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Proceedings Paper

Room temperature measurements of CO2(v2)-O vibrational energy transfer
Author(s): Karen J. Castle; Katherine M. Kleissas; Justin M. Rhinehart; Eunsook S. Hwang; James A. Dodd
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Paper Abstract

In the Earth's upper atmosphere, collisions between ground state CO2 molecules and translationally excited O atoms effectively populate the bending (v2) vibrational modes of CO2. Subsequent relaxation of the v2 modes occurs through spontaneous or stimulated emission of 15-μm radiation. Much of this radiation escapes into space, thereby removing ambient kinetic energy from the atmosphere. This cooling mechanism is especially important at altitudes between 75 and 120 km where the O atom density is relatively high and the conditions are optically thin. We have performed laboratory measurements to better characterize the vibrational energy transfer efficiency for this system. Several improvements to the experiment have been made since our preliminary manuscript on this topic. The temperature-jump method is used to form vibrationally excited CO2, and transient diode laser absorption spectroscopy is used to monitor the vibrational level populations following collisions with atomic oxygen. Using this approach, the room-temperature vibrational relaxation rate coefficient, kO(v2), has been measured to be (2.0±0.3)x10-12 cm3s-1. This value is slightly higher than previous laboratory measurements, which have clustered in the (1-1.5)x10-12 cm3s-1 range, and on the low end of aeronomical estimates of (2-6)x10-12 cm3s-1.

Paper Details

Date Published: 1 November 2005
PDF: 11 pages
Proc. SPIE 5979, Remote Sensing of Clouds and the Atmosphere X, 597910 (1 November 2005); doi: 10.1117/12.627073
Show Author Affiliations
Karen J. Castle, Bucknell Univ. (United States)
Katherine M. Kleissas, Bucknell Univ. (United States)
Justin M. Rhinehart, Bucknell Univ. (United States)
Eunsook S. Hwang, Stewart Radiance Lab. (United States)
James A. Dodd, Air Force Research Lab. (United States)

Published in SPIE Proceedings Vol. 5979:
Remote Sensing of Clouds and the Atmosphere X
Klaus Schäfer; Adolfo T. Comerón; James R. Slusser; Richard H. Picard; Michel R. Carleer; Nicolaos Sifakis, Editor(s)

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