X-Ray photoelectron spectroscopy and mass spectrometry studies of X-ray-processed solid CO2

Cornelison, D. M. and Dillingham, T. R. and Tegler, S. C. and Galle, K. and Miller, G. A. and Lutz, B. L. (1998) X-Ray photoelectron spectroscopy and mass spectrometry studies of X-ray-processed solid CO2. The Astrophysical Journal, 505. pp. 443-451. ISSN 1538-4357

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Abstract

Solid CO2 films have been grown on a stainless steel substrate and processed by X-ray bombardment for up to 6 hr.. The reactions induced were monitored using X-ray photoelectron spectroscopy (XPS) and mass spectrometry. The XPS results are twofold: direct X-ray photolysis of the CO2 ice produced CO and an unidentified O product, possibly atomic O; secondary effects resulting from surface reactions between CO, O, and residual H from the vacuum environment produced H2CO, CH3OH, and a water ice cap on the CO2 film. The rate of production of CO from direct X-ray photolysis of CO2 is measured to be 5.4 × 102 molecule photon-1, corresponding to a formation cross section of 4.7 × 10-20 cm2. The growth rate for the water cap is calculated to be 2.6 × 10-4 monolayers s-1 for a partial pressure of H equal to 2 × 10-10 Torr. The appearance of gas-phase products from the film showed a time lag which indicates that the diffusion of the product species in the bulk CO2 is affected by some time-dependent process, possibly the creation of defects in the film. A model for the observed time dependence of the dissociation products in the gas phase yields diffusion coefficients in the CO2 of 5 × 10-12 and 1 × 10-12 cm2 s-1, for O and CO, respectively.

Item Type:	Article
Publisher’s Statement:	© 1998 The American Astronomical Society. Published in the Astrophysical Journal
ID number or DOI:	10.1086/306140
Keywords:	Absorption; dense molecular clouds; diffusion; discovery; hydrogen; ice analogs; infrared-spectroscopy; interstellar; Irradiation; ISM : molecules; molecular processes; Surfaces; time-dependent chemistry;
Subjects:	Q Science > QB Astronomy
NAU Depositing Author Academic Status:	Faculty/Staff
Department/Unit:	College of Engineering, Forestry, and Natural Science > Physics and Astronomy
Date Deposited:	19 Jan 2016 18:30
URI:	http://openknowledge.nau.edu/id/eprint/1856

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