FORMATION OF COMPACT AMORPHOUS H{sub 2}O ICE BY CODEPOSITION OF HYDROGEN ATOMS WITH OXYGEN MOLECULES ON GRAIN SURFACES
Formation of H{sub 2}O molecules through the codeposition of oxygen molecules and hydrogen atoms is examined in situ using IR spectroscopy at 10-40 K under various O{sub 2} and H fluxes. It is found that H{sub 2}O and H{sub 2}O{sub 2} are continuously formed by reaction, even at 40 K. The H{sub 2}O ice formed is amorphous, but has a compact (not microporous) structure compared to vapor-deposited amorphous H{sub 2}O ice, because dangling OH bonds are not observed in the IR spectrum. This is consistent with astronomical observations in molecular clouds and theoretical predictions, which suggest that hydrogenation of O{sub 2} is one of the potential routes for reproducing these IR spectral characteristics. The composition of the ice formed by codeposition varies with the O{sub 2}/H ratio and temperature. Although no data are available at present for the H{sub 2}O/H{sub 2}O{sub 2} ratio of ice in molecular clouds, this study suggests that hydrogenation of O{sub 2} has a potential to yield a H{sub 2}O/H{sub 2}O{sub 2} ratio of 5 or more in molecular clouds.
- OSTI ID:
- 21313675
- Journal Information:
- Astrophysical Journal, Vol. 701, Issue 1; Other Information: DOI: 10.1088/0004-637X/701/1/464; Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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