Atomic charge exchange between fast helium ions and targets from carbon to bismuth at β=0.36

Equilibrium charge-state distributions for singly and doubly ionized ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ ions of energy E${(}^3$He)=200 MeV (β=0.36) have been measured for atomic targets ranging from carbon to bismuth (Z=6,14,28,40,50,67,73,83). A magnetic spectrometer was used to simultaneously measure the rate of ${}_{}{}^3{}_{}{}^{}\mathrm{He}_{}^{+}{}_{}{}^{}$ ions and the current of the incident beam of ${}_{}{}^3{}_{}{}^{}\mathrm{He}_{}^{2+}{}_{}{}^{}$ ions. The ratio of the fraction of ions Y${(}^3$ ${\mathrm{He}}^{+}$/Y${(}^3$ ${\mathrm{He}}^{2+}$) was found to increase from 3×${10}^{\mathrm{-}9}$ for Z=6 to 2×${10}^{\mathrm{-}7}$ for Z=83. Very good agreement with the experimental ratios was obtained for calculated ratios based on theoretical stripping (ionization) and capture cross sections. The cross sections are dominated by capture from K orbits only for atoms up to about Z=25. For target atoms with high Z, contributions up to principal quantum numbers n=4 (N orbits) must be included.