Systematic theoretical investigation of charge exchange in He⁺-alkali-atom collisions

A comprehensive systematic study of near-resonant charge exchange into He^*(n=2) levels in He⁺ -alkali-atom collisions is reported. The relevant quasimolecular properties of the (He-alkali)⁺ systems are obtained within the one-electron projected-valence-bond method of Kubach and Sidis. The detailed investigation of the considered systems enables one to assess the relevance of the two-state Demkov model for near-resonant charge exchange and the role of rotational coupling. The present multistate close-coupling treatment considerably improves upon the previous simplified theory of Olson and Smith and nicely reproduces the measured relative abundance of the specific He^*(2^3,1S,2^3,1P) states formed by charge exchange. The calculated summed total charge-exchange cross sections generally agree with experiment for He⁺-Cs, -Rb, and -K, whereas problems remain for He⁺-Na.