Atomic-orbital expansion study for the (quasi-)two-electron collision system O6++He and C6++He

The atomic-orbital expansion method within the close-coupling scheme is extended to two-electron collision systems. Coupling matrix elements are evaluated with full account of electron exchange and translation. Results are presented for one-electron capture in the (quasi-)two-electron systems O 6+ +He and C 6+ +He in the energy range 0.5-40 keV amu -1 where a one-electron potential model description fails. Calculated total transfer cross sections agree very well with experiment. A comparison of subshell cross sections indicates about the same degree of convergence of the calculations as has been reached in analogous calculations for (quasi-)one-electron systems of comparable complexity.