Band 39, Heft 6

The thallium-heavy noble gas potentials and absorption oscillator strengths as a function of internuclear separation have been recalculated using a somewhat modified Baylis' model for the electronic interaction between the atoms. The calculated potentials associated with the 6 2 P 1/2 , 6 2 P 3/2 and 7 2 S 1/2 thallium states are compared to the potentials determined by Cheron et al. from the measurement of continuum emission intensities on the extreme wings of the TI resonance lines due to noble gas perturbers. The shift and broadening coefficients for the 3776 and 5350 Å lines of thallium perturbed by noble gases have also been estimated from the present potentials. The agreement with the experiment is quite good. Moreover, the very strong emission TIXe band centered at approximately 6000, 4300 and 3650 Å, as observed experimentally, can be predicted by the calculated potentials as well.

The present work is an attempt to treat hydrogen storage in metals with the aid of field theoretical methods. Starting with the many-body Schrödinger equation, an adiabatic decomposition yields an electronic system, a protonic system and a host lattice system. We define a storage energy consisting of a lattice contribution and an electronic part. The latter one will be evaluated by The New Tamm-Dancoff (NTD) procedure. This formalism is a method to compute differences of eigenvalues in quantum mechanical problems. As an example we derive a one-particle equation describing a single hydrogen atom in a metal crystal.

The orientational correlation functions in the isotropic phase of nematics are calculated starting from the expression of De Gennes for the free energy density of this phase.

Using the ECR-technique the capture of thermal-energy free electrons was investigated by the molecules HNO 3 and ClNO 3 . The following rate constants at room temperature were obtained: k(HNO 3 ) =(1.4 ±0.7)· 10 -8 cm 3 sec -1 ; k (ClNO 3 ) = (3.9 ± 1.2)· 10 -9 cm 3 sec -1 . An apparent activation energy of AE = (1.6 ± 0.5) kcal · mol -1 was found for the reaction with ClNO 3 . From the energy dependences of the both reactions together with thermodynamic considerations it is suggested that electron capture by ClNO 3 occurs via dissociative attachment whereas with HNO 3 a negative parent ion can be formed. Strong similarity is pointed out to exist between HONO 2 and ClONO 2 towards capture of electrons and the reaction with O 2 - respectively.

Spin-lattice relaxation times (T 1 ) of protons in polycrystalline dimethyl sulfone, stearic acid, stearyl alcohol, trimethylamine-N-oxide, tertiary-butylhydrazine hydrochloride and tertiary-butyl carbamate have been measured over a range of temperatures by pulsed proton magnetic resonance. Except for tertiary-butyl carbamate a single minimum in T 1 was observed for all the compounds. The T 1 results have been interpreted by considering the methyl group reorientations about the C 3 axis and the role of the spin diffusion of the other protons to the methyl protons in the compounds. The double minima in T 1 for tertiary-butyl carbamate have been attributed to reorientations of methyl groups in the tertiary-butyl group about the C 3 ′ axis and reorientations of each methyl group about its C 3 axis. The spin-lattice relaxation parameters have been determined.

The simple relations between the Stark broadening parameters and the ionization potential derived by Purić et al. [1] are discussed, and attention is drawn to the serious limitations for their application. The periodic dependence of the Stark width and shift on nuclear charge number obtained by the same authors [2] is also explained.

The phosphorescence spectra, mean lifetimes of phosphorescence and ratios of phosphorescence/ fluorescence quantum yields have been measured for 5-phenyltetrazole and its three methyl derivatives in a polyvinyl alcohol film over the temperature range of (77-250) K. Temperature responses of the non-radiative intersystem crossing constant. K ST , and the non-radiative triplet state deactivation constant, k m , have been investigated on the basis of these measurements. The energy of activation for the non-radiative transitions has been determined. With the methyl 5-phenyltetrazoles, the thermal deactivation of the triplet state, contrary to the intersystem crossing, has been found to be influenced by the position of the methyl substituent in the phenyl ring.

