Trapping and desorption of complex organic molecules in water at 20 K.

The Journal of chemical physics (2015-11-02)
Daren J Burke, Fabrizio Puletti, Paul M Woods, Serena Viti, Ben Slater, Wendy A Brown
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.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Acetic acid, glacial, ReagentPlus®, ≥99%
Sigma-Aldrich
Acetic acid, glacial, ACS reagent, ≥99.7%
Sigma-Aldrich
Acetic acid, glacial, puriss., meets analytical specification of Ph. Eur., BP, USP, FCC, 99.8-100.5%
Sigma-Aldrich
Acetic acid, natural, ≥99.5%, FG
Sigma-Aldrich
Acetic acid, glacial, ≥99.99% trace metals basis
Sigma-Aldrich
Acetic acid solution, suitable for HPLC
Sigma-Aldrich
Acetic acid, glacial, puriss. p.a., ACS reagent, reag. ISO, reag. Ph. Eur., ≥99.8%
Sigma-Aldrich
Methyl formate, anhydrous, 99%
Sigma-Aldrich
Glycolaldehyde dimer, crystalline, mixture of stereoisomers. Melts between 80 and 90 °C depending on stereoisomeric composition
Sigma-Aldrich
Acetic acid, ≥99.5%, FCC, FG
Sigma-Aldrich
5α-Androstan-17β-ol-3-one, ≥97.5%
Sigma-Aldrich
Acetic acid, for luminescence, BioUltra, ≥99.5% (GC)
Sigma-Aldrich
Methyl formate, reagent grade, 97%
Sigma-Aldrich
Acetic acid, glacial, puriss., 99-100%
Sigma-Aldrich
Methyl formate, spectrophotometric grade, 99%
Sigma-Aldrich
Acetic acid-12C2, 99.9 atom % 12C
Sigma-Aldrich
Methyl formate-12C, 99.9 atom % 12C, 13C depleted
Sigma-Aldrich
Methyl formate, ≥95%