Material dependence on the mean charge state of light ions in titanium, zirconium and copper

Abstract

Charge cycling cross sections of lithium and helium ions are measured for atomic metal films of titanium, zirconium and copper. The material dependence of the measured charge state fractions is investigated and compared with the material density, electron density, mean ionization potential and Fermi level. The experimental data quantitatively agrees with previously documented charge exchange cross sections for thin films and shows the expected increase in the fraction of higher charge states with increasing velocity, over the ion velocity range considered. There is an observable material dependence of the charge state fraction. The measured charge state distributions are expressed as a mean charge state and compared with various mean and effective charge formalisms. The effective charge models are demonstrated to be inadequate representations of the measured mean charge states for the ions and films probed in this study.