| Autor: |
Teolis, B. D., Shi, J., Baragiola, R. A. |
| Předmět: |
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| Zdroj: |
Journal of Chemical Physics; 4/7/2009, Vol. 130 Issue 13, p134704, 9p, 1 Chart, 8 Graphs |
| Abstrakt: |
We report experimental studies of 100 keV Ar+ ion irradiation of ice leading to the formation of molecular oxygen and its trapping and ejection from the surface, at temperatures between 80 and 150 K. The use of a mass spectrometer and a quartz-crystal microbalance and sputter depth profiling at 20 K with low energy Ar ions allowed us to obtain a consistent picture of the complex radiolytic mechanism. We show that the dependence of O2 sputtering on ion fluence is mainly due to the buildup of trapped O2 near the surface. A small proportion of the O2 is ejected above 130 K immediately upon creation from a precursor such as OH or H2O2. The distribution of trapped oxygen peaks at or near the surface and is shallower than the ion range. Measurements of sputtering of H2 help to elucidate the role of this molecule in the process of O2 formation: out-diffusion leading to oxygen enrichment near the surface. The competing phenomena of OH diffusion away from the ion track and hydrogen escape from the ice and their temperature dependence are used to explain the finding of opposite temperature dependencies of O2 and H2O2 synthesis. Based on the new data and understanding, we discuss the application of our findings to ices in the outer solar system and interstellar space. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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