Astrochemistry at high resolution Faraday Discussion

Astrochemistry at high resolution Faraday Discussion 31 May - 2 June 2023, Maryland, United States

31 May - 2 June 2023, Maryland, United States Astrochemistry at high resolution Faraday Discussion #FDAstrochem

Book of abstracts

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Introduction

Astrochemistry at high resolution Faraday Discussion is organised by the Faraday Division of the Royal Society of Chemistry This book contains abstracts of the posters presented at Astrochemistry at high resolution Faraday Discussion . All abstracts are produced directly from typescripts supplied by authors. Copyright reserved. Oral presentations and discussions All delegates at the meeting, not just speakers, have the opportunity to make comments, ask questions, or present complementary or contradictory measurements and calculations during the discussion. If it is relevant to the topic, you may give a 5-minute presentation of your own work during the discussion. These remarks are published alongside the papers in the final volume and are fully citable. If you would like to present slides during the discussion, please let the session chair know and load them onto the computer in the break before the start of the session. Faraday Discussion volume Copies of the discussion volume will be distributed approximately 6 months after the meeting. To expedite this, it is essential that summaries of contributions to the discussion are received no later than Friday 9 June 2023 for questions and comments and Friday 30 June 2023 for responses. Posters A poster session for the online posters will take place on Wednesday 31 May at 18:00 EST. The online posters will be available to view throughout the discussion by clicking on the link in the virtual lobby. During the dedicated poster session, online authors will be available to use the networking functions in the virtual lobby. Use the inbox in the top light blue bar of the virtual lobby screen to send the poster presenter a message or request a video call with them by clicking on their name in the networking section at the bottom of the screen. A poster session for the in-person posters will take place on Wednesday 31 May at 18:00 EST. The posters will be available to view throughout the discussion during all refreshment breaks. During the dedicated poster session, authors should stand with their poster to discuss their research with other attendees. Poster prize The Faraday Discussions poster prize will be awarded to the best student poster as judged by the committee. Networking sessions There will be regular breaks throughout the meeting for socialising, networking and continuing discussions started during the scientific sessions. During the networking sessions, all delegates will have access to join online networking rooms and can set theses up from the virtual lobby.

Scientific Committee

Invited Speakers

Martin R. S. McCoustra (Chair) Heriot-Watt University, UK Paola Caselli MPI for Extra-terrestrial Physics, Germany Anthony J. H. M. Meijer University of Sheffield, UK Neill Reid Space Telescope Science Institute, USA Ian R. Sims University of Rennes, France

Cecilia Ceccarelli (Introductory lecture) IPAG, Université Grenoble Alpes, France

Tom Millar (Closing remarks lecture) Queen’s University Belfast, UK

Wendy Brown University of Sussex, UK

Sandra Brünken Radboud University and FELIX, Netherlands

Robin Garrod University of Virginia, USA

Nick Walker University of Newcastle, UK

Murthy Gudipati NASA JPL, USA

Susanna Widicus Weaver University of Wisconsin-Madison, USA

Nikku Madhusudhan University of Cambridge, UK

Arthur Suits University of Missouri, Columbia, USA Ewine van Dishoeck Leiden Observatory, Netherlands Serena Viti Leiden Observatory, Netherlands

Faraday Discussions Forum

www.rscweb.org/forums/fd/login.php In order to record the discussion at the meeting, which forms part of the final published volume, your name and e-mail address will be stored in the Faraday Forum. This information is used for the collection of questions and responses communicated during each session. After each question or comment you will receive an e-mail which contains some keywords to remind you what you asked, and your password information for the forum. The e-mail is not a full record of your question. You need to complete your question in full on the forum. The deadline for completing questions and comments is Friday 9 June.

The question number in the e-mail keeps you a space on the forum. Use the forum to complete, review and expand on your question or comment. Figures and attachments can be uploaded to the forum. If you want to ask a question after the meeting, please e-mail faraday@rsc.org . Once we have received all questions and comments, responses will be invited by e-mail . These must also be completed on the forum . The deadline for completing responses is Friday 23 June . Please note that when using the Forum to submit a question or reply, your name and registered e-mail address will be visible to other delegates registered for this Faraday Discussions meeting. Key points: • The e-mail is not a full record of your comment/question. • All comments and responses must be completed in full on the forum Deadlines: Questions and comments Friday 9 June Responses Friday 23 June

Poster presentations

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The role of low-energy (< 20 eV) electrons in astrochemistry Kennedy Barnes Wellesley College, USA Chemical complexity and the role of condensed film structure: methane adsorption and propene oxidation Michelle Brann National Institute of Standards and Technology (NIST), USA Molecular mapping of comet 46P/Wirtanen using ALMA: parent vs. daughter sources in the coma Martin Cordiner NASA Goddard Space Flight Center, USA Discovery of an elevated 15N/14N ratio in the Jupiter-family comet 46P/ Wirtanen using ALMA Kristen Darnell NASA GSFC, USA

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Non-linear astrochemical kinetics: theory and application Gwenaelle Dufour NASA GSFC/CUA, USA

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High resolution anharmonic infrared absorption spectra of polycyclic aromatic hydrocarbons Vincent Esposito NASA Ames Research Center, USA Cyclopropenylidene chemistry in the interstellar medium Athena Flint University of Mississippi, USA The effects of small alcohols on the crystallisation behaviour of amorphous solid water Jack Fulker University of Sussex, UK Enhanced star formation through the high-temperature formation of H2 on carbonaceous dust grains Francesco Grieco University Ghent, Italy

