;"> The chemical network governing interstellar sulfur has been the topic of unrelenting discussion for the past decades due to the conspicuous discrepancy between its expected and observed abundances in different interstellar environments. More recently, the astronomical detections of CH3CH2SH and CH2CS highlighted the importance of interstellar formation routes for sulfur-bearing organic molecules w… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.09730v1-abstract-full').style.display = 'inline'; document.getElementById('2407.09730v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2407.09730v1-abstract-full" style="display: none;"> The chemical network governing interstellar sulfur has been the topic of unrelenting discussion for the past decades due to the conspicuous discrepancy between its expected and observed abundances in different interstellar environments. More recently, the astronomical detections of CH3CH2SH and CH2CS highlighted the importance of interstellar formation routes for sulfur-bearing organic molecules with two carbon atoms. In this work, we perform a laboratory investigation of the solid-state chemistry resulting from the interaction between C2H2 molecules and SH radicals -- both thought to be present in interstellar icy mantles -- at 10 K. Reflection absorption infrared spectroscopy and quadrupole mass spectrometry combined with temperature-programmed desorption experiments are employed as analytical techniques. We confirm that SH radicals can kick-start a sulfur reaction network under interstellar cloud conditions and identify at least six sulfurated products: CH3CH2SH, CH2CHSH, HSCH2CH2SH, H2S2, and tentatively CH3CHS and CH2CS. Complementarily, we utilize computational calculations to pinpoint the reaction routes that play a role in the chemical network behind our experimental results. The main sulfur-bearing organic molecule formed under our experimental conditions is CH3CH2SH and its formation yield increases with the ratios of H to other reactants. It serves as a sink to the sulfur budget within the network, being formed at the expense of the other unsaturated products. The astrophysical implications of the chemical network proposed here are discussed. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.09730v1-abstract-full').style.display = 'none'; document.getElementById('2407.09730v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 12 July, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">9 figures, 2 pages, Accepted for publication in ACS Earth and Space Chemistry on July 5th 2024</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2303.12221">arXiv:2303.12221</a> <span> [<a href="https://arxiv.org/pdf/2303.12221">pdf</a>, <a href="https://arxiv.org/format/2303.12221">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/acc584">10.3847/1538-4357/acc584 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Detection of Interstellar $E$-1-cyano-1,3-butadiene in GOTHAM Observations of TMC-1 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Cooke%2C+I+R">Ilsa R. Cooke</a>, <a href="/search/?searchtype=author&query=Xue%2C+C">Ci Xue</a>, <a href="/search/?searchtype=author&query=Changala%2C+P+B">P. Bryan Changala</a>, <a href="/search/?searchtype=author&query=Shay%2C+H+T">Hannah Toru Shay</a>, <a href="/search/?searchtype=author&query=Byrne%2C+A+N">Alex N. Byrne</a>, <a href="/search/?searchtype=author&query=Tang%2C+Q+Y">Qi Yu Tang</a>, <a href="/search/?searchtype=author&query=Fried%2C+Z+T+P">Zachary T. P. Fried</a>, <a href="/search/?searchtype=author&query=Lee%2C+K+L+K">Kin Long Kelvin Lee</a>, <a href="/search/?searchtype=author&query=Loomis%2C+R+A">Ryan A. Loomis</a>, <a href="/search/?searchtype=author&query=Lamberts%2C+T">Thanja Lamberts</a>, <a href="/search/?searchtype=author&query=Remijan%2C+A">Anthony Remijan</a>, <a href="/search/?searchtype=author&query=Burkhardt%2C+A+M">Andrew M. Burkhardt</a>, <a href="/search/?searchtype=author&query=Herbst%2C+E">Eric Herbst</a>, <a href="/search/?searchtype=author&query=McCarthy%2C+M+C">Michael C. McCarthy</a>, <a href="/search/?searchtype=author&query=McGuire%2C+B+A">Brett A. McGuire</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2303.12221v1-abstract-short" style="display: inline;"> We report the detection of the lowest energy conformer of $E$-1-cyano-1,3-butadiene ($E$-1-C$_4$H$_5$CN), a linear isomer of pyridine, using the fourth data reduction of the GOTHAM deep spectral survey toward TMC-1 with the 100 m Green Bank Telescope. We performed velocity stacking and matched filter analyses using Markov chain Monte Carlo simulations and find evidence for the presence of this mol… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2303.12221v1-abstract-full').style.display = 'inline'; document.getElementById('2303.12221v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2303.12221v1-abstract-full" style="display: none;"> We report the detection of the lowest energy conformer of $E$-1-cyano-1,3-butadiene ($E$-1-C$_4$H$_5$CN), a linear isomer of pyridine, using the fourth data reduction of the GOTHAM deep spectral survey toward TMC-1 with the 100 m Green Bank Telescope. We performed velocity stacking and matched filter analyses using Markov chain Monte Carlo simulations and find evidence for the presence of this molecule at the 5.1$蟽$ level. We derive a total column density of $3.8^{+1.0}_{-0.9}\times 10^{10}$ cm$^{-2}$, which is predominantly found toward two of the four velocity components we observe toward TMC-1. We use this molecule as a proxy for constraining the gas-phase abundance of the apolar hydrocarbon 1,3-butadiene. Based on the three-phase astrochemical modeling code NAUTILUS and an expanded chemical network, our model underestimates the abundance of cyano-1,3-butadiene by a factor of 19, with a peak column density of $2.34 \times 10^{10}\ \mathrm{cm}^{-2}$ for 1,3-butadiene. Compared to the modeling results obtained in previous GOTHAM analyses, the abundance of 1,3-butadiene is increased by about two orders of magnitude. Despite this increase, the modeled abundances of aromatic species do not appear to change and remain underestimated by 1--4 orders of magnitude. Meanwhile, the abundances of the five-membered ring molecules increase proportionally with 1,3-butadiene by two orders of magnitudes. We discuss implications for bottom-up formation routes to aromatic and polycyclic aromatic molecules. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2303.12221v1-abstract-full').style.display = 'none'; document.getElementById('2303.12221v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 21 March, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2023. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2301.09140">arXiv:2301.09140</a> <span> [<a href="https://arxiv.org/pdf/2301.09140">pdf</a>, <a href="https://arxiv.org/format/2301.09140">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Earth and Planetary Astrophysics">astro-ph.EP</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/s41550-022-01875-w">10.1038/s41550-022-01875-w <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> An Ice Age JWST inventory of dense molecular cloud ices </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=McClure%2C+M+K">M. K. McClure</a>, <a href="/search/?searchtype=author&query=Rocha%2C+W+R+M">W. R. M. Rocha</a>, <a href="/search/?searchtype=author&query=Pontoppidan%2C+K+M">K. M. Pontoppidan</a>, <a href="/search/?searchtype=author&query=Crouzet%2C+N">N. Crouzet</a>, <a href="/search/?searchtype=author&query=Chu%2C+L+E+U">L. E. U. Chu</a>, <a href="/search/?searchtype=author&query=Dartois%2C+E">E. Dartois</a>, <a href="/search/?searchtype=author&query=Lamberts%2C+T">T. Lamberts</a>, <a href="/search/?searchtype=author&query=Noble%2C+J+A">J. A. Noble</a>, <a href="/search/?searchtype=author&query=Pendleton%2C+Y+J">Y. J. Pendleton</a>, <a href="/search/?searchtype=author&query=Perotti%2C+G">G. Perotti</a>, <a href="/search/?searchtype=author&query=Qasim%2C+D">D. Qasim</a>, <a href="/search/?searchtype=author&query=Rachid%2C+M+G">M. G. Rachid</a>, <a href="/search/?searchtype=author&query=Smith%2C+Z+L">Z. L. Smith</a>, <a href="/search/?searchtype=author&query=Sun%2C+F">Fengwu Sun</a>, <a href="/search/?searchtype=author&query=Beck%2C+T+L">Tracy L Beck</a>, <a href="/search/?searchtype=author&query=Boogert%2C+A+C+A">A. C. A. Boogert</a>, <a href="/search/?searchtype=author&query=Brown%2C+W+A">W. A. Brown</a>, <a href="/search/?searchtype=author&query=Caselli%2C+P">P. Caselli</a>, <a href="/search/?searchtype=author&query=Charnley%2C+S+B">S. B. Charnley</a>, <a href="/search/?searchtype=author&query=Cuppen%2C+H+M">Herma M. Cuppen</a>, <a href="/search/?searchtype=author&query=Dickinson%2C+H">H. Dickinson</a>, <a href="/search/?searchtype=author&query=Drozdovskaya%2C+M+N">M. N. Drozdovskaya</a>, <a href="/search/?searchtype=author&query=Egami%2C+E">E. Egami</a>, <a href="/search/?searchtype=author&query=Erkal%2C+J">J. Erkal</a>, <a href="/search/?searchtype=author&query=Fraser%2C+H">H. Fraser</a> , et al. (17 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2301.09140v1-abstract-short" style="display: inline;"> Icy grain mantles are the main reservoir of the volatile elements that link chemical processes in dark, interstellar clouds with the formation of planets and composition of their atmospheres. The initial ice composition is set in the cold, dense parts of molecular clouds, prior to the onset of star formation. With the exquisite sensitivity of JWST, this critical stage of ice evolution is now acces… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.09140v1-abstract-full').style.display = 'inline'; document.getElementById('2301.09140v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2301.09140v1-abstract-full" style="display: none;"> Icy grain mantles are the main reservoir of the volatile elements that link chemical processes in dark, interstellar clouds with the formation of planets and composition of their atmospheres. The initial ice composition is set in the cold, dense parts of molecular clouds, prior to the onset of star formation. With the exquisite sensitivity of JWST, this critical stage of ice evolution is now accessible for detailed study. Here we show the first results of the Early Release Science program "Ice Age" that reveal the rich composition of these dense cloud ices. Weak ices, including, $^{13}$CO$_2$, OCN$^-$, $^{13}$CO, OCS, and COMs functional groups are now detected along two pre-stellar lines of sight. The $^{12}$CO$_2$ ice profile indicates modest growth of the icy grains. Column densities of the major and minor ice species indicate that ices contribute between 2 and 19% of the bulk budgets of the key C, O, N, and S elements. Our results suggest that the formation of simple and complex molecules could begin early in a water-ice rich environment. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.09140v1-abstract-full').style.display = 'none'; document.getElementById('2301.09140v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 22 January, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">To appear in Nature Astronomy on January 23rd, 2023. 33 pages, 16 figures, 3 tables; includes extended and supplemental data sections. Part of the JWST Ice Age Early Release Science program's science enabling products. Enhanced spectra downloadable on Zenodo at the following DOI: 10.5281/zenodo.7501239</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2301.04324">arXiv:2301.04324</a> <span> [<a href="https://arxiv.org/pdf/2301.04324">pdf</a>, <a href="https://arxiv.org/format/2301.04324">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1093/mnras/stad139">10.1093/mnras/stad139 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Investigating the impact of reactions of C and CH with molecular hydrogen on a glycine gas-grain network </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Heyl%2C+J">Johannes Heyl</a>, <a href="/search/?searchtype=author&query=Lamberts%2C+T">Thanja Lamberts</a>, <a href="/search/?searchtype=author&query=Viti%2C+S">Serena Viti</a>, <a href="/search/?searchtype=author&query=Holdship%2C+J">Jonathan Holdship</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2301.04324v1-abstract-short" style="display: inline;"> The impact of including the reactions of C and CH with molecular hydrogen in a gas-grain network is assessed via a sensitivity analysis. To this end, we vary 3 parameters, namely, the efficiency for the reaction \ce{C + H2 -> CH2}, and the cosmic ray ionisation rate, with the third parameter being the final density of the collapsing dark cloud. A grid of 12 models is run to investigate the effect… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.04324v1-abstract-full').style.display = 'inline'; document.getElementById('2301.04324v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2301.04324v1-abstract-full" style="display: none;"> The impact of including the reactions of C and CH with molecular hydrogen in a gas-grain network is assessed via a sensitivity analysis. To this end, we vary 3 parameters, namely, the efficiency for the reaction \ce{C + H2 -> CH2}, and the cosmic ray ionisation rate, with the third parameter being the final density of the collapsing dark cloud. A grid of 12 models is run to investigate the effect of all parameters on the final molecular abundances of the chemical network. We find that including reactions with molecular hydrogen alters the hydrogen economy of the network; since some species are hydrogenated by molecular hydrogen, atomic hydrogen is freed up. The abundances of simple molecules produced from hydrogenation, such as \ce{CH4}, \ce{CH3OH} and \ce{NH3}, increase, and at the same time, more complex species such as glycine and its precursors see a significant decrease in their final abundances. We find that the precursors of glycine are being preferentially hydrogenated, and therefore glycine itself is produced less efficiently. