title: Trapping and desorption of complex organic molecules in water at 20 K.
abstract: The formation, chemical, and thermal processing of complex organic molecules (COMs) is currently a topic of much interest in interstellar chemistry. The isomers glycolaldehyde, methyl formate, and acetic acid are particularly important because of their role as pre-biotic species. It is becoming increasingly clear that many COMs are formed within interstellar ices which are dominated by water. Hence, the interaction of these species with water ice is crucially important in dictating their behaviour. Here, we present the first detailed comparative study of the adsorption and thermal processing of glycolaldehyde, methyl formate, and acetic acid adsorbed on and in water ices at astrophysically relevant temperatures (20 K). We show that the functional group of the isomer dictates the strength of interaction with water ice, and hence the resulting desorption and trapping behaviour. Furthermore, the strength of this interaction directly affects the crystallization of water, which in turn affects the desorption behaviour. Our detailed coverage and composition dependent data allow us to categorize the desorption behaviour of the three isomers on the basis of the strength of intermolecular and intramolecular interactions, as well as the natural sublimation temperature of the molecule. This categorization is extended to other C, H, and O containing molecules in order to predict and describe the desorption behaviour of COMs from interstellar ices.
authors.affiliation: Division of Chemistry, University of Sussex, Falmer, Brighton BN1 9QJ, United Kingdom.
authors.forename: Daren J
authors.initials: DJ
authors.lastname: Burke
authors.affiliation: Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Puletti
authors.affiliation: Astrophysics Research Centre, School of Mathematics and Physics, Queen's University Belfast, University Road, Belfast BT7 1NN, United Kingdom.
authors.forename: Paul M
authors.initials: PM
authors.lastname: Woods
authors.affiliation: Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom.
authors.forename: Serena
authors.initials: S
authors.lastname: Viti
authors.affiliation: Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom.
authors.forename: Ben
authors.initials: B
authors.lastname: Slater
authors.affiliation: Division of Chemistry, University of Sussex, Falmer, Brighton BN1 9QJ, United Kingdom.
authors.forename: Wendy A
authors.initials: WA
authors.lastname: Brown