THE LOW-LYING STATES OF THE URANIUM MONOXIDE (UO) MOLECULE

$^{1}$ L.A. Kaledin, A.N. Kulikov, A.I. Kobylyanskii, et al. Russ. [Phys. Chem. 61, 712, (1987). $^{2}$ R.W. Field Ber. Bunsenges. Phys. Chem. 86, 771 (1982).""Author Institution: High Temperature Institute of the USSR, Academy of SciencesRecent work on the UO molecule in the gas $phase^{1}$has led to the determination of the energies of five low-lying electronic states. Allowance for the stabilization of the outer 7s urbitals in relation to the inner 5f and 6d orbitals by the $O^{2-}$ ligand field according to Field’s $method^{2}$ shows that the lowest and first excited configurations of the bound ion in the $U^{2}+O^{2}$system are $5f^{3}7s$ (configuration 1) and $5f^{2}7s^{2}$ (configuration II), respectively. In the fit procedure for the $5f^{3}7s$ configuration, there were three variable parameters: the exchange interaction $G_{3}(=450 cm^{-1})$ between the outer 7s and 5f core electrons and two crystal field parameters $B^{2}(6000 cm^{-1})$ and $B^{4}(1500 cm^{-1})$. $B^{6}$ was held fixed at 0 $cm^{-1}$. The spin-orbit interaction parameter $\zeta$ was set equal to the value for $U^{-}$ in the $5f^{3}7s^{2}$ configuration: $\zeta =2100$ $cm^{-1}$. The energies for the $5f^{2}7s^{2}$ configuration (II) were calculated using the same values of the parameters as derived for the $5f^{3}7s(I)$ configuration. [FIGURE] This table summarizes our results (in $cm^{-1}$)for the states of UO with energies less than 8000 $cm^{-1}$, [$^{*}$Energy of (2) 4 state fixed at observed value