BOND STRENGTHS OF TRANSITION-METAL DIATOMICS - VNI AND V2

The abrupt onset of predissociation in an extremely congested electronic spectrum has been used to measure the bond strengths of jet-cooled VNi and V2. The resulting values are D0(VNi) = 2.100 +/- 0.002 eV and D0(V2) = 2.752 +/- 0.002 eV. A discussion of the requirements needed to determine bond strengths accurately by the onset of predissociation is presented, resulting in two criteria: (1) the molecule must possess a sufficient density of electronic states, so that non-adiabatic couplings can induce predissociation readily, and (2) the lowest separated atom limit must generate repulsive curves, so that the potential curves are not nested (and as a result, poorly coupled). Finally, comparisons of the bond strengths of V2, VNi, Ni2, NiPt, and Pt2 with the corresponding coinage metal analogues are made, and the magnitude of d-orbital contributions to the chemical bonding in these species is assessed.