CO ICE PHOTODESORPTION: A WAVELENGTH-DEPENDENT STUDY

Journal Article · Sat Oct 01 00:00:00 EDT 2011 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/739/2/L36· OSTI ID:21565477

Fayolle, Edith C; Linnartz, Harold ^[1]; Bertin, Mathieu; Romanzin, Claire; Michaut, Xavier; Fillion, Jean-Hugues ^[2]; Oeberg, Karin I ^[3]

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1. Sackler Laboratory for Astrophysics, Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands)
2. Laboratoire de Physique Moleculaire pour l'Atmosphere et l'Astrophysique, Universite Pierre et Marie Curie-Paris 6, CNRS UMR7092, 75005 Paris (France)
3. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

UV-induced photodesorption of ice is a non-thermal evaporation process that can explain the presence of cold molecular gas in a range of interstellar regions. Information on the average UV photodesorption yield of astrophysically important ices exists for broadband UV lamp experiments. UV fields around low-mass pre-main-sequence stars, around shocks and in many other astrophysical environments are however often dominated by discrete atomic and molecular emission lines. It is therefore crucial to consider the wavelength dependence of photodesorption yields and mechanisms. In this work, for the first time, the wavelength-dependent photodesorption of pure CO ice is explored between 90 and 170 nm. The experiments are performed under ultra high vacuum conditions using tunable synchrotron radiation. Ice photodesorption is simultaneously probed by infrared absorption spectroscopy in reflection mode of the ice and by quadrupole mass spectrometry of the gas phase. The experimental results for CO reveal a strong wavelength dependence directly linked to the vibronic transition strengths of CO ice, implying that photodesorption is induced by electronic transition (DIET). The observed dependence on the ice absorption spectra implies relatively low photodesorption yields at 121.6 nm (Ly{alpha}), where CO barely absorbs, compared to the high yields found at wavelengths coinciding with transitions into the first electronic state of CO (A{sup 1}{Pi} at 150 nm); the CO photodesorption rates depend strongly on the UV profiles encountered in different star formation environments.

• OSTI ID: 21565477
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 2 Vol. 739; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ABSORPTION SPECTRA
ABSORPTION SPECTROSCOPY
BREMSSTRAHLUNG
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTION YIELD
DESORPTION
ELECTROMAGNETIC RADIATION
FREQUENCY DEPENDENCE
ICE
INTERSTELLAR SPACE
MAIN SEQUENCE STARS
MASS SPECTROSCOPY
OXIDES
OXYGEN COMPOUNDS
RADIATIONS
SORPTION
SPACE
SPECTRA
SPECTROSCOPY
STARS
SYNCHROTRON RADIATION
ULTRAVIOLET RADIATION
YIELDS