Laboratory Studies of the Formation of Methanol and Other Organic Molecules by Water+Carbon Monoxide Radiolysis: Relevance to Comets, Icy Satellites, and Interstellar Ices
✍ Scribed by R.L. Hudson; M.H. Moore
- Publisher
- Elsevier Science
- Year
- 1999
- Tongue
- English
- Weight
- 145 KB
- Volume
- 140
- Category
- Article
- ISSN
- 0019-1035
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✦ Synopsis
Radiation processing of cometary, planetary, and interstellar ices has been investigated by irradiating mixtures of H
2 O and CO near 16 K with 0.8-MeV protons. IR spectroscopy and isotopic substitution showed that H and OH, from H 2 O, added to CO to form HCO, H 2 CO, HCOOH, and CH 3 OH. A values (integrated spectral absorbances) for HCOOH and HCO trapped in H 2 O ice were measured for the first time. These new values, along with published A's for H 2 CO and CH 3 OH, were used to calculate radiation yields (G values) and conventional percentage yields. Significantly higher percentage yields of HCOOH and CH 3 OH were observed, compared to previous solid-state H 2 O + CO experiments. This suggests that radiation processing may help explain the discrepancy between the observed gas-phase abundances of small organic molecules and the abundances predicted by current theoretical models and previous laboratory experiments. In contrast to previous experiments on one-component ices, no spectral evidence for long-chain molecules was found in the present work. This demonstrates that ice composition is a critical factor in applying laboratory results to cometary, icy satellite, and interstellar ices.