LASER RAMAN-SPECTROSCOPY OF SOME URANYL TRINITRATE COMPLEXES (MUO(2)(NO3)(3) M=CS, RB, K, NH4)

The laser Raman spectra of four uranyl trinitrate complexes (MUO(2)(NO 3)(3); M = Cs, Rb, K, NH4) are recorded in the region from 2000 to 10 cm(-1) by using the lambda = 514.5 (Ar+), 528.7 (Ar+), and 632.8 nm (H e-Ne) laser excitation lines. Their vibrational assignments are made o n the assumption that all the complexes contain discrete UO(2)X(3)(-)( X = NO3) ions belong to a point group of D-3h. In order to support suc h assignments, normal coordinate analyses of the skeletal vibrations a re carried out on the basis of a modified valence force field includin g the bond-bond angle-angle interactions. Approximate stretching and b ending force constants of the U-O and U-X bonds in the UO(2)X(3)(-), a nion are obtained with additional force constants of opposite U-O bond -bond, adjacent U-X bond-bond and angle-angle interactions. Apart from lambda = 632.8 nm, for lambda = 514.5 and 528.7 nm, the resonance Ram an scattering is observed for each complex. It is found that, as reson ance is approached, the uranyl symmetric stretching vibration at c. 88 0 cm(-1) is conspicuously enhanced in comparison with the NO3- vibrati on at c. 1025 cm(-1).