Correction toZPZTExpansions for Electron Capture

Abstract
For highly asymmetric electron-capture collisions, the ratio of the small charge ZP, here taken to be that of the projectile, to the large charge of the target ZT forms the natural expansion parameter. Previous treatments with use of ZPZT expansions obtain the impulse approximation which is shown to err by unknowingly neglecting terms of order (ZTv)2; a simple correction factor in the limit of small ZPv is derived.