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Determination of product abundances using broadband rotational spectroscopy of buffer gas cooled molecules desorbed from electron irradiated acetonitrile ices Travis Hager University of Missouri, USA Quantification of methanol photolysis branching ratios using multiplexed photoionization mass spectrometry Emily Hockey University of Maryland, USA Photodissociation and photoionization of molecules of astronomical interest: updates to the Leiden photodissociation & photoionization cross section database Helgi Hrodmarsson LISA laboratory (Université Paris-Est Créteil), France Laboratory measurements of N2 reacting with H3+ isotopologues Dmitry Ivanov Columbia University, USA A computational study of CO2 formation on interstellar H2O ice Harjasnoor Kakkar Universitat Autònoma de Barcelona, Spain Mono-deuterated methanol – a tool to assess the degree of thermal processing of interstellar ices? Beatrice Kulterer Center for Space and Habitability, Switzerland High-resolution SOFIA/EXES spectroscopy of water absorption lines in the massive young binary W3 IRS5 Jialu Li University of Maryland College Park, USA

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Ice origins of OCS Rafael Martin Domenech Centro de Astrobiologia, Spain

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Measuring isotopic ratios in Titan’s atmospheric nitriles Jonathon Nosowitz Catholic University of America/NASA Goddard Space Flight Center, USA

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Fingerprinting fragments of fragile interstellar molecules: dissociation chemistry of pyridine and benzonitrile revealed by infrared spectroscopy and theory Daniel Rap FELIX Laboratory, Radboud University Nijmegen, Netherlands Autoionization from the plasmon resonance in isolated 1-cyanonaphthalene Mark Stockett University of East Anglia, UK Measuring the icy content of protoplanetary disks with JWST Ardjan Sturm Leiden Observatory, Netherlands Low temperature reaction kinetics in a uniform flow inside an extended Laval nozzle characterized by REMPI and probed by rotational spectroscopy Arthur Suits University of Missouri, USA Quantifying non-thermal desorption from NH3 Ices: a comparative study of photon and electron irradiation in the valence- and core-shell energy ranges Daniela Torres Díaz ISMO, CNRS, Université Paris-Saclay, France Low-energy rotational energy transfer in water-molecular hydrogen collisions: experiments and theory Laurent Wiesenfeld Université Paris-Saclay, CNRS, France

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The role of low-energy (less than 20 eV) electrons in astrochemistry Christopher Arumainayagam 2 , Kennedy Barnes 1 , Qin Tong Wu 1 , James Battat 2 and Marco Padovani 3 1 Wellesley College, Department of Chemistry, 106 Central St, Wellesley, USA, 2 Wellesley College, Department of Physics, 106 Central St, Wellesley, USA, 3 INAF - Osservatorio Astrofisico di Arcetri, 5 Largo E. Fermi, Firenze, Italy Radiation chemistry and photochemistry inside the ice mantles surrounding micron-size dust grains within dark, dense molecular clouds likely dominate the synthesis of prebiotic molecules (e.g., glycine) in the interstellar medium 1 . We explore the relative importance of low-energy (<20 eV) secondary electrons — instigators of radiation chemistry — and low-energy photons (<10 eV) — instigators of photochemistry. We estimate the flux of cosmic-ray-induced secondary electrons within interstellar ices by 1) considering the attenuated cosmic-ray particle spectra after propagation through dark, dense molecular clouds and 2) incorporating data from the National Institute for Standards and Technology (NIST) databases to account for the total stopping power (the energy loss per unit length) for particles in liquid water. Photons produced via excitation of gaseous hydrogen within dense molecular clouds have a flux of ~10 3 photons cm −2 s −1 whereas our order-of-magnitude calculations indicate fluxes as high as ~10 2 electrons cm −2 s −1 for low-energy secondary electrons produced within interstellar ices due to incident cosmic rays. Furthermore, reaction cross-sections can be several orders of magnitude larger for electrons than for photons because (1) electron-induced singlet-to-triplet transitions are allowed, (2) electrons can be captured into resonant negative ion states that may then dissociate 2 (3) electron impact excitation is not a resonant process. Therefore, our laboratory studies and order-of-magnitude calculations suggest that the role of low-energy secondary electrons is at least as significant as that of photons in the interstellar synthesis of prebiotic molecules, which likely seeded Earth via comets and meteorites in a process referred to as molecular panspermia.

References 1. C. Arumainayagam, R. Garrod, M. Boyer, A. Hay, S. Bao, J. Campbell, J. Wang, C. Nowak, M. Arumainayagam, P. Hodge, Chem. Soc. Rev. 2019 , 48, 2293-2314 2. C. Aruminaygam, H. Lee, R. Nelson, D. Haines, R. Gunawardane, Surf. Sci. Rep. 2010 , 1, 1-44

