Gas phase infrared spectroscopy of mono- and divanadium oxide cluster cations.

The vibrational spectroscopy of the mono- and divanadium oxide cluster cations VO(1-3)+ and V2O(2-6)+ is studied in the region from 600 to 1600 wave numbers by infrared photodissociation of the corresponding cluster cation-helium atom complexes. The comparison of the experimental depletion spectra with the results of density functional calculations on bare vanadium oxide cluster cations allows for an unambiguous identification of the cluster geometry in most cases and, for VO(1-3)+ and V2O(5,6)+, also of the electronic ground state. A common structural motif of all the studied divanadium cluster cations is a four-membered V-O-V-O ring, with three characteristic absorption bands in the 550-900 wave number region. For the V-O-V and V=O stretch modes the relationship between vibrational frequencies and V-O bond distances follows the Badger rule.