KINETICS OF THERMALIZATION OF FAST NITROGEN-ATOMS BEYOND THE HARD-SPHERE APPROXIMATION

The thermalization of fast nitrogen atoms through elastic collisions w ith thermal oxygen atoms is studied by obtaining the energy distributi on function of fast nitrogen atoms from a direct numerical solution of the Boltzmann kinetic equation. The kernel of the Boltzmann equation is constructed using quantum mechanically evaluated differential scatt ering cross sections. The contributions to the cross sections that ari se from the six lowest NO molecular potential curves exhibit a marked dependence on both the energy and the scattering angle. It is shown th at the classical scattering cross sections are an excellent approximat ion to the smooth curve obtained by averaging the quantum mechanical c ross sections. The differences between the results of calculations of the collision kernel for the hard sphere cross sections and the actual cross sections are discussed and the steady state distribution functi on of the fast N atoms is compared with the results of kinetic calcula tions with the hard sphere approximation. Copyright (C) 1996 Elsevier Science Ltd.