Publication
Reference
Cruz-Diaz G.~A., Munoz Caro G.~M., Chen Y. -J., Yih T. -S. (2014). Vacuum-UV spectroscopy of interstellar ice analogs. I. Absorption cross-sections of polar-ice molecules. Astron. Astrophys., 562, A119.
Names
  • G.~A. Cruz-Diaz
  • G.~M. Munoz Caro
  • Y. -J. Chen
  • T. -S. Yih
Article and keywords
Title
Vacuum-UV spectroscopy of interstellar ice analogs. I. Absorption cross-sections of polar-ice molecules
Abstract
Context. The vacuum-UV (VUV) absorption cross sections of most molecular solids present in interstellar ice mantles with the exception of H$_2$O, NH$_3$, and CO$_2$ have not been reported yet. Models of ice photoprocessing depend on the VUV absorption cross section of the ice to estimate the penetration depth and radiation dose, and in the past, gas phase cross section values were used as an approximation. Aims: We aim to estimate the VUV absorption cross section of molecular ice components. Methods: Pure ices composed of CO, H$_2$O, CH$_3$OH, NH$_3$, or H$_2$S were deposited at 8 K. The column density of the ice samples was measured in situ by infrared spectroscopy in transmittance. VUV 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. Results: We provide VUV absorption cross sections of the reported molecular ices. Our results agree with those previously reported for H$_2$O and NH$_3$ ices. Vacuum-UV absorption cross section of CH$_3$OH, CO, and H$_2$S in solid phase are reported for the first time. H$_2$S presents the highest absorption in the 120-160 nm range. Conclusions: Our method allows fast and readily available VUV spectroscopy of ices without the need to use a synchrotron beamline. We found that the ice absorption cross sections can be very different from the gas-phase values, and therefore, our data will significantly improve models that simulate the VUV photoprocessing and photodesorption of ice mantles. Photodesorption rates of pure ices, expressed in molecules per absorbed photon, can be derived from our data. Data can be found at <A href=``http://ghosst.osug.fr/''>http://ghosst.osug.fr/</A>
Keywords
spectroscopy, VUV, absorption cross section, ices, molecular solids, isotopes, H2O, CO, CH3OH, NH3, H2S, interstellar grains
Content
spectral data, band list data, astrophysics
Year
2014
Journal
Astronomy and Astrophysics
Volume
562
Pages
A119
Document type
article
Publication state
published
Doi
10.1051/0004-6361/201322140
Identifiers