Band 27, Heft 5

Time correlation functions for gases of linear molecules in a static homogeneous magnetic field are derived from the set of transport relaxation equations obtained from the linearized Waldmann-Snider equation. In particular, the complex auto-and cross correlation functions of the friction pressure tensor and the tensor polarization are considered. They are of importance for the viscosity, the depolarized Rayleigh spectrum, and flow birefringence. For the gases HD and CO 2 their real and imaginary parts are plotted as functions of a reduced time and discussed. Lastly, the influence of a constant magnetic field on the flow birefringence property of a gas of linear molecules in a Couette flow arrangement is treated. The principal axes of the dielectric tensor are rotated about the field direction. For two field orientations the respective angles of rotation are determined. The eigenvalues of the dielectric tensor reveal the tendency of the optical and transport properties of the gas to decouple for increasing field strengths

An explicit expression for the circular polarization of gamma rays emitted by odd mass deformed nuclei is given. A semi-microscopic description of the nuclear excited states based on pairing plus quadrupole and octupole model is used. The average field is based on a deformed diffuse edge potential. The short-range correlations are taken into account via the generalized Bethe-Goldstone-equation.

ESR measurements on Fe 3+ and Cr 3+ at interstitial sites in SnO 2 show that two of the magnetic main axes form an angle of 0.7° to the crystallographic axes. Additional information as to which kind of sites are occupied is yielded by ENDOR measurements of the Fe 57 , Cr 53 hyperfine inter-action, and of the superhyperfine interaction with neighbouring Sn-ligands. It is, furthermore, shown that hydrogen is present in the immediate surroundings of both 3d-ions at interstitial sites

Starting from a two-particle equation of the exciton which includes beside the Coulomb inter-action a spin-dependent exchange term the influence of the electron and hole spin on the exciton spectrum is studied by taking into account spin-orbit and spin-spin interaction. A rough estimate of the resulting splitting is given. In a second part the effect of the spin-dependent exchange term in a magnetic field is investigated. The result is that the usual spin splitting for s-states can not be observed

Measurements on the rotational transition J = 0 → 1 of the four isotopic species of GaCl resulted in improved rotational and hyperfine structur constants. 35 Cl: e q ν Q = [-13.20-0.20(ν+1/2) ± 0.15] MHz; 69 Ga: e q ν Q = [-92.40+0.68(ν+1/2) ± 0.14] MHz

Absorption spectra in liquid solution, fluorescence and phosphorescence spectra, phosphores-cence quantum yields, phosphorescence to fluorescence quantum yield ratios, and phosphorescence decay times of 9 chloro substituted biphenyls dissolved in low temperature EPA glass were in-vestigated. The emission spectra of sterically unhindered systems are structured and significantly Stokes-shifted. Ortho substitution shifts the conjugation band in absorption as well as the un-structured fluorescence and phosphorescence bands to shorter wave lengths presumably by pre-venting the system from attaining a planar excited state. Chloro substitution which increases the rate constant of phosphorescence in the order meta < para < ortho, is nearly additive for multiple substituted systems and is correlated to the MO coefficients at the chloro substituted position in the absence of steric hindrance

Die Untersuchung der IR-und Raman-Spektren von (CD 3 ) 3 SiCl und (CD 3 ) 3 SiOSi (CD 3 ) 3 führt zu einer Neuzuordnung der ρCH 3 -Schwingungen in Trimethylsilylverbindungen. In Normalkoordina-tenanalysen an diesen Verbindungen sowie an HSi (OCH 3 ) 3 /HSi (OCD 3 ) 3 , die sich auf die gemes-senen Isotopenverschiebungen stützen, wird das Schwingungsverhalten der Methylgruppen durch die Einbeziehung von ρCH 3 (CD 3 )-Koordinaten angemessener wiedergegeben als durch eine Betrachtung als Punktmassen. Für die vornehmlich interessierenden Valenzkraftkonstanten ergeben sich folgende verbesserte Werte: f(SiCl) 2,84; f(SiO) 4,60 (Hexamethyldisiloxan) bzw. 5,13 mdyn/Å (Tri-methoxysilan) und f(SiC) 2,84-2,89 mdyn/Å

