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A Model Study of the Thermal Evolution of Astrophysical IcesWe address the question of the evolution of ices that have been exposed to radiation from stellar sources and cosmic rays. We studied in the laboratory the thermal evolution of a model ice sample: a mixture of water, hydrogen peroxide, dioxygen, and ozone produced by irradiating solid H2O2 with 50 keV H(+) at 17 K. The changes in composition and release of volatiles during warming to 200 K were monitored by infrared spectroscopy, mass spectrometry, and microbalance techniques. We find evidence for voids in the water component from the infrared bands due to dangling H bonds. The absorption from these bands increases during heating and can be observed at temperatures as high as approx. 155 K. More O2 is stored in the radiolyzed film than can be retained by codeposition of O2 and H2O. This O2 remains trapped until approx. 155 K, where it desorbs in an outburst as water ice crystallizes. Warming of the ice also drastically decreases the intrinsic absorbance of O2 by annealing defects in the ice. We also observe loss of O3 in two stages during heating, which correlates with desorption and possibly chemical reactions with radicals stored in the ice, triggered by the temperature increase.
Document ID
20060047450
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Loeffler, M. J.
(Virginia Univ. Charlottesville, VA, United States)
Teolis, B. D.
(Virginia Univ. Charlottesville, VA, United States)
Baragiola, R. A.
(Virginia Univ. Charlottesville, VA, United States)
Date Acquired
August 23, 2013
Publication Date
February 20, 2006
Publication Information
Publication: The Astrophysical Journal
Publisher: American Astronomical Society
Volume: 639
Subject Category
Astrophysics
Funding Number(s)
CONTRACT_GRANT: NAG5-13330
Distribution Limits
Public
Copyright
Other

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