Volume 30, Issue 3

The reliability of the resonating group method is studied above the three-body breakup threshold. In particular, the real part of the elastic n-d phase shift is calculated in a model of three spinless bosons interacting by a separable Yamaguchi potential for which exact Faddeev results are available. Spurious singularities which are caused by the distortion part of the resonating group ansatz are eliminated by a least squares method.

The energies of the γ-rays from radioactive decay of 51 Cr, 169 Yb, 170 Tm, 192 Ir and 203 Hg have been measured relative to the 411.794 keV standard from the decay of 198 Au with relative accuracies between 4 × 10 -7 and 4 × 10 -6 .

The delayed fluorescence of naphthalene crystals doped with anthracene has been investigated for concentrations between 7 × 10 -9 and 10 -5 mol/mol in the temperature range 4.2 -300 °K. The concentration dependence of both the quantum ratio of host and guest emission and of the lifetime shows the effectivity of energy transfer by triplet excitons. It can be described quantitatively within the statistical hopping model, which includes the probability for an exciton to visit the same host molecules repetitively before becoming trapped. This incoherent energy transport becomes faster as the temperature is lowered. The exciton hopping time decreases monotonically from t ʜ = 2 × 10 -10 sec at 300 °K to t ʜ = 8 × 10 -11 sec at 130 °K. Below 100 °K the delayed fluorescence is governed by competing trapping effects.

A variation of the temperature changes the static dielectric constant (ε) and the refractive index (n) of solvents and, in conjunction with the measurement of solvent shifts of absorption and fluorescence maxima, allows the investigation of dipole moment changes of solutes in the excited state. For this purpose, investigations of the temperature dependences of ε and n of some pure and mixed solvents of different polarities have been made. It is found that the excited dipole moments of indole, 1,2-dimethylindole, 2,3-dimethylindole and tryptophan obtained from the shifts of the fluorescence maxima in mixed solvents at high temperatures are in good agreement with those obtained in other ways.

It is pointed out that from the measured principal g values in single crystals of bis (diethyldiselenocarbamate) copper (II) it is possible to deduce the g values for the single molecular unit. By a reasonable choice of its principal directions it turns out that the g tensor is axial along the bisecting line of the major angle between the Cu-Se bonds, with g ∥ ∼ 2.05 and g ⊥ ∼ 2.01. These values seem to confirm the presence, also in the pure Cu crystals, of the main g anomaly, recently observed in the Cu : Ni diluted crystals. Therefore, one can infer that the anomaly is essentially due to the nature of the Cu-Se bonds and not to distortions produced by the Ni diamagnetic matrix.

The molecular structures of Cl 3 V = NCl and Cl 3 V = O were determined by gas-phase electron diffraction. For both molecules the r α 0 -structure was converted to restructure. In the case of Cl 3 V=O the necessary corrections were taken from the literature while for Cl 3 V=NCl an approximate force field was evaluated from the infrared spectra of the solid compound for calculating these corrections. The following rα 0 parameters were derived for Cl 3 V = NCl: V = N = 1,651 (6), N-Cl = 1,597 (8), V - Cl = 2,138 (2), ⦓ ClVCl = 113,4° (0,3) and ⦓ VNCl = 169,7° (4,2). The most interesting result of this investigation is the structure of the V = N -Cl group which is almost linear and has a very short N -CI bond distance. Concerning the VNCl group the gas-phase results agree very well with the crystal structure. For vanadyl chloride the following rα 0 -values were obtained: V = 0 = 1,571 (4), V - Cl = 2,137 (1) and ⦓ ClVCl = 111,0° (0,1°). The error limits given in thousandth parts of an Angstrom or degrees are the threefold standard deviations of the least squares analysis.

The kinetics of the solid state reactions AgI + TiI → AgTlI 2 (I) Agl + AgTl 2 I 3 → 2 AgTlI 2 (II) AgTlI 2 + Til → AgTl 2 I 3 (III) are investigated with reactant pellets by the contact method. With the aid of inert marker experiments and transport number determinations it was possible to state that the governing mechanism is the cation counter-diffusion in all cases and that the rate determining step is the diffusion of Tl + . The experimental reaction rate constants agree reasonably with those calculated on the basis of the Wagner's thermodynamic theory.

The results of a factor group analysis, the symmetry coordinates and vibrational modes of the lattice vibrations of compounds crystallizing in NiAs structure respectively NiAs defect structure (Fe 3 Se 4 type) are presented. A normal coordinate treatment of the NiAs structure is performed using the GF-matrix-method assuming a valence force field with 3 force constants.

The specific electric conductivity of molten HgI 2 -HgBr 2 and HgI 2 -SbI 3 binary mixtures was measured as a function of composition and temperature in the ranges 220 - 540 °C and 180 to 540 °C, respectively. In the HgI 2 -HgBr 2 system negative deviations from additivity are found in mixtures rich in HgBr 2 , and positive ones in those rich in HgI 2 . The positive deviations are more pronounced at higher temperatures. In the HgI 2 -SbI 3 system the deviations from additivity are negative throughout.

The effect of temperature and concentration of the added electrolyte tetrabutylammoniumpicrate on the electric conductivity of homologous 4,4′-di-n-alkoxyazoxybenzenes (C 1 to C 8 ) in their nematic phase is investigated. In general an increase of the alkyl chain length results in a decrease of the ratio of anisotropy x ∥ /x ⊥ . At the lowest temperature of the nematic phase values between 1,6 (C 2 ) and 0,45 (C 8 ) are obtained. This behaviour can be explained by the formation of cybotactic groups with a smectic structure. Increasing the electrolyte concentration reduces the ratio of anisotropy for short alkyl chains, whereas for long chains the ratio rapidly increases.

