Production of ArN+ ions in the reactions Ar++N-2 and N-2(+)+Ar

We have studied the production of ArN+ starting from the two symmetric char ge-state reactants Ar+ + N-2 and N-2(+) + Ar. For both reactions we measure d the total cross sections as a function of the relative energy, in the ene rgy range from 5 to 45 eV. Estimates of the reaction thresholds and symmetr y considerations suggest that the reaction Ar+ + N-2 produces ArN+ essentia lly in its first excited state A (3)Pi, while the reaction N-2(+) + Ar prod uces ground state ArN+ ions. This fact explains the discrepancies between d ifferent estimates of the dissociation energy of ArN+ obtained in previous studies. (C) 1999 American Institute of Physics. [S0021-9606(99)01407-5].