ASSOCIATIVE IONIZATION BETWEEN 2 LASER-EXCITED SODIUM ATOMS - THEORY COMPARED TO EXPERIMENT

A theoretical model for the reaction Na(3p) + Na(3p) --> Na-2(+) + e i s compared to a large number of experimental data. This model is consi dering population of long-range adiabatic Na-2 molecular states from t wo colliding excited atoms, and transfer of this population to short-r ange doubly excited autoionizing states of (3) Sigma(u)(+), (1) Sigma( g)(+), (3) Pi(u), (1) Pi(u), (1) Delta(g), and (3) Delta(u) symmetries . Good agreement is obtained with experimental results for total cross sections and polarization dependence of the ion signal at collision v elocities v(c) greater than or equal to 400 m/s. At lower velocities t he sudden approximation for spin uncoupling is not valid. The computed velocity dependence of the ion signal does nor reproduce the maximum in the ion signal observed in some experiments. [S1050-2947(98)02401-9 ].