DoubleK-shell electron capture for ion-atom collisions at intermediate energies

A three-state, two-center atomic expansion method is used to investigate double-electron capture from the K shell of multielectron atoms to the K shell of projectiles in the energy region where the projectile velocity is nearly equal to the orbital velocity of the target K-shell electron. By adopting an independent-electron approximation, the Coulomb interaction between the two electrons is replaced by monopole terms with a screening charge. The validity of this approximation is checked by comparing the cross sections for double capture in p-He and He⁺⁺-He collisions obtained from this method with other theoretical calculations and experiments. Double-electron-capture cross sections from the K shell of Ne atoms by F⁹⁺, O⁸⁺, and N⁷⁺ ions are then calculated; the results are shown to compare well with the neon Auger hypersatellite intensities measured by Woods et al.