Investigation of the impact-parameter dependence of electrons emitted in 30-, 100-, 350-keV H+ and 100-keV 3He

Abstract

Energy distributions of electrons ejected in collisions of light ions with Ar atoms were measured as a function of projectile scattering angle. For this purpose the ion-electron coincidence technique was combined with the time-of-flight method for electron momentum analysis. Thus, the simultaneous detection of electrons with energies from a few hundred meV up to some keV and ions at different projectile scattering angles could be performed. The electron analyzer could observe electrons at ejection angles of 40/sup 0/--140/sup 0/ with respect to the beam axis. A time resolution of less than 400 ps was achieved with a recently developed position-sensitive ion detector. For the first time, absolute double differential yields for electron emission were measured as a function of impact parameter and electron energy for the system H/sup +/+Ar at collision energies of 30, 100, and 350 keV. Also L-shell ionization yields were determined for 30-, 100-, and 350-keV H/sup +/ and 100-keV He/sup 2+/ impact on Ar. The results are compared with predictions of the plane-wave Born approximation, an atomic orbital expansion, and the semiclassical approximation. Total L-shell ionization cross sections were deduced and compared to other measurements.