Charge transfer at large internuclear distances: application to asymmetric alkali-ion--alkali-atom systems

Numerical coupled-channel two-state calculations have been employed to yield a reducedtotal-cross-section curve as a function of reduced velocity for the case where the potential curves lie parallel to one another and there is an exponential coupling between them. This plot may be used to estimate the energy dependence of the charge-transfer inelastic total cross sections for transitions that occur at large internuclear distances due to coupling between two close-lying states. We have specifically applied the above plot to several alkali-ion-alkali-atom systems and find reasonable agreement between theory and experiment. The velocity at which the total cross sections reach their maximum is obtained for the general case and is found to be in fair agreement with experiment. A comparison between the results of Demkov and these calculations is also made.