Electron capture and excitation in alkali ion-atom collisions using an atomic eigenfunction expansion

Previous calculations of (Li⁺, Li) scattering utilizing an expansion in traveling atomic orbitals have been extended to the collisions (Na⁺, Na), (Li⁺, Na), and (Na⁺, Li). While the over‐all trends of the experimental energy dependences of the cross sections are reproduced by the theory, the detailed structure in the data is very poorly represented by our calculations. Since this structure is due to collisions at small impact parameter (less than ${\text{∼ 5\hspace{0.17em}a\hspace{0.17em}}}_0$ ) it appears that a variational technique is required to allow the atomic orbitals to contract at small separations. Unless this is done, the atomic expansion method fails badly at small impact parameter. We believe the calculations are reasonable at large impact parameters, however.