HR: 0800h
AN: SA11A-0222    [Abstracts]
TI: Quenching of CO₂(ν₂) by O: New Results and Analysis
AU: * Dodd, J A
EM: James.Dodd@hanscom.af.mil
AF: Air Force Research Laboratory, VSBYM 29 Randolph Road, Hanscom AFB, MA 01731-3010
AU: Castle, K J
EM: kcastle@bucknell.edu
AF: Bucknell University, Dept. of Chemistry 315 Rooke Chemistry Building, Lewisburg, PA 17837
AU: Rhinehart, J M
EM: jrhineha@bucknell.edu
AF: Bucknell University, Dept. of Chemistry 315 Rooke Chemistry Building, Lewisburg, PA 17837
AU: Hwang, E S
EM: Eunsook.Hwang@hanscom.af.mil
AF: Stewart Radiance Laboratory, 139 The Great Road, Bedford, MA 01730
AB: New results from ongoing laboratory measurements of CO₂(ν₂) + O vibrational energy transfer (VET) will be presented. The process is a key contributor to both the CO₂ 15-μm emission intensity and to upper atmospheric cooling in the 75-120 km altitude range. A 266-nm laser pulse photolyzes O₃, producing O atoms and initiating a temperature jump, while transient diode laser absorption spectroscopy is used to monitor the CO₂(ν₂) level population. We report the latest measurement results, including improvements in the experiment that have mitigated vibrational cascading effects, and the development of a powerful global kinetic fitting routine to allow the simultaneous determination of the appropriate rate parameters from a large body of data. Predictions of upper atmospheric density and temperature are sensitive to the input value of the CO₂(ν₂) + O relaxation rate constant k_o(ν₂), including its temperature dependence. Aeronomic models imply that increasing CO₂ levels from anthropogenic sources will cause the thermosphere to cool and contract over time. The model results are supported by analyses of satellite orbital motion data over the past 40 years, which are consistent with a few percent thermospheric density decrease per decade. This has important implications for spacecraft drag and orbital longevity. It also provides an interesting connection between a molecular-level parameter, the CO₂ + O VET efficiency, and the macroscopic effects of atmospheric density and temperature.
DE: 0317 Chemical kinetic and photochemical properties
DE: 0340 Middle atmosphere: composition and chemistry
DE: 0342 Middle atmosphere: energy deposition (3334)
DE: 0355 Thermosphere: composition and chemistry
DE: 0358 Thermosphere: energy deposition (3369)
SC: SPA-Aeronomy [SA]
MN: Fall Meeting 2005