The resonance absorption method is described for detecting ppm concentrations of NO mixed with other gases. As source lamp for the emission of the NO γ system, A 2 ∑ + - X 2 ∏, a hollow cathode discharge has been used operating in streaming air at low discharge current (∼). NO detection is achieved by a double-beam technique with single-beam optics. The experimental average absorption coefficient obtained for the γ (0,0) band is compared with the calculated value. Relevant NO spectroscopic information is reported.

The mass spectra and the ion molecule reactions of methylphosphine, dimethylphosphine and dimethyldeuterophosphine have been studied by ion cyclotron resonance spectrometry. About 50 ion molecule reaction are observed for each compound. The product ions can be classified as ions with two phosphorus atoms: P 2 R 5 + , P 2 R 3 + , P 2 R 2 + and P 2 R + (R = CH 3 or H), as phosphonium and phosphinium ions and ions resulting from collision dissociations and charge exchange reactions. Tertiary ions with three phosphorus atoms like CH 3 P 3 H 2 + (from CH 3 PH 2 ) and (CH 3 ) 4 P 3 H 2 (from (CH 3 ) 2 PH) have also been detected. The mechanisms of the ion molecule reactions, rearrangements, P -H- and C-H-reactivities and product ion structures are discussed, using in the case of dimethylphosphine the results obtained with the deuterated compound. Rate constants of formation of the more abundant product ions from the molecular ion and the CH 3 P + ion, both odd electron particles, have been determined. The reactions with dimethylphosphine have much smaller rate constants than the reactions with methylphosphine.

Ionisation- and appearance potentials of some dialkylsulfoxides and their major fragment ions were determined. In addition to the determination of dissociation energies in the ions and heats of formation of the ions and ionic fragments, a value of 66 kcal/mole for the C-S dissociation energy in neutral dialkyl sulfoxides was obtained.

The appearance potentials for a large number of organosilicon ions have been measured. Combination of these values with thermochemical heats of combustion allow the determination of bond energy terms which may be used to calculate heats of formation for all silicon compounds containing hydrogen, alkyl and chlorine ligands. The bond dissoziation energies D(Si - H)= 89 ± 4, D(Si - C) = 85 ± 4 and D (Si - Si) =75 ± 8 kcal/Mol were found to be independent of the number of methylgroups attached to silicon. In addition the Si - Cl bond energy was found to be 116 and 104 kcal/Mol in (CH 3 ) 3 SiCl and Cl 3 SiCl respectively.

Relative Q-values for (d, p) and (d, t) reactions on all even-A tin isotopes have been determined by simultaneous detection in nuclear emulsions placed in the focal plane of a magnetic spectrograph of the particle groups corresponding to the ground state transitions. The results when combined to other input data for the atomic mass tables provide more accurate mass excesses for nuclides in this mass region.

The spin locking method known from NMR is shown to be useful also in ESR for investigating spin lattice relaxation problems and “slow” motions, e. g. questions of energy transfer by triplet states in organic molecular crystals, and probing of nuclear quadrupolar splittings even smaller than the ESR line width at zero magnetic field. Optically detected ESR spin locking experiments for isolated triplet states in zero field are demonstrated. It is shown how the complication of incoming and decaying triplet states and relaxation between all three triplet sublevels has to be handled during spin locking. An application, the study of the cross-relaxation between electronic triplet spin states and deuteron or proton spins is presented. These experiments are possible in spite of the first order quenching of the hyperfine coupling in zero magnetic field. Another application is briefly mentioned, in which the adiabatically demagnetized state in the rotating frame is used to probe the electronic triplet state transfer and nuclear spin lattice relaxation.

The noise of the laser signal of the cataphoretic He-Cd-Laser (441,6 nm) and the spontaneous emission are investigated spectroscopically in end on and side on observation as function of Cd and He atom density. Commencing with Cd atom densities of 5 · 10 14 cm -3 witish and blue striations of the positive column develop, that are directly connected with a sinoidal modulation of the voltage and the Cd, Cd + , and He emission. Electron temperature and Cd + density are higher in the whitish zones than in the blue zones. The noise is attributed to plasma disturbations, for example Cd density fluctuations. The striations are explained on the basis of Wojaczek's theory of electron temperature waves.

Various donor doping of ZnSb is investigated. Te-doping yields the most stable n-type crystals at room temperature; the samples show p-type behaviour at low temperatures. The influence of surface effects is demonstrated. It was possible to prepare n-type ZnSb for the whole temperature range.

The liquid structure factors of sodium and potassium have been calculated by taking a Lennard-Jones 6:12 potential as a perturbation of the hard sphere potential in the mean spherical model approximation. Typical results are in good agreement with the experimental ones.

The compound K 3 Sb 5 O 14 was synthetisized single-phase and examined by means of dielectric spectroscopy from 30 Hz to 10 MHz. Three separate regions of dielectric absorption with broad distributions of relaxation times have been found. Temperature-dependend measurements up to 200 °C yielded enthalpies of activation between 15 and 20 kcal/mole.

The initial thermoelectric power of the molten systems (Cu, Me) Cl and (Cu,Me)Br (Me=Na, K, Rb, Cs) was determined using copper electrodes. The results are compared with previous results obtained from the systems (Cu, Me) I and (Ag, Me)X (X = Cl, Br, I).

Results of measurements of the electric conductivity and of the molar volume for the water-free liquid system formic acid-f-acetic acid are presented. They cover the whole composition range at temperatures between 0 °C and 50 °C. The equivalent conductivity and the activation energy are also given.

Cleaved crystal surfaces of CaF 2 were decorated by means of gold deposited on the crystal surface by vacuum evaporation. The influence of the substrate temperature on the decoration behaviour was studied.