HR: 0800h
AN: SA11A-0221    [Abstracts]
TI: Laboratory Measurements of Ozone - M Vibrational Energy Transfer
AU: * Castle, K J
EM: kcastle@bucknell.edu
AF: Bucknell University, Department of Chemistry, Lewisburg, PA 17837 United States
AU: Rhinehart, J M
EM: jrhineha@bucknell.edu
AF: Bucknell University, Department of Chemistry, Lewisburg, PA 17837 United States
AU: Dodd, J A
EM: James.Dodd@hanscom.af.mil
AF: Air Force Research Laboratory/VSBYM, 29 Randolph Rd., Hanscom AFB, MA 01731 United States
AB: In preliminary work, we explore using a temperature-jump method, similar to what has been used in our ongoing CO₂(ν₂)-O energy transfer studies, to measure vibrational energy transfer efficiencies in O₃-M encounters, where M=O₂, N₂, or O. A lingering concern in the analysis of NASA`s TIMED/SABER data involves the 9.6 micron channel, where the observed radiance is dominated by intense emission from the O₃(ν₃) asymmetric stretch level. Hot band emission trailing to longer wavelengths is also present, arising from vibrationally excited O₃ initially populated by O + O₂ three-body recombination. Poor knowledge of the relevant collisional quenching rate coefficients constitutes one of the most significant deficiencies in the non-LTE models used to retrieve ozone densities from SABER data. Specifically, accurate rate parameters for the relaxation of vibrationally-excited O₃ by the major atmospheric species in the mesosphere and lower thermosphere, N₂, O₂, and O, are required. The O₃(v)-O₂, N₂quenching rate coefficients derived from existing laboratory measurements vary over a substantial range, and there exists only a single published measurement of O-atom quenching coefficients. The proposed method involves a slow-flowing, dilute mixture of O₃ in Xe bath gas. A 266 nm laser pulse is used to dissociate a small fraction of the O₃, forming O atoms and stimulating a modest temperature increase. The O₃ vibrational level populations redistribute according to the new temperature, and the excited vibrational level populations are monitored via transient diode laser absorption spectroscopy as they return to equilibrium. Rate parameters are determined by effectively plotting the redistributions rates against the quencher concentration. Any promising data or experimental progress will be discussed.
DE: 0358 Thermosphere: energy deposition (3369)
SC: SPA-Aeronomy [SA]
MN: Fall Meeting 2005