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Title: UV PHOTODESORPTION OF METHANOL IN PURE AND CO-RICH ICES: DESORPTION RATES OF THE INTACT MOLECULE AND OF THE PHOTOFRAGMENTS

Wavelength-dependent photodesorption rates have been determined using synchrotron radiation for condensed pure and mixed methanol ice in the 7–14 eV range. The VUV photodesorption of intact methanol molecules from pure methanol ices is found to be of the order of 10{sup −5} molecules/photon, that is two orders of magnitude below what is generally used in astrochemical models. This rate gets even lower (<10{sup −6} molecules/photon) when the methanol is mixed with CO molecules in the ices. This is consistent with a picture in which photodissociation and recombination processes are at the origin of intact methanol desorption from pure CH{sub 3}OH ices. Such low rates are explained by the fact that the overall photodesorption process is dominated by the desorption of the photofragments CO, CH{sub 3}, OH, H{sub 2}CO, and CH{sub 3}O/CH{sub 2}OH, whose photodesorption rates are given in this study. Our results suggest that the role of the photodesorption as a mechanism to explain the observed gas phase abundances of methanol in cold media is probably overestimated. Nevertheless, the photodesorption of radicals from methanol-rich ices may stand at the origin of the gas phase presence of radicals such as CH{sub 3}O, therefore, opening new gas phase chemical routes for themore » formation of complex molecules.« less
Authors:
; ; ; ; ;  [1] ;  [2] ; ;  [3]
  1. LERMA, Sorbonne Universités, UPMC Univ. Paris 06, Observatoire de Paris, PSL Research University, CNRS, F-75252, Paris (France)
  2. LCP (UMR 8000), CNRS, Université Paris-Sud, F-91405 Orsay (France)
  3. Sackler Laboratory for Astrophysics, Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden (Netherlands)
Publication Date:
OSTI Identifier:
22518629
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 817; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CARBON MONOXIDE; DESORPTION; DISSOCIATION; EV RANGE; FAR ULTRAVIOLET RADIATION; ICE; METHANOL; MOLECULES; PHOTOLYSIS; PHOTONS; RADICALS; RECOMBINATION; SYNCHROTRON RADIATION