Resonance Raman excitation profile for uranyl acetate in dimethyl sulfoxide

Abstract

The intensity of Raman lines of uranyl acetate/UO 2(CH 3COO) 2 in dimethyl sulfoxide has been measured as a function of excitation energy in the region of the Laport-forbidden f–f electronic transitions, using ten output lines of an argon-ion laser. The resonance Raman excitation profile of the totally symmetric stretching vibration of the uranyl observed at 829 cm −1 shows vibrational fine structure, which resembles the vibronic structure of the electronic absorption spectrum but does not completely coincide. Experimental excitation profile is compared to that calculated using transform theory with parameters derived from the observed absorption spectrum of the resonant electronic state of interest. The non-Condon model (generalized B, C-term source of scattering) gives relatively good agreement with experimental results. The disagreement between the experimental data and the calculated resonance Raman excitation profile may be ascribed to interference between the weak scattering from the neighboring forbidden electronic states and strong preresonance scattering from allowed electronic states at higher level. The change in the UO equilibrium bond length resulting from the 1Σ + g→ 1Φ g electronic transition is found to be 0.068 Å.