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Chemical complexity and the role of condensed film structure: methane adsorption and Propene Oxidation Michelle Brann 1,2 , Rebecca Thompson 1,3 , Steven J. Sibener 1 1 Department of Chemistry and The James Franck Institute, 929 East 57th Street, University of Chicago, Chicago, Illinois 60637, 2 National Institute of Standards and Technology (NIST), 100 Bureau Dr,Gaithersburg, MD 20899, 3 Department of Chemistry, St. Edward's University, 3001 South Congress Austin, Texas 78704 This poster will examine the molecular adsorption and oxidative reactivity of small hydrocarbons (methane and propene) in the condensed phase. The systems experimentally model surface-mediated processes occurring on icy-dust grains to develop a more complete understanding of the formation of planetary atmospheres, complex organic molecules, and origin of life in the universe. These studies were conducted in a state-of-the-art ultra-high vacuum gas-surface scattering chamber equipped for operation involving cryogenic substrates. The chamber is connected to a differentially-pumped supersonic molecular beam line that produces reactant gases with highly- tunable kinetic energies for exposure. First, we examined the sticking probability of methane on deuterium oxide ice films with varying porosities and crystalline structures. Changes on the surface are monitored in real-time with Reflection Absorption Infrared Spectroscopy (RAIRS) and King and Wells mass spectrometry techniques. We found that the sticking probability of high energy methane is greatest for the porous films. These results suggest that porous films are more efficient at dissipating energy and that the morphology of frozen films may greatly impact the subsequent concentration and reactivity of adsorbates. To further understand how ordering in condensed films can have impact on reactivity, we next examined the oxidative reactivity of thin films of propene with particular interest towards propene epoxidation. After exposing propene to a supersonic beam of ground state atomic oxygen, O( 3 P), RAIRS spectra confirm significant propene reactivity towards a variety of products including the epoxide. Moreover, propene film thickness and ordering in the multilayer does influence oxygen penetration and mobility within the film, and therefore the resulting product formation. This work provides fundamental mechanistic insight into the sticking, diffusion, and reactivity of small molecules in condensed films. This work is critical to create accurate models of the chemical and physical processes occurring in atmospheric and terrestrial environments and to determine planetary atmospheres’ gas compositions. Ultimately, this will help us to better understand formation of solar systems and the origin of lifein the universe. References 1. Thompson, R. S.; Brann, M. R.; Sibener, S. J. Sticking Probability of High-Energy Methane on Crystalline, Amorphous, and Porous Amorphous Ice Films. Phys. Chem. C 2019 , 123 , 17855–17863. 2. https://pubs.acs.org/doi/10.1021/acs.jpcc.9b03900 Brann, M. R.; Thompson, R. S.; Sibener, S. J. Reaction Kinetics and Influence of Film Morphology on the Oxidation of Propene Thin Films by O( 3 P) Atomic Oxygen. Phys. Chem. C 2020 , 124 , 7205–7215. 3. https://pubs.acs.org/doi/10.1021/acs.jpcc.9b11439 Brann, M. R.; Hansknecht, S. P.; Ma, X.; Sibener, S. J. Differential Condensation of Methane Isotopologues Leading to Isotopic Enrichment under Non-Equilibrium Gas–Surface Collision Conditions. Phys. Chem. A 2021 , 125 , 9405–9413. https://pubs.acs.org/doi/10.1021/acs.jpca.1c07826

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Molecular mapping of comet 46P/Wirtanen using ALMA: parent vs. daughter sources in the coma

Martin Cordiner 1,2 , Stefanie Milam 1 , Nathan Roth 1,2, Steven Charnley 1 , Boncho Bonev 3 , Dominique Bockelee-Morvan 4 , Nicolas Biver 4 , Jeremie Boissier 5 , Anthony Remijan 6 1 Astrochemistry Laboratory, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA, 2 Department of Physics, Catholic University of America, Washington, DC 20064, USA, 3 Department of Physics, American University, Washington D.C., USA, 4 LESIA, Observatoire de Paris, 5 place Jules Janssen, F-92195 Meudon, France, 5 Institut de Radioastronomie Millimetrique, 300 rue de la Piscine, F-38406, Saint Martin d'Heres, France, 6 National Radio Astronomy Observatory, Charlottesville, VA 22903, USA. Molecules observed in cometary comae originate primarily from (1) outgassing by the nucleus, (2) sublimation of icy grains in the near-nucleus coma, and (3) gas-phase coma (photo-)chemistry. However, the majority of cometary gases observed at radio wavelengths have yet to be mapped, so their production mechanisms remain uncertain. Here we present ALMA observations of six molecular species towards comet 46P/Wirtanen, obtained during the comet's extremely close (~0.1 au) approach to Earth in December 2018. Emission maps of HCN, HNC, CH3OH, CH3CN, H2CO and CS were obtained at an unprecedented spatial resolution of up to 25 km, enabling the nucleus and coma sources of these molecules to be investigated. Asymmetric outgassing from the comet was modeled using our 3D, non-LTE radiative transfer code (SUBLIME). The HCN, CH3OH and CH3CN spatial distributions are found to be consistent with the majority of their production coming from direct outgassing by the nucleus, whereas CS, HNC and H2CO originate primarily from (distributed) coma sources.

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Discovery of an elevated 15N/14N ratio in the Jupiter-family comet 46P/Wirtanen using ALMA K. J. Darnell 1 , M. A. Cordiner 1 , S. N. Milam 1 , N. X. Roth 1 , S. B. Charnley 1 , A. J. Remijan 2 , D. Bockelee-Morvan 3 , N. Biver 3 1 Astrochemistry Laboratory, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA. 2 National Radio Astronomy Observatory, Charlottesville, VA 22903, USA. 3 LESIA, Observatoire de Paris, 5 place Jules Janssen, F-92195 Meudon, France. 46P/Wirtanen is a Jupiter Family comet with a short (5.4 year) orbital period. During its last apparition in 2018, it passed unusually close to the Earth (within 0.08 au), presenting an outstanding opportunity for close-up observations of its inner coma. We used the Atacama Large Millimeter/submillimeter Array (ALMA) to obtain detailed, interferometric observations of 46P in the 243-366 GHz spectral range near the comet's closest approach in December 2018, resulting in an unprecedented sky-projected spatial resolution of up to 25 km. Spectral imaging of multiple molecules was performed, and these data were analyzed using our latest non-LTE radiative transfer code (SUBLIME), to determine the detailed physical and chemical structure of the coma. In this poster, we present images and spectra of the HCN, H 13 CN and HC 15 N molecules, from which the 12 C/ 13 C and 14 N/ 15 N ratios are derived. The results are found to be consistent with a lack of significant 13 C fractionation in cometary nitriles, whereas the 14 N/ 15 N ratio indicates an enhancement in 15 N compared with protosolar (~440) and terrestrial values (~270). The ratio also appears to be lower than previously observed in other comets (~140), implying a significant 15 N enrichment in 46P's HCN. This indicates that the nitrogen in Jupiter-family comets could be more enriched in 15 N than previously thought.