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.04324v1-abstract-full').style.display = 'none'; document.getElementById('2301.04324v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 11 January, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">11 pages, 3 figures, accepted for publication in MNRAS</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2205.12284">arXiv:2205.12284</a> <span> [<a href="https://arxiv.org/pdf/2205.12284">pdf</a>, <a href="https://arxiv.org/format/2205.12284">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/2041-8213/ac7158">10.3847/2041-8213/ac7158 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> First experimental confirmation of the CH3O + H2CO -> CH3OH + HCO reaction: expanding the CH3OH formation mechanism in interstellar ices </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Santos%2C+J+C">Julia C. Santos</a>, <a href="/search/?searchtype=author&query=Chuang%2C+K">Ko-Ju Chuang</a>, <a href="/search/?searchtype=author&query=Lamberts%2C+T">Thanja Lamberts</a>, <a href="/search/?searchtype=author&query=Fedoseev%2C+G">Gleb Fedoseev</a>, <a href="/search/?searchtype=author&query=Ioppolo%2C+S">Sergio Ioppolo</a>, <a href="/search/?searchtype=author&query=Linnartz%2C+H">Harold Linnartz</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2205.12284v1-abstract-short" style="display: inline;"> The successive addition of H atoms to CO in the solid phase has been hitherto regarded as the primary route to form methanol in dark molecular clouds. However, recent Monte Carlo simulations of interstellar ices alternatively suggested the radical-molecule H-atom abstraction reaction CH3O + H2CO -> CH3OH + HCO, in addition to CH3O + H -> CH3OH, as a very promising and possibly dominating (70 - 90… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.12284v1-abstract-full').style.display = 'inline'; document.getElementById('2205.12284v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2205.12284v1-abstract-full" style="display: none;"> The successive addition of H atoms to CO in the solid phase has been hitherto regarded as the primary route to form methanol in dark molecular clouds. However, recent Monte Carlo simulations of interstellar ices alternatively suggested the radical-molecule H-atom abstraction reaction CH3O + H2CO -> CH3OH + HCO, in addition to CH3O + H -> CH3OH, as a very promising and possibly dominating (70 - 90 %) final step to form CH3OH in those environments. Here, we compare the contributions of these two steps leading to methanol by experimentally investigating hydrogenation reactions on H2CO and D2CO ices, which ensures comparable starting points between the two scenarios. The experiments are performed under ultrahigh vacuum conditions and astronomically relevant temperatures, with H:H2CO (or D2CO) flux ratios of 10:1 and 30:1. The radical-molecule route in the partially deuterated scenario, CHD2O + D2CO -> CHD2OD + DCO, is significantly hampered by the isotope effect in the D-abstraction process, and can thus be used as an artifice to probe the efficiency of this step. We observe a significantly smaller yield of D2CO + H products in comparison to H2CO + H, implying that the CH3O-induced abstraction route must play an important role in the formation of methanol in interstellar ices. Reflection-Absorption InfraRed Spectroscopy (RAIRS) and Temperature Programmed Desorption-Quadrupole Mass Spectrometry (TPD-QMS) analyses are used to quantify the species in the ice. Both analytical techniques indicate constant contributions of ~80 % for the abstraction route in the 10 - 16 K interval, which agrees well with the Monte Carlo conclusions. Additional H2CO + D experiments confirm these conclusions. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.12284v1-abstract-full').style.display = 'none'; document.getElementById('2205.12284v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 24 May, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">10 pages, 1 table, 6 figures. Accepted in the Astrophysical Journal Letters</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2202.04992">arXiv:2202.04992</a> <span> [<a href="https://arxiv.org/pdf/2202.04992">pdf</a>, <a href="https://arxiv.org/format/2202.04992">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1017/S1743921317009929">10.1017/S1743921317009929 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Surface astrochemistry: a computational chemistry perspective </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Cuppen%2C+H+M">H. M. Cuppen</a>, <a href="/search/?searchtype=author&query=Fredon%2C+A">A. Fredon</a>, <a href="/search/?searchtype=author&query=Lamberts%2C+T">T. Lamberts</a>, <a href="/search/?searchtype=author&query=Penteado%2C+E+M">E. M. Penteado</a>, <a href="/search/?searchtype=author&query=Simons%2C+M">M. Simons</a>, <a href="/search/?searchtype=author&query=Walsh%2C+C">C. Walsh</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2202.04992v1-abstract-short" style="display: inline;"> Molecules in space are synthesized via a large variety of gas-phase reactions, and reactions on dust-grain surfaces, where the surface acts as a catalyst. Especially, saturated, hydrogen-rich molecules are formed through surface chemistry. Astrochemical models have developed over the decades to understand the molecular processes in the interstellar medium, taking into account grain surface chemist… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2202.04992v1-abstract-full').style.display = 'inline'; document.getElementById('2202.04992v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2202.04992v1-abstract-full" style="display: none;"> Molecules in space are synthesized via a large variety of gas-phase reactions, and reactions on dust-grain surfaces, where the surface acts as a catalyst. Especially, saturated, hydrogen-rich molecules are formed through surface chemistry. Astrochemical models have developed over the decades to understand the molecular processes in the interstellar medium, taking into account grain surface chemistry. However, essential input information for gas-grain models, such as binding energies of molecules to the surface, have been derived experimentally only for a handful of species, leaving hundreds of species with highly uncertain estimates. Moreover, some fundamental processes are not well enough constrained to implement these into the models. The proceedings gives three examples how computational chemistry techniques can help answer fundamental questions regarding grain surface chemistry. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2202.04992v1-abstract-full').style.display = 'none'; document.getElementById('2202.04992v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 10 February, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">(12 pages, 8 figures)</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astrochemistry VII -- Through the Cosmos from Galaxies to Planets", proceedings of the IAU Symposium No. 332, 2017, Puerto Varas, Chile; eds. M. Cunningham, T. Millar and Y. Aikawa,p 293 - 304 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2112.09230">arXiv:2112.09230</a> <span> [<a href="https://arxiv.org/pdf/2112.09230">pdf</a>, <a href="https://arxiv.org/format/2112.09230">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202142414">10.1051/0004-6361/202142414 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Methoxymethanol Formation Starting from CO-Hydrogenation </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=He%2C+J">Jiao He</a>, <a href="/search/?searchtype=author&query=Simons%2C+M">Mart Simons</a>, <a href="/search/?searchtype=author&query=Fedoseev%2C+G">Gleb Fedoseev</a>, <a href="/search/?searchtype=author&query=Chuang%2C+K">Ko-Ju Chuang</a>, <a href="/search/?searchtype=author&query=Qasim%2C+D">Danna Qasim</a>, <a href="/search/?searchtype=author&query=Lamberts%2C+T">Thanja Lamberts</a>, <a href="/search/?searchtype=author&query=Ioppolo%2C+S">Sergio Ioppolo</a>, <a href="/search/?searchtype=author&query=McGuire%2C+B+A">Brett A. McGuire</a>, <a href="/search/?searchtype=author&query=Cuppen%2C+H">Herma Cuppen</a>, <a href="/search/?searchtype=author&query=Linnartz%2C+H">Harold Linnartz</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2112.09230v1-abstract-short" style="display: inline;"> Methoxymethanol (CH3OCH2OH, MM) has been identified through gas-phase signatures in both high- and low-mass star-forming regions. This molecule is expected to form upon hydrogen addition and abstraction reactions in CO-rich ice through radical recombination of CO hydrogenation products. The goal of this work is to investigate experimentally and theoretically the most likely solid-state MM reaction… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2112.09230v1-abstract-full').style.display = 'inline'; document.getElementById('2112.09230v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2112.09230v1-abstract-full" style="display: none;"> Methoxymethanol (CH3OCH2OH, MM) has been identified through gas-phase signatures in both high- and low-mass star-forming regions. This molecule is expected to form upon hydrogen addition and abstraction reactions in CO-rich ice through radical recombination of CO hydrogenation products. The goal of this work is to investigate experimentally and theoretically the most likely solid-state MM reaction channel -- the recombination of CH2OH and CH3O radicals -- for dark interstellar cloud conditions and to compare the formation efficiency with that of other species that were shown to form along the CO-hydrogenation line. Hydrogen atoms and CO or H2CO molecules are co-deposited on top of the predeposited H2O ice to mimic the conditions associated with the beginning of 'rapid' CO freeze-out. Quadrupole mass spectrometry is used to analyze the gas-phase COM composition following a temperature programmed desorption. Monte Carlo simulations are used for an astrochemical model comparing the MM formation efficiency with that of other COMs. Unambiguous detection of newly formed MM has been possible both in CO+H and H2CO+H experiments. The resulting abundance of MM with respect to CH3OH is about 0.05, which is about 6 times less than the value observed toward NGC 6334I and about 3 times less than the value reported for IRAS 16293B. The results of astrochemical simulations predict a similar value for the MM abundance with respect to CH3OH factors ranging between 0.06 to 0.03. We find that MM is formed by co-deposition of CO and H2CO with H atoms through the recombination of CH2OH and CH3O radicals. In both the experimental and modeling studies, the efficiency of this channel alone is not sufficient to explain the observed abundance of MM. These results indicate an incomplete knowledge of the reaction network or the presence of alternative solid-state or gas-phase formation mechanisms. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2112.09230v1-abstract-full').style.display = 'none'; document.getElementById('2112.09230v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 16 December, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">8 pages, 8 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 659, A65 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2111.08548">arXiv:2111.08548</a> <span> [<a href="https://arxiv.org/pdf/2111.08548">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/ac3834">10.3847/1538-4357/ac3834 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Hydrogenation of accreting C-atoms and CO molecules -- simulating ketene and acetaldehyde formation under dark and translucent cloud conditions </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Fedoseev%2C+G">Gleb Fedoseev</a>, <a href="/search/?searchtype=author&query=Qasim%2C+D">Danna Qasim</a>, <a href="/search/?searchtype=author&query=Chuang%2C+K">Ko-Ju Chuang</a>, <a href="/search/?searchtype=author&query=Ioppolo%2C+S">Sergio Ioppolo</a>, <a href="/search/?searchtype=author&query=Lamberts%2C+T">Thanja Lamberts</a>, <a href="/search/?searchtype=author&query=van+Dishoeck%2C+E+F">Ewine F. van Dishoeck</a>, <a href="/search/?searchtype=author&query=Linnartz%2C+H">Harold Linnartz</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2111.08548v1-abstract-short" style="display: inline;"> Simple and complex organic molecules (COMs) are observed along different phases of star and planet formation and have been successfully identified in prestellar environments such as dark and translucent clouds. Yet the picture of organic molecule formation at those earliest stages of star formation is not complete and an important reason is the lack of specific laboratory experiments that simulate… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2111.08548v1-abstract-full').style.display = 'inline'; document.getElementById('2111.08548v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2111.08548v1-abstract-full" style="display: none;"> Simple and complex organic molecules (COMs) are observed along different phases of star and planet formation and have been successfully identified in prestellar environments such as dark and translucent clouds. Yet the picture of organic molecule formation at those earliest stages of star formation is not complete and an important reason is the lack of specific laboratory experiments that simulate carbon atom addition reactions on icy surfaces of interstellar grains. Here we present experiments in which CO molecules as well as C- and H-atoms are co-deposited with H$_2$O molecules on a 10 K surface mimicking the ongoing formation of an "H$_2$O-rich" ice mantle. To simulate the effect of impacting C-atoms and resulting surface reactions with ice components, a specialized C-atom beam source is used, implemented on SURFRESIDE$^3$, an UHV cryogenic setup. Formation of ketene (CH$_2$CO) in the solid state is observed "in situ" by means of reflection absorption IR spectroscopy. C$^1$$^8$O and D isotope labelled experiments are performed to further validate the formation of ketene. Data analysis supports that CH$_2$CO is formed through C-atom addition to a CO-molecule, followed by successive hydrogenation transferring the formed :CCO into ketene. Efficient formation of ketene is in line with the absence of an activation barrier in C+CO reaction reported in the literature. We also discuss and provide experimental evidence for the formation of acetaldehyde (CH$_3$CHO) and possible formation of ethanol (CH$_3$CH$_2$OH), two COM derivatives of CH$_2$CO hydrogenation. The underlying reaction network is presented and the astrochemical implications of the derived pathways are discussed. