Volume 23, Issue 8

Starting from the exact steady state Navier-Stokes equation and taking the quadratic inertia term into account in an appropriate way one can show the existence of a coupling of the translational and rotational motions of a rigid sphere in an incompressible fluid. No-slip boundary conditions are used. The coupling consists in a transverse force proportional to the cross product of the linear and angular velocities of the sphere. This force is closely related to the Magnus effect. It is of interest for the theory of Brownian motion of particles with internal degrees of freedom.

The selfconsistent theory of recombination-dissociation kinetics developed in an earlier article is derived in a more rigorous manner. A noniterative solution is obtained for the resulting equations describing the nonequilibrium distribution of the internal molecular energy levels. This method of solving these equations also leads to a number of interesting mathematical and physical insights about the importance of nonequilibrium effects in recombination-dissociation kinetics. Implicit in these equations is a method for calculating the vibrational relaxation times for both recombination and dissociation reactions. These same equations also arise in calculating the rate constant for a nontrivial model of a dissociating diatomic molecule. The mathematical techniques used to derive this information also allows us to show that the selfconsistent theory is really a generalization of the conventional steady-state approximation and a special case of a projection operator formalism for solving problems in nonequilibrium statistical mechanics.

The absorption band spectrum of FCl 35 /FCl 137 is photographed in the region 5200—4600 A using a 5 m Ebert spectrograph. 27 bands of the O + ← 1 Σ + -system are analyzed and their origins calculated. The isotopic shifts measured on 7 bands allow the determination of the exact numbering of the vibrational levels of the excited 0 + -term. Furthermore molecular constants of both states involved could be determined. By means of this set of bands an empirical formula representing irregular vibrational terms of diatomic molecules is tested. Connecting the dissociation energy of FCl and Cl 2 and the formation energy of FCl a value of the dissociation energy of the F 2 -molecule is derived.

Appearance potentials and ionization efficiency curves of negative ions formed in SiCl 4 , CH 3 SiCl 3 , (CH 3 ) 2 SiCl 2 , (CH 3 ) 3 ) 3 SiCl, C 2 H 3 SiCl 3 , and C 6 H 5 SiCl 3 by electron impact have been measured by using a Fox ion source. Negative molecular ions were observed in SiCl 4 , C 2 H 3 SiCl 3 and C 6 H 5 SiCl 3 besides several fragment ions. The electron affinity of the SiCl 3 radical was found to be about equal to the electron affinity of the chlorine atom. The electron affinity of SiCl 2 is shown to be higher than 2.5 eV. Dissociative electron capture processes from SF 6 – have been found in mixtures of SF e and silicon compounds (such as SF 6 – +SiCl 4 ➝ Cl – +SiCl 3 +SF 6 ). It is concluded that in these processes the electron in SF 6 – behaves like a free electron of zero kinetic energy. Various reactions of the O – -ion with the silicon compounds have also been observed.

Quantum yields of hydrogen halide formation upon irradiation (λ=313 nm) of N,N-dimethylaniline together with different benzene halogen-derivatives in methanolic solution have been measured. In the discussion attention has been paid not only to relations between quantum yields of hydrogen halide and electron affinity of the acceptor, but also to the role of the interaction energy between transition moments in a heteropolar excimer.

Es wurde die Temperatur- und Konzentrationsabhängigkeit der Halbwertsbreite einiger Thiophen A 1 -Schwingungen untersucht. Die Messungen zeigen, daß ein Teil der Bandenbreite bei gewissen Schwingungen proportional mit der Verdünnung abnimmt. Temperaturabnahme führt bei den gleichen Schwingungen zur Verbreiterung der Banden. Die Abnahme der Bandenbreite bei Verdünnung ist nicht meßbar vom Dipolmoment der Moleküle des Mischungspartners abhängig. Diese drei wesentlichen Ergebnisse lassen darauf schließen, daß der hier untersuchte Anteil der Bandenbreite durch Resonanzverbreiterung hervorgerufen wird.