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Non-linear astrochemical kinetics: theory and application Gwenaelle Dufour 1,2 S.B. Charnley 1 and J.E. Lindberg 1 1 Astrochemistry Laboratory, Code 691, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA, 2 Department of Physics, Catholic University of America, Washington, DC 20064, USA The systems of differential equations governing the kinetics of chemical reaction network scan exhibit a wide range of nonlinear dynamical phenomena: limit cycles, complex oscillations and chaos can all emerge from stable stationary solutions, subject to variation of externally controlled bifurcation parameters. One signpost of possible non-linear chemical kinetics is the presence of bistability in the stationary solutions of the associated system of differential equations. Furthermore, bistability is special as it indicates that a chemical evolution can develop incompletely different directions. To expand the understanding of chemical composition in space, it is important to characterize these processes theoretically. This work presents an overall description of

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High resolution anharmonic infrared absorption spectra of polycyclic aromatic hydrocarbons Vincent Esposito, Christiaan Boersma, Louis J. Allamandola NASA Ames Research Center, Moffett Field, CA 94035-1000 USA Emission from polycyclic aromatic hydrocarbons (PAHs) is believed to dominate the infrared (IR) spectra of a wide variety of astronomical objects and environments. Quantum chemically computed PAH spectra, combined with experimental studies, are indispensable in analyzing and interpreting astronomical observations. To provide a foundation for the analysis of the high-fidelity JWST data, new computational tools have been developed at NASA Ames to produce fully anharmonic IR absorption spectra of various PAHs with the ultimate goal of generating cascade emission spectra.

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Cyclopropenylidene chemistry in the interstellar medium Athena R. Flint, C. Zachary Palmer, Alexandria G. Watrous, Brent R. Westbrook, Blake N. Rogers, Dev J. Patel and Ryan C. Fortenberry Department of Chemistry and Biochemistry, University of Mississippi, University, Mississippi,38677-1848, USA A series of functionalized cyclopropenylidenes and functionalized cyclopropenes are quantum chemically investigated for their potential to form in the cold ISM. Cyclopropenylidene is one of the most prevalent molecules in the interstellar medium (ISM) and other cosmic environments. However, for many years after its initial detection, little was known about the kinds of chemistry in which it might participate. The detection of cyclopropenone in 2006 1 and ethynyl cyclopropenylidene in 2021, 2 and subsequent computational analysis of their formation pathways, 3,4 highlight cyclopropenylidene as an important precursor of molecules both known and unknown in the ISM. To supplement results in the literature and build a greater knowledge of the possibilites of cyclopropenylidene chemistry, chemically accurate CCSD(T)-F12/cc-pVTZ-F12 (F12-TZ) calculations are used to locate chemically viable formation pathways for various cyclopropenylidene derivatives. Four currently undetected monosubstituted cyclopropenylidenes ( c -C 3 HX, X=CN, OH, NH 2 , F), 5 three disubstituted cyclopropenylidenes ( c -C 3 XX', X or X' = C 2 H, CN), 6 and four functionalized cyclopropenes ( c -C 3 H 2 X, X=NH, CH 2 , S, CC) 7 are presented as possible cosmic chemical species. c -C 3 HCN is a likely candidate for detection due to its greatly exothermic reaction pathway (-16.10 kcal mol -1 ) and large dipole moment (3.06 D). However, a small dipole moment (0.08 D) and lack of intense vibrational modes renders c -C 3 (CN) 2 likely undetectable despite favorable formation. Other disubstituted cyclopropenylidenes have favorable spectroscopic profiles for detection. c -C 3 H 2 S and c -C 3 H 2 NH have reaction profiles largely favorable for formation when considering the possibility of competing reaction products. The formation of c -C 3 H 2 CH 2 is barriered, but such a barrier may be surmountable in circumstellar environments where a radio line for that species has been tentatively detected. 8 References

1. Hollis J. M. et al. 2006, ApJ,642,933 2. Cernicharo J. et al. 2021, A&A,649,L15 3. Ahmadvand S. 2018, PhD thesis, University of Nevada, Reno, NV 4. Fortenberry R. C. 2021, ApJ, 921, 132 5. Flint A. R. and Fortenberry R. C. 2022, ApJ, 938, 15 6. Flint A. R. et al. 2023, A&A, 671, A95 7. Flint A. R., Rogers B. N. and Fortenberry R. C. 2023, MNRAS (submitted) 8. Rojas-García O. S. et al. 2022, ApJSS, 262, 13

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The effects of small alcohols on the crystallisation behaviour of amorphous solid water Jack Fulker and Wendy Brown Department of Chemistry, University of Sussex, Falmer, Brighton, BN1 9QJ, UK Water is one of the most abundant molecules in the interstellar medium and can be found frozen out in icy mantles on the surface of dust grains. [1] Understanding the desorption behaviour of water under astronomical conditions is therefore extremely important in astrochemistry, as the conversion between gas and solid phase water can help to determine the size and age of environments such as nebulae and protoplanetary disks. However, these icy mantles are not single component, but rather a mixture of water and other small molecules, making the desorption kinetics very complex. [2] To investigate these more complex systems, surface science techniques including temperature programmed desorption (TPD) and reflection absorption infrared spectroscopy (RAIRS) have been used to investigate the effects of alcohols on the behaviour of multi-component water ices adsorbed on graphite at ~30 K. Water ice grown on a cold surface undergoes an irreversible, thermally induced phase change from amorphous solid water (ASW) to crystalline ice (CI) when heated above 148 K. [3] Due to the porous nature of the ASW ice, small molecules can become trapped within the cavities of the water ice and are then held on the surface above their natural desorption temperature. While trapped, these species can influence the water ice crystallisation behaviour and desorption kinetics. Our investigations show that small alcohols such as methanol promote crystallisation of the water ice by lowering the temperature of crystallisation (T c ) by as much as 20 K, while larger alcohols such as isopropyl alcohol and 1-butanol increase T c to the point of inhibiting the phase change completely. These changes in the water crystallisation behaviour are attributed to the disruption of the hydrogen bond network within the pores of the ASW ice. The crystallisation and desorption behaviours of water ices are important to a number of astronomy groups, particularly when investigating snowlines in star forming regions as well as the ice composition of comets. [4] The phase behaviour of water ices is also important in atmospheric chemistry, as water droplets in the Earth’s mesosphere go through a similar phase change to release trapped molecular species upon thermal processing. [5] References

1. D. A. Williams and E. Herbst, Surf. Sci. , 2002, 500 , 823–837. 2. T. Draine, Annu. Rev. Astron. Astrophys. , 2003, 41 , 241–289.

