INNER-SHELL CONTRIBUTION TO ELECTRON-CAPTURE IN POSITRON-ALKALI COLLISIONS

Positronium formation through electron capture from ground state alkal i targets is studied theoretically at intermediate and high impact ene rgies by means of a continuum distorted-wave approximation. In this ap proximation, distortions in the final state are introduced by using tw o Coulomb wavefunctions associated with the positron-and electron-resi dual target interactions. Total cross sections for lithium and potassi um targets are computed. An estimation of the capture from the inner s hell of lithium and potassium is given. Comparison with other theoreti cal results and experiments is made. The contribution from the inner s hells becomes important as the impact energy increases and seems to be necessary to describe the measured cross sections.