Photoionization has been used to produce ions of N 2 , O 2 . and CO in definite excited states. Deactivating collisions of these ions with molecular gases were described in paper I, where the cross sections of ions with thermal velocity are given for various electronic and vibrational states. By application of an electric field the charged particles are accelerated yielding information on the influence of the kinetic energy of the collision partners on these deactivating collisions. The cross section is found to follow an exponential law σ ~ E -α , with a varying between 0.34 and 0 41 for the different excited stales of the molecular ions. The observations were carried out for a range of kinetic energies from the thermal energy up to 6 eV maximum. This simple exponential law is followed for kinetic energies up to at least 2 eV. At higher energies slight deviations were found to occur

Some comments are made for the generation of e.m. travelling and standing waves used for in-ductive plasma acceleration. Resulting from a simple mathematical formulation the different features lead to a non-conventional method for travelling wave generation, which is compared with the basic method - i. e. the standing wave generation - with regard to Ohmic losses and mag-netic energy density

The modified form of the Rittner's potential function has been tested in it's ability to reproduce the ω e χ e values of alkali halide diatomic molecules. The function has been compared with the original form of Rittner's potential. The comparison of the calculated values of ω e χ e with those obtained experimentally shows that the modified form of the Rittner's potential is better than the original one. The reliability of the test made in the present study has been briefly discussed

The paper represents an analysis of the characteristic properties of spontaneously excited irregu-lar striations observed in the positive column of a glow discharge. Comparisions with the properties of coherent, externally excited, growing ionization waves lead to the conclusion that irregular stria-tions are random ionization waves. Assuming that random striations originate at the cathode end of the positive column, their frequency spectrum can be approximately explained from a knowledge of the dispersion relation of ionization waves. The nonlinear properties of random striations remain to be explained

Te was evaporated in high vacuum (10 -5 Torr) on simultaneously cleavaged alkali halides with rock salt structure. Research on the Te-films was done by transmission electron microscopy. We ob-served characteristic differences in epitaxy quality of the different substances: e. g. NaCl and LiBr showed bad, RbJ and KJ showed exceptionally good epitaxy (exclusively point diffraction pat-terns) . Reproduced experiments showed the same results as simultaneous evaporation. The expected systematic relation to analoguous d-values was however insignificant. It seems to be an "indirect epitaxy" caused by intermediate layers of different structures

Three methods for the measurement of the change ΔΦ of the work function Φ of a metal surface due to the presence of adsorbed particles (e. g. oxygen) have been developed utilizing the surface ionization of a beam of metal atoms (e. g. In, Sr) as a probe. The experiments have been performed with a mass spectrometer at ultrahigh vacuum. In the first method the temperature dependency of the ion emission current is used for the determination of the work function Φ considering certain limiting conditions. The two other methods which may be applied simultaneously with the first one, involve a direct measurement of ΔΦ by compensating the change of the contact potential by an external voltage: In the second method the contact potential between the ionizing surface and a surrounding reference electrode is used to control the ion optical conditions for the ion emission, whereas in the third method the change in the kinetic energy of the ions caused by a change of the contact potential between the ionizing surface and the entrance slit of the mass spectrometer is used as a measure of ΔΦ

An electric spark of high energy density is produced by discharging a capacitor through closely spaced electrodes immersed in a liquid dielectric. A hot plasma arises which is surrounded by a compression ring of highly compressed matter. The shape and state of motion of the compression ring are photographed by the aid of X-ray flashes. Out of the magnitude of the compression, and since the broadening velocity of the compression ring goes nearly to zero, it is concluded that the original liquid in the compression ring undergoes, for a time, a solidification by shock wave pro-cesses. These investigations were carried out in organic liquids and water.

Simplified expressions for the calculation of the contribution of the heavy components to the viscosity and to the translational thermal conductivity have been tested for pure and mixed plasmas

Under normal conditions the carbon cycle is a stationary process. A varying CO 2 partial pres-sure would cause deviations from the steady state. This process is analysed using a differen-tiated flow scheme of the carbon through the biosphere. For this purpose the biomass on land is divided into three reservoirs with average fixation times of 1 day (day-night-cycle), 2 years (annual period), and 100 years (timber, humus), respectively. The kinetic analysis shows that about 70% of the global respiration follow fluctuations of the rate of photosynthesis immediately, so that this portion of the excess of fixed carbon will be returned in the atmosphere within a few years. Only 30% of the total cycle passes through the largest reservoir (timber, humus) which could serve as a buffering system. But since the time constant of this partial cycle is about 100 years, the CO 2 exchange with the ocean is the faster process

