A four-state calculation of charge exchange in He+-Ar collisions using a quasimolecule model

The charge exchange in He+-Ar collisions into the channels He(1s2)+Ar+(3s3P6) (channel 1) and He (1s2)+Ar+(3p5) (channel 2) is studied theoretically at moderate impact energies from 1 keV up to 35 keV. The four molecular states arising from the atomic states of the elastic channel, channel 1 and channel 2 are used in a four-state impact-parameter calculation. Quasi-diabatic potential curves and coupling matrix elements are calculated ab initio. The strong rise of the total cross section for channel 1 at impact energies about 1 keV can be explained mainly by the direct radial coupling of the initial and final channel. For channel 1 the calculation of the cross section is in good agreement with experiment only up to 5 keV. The calculated cross section for channel 2 agrees well with experiment in the whole energy range.