3. D.J. Burke, F. Puletti, P. M. Woods, S. Viti, B. Slater and W. A. Brown, J. Chem. Phys. , 2015, 143 , 164704. 4. M. N. Fomenkova, S. Chang and L. M. Mukhin, Geochim. Cosmochim. Acta , 1994, 58 , 4503–4512. 5. J. D. Graham and J. T. Roberts, J. Phys. Chem. , 1994, 98 , 5974–5983.

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Enhanced star formation through the high-temperature formation of H2 on carbonaceous dust grains Francesco Grieco 1,2 ,Patrice Theulé 3 , Ilse De Looze 2 , François Dulieu 1 1 CY Cergy-Paris Université,Observatoire de Paris,PSL University,Sorbonne Université,CNRS, LERMA,Cergy(France). 2 University of Ghent,Department of Physics and Astronomy,Ghent(Belgium). 3 Aix Marseille Université,CNRS,CNES,LAM,Marseille(France). Molecular hydrogen is the most abundant molecule in the Universe and its formation has implications on star formation rates over cosmic times. It is the cooling agent needed to initiate the cloud collapse regulating the star formation efficiency.[1,2]The following results can contribute to changing the H/H2 photodissociation front location and the respective size of PDR(PhotoDissociation Region), HII and molecular regions in a classical PDR picture. [3]The dominant H2 formation route depends on dust grains as catalysts, such as small carbonaceous grains, including PAHs(Polycyclic Aromatic Hydrocarbons), that have been shown to increase the H2 formation rates.[4,5] H2 formation on PAHs was thought to reduce above dust temperatures of 50K and H atom recombination was believed to be highly efficient only below 20K. Until now, laboratory and theoretical works have suggested that H2 cannot form on grains with temperatures above 100K and they do not provide a direct measurement of the recombination efficiency at dust temperatures >20K.[6,7,8,9]Here we report direct laboratory measurements of the high efficiency formation of H2 at temperatures up to 250K on a carbonaceous surface mimicking interstellar dust. We observe a plateau above 100K(20%), elevated values(30%) between 30K-80K, a maximum(45%) around 20K, a sharp decrease(20%) at 10K. This efficiency includes accretion, diffusion and reaction steps. The H2 formation pathway on surfaces can therefore be much more efficient than previously estimated, over an extended range of temperatures. H2 could start contributing to the cooling of warmer gas(T~50-250K) having a huge impact on our understanding of H2 formation in nearby galaxies and the availability of H2 reservoirs for star formation in high-redshift galaxies, in which significant dust masses have been built up and the CMB(Cosmic Microwave Background) pushes the dust temperatures to >20K.[10]This study will enable an estimation of the contribution of PAHs to interstellar H2 formation at higher temperature. Correctly accounting for H2 formation over cosmic times is a key ingredient to interpret the James Webb Space Telescope observations of the PAH grain population, the H2 line emission in local PDRs and nearby galaxies, and to study the formation of the first generations of stars in

Early Universe galaxies.[11,12] More info in Grieco et al.[13] References 1. Glover, S. C. O. & Clark, P. C. MNRAS. 437, 9–20(2014). 2. Bigiel, F. et al. Astron. J. 136, 2846(2008). 3. Tielens, A. G. G. M. & Hollenbach, D. Astrophys. J. 291, 722(1985). 4. Lipshtat, A. & Biham, O. MNRAS. 362, 666–670(2005). 5. Congiu, E., Matar, E., Kristensen, L. E., Dulieu, F. & Lemaire, J. L. MNRAS Lett. 397, L96–L100(2009). 6. Cazaux, S. & Spaans, M. Astrophys. J. 611, 40–51(2004). 7. Pirronello, V., Biham, O., Liu, C., Shen, L. & Vidali, G. Astrophys. J. 483, L131–L134(1997). 8. Cazaux, S. et al. Sci. Rep. 6, 19835(2016).

9. Wakelam, V. et al. Mol. Astrophys. 9, 1–36(2017). 10. Cunha, E. da et al. Astrophys. J. 766, 13(2013). 11. Berné, O. et al. Preprint at https://doi.org/10.1088/1538-3873/ac604c(2022). 12. Finkelstein et al. ApJ 940, 559(2022). 13. Grieco et al. Nature Astronomy(in press,2023).

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Determination of product abundances using broadband rotational spectroscopy of buffer gas cooled molecules desorbed from electron irradiated acetonitrile ices Travis Hager and Bernadette Broderick Department of Chemistry, University of Missouri, Columbia, Missouri, 65211, USA A new instrument combining buffer gas cooling with broadband chirped-pulse mm-wave spectroscopy is used here to study the products sublimed from electron irradiated ices. Pure acetonitrile ices, formed at 4 K, were irradiated with electrons to induce the production of various nitriles, such as hydrogen cyanide (HCN), hydrogen isocyanide (HNC), methylamine (CH 3 NH 2 ), methyl isocyanide (CH 3 NC), ketenimine (H 2 CCNH), and others. The primary motivation of this work is to utilize the isomer and conformer specificity of rotational spectroscopy to unambiguously determine the relative abundances of products formed from irradiation of astrobiologically important species contained within interstellar ices. We present the detection of these products and their ratios via temperature-programmed desorption coupled with 60 – 90 GHz broadband rotational spectroscopy.

