The Local Plasma Frequency Approach in Description of the Impact-Parameter Dependence of Energy Loss

Abstract

The LPF approach of Lindhard and Scharff is generalized to describe on the same basis the impact parameter dependence of energy loss in ion–atom collision. To make this feasible the energy loss is represented as an integral of the local energy deposition over the atomic shell volume. The local energy loss is determined by the induced electron current and the intensity of the projectile field at a given point. The LPF approach consists in an approximate description of the induced current using the corresponding expression for a uniform electron gas. With an appropriate description of the electron gas response, the atomic shell polarization and the state of electron motion are considered. The developed approach provides a possibility to test the accuracy of the customary approximation where the energy loss is expressed through the electron density on the ion trajectory, the local density approximation. A comparison with the available experimental results displays the adequateness of the developed approach if, additionally, the higher-order corrections over the projectile charge are taken into account.