Charge-Changing Cross Sections of 5-25-MeV Iodine Ions in Hydrogen and Oxygen

Iodine ions, accelerated to energies between 5 and 25 MeV, have been passed through thin targets of hydrogen and oxygen, and nonequilibrium charge-state distributions have been measured in order to obtain charge-changing cross sections. Results of cross sections for capture of one and two electrons, and for loss of one to eight electrons are presented for ions with initial charge states ranging from $2^{+}$ to ${18}^{+}$. Multiple-electron loss of iodine ions has been found to be relatively large in oxygen, but small in hydrogen. This systematic difference reveals the influence of different excitation mechanisms in energetic ion-atom collisions. The dependence of the cross sections on initial charge and velocity of the ions is discussed and, whenever possible, compared with theoretical expectations.