Metal-insulator segregation in lithium rich LinHm + clusters

The metallicity of lithium rich LinHm + cluster ions [1⩽m⩽6, n⩽22, and (n–m)>3] is studied by measuring unimolecular dissociation rates. These clusters are found to decompose by evaporation of a Li atom or a Li2 molecule. The evaporative rates of mixed clusters display features characteristic of metallic clusters. This confirms and extends to a larger size range the previous results obtained by photoionization and absorption cross-section measurements. The simulation of the evaporative rates, with a statistical Rice–Ramsperger–Kassel (RRK) model which has been adapted to mixed clusters, confirms that there is a clear separation between a metallic Lin–m + part and an insulating (LiH)m part.