Differential cross sections for state-selective electron capture in 25-100-keV proton-helium collisions.

Abstract

Cross sections differential in the scattering angle of the projectile are presented for electron capture summed over all states and to the 2{ital s}, 2{ital p}, 3{ital s}, 3{ital p}, 4{ital s}, and 4{ital p} states of hydrogen in 25-, 50-, and 100-keV proton-helium collisions. The classical-trajectory Monte Carlo (CTMC) technique was employed for these calculations as well as to compute total cross sections as a function of impact energy. The latter are compared with experiment to display the behavior of the integral state-selective cross sections in this energy regime. Detailed comparison is also made between the calculated angular differential cross sections and the experimental measurements of Martin {ital et} {ital al}. (Phys. Rev. A 23, 285 (1981)) for capture summed over all states and of Seely {ital et} {ital al}. (Phys. Rev. A 45, R1287 (1992)) for capture to the 2{ital p} state. Very good overall agreement is found. Regarding the cross section for capture summed over all states, an improved agreement is demonstrated by using an alternate representation of the initial state in the CTMC method, which improves the electronic radial distribution but which cannot presently be applied to state-selective determinations.