Helium excitation by protons and highly-charged-ion impact

The symmetric eikonal distorted wave method is extended to account for two-electron atom excitation by ion impact. In this formulation (SE2), the interaction between the projectile and each one of the two target electrons is taken into account in the initial and final wave functions by using the eikonal approximation. The active electron notion is not employed as both electrons are treated the same. When single configuration target wave functions are used, the SE2 transition matrix element can be expressed as a convolution of one-electron transition matrix elements. The theory is applied to the study of helium excitation by proton and highly-charged-ion impact. Experimental total and differential cross section data are well reproduced.