Photoionization of metal atom-ammonia clusters formed in supersonic beam

The results of spectroscopic studies of Me(NH3)(n) (Me=Fe, Cu, Zn) clusters formed in a supersonic beam from the laser ablated metal with gaseous ammonia are here reported. The ionization potentials of Cu(NH3)(n) 2 less than or equal to n less than or equal to 6 have been measured. The observed IPs are shifted to lower energies with respect to the bare Cu atom IF. They appear to decrease monotonically with increasing clusters size. The observed trend is consistent with a model in which the unpaired valence electron of the ground electronic state is delocalized in a well bound surface state. The data are confirmed by energetics and structure calculations performed by density functional method.