IR-Induced CO Photodesorption from Pure CO Ice and CO on Amorphous Solid Water

Carbon monoxide (CO) is a key component of the icy mantles that form on the surfaces of dust grains in the interstellar medium. In dense molecular clouds, where grain temperatures are around 10 K, CO freezes out as a nonpolar layer on top of H<sub>2</sub>O ice. This CO plays an important role in the formation of complex organic molecules (COMs) through reactions with hydrogen atoms. Interstellar grains are also exposed to photons and charged particles that can both drive chemical reactions and promote desorption of molecules, providing an important link between the solid state reservoir of molecules and the gas phase. While several studies have considered UV photon driven desorption mechanisms, the UV component of the interstellar radiation field is strongly attenuated within dense clouds, with the internal cloud field being dominated by IR photons. We have used the FELIX IR Free Electron Laser (FEL) FEL-2 to irradiate a few monolayer film of CO deposited on the top of amorphous solid water (ASW) and compared the CO desorption yields to those obtained for a pure CO film. Infrared spectroscopy, combined with mass spectrometric detection of desorbing CO molecules, reveals that excitation of vibrational modes in the underlying ASW leads to significant CO desorption. This is in contrast to direct excitation of the stretching mode of CO which results in only inefficient desorption. The desorption efficiencies we derive indicate that energy transfer within ices on interstellar grains might provide an important route to IR photon-induced desorption of volatile species, such as CO.

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Publication Details

Journal
ACS Earth and Space Chemistry
Published
2025-05-22
DOI
https://doi.org/10.1021/acsearthspacechem.5c00040
Citations
2
Primary Topic
Atmospheric Ozone and Climate
Type
article
Field-Weighted Citation Impact
2.60

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article

IR-Induced CO Photodesorption from Pure CO Ice and CO on Amorphous Solid Water

Thanja Lamberts, Liv Hornekær, H. Linnartz, Wendy A. Brown et al.
2 citations
ACS Earth and Space Chemistry
Atmospheric Ozone and Climate
2.60
article

IR-Induced CO Photodesorption from Pure CO Ice and CO on Amorphous Solid Water

Thanja Lamberts, Liv Hornekær, H. Linnartz, Wendy A. Brown, H. M. Cuppen, S. Ioppolo, Jessalyn A. DeVine, J. Terwisscha van Scheltinga, Johanna G. M. Schrauwen, Gabi Wenzel, Emily R. Ingman, J. D. Thrower, Domantas Laurinavicius, Britta Redlich, Martin R. S. McCoustra, Jennifer A. Noble, Julia C. Santos, Laura Slumstrup
article en
2 citations

Abstract

Carbon monoxide (CO) is a key component of the icy mantles that form on the surfaces of dust grains in the interstellar medium. In dense molecular clouds, where grain temperatures are around 10 K, CO freezes out as a nonpolar layer on top of H<sub>2</sub>O ice. This CO plays an important role in the formation of complex organic molecules (COMs) through reactions with hydrogen atoms. Interstellar grains are also exposed to photons and charged particles that can both drive chemical reactions and promote desorption of molecules, providing an important link between the solid state reservoir of molecules and the gas phase. While several studies have considered UV photon driven desorption mechanisms, the UV component of the interstellar radiation field is strongly attenuated within dense clouds, with the internal cloud field being dominated by IR photons. We have used the FELIX IR Free Electron Laser (FEL) FEL-2 to irradiate a few monolayer film of CO deposited on the top of amorphous solid water (ASW) and compared the CO desorption yields to those obtained for a pure CO film. Infrared spectroscopy, combined with mass spectrometric detection of desorbing CO molecules, reveals that excitation of vibrational modes in the underlying ASW leads to significant CO desorption. This is in contrast to direct excitation of the stretching mode of CO which results in only inefficient desorption. The desorption efficiencies we derive indicate that energy transfer within ices on interstellar grains might provide an important route to IR photon-induced desorption of volatile species, such as CO.

ACS Earth and Space ChemistryVol. 9(6)
Leiden University (NL), Radboud University Nijmegen (NL), University of Sussex (GB), Aarhus University (DK), Aix-Marseille Université (FR), Heriot-Watt University (GB), Center for Astrophysics Harvard & Smithsonian (US), Felix Scholarship (GB), Physique des interactions ioniques et moléculaires (FR), Institute of Chemistry (CN), HFML-FELIX (NL), Leiden Observatory, Massachusetts Institute of Technology (US)
Royal Society, Agence Nationale de la Recherche, Danmarks Grundforskningsfond, Centre National d’Etudes Spatiales, Centre National de la Recherche Scientifique, H2020 Research Infrastructures
Clean water and sanitation
Openalex Percentile: Top 12%
Atmospheric Ozone and Climate
2.60
DOIOpen Access PDFOpenAlex
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