The X-ray photoelectron energy spectra of chromium, molybdenum and tungsten hexacarbonyls are found to show a multi-peak structure. This is particularly remarkable in the C 1S and O 1S binding energy region. This peculiarity is tentatively interpreted on the basis of a double excitation process involving the ionization and simultaneous excitation of a valence electron

The fractionation of the oxygen isotopes of the water molecules in CuS0 4 -5 H 2 0 and in aqueous solutions of copper sulphate has been measured at 25 °C. In the total crystal water (G) three kinds of water can be distinguished by their binding: 1) The bisector of the two lone pairs directed to­wards the copper ion (Kj), 2) One of the lone pairs directed towards the copper ion (K 2 ), 3) The two lone pairs directed towards two hydrogen atoms of water molecules coordinated with the cop­per ion (L). The water molecules in the copper sulphate solution are considered either hydration water (HW) or bulk water (FW). Defining a.\-B= ( 18 0/ 16 0)a/( 18 0/ 18 0)b the following results have been obtained: There remains some doubt if the values attributed to ctKi-G and aK2-G have to be interchanged. The elementary cell of CuS0 4 *5 H 2 0 consists of two molecules. Four molecules of Kj-water are coordinated with one copper ion and four molecules of K 2 -water are coordinated with the second copper ion. The remaining two water molecules are of L-type. It is concluded from the results that on dehydration at temperatures below 50 °C first one copper ion loses it’s water and then the other. There is some doubt as to which group breaks up first. In addition, the results show that the L-type water becomes quantitatively the water of the monohydrate in agreement with the conclusions drawn from the results of the fractionation of the hydrogen isotopes in CuS0 4 -5 H 2 0. It is de­monstrated that, by considering only the overall fractionation of the oxygen or hydrogen isotopes between total crystal water and the saturated solution, wrong conclusions about the crystallization process could be drawn. In the case of CuCl 2 solutions, it has been shown that the separation factor aHW-FW is sensi­tive towards changes in the structure of the solution.

Es wird eine automatische Röntgen-Streuapparatur zur Untersuchung von flüssigem Natrium be-schrieben. Zum Unterschied früherer Messungen an freien Natriumoberflächen wurde eine senkrecht-stehende Meßkammer mit Beryllium als Röntgen-Fenstermaterial verwendet. Messungen am flüssigen Natrium wurden bei einer Temperatur von 114,3 °C durchgeführt und aus den Streudaten die statische Strukturfunktion und die atomare Dichteverteilung ermittelt. Die Ergebnisse werden mit den bisher bekannten Messungen am flüssigen Natrium verglichen

Relaxation times and Overhauser enhancements for protons in metal (K, Li, Na, Ca) ammonia solutions have been measured at 176, 3400 and 11 200 G over a wide range of concentrations and temperatures. Both the relaxation rate due to the interaction with unpaired electrons and the Overhauser coupling parameter are strongly frequency-dependent and undergo a characteristic change at metal concentrations of 0.05 - 0.5 M. They can be explained by a mixed scalar and di-polar coupling. Coupling amplitudes, spectral intensity functions and correlation times with their temperature-dependence have been determined. The results and a comparison with Knight shift data show that more than one paramagnetic species in the solution, and different mechanisms of relative motion between protons and electrons must contribute. The major part of the coupling is of a short range type, where the electrons, by some kind of tunneling, are the carriers of the motion. The discussion postulates dissolved electrons with rather flexible solvation spheres where spin density is greatly smeared out. The second paramagnetic species may be the "monomer" often dis-cussed in the literature. Additional experiments which support our conclusions have concerned the self diffusion coefficient of the protons, and the Overhauser enhancement of lithium-7

Starting from a set of Slater-type atomic orbitals with seven s-, four p-, one d- and one f-type functions the total wavefunction is constructed by a C I-calculation. The highest degree of the secular equation is 84 for Li ( 2 S) and 142 for Li - ( 1 S). By diagonalizing the first-order density matrices approximate natural orbitals are obtained. These are analysed and used again in a further C I-calculation. The best values for the electron-affinity are 0.572 eV and 0.614 eV. For the latter value only the correlaton energy of the L-shell of Li - is considered

