Role of Electronic Structure in Determining the Charges of Fast Ions in Matter

Some equilibrium charge-state distributions of 7-11×${10}^8$ cm/sec ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, and ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ ions in plastic films and in carbon have been determined by spectrometry of the recoils from the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(d, \alpha )$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(d, d^{\prime })$, and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(d, p)$ reactions at 15 MeV. A simple phenomenological model is presented for the capture and loss of electrons in a beam at charge-state equilibrium. The present experimental results, together with all previously published data on the equilibrium charge states in plastics of ions in the second period of the periodic table, are analyzed within the framework of the model for the influence of the electronic structure of the ions. A universal correlation with the respective ionization potentials is found when the "same" electrons are compared in all ions. Indications are that the same kind of correlation prevails also in heavier ions. The model and its resultant correlations focus upon the equality of capture and loss cross sections as the "stripping" criterion for each electron.