Growth mechanism of group 5 transition metal clusters elucidated by far-infrared spectroscopy

The knowledge of the electronic and geometric structure of clusters is vital for the understanding of their physical and chemical properties. However, the determination of the clusters' geometric structure is an experimental challenge. Recently, we have shown that vibrational spectroscopy in combination with density functional theory calculations can provide information on the geometric structures of free metal clusters. The experimental far-infrared spectra of free metal clusters are obtained by multiple photon dissociation (MPD) spectroscopy of their complexes with rare gas atoms, using the intense and tunable radiation of a free electron laser. We have completed the investigations on clusters of group 5 elements of the periodic table, namely vanadium, niobium, and tantalum. For all three elements many cluster sizes show remarkable similarities in their vibrational features, indicating a similar growth mechanism. Furthermore, for niobium clusters both neutral and cationic clusters have been studied, which allows for an understanding of the influence of a single electron both on the vibrational properties as well as on the clusters' geometric structure