Electron Capture and Loss Cross Sections of Fast Bromine Ions in Gases

Br ions with energies of 13.9 and 25 MeV from the Oak Ridge tandem accelerator have been used to measure ionic charge-state distributions in dilute gas targets of ${\mathrm{H}}_2$, He, and Ar. A least-squares technique has been developed to obtain complete sets of electron charge-exchange cross sections from any number and range of measured nonequilibrium charge distributions. Characteristic irregularities, which originate in the atomic shell structure of the Br ions, have been found in the cross sections for capture of a single electron. Multiple electron capture and loss, as well as equilibrium charge distributions, are discussed.