Comparison of hydrogen chemisorption rates and electronic structures of small Nb_nAl^- clusters: A photoelectron spectroscopic study

Photodetachment photoelectron spectroscopy experiments on Nb_nAl^- clusters have been carried out in a size range n=4 to 12 at 3.49 eV photon energy. The evolution of the electronic structure is discussed as a function of cluster size and composition. Electron affinities (EA) and vertical detachment energies are determined. One central point of this study is the direct comparison of the electronic structure of pure and Al-doped Nb_n^- clusters in the threshold binding energy region with regard to hybridization effects. Direct correlation between electronic structure and H₂ chemisorption rate constants reported by Nonose et al. [Chem. Phys. Lett. 164 (1989) 427], is found for n=5 to 8 and n>9.