THE STRUCTURE OF NB3O AND NB3O-FIELD IONIZATION-ZERO ELECTRON KINETIC-ENERGY PHOTOELECTRON-SPECTROSCOPY AND DENSITY-FUNCTIONAL THEORY( DETERMINED BY PULSED)

The geometrical structures of the ground states of triniobium monoxide , Nb3O, and its cation, Nb3O+, have been determined by an experimental and theoretical study. Vibrationally resolved photoelectron spectra o f an Nb3O cluster beam were obtained at 100 and 300 K using the pulsed field ionization-zero electron kinetic energy technique. The spectra were simulated by calculating multidimensional Franck-Condon factors u sing the geometries and harmonic vibrational frequencies obtained from density functional theory for the minimum energy structures of the io n and neutral molecule. The rather remarkable agreement between the ex periment and the simulated spectra establishes that Nb3O and Nb3O+ hav e planar C-2v structures with the oxygen atom bridging two niobium ato ms. These are the most complex transition metal cluster structures to date to be characterized by gas phase spectroscopic techniques. (C) 19 95 American Institute of Physics.