NEGATIVE ION PHOTOELECTRON SPECTROSCOPY OF VCr
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Date
1995
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Ohio State University
Abstract
The 488 nm photoelectron spectrum of the $VCr^{-}$ anion shows vibrationally resolved transitions to the ground state and to four excited electronic states of neutral VCr. The ground state transition yields an electron affinity of $0.523 \pm 0.005$ eV for VCr, and displays a long vibrational progression with a non-Franck Condon intensity profile. Observed vibrational levels in the VCr ground state up to $\nu = 9$ fit a Morse potential with $\omega_{e} = 521 \pm 1.0 cm^{-1}$ and $\omega_{e}X_{e} = 7.3\pm 10 cm^{-1}$. The anion displays a lower fundamental vibrational frequency of $405 \pm 15 cm^{-1}$. A comparison of these results with those available for $V_{2}$ and $Cr_{2}$ indicate that VCr has a ${^{2}}\Delta$ ground state with a $(d\pi)^{4}(ds\sigma)^{2}(sd\sigma)^{2}(d\delta)^{3}$ electron configuration, and that the $VCr^{-}$ anion has a ${^{3}}\Delta$ ground state with the extra electron occupying a $\sigma_{u}$ orbital. Somewhat suprisingly in view of our previous negative ion photoelectron studies of $Cr_{2}$ and $V_{2}$, we observe a strong transition to a low lying excited state of VCr at $4485 \pm 15 cm^{-1}$ whose vibrational frequency $(\omega_{e} = 720 \pm 20 cm^{-1}, \omega_{e}X_{e} = 13 \pm 4 cm^{-1})$ considerably exceeds that of the ground state. Additional transitions to three higher states of VCr, and from two excited states of $VCr^{-}$, will also be discussed.
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Author Institution: University of Minnesota, Minneapolis MN 55455