ProjectileZdependence of CuK-shell vacancy production in 10-MeV/amu ion-solid collisions

Abstract

The dependence of Cu (target atom) K-shell vacancy production cross sections on projectile atomic number was investigated in collision systems for which the ratio of projectile-to-target atomic numbers ${(Z}_{1}{/Z}_{2})$ ranged from 0.34 to 2.86. A combination of energy and wavelength dispersive x-ray spectrometry was used to measure Cu K x-ray production cross sections and to determine the appropriate fluorescence yields for converting them to K-vacancy production cross sections. The high-resolution spectra also revealed the presence of sizable contributions from predominately single-ionization mechanisms not directly associated with ion-atom interactions. The role of electron capture to the projectile was examined by observing the dependence of the cross sections on target thickness. The Cu K-vacancy production cross sections determined for equilibrated projectiles display a plateau centered in the region of symmetric collisions ${(Z}_{1}{/Z}_{2}\ensuremath{\sim}1)$ and they become essentially constant beyond ${Z}_{1}=54.$ The cross sections for ${Z}_{1}>24$ fall far below a ${Z}_{1}^{2}$ scaling law and are greatly overestimated by the perturbed stationary-state theory with energy loss, Coulomb deflection, and relativistic corrections.