PHOTOELECTRON-SPECTRA AND GEOMETRIC STRUCTURES OF SMALL NIOBIUM CLUSTER ANIONS

Photoelectron spectroscopy measurements and density functional theory calculations are combined to determine structures of Nb-n(-) (n = 3-8) clusters. A detailed comparison between observed and calculated elect ronic binding energies shows that the clusters have low-symmetry compa ct 3D structures and the lowest possible total spin, except for the th ree- and five-atom clusters which are in triplet states. We find evide nce for the coexistence of two isomers of Nb-8(-) under some experimen tal conditions. This approach shows great promise for structural chara cterization of small clusters.