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2111.08548v1-abstract-full').style.display = 'none'; document.getElementById('2111.08548v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 16 November, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted by ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2110.15887">arXiv:2110.15887</a> <span> [<a href="https://arxiv.org/pdf/2110.15887">pdf</a>, <a href="https://arxiv.org/format/2110.15887">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1021/acs.jpclett.1c02760">10.1021/acs.jpclett.1c02760 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Carbon Atom Reactivity with Amorphous Solid Water: H$_2$O Catalyzed Formation of H$_2$CO </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Molpeceres%2C+G">Germ谩n Molpeceres</a>, <a href="/search/?searchtype=author&query=K%C3%A4stner%2C+J">Johannes K盲stner</a>, <a href="/search/?searchtype=author&query=Fedoseev%2C+G">Gleb Fedoseev</a>, <a href="/search/?searchtype=author&query=Qasim%2C+D">Danna Qasim</a>, <a href="/search/?searchtype=author&query=Sch%C3%B6mig%2C+R">Richard Sch枚mig</a>, <a href="/search/?searchtype=author&query=Linnartz%2C+H">Harold Linnartz</a>, <a href="/search/?searchtype=author&query=Lamberts%2C+T">Thanja Lamberts</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2110.15887v1-abstract-short" style="display: inline;"> We report new computational and experimental evidence of an efficient and astrochemically relevant formation route to formaldehyde (H$_2$CO). This simplest carbonylic compound is central to the formation of complex organics in cold interstellar clouds, and is generally regarded to be formed by the hydrogenation of solid-state carbon monoxide. We demonstrate H$_2$CO formation via the reaction of ca… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2110.15887v1-abstract-full').style.display = 'inline'; document.getElementById('2110.15887v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2110.15887v1-abstract-full" style="display: none;"> We report new computational and experimental evidence of an efficient and astrochemically relevant formation route to formaldehyde (H$_2$CO). This simplest carbonylic compound is central to the formation of complex organics in cold interstellar clouds, and is generally regarded to be formed by the hydrogenation of solid-state carbon monoxide. We demonstrate H$_2$CO formation via the reaction of carbon atoms with amorphous solid water. Crucial to our proposed mechanism is a concerted proton transfer catalyzed by the water hydrogen bonding network. Consequently, the reactions $^3$C + H$_2$O -> $^3$HCOH and $^1$HCOH -> $^1$H$_2$CO can take place with low or without barriers, contrary to the high-barrier traditional internal hydrogen migration. These low barriers or absence thereof explain the very small kinetic isotope effect in our experiments when comparing the formation of H$_2$CO to D$_2$CO. Our results reconcile the disagreement found in the literature on the reaction route: C + H$_2$O -> H$_2$CO. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2110.15887v1-abstract-full').style.display = 'none'; document.getElementById('2110.15887v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 29 October, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in JPCL</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2110.15881">arXiv:2110.15881</a> <span> [<a href="https://arxiv.org/pdf/2110.15881">pdf</a>, <a href="https://arxiv.org/format/2110.15881">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/ac51d1">10.3847/1538-4357/ac51d1 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Methane formation in cold regions from carbon atoms and molecular hydrogen </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Lamberts%2C+T">Thanja Lamberts</a>, <a href="/search/?searchtype=author&query=Fedoseev%2C+G">Gleb Fedoseev</a>, <a href="/search/?searchtype=author&query=van+Hemert%2C+M">Marc van Hemert</a>, <a href="/search/?searchtype=author&query=Qasim%2C+D">Danna Qasim</a>, <a href="/search/?searchtype=author&query=Chuang%2C+K">Ko-Ju Chuang</a>, <a href="/search/?searchtype=author&query=Santos%2C+J+C">Julia C. Santos</a>, <a href="/search/?searchtype=author&query=Linnartz%2C+H">Harold Linnartz</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2110.15881v1-abstract-short" style="display: inline;"> Methane is typically thought to be formed in the solid state on the surface of cold interstellar icy grain mantles via the successive atomic hydrogenation of a carbon atom. In the current work we investigate the potential role of molecular hydrogen in the CH$_4$ reaction network. We make use of an ultra-high vacuum cryogenic setup combining an atomic carbon atom beam and both atomic and/or molecul… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2110.15881v1-abstract-full').style.display = 'inline'; document.getElementById('2110.15881v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2110.15881v1-abstract-full" style="display: none;"> Methane is typically thought to be formed in the solid state on the surface of cold interstellar icy grain mantles via the successive atomic hydrogenation of a carbon atom. In the current work we investigate the potential role of molecular hydrogen in the CH$_4$ reaction network. We make use of an ultra-high vacuum cryogenic setup combining an atomic carbon atom beam and both atomic and/or molecular beams of hydrogen and deuterium on a H$_2$O ice. These experiments lead to the formation of methane isotopologues detected in situ through reflection absorption infrared spectroscopy. Most notably, CH$_4$ is formed in an experiment combining C atoms with H$_2$ on amorphous solid water, albeit slower than in experiments with H atoms present. Furthermore, CH$_2$D$_2$ is detected in an experiment of C atoms with H$_2$ and D$_2$ on H$_2$O ice. CD$_4$, however, is only formed when D atoms are present in the experiment. These findings have been rationalized by means of computational chemical insights. This leads to the following conclusions: a) the reaction C + H$_2$ -> CH$_2$ can take place, although not barrierless in the presence of water, b) the reaction CH + H$_2$ -> CH$_3$ is barrierless, but has not yet been included in astrochemical models, c) the reactions CH$_2$ + H$_2$ -> CH$_3$ + H and CH$_3$ + H$_2$ -> CH$_4$ + H can take place only via a tunneling mechanism and d) molecular hydrogen possibly plays a more important role in the solid-state formation of methane than assumed so far. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2110.15881v1-abstract-full').style.display = 'none'; document.getElementById('2110.15881v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 29 October, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Submitted to ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2002.06101">arXiv:2002.06101</a> <span> [<a href="https://arxiv.org/pdf/2002.06101">pdf</a>, <a href="https://arxiv.org/format/2002.06101">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1093/mnras/staa484">10.1093/mnras/staa484 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Revisiting the reactivity between HCO and CH$_3$ on interstellar grain surfaces </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Enrique-Romero%2C+J">J. Enrique-Romero</a>, <a href="/search/?searchtype=author&query=%C3%81lvarez-Barcia%2C+S">S. 脕lvarez-Barcia</a>, <a href="/search/?searchtype=author&query=Kolb%2C+F+J">F. J. Kolb</a>, <a href="/search/?searchtype=author&query=Rimola%2C+A">A. Rimola</a>, <a href="/search/?searchtype=author&query=Ceccarelli%2C+C">C. Ceccarelli</a>, <a href="/search/?searchtype=author&query=Balucani%2C+N">N. Balucani</a>, <a href="/search/?searchtype=author&query=Meisner%2C+J">J. Meisner</a>, <a href="/search/?searchtype=author&query=Ugliengo%2C+P">P. Ugliengo</a>, <a href="/search/?searchtype=author&query=Lamberts%2C+T">T. Lamberts</a>, <a href="/search/?searchtype=author&query=K%C3%A4stner%2C+J">J. K盲stner</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2002.06101v1-abstract-short" style="display: inline;"> Formation of interstellar complex organic molecules is currently thought to be dominated by the barrierless coupling between radicals on the interstellar icy grain surfaces. Previous standard DFT results on the reactivity between CH$_3$ and HCO on amorphous water surfaces, showed that formation of CH$_4$ + CO by H transfer from HCO to CH$_3$ assisted by water molecules of the ice was the dominant… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2002.06101v1-abstract-full').style.display = 'inline'; document.getElementById('2002.06101v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2002.06101v1-abstract-full" style="display: none;"> Formation of interstellar complex organic molecules is currently thought to be dominated by the barrierless coupling between radicals on the interstellar icy grain surfaces. Previous standard DFT results on the reactivity between CH$_3$ and HCO on amorphous water surfaces, showed that formation of CH$_4$ + CO by H transfer from HCO to CH$_3$ assisted by water molecules of the ice was the dominant channel. However, the adopted description of the electronic structure of the biradical (i.e., CH$_3$/HCO) system was inadequate (without the broken-symmetry (BS) approach). In this work, we revisit the original results by means of BS-DFT both in gas phase and with one water molecule simulating the role of the ice. Results indicate that adoption of BS-DFT is mandatory to describe properly biradical systems. In the presence of the single water molecule, the water-assisted H transfer exhibits a high energy barrier. In contrast, CH$_3$CHO formation is found to be barrierless. However, direct H transfer from HCO to CH$_3$ to give CO and CH$_4$ presents a very low energy barrier, hence being a potential competitive channel to the radical coupling and indicating, moreover, that the physical insights ofthe original work remain valid. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2002.06101v1-abstract-full').style.display = 'none'; document.getElementById('2002.06101v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 14 February, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Submitted to MNRAS main journal. For associated supporting material refer to the publication in MNRAS. Accepted 2020 February 14. Received 2020 February 14</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2001.04895">arXiv:2001.04895</a> <span> [<a href="https://arxiv.org/pdf/2001.04895">pdf</a>, <a href="https://arxiv.org/format/2001.04895">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/201936522">10.1051/0004-6361/201936522 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Formation of COMs through CO hydrogenation on interstellar grains </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Simons%2C+M+A+J">M. A. J. Simons</a>, <a href="/search/?searchtype=author&query=Lamberts%2C+T">T. Lamberts</a>, <a href="/search/?searchtype=author&query=Cuppen%2C+H+M">H. M. Cuppen</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2001.04895v1-abstract-short" style="display: inline;"> Glycoaldehyde, ethylene glycol, and methyl formate are complex organic molecules that have been observed in dark molecular clouds. Because there is no efficient gas-phase route to produce these species, it is expected that a low-temperature surface route existst that does not require energetic processing. CO hydrogenation experiments at low temperatures showed that this is indeed the case. Glyoxal… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2001.04895v1-abstract-full').style.display = 'inline'; document.getElementById('2001.04895v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2001.04895v1-abstract-full" style="display: none;"> Glycoaldehyde, ethylene glycol, and methyl formate are complex organic molecules that have been observed in dark molecular clouds. Because there is no efficient gas-phase route to produce these species, it is expected that a low-temperature surface route existst that does not require energetic processing. CO hydrogenation experiments at low temperatures showed that this is indeed the case. Glyoxal can form through recombination of two HCO radicals and is then further hydrogenated. Here we aim to constrain the methyl formate, glycolaldehyde, and ethylene glycol formation on the surface of interstellar dust grains through this cold and dark formation route. We also probe the dependence of the grain mantle composition on the initial gas-phase composition and the dust temperature. A full CO hydrogenation reaction network was built based on quantum chemical calculations for the rate constants and branching ratios. This network was used in combination with a microscopic kinetic Monte Carlo simulation to simulate ice chemistry, taking into account all positional information. After benchmarking the model against CO-hydrogenation experiments, simulations under molecular cloud conditions were performed. COMs are formed in all interstellar conditions we studied, even at temperatures as low as 8 K. This is because the HCO + HCO reaction can occur when HCO radicals are formed close to each other and do not require to diffuse. Relatively low abundances of methyl formate are formed. The final COM abundances depend more on the H-to-CO ratio and less on temperature. Only above 16 K, where CO build-up is less efficient, does temperature start to play a role. Molecular hydrogen is predominantly formed through abstraction reactions on the surface. Our simulations are in agreement with observed COM ratios for mantles that have been formed at low temperatures. