Forward electron ejection in H+-He, He+-He and He2+-He collisions

The dependence of the parameters (width, intensity and shape) of the cusp in the processes of electron capture to the continuum (ECC) and electron loss to the continuum (ELC) has been studied as a function of impact velocity (from 2 to 5 au) for the simple collision systems H+-He, He+-He and He2+-He. An approximately linear increase in the width (FWHM) is found in both cases. There is no difference in this respect within the error limits for He2+ (ECC) and He+ (ELC). Regarding cusp shape, similar symmetry (ELC) and asymmetry (ECC) have been observed as in the case of heavy-ion projectiles. None of the theories satisfactorily describes the experimental absolute cross sections of ECC cusp (He2+), while in the case of the He+ projectile (ELC) rather good agreement with theory can be seen in the higher-velocity region. The deviation at lower velocities in the latter case could be explained by an ECC effect present even in the case of He+. Concerning the dependence of the cusp yield on the Zp value of the projectile, Z02.5+or-0.3 was obtained from the yield in H+-He and He2+-He collisions.