Knowledge Bank

Wavelength-resolved fluorescence excitation techniques have been used to record thirty-three electronic transitions of UO at a resolution of $0.03cm-1$. Nine low-lying electronic states that correlate with $U2+(5f37s)O2-$ and $U2+(5f27s2)O2-$ were characterized. With few exceptions, $\Omega$ assignments were unambiguously determined from observations of the first lines in at least two rotational branches. Deperturbed constants of $\omega e=850.8cm-1$ and $re=1.8378$ {\AA} have been determined for the ground state of the $5f37s$ configuration, and $\omega e=928.6cm-1$ and $re=1.7851$ {\AA} for states of the $5f27s2$ configuration. Fitted values for the ligand field parameters $B02(5f)=10270cm-1,B04(5f)=621cm-1$. and $B06(5f)=173cm-1$ strongly differ from their relativistic Dirac-Fock values: $B02(5f)=24000cm-1,B40(5f)=9000cm-1$, and $B06(5f)=6000cm-1.$ Ligand field theory calculations have been used in an attempt to provide configurational assignments for the excited states of UO. The energies of 23 electronic configurations of UO, and 19 electronic configurations of $UO+$, have been calculated. The density distribution of bound states for UO and $UO+$ up to their ionization limits was also calculated.