SLOWING OF ENERGETIC O(P-3) ATOMS IN COLLISIONS WITH N-2

Energetic atoms influence the composition, the thermal structure and t he evolution of the upper atmosphere. We investigate the slowing of en ergetic O(P-3) atoms by elastic and inelastic collisions with N-2. Res ults of quantum mechanical and semiclassical calculations of energy an d angle-resolved cross sections are presented for elastic and inelasti c collision of O(P-3) with N-2. A general analytical expression is dev eloped for the kernel of the Boltzmann equation for the energy distrib ution function which is valid for elastic and inelastic collisions and incorporates both the angle and the energy dependence of the cross se ctions. The Boltzmann kernel for the energy relaxation of fast O(P-3) a,toms is evaluated using the computed cross sections. We report value s of the collision frequency, the average energy loss in elastic and i nelastic collisions with N-2, and the mean time and the number of coll isions required to thermalize initially energetic O(P-3) atoms. We com pare the efficiencies of elastic and inelastic collisions in slowing d own fast O(P-3) atoms. These data are basic to the development of a re liable model of the atmospheric effects of the hot oxygen atoms produc ed by dissociative recombination, collisional quenching, photodissocia tion and photoelectron impact dissociation.