Probabilities for K-shell ionization and capture by light ions: Scaling properties

Abstract

Theoretical approximate scaling relations for the probability of K-shell ionization and K-shell capture in collisions between moderately heavy target atoms (C, Ne and Ar) and light bare ions (H +, He 2+ and Li 3+) have been tested experimentally. The scaling with respect to the projectile charge was studied only at one intermediate scaled velocity whereas the scaling with respect to the target atomic number has been tested at several intermediate or high velocities. The scaling laws are obeyed fairly well by the present set of experimental data. The measured K-shell ionization and capture probabilities, which are smoothly decreasing functions of impact parameter, can each be characterized to a first approximation by two velocity-dependent parameters: the probability at small impact parameters, P( b≅0), and the impact parameter, b 1 2 , defined by P(b 1 2 = 1 2 P(b≅0) . The width, b 1 2 , characterizing the K-shell ionization process increases with increasing collision velocity and becomes even larger than the K-shell radius at large velocities. In contrast, the width characterizing the K-shell capture process exhibits a broad maximum of about the same size as the K-shell radius at intermediate velocities and becomes significantly smaller than this radius at large velocities.