Spectroscopic and theoretical investigations of UF and UF+.

Laser induced fluorescence and resonantly enhanced multiphoton ionization spectra were recorded for UF in the 18,000-20,000 cm(-1) range. Rotationally resolved data were obtained, and the analysis of a band at 18624 cm(-1) yielded a ground state rotational constant of 0.2348 cm(-1). The electronic ground state was clearly identified as |Ω| = 4.5, confirming the theoretically predicted U(+)(5f(3)7s(2))F(-) configuration. Dispersed fluorescence spectra revealed low-lying electronic states that are assigned as |Ω| = 3.5 (435 cm(-1)) and 2.5 (650 cm(-1)). Two-color photoionization spectroscopy was used to study UF(+). The ground state and fifteen electronically excited states have been characterized. The ground state was found to be |Ω| = 4, as it is for the isoelectronic molecule UO, and with vibrational constants of ωe = 649.92 and ωexe = 1.83 cm(-1). The patterns of electronically excited states observed for UF(+), with |Ω| values ranging from 0 to 6, were qualitatively consistent with the predictions of a ligand field theory model developed for UO. The experimental data for both UF and UF(+) were reasonably well reproduced by CASSCF/CASPT2 electronic structure calculations that included spin-orbit coupling.

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