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Quantification of methanol photolysis branching ratios using multiplexed photoionization mass spectrometry Emily K. Hockey 1 , Thomas Howard 1 , Julianna Palotás 1 , David L. Osborn 2 , Leah G. Dodson 1 1 University of Maryland College Park, MD, USA, 2 Combustion Research Facility, Sandia National Laboratories, Livermore, CA, USA Over 250 distinct chemical species have been detected in the interstellar regions of space. The harsh conditions of astrophysical objects mean that the molecules that form and evolve there are not subject to the same reaction conditions as on Earth. The products formed upon UV excitation of methanol, an extremely prevalent molecule in space, have not been well constrained. In a collaborative project between UMD and two government research labs-Sandia National Laboratories and Lawrence Berkeley National Laboratory-we carried out UV photodissociation studies on gas-phase methanol using 193 nm light at the Advanced Light Source synchrotron. We have identified and quantified the photodissociation products and their associated branching ratios via Multiplexed Photoionization Mass Spectrometry. Empowered by the tunability of the synchrotron source, isomeric products such as CH 3 O/CH 2 OH and HCOH/H 2CO were able to be differentiated at different ionization energies, providing a more complete understanding of each species independently. The results of this work will inform astronomers of the destruction processes possible for this important astrochemical in regions of space with high ultraviolet radiation fields.

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Photodissociation and photoionization of molecules of astronomical interest: updates to the Leiden photodissociation & photoionization cross section database Helgi Hrodmarsson 2 and Ewine van Dishoeck 1 1 Leiden University, Netherlands and 2 LISA laboratory (Université Paris-Est Créteil), France The Leiden VUV cross section database has been updated with 14 new molecular species and 16 updates to previous entries. The database update is accompanied by a brief review of the basic physical processes, particularly toward photoionization processes which have not been reviewed in the context of previous database updates. 1-4 The cross sections have been used to calculate photodissociation and photoionization rates in several different radiation fields as well as from cosmic ray induced VUV fluxes. The reduction of rates in shielded regions was calculated as a function of dust, molecular and atomic hydrogen, atomic carbon, and self-shielding column densities. The relative importance of these shielding types is molecule/atom dependent, as well as the assumed dust absorbance. All the data are publicly available from the Leiden VUV cross section database. References 1. van Dishoeck, E. F. 1988, in Rate Coefficients in Astrochemistry 2. van Dishoeck, E. F., Jonkheid, B., & van Hemert, M. C. 2006, Faraday Discuss, 133, 231 3. van Dishoeck, E. F., & Visser, R. 2015, in Laboratory Astrochemistry: From Molecules through Nanoparticles to Grains 4. Heays, A. N., Bosman, A. D., & van Dishoeck, E. F. 2017, A&A, 602, A105

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Laboratory Measurements of N2 reacting with H3+ isotopologues Dmitry Ivanov 1 , C. Bu 1 , P.-M. Hillenbrand 2 , L.W. Isberner 2 , D. Schury 1 , X. Urbain 3 and D.W. Savin 1† 1 Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027, USA 2 I. Physikalisches Institut, Justus-Liebig-Universität Gießen, 35392 Gießen, Germany 3 Institute of Condensed Matter and Nanosciences, Université catholique de Louvain, B-1348, Louvain-la-Neuve, Belgium The properties of prestellar cores and the outer midplane of protoplanetary discs can be inferred using observations of deuterated molecules [1, 2]. In particular, the N2D+-to-N2H+ abundance ratio is a commonly used diagnostic, the accuracy of which requires an accurate understanding of the underlying chemical processes forming and destroying these species. Here, we used a dual-source, ion-neutral, merged-fast-beams apparatus [3, 4] to investigate the reaction N2 + D3 + → N2D+ + D2. Fast beams of N2 + and D3 + were produced in duoplasmatron sources. The N2 + was neutralized to the X1Σ+ g ground electronic state by electron capture from N2 in a gas cell at room temperature. The D3 + was then electrostatically merged onto the neutral beam. N2D+ daughter products were detected using an electrostatic energy analyzer. Our approach enables us to measure the integral cross section for the ion-molecular reaction and thereby determine thermal rate coefficients, both to an accuracy of ~ 20%. These results can be used in astrochemical models to describe the processes taking place at dense cold regions found in prestellar cores and protoplanetary disks. This work was supported, in part, by a grant from the U.S. National Science Foundation Division of Astronomical Sciences Astronomy and Astrophysics Grants Program. References 1. Aikawa Y. et al. 2018 Astrophys. J. 885 119

2. Sipilä O. and Caselli P. 2018 Astron. Astrophys. 615 A15 3. O’Connor A et al. 2015 Astrophys. J. Suppl. Ser. 219 6 4. Hillenbrand P-M. et al. 2019 Astrophys. J. 877 38.

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A computational study of CO 2 formation on interstellar H 2 O ice Harjasnoor Kakkar, Albert Rimola Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Catalonia, Spain Solid CO 2 has been detected in various physical environments in the interstellar medium (ISM) since its first observation in 1989. [1] Despite being one of the most abundant species in the ISM and a significant component of ice mantles on dust grains, the formation route of CO 2 remains uncertain. [2] The low abundance of CO 2 in the gas phase suggests that it is exclusively formed on the solid ice surface. Moreover, there is no clear, efficient process that can account for the majority of CO 2 formation. [3] In this study, we investigate three well-known radical-neutral reaction pathways (CO with O, CO with OH, and HCHO with O) on pure water ice clusters using quantum chemical calculations. Multiple density functional theory (DFT) functionals are employed to carry out the preliminary benchmarking study on the model gas-phase reactions and determine an accurate method for describing the reaction properties. With the selected functional, potential energy surfaces of the reactions are obtained on ice models i.e., two water clusters consisting of 18 and 33 molecules. First insights will be presented based on the computational investigation that aims to determine the energetically feasible reaction mechanisms. The astrophysical implications of the results will be discussed in combination with observations from experiments and astrochemical models of these widely studied reactions. References

1. J. E. Roser, G. Vidali, et al. Astrophys. J . 2001 , 555, L61-L64. 2. M. Minissale, E. Congiu, et al. Astron. Astrophys . 2013 , 559, A49. 3. R. T. Garrod, T. Pauly. Astrophys. J . 2011 , 735, 15.

