Ken Ohwada

An effective nuclear charge model for the prediction of valence force constants in polyatomic molecules. I

The effective nuclear charges have been defined using the quadratic force constants which are obtained by the application of perturbation theory to homonuclear diatomic molecules. It has been shown that these charges are applicable to the calculation of force constants in heteronuclear diatomic molecules. To make further application of the effective nuclear charges to polyatomic molecules, we have proposed effective intramolecular potential functions founded on the electrostatic theorem, and have attempted to predict the force constants of triatomic molecules. The results show that our method of approach using the effective nuclear charges is useful for the prediction of approximate valence force constants in polyatomic molecules.

The application of an effective nuclear charge model to the prediction of valence force constants in planar and pyramidal XY3 molecules. II.

The valence force constants of planar and pyramidal XY3 molecules are calculated on the basis of the effective nuclear charge model previously developed. The calculated results are compared with the experimental force constants which are determined by the normal coordinate analysis. The agreement between the calculated and experimental force constants is moderately good for most molecules under investigation. This implies that the effective nuclear charge model is useful for the prediction of approximate valence force constants in more complicated polyatomic molecules.

The application of an effective nuclear charge model to the prediction of valence force constants in tetrahedral XY4 molecules. III

With the use of effective nuclear charges defined from the quadratic force constants of homonuclear diatomic molecules, calculations of valence force constants for tetrahedral XY4 molecules are carried out illustrating the effective nuclear charge model previously developed. The calculated results are compared with the experimental force constants which are determined by the normal coordinate analysis. The agreement between the calculated and experimental force constants is moderately good for most molecules under investigation. This suggests that the effective nuclear charge model is useful for the prediction of approximate valence force constants in more complicated polyatomic molecules.

Uranium-fluorine lattice vibration of uranyl fluoride

Abstract I.R. spectrum of uranyl fluoride, UO2F2, has been measured in the frequency region from 4000 cm−1 to 380 cm−1. A normal coordinate analysis of the optically active UO and UF lattice vibrations has been made on the basis of a layer model of infinite [(UO2)F2]∞. Based on the results of this treatment, some of the observed bands have been assigned to the UO and UF lattice vibrations. The stretching and repulsive force constants have been obtained and discussed. I.R. spectrum of neptunyl fluoride, NpO2F2, has also been investigated in the same viewpoint as above interpreted.

Uranium-oxygen lattice vibrations of triuranium octoxide

Abstract A tentative assignment of the i.r. spectrum for triuranium octoxide has been made by assuming two structure models of infinite hexagonal UO 3 and UO 2 . It has been found that all the i.r. absorption bands previously observed in the region from 4000 to 90 cm −1 are well explained by the assumption of such models. In order to obtain the approximate force constants of the uranium-oxygen bonds in triuranium octoxide, the normal coordinate analysis of the optically active U-O lattice vibrations has been made on the basis of the two models. The force constants of U-O bonds have been obtained and discussed in some detail.

RAMAN SPECTROSCOPIC STUDIES OF SOME URANYL NITRATE COMPLEXES

Abstract Laser Raman spectra of uranyl trinitrate complexes (KUO2(NO3)3, RbUO2(NO3)3, CsUO2(NO3)3, NH4UO2(NO3)3) have been measured in the region from 2000 cm−1 to 10 cm−1. Vibrational assignments have been made on the assumption that all the complexes contain discrete UO2X3 − (X = NO3) ions belonging to a point group of D3h. A brief discussion is made on the ligation effect of nitrate group on the uranyl bond order from a point of view of molecular orbital theory.

Uranium-oxygen lattice vibrations of lithium, β-sodium and β-strontium uranates

Abstract I.R. spectra of Li 2 UO 4 , β-Na 2 UO 4 , and β-SrUO 4 have been measured in the region from 4000 cm −1 to 380 cm −1 . A normal coordinate analysis of the optically active U-O lattice vibrations of such compounds has been made on the basis of a simple layer model of infinite [(UO 2 )O 2 ] ∞ . Based on the results of this treatment, some of the observed bands have been assigned to the U-O lattice vibrations. The force constants of U-O bonds and angles have been obtained and discussed.

IR spectroscopic studies of some uranyl tetrachloride complexes

Abstract The IR spectra of dipotassium, dirubidium and diammonium uranyl tetrachloride hydrates (K 2 UO 2 Cl 4 ·3H 2 O, Rb 2 UO 2 Cl 4 ·H 2 O, (NH 4 ) 2 UO 2 Cl 4 ·4H 2 O) have been measured in the region from 4000 down to 30 cm −1 . A normal coordinate analysis of the (UO 2 Cl 4 ) 2− ion apart from the K + , Rb + and NH 4 + ions has been made using Wilsons FG matrix method. The force constants associated with the UO and UCl bonds have been obtained on the basis of both the force models of modified Urey-Bradley and valence force fields. An effort has been directed towards the understanding of the uranyl bond weakening with coordination of the ligands. It has been suggested that this bond weakening is caused by charge transfer from the ligands to the uranium atom.

Chemical Degradation of Kerosene Diluent with Nitric Acid

Chemical degradation of kerosene diluent with nitric, acid was studied to clarify its effect on uranium distribution ratio and fission product retention in the presence of degradation products. The decontamination of fission products retained in degraded kerosene was also investigated. From the results of infrared spectrometry, it was recognized that nitro compounds, carboxylic acids, nitrate esters and nitroso compounds were formed as the main degradation products. The uranium distribution ratio in the extraction with TBP/degraded kerosene decreased with increasing concentration of nitric acid above 5 N, with rising temperature, and with increasing concentration of olefinic and aromatic hydrocarbons in the kerosene. It is suggested that the decrease of uranium distribution ratio may be due to the formation of carboxylic acids caused by the kerosene degradation. Some fission products, in particular 95Zr-95Nb and 131I, were retained in the organic phase, but 106Ru-106Rh did not remain after scrubbing with ...

Excitation Profile of the Resonance Raman Effect of Uranyl Nitrate in Dimethyl Sulfoxide

The resonance Raman spectra of uranyl nitrate in dimethyl sulfoxide (DMSO) were measured at room temperature, with the use of ten output lines (528.7, 514.5, 501.7, 496.5, 488.0, 476.5, 472.7, 465.8, 457.9, and 454.5 nm) of an argon-ion laser. The excitation profile of the resonance Raman effect has been obtained by plotting the relative intensities of the uranyl symmetric stretching vibration at 835 cm−1 against the laser exciting wavelengths. It has been found that the observed excitation profile of the uranyl symmetric stretching vibration resembles the vibronic structure of the electronic absorption spectrum. Also, the excitation profile obtained is briefly discussed in relation to the theory developed by J. Tang and A. C. Albrecht.