The forward steady-state behaviour of a one-dimensional abrupt p + -n junction germanium diode at zero and at low to high injection levels is analysed. For this purpose the numerical integration of the current differential equations, the continuity equations, and Poisson’s differential equation is performed not only inside the space-charge layer but also along the quasineutral regions of the diode satisfying the boundary and continuity conditions. The integration is made on a digital computer without applying the Boltzmann equilibrium approximation in the space-charge layer and the space-charge neutrality approximation in the quasineutral regions. Furthermore, the acoustical and optical mode scattering, the ionized impurity scattering, and the Hall-Shockley-Read and Auger recombination processes are included in the calculation. The method of solution applied differs from those already available in the literature and permits the “exact” computation of the space-charge density inside the relatively long (compared with the Debye length) quasineutral p and n regions of the diode considered. The numerical results for the hole and electron concentration distributions, the electric field distributions, the electron current density distributions, the electrostatic potential distributions and the space-charge density distributions are reported for five values of the total current density across the p-n junction. The comparison of the obtained numerical solutions with the closed analytical solutions for zero bias (as a test of the computer program) on the one side and of the computed current/voltage characteristic of the p-n junction with experimental values on the other side shows satisfactory agreement.

The analysis of Shubnikov-De Haas oscillations in n- and p-type Bi 2 Te 3 indicate the existence of a multivalley structure of valence and conduction band. In p-type Bi 2 Te 3 the surfaces of constant energy are found to consist of 6 ellipsoids. Spin splitting of the Landau-levels was observed, the anisotropy of the g-factor in the trigonal-bisectrix plane is consistent with an existing theory. In n-type Bi 2 Te 3 Hall-coefficient, magnetoresistance and g-factor do not follow the predicted pattern of a simple many valley model, so that the number of ellipsoids could not be determined with certainty. The presence of an additional band must be considered.

In a thermocell with silver electrodes the thermoelectric power ε at zero time of the molten systems (Ag + Rb)NO 3 and (Ag + Cs) NO 3 at various temperatures has been measured. These data, combined with previous measurements 1 , allow to obtain information about the heat and electricity transport phenomena in the fused systems (AgNO 3 +alkali nitrates).

The quantum efficiency of the production of F′-centers under absorption of light in the F-band is strongly temperature dependent. This paper considers a non-radiative model for this reaction, in which transitions of the excited F-center electron into a polaron band with 2p-symmetry are calculated. The polaron is treated by the strong coupling method giving the possibility of introducing hydrogen functions for the electronic states. The temperature curve of the quantum efficiency is obtained by means of the Pauli master equation. The effective electron mass, which equals the free electron mass after the adaption of the quantum efficiency to the experimental data, stands as a free parameter in the theory.

The concentration of electron centers in polycrystalline NaCl formed during irradiation has been determined using a chemical method previously described. The influence on the formation of electron centers under irradiation, of thermal treatment, Ca ++ doping and grinding of the salt has been studied. The growth of electron centers with time of irradiation was found to obey the equation given by Mitchell, Wiegand and Smoluchowski. In this equation occur the two types of anion vacancies present prior to irradiation, the rate of formation of new vacancies and the rates of center formation from initial and new vacancies. Consistent with the Crawford-Nelson mechanism, the concentration of electron centers increases proportionally with the square root of the Ca ++ concentration. At a Ca ++ /Na + ratio of 2.5 × 10 -4 , about 11 Ca ++ are needed to form an additional electron center. The formation of defects by grinding the salt depends on its thermal pretreatment as well as on its Ca ++ concentration. Most of the defects formed during grinding anneal when the salt is stored in moist air. When azoethane is adsorbed on preirradiated NaCl, the concentration of electron centers decreases. A quantitative evaluation of this effect leads to the conclusion that the concentration of defects formed by grinding the salt is orders of magnitude higher near the surface than in the bulk.

A plane crystal spectrometer was used to measure relative integrated intensities of K α X-ray satellites in fluorescence spectra of Na in NaF, and of Mg, Al, Si in metals and oxides. A comparison between the measured intensity of the Κ α'α3α4 satellite group and the intensity obtained from electron excitation measurements indicates that the production probability of KL double-hole states is independent of the excitation mode. The measured intensities in metals are in agreement with calculated intensities based on the sudden approximation theory of x-ray satellites of free neon-like ions. The bond in fluoride and oxides was shown to increase the relative intensity by about 13%. From intensity considerations, the Κ α5α6 satellite group was attributed to KL 2 triplehole states.

