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

Journal Article · Mon Feb 01 00:00:00 EST 2016 · Astrophysical Journal Letters

DOI:https://doi.org/10.3847/2041-8205/817/2/L12· OSTI ID:22518629

Bertin, Mathieu; Doronin, Mikhail; Philippe, Laurent; Jeseck, Pascal; Michaut, Xavier; Fillion, Jean-Hugues ^[1]; Romanzin, Claire ^[2]; Ligterink, Niels; Linnartz, Harold ^[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)

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 the formation of complex molecules.

• OSTI ID: 22518629
• Journal Information: Astrophysical Journal Letters, Vol. 817, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

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