Singly ionizing 100-MeV/amu C6++He collisions with small momentum transfer

Abstract

We present a theoretical analysis of single ionization of He by C${}^{6+}$ at an impact energy of 100 Mev/amu and a momentum transfer $Q=0.75$ a.u. Relativistic, second-order Born, and distorted-wave effects on fully differential cross sections are examined. It is demonstrated that neither of them is able to explain the serious discrepancy observed between theory and experiment when an electron is ejected perpendicular to the direction of momentum transfer. We show, however, that experimental uncertainties, including those due to a velocity spread of the He gas atoms in a supersonic jet, can be responsible for the observed disagreement.