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3034289 
Journal Article 
Glycolaldehyde, methyl formate and acetic acid adsorption and thermal desorption from interstellar ices 
Burke, DJ; Puletti, F; Brown, WA; Woods, PM; Viti, S; Slater, Ben 
2015 
1 
Monthly Notices of the Royal Astronomical Society
ISSN: 0035-8711
EISSN: 1365-2966 
447 
2 
1444-1451 
WOS:000350272900035 
We have undertaken a detailed investigation of the adsorption, desorption and thermal processing of the astrobiologically significant isomers glycolaldehyde, acetic acid and methyl formate. Here, we present the results of laboratory infrared and temperature programmed desorption (TPD) studies of the three isomers from model interstellar ices adsorbed on a carbonaceous dust grain analogue surface. Laboratory infrared data show that the isomers can be clearly distinguished on the basis of their infrared spectra, which has implications for observations of interstellar ice spectra. Laboratory TPD data also show that the three isomers can be distinguished on the basis of their thermal desorption behaviour. In particular, TPD data show that the isomers cannot be treated the same way in astrophysical models of desorption. The desorption of glycolaldehyde and acetic acid from water-dominated ices is very similar, with desorption being mainly dictated by water ice. However, methyl formate also desorbs from the surface of the ice, as a pure desorption feature, and therefore desorbs at a lower temperature than the other two isomers. This is more clearly indicated by models of the desorption on astrophysical time-scales corresponding to the heating rate of 25 and 5 M-circle dot stars. For a 25 M-circle dot star, our model shows that a proportion of the methyl formate can be found in the gas phase at earlier times compared to glycolaldehyde and acetic acid. This has implications for the observation and detection of these molecules, and potentially explains why methyl formate has been observed in a wider range of astrophysical environments than the other two isomers. 
astrochemistry; molecular processes; methods: laboratory; stars: formation; ISM: molecules; infrared: ISM