Knowledge Bank

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 $\omega e=521\pm 1.0cm-1$ and $\omega eXe=7.3\pm 10cm-1$. The anion displays a lower fundamental vibrational frequency of $405\pm 15cm-1$. A comparison of these results with those available for $V2$ and $Cr2$ indicate that VCr has a $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Delta$ 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 $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Delta$ ground state with the extra electron occupying a $\sigma u$ orbital. Somewhat suprisingly in view of our previous negative ion photoelectron studies of $Cr2$ and $V2$, we observe a strong transition to a low lying excited state of VCr at $4485\pm 15cm-1$ whose vibrational frequency $(\omega e=720\pm 20cm-1,\omega eXe=13\pm 4cm-1)$ 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.