Collisional quenching of O(1D) by O(3P)

Abstract

Metastable O(1D) atoms may be quenched in collisions with ground state O(3P) atoms by transitions in the avoided crossing regions of the three lowest 3[Pi]g states of O2 of which the lowest separates to O(3P) + O(3P) and the two upper to O(3P) + O(1D). Quantal calculations of the adiabatic potential energy curves of the 3[Pi]g , states are carried out with particular attention to an avoided crossing region in the lowest two states around a nuclear separation of 3.2a0. Diabatic potential matrix elements are constructed from the adiabatic curves by imposing the requirement that they be smooth everywhere. A multistate diabatic formulation is used to describe the scattering and the cross-sections for the collision-induced quenching of O(1D) atoms are calculated.The rate coefficient for the quenching of O(1D) atoms by O(3P) atoms is obtained as a function of temperature. At 1000 K, the value is 1.0 x 10-11 cm3 s-1, accurate probably to a factor of two. The theoretical rate coefficient is consistent with the empirical value inferred from upper atmosphere data.