Room temperature measurements of CO<sub>2</sub>(v<sub>2</sub>)-O vibrational energy transfer

Karen J. Castle; Katherine M. Kleissas; Justin M. Rhinehart; Eunsook S. Hwang; James A. Dodd

doi:10.1117/12.627073

1 November 2005 Room temperature measurements of CO₂(v₂)-O vibrational energy transfer

Karen J. Castle, Katherine M. Kleissas, Justin M. Rhinehart, Eunsook S. Hwang, James A. Dodd

Proceedings Volume 5979, Remote Sensing of Clouds and the Atmosphere X; 597910 (2005) https://doi.org/10.1117/12.627073
Event: SPIE Remote Sensing, 2005, Bruges, Belgium

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, k_O(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.

Citation Download Citation

Karen J. Castle, Katherine M. Kleissas, Justin M. Rhinehart, Eunsook S. Hwang, and James A. Dodd "Room temperature measurements of CO₂(v₂)-O vibrational energy transfer", Proc. SPIE 5979, Remote Sensing of Clouds and the Atmosphere X, 597910 (1 November 2005); https://doi.org/10.1117/12.627073

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