Starting with a model for odd-odd nuclei, which had been used in former investigation (rigid, symmetrical top for the deformed even-even core, two extra particles in a Nilsson potential), the influence of the coupling term H c and of the residual interaction V PN on the rotational spectrum of the odd-odd nucleus 166 Ho are discussed. It is shown, that in this nucleus neither the coupling term H c nor a pure Wigner force can explain the characteristic features of the rotational spectrum. It is therefore necessary to introduce a residual interaction V PN , which contains at least a spin-spin term. The explicit calculation for the nucleus 166 Ho with a simple ansatz (δ-interaction with spin-spin term) already leads to a qualitative explanation of the particularities in the observed rotational spectrum. The investigations show a way how to get more information about the protonneutron interaction in odd-odd nuclei

On Nucleon-Nucleon S-Scattering. II. The Numerical Stability Test The numerical stability test is discussed which prevented the decision on the usefulness of a non-relativistic nucleon-nucleon potential of a previous paper, and this decision is finally accomplished by fulfilling the stability condition

Because of the discrepancies between different determina­tions of the half-life T of 87 Rb and the importance of T for measuring geological ages we decided to compare the separat­ed isotopes. All experimental errors are the same in both cases, and the difference of the counting rates has to be attri­buted to 87 Rb. In this manner we got T = (4.88 + 0.10) • 10 10 y

The exchange part of the single-particle spin-orbit potential following from a two-body spin-orbit potential is calculated. Scheerbaum's approximation of setting the exchange part equal to the direct part is investigated

The intramolecular force fields of nitrogen trichloride have been determined using the recent experimental data on the vibrational frequencies. Three different methods have been used for the evaluation of force constants. The results ob-tained are quite consistent

Force constants for nine ions belonging to Oh point group have been evaluated by using Orbital Valence Force Field. The constants have been compared with their values obtained by using Urey-Bradley Force Field. The validity of the two methods has been discussed

Stark-effect measurements on the rotational transition J = 1 → 2 of InCl are described. The vapour pressure in the absorption cell was chosen so that the quadrupole hyperfine structure due to the Cl-nucleus could not be resolved. Thus we neglect this coupling in the calculation of the Stark-effect. The derived electric dipole moment in the ground vibrational state is: 115 In 35 Cl : | μ 0 = (3.79 ± 0.10) D. The electric dipole moment of 205 Tl 19 F : | μ 0 | = 4.2282 (8) D was used for the calibration of the electric field

Aromaten bilden mit einigen ihrer Derivate unsym- metrische Excimere 1 . Ob unsymmetrische Excimere auch zwischen dem aromatischen Pyren (I) und dem heteroaromatischen, zu Pyren isoelektronischen 4.5- Iminophenanthren (II) gebildet werden, soil hier un- tersucht werden. Da beide Molekiile nahezu gleiche Elektronenanregungszustande haben 2 , jeweils sym- metrische Excimere bilden 1,3 und (II) 4 ebenfalls wie (I) ein planares Molekiil ist, erscheint es naheliegend, die Bildung unsymmetrischer Excimerer zwischen (I) und (II) zu erwarten. Abbildung 1 zeigt die Struktur- formeln beider Molekiile

The postulate that a liquid possesses characteristic frequen­cy and enegy of vibration, and that all other energy goes to “free” diffusion, leads to the relation where T m is the melting point, M the atomic mass, V the atom­ic volume and L the heat of fusion. A is a constant obtainable from the Lindemann relation, 0.36 for the alkali metals, 0.30 for noble metals. This relation is in very good agreement with experimental self-diffusion data of liquid metals

It has been observed that in several semiconductors an in-crease in total impurity concentration leads to an increase in the low-temperature mobility due to pairing effects. The trans port coefficients rʜ, r Q ' and r Q necessary for the analysis of the Hall effect and the magnetoresistance, in the event of di-pole scattering, are derived for the cases k a ≫ 3 and k a ≪ 3 (k = wave number of the quasi-free charge carrier, a = dipole length). For k a ≫ 3 the coefficients are dependent on tempe-rature, effective mass, and dipole length, whereas for k a ≪ 3 they are constant

Detailed calculations of population densities of excited levels in a decaying hydrogen plasma flow predict population inversions within a definite range of plasma parameters. This has been verified experimentally in a rapid expanding plasma where the characteristic time of decay was much shorter than the relaxation time of the ground state. Population inversions have been found for the first transitions of the Paschen and Brackett series