MOLECULAR-BEAM STUDIES OF AMMONIA CLUSTERED WITH METALS PRODUCED BY PULSED-LASER REACTIVE ABLATION

The results of spectroscopic studies of Me(NH,), clusters formed in th e reaction of photoablated III group metal vapor with gaseous ammonia are reported here. The photoionization spectra of Me(NH,) clusters exh ibit some features attributed to vibronic excitation of ionic clusters and transitions to autoionizing neutral Rydberg states. The first ion ization potentials of these metals clustered with more than one ammoni a molecule appear to decrease almost monotonically with increasing clu sters size. The observed trend is consistent with a model in which the unpaired valence electron of the ground electronic state is delocaliz ed in a well bound surface state. The data are confirmed by energetics and structure calculations performed by density functional method. (C ) 1998 Elsevier Science B.V.