Distribution in angle of the Bloch correction in electronic stopping

Abstract

The position in angular space of the Bloch correction to the perturbative electronic stopping power formula of Bethe is investigated. It is demonstrated that this nonperturbative correction which originates in close collisions between the penetrating ion and target electrons appears at small scattering angles and that its position depends on the (adiabatic) cutoff at large distances. In the limit of infinite range the correction moves to infinitely small angles but remains finite and both the exact and the perturbative cross sections approach the Rutherford value at all finite angles. The picture is consistent with the lack of a Bloch-type correction in the energy-loss straggling. {copyright} {ital 1997} {ital The American Physical Society}