FINAL-STATE PHI(2) WAVE-FUNCTION IN ION-HELIUM COLLISIONS

In this work we study the double-differential cross sections (DDCSs) o f ejected electrons in single-ionization collisions of protons with he lium atoms. The final state of the emitted electron is modeled by the correlated wave function Phi(2), a confluent hypergeometric function o f two variables. We introduce a series representation of the Phi(2) wa ve function in terms of two-body Coulomb-like states, corresponding to the electron-projectile and electron-target relative motions. We cons ider undistorted and eikonal initial states that give rise to the Born Phi(2) and eikonal initial-state Phi(2) approximations, respectively. In both cases we obtain analytic series representations of the transi tion matrices, which exhibit a strong numerical convergence. We obtain DDCSs in ion-helium collisions in the intermediate- to high-energy re gime with the Born Phi(2) approximation and show that it qualitatively agrees with the available experimental data. [S1050-2947(98)06610-4].