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Mono-deuterated methanol – a tool to assess the degree of thermal processing of interstellar ices? Beatrice Kulterer 1 , Maria N. Drozdovskaya 1 , Izaskun Jimenez-Serra 2 , Paola Caselli 3 , Silvia Spezzano 3 , Catherine Walsh 4 1 Center for Space and Habitability, Switzerland, 2 Centro de Astrobiología (CSIC-INTA), Spain, 3 Max-Planck-Institut für extraterrestrische Physik, Germany, 4 School of Physics and Astronomy, University of Leeds, United Kingdom Methanol, the simplest complex organic molecule is abundantly detected across the different stages of star formation, but predominantely formed at cold, prestellar stages (1,2) . In addition to the formation of methanol, the deuteration of molecules, where hydrogen is replaced by its heavier isotopologue deuterium, is also favored under cold conditions. Therefore, the ratio of the mono-deuterated methanol isotopologues, CH 2 DOH/CH 3 OD, has been proposed to act as a proxy of the dust temperature in prestellar cores. This hypothesis is motivated by variations of this ratio across the subsequent protostellar stage: values exceeding ten are found for some low- mass protostars (3) , while it approaches unity for high-mass protostellar sources (4) . A low ratio could correspond to warmer core temperatures during the prestellar stage, while a high ratio is speculated to stem from colder core temperatures. However, due to a lack of observations this ratio has not been observationally constrained yet for the prestellar stage. I will show results from a chemical model that explores a first set of experimentally derived formation schemes and implements results from quantum chemical calculations (5,6) for a range of dust temperatures, gas densities and cloud ages resembling conditions at the prestellar stage. Independent of the underlying dust temperature, CH 3 OD formation is inefficient, which questions the idea that the ratio of CH 2 DOH/CH 3 OD is set at the prestellar stage, and a suitable proxy for the dust temperature (7) . The lack of CH 3 OD at the prestellar stage is also supported by new observations of the prototypical prestellar core L1544 conducted with the IRAM 30m telescope and the Greenbank Telescope (8) . To finish, I will present ongoing work that explores additional formation pathways of deuterated methanol, such as the exchange of hydrogen and deuterium between methanol and water, which increases the abundance of CH 3 OD. Experiments have shown that this mechanism becomes effective once temperatures start to exceed 70 K (9,10) , and opens the possibility of utilizing the ratio of CH 2 DOH/CH 3 OD to trace the temperature range that ices experience during the sequential steps of star formation. This study will demonstrate if the ratio of CH 2 DOH/ CH 3 OD is an effective tool to assess the degree of thermal processing that interstellar ices are exposed to during the warm-up phase after the gravitational collapse and during the formation of a protostellar system. References 1. Geppert et al. 2006, Faraday Discussions, 133, 177

2. Watanabe et al. 2004, ApJ, 616, 638W 3. Parise et al. 2006, A&A, 453, 949P 4. Bøgelund et al. 2018, A&A, 615A, 88B 5. Nagaoka et al. 2005, ApJ, 624L, 29N 6. Song et al. 2017, ApJ, 850, 118S 7. Kulterer et al., ACS Earth and Space Chemistry, 6, 1171K

8. Kulterer et al., submitted to A&A 9. Souda 2004, PhRvL, 93, 5502 10. Ratajczak et al. 2009, A&A, 496L, 21R

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High-resolution SOFIA/EXES Spectroscopy of water absorption lines in the massive young binary W3 IRS5 Jialu Li 1 , Adwin Booger 2 , Andrew G. Barr 3 , Curtis DeWitt 4 , Alexander G.G.M. Tielens 1,2 1 University of Maryland College Park, USA, 2 University of Hawaii, USA, 3 Leiden University, The Netherlands, 4 SOFIA Science Center, USA High spectral resolution, pencil beam absorption line studies at mid-IR wavelengths provide a unique opportunity to study the physical conditions and chemical inventory of embedded phases in massive star formation [1, 2, 3]. The size of the mid-IR continuum emission region provides the effective spatial resolution of such spectroscopic observations. Thespectralresolution down to a few km/s enables individual components such as shocked gas, disks, or foreground envelopes to be resolved dynamically. Therefore, we are able to understand the interactions of the massive protostars with their environment in a better way. Among the rich chemical inventory in the regions associated with the protostars, water is one of the most abundant moleculesin both the gas and ice phaseand has a powerfuldiagnostic capability in probing physical conditions [4]. However, water is very difficult to observe from the ground. We present in this work the power of combining the SOFIA which flies high above most of the water in the Earth's atmosphere and EXES which resolves lines to several km/s in realizing water's diagnostic capability. We conducted high spectral resolution(R=50,000)spectroscopyfrom 5-8 um with SOFIA/EXES toward the hot core region close to the massive binary protostar W3 IRS5, and detected ~200 rovibrational water lines (the ν2 band). Multiple velocity components are identified and will be analyzed with complementary M-band studies on CO lines toward the same region [5]. Our preliminary rotation diagram analysis shows that the detected water lines are tracing hot gas in temperatures of ~700 K. To correctly derive the temperatures and column densities (or abundances), we will apply curve-of-growth analyses following [3] to account for the opacity effects. Once the temperatures and column densities are properly constrained, we can link individual components to those detected and distinguished by CO absorption lines. We will explore the implication of the oxygen budget by analyzing dynamically resolved water and CO in the gas and ice phase. We will also investigate the constraints of the results on the potentially existing disks around the protostars. We emphasize that many of the involved physics and chemistry in disks or hot cores in massive protostars are similar toplanet-forming disks or hot corinos around low-mass protostars thatfuture JWST/MIRI studies are interested in.However, JWST/MIRI (R=3,000) lacks the spectral resolution to separate individual dynamical components and even blends multiple transition lines into one feature. Therefore,the SOFIA/EXES studies will be instrumental in guiding future MIRI/JWST observations. References 1. Beltran, M. T. & de Wit, W. J. 2016, A&AR, 24, 6 2. Barr, A. G., et al. 2020, ApJ, 900, 104Barr, A. G., et al. 2022, ApJ, 935, 165van Dishoeck, et al. 2021, A&A, 648, A24 3. Li, J., et al. 2022, ApJ, 935, 161

