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BEAU J. BARKER, SEAN M. CASEY, SIMSON ALEX, DOREEN G. LEOPOLD, Department of Chemistry, University of Minnesota, Minneapolis, MN 55455.
The heteronuclear diatomic metal ions CrV- and MoV- were investigated using negative ion photoelectron spectroscopy. These bare, heteronuclear group 5 and 6 transition metal dimers allow the study of multiple metal-metal bonding free of ligand effects. The photoelectron spectra, obtained at 488 nm with an instrumental resolution of about 5 meV (40 cm-1), provide measurements of the electron affinities, vibrational frequencies for both the anion and neutral states, bond length changes upon electron detachment, excited electronic state energies and spin-orbit splittings. The CrV- and MoV- spectra display transitions to the multiply-bonded 2
(d
)4(d
)3(d
)2(s
)2 ground states of the neutral molecules and to several excited states. Addition of an electron to the vacant
* orbital gives the 3
anion, which is found to be the ground state of CrV- but a low lying excited state of MoV-. Addition of a d
electron yields the 1
+ MoV- ground state. Density functional theory calculations of the anions and neutrals were performed to help elucidate the spectroscopic assignments and observed periodic trends.