Pulsed field ionization zero kinetic energy photoelectron spectroscopy of the vanadium dimer molecule.

The technique of pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE), photoelectron spectroscopy was employed to probe the electronic structure of the V+2 cation. Rotationally resolved PFI-ZEKE spectra of the V+2 ground state were obtained by two color excitation via the 700 nm A 3Πu←X 3Σ-g system. The observation of transitions from the A 3Π2u state to two spin–orbit components with Ω=1/2 and Ω=3/2, confirms that the cation ground state has 4Σg- symmetry, in accordance with previous experimental and theoretical work. Striking differences were observed in the rotational selection rules for the 4Σg-←A 3Π1u and the 4Σg-←A 3Π2u transitions. The adiabatic ionization potential of V2 was determined to be 51 271.14(50) cm-1. From an analysis of the rotational structure of the PFI-ZEKE spectra, the following molecular constants were determined for the 4Σg- state: r0=1.7347(24) Å, second order spin–orbit splitting, λ=5.248(17) cm-1, spin–rotation constant, γ=0.0097(87) cm-1, T0=51 282.20(50) cm-1 (1σ error bounds). © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]