K-shell electron capture from negative ions

Electron capture from the K-shell of a negative ion by protons is considered by accounting for the interplay between the final channel-distorted projectile and off-shell electronic scattering motions using the distorted strong-potential Born approximation. The distorted motion accounts for the ionized state of the target core and the short-range shielding of the K-shell by the passive outer-shell electrons. Total cross sections versus incident energy are compared for the negative-ion, neutral, and singly-ionized forms of the second- and third-row elements C, O, F and Si, S, Cl. Target core neutrality and diffuseness of the negative-ion screening consistently lower the cross section by amounts ranging from 22 to 37% while the positive-ion results are larger by only 1 to 15%. Previous comparison with experiment and coupled-Sturmian-pseudostate results for neutrals has shown very good agreement. (author)