GROUND STATE OF THE $Nb_{2}^{+}$ MOLECULE

$^{1}$ S. P. Walch and C. W. Bauschlicher, Jr, in Comparison of Ab Initio Quantum Chemistry with Experiment for Small Molecules, ed. R. J. Bartlett, Reidel, Dordrecht (1985). $^{2}$ S. K. Loh, L. Lian, and P. B. Armentrout, J. Am. Chem Soc. 111, 3167 (1989).Author Institution: Department of Chemistry, University of FloridaElectron-spin-resonance spectroscopy of an argon matrix at 4K containing laser-vaporized niobium indicates that $Nb_{2}{^{+}}$ has been trapped and has a $^{2}\Sigma$ ground state. Evidence for this assignment is provided by a nineteen line pattern with a 80(3) MHz spacing at $g_{i} = 1.85(1)$ produced by hyperfine interaction with two equivalent $^{93}Nb (I = 9/2)$ nuclei. From neutral $Nb_{2}$ $calculations,^{1}$ this state would then be ascribed to a $5s\sigma_{g}{^{2}} 4d\sigma_{g}{^{1}} 4d\pi^{4} 4d\delta^{2}$ configuration, where multiple bonding is $extensive.^{2}