Charge transfer in collisions of B2+(2S,2P) and B3+(1S) ions with He atoms below 200 keV.

Abstract

Charge transfer in ${\mathrm{B}}^{2+}$${(}^{2}$S${,}^{2}$P)+He and in ${\mathrm{B}}^{3+}$${(}^{1}$S)+He collisions is studied theoretically by using a semiclassical molecular representation with 8 and 12 molecular channels for ${\mathrm{B}}^{2+}$ and ${\mathrm{B}}^{3+}$ on He systems, respectively, at collision energies between 200 eV and 200 keV for the former and between 600 eV and 50 keV for the latter. The ab initio potential curves and nonadiabatic coupling matrix elements are obtained from the multireference single- and double-excitation configuration-interaction (MRD-CI) calculations for the ${\mathrm{B}}^{2+}$-He system and a pseudopotential-modified configuration-interaction method for the ${\mathrm{B}}^{3+}$-He system. The present cross sections for charge transfer by the ground state ${\mathrm{B}}^{2+}$ ions are found to have a broad maximum with a magnitude as large as 2\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}15}$ ${\mathrm{cm}}^{2}$ at 100 keV and those by an excited ${\mathrm{B}}^{2+}$${(}^{2}$P) state are found to be larger by a factor of 6 than those by the ground state in the same energy regime. ${\mathrm{B}}^{2+}$-excitation cross sections are smaller than those for charge transfer below 1 keV, while they increasingly dominate above this energy. The present total charge-transfer cross section for ${\mathrm{B}}^{3+}$ in collisions with He is similar to that obtained in earlier work by Gargaud et al. [J. Phys. B 27, 3985 (1994)] both in magnitude and energy dependence, but is found to show slightly different ${\mathrm{B}}^{2+}$(2s) and ${\mathrm{B}}^{2+}$(2p) production ratio. \textcopyright{} 1996 The American Physical Society.