Semiclassical trajectory effects on C6+-H charge-exchange cross sections at low energy

Close-coupling charge-exchange calculations for C6+-H collisions have been carreid out for impact velocities spanning 2.5 x 104 to 5 x 105 m/s (approx.3-to-1300--eV H energy). Six appropriate molecular states were included, among which all radial and angular couplings were evaluated using the proton as an electronic origin following the approach of Piacentini and Salin. Four levels of semiclassical approximations for the nuclear motion were investigated and compared: (1) the usual straight-line impact-parameter approximation, (2) the use of a Coulomb trajectory on an effective 6/R potential, (3) the average approximation, which is a form of multitrajectory theory, and (4) a uniform semiclassical reference-function method of essentially full quantum accuracy. The results are presented and the validity of these various approximations for the nuclear motion is discussed, for the range of collision energies reported