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2001.04895v1-abstract-full').style.display = 'none'; document.getElementById('2001.04895v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 14 January, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 634, A52 (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1911.01239">arXiv:1911.01239</a> <span> [<a href="https://arxiv.org/pdf/1911.01239">pdf</a>, <a href="https://arxiv.org/ps/1911.01239">ps</a>, <a href="https://arxiv.org/format/1911.01239">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/ab5360">10.3847/1538-4357/ab5360 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Efficient Production of S$_8$ in Interstellar Ices: The effects of cosmic ray-driven radiation chemistry and non-diffusive bulk reactions </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Shingledecker%2C+C+N">Christopher N. Shingledecker</a>, <a href="/search/?searchtype=author&query=Lamberts%2C+T">Thanja Lamberts</a>, <a href="/search/?searchtype=author&query=Laas%2C+J+C">Jacob C. Laas</a>, <a href="/search/?searchtype=author&query=Vasyunin%2C+A">Anton Vasyunin</a>, <a href="/search/?searchtype=author&query=Herbst%2C+E">Eric Herbst</a>, <a href="/search/?searchtype=author&query=Kaestner%2C+J">Johannes Kaestner</a>, <a href="/search/?searchtype=author&query=Caselli%2C+P">Paola Caselli</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1911.01239v1-abstract-short" style="display: inline;"> In this work, we reexamine sulfur chemistry occurring on and in the ice mantles of interstellar dust grains, and report the effects of two new modifications to standard astrochemical models; namely, (a) the incorporation of cosmic ray-driven radiation chemistry and (b) the assumption of fast, non-diffusive reactions for key radicals in the bulk. Results from our models of dense molecular clouds sh… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1911.01239v1-abstract-full').style.display = 'inline'; document.getElementById('1911.01239v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1911.01239v1-abstract-full" style="display: none;"> In this work, we reexamine sulfur chemistry occurring on and in the ice mantles of interstellar dust grains, and report the effects of two new modifications to standard astrochemical models; namely, (a) the incorporation of cosmic ray-driven radiation chemistry and (b) the assumption of fast, non-diffusive reactions for key radicals in the bulk. Results from our models of dense molecular clouds show that these changes can have a profound influence on the abundances of sulfur-bearing species in ice mantles, including a reduction in the abundance of solid-phase H$_2$S and HS, and a significant increase in the abundances of OCS, SO$_2$, as well as pure allotropes of sulfur, especially S$_8$. These pure-sulfur species - though nearly impossible to observe directly - have long been speculated to be potential sulfur reservoirs and our results represent possibly the most accurate estimates yet of their abundances in the dense ISM. Moreover, the results of these updated models are found to be in good agreement with available observational data. Finally, we examine the implications of our findings with regard to the as-yet-unknown sulfur reservoir thought to exist in dense interstellar environments. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1911.01239v1-abstract-full').style.display = 'none'; document.getElementById('1911.01239v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 4 November, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">ApJ, accepted: 37 pages, 8 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1906.06508">arXiv:1906.06508</a> <span> [<a href="https://arxiv.org/pdf/1906.06508">pdf</a>, <a href="https://arxiv.org/format/1906.06508">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1017/S174392131900975X">10.1017/S174392131900975X <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Synthesis of solid-state Complex Organic Molecules through accretion of simple species at low temperatures </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Qasim%2C+D">D. Qasim</a>, <a href="/search/?searchtype=author&query=Fedoseev%2C+G">G. Fedoseev</a>, <a href="/search/?searchtype=author&query=Chuang%2C+K+-">K. -J. Chuang</a>, <a href="/search/?searchtype=author&query=Taquet%2C+V">V. Taquet</a>, <a href="/search/?searchtype=author&query=Lamberts%2C+T">T. Lamberts</a>, <a href="/search/?searchtype=author&query=He%2C+J">J. He</a>, <a href="/search/?searchtype=author&query=Ioppolo%2C+S">S. Ioppolo</a>, <a href="/search/?searchtype=author&query=van+Dishoeck%2C+E+F">E. F. van Dishoeck</a>, <a href="/search/?searchtype=author&query=Linnartz%2C+H">H. Linnartz</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1906.06508v1-abstract-short" style="display: inline;"> Complex organic molecules (COMs) have been detected in the gas-phase in cold and lightless molecular cores. Recent solid-state laboratory experiments have provided strong evidence that COMs can be formed on icy grains through 'non-energetic' processes. In this contribution, we show that propanal and 1-propanol can be formed in this way at the low temperature of 10 K. Propanal has already been dete… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1906.06508v1-abstract-full').style.display = 'inline'; document.getElementById('1906.06508v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1906.06508v1-abstract-full" style="display: none;"> Complex organic molecules (COMs) have been detected in the gas-phase in cold and lightless molecular cores. Recent solid-state laboratory experiments have provided strong evidence that COMs can be formed on icy grains through 'non-energetic' processes. In this contribution, we show that propanal and 1-propanol can be formed in this way at the low temperature of 10 K. Propanal has already been detected in space. 1-propanol is an astrobiologically relevant molecule, as it is a primary alcohol, and has not been astronomically detected. Propanal is the major product formed in the C2H2 + CO + H experiment, and 1-propanol is detected in the subsequent propanal + H experiment. The results are published in Qasim et al. (2019c). ALMA observations towards IRAS 16293-2422B are discussed and provide a 1-propanol:propanal upper limit of < 0.35 - 0.55, which are complemented by computationally-derived activation barriers in addition to the performed laboratory experiments. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1906.06508v1-abstract-full').style.display = 'none'; document.getElementById('1906.06508v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 15 June, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Proceedings IAU Symposium No. 350, 2019, Laboratory Astrophysics: from Observations to Interpretation</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1905.07801">arXiv:1905.07801</a> <span> [<a href="https://arxiv.org/pdf/1905.07801">pdf</a>, <a href="https://arxiv.org/format/1905.07801">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/201935217">10.1051/0004-6361/201935217 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Formation of interstellar propanal and 1-propanol ice: a pathway involving solid-state CO hydrogenation </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Qasim%2C+D">D. Qasim</a>, <a href="/search/?searchtype=author&query=Fedoseev%2C+G">G. Fedoseev</a>, <a href="/search/?searchtype=author&query=Chuang%2C+K+-">K. -J. Chuang</a>, <a href="/search/?searchtype=author&query=Taquet%2C+V">V. Taquet</a>, <a href="/search/?searchtype=author&query=Lamberts%2C+T">T. Lamberts</a>, <a href="/search/?searchtype=author&query=He%2C+J">J. He</a>, <a href="/search/?searchtype=author&query=Ioppolo%2C+S">S. Ioppolo</a>, <a href="/search/?searchtype=author&query=van+Dishoeck%2C+E+F">E. F. van Dishoeck</a>, <a href="/search/?searchtype=author&query=Linnartz%2C+H">H. Linnartz</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1905.07801v3-abstract-short" style="display: inline;"> 1-propanol (CH3CH2CH2OH) is a three carbon-bearing representative of primary linear alcohols that may have its origin in the cold dark cores in interstellar space. To test this, we investigated in the laboratory whether 1-propanol ice can be formed along pathways possibly relevant to the prestellar core phase. We aim to show in a two-step approach that 1-propanol can be formed through reaction ste… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1905.07801v3-abstract-full').style.display = 'inline'; document.getElementById('1905.07801v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1905.07801v3-abstract-full" style="display: none;"> 1-propanol (CH3CH2CH2OH) is a three carbon-bearing representative of primary linear alcohols that may have its origin in the cold dark cores in interstellar space. To test this, we investigated in the laboratory whether 1-propanol ice can be formed along pathways possibly relevant to the prestellar core phase. We aim to show in a two-step approach that 1-propanol can be formed through reaction steps that are expected to take place during the heavy CO freeze-out stage by adding C2H2 into the CO + H hydrogenation network via the formation of propanal (CH3CH2CHO) as an intermediate and its subsequent hydrogenation. Temperature programmed desorption-quadrupole mass spectrometry (TPD-QMS) is used to identify the newly formed propanal and 1-propanol. Reflection absorption infrared spectroscopy (RAIRS) is used as a complementary diagnostic tool. The mechanisms that can contribute to the formation of solid-state propanal and 1-propanol, as well as other organic compounds, during the heavy CO freeze-out stage are constrained by both laboratory experiments and theoretical calculations. Here it is shown that recombination of HCO radicals, formed upon CO hydrogenation, with radicals formed upon C2H2 processing - H2CCH and H3CCH2 - offers possible reaction pathways to solid-state propanal and 1-propanol formation. This extends the already important role of the CO hydrogenation chain in the formation of larger COMs (complex organic molecules). The results are used to compare with ALMA observations. The resulting 1-propanol:propanal ratio concludes an upper limit of < 0:35-0:55, which is complemented by computationally-derived activation barriers in addition to the experimental results. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1905.07801v3-abstract-full').style.display = 'none'; document.getElementById('1905.07801v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 22 May, 2019; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 19 May, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in Astronomy and Astrophysics</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 627, A1 (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1905.06767">arXiv:1905.06767</a> <span> [<a href="https://arxiv.org/pdf/1905.06767">pdf</a>, <a href="https://arxiv.org/format/1905.06767">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/201935068">10.1051/0004-6361/201935068 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Extension of the HCOOH and CO2 solid-state reaction network during the CO freeze-out stage: inclusion of H2CO </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Qasim%2C+D">D. Qasim</a>, <a href="/search/?searchtype=author&query=Lamberts%2C+T">T. Lamberts</a>, <a href="/search/?searchtype=author&query=He%2C+J">J. He</a>, <a href="/search/?searchtype=author&query=Chuang%2C+K+-">K. -J. Chuang</a>, <a href="/search/?searchtype=author&query=Fedoseev%2C+G">G. Fedoseev</a>, <a href="/search/?searchtype=author&query=Ioppolo%2C+S">S. Ioppolo</a>, <a href="/search/?searchtype=author&query=Boogert%2C+A+C+A">A. C. A. Boogert</a>, <a href="/search/?searchtype=author&query=Linnartz%2C+H">H. Linnartz</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1905.06767v3-abstract-short" style="display: inline;"> Formic acid (HCOOH) and carbon dioxide (CO2) are simple species that have been detected in the interstellar medium. The solid-state formation pathways of these species under experimental conditions relevant to prestellar cores are primarily based off of weak infrared transitions of the HOCO complex and usually pertain to the H2O-rich ice phase, and therefore more experimental data are desired. In… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1905.06767v3-abstract-full').style.display = 'inline'; document.getElementById('1905.06767v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1905.06767v3-abstract-full" style="display: none;"> Formic acid (HCOOH) and carbon dioxide (CO2) are simple species that have been detected in the interstellar medium. The solid-state formation pathways of these species under experimental conditions relevant to prestellar cores are primarily based off of weak infrared transitions of the HOCO complex and usually pertain to the H2O-rich ice phase, and therefore more experimental data are desired. In this article, we present a new and additional solid-state reaction pathway that can form HCOOH and CO2 ice at 10 K 'non-energetically' in the laboratory under conditions related to the "heavy" CO freeze-out stage in dense interstellar clouds, i.e., by the hydrogenation of an H2CO:O2 ice mixture. This pathway is used to piece together the HCOOH and CO2 formation routes when H2CO or CO reacts with H and OH radicals. Temperature programmed desorption - quadrupole mass spectrometry (TPD-QMS) is used to confirm the formation and pathways of newly synthesized ice species as well as to provide information on relative molecular abundances. Reflection absorption infrared spectroscopy (RAIRS) is additionally employed to characterize reaction products and determine relative molecular abundances. We find that for the conditions investigated in conjunction with theoretical results from the literature, H+HOCO and HCO+OH lead to the formation of HCOOH ice in our experiments. Which reaction is more dominant can be determined if the H+HOCO branching ratio is more constrained by computational simulations, as the HCOOH:CO2 abundance ratio is experimentally measured to be around 1.8:1. H+HOCO is more likely than OH+CO (without HOCO formation) to form CO2. Isotope experiments presented here further validate that H+HOCO is the dominant route for HCOOH ice formation in a CO-rich CO:O2 ice mixture that is hydrogenated. These data will help in the search and positive identification of HCOOH ice in prestellar cores. