LASER SPECTROSCOPY OF LOW-LYING EXCITED STATES OF CeO: LINKAGE OF 15 STATES OF THE 4f6s CONFIGURATION WITH $0.03 cm^{-1}$ ACCURACY

$^{1}$ C. Linton, M. Dulick, R. W. Field, P. Carette, P. C. Leyland, and R. F. barrow, J. Mol. Spectrosc. 102, 441 (1983). $^{2}$. R. W. Field, Ber. Bunsenges. Phys. Chem. 86 771 (1982).Author Institution: Department of Chemistry, Emory UniversityIn a previous study, Limon $et al.^{1}$ succeeded in locating all of the sixteen states arising from the $Ce^{2+}(4f6s)O^{2-}$ configuration. Most of the electronic term energies were established with an accuracy of $\pm$$3 cm^{-1}$. In many cases the $\Omega$ assignments were based on relative P/Q/R branch intensities, which can be misleading. Accurate rotational and centrifugal distortion constants were obtained for seven of the low-lying states. Approximate rotational constants were given for another seven states. Our recent measurements have provided term energies for fifteen of the $Ce^{2+}(4f6s)O^{2-}$ states with an accuracy of $\pm$$0.03 cm^{-1}$. $\Omega$ assignments were unambiguously determined from observations of the first line in each branch. Improved rotational and centrifugal distortion constants were obtained for eight levels. Previously unresolved $\Omega$-doublings of three low-lying $\Omega$=1 states have been characterized. We have also observed the Q-branch of a nove $l 0^{-}-0^{+}$ transition which gains intensity through mixing between $\Omega$=$U_{1}0^{+}$ and $V_{2}1$ states. Overall, the results confirm the validity of the ligand field $model^{2}$ used to predict the energy ordering of lanthanide oxides