DE-EXCITATION OF ELECTRONICALLY EXCITED SODIUM BY NITROGEN

A semiquantitative calculation is made of the cross section for the quenching of Na(32P) by molecular nitrogen, as a function of initial kinetic energy and of final vibrational quantum number, Vf, of the nitrogen molecule. The large observed cross section, which is of gas-kinetic order, can be explained in terms of an intermediate ionic state, involving Na+ and N2- (v=v-). This state is unstable at infinite separation of Na and N2, but because of the Coulomb attraction it becomes stable at collision distances below about 3 Å. As a result of the vibrational structure of both the intermediate and final states, we treat the reaction in terms of a diffusion of the probability flux through a two-dimensional network of potential-energy curves parametrized by both the electronic state and also the vibrational quantum numbers v - and vf. At each potential-energy curve crossing we compute the transition matrix element for insertion into a Landau-Zener type of transition probability. The transition matrix element is represented as the product of an electronic interaction function (obtained from a correlation, due to Hasted and Chong, of results obtained from charge-transfer processes involving multiply charged ions) and a vibrational overlap integral or Franck-Condon factor. Results are also presented on the quenching of Na(4 2P) by N2, and on the quenching of Na(32P) by CO. All the results have the same general character: The total cross section is of gas-kinetic order and depends only weakly on kinetic energy. The partial cross sections for excitation of the different final vibrational levels v f show a rather broad distribution, with somewhat more than half the energy of electronic excitation ending up as vibrational excitation. Copyright © 1969 by the American Institute of Physics.