The rotational spectrum of ethyl formate has been investigated up to 240 GHz. High J transitions of both a-type and b-type have been measured for the two isomers and fitted to a centrifugally distorted Hamiltonian including some sextic coefficients. The results of the analysis are sufficiently accurate for the prediction of all strong transitions throughout the millimeterwave range. No splitting due to the internal rotation of the methyl group was observed, which indicates that the barrier to internal rotation is of the order of 3 kcal/mole or greater.

In order to separate diffusion induced changes in the electrical resistivity of quench-condensed amorphous AgCu alloy films from such arising from other causes several trial experiments have been performed. Such films consisting of alternating Ag 60 Cu 40 /Ag 40 Cu 60 layers showed a specific resistance rise which revealed the following peculiarities: 1. The duration of this increase is inversly proportional to the square of the individual Ag 60 Cu 40 /Ag 40 Cu 60 couple thickness, 2. The increase is suppressed if rapid heating up to the crystallization temperature is performed and 3. It is not appearing in homogeneous layers. These results give clear evidence that the observed effect is arising from diffusional intermixing only. Diffusion coefficients averaged over the annealing period are estimated as D = 8.7 x 10 -15 cm 2 s -1 x exp 0.89 eV/kT.

We analyse Deuling's problem both in the one constant approximation and in the general case. An explicit expression is found for the electric field threshold vs. the crossed applied magnetic field, in the strong anchoring hypothesis.

We analyse the Freedericksz transition and the flexoelectric deformation in a hybrid aligned nematic liquid crystal cell. We show that the threshold field for the first effect is smaller than that for a homogeneous sample. The calculations are made in the one constant approximation and in the general situation. Furthermore, in the adiabatic approximation we calculated the polarization plane rotation vs. the applied magnetic field, in the one constant approximation. A similar calculation is made for the flexoelectric effect. In particular we show that it is possible to extend the analysis to a situation of weak anchoring energy.

The dependence upon ion mass of the loss of translational energy suffered by an ion with kiloelectron volt energy as a result of collision with helium has been investigated over the mass range 400 u to 1600 u. At masses below about 1500 u and an incident ion energy of 8 keV, there is forward-scattering in the centre-of-mass frame: at mass 1620 u at the same energy, there is backscattering in the centre-of-mass frame. The uptake of internal energy by an ion is at a maximum in the region in which the change from forward-scattering to back-scattering occurs.

Recently we reported the results of semiempirical calculations (MNDO, MINDO/3) which led us to the conclusion, that the proton-affinity of molecules R-NH 2 (R = H, CH 3 , C 2 H 5 , n-C 3 H 7 and n-C 4 H 9 ) is determined by the ability of the groups R to carry positive charge in the corresponding cations R-NH 3 + . We did extend our investigations concerning the protonaffinities of primary aliphatic amines including NH 3 and performed ab initio calculations with an STO-3G basis. The results qualitatively parallel those obtained by the semiempirical methods mentioned above. In contrast to the semiempirical results we found that there is a satisfactory correlation between the Mulliken-charges of the nitrogen-atoms and of the NH 2 -groups and the experimental protonaffinities if NH 3 is excluded.

The non-random two-liquid (NRTL) theory developed by Renon and Prausnitz has been used to calculate the concentration fluctuations in liquid Na-Cs alloys. The agreement with experiment is better than with other theories used previously.

The solubiltiy of silver bromate, the Gibbs transfer energy of Ag + and BrO 3 - and the solvent transport number in methanol-dimethyl sulfoxide mixtures are reported. The solubility of silver bromate increases with addition of DMSO. The Gibbs energy of transfer of the silver ion (based on the ferrocene reference method) decreases, while that of the bromate ion becomes slightly negative with the addition of DMSO. The solvent transport number A passes through a maximum (⊿ = 1.0 at X DMSO = 0.65. From these results, it is concluded that the silver ion is preferentially solvated by DMSO whereas the bromate ion shows no preferential solvation.

Inverse methods are applied to the nuclear bound-state problem. Considering only the self-interactions of these states analytical solutions results for potentials and densities. The simplest possible approximation to the full expression yields immediately ⊿R 0i 2 ≡ 〈r 2 (A i )〉 - 〈r 2 (A 0 )〉 ~ - [B (A i ) - B (A 0 )] for the differences in the squared nuclear radii as functions of the respective binding energies per nucleon, B (A i ).