depuis le 05 février 2011 :
Visualisation(s): 514 (7 ULiège)
Téléchargement(s): 79 (0 ULiège)
print        
Gustavo A. Cruz-Díaz, Rafael Martín-Doménech & Guillermo M. Muñoz Caro

Photoprocessing of astrophysical ice analogs using the Interstellar Astrochemistry Chamber

Article
Open Access

Document(s) associé(s)

Version PDF originale
Mots-clés : CH3OH, CH4, CO, CO2, glace, H2O, H2S, N2, NH3, O2, photodésortion, section efficace d’absorption, VUV

Abstract

UV-photodesorption is a plausible non-thermal desorption process in dark clouds, which is required to explain the presence of molecules in the gas phase. Models of ice photoprocessing depend on the vacuum ultraviolet (VUV) absorption cross section of the ice. In the past, gas phase cross section values were used as an approximation due to the lack of reported VUV-absorption cross sections of most molecules present in interstellar ice mantles (with the exception of H2O, CO2, and NH3). ISAC is an ultra-high-vacuum (UHV) set-up where pure ices composed of H2O, CO, CO2, CH3OH, NH3, CH4, H2S, N2, and O2 were deposited at 8 K. The column density of the ice samples was measured in situ by infrared spectroscopy in transmittance. VUV-absorption spectra of the ice samples were collected in the 120-160 nm (10.33-7.74 eV) range using a commercial microwave-discharged hydrogen flow lamp. We provide VUV-absorption cross sections of the reported molecular ices. H2S presents the highest absorption in the 120-160 nm range, while solid N2 has the lowest VUV-absorption cross section, which is about three orders of magnitude lower than that of other species. Isotopic effects were studied for D2O, 13CO2, CD3OD, and 15N2. Our method allows fast and readily available VUV spectroscopy of ices without the need of using a synchrotron beamline. Photodesorption rates of pure ices, expressed in molecules per absorbed photon, can be derived from our data.

Keywords : absorption cross section, CH3OH, CH4, CO, CO2, H2O, H2S, ice, N2, NH3, O2, photodesorption, VUV

Pour citer cet article

Gustavo A. Cruz-Díaz, Rafael Martín-Doménech & Guillermo M. Muñoz Caro, «Photoprocessing of astrophysical ice analogs using the Interstellar Astrochemistry Chamber», Bulletin de la Société Royale des Sciences de Liège [En ligne], Volume 84 - Année 2015, Actes de colloques, Workshop d'astrochimie expérimentale, 42 - 52 URL : https://popups.uliege.be:443/0037-9565/index.php?id=4651.

A propos de : Gustavo A. Cruz-Díaz

Leiden Obseravtory (Universiteit Leiden), Niels Bohrweg 2, NL-2300 CA, Leiden, The Netherlands, cruzdiaz@strw.leidenuniv.n1

A propos de : Rafael Martín-Doménech

Centro de Astrobiología (INTA-CSIC), Ctra. de Ajalvir, km 4, Torrejón de Ardoz, 28850 Madrid, Spain

A propos de : Guillermo M. Muñoz Caro

Centro de Astrobiología (INTA-CSIC), Ctra. de Ajalvir, km 4, Torrejón de Ardoz, 28850 Madrid, Spain