TRANSLATIONAL AND ROTATIONAL ENERGY MEASUREMENTS OF PHOTODESORBED WATER MOLECULES IN THEIR VIBRATIONAL GROUND STATE FROM AMORPHOUS SOLID WATER

Akihiro Yabushita, Tetsuya Hama, Masaaki Yokoyama, Masahiro Kawasaki, Stefan Andersson, Richard N. Dixon, Michael N. R. Ashfold, Naoki Watanabe

Research output: Contribution to journalArticle (Academic Journal)peer-review

23 Citations (Scopus)

Abstract

For interstellar grains coated with water ice, the most important desorption mechanism at the edge of molecular clouds is photodesorption of water. To reveal details of the photodesorption mechanism, we have measured the translational and rotational energies of H2O (v = 0) molecules photodesorbed from amorphous solid water and polycrystalline ice following excitation within the first absorption band using a 157 nm laser. The measured translational and rotational temperatures are 1800 K and 300 K, respectively. These energies are in good accord with those predicted by classical molecular dynamics calculations for the "kick-out" of an H2O molecule in the ice by an energetic H atom. The statistical ortho: para ratio of g(OPR) = 3 is appropriate for the Boltzmann rotational distribution of the H2O molecules.

Original languageEnglish
Pages (from-to)L80-L83
Number of pages4
JournalAstrophysical Journal
Volume699
Issue number2
DOIs
Publication statusPublished - 10 Jul 2009

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