Pump-probe spectroscopy of ultrafast structural relaxation of electronically excited rare gas heteroclusters

Optical absorption spectra of vanadium cluster ions, Vn+, (n=3-5) were obtained in the IRUV region by measuring photodissociation action spectra of their argon-atom complexes. The spectra were analyzed with the aid of the density functional theory to obtain their most probable geometric and electronic structures. V3+was shown to be an isosceles triangular structure with bond lengths of 2.5 ? and the apex angle of 42°. On the other hand, V5+ was found to have a trigonal bipyramid structure with an isosceles basal triangle (two bond lengths of 2.6 ? and the other of 2.2 ?) and a pair of three legs (two of 2.4 ? and the other of 2.2 ?). Analysis of the spin configuration indicates that V3+ and V5+ exhibit high-spin characters (triplet), where the spin magnetic moments at each atomic site couples in an anti-parallel manner. They are in contrast to V4+, which has been shown in our previous study to be in the lowest spin state.