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1905.06767v3-abstract-full').style.display = 'none'; document.getElementById('1905.06767v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 21 May, 2019; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 16 May, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in Astronomy and Astrophysics</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 626, A118 (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1905.05063">arXiv:1905.05063</a> <span> [<a href="https://arxiv.org/pdf/1905.05063">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1021/acsearthspacechem.9b00062">10.1021/acsearthspacechem.9b00062 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Alcohols on the rocks: solid-state formation in a H3CCCH + OH cocktail under dark cloud conditions </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Qasim%2C+D">D. Qasim</a>, <a href="/search/?searchtype=author&query=Fedoseev%2C+G">G. Fedoseev</a>, <a href="/search/?searchtype=author&query=Lamberts%2C+T">T. Lamberts</a>, <a href="/search/?searchtype=author&query=Chuang%2C+K+-">K. -J. Chuang</a>, <a href="/search/?searchtype=author&query=He%2C+J">J. He</a>, <a href="/search/?searchtype=author&query=Ioppolo%2C+S">S. Ioppolo</a>, <a href="/search/?searchtype=author&query=K%C3%A4stner%2C+J">J. K盲stner</a>, <a href="/search/?searchtype=author&query=Linnartz%2C+H">H. Linnartz</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1905.05063v1-abstract-short" style="display: inline;"> A number of recent experimental studies have shown that solid-state complex organic molecules (COMs) can form under conditions that are relevant to the CO freeze-out stage in dense clouds. In this work, we show that alcohols can be formed well before the CO freeze-out stage (i.e., in the H2O-rich ice phase). This joint experimental and computational investigation shows that the isomers, n- and i-p… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1905.05063v1-abstract-full').style.display = 'inline'; document.getElementById('1905.05063v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1905.05063v1-abstract-full" style="display: none;"> A number of recent experimental studies have shown that solid-state complex organic molecules (COMs) can form under conditions that are relevant to the CO freeze-out stage in dense clouds. In this work, we show that alcohols can be formed well before the CO freeze-out stage (i.e., in the H2O-rich ice phase). This joint experimental and computational investigation shows that the isomers, n- and i-propanol (H3CCH2CH2OH and H3CCHOHCH3) and n- and i-propenol (H3CCHCHOH and H3CCOHCH2), can be formed in radical-addition reactions starting from propyne (H3CCCH) + OH at the low temperature of 10 K, where H3CCCH is one of the simplest representatives of stable carbon chains already identified in the interstellar medium (ISM). The resulting average abundance ratio of 1:1 for n-propanol:i-propanol is aligned with the conclusions from the computational work that the geometric orientation of strongly interacting species is influential to the extent of which 'mechanism' is participating, and that an assortment of geometries leads to an averaged-out effect. Three isomers of propanediol are also tentatively identified in the experiments. It is also shown that propene and propane (H3CCHCH2 and H3CCH2CH3) are formed from the hydrogenation of H3CCCH. Computationally-derived activation barriers give additional insight into what types of reactions and mechanisms are more likely to occur in the laboratory and in the ISM. Our findings not only suggest that the alcohols studied here share common chemical pathways and therefore can show up simultaneously in astronomical surveys, but also that their extended counterparts that derive from polyynes containing H3C(CC)nH structures may exist in the ISM. Such larger species, like fatty alcohols, are the possible constituents of simple lipids that primitive cell membranes on the early Earth are thought to be partially composed of. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1905.05063v1-abstract-full').style.display = 'none'; document.getElementById('1905.05063v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 13 May, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Published in ACS Earth and Space Chemistry, Complex Organic Molecules (COMs) in Star-Forming Regions special issue</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1904.06112">arXiv:1904.06112</a> <span> [<a href="https://arxiv.org/pdf/1904.06112">pdf</a>, <a href="https://arxiv.org/format/1904.06112">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1021/acsearthspacechem.9b00029">10.1021/acsearthspacechem.9b00029 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Formation of Acetaldehyde on CO-rich Ices </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Lamberts%2C+T">Thanja Lamberts</a>, <a href="/search/?searchtype=author&query=Markmeyer%2C+M+N">Max N. Markmeyer</a>, <a href="/search/?searchtype=author&query=Kolb%2C+F+J">Florian J. Kolb</a>, <a href="/search/?searchtype=author&query=K%C3%A4stner%2C+J">Johannes K盲stner</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1904.06112v1-abstract-short" style="display: inline;"> The radicals HCO and CH$_3$ on carbon monoxide ice surfaces were simulated using density functional theory. Their binding energy on amorphous CO ice shows broad distributions, with approximative average values of 500 K for HCO and 200 K for CH$_3$. If they are located on the surface close to each other (3 to 4 脜), molecular dynamics calculations based on density functional theory show that they ca… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1904.06112v1-abstract-full').style.display = 'inline'; document.getElementById('1904.06112v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1904.06112v1-abstract-full" style="display: none;"> The radicals HCO and CH$_3$ on carbon monoxide ice surfaces were simulated using density functional theory. Their binding energy on amorphous CO ice shows broad distributions, with approximative average values of 500 K for HCO and 200 K for CH$_3$. If they are located on the surface close to each other (3 to 4 脜), molecular dynamics calculations based on density functional theory show that they can form acetaldehyde (CH$_3$CHO) or CH$_4$ + CO in barrier-less reactions, depending on the initial orientation of the molecules with respect to each other. In some orientations, no spontaneous reactions were found, the products remained bound to the surface. Sufficient configurational sampling, inclusion of the vibrational zero point energy, and a thorough benchmark of the applied electronic structure method are important to predict reliable binding energies for such weakly interacting systems. From these results it is clear that complex organic molecules, like acetaldehyde, can be formed by recombination reactions of radicals on CO surfaces. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1904.06112v1-abstract-full').style.display = 'none'; document.getElementById('1904.06112v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 12 April, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted in ACS Earth and Space Chemistry</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1810.04669">arXiv:1810.04669</a> <span> [<a href="https://arxiv.org/pdf/1810.04669">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/s41550-018-0380-9">10.1038/s41550-018-0380-9 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> An infrared measurement of chemical desorption from interstellar ice analogues </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Oba%2C+Y">Y. Oba</a>, <a href="/search/?searchtype=author&query=Tomaru%2C+T">T. Tomaru</a>, <a href="/search/?searchtype=author&query=Lamberts%2C+T">T. Lamberts</a>, <a href="/search/?searchtype=author&query=Kouchi%2C+A">A. Kouchi</a>, <a href="/search/?searchtype=author&query=Watanabe%2C+N">N. Watanabe</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1810.04669v1-abstract-short" style="display: inline;"> In molecular clouds at temperatures as low as 10 K, all species except hydrogen and helium should be locked in the heterogeneous ice on dust grain surfaces. Nevertheless, astronomical observations have detected over 150 different species in the gas phase in these clouds. The mechanism by which molecules are released from the dust surface below thermal desorption temperatures to be detectable in th… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1810.04669v1-abstract-full').style.display = 'inline'; document.getElementById('1810.04669v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1810.04669v1-abstract-full" style="display: none;"> In molecular clouds at temperatures as low as 10 K, all species except hydrogen and helium should be locked in the heterogeneous ice on dust grain surfaces. Nevertheless, astronomical observations have detected over 150 different species in the gas phase in these clouds. The mechanism by which molecules are released from the dust surface below thermal desorption temperatures to be detectable in the gas phase is crucial for understanding the chemical evolution in such cold clouds. Chemical desorption, caused by the excess energy of an exothermic reaction, was first proposed as a key molecular release mechanism almost 50 years ago. Chemical desorption can, in principle, take place at any temperature, even below the thermal desorption temperature. Therefore, astrochemical net- work models commonly include this process. Although there have been a few previous experimental efforts, no infrared measurement of the surface (which has a strong advantage to quantify chemical desorption) has been performed. Here, we report the first infrared in situ measurement of chemical desorption during the reactions H + H2S -> HS + H2 (reaction 1) and HS + H -> H2S (reaction 2), which are key to interstellar sulphur chemistry. The present study clearly demonstrates that chemical desorption is a more efficient process for releasing H2S into the gas phase than was previously believed. The obtained effective cross-section for chemical desorption indicates that the chemical desorption rate exceeds the photodesorption rate in typical interstellar environments. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1810.04669v1-abstract-full').style.display = 'none'; document.getElementById('1810.04669v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 10 October, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Oba et al. (2018) Nature Astronomy, 2, 228-232 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1806.05831">arXiv:1806.05831</a> <span> [<a href="https://arxiv.org/pdf/1806.05831">pdf</a>, <a href="https://arxiv.org/format/1806.05831">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/201833346">10.1051/0004-6361/201833346 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Tunnelling dominates the reactions of hydrogen atoms with unsaturated alcohols and aldehydes in the dense medium </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Zaverkin%2C+V">V. Zaverkin</a>, <a href="/search/?searchtype=author&query=Lamberts%2C+T">T. Lamberts</a>, <a href="/search/?searchtype=author&query=Markmeyer%2C+M+N">M. N. Markmeyer</a>, <a href="/search/?searchtype=author&query=K%C3%A4stner%2C+J">J. K盲stner</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1806.05831v1-abstract-short" style="display: inline;"> Hydrogen addition and abstraction reactions play an important role as surface reactions in the buildup of complex organic molecules in the dense interstellar medium. Addition reactions allow unsaturated bonds to be fully hydrogenated, while abstraction reactions recreate radicals that may undergo radical-radical recombination reactions. Previous experimental work has indicated that double and trip… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1806.05831v1-abstract-full').style.display = 'inline'; document.getElementById('1806.05831v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1806.05831v1-abstract-full" style="display: none;"> Hydrogen addition and abstraction reactions play an important role as surface reactions in the buildup of complex organic molecules in the dense interstellar medium. Addition reactions allow unsaturated bonds to be fully hydrogenated, while abstraction reactions recreate radicals that may undergo radical-radical recombination reactions. Previous experimental work has indicated that double and triple C--C bonds are easily hydrogenated, but aldehyde -C=O bonds are not. Here, we investigate a total of 29 reactions of the hydrogen atom with propynal, propargyl alcohol, propenal, allyl alcohol, and propanal by means of quantum chemical methods to quantify the reaction rate constants involved. First of all, our results are in good agreement with and can explain the observed experimental findings. The hydrogen addition to the aldehyde group, either on the C or O side, is indeed slow for all molecules considered. Abstraction of the H atom of the aldehyde group, on the other hand, is among the faster reactions. Furthermore, hydrogen addition to C--C double bonds is generally faster than to triple bonds. In both cases, addition on the terminal carbon atom that is not connected to other functional groups is easiest. Finally, we wish to stress that it is not possible to predict rate constants based solely on the type of reaction: the specific functional groups attached to a backbone play a crucial role and can lead to a spread of several orders of magnitude in the rate constant. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1806.05831v1-abstract-full').style.display = 'none'; document.getElementById('1806.05831v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 15 June, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in A&A</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1806.02990">arXiv:1806.02990</a> <span> [<a href="https://arxiv.org/pdf/1806.02990">pdf</a>, <a href="https://arxiv.org/format/1806.02990">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/201832830">10.1051/0004-6361/201832830 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> From interstellar carbon monosulfide to methyl mercaptan: paths of least resistance </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Lamberts%2C+T">T Lamberts</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1806.02990v1-abstract-short" style="display: inline;"> The 29 reactions linking carbon monosulfide (CS) to methyl mercaptan (CH3SH) via ten intermediate radicals and molecules have been characterized with relevance to surface chemistry in cold interstellar ices. More intermediate species than previously considered are found likely to be present in these ices, such as trans- and cis-HCSH. Both activation and reaction energies have been calculated, alon… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1806.02990v1-abstract-full').style.display = 'inline'; document.getElementById('1806.02990v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1806.02990v1-abstract-full" style="display: none;"> The 29 reactions linking carbon monosulfide (CS) to methyl mercaptan (CH3SH) via ten intermediate radicals and molecules have been characterized with relevance to surface chemistry in cold interstellar ices. More intermediate species than previously considered are found likely to be present in these ices, such as trans- and cis-HCSH. Both activation and reaction energies have been calculated, along with low-temperature (T > 45~K) rate constants for the radical-neutral reactions. For barrierless radical-radical reactions on the other hand, branching ratios have been determined. The combination of these two sets of information provides, for the first time, quantitative information on the full H + CS reaction network. Early on in this network, that is, early on in the lifetime of an interstellar cloud, HCS is the main radical, while later on this becomes first CH2SH and finally CH3S. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1806.02990v1-abstract-full').style.display = 'none'; document.getElementById('1806.02990v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 8 June, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in A&A Lett</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1806.02062">arXiv:1806.02062</a> <span> [<a href="https://arxiv.org/pdf/1806.02062">pdf</a>, <a href="https://arxiv.org/format/1806.02062">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1093/mnras/sty1478">10.1093/mnras/sty1478 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Hydrogen transfer reactions of interstellar Complex Organic Molecules </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=%C3%81lvarez-Barcia%2C+S">S. 脕lvarez-Barcia</a>, <a href="/search/?searchtype=author&query=Russ%2C+P">P. Russ</a>, <a href="/search/?searchtype=author&query=K%C3%A4stner%2C+J">J. K盲stner</a>, <a href="/search/?searchtype=author&query=Lamberts%2C+T">T. Lamberts</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1806.02062v1-abstract-short" style="display: inline;"> Radical recombination has been proposed to lead to the formation of complex organic molecules (COMs) in CO-rich ices in the early stages of star formation. These COMs can then undergo hydrogen addition and abstraction reactions leading to a higher or lower degree of saturation. Here, we have studied 14 hydrogen transfer reactions for the molecules glyoxal, glycoaldehyde, ethylene glycol, and methy… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1806.02062v1-abstract-full').style.display = 'inline'; document.getElementById('1806.02062v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1806.02062v1-abstract-full" style="display: none;"> Radical recombination has been proposed to lead to the formation of complex organic molecules (COMs) in CO-rich ices in the early stages of star formation. These COMs can then undergo hydrogen addition and abstraction reactions leading to a higher or lower degree of saturation. Here, we have studied 14 hydrogen transfer reactions for the molecules glyoxal, glycoaldehyde, ethylene glycol, and methylformate and an additional three reactions where \ce{CH_nO} fragments are involved. Over-the-barrier reactions are possible only if tunneling is invoked in the description at low temperature. Therefore the rate constants for the studied reactions are calculated using instanton theory that takes quantum effects into account inherently. The reactions were characterized in the gas phase, but this is expected to yield meaningful results for CO-rich ices due to the minimal alteration of reaction landscapes by the CO molecules. We found that rate constants should not be extrapolated based on the height of the barrier alone, since the shape of the barrier plays an increasingly larger role at decreasing temperature. It is neither possible to predict rate constants based only on considering the type of reaction, the specific reactants and functional groups play a crucial role. Within a single molecule, though, hydrogen abstraction from an aldehyde group seems to be always faster than hydrogen addition to the same carbon atom. Reactions that involve heavy-atom tunneling, e.g., breaking or forming a C--C or C--O bond, have rate constants that are much lower than those where H transfer is involved. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1806.02062v1-abstract-full').style.display = 'none'; document.getElementById('1806.02062v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 6 June, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in MNRAS</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1712.02088">arXiv:1712.02088</a> <span> [<a href="https://arxiv.org/pdf/1712.02088">pdf</a>, <a href="https://arxiv.org/format/1712.02088">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1021/acs.jpca.7b10296">10.1021/acs.jpca.7b10296 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Tunneling Reaction Kinetics for the Hydrogen Abstraction Reaction H + H$_2$S -> H$_2$ + HS in the Interstellar Medium </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Lamberts%2C+T">Thanja Lamberts</a>, <a href="/search/?searchtype=author&query=K%C3%A4stner%2C+J">Johannes K盲stner</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1712.02088v1-abstract-short" style="display: inline;"> The hydrogen abstraction reaction between H and H$_2$S, yielding HS and H$_2$ as products, has been studied within the framework of interstellar surface chemistry. High-temperature rate constants up to 2000 K are calculated in the gas phase and are in agreement with previously reported values. Subsequently low-temperature rate constants down to 55 K are presented for the first time that are of int… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1712.02088v1-abstract-full').style.display = 'inline'; document.getElementById('1712.02088v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1712.02088v1-abstract-full" style="display: none;"> The hydrogen abstraction reaction between H and H$_2$S, yielding HS and H$_2$ as products, has been studied within the framework of interstellar surface chemistry. High-temperature rate constants up to 2000 K are calculated in the gas phase and are in agreement with previously reported values. Subsequently low-temperature rate constants down to 55 K are presented for the first time that are of interest to astrochemistry, i.e., covering both bimolecular and unimolecular reaction mechanisms. For this, a so-called implicit surface model is used. Strictly speaking, this is a structural gas-phase model in which the restriction of the rotation in the solid state is taken into account. The calculated kinetic isotope effects are explained in terms of difference in activation and delocalization. All rate constants are calculated at the UCCSD(T)-F12/cc-VTZ-F12 level of theory. Finally, we show that the energetics of the reaction is only affected to a small extent by the presence of H$_2$O or H$_2$S molecular clusters that simulate an ice surface, calculated at the MPWB1K/def2-TZVP level of theory. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1712.02088v1-abstract-full').style.display = 'none'; document.getElementById('1712.02088v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 6 December, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2017. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in Journal of Physical Chemistry A http://pubs.acs.org/doi/pdfplus/10.1021/acs.jpca.7b10296</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1708.05559">arXiv:1708.05559</a> <span> [<a href="https://arxiv.org/pdf/1708.05559">pdf</a>, <a href="https://arxiv.org/format/1708.05559">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1021/acsearthspacechem.7b00052">10.1021/acsearthspacechem.7b00052 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Atom Tunneling in the Water Formation Reaction H$_2$ + OH $\rightarrow$ H$_2$O + H on an Ice Surface </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Meisner%2C+J">Jan Meisner</a>, <a href="/search/?searchtype=author&query=Lamberts%2C+T">Thanja Lamberts</a>, <a href="/search/?searchtype=author&query=K%C3%A4stner%2C+J">Johannes K盲stner</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1708.05559v1-abstract-short" style="display: inline;"> OH radicals play a key role as an intermediate in the water formation chemistry of the interstellar medium. For example the reaction of OH radicals with H$_2$ molecules is among the final steps in the astrochemical reaction network starting from O, O$_2$, and O$_3$. Experimentally it was shown that even at 10 K this reaction occurs on ice surfaces. As the reaction has a high activation energy only… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1708.05559v1-abstract-full').style.display = 'inline'; document.getElementById('1708.05559v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1708.05559v1-abstract-full" style="display: none;"> OH radicals play a key role as an intermediate in the water formation chemistry of the interstellar medium. For example the reaction of OH radicals with H$_2$ molecules is among the final steps in the astrochemical reaction network starting from O, O$_2$, and O$_3$. Experimentally it was shown that even at 10 K this reaction occurs on ice surfaces. As the reaction has a high activation energy only atom tunneling can explain such experimental findings. In this study we calculated reaction rate constants for the title reaction on a water-ice I$_h$ surface. To our knowledge, low-temperature rate constants on a surface are not available in the literature. All surface calculations were done using a QM/MM framework (BHLYP/TIP3P) after a thorough benchmark of different density functionals and basis sets to highly accurate correlation methods. Reaction rate constants are obtained using instanton theory which takes atom tunneling into account inherently, with constants down to 110 K for the Eley-Rideal mechanism and down to 60 K for the Langmuir-Hinshelwood mechanism. We found that the reaction is nearly temperature independent below 80 K. We give kinetic isotope effects for all possible deuteration patterns for both reaction mechanisms. For the implementation in astrochemical networks, we also give fit parameters to a modified Arrhenius equation. Finally, several different binding sites and binding energies of OH radicals on the I$_h$ surface are discussed and the corresponding rate constants are compared to the gas-phase case. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1708.05559v1-abstract-full').style.display = 'none'; document.getElementById('1708.05559v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 18 August, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2017. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Published online. Supporting information on http://pubs.acs.org/doi/suppl/10.1021/acsearthspacechem.7b00052</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1708.05555">arXiv:1708.05555</a> <span> [<a href="https://arxiv.org/pdf/1708.05555">pdf</a>, <a href="https://arxiv.org/format/1708.05555">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/aa8311">10.3847/1538-4357/aa8311 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Influence of surface and bulk water ice on the reactivity of a water-forming reaction </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Lamberts%2C+T">Thanja Lamberts</a>, <a href="/search/?searchtype=author&query=K%C3%A4stner%2C+J">Johannes K盲stner</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1708.05555v1-abstract-short" style="display: inline;"> On the surface of icy dust grains in the dense regions of the interstellar medium a rich chemistry can take place. Due to the low temperature, reactions that proceed via a barrier can only take place through tunneling. The reaction H + H$_2$O$_2$ $\rightarrow$ H$_2$O + OH is such a case with a gas-phase barrier of $\sim$26.5 kJ/mol. Still the reaction is known to be involved in water formation on… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1708.05555v1-abstract-full').style.display = 'inline'; document.getElementById('1708.05555v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1708.05555v1-abstract-full" style="display: none;"> On the surface of icy dust grains in the dense regions of the interstellar medium a rich chemistry can take place. Due to the low temperature, reactions that proceed via a barrier can only take place through tunneling. The reaction H + H$_2$O$_2$ $\rightarrow$ H$_2$O + OH is such a case with a gas-phase barrier of $\sim$26.5 kJ/mol. Still the reaction is known to be involved in water formation on interstellar grains. Here, we investigate the influence of a water ice surface and of bulk ice on the reaction rate constant. Rate constants are calculated using instanton theory down to 74 K. The ice is taken into account via multiscale modeling, describing the reactants and the direct surrounding at the quantum mechanical level with density functional theory (DFT), while the rest of the ice is modeled on the molecular mechanical level with a force field. We find that H$_2$O$_2$ binding energies cannot be captured by a single value, but rather depend on the number of hydrogen bonds with surface molecules. In highly amorphous surroundings the binding site can block the routes of attack and impede the reaction. Furthermore, the activation energies do not correlate with the binding energies of the same sites. The unimolecular rate constants related to the Langmuir-Hinshelwood mechanism increase as the activation energy decreases. Thus, we provide a lower limit for the rate constant and argue that rate constants can have values up to two order of magnitude larger than this limit. