Electron capture and excitation in slow H++He*(n=3) collisions

The electron-capture and excitation processes in slow collisions of protons with He*(1s3l) are studied using the close-coupling method within the semi classical approximation. The Stark splitting of electron-capture states on H is explicitly taken into account and the coupling-matrix elements between these states and the initial angular-momentum states on He are calculated analytically. The cross sections for excitation (de-excitation) and single- electron capture to specific spherical hydrogen states have been calculated in the relative velocity range 2 x 10(6)-1.3 x 10(8) cm s(-1). The cross s ection values for both types of processes in the considered velocity range are found to be large (10(-14)-10(-13) cm(2)) due to the large values of el ectron-exchange couplings at large internuclear distances. The excitation ( de-excitation) processes are controlled by two-step exchange (capture and r e-capture) transitions rather than by direct coupling among the states cent red on He.