Collisional Removal of O2(5Πg) at 195 and 150 K

Details Collisional Removal of O2(5Πg) at 195 and 150 K Collisional Removal of O2(5Πg) at 195 and 150 K

May 2001

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agusm..sa31a20c&link_type=abstract

American Geophysical Union, Spring Meeting 2001, abstract #SA31A-20

Other

0310 Airglow And Aurora, 0317 Chemical Kinetic And Photochemical Properties, 0342 Middle Atmosphere--Energy Deposition, 0343 Planetary Atmospheres (5405, 5407, 5409, 5704, 5705, 5707)

Scientific paper

The weakly bound 5Πg state of O2 is expected to be a key intermediate in O + O recombination in the atmospheres of Earth and Venus, under the assumption that collisions of O2(5Πg) with N2, O2, and CO2 lead to relaxation to lower-energy vibrational levels of more strongly bound O2 states, rather than to redissociation into oxygen atoms. One way to test this hypothesis is to investigate the rates of collisional removal of O2(5 Πg) in v = 0. If upward redissociation dominates, the overall rate of removal should decrease as the temperature is decreased. On the other hand, if downward relaxation is the principal process, then the rates should stay the same, or possibly increase. In a previous AGU poster [1] we described a scheme for following the kinetics of O2(5Πg) by REMPI detection after laser excitation to high vibrational levels of O2(A3Σ u+). The rates of collisional removal by O2, N2 had about the same values at 300~K and 240~K, the two temperatures studied in detail. In this presentation we describe extension of this work to lower temperatures, 195~K and 150~K. As indicated in the following table, we find a slight increase in the removal rate when going from 240 to 195~K. At 150~K, collisional removal is significantly faster. The overall trends provide strong support for the importance of the 5Πg state of O2 in O + O recombination [2].
This research was supported by the NASA Geospace Sciences (ITM) and Planetary Atmospheres programs. [1] B.-Y. Chang, D. L. Huestis, and R. A. Copeland, ``Temperature Dependence of the Collisional Removal of O2(5Πg) Between 150 and 300 K," 1999 Spring Meeting of the Am. Geophys. Union (Boston, MA, June 1-4, 1999) [EOS, Trans. AGU, 80, S239 (1999)]. [2] D. L. Huestis, R. A. Copeland, and T. G. Slanger, ``Yields of O2 Electronic States in Oxygen Atom Recombination," 2000 Fall Meeting of the Am. Geophys. Union (San Francisco, CA, 15-19 December 2000) [Eos, Trans. AGU 81, F930 (2000)].

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