ROTATIONALLY RESOLVED ELECTRONIC SPECTRA FOR URANIUM MONOXIDE

Author Institution: Department of Chemistry, Illinois Institute of Technology; Chemistry Division, Argonne National LaboratoryPrevious attempts to observe the electronic band systems of uranium monoxide (UO) have been hindered by overlapping spectra which arise from the large number of polymeric oxides that coexist with vapor phase UO. We have overcome these problems by the use of sequential muliphoton ionization of a molecular beam of UO, followed by mass selected ion detection. Several vibronic bands of UO have now been observed by this technique. Spectra were recorded by tuning a pulsed dye laser through the single photon resonances, and ionizing the excited molecules with pulses from a XeCl laser. A time of flight mass spectrometer was used to ensure that only $UO^{+}$ ions were detected. Rotationally resolved bands were recorded in the region between 560-600 nm. Many of the bands showed a simple P, Q and R branch structure with $B^{\prime}=B^{\prime \prime} =0.333^{\circ} 0.004 cm^{-1}$. Rotational lines with $J^{\prime \prime} \leq 3$ were not seen indicating that $\Omega= 4$ for the lower state. Further analytical and experimental work is in progress on these spectra, and a summary of the results will be presented