Classical Calculations of Charge-Transfer Cross Sections

The utility of Gryzinski's classical procedure for estimating charge-transfer cross sections is examined. The essential content of the method is that charge transfer occurs whenever the energy transferred in a Coulomb collision between the incident ion and the transferring electron lies between specified limits. For protons incident on noble-gas and alkali atoms, it is found that the procedure in its present form is not as reliable for predicting charge-transfer cross sections as for ionization, though individual examples of remarkable agreement are found. Nevertheless, it remains possible that a more sophisticated classical approach can reasonably account for charge transfer.