Shmuel Weiss

Uniform reduced interaction dipole for all rare gas pairs

A large body of translational absorption spectra of the rare gases was used to evaluate a uniform reduced interaction dipole for all rare gas pairs. This dipole, obtained through the use of realistic intermolecular potentials, was free from artifacts which distorted previous dipoles, obtained from cruder models. Interesting correlations were found between individual dipole strengths and molecular properties. Similarities between the dipole and potential functions were noted.

Collision‐induced spectra of rare gas mixtures: Experimental results and empirical relations

Translational absorption spectra were obtained for He–Kr and He–Xe mixtures at 300 °K and for He–Ar, He–Kr, He–Xe, Ne–Ar, Ne–Kr, and Ne–Xe mixtures at 480 °K. These spectra, as well as other rare gas translational spectra available from the literature, were found to obey a rule of corresponding states when expressed in terms of reduced frequencies and intensities. The peak frequencies and intensities, the half‐widths and spectral moments, were found empirically to vary as simple functions of the temperature and could be correlated quantitatively with molecular properties. On the basis of these correlations the characteristics of as yet unmeasured spectra could be predicted.

Kinetics of some uranyl nitrate-organic phosphate exchange reactions

Abstract The kinetics of the exchange reaction between uranyl nitrate-organic phosphate complex and excess phosphate was studied by NMR line broadening. The organic phosphates were tributyl, dibutyl cresyl and discresyl butyl phosphate. The influence of solvents on rate constants was investigated, the order of the reaction was ascertained and activation energies were determined. Strikingly the activation energy was the same, within experimental accuracy for all three phosphates in all the solvents investigated 9 kcal/mole. Qualitative results were also obtained for the more bulky tri (Hexyl-2 ethyl) phosphate which was found to exchange at a lesser rate than the above mentioned phosphates. The problems arising when it is attempted to use the rate constants of the exchange reaction to estimate the permeability of uranyl nitrate through “solvent membranes” containing the same phosphates are discussed.

Translational spectrum due to ternary collisions in pure rare gases

Abstract A simplified model is used to predict the spectral region in which the translational absorption spectrum due to ternary collisions in a pure monoatomic gas is to be expected and its general shape. Analytical expressions are obtained for the absorption coefficient and for the integrated intensity.

Information on Intermolecular Potentials Obtained from the Temperature Dependence of the ir Absorption Spectrum of Rare Gas Mixtures

The infrared collision‐induced absorption spectra of He–Kr and He–Xe mixtures were measured at 300° and at 620°K. The results were analyzed in terms of models previously suggested by Levine and Birnbaum and by Okada et al. The integrated intensities are found to be strongly temperature dependent. This finding indicates the molecules are actually soft. It is definitely concluded that studies of the temperature dependence of collision‐induced absorption spectra can be used to obtain information on intermolecular potentials (particularly their repulsive part). For the case of He–Kr and He–Xe mixtures it is found that the results support the modified Buckingham exp‐6 potential in preference to the Lennard‐Jones potential.

Translational Spectra Due to Collision‐Induced Overlap Moments in Mixtures of He with CO2, N2, CH4, and C2H6

Enhancement of the absorption, upon addition of He to CO2, N2, CH4, and C2H6, has been observed in the frequency region 200–450 cm−1. It is shown that in this frequency region absorption due to multipole moment induction is weak and particularly so because of the very low polarizability of He. The observed spectra are thus due to induction by overlap forces and similar in origin to spectra observed for rare gas mixtures. The observed spectra are indeed found to resemble those for mixtures of He with rare gases in position and shape as well as in intensity. The spectra are analyzed in terms of a hard sphere potential and an overlap moment varying exponentially with intermolecular separation.

Ligand exchange in uranyl complexes in non-aqueous solutions: Equilibrium properties

Abstract The systems uranyl nitrate, tributylphosphate and 8-hydroxyquinoline or diphenylcarbazone were studied in chloroform, carbon tetrachloride and 1,2-dichloroethane at a number of temperatures. The nature of the complexes formed was determined and the equilibrium constants and several thermodynamic functions were measured. 8-Hydroxyquinoline and diphenylacrbazone will be valuable as indicators for uranyl in kinetic studies. They are also interesting since they participate, along with tributylphosphate, in formation of synergistic complexes.

Experimental interaction dipoles for the rare gases

Interaction dipoles for He–Ar, He–Kr, He–Xe, Ne–Ar, Ne–Kr, Ne–Xe, Ar–Kr, and Ar–Xe were determined by adjusting the parameters of flexible dipole moment functions to reproduce the experimental collision‐induced translational spectra. The present limitations of this approach to interaction dipoles — which to date is the only experimental one available — are discussed.

Dipole moment of interacting rare-gas atoms

Abstract The translational absorption spectra of HeAr and NeAr have been analyzed with a hard-sphere potential to obtain the explicit dependence of the interaction dipoles on interatomic distance. The dipoles were found to consist of a short-range part varying almost exponentially with the distance and of a long-range part which varies more slowly. μ He Ar ( r ) exhibited an unexpected maximum at small distances.

Kinetics of ligand exchange in uranyl complexes in non-aqueous solvents

Abstract Stopped flow and T-jump experiments were carried out to study the kinetics of the reactions leading to the formation of complexes of the forms UPL and UPL2 where U stands for uranyl, P for TBP and L for 8-hydroxyquinoline or diphenylcarbazone. The experimental results, for CCl4 and CH2ClCH2Cl solutions, provided considerable information on the mechanisms of these reactions as well as numerical values for some of the rate constants and activation energies and entropies.