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1708.05555v1-abstract-full').style.display = 'none'; document.getElementById('1708.05555v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 18 August, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2017. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1705.09235">arXiv:1705.09235</a> <span> [<a href="https://arxiv.org/pdf/1705.09235">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1093/mnras/stu2603">10.1093/mnras/stu2603 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Experimental evidence for Glycolaldehyde and Ethylene Glycol formation by surface hydrogenation of CO molecules under dense molecular cloud conditions </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Fedoseev%2C+G">Gleb Fedoseev</a>, <a href="/search/?searchtype=author&query=Cuppen%2C+H+M">Herma M. Cuppen</a>, <a href="/search/?searchtype=author&query=Ioppolo%2C+S">Sergio Ioppolo</a>, <a href="/search/?searchtype=author&query=Lamberts%2C+T">Thanja Lamberts</a>, <a href="/search/?searchtype=author&query=Linnartz%2C+H">Harold Linnartz</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1705.09235v1-abstract-short" style="display: inline;"> This study focuses on the formation of two molecules of astrobiological importance - glycolaldehyde (HC(O)CH2OH) and ethylene glycol (H2C(OH)CH2OH) - by surface hydrogenation of CO molecules. Our experiments aim at simulating the CO freeze-out stage in interstellar dark cloud regions, well before thermal and energetic processing become dominant. It is shown that along with the formation of H2CO an… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1705.09235v1-abstract-full').style.display = 'inline'; document.getElementById('1705.09235v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1705.09235v1-abstract-full" style="display: none;"> This study focuses on the formation of two molecules of astrobiological importance - glycolaldehyde (HC(O)CH2OH) and ethylene glycol (H2C(OH)CH2OH) - by surface hydrogenation of CO molecules. Our experiments aim at simulating the CO freeze-out stage in interstellar dark cloud regions, well before thermal and energetic processing become dominant. It is shown that along with the formation of H2CO and CH3OH - two well established products of CO hydrogenation - also molecules with more than one carbon atom form. The key step in this process is believed to be the recombination of two HCO radicals followed by the formation of a C-C bond. The experimentally established reaction pathways are implemented into a continuous-time random-walk Monte Carlo model, previously used to model the formation of CH3OH on astrochemical time-scales, to study their impact on the solid-state abundances in dense interstellar clouds of glycolaldehyde and ethylene glycol. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1705.09235v1-abstract-full').style.display = 'none'; document.getElementById('1705.09235v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 25 May, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2017. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Monthly Notices of the Royal Astronomical Society, Volume 448, Issue 2, p.1288-1297 (2015) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1705.09184">arXiv:1705.09184</a> <span> [<a href="https://arxiv.org/pdf/1705.09184">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1093/mnras/stu2028">10.1093/mnras/stu2028 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Low Temperature Surface Formation of NH3 and HNCO: hydrogenation of nitrogen atoms in CO-rich interstellar ice analogues </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Fedoseev%2C+G">Gleb Fedoseev</a>, <a href="/search/?searchtype=author&query=Ioppolo%2C+S">Sergio Ioppolo</a>, <a href="/search/?searchtype=author&query=Zhao%2C+D">Dongfeng Zhao</a>, <a href="/search/?searchtype=author&query=Lamberts%2C+T">Thanja Lamberts</a>, <a href="/search/?searchtype=author&query=Linnartz%2C+H">Harold Linnartz</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1705.09184v1-abstract-short" style="display: inline;"> Solid state astrochemical reaction pathways have the potential to link the formation of small nitrogen-bearing species, like NH3 and HNCO, and prebiotic molecules, specifically amino acids. To date, the chemical origin of such small nitrogen containing species is still not well understood, despite the fact that ammonia is an abundant constituent of interstellar ices toward young stellar objects an… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1705.09184v1-abstract-full').style.display = 'inline'; document.getElementById('1705.09184v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1705.09184v1-abstract-full" style="display: none;"> Solid state astrochemical reaction pathways have the potential to link the formation of small nitrogen-bearing species, like NH3 and HNCO, and prebiotic molecules, specifically amino acids. To date, the chemical origin of such small nitrogen containing species is still not well understood, despite the fact that ammonia is an abundant constituent of interstellar ices toward young stellar objects and quiescent molecular clouds. This is mainly because of the lack of dedicated laboratory studies. The aim of the present work is to experimentally investigate the formation routes of NH3 and HNCO through non-energetic surface reactions in interstellar ice analogues under fully controlled laboratory conditions and at astrochemically relevant temperatures. This study focuses on the formation of NH3 and HNCO in CO-rich (non-polar) interstellar ices that simulate the CO freeze-out stage in dark interstellar cloud regions, well before thermal and energetic processing start to become relevant. We demonstrate and discuss the surface formation of solid HNCO through the interaction of CO molecules with NH radicals - one of the intermediates in the formation of solid NH3 upon sequential hydrogenation of N atoms. The importance of HNCO for astrobiology is discussed. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1705.09184v1-abstract-full').style.display = 'none'; document.getElementById('1705.09184v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 25 May, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2017. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Monthly Notices of the Royal Astronomical Society, Volume 446, Issue 1, p.439-448 (2015) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1705.09175">arXiv:1705.09175</a> <span> [<a href="https://arxiv.org/pdf/1705.09175">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1063/1.4738893">10.1063/1.4738893 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Efficient Surface Formation Route of Interstellar Hydroxylamine through NO Hydrogenation II: the multilayer regime in interstellar relevant ices </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Fedoseev%2C+G">Gleb Fedoseev</a>, <a href="/search/?searchtype=author&query=Ioppolo%2C+S">Sergio Ioppolo</a>, <a href="/search/?searchtype=author&query=Lamberts%2C+T">Thanja Lamberts</a>, <a href="/search/?searchtype=author&query=Zhen%2C+J">Junfeng Zhen</a>, <a href="/search/?searchtype=author&query=Cuppen%2C+H+M">Herma M. Cuppen</a>, <a href="/search/?searchtype=author&query=Linnartz%2C+H">Harold Linnartz</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1705.09175v1-abstract-short" style="display: inline;"> Hydroxylamine (NH2OH) is one of the potential precursors of complex pre-biotic species in space. Here we present a detailed experimental study of hydroxylamine formation through nitric oxide (NO) surface hydrogenation for astronomically relevant conditions. The aim of this work is to investigate hydroxylamine formation efficiencies in polar (water-rich) and non-polar (carbon monoxide-rich) interst… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1705.09175v1-abstract-full').style.display = 'inline'; document.getElementById('1705.09175v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1705.09175v1-abstract-full" style="display: none;"> Hydroxylamine (NH2OH) is one of the potential precursors of complex pre-biotic species in space. Here we present a detailed experimental study of hydroxylamine formation through nitric oxide (NO) surface hydrogenation for astronomically relevant conditions. The aim of this work is to investigate hydroxylamine formation efficiencies in polar (water-rich) and non-polar (carbon monoxide-rich) interstellar ice analogues. A complex reaction network involving both final (N2O, NH2OH) and intermediate (HNO, NH2O, etc.) products is discussed. The main conclusion is that hydroxylamine formation takes place via a fast and barrierless mechanism and it is found to be even more abundantly formed in a water-rich environment at lower temperatures. In parallel, we experimentally verify the non-formation of hydroxylamine upon UV photolysis of NO ice at cryogenic temperatures as well as the non-detection of NC- and NCO-bond bearing species after UV processing of NO in carbon monoxide-rich ices. Our results are implemented into an astrochemical reaction model, which shows that NH2OH is abundant in the solid phase under dark molecular cloud conditions. Once NH2OH desorbs from the ice grains, it becomes available to form more complex species (e.g., glycine and beta-alanine) in gas phase reaction schemes. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1705.09175v1-abstract-full').style.display = 'none'; document.getElementById('1705.09175v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 25 May, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2017. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Journal of Chemical Physics, Volume 137, Issue 5, page 054714 (2012) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1612.07027">arXiv:1612.07027</a> <span> [<a href="https://arxiv.org/pdf/1612.07027">pdf</a>, <a href="https://arxiv.org/format/1612.07027">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/201629845">10.1051/0004-6361/201629845 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Importance of tunneling in H-abstraction reactions by OH radicals: The case of CH4 + OH studied through isotope-substituted analogs </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Lamberts%2C+T">Thanja Lamberts</a>, <a href="/search/?searchtype=author&query=Fedoseev%2C+G">Gleb Fedoseev</a>, <a href="/search/?searchtype=author&query=K%C3%A4stner%2C+J">Johannes K盲stner</a>, <a href="/search/?searchtype=author&query=Ioppolo%2C+S">Sergio Ioppolo</a>, <a href="/search/?searchtype=author&query=Linnartz%2C+H">Harold Linnartz</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1612.07027v1-abstract-short" style="display: inline;"> We present a combined experimental and theoretical study focussing on the quantum tunneling of atoms in the reaction between CH4 and OH. The importance of this reaction pathway is derived by investigating isotope substituted analogs. Quantitative reaction rates needed for astrochemical models at low temperature are currently unavailable both in the solid state and in the gas phase. Here, we study… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1612.07027v1-abstract-full').style.display = 'inline'; document.getElementById('1612.07027v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1612.07027v1-abstract-full" style="display: none;"> We present a combined experimental and theoretical study focussing on the quantum tunneling of atoms in the reaction between CH4 and OH. The importance of this reaction pathway is derived by investigating isotope substituted analogs. Quantitative reaction rates needed for astrochemical models at low temperature are currently unavailable both in the solid state and in the gas phase. Here, we study tunneling effects upon hydrogen abstraction in CH4 + OH by focusing on two reactions: CH4 + OD -> CH3 + HDO and CD4 + OH -> CD3 + HDO. The experimental study shows that the solid-state reaction rate R(CH4 + OD) is higher than R(CD4 + OH) at 15 K. Experimental results are accompanied by calculations of the corresponding unimolecular and bimolecular reaction rate constants using instanton theory taking into account surface effects. From the work presented here, the unimolecular reactions are particularly interesting as these provide insight into reactions following a Langmuir-Hinshelwood process. The resulting ratio of the rate constants shows that the H abstraction (k(CH4 + OD)) is approximately ten times faster than D-abstraction (k(CD4 + OH)) at 65 K. We conclude that tunneling is involved at low temperatures in the abstraction reactions studied here. The unimolecular rate constants can be used by the modeling community as a first approach to describe OH-mediated abstraction reactions in the solid phase. For this reason we provide fits of our calculated rate constants that allow the inclusion of these reactions in models in a straightforward fashion. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1612.07027v1-abstract-full').style.display = 'none'; document.getElementById('1612.07027v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 21 December, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2016. