16 February 2004 Laboratory studies of CO22)-O vibrational energy transfer
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Abstract
For altitudes above about 80 km, oxygen molecules are increasingly dissociated by solar vacuum ultraviolet absorption, and O atoms, together with N2, become a principal constituent of the atmosphere. Through collisions with the ambient O atoms, the ground vibrational state of CO2 is efficiently excited to its lowest excited vibrational state, with one quantum of energy in the ν2 bending mode. In the near-space environment, a sizable fraction of this population relaxes via 15-μm spontaneous infrared emission, which effectively converts ambient kinetic energy into radiative energy that passes into space. This process is the principal upper atmospheric cooling mechanism in the 75-120 km altitude range. Despite the importance of this mechanism, current estimates of the CO22)-O vibrational relaxation rate constant kO2) vary over a factor of six, with the laboratory measurements clustering in the 1-1.5 × 10-12 cm3s-1 range, and the aeronomical estimates in the 3-6 × 10-12 cm3s-1 range. We are currently pursuing vibrational relaxation measurements on the CO22)-O system in the laboratory, using the temperature jump method together with transient diode laser absorption spectroscopy detection of the CO2 vibrational level populations. We will present the current state of progress of the experimental effort, as well as possible future directions.
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Karen J Castle, Eunsook S Hwang, James A. Dodd, "Laboratory studies of CO22)-O vibrational energy transfer", Proc. SPIE 5235, Remote Sensing of Clouds and the Atmosphere VIII, (16 February 2004); doi: 10.1117/12.515423; https://doi.org/10.1117/12.515423
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