Associative Ionization in Collisions of H Plus + H- and H(1s) + H(ns)

Associative ionization in collisions of H+ + H- as well as H(1s) + H(ns) with n = 2, 3, 4 is studied theoretically. Relevant adiabatic potential curves and nonadiabatic couplings are calculated ab initio and the autoionization from the lowest electronic resonant states in the 11+g/u and 31+g/u symmetries are considered. The cross sections are obtained by solving the coupled Schrodinger equation, including a complex potential matrix, in a strict diabatic representation. The importance of using a nonlocal description of autoionization is investigated. Associative ionization is also studied for different isotopes of hydrogen. Calculated cross sections are compared with results from measurements.