Es wird die Richtungsdispersion der außerordentlichen Ultrarot-Banden des n-Spektrums, k-Spektrums und des Reflexionsspektrums von α-Quarz nach den Gleichungen aus Teil I (Z. Naturforsch. 22 a, 359 [1967]) berechnet und im einzelnen diskutiert. Die als Eingangswerte benötigten Oszillatorparameter sind der Arbeit von SPITZER und KLEINMAN entnommen. In α-Quarz existieren alle vier der prinzipiell möglichen Bandentypen : 6 (t → 1) -Banden, 2 (1 → t) -Banden, 2 (t → t)-Banden, 2 (1 → 1) -Banden (t = transversal, 1 = longitudinal), die sich bezüglich ihrer Richtungsabhängigkeit wesentlich voneinander unterscheiden. Es wird gezeigt, daß einige der Resonanzen, die von SPITZER und KLEINMAN Kombinationsschwingungen zugeordnet wurden, in Wirklichkeit durch die transversalen Komponenten der in den Kristallhauptrichtungen streng longitudinalen Schwingungen verursacht werden.

NMR transients in solids have been calculated using the method of LOWE and NORBERG 1 and its extension by POWLES and STRANGE 2 . Some remarks are given concerning the evaluation of the formal solution for the signal after several pulses. So far the influence of the pulse durations and of the longitudinal relaxation is neglected usually, higher terms of the power series expansion of the signals were discussed only with respect to corrections of their amplitudes. Some remarkable differences between these calculations and new experimental results to be reported here are explained — at least in principle — avoiding these limitations: The maximum amplitude of the echo after two 90°-pulses (phase difference of their modulations Δφ=90°) occurs not exactly at a time twice the pulse distance, the deviation is explained considering the duration of the pulses and the decay of the echo envelope. After two pulses with Δφ=0° an echo was found which should disappear only in an ideal twospin system. For a three pulse sequence the influence of the longitudinal relaxation is described; and in a multi-pulse sequence the calculated modulation of the amplitude of successive echoes was checked by experiments.

The NMR signals of the nuclei 2 H, 6 Li, 7 Li, 23 Na, 87 Rb and 133 Cs have been investigated in aqueous solutions. The ratios of the Larmor-frequencies of these alkali nuclei relative to 2 H have been measured with high accuracy. Because the Larmor-frequencies depend on the concentration of the aqueous solutions, an extrapolatiton to vanishing concentration was made. From these ratios of Larmor-frequencies, a magnetic moment for the alkali nuclei has been derived and has been compared with the available nuclear magnetic moments from atomic beam or optical pumping experiments. The difference in the magnetic moments results from the shielding of the alkali nuclei by the water molecules around the ions. The shielding constants are: σ (Rb + ) = — (2.0 ± 0.2) ·10 -4 and σ (Cs + ) = — (3.4 ± 0.1) · 10 -4 relative to the free ion. The shift of the 133 Cs NMR line as a function of the concentration of aqueous solutions of Cssalts is given in detail. The influence of the chlorides of some elements in the iron group and of some lanthanide elements on the position of the 133 Cs NMR line is shown.

For a series of alkyl radicals we have measured the electron g factors and hfs splitting constants by EPR methods. The isotropic chlorine hfs constants are discussed in terms of the Karplus-Fraenkel formula αCl=Q CCl Cl Qc . The results indicate that Q Cl = Δ (Cl) Q C π with Δ (Cl) =0.16. From this and Fischer’s Δ (Xi) parameters for the other substituents, effective σ-π-parameters could be determined to be There exists a proportional relationship between the g factor shift ΔgCl due to chlorine substituents and Cl Σ Q Cl π from which ΔE n→π Cl =15.6·10 3 cm -1 was determined. CI

The radiation emitted from the axis of a low current cylindric arc in chlorine was quantitatively recorded. In the UV-region appears the affinity-continuum of chlorine which begins at a longwave threshold of 3428 A yielding an electron-affinity for Cl of 3.616 eV. With spectroscopic temperature measurements and by means of Kirchhoff’s law, the absorption coefficient of the affinitycontinuum is obtained after separation from the background with a linear extrapolation. Thereby the detachment cross section of the negative chlorine-ion is calculated as a function of photon energy. Deviations from thermodynamic equilibrium are accounted for.

The cosmogenic production rates of Be-10 and Be-7 in the atmosphere have been derived from activity measurements of the Be-isotopes in soils. The ratio of the spallation yields was found to be Be-10/Be-7 =0.7 ±0.3.

The phosphorescence of ferrocene in glassy solution at 77 °K has been investigated and compared with the results of other authors. There is no evidence that the observed weak phosphorescence can be unequivocally Attributed to ferrocene.