Multiple-scattering approach to coherent excitation in electron-capture collisions

The complete density matrix for the n = 3 level of hydrogen coherently excited by electron capture, H/sup +/+He..-->..H(n = 3)+He/sup +/, at medium to high energies is calculated with the first Born approximation and for the first time with a multiple-scattering theory, namely the continuum distorted-wave approximation. Final-state interactions are also explicitly incorporated to account for the long-range coupling effects between the degenerate states of the projectile. Comparison is made with recent experimental data and a quasiclassical interpretation of coherences in terms of the orbital parameters of the captured electron is proposed.