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Ice origins of OCS Rafael Martín-Doménech 1,2 , Karin I. Öberg 2 , Guillermo M. Muñoz Caro 1

1 Centro de Astrobiología (CSIC-INTA). Carretera de Ajalvir, Km. 4, Torrejón de Ardoz, E-28850, Madrid, Spain. 2 Center for Astrophysics | Harvard & Smithsonian. 60 Garden St., Cambridge, MA 02138, USA The fate of sulfur in the interior of dense interstellar clouds is currently uncertain, and the fraction of sulfur present in the gas phase, ice mantles, and refractories is unconstrained [1]. As a result, the final form in which volatile sulfur is incorporated into star-forming regions and could eventually participate in prebiotic chemical networks is unknown. Complex organic and prebiotic chemistry takes place upon energetic processing of interstellar ice mantles, so the fraction of sulfur present in such ices is of particular interest. The only S-bearing ice molecule confirmed to date is OCS [2,3], while SO 2 detection remains tentative [3]. Recent observations with the NASA InfRared Telescope Facility and James Webb Space Telescope have notably increased the number of sources in which OCS ice is detected [2,3]. Understanding how the initial reservoir of sulfur in interstellar ices is built is of vital importance to understand the sulfur chemistry. Due to the low gas-phase OCS abundance, in situ ice formation is required [2]. Solid-state formation pathways suggested in the literature include oxidation of CS (CS+O) or sulfurization of CO (CO+S) through non-energetic or energetic processes [2]. The CS+O pathway has been previously studied in the laboratory through thermal reaction of CS 2 with O atoms [4], and electron irradiation of CS 2 :O 2 ices [5]. The CO+S pathway has been explored through proton and UV-photon irradiation of CO/CO 2 ices with SO 2 or H 2 S as the sulfur source [6-8]. We have expanded on these works and studied the OCS formation upon electron irradiation of CO:CS 2 and H 2 O:CS 2 ice analogs at 6 K. Formation of OCS was detected in both cases using IR spectroscopy and quadrupole mass spectrometry. We used isotopically-labeled CO in CO:CS 2 mixtures that allowed us to determine that OCS formation proceeded through both the CS+O and CO+S pathways. In H 2 O:CS 2 ice samples, OCS formation took place to a similar extent via the CS+O pathway, but any additional sulfur chemistry was significantly quenched. We have also evaluated the formation of OCS in a CH 4 :SO 2 ice where the CO and CS moieties were not initially present. In this case, the chemistry was hydrocarbon-dominated, and formation of OCS was not detected. References 1. Laas, J. & Caselli, P. 2019, A&A, 624, A108

2. Boogert, A.C.A., Brewer, K., Brittain, A., & Emerson, K.S. 2022, ApJ, 941, 32 3. McClure, M.K., Rocha, W.R.M., Pontoppidan, K.M., et al. 2023, NatAs, in press. 4. Ward, M.D., Hogg, I.A., & Price, S.D. 2012, MNRAS, 425, 1264 5. Maity, S. & Kaiser, R.I. 2013, ApJ, 773, 184 6. Ferrante, R.F., Moore, M.H., Spiliotis, M.M., & Hudson , R.L. 2008, 684, 1210 7. Garozzo, M., Fulvio, D., Kanuchova, Z., Palumbo, M.E., & Strazzulla, G. 2010, A&A, 509, A67 8. Chen, Y.-J., Juang, K.-J., Nuevo, M., et al. 2015, ApJ, 798, 80

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Measuring Isotopic ratios in Titan's atmospheric nitriles Jonathon Nosowitz 1,2 ,Martin Cordiner 2,1 ,Conor Nixon 2 , Alexander Thelen 3 , Steven Charnley 2 , Nicholas Teanby 4 , Veronique Vuitton 5 1 Catholic University of America, USA, 2 NASA Goddard Space Flight Center, USA, 3 California Institute of Technology, USA, 4 University of Bristol, UK, 5 Université Grenoble Alpes, FR Titan, Saturn's largest satellite, maintains a thick atmosphere that is composed primarily of molecular nitrogen (N 2 ) at about 98% and methane (CH 4 ) at about 1.5%. These molecules form the basis for a complex atmospheric chemical network. A diverse population of organic compounds is generated through high-altitude photochemistry, following dissociation by solar UV, or collisions by charged particles from Saturn's magnetosphere, as well as galactic cosmic rays. Some of the yielded molecules include isotopologues of those organic compounds. Studying the isotopic ratios within an atmosphere can provide key insights into its origin, evolution, and the current physical and chemical processes acting on its constituent gases. Titan's atmospheric nitriles (or cyanides, molecules that have a -CN group), have been found to contain substantially enhanced 15 N abundances compared to the values found both on Earth, and in Titan's dominant nitrogen (N 2 ) reservoir. More detailed investigation of these isotopic ratios can provide a better understanding of the synthesis of nitrogen-bearing organics in planetary atmospheres, and help constrain the origin of Titan's surprisingly large nitrogen reservoir. Among the various nitriles detected in Titan's atmosphere, we chose three as the basis for our study: HNC, CH 3 CN, and HC 3 N. These molecules were observed at high signal-to-noise ratio with the Atacama Large Millimeter/submillimeter array (ALMA) using band 6 (211-275 GHz) over 3 dates during November and December, 2019. We derived molecular abundances and carbon and nitrogen isotopic ratios as a function of altitude using a radiative transfer code designed for planetary atmospheres: Non-linear optimal Estimator for MultivariatE Spectral analySIS (NEMESIS), following methods that have previously proven successful for ALMA data. Our preliminary results show enhanced 15 N/ 14 N isotopic ratios in CH 3 CN as in other nitriles, whereas the carbon isotopic ratios ( 13 C/ 12 C) are more consistent with the bulk (Titan and terrestrial) values.

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