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 h as been found that clusters possessing a single quantum of the N ... N stretching vibration decay on the 100 mus time scale. The rate for th e relaxation of the N ... N stretching vibration in larger N2+-He(n) c omplexes has been determined by measuring the relative intensities of hot bands involving the N ... N stretch vibration in the B <-- X spect ra and comparing with the hot-band intensity for the N2+-He complex fo r which a lifetime for the upsilon = 1 state of 220 +/- 30 mus has bee n previously measured. While for the smaller complexes (n = 1-3) the r elaxation rate is proportional to ligand number there appears to be so me saturation for the larger species (n = 4-6). The roughly linear inc rease in dissociation rate with ligand number and the ionic fragment s ize 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 collision s with the other ligands leading to further He evaporations.