Laboratory studies of CO2(nu2)-O vibrational energy transfer

Karen J Castle; Eunsook S Hwang; James A. Dodd

doi:10.1117/12.515423

16 February 2004 Laboratory studies of CO₂(ν₂)-O vibrational energy transfer

Karen J Castle, Eunsook S Hwang, James A. Dodd

Proceedings Volume 5235, Remote Sensing of Clouds and the Atmosphere VIII; (2004) https://doi.org/10.1117/12.515423
Event: Remote Sensing, 2003, Barcelona, Spain

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 CO₂(ν₂)-O vibrational relaxation rate constant k_O(ν₂) vary over a factor of six, with the laboratory measurements clustering in the 1-1.5 × 10^-12cm³s^-1range, and the aeronomical estimates in the 3-6 × 10^-12cm³s^-1range. We are currently pursuing vibrational relaxation measurements on the CO₂(ν₂)-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.

Citation Download Citation

Karen J Castle, Eunsook S Hwang, and James A. Dodd "Laboratory studies of CO₂(ν₂)-O vibrational energy transfer", Proc. SPIE 5235, Remote Sensing of Clouds and the Atmosphere VIII, (16 February 2004); https://doi.org/10.1117/12.515423

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