Applying laboratory thermal desorption data in an interstellar context: Sublimation of methanol thin films

S D Green, Amandeep S. Bolina, Rui Chen, Mark P. Collings, Wendy A. Brown, M. R S McCoustra

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Abstract

Methods by which experimental measurements of thermal desorption can be applied in astrophysical environments have been developed, using the sublimation of solid methanol as an example. The temperature programmed desorption of methanol from graphitic, amorphous silica and polycrystalline gold substrates was compared, with the kinetic parameters of desorption extracted by either a leading edge analysis or by fitting using a stochastic integration method. At low coverages, the desorption shows a substrate-dependent fractional order. However, at higher coverages methanol desorption is zeroth order with kinetic parameters independent of substrate. Using a kinetic model based on the stochastic integration analyses, desorption under astrophysically relevant conditions can be simulated. We find that the chemical and morphological nature of the substrate has relatively little impact on the desorption temperature of solid methanol, and that the substrate independent zeroth-order kinetics can provide a satisfactory model for desorption in astrophysical environments. Uncertainties in the heating rate and the distribution of grain sizes will have the largest influence on the range of desorption temperature. These conclusions are likely to be generally applicable to all species in dust grain ice mantles. © 2009 RAS.

Original languageEnglish
Pages (from-to)357-367
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Volume398
Issue number1
DOIs
Publication statusPublished - Sep 2009

Keywords

  • Astrochemistry
  • ISM: Molecules
  • Methods: Laboratory
  • Molecular data
  • Molecular processes

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