FORMATION AND MEAN LIFETIME MEASUREMENTS OF THE LONG-LIVED DOUBLY-CHARGED HENE2+ RARE-GAS DIMER

The first observation of a long-lived doubly charged HeNe2+ rare-gas dimer is reported. This dication was obtained in charge-stripping collisions of 900 keV HeNe+ and Ar. The mean lifetime of HeNe2+, tau=184+/-32 ns, was determined by measuring the yield of its He fragments, which have dissociated after passing the analyzer, as a function of the distance between the target cell and analyzer exits. Theoretical calculations of the 1SIGMA+ ground state indicate no bound vibrational states for this shallow potential curve. Further calculations are needed to determine the long-lived electronic state which is most likely an excited state.