Atomic charge-exchange between semi-relativistic ( v/ c = 0.49) helium ions and targets from carbon to lead

Abstract

Ratios of equilibrium charge-state yields for singly to doubly ionized 3He ions at an energy of 420 MeV were measured using the Grand Raiden magnetic spectrometer at RCNP. Targets with atomic numbers of 6, 12, 28, 40, 50 and 82 were used. It is found that theoretical calculations for atomic electron-capture and stripping cross sections, which have been successful in describing the data up to beam energies of 200 MeV, are also applicable at this higher energy. However, where at the lower energies the stripping cross sections were calculated with a combination of models by Bohr and Gillespie, the best description of the data at E( 3He) = 420 MeV is obtained when using only the model by Gillespie. The experimental results are also compared with calculations using the code CHARGE, originally developed for fast, heavy ( Z > 29) projectiles, to test the extrapolation to low- Z projectiles. It is found that the code underestimates the production of singly-charged 3He ions, in particular for heavier target nuclei.