Single and double electron capture processes in slow Neq+-He (q = 10, 6) collisions

The cross sections for single and double electron capture to the states Ne9 + (n) with n=3-6 and Ne8+ (3l,n'l'), Ne8+ (4l,n'l') with n'greater than or equal to 4 and also the cross sections for single electron capture to the s tates Ne5+ (3) in collisions of Ne10+ and Ne6+ with He atoms are calculated for collision energies in the interval from 10 to 150 keV. The calculation is carried out in the multichannel Landau-Zener, Nikintin, and Landau-Zene r-Chaplik models with allowance for the radial coupling of the channels at crossing points of the energies of the quasidiabatic two-electron states of the quasimolecule. The energies of the two- electron states are calculated in the effective potential method to first order in perturbation theory in the residual electron-electron interaction. The energies of the adiabatic states in the neighborhoods of the crossings of quasidiabatic terms are det ermined by the configuration interaction method. It is found that in Ne10+- He collisions the electron is captured mainly to the n=5 state of the Ne9ion. The cross section for double electron capture to the 3lnl' state (n gr eater than or equal to 4) of the Ne8+ ion is an order of magnitude smaller than the cross section for single electron capture. The contribution to the total cross section for double electron charge transfer from the 4l4l', 4l 5l', and 4l6l' states is approximately 25%. The dependence of the cross sec tions for double electron charge transfer on the values of l and l' is inve stigated. (C) 1999 American Institute of Physics. [S1063-7842(99)00301-3].