Screening and antiscreening by projectile electrons in high-velocity atomic collisions

Abstract

The scattering amplitude for a projectile of nuclear charge ${Z}_{1}$ carrying $N$ electrons colliding with an atomic target with charge ${Z}_{2}$, evaluated in the first Born approximation using hydrogenic wave functions, is compared with recent experimental results. In the present approximation where the minimum momentum transfer ${t}_{min}$ is considered to be approximately independent of the final state of the projectile, the differential cross sections separate into a product of one term that depends only on the target times the square ${Z}_{1}^{2}(t)$ of an effective projectile charge. Here an analytic expression for ${Z}_{1}^{2}(t)$ is given for 2, 1, and 0 electrons. Some total ionization cross-section ratios are also given.