Theoretical charge-exchange total cross sections forB+3+ He andC+4+ He collisions

Charge-exchange total cross sections for the ${\mathrm{B}}^{+3\mathrm{}}$ + He and ${\mathrm{C}}^{+4\mathrm{}}$ + He systems have been calculated in the velocity range $v=(1-10)\mathrm{}\times {10}^7$ cm/sec. Ab initio potential-energy curves and coupling-matrix elements were computed and employed in the impact-parameter classical-coupled equations that describe the collision to obtain the cross sections. For the ${\mathrm{B}}^{+3\mathrm{}}$ + He system, our calculations are in excellent agreement with experimental results with the finding that the single-electron-transfer cross section rises rapidly to a maximum of 1.45×${10}^{-15\mathrm{}}$ ${\mathrm{cm}}^2$ at $v=5.5\mathrm{}\times {10}^7$ cm/sec. For the ${\mathrm{C}}^{+4\mathrm{}}$ + He system, however, we find that the double-electron-transfer process is more important than the single-electron-transfer process. For example, at $v=5\mathrm{}\times {10}^7$ cm/sec, the double-electron-transfer cross section is found to be 0.6×${10}^{-16\mathrm{}}$ ${\mathrm{cm}}^2$ vs 5.5×${10}^{-17\mathrm{}}$ for the single-electron transfer. This is in disagreement with an experiment of Crandall which gave the single-charge-transfer process as dominant. However, the more recent experiment reported by Crandall, Olson, Browne, and Shipsey verifies the double charge transfer as the dominant process for low energies.