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

TY - JOUR

T1 - IR-Induced CO Photodesorption from Pure CO Ice and CO on Amorphous Solid Water

AU - Slumstrup, Laura

AU - Thrower, John D.

AU - Schrauwen, Johanna G.M.

AU - Lamberts, Thanja

AU - Ingman, Emily R.

AU - Laurinavicius, Domantas

AU - DeVine, Jessalyn

AU - Terwisscha van Scheltinga, Jeroen

AU - Santos, Julia C.

AU - Noble, Jennifer A.

AU - Wenzel, Gabi

AU - McCoustra, Martin R.S.

AU - Brown, Wendy A.

AU - Linnartz, Harold

AU - Hornekær, Liv

AU - Cuppen, Herma M.

AU - Redlich, Britta

AU - Ioppolo, Sergio

N1 - Publisher Copyright: © 2025 The Authors. Published by American Chemical Society.

PY - 2025/6/19

Y1 - 2025/6/19

N2 - 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 H2O 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.

AB - 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 H2O 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.

KW - astrochemistry

KW - ice

KW - infrared

KW - interstellar

KW - irradiation

KW - ISM

KW - mass spectrometry

KW - solid-state

UR - http://www.scopus.com/inward/record.url?scp=105006570112&partnerID=8YFLogxK

U2 - 10.1021/acsearthspacechem.5c00040

DO - 10.1021/acsearthspacechem.5c00040

M3 - Journal article

AN - SCOPUS:105006570112

SN - 2472-3452

VL - 9

SP - 1607

EP - 1621

JO - ACS Earth and Space Chemistry

JF - ACS Earth and Space Chemistry

IS - 6

ER -