Ion-Beam Excitation Effects on the Single Charge Transfer between Argon and Nitrogen

Single charge-transfer cross sections for N2+ in argon and Ar+ in molecular nitrogen and argon have been measured as functions of ion energy and of ion-source electron energy. Ion energies studied were in the range of 50 to 1000 eV. The ion-source electron energy was varied from 16 to 24 eV for the N2+ ions, and 16 to 40 eV for Ar+. For the Ar++N2 case, the cross section appeared to be nonresonant and was insensitive to ionizing electron energy. The slightly endothermic charge transfer for the N2++Ar case also appeared to be nonresonant, but was measurably influenced by ion-source electron energy. This result is attributed to the presence of long-lived excited states of N2+ reported earlier. Evidence is presented to show that the (N2+)* ions exhibit near-resonant behavior in charge transfer with argon atoms. This suggests that the effect is due to an increased population of vibrational states v=1, 2 at higher electron energies.