THE LOW-LYING ELECTRONIC STATES OF URANIUM MONOXIDE

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1992

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Ohio State University

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Electronic states of UO belonging to the $U^{2+}$ $(5f^{2}7s)O^{2-}$ and $U^{2+}(5f^{2}7s^{2})O^{2-}$ configurations have been identified in absorption and wavelength-resolved fluorescence spectra. The energy spacings among the observed levels have been used to develop a semi-empirical ligand field model of the low-lying states. To fit the model to levels of the $5f^{3}$7s configuration, two parameters were varied: the exchange interaction between the outer 7s and 5f core electrons, and the ligand field parameter $B^{2}_{0}$. The effects of higher order terms $(B^{4}_{0}$ and $B^{6}_{0}$) in the point charge expansion were significantly smaller than those of the leading quadrupolar term $(B^{2}_{0})$. They were included by maintaining the $B^k_{0}$$/B^{2}_{0}$ k=4,6 ratios at the values calculated from Hartree-Fock radial wavefunctions. The remaining nineteen model parameters were held at the values for the $U^{3+}$$(5f^{3}$)ion[1]. Predictions of the ligand field calculations are being tested in a series of wavelength-resolved fluorescence measurements. A CW ring dye laser is used to excite fluorescence from various states of gas phase UO. The emission is resolved by a 0.64m monochromator. High concentrations of UO vapor are obtained by heating samples of the oxidized metal to temperatures around 2400k in a resistively heated tube furnace. Fluorescence spectra and details of the ligand field calculations will be presented.

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1. H. M. Crosswhite, H. Crosswhite, W. T. Carnell, and A. P. Paszek, J. Chem. Phys. 72, 5103 (1980).
Author Institution: Department of Chemistry, Emory University

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