PARTIAL AND TOTAL MULTIPHOTON DETACHMENT RATES FOR H- IN A PERTURBATIVE B-SPLINE-BASED APPROACH

An ab initio approach has been applied to study multiphoton detachment rates for the negative hydrogen ion in the lowest nonvanishing order of perturbation theory. The approach is based on the use of B splines allowing an accurate treatment of the electronic repulsion. Total deta chment rates have been determined for two- to six-photon processes as well as partial rates for detachment into the different final symmetri es. It is shown that B-spline expansions can yield accurate continuum and bound-state wave functions in a very simple manner. The calculated total rates for two- and three-photon detachment are in good agreemen t with other perturbative calculations. For more than three-photon det achment little information has been available before now. While the to tal cross sections show little structure, a fair amount of structure i s predicted in the partial cross sections. In the two-photon process, it is shown that the detached electrons mainly have s character. For f our-and six-photon processes, the contribution from the d channel is t he most important. For three-and five-photon processes p electrons dom inate the electron emission spectrum. Detachment rates for s and p ele ctrons show minima as a function of photon energy.