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted by A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 599, A132 (2017) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1611.09188">arXiv:1611.09188</a> <span> [<a href="https://arxiv.org/pdf/1611.09188">pdf</a>, <a href="https://arxiv.org/format/1611.09188">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1039/C6CP06457D">10.1039/C6CP06457D <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Quantum tunneling during interstellar surface-catalyzed formation of water: the reaction H + H$_2$O$_2$ $\rightarrow$ H$_2$O + OH </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Lamberts%2C+T">Thanja Lamberts</a>, <a href="/search/?searchtype=author&query=Samanta%2C+P+K">Pradipta Kumar Samanta</a>, <a href="/search/?searchtype=author&query=K%C3%B6hn%2C+A">Andreas K枚hn</a>, <a href="/search/?searchtype=author&query=K%C3%A4stner%2C+J">Johannes K盲stner</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1611.09188v1-abstract-short" style="display: inline;"> The final step of the water formation network on interstellar grain surfaces starting from the H + O$_2$ route is the reaction between H and H$_2$O$_2$. This reaction is known to have a high activation energy and therefore at low temperatures it can only proceed via tunneling. To date, however, no rate constants are available at temperatures below 200 K. In this work, we use instanton theory to co… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1611.09188v1-abstract-full').style.display = 'inline'; document.getElementById('1611.09188v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1611.09188v1-abstract-full" style="display: none;"> The final step of the water formation network on interstellar grain surfaces starting from the H + O$_2$ route is the reaction between H and H$_2$O$_2$. This reaction is known to have a high activation energy and therefore at low temperatures it can only proceed via tunneling. To date, however, no rate constants are available at temperatures below 200 K. In this work, we use instanton theory to compute rate constants for the title reaction with and without isotopic substitutions down to temperatures of 50 K. The calculations are based on density functional theory, with additional benchmarks for the activation energy using unrestricted single-reference and multireference coupled-cluster single-point energies. Gas-phase bimolecular rate constants are calculated and compared with available experimental data not only for H + H$_2$O$_2$ $\rightarrow$ H$_2$O + OH, but also for H + H$_2$O$_2$ $\rightarrow$ H$_2$ + HO$_2$. We find a branching ratio where the title reaction is favored by at least two orders of magnitude at 114 K. In the interstellar medium this reaction predominantly occurs on water surfaces, which increases the probability that the two reactants meet. To mimic this one, two, or three spectator H2O molecules are added to the system. Eley-Rideal bimolecular and Langmuir-Hinshelwood unimolecular rate constants are presented here. The kinetic isotope effects for the various cases are compared to experimental data as well as to expressions commonly used in astrochemical models. Both the rectangular barrier and the Eckart approximations lead to errors of about an order of magnitude. Finally, fits of the rate constants are provided as input for astrochemical models. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1611.09188v1-abstract-full').style.display = 'none'; document.getElementById('1611.09188v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 28 November, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2016. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication by Phys. Chem. Chem. Phys. 2016. Supplementary information available: http://www.rsc.org/suppdata/c6/cp/c6cp06457d/c6cp06457d1.pdf</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1511.02010">arXiv:1511.02010</a> <span> [<a href="https://arxiv.org/pdf/1511.02010">pdf</a>, <a href="https://arxiv.org/format/1511.02010">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Earth and Planetary Astrophysics">astro-ph.EP</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1093/mnras/stv2305">10.1093/mnras/stv2305 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Low-temperature chemistry between water and hydroxyl radicals: H/D isotopic effects </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Lamberts%2C+T">T. Lamberts</a>, <a href="/search/?searchtype=author&query=Fedoseev%2C+G">G. Fedoseev</a>, <a href="/search/?searchtype=author&query=Puletti%2C+F">F. Puletti</a>, <a href="/search/?searchtype=author&query=Ioppolo%2C+S">S. Ioppolo</a>, <a href="/search/?searchtype=author&query=Cuppen%2C+H+M">H. M. Cuppen</a>, <a href="/search/?searchtype=author&query=Linnartz%2C+H">H. Linnartz</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1511.02010v1-abstract-short" style="display: inline;"> Sets of systematic laboratory experiments are presented -- combining Ultra High Vacuum cryogenic and plasma-line deposition techniques -- that allow us to compare H/D isotopic effects in the reaction of H2O (D2O) ice with the hydroxyl radical OD (OH). The latter is known to play a key role as intermediate species in the solid-state formation of water on icy grains in space. The main finding of our… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1511.02010v1-abstract-full').style.display = 'inline'; document.getElementById('1511.02010v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1511.02010v1-abstract-full" style="display: none;"> Sets of systematic laboratory experiments are presented -- combining Ultra High Vacuum cryogenic and plasma-line deposition techniques -- that allow us to compare H/D isotopic effects in the reaction of H2O (D2O) ice with the hydroxyl radical OD (OH). The latter is known to play a key role as intermediate species in the solid-state formation of water on icy grains in space. The main finding of our work is that the reaction H2O + OD --> OH + HDO occurs and that this may affect the HDO/H2O abundances in space. The opposite reaction D2O + OH --> OD + HDO is much less effective, and also given the lower D2O abundances in space not expected to be of astronomical relevance. The experimental results are extended to the other four possible reactions between hydroxyl and water isotopes and are subsequently used as input for Kinetic Monte Carlo simulations. This way we interpret our findings in an astronomical context, qualitatively testing the influence of the reaction rates. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1511.02010v1-abstract-full').style.display = 'none'; document.getElementById('1511.02010v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 6 November, 2015; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2015. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in MNRAS</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> MNRAS (January 01, 2016) 455 (1): 634-641 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1502.03584">arXiv:1502.03584</a> <span> [<a href="https://arxiv.org/pdf/1502.03584">pdf</a>, <a href="https://arxiv.org/format/1502.03584">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1093/mnras/stv278">10.1093/mnras/stv278 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Thermal H/D exchange in polar ice - deuteron scrambling in space </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Lamberts%2C+T">Thanja Lamberts</a>, <a href="/search/?searchtype=author&query=Ioppolo%2C+S">Sergio Ioppolo</a>, <a href="/search/?searchtype=author&query=Cuppen%2C+H">Herma Cuppen</a>, <a href="/search/?searchtype=author&query=Fedoseev%2C+G">Gleb Fedoseev</a>, <a href="/search/?searchtype=author&query=Linnartz%2C+H">Harold Linnartz</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1502.03584v1-abstract-short" style="display: inline;"> We have investigated the thermally induced proton/deuteron exchange in mixed amorphous H$_2$O:D$_2$O ices by monitoring the change in intensity of characteristic vibrational bending modes of H$_2$O, HDO, and D$_2$O with time and as function of temperature. The experiments have been performed using an ultra-high vacuum setup equipped with an infrared spectrometer that is used to investigate the spe… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1502.03584v1-abstract-full').style.display = 'inline'; document.getElementById('1502.03584v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1502.03584v1-abstract-full" style="display: none;"> We have investigated the thermally induced proton/deuteron exchange in mixed amorphous H$_2$O:D$_2$O ices by monitoring the change in intensity of characteristic vibrational bending modes of H$_2$O, HDO, and D$_2$O with time and as function of temperature. The experiments have been performed using an ultra-high vacuum setup equipped with an infrared spectrometer that is used to investigate the spectral evolution of homogeneously mixed ice upon co-deposition in thin films, for temperatures in the 90 to 140 K domain. With this non-energetic detection method we find a significantly lower activation energy for H/D exchange -- $3840 \pm 125$ K -- than previously reported. Very likely this is due to the amorphous nature of the interstellar ice analogues involved. This provides reactive timescales ($蟿<10^4$ years at $T$ $>70$ K) fast enough for the process to be important in interstellar environments. Consequently, an astronomical detection of D$_2$O will be even more challenging because of its potential to react with H$_2$O to form HDO. Furthermore, additional experiments, along with previous studies, show that proton/deuteron swapping also occurs in ice mixtures of water with other hydrogen bonded molecules, in particular on the OH and NH moieties. We conclude that H/D exchange in ices is a more general process that should be incorporated into ice models that are applied to protoplanetary disks or to simulate the warming up of cometary ices in their passage of the perihelion, to examine the extent of its influence on the final deuteron over hydrogen ratio. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1502.03584v1-abstract-full').style.display = 'none'; document.getElementById('1502.03584v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 12 February, 2015; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2015. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">10 pages, 8 figures, accepted for publication in MNRAS</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1409.3055">arXiv:1409.3055</a> <span> [<a href="https://arxiv.org/pdf/1409.3055">pdf</a>, <a href="https://arxiv.org/format/1409.3055">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Earth and Planetary Astrophysics">astro-ph.EP</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Chemical Physics">physics.chem-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/201424252">10.1051/0004-6361/201424252 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> On the relevance of the H2 + O reaction pathway for the surface formation of interstellar water - A combined experimental and modeling study </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Lamberts%2C+T">Thanja Lamberts</a>, <a href="/search/?searchtype=author&query=Cuppen%2C+H">Herma Cuppen</a>, <a href="/search/?searchtype=author&query=Fedoseev%2C+G">Gleb Fedoseev</a>, <a href="/search/?searchtype=author&query=Ioppolo%2C+S">Sergio Ioppolo</a>, <a href="/search/?searchtype=author&query=Chuang%2C+K">Ko-Ju Chuang</a>, <a href="/search/?searchtype=author&query=Linnartz%2C+H">Harold Linnartz</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1409.3055v1-abstract-short" style="display: inline;"> The formation of interstellar water has been commonly accepted to occur on the surfaces of icy dust grains in dark molecular clouds at low temperatures (10-20 K), involving hydrogenation reactions of oxygen allotropes. As a result of the large abundances of molecular hydrogen and atomic oxygen in these regions, the reaction H2 + O has been proposed to contribute significantly to the formation of w… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1409.3055v1-abstract-full').style.display = 'inline'; document.getElementById('1409.3055v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1409.3055v1-abstract-full" style="display: none;"> The formation of interstellar water has been commonly accepted to occur on the surfaces of icy dust grains in dark molecular clouds at low temperatures (10-20 K), involving hydrogenation reactions of oxygen allotropes. As a result of the large abundances of molecular hydrogen and atomic oxygen in these regions, the reaction H2 + O has been proposed to contribute significantly to the formation of water as well. However, gas phase experiments and calculations, as well as solid-phase experimental work contradict this hypothesis. Here, we use precisely executed temperature programmed desorption (TPD) experiments in an ultra-high vacuum setup combined with kinetic Monte Carlo simulations to establish an upper limit of the water production starting from H2 and O. These reactants are brought together in a matrix of CO2 in a series of (control) experiments at different temperatures and with different isotopological compositions. The amount of water detected with the quadrupole mass spectrometer upon TPD is found to originate mainly from contamination in the chamber itself. However, if water is produced in small quantities on the surface through H2 + O, this can only be explained by a combined classical and tunneled reaction mechanism. An absolutely conservative upper limit for the reaction rate is derived with a microscopic kinetic Monte Carlo model that converts the upper limit into a maximal possible reaction rate. Incorporating this rate into simulations run for astrochemically relevant parameters, shows that the upper limit to the contribution of the reaction H2 + O in OH, and hence water formation, is 11% in dense interstellar clouds. Our combined experimental and theoretical results indicate however, that this contribution is likely to be much lower. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1409.3055v1-abstract-full').style.display = 'none'; document.getElementById('1409.3055v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 10 September, 2014; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2014. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">9 pages, 4 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 570, A57 (2014) </p> </li> </ol> <div class="is-hidden-tablet">  <span class="help" style="display: inline-block;"><a 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