O₂(a¹D_g ,u = 0) and O₂(b¹S_g⁺ , u = 0) Generation Following O₂(A³S_u⁺) State Excitation and O₂ Collisions

P. C. Cosby, R. A. Copeland, and T. G. Slanger
Molecular Physics Laboratory
SRI International
Menlo Park, CA 94025

Excitation of the Herzberg states of O₂ close to the dissociation limit and the resulting flow of energy down the various O₂ manifolds is a surrogate for the three-body atom recombination process. Previous studies have shown that laser excitation of the O₂(A³S_u⁺) state to the u = 7,8 levels followed by O₂ collisions results in production of O₂(b¹S_g⁺, u = 10-15) and
O₂(a¹D_g , u = 15-20), along with prompt production of O₂ molecules in the u = 0 levels of the b¹S_g⁺ and a¹D_g, states.(1) The transient vibrationally-excited populations have been probed with resonance-enhanced multiphoton ionization (REMPI). In this work we perform quantitative studies of the two u = 0 populations, to evaluate their yields in the levels from which they radiate in the atmosphere. Yields are determined by products from an ozone/oxygen system, and with this information it will ultimately be possible to convert the atmospheric u = 0 emission intensities to O-atom densities.

1) K. Kalogerakis et al., EOS Transactions 81, F944 (2000).

We gratefully acknowledge support from the NASA Planetary Atmospheres program.