HR: 0830h
AN: SA41B-0443    [PDF]
TI: Laboratory Studies of CO$_{2}$($\nu$$_{2}$)-O Vibrational Energy Transfer
AU: Castle, K J
EM: kcastle@bucknell.edu
AF: Bucknell University, 315 Rooke Chemistry Building, Lewisburg, PA 17837 United States
AU: Hwang, E S
EM: Eunsook.Hwang@hanscom.af.mil
AF: Stewart Radiance Laboratory, 139 The Great Road, Bedford, MA 01730 United States
AU: * Dodd, J A
EM: James.Dodd@hanscom.af.mil
AF: Air Force Research Laboratory, 29 Randolph Road, Hanscom AFB, MA 01731 United States
AB: For altitudes above about 80 km, oxygen molecules are increasingly dissociated by solar VUV absorption, and O atoms, together with N$_{2}$, become a principal constituent of the atmosphere. Through collisions with the ambient O atoms, the ground vibrational state of CO$_{2}$ is efficiently excited to its lowest excited vibrational state, with one quantum of energy in the $\nu$$_{2}$ bending mode. In the near-space environment, a sizable fraction of this population relaxes via 15-$\mu$ spontaneous IR 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 CO$_{2}$($\nu$$_{2}$)-O vibrational relaxation rate constant vary over a factor of six, with the laboratory measurements clustering in the 1-1.5 $\times$ 10$^{-12}$ cm$^{3}$s$^{-1}$ range, and the aeronomical estimates in the 3-6 $\times$ 10$^{-12}$ cm$^{3}$s$^{-1}$ range. We are currently pursuing vibrational relaxation measurements on the CO$_{2}$($\nu$$_{2}$)-O system in the laboratory, using the temperature jump method together with transient diode laser absorption spectroscopy detection of the CO$_{2}$ vibrational level populations. We will present the current state of progress of the experimental effort, as well as possible future directions.
DE: 0310 Airglow and aurora
DE: 0317 Chemical kinetic and photochemical properties
DE: 0342 Middle atmosphere--energy deposition
SC: SPA - Aeronomy [SA]
MN: 2003 Fall Meeting