Electron and recoil-ion momenta in single ionization of He by protons

Abstract

For single ionization of He atoms in collisions with fast protons we have measured and calculated, as a function of the scattering of the proton, differential reaction cross sections and mean values of the recoil momentum projected onto the transverse direction defined by the collision plane and the plane perpendicular to the proton impact velocity (the mean transverse momentum). The calculations were performed in the continuum distorted-wave eikonal initial-state (CDW-EIS) approximation. The partitioning, at a fixed scattering angle , of the total transverse recoil momentum into two mean transverse momenta, one carried by the free electron and the other by the remaining ion, is almost independent of the impact energy (250, 500 and 1000 keV). At the mean transverse electronic momentum goes to zero, but for the fraction rises smoothly and reaches 80% near 0.4 mrad. The present experimental cross sections and transverse recoil momenta are in good agreement with CDW-EIS results including the internuclear interaction.