METASTABLE DECAY OF N2+-HE(N) (V=1) (1-LESS-THAN-N-LESS-THAN-OR-EQUAL-TO-6) CLUSTERS

Laser and mass spectroscopic techniques have been combined to explore the fragmentation process of metastable N2+-He(n) ionic clusters. It has been found that clusters possessing a single quantum of the N ... N stretching vibration decay on the 100 mus time scale. The rate for the relaxation of the N ... N stretching vibration in larger N2+-He(n) complexes has been determined by measuring the relative intensities of hot bands involving the N ... N stretch vibration in the B <-- X spectra and comparing with the hot-band intensity for the N2+-He complex for which a lifetime for the upsilon = 1 state of 220 +/- 30 mus has been previously measured. While for the smaller complexes (n = 1-3) the relaxation rate is proportional to ligand number there appears to be some saturation for the larger species (n = 4-6). The roughly linear increase in dissociation rate with ligand number and the ionic fragment size distribution are consistent with a two-step fragmentation process whereby a single He atom collides inelastically with the vibrationally excited core with the recoiling N2+ undergoing intracluster collisions with the other ligands leading to further He evaporations.