Showing papers by "Technical University of Dortmund published in 1975"
TL;DR: In this article, the perfect crystal neutron interferometer was used to test the spinor rotation of spin- 1 2 -systems and showed interference oscillations consistent with the predicted 4π-value.
283 citations
TL;DR: In this article, the authors derived a set of linearized equations for the deviation from the equilibrium value of the quasiparticle distribution function as well as of the order parameter, and the equations were solved for the case of an injection of a stationary quaiparticle into a superconductor.
Abstract: Starting from the equation of Gor'kov and Eliashberg in a form introduced by Eilenberger, we derive a set of linearized equations for the deviation from the equilibrium value of the quasiparticle distribution function as well as of the order parameter. These equations resemble the Boltzmann equation and the Ginzburg-Landau equation, respectively, and they form a set of coupled equations. Two different modes can be distinguished, depending on whether the order parameter changes in magnitude or in phase. The equations are solved for the case of a stationary quasiparticle injection into a superconductor and the change in the electrochemical potential of the quasiparticles is calculated. Furthermore, we treat the problem of a current flowing perpendicular to a superconducting-normal interface in which a normal current is converted into a supercurrent, and we calculate the extra resistance of the interface.
280 citations
111 citations
TL;DR: In this article, the authors examined the characteristics and potentialities of the injection method described by Sebastiani, ohls and riemer for the determination of small amounts of substances and for the analysis of concentrates of trace elements.
86 citations
TL;DR: In this article, the theory of polar fluids is applied to five different viscometric flows and to the flow around a slowly rotating sphere, and it is demonstrated that the theory may serve as a model for the flow of suspensions if a velocity slip along a solid wall is accounted for.
Abstract: The theory of polar fluids, briefly reviewed and shown to be identical to the theory of micropolar fluids, is applied to five different viscometric flows and to the flow around a slowly rotating sphere. Comparing theoretical predictions with experimental results for the viscometric flows it is demonstrated that the theory may serve as a model for the flow of suspensions if a velocity slip along a solid wall is accounted for.
65 citations
TL;DR: In this article, it is shown how approximate charge neutrality of the metal is maintained in these modes, based on a microscopic theory developed previously by the authors, and it is also shown how the metal can be maintained in the order-parameter collective modes in a dirty superconductor.
Abstract: Recent observations of propagating order-parameter collective modes in a dirty superconductor are explained on the basis of a microscopic theory developed previously by the authors. It is shown how approximate charge neutrality of the metal is maintained in these modes.
59 citations
TL;DR: A number of papers have appeared with the purpose of generalizing Albert's long-standing result that a simple right alternative algebra of finite dimension over a field of characteristic f 2 that has a unit element e and an idempotent c # e is necessarily alternative as discussed by the authors.
52 citations
TL;DR: The crystal structure of hexamethylcyclotristannathiane [(CH3)2SnS]3 was determined by means of X-ray single crystal methods (number of reflections: 1660; a = 9.685(3), c = 17.302(4) A; Z = 4; space group P41) as discussed by the authors.
50 citations
TL;DR: In this paper, upper bounds for the ground-state energy of the exciton-phonon system were derived for all ratios of the polaron radii to the excitons radius.
50 citations
TL;DR: A complete and simple method for finding the positive Boolean function mentioned above is given and the problem of obtaining all irredundant sums from the list of all prime implicants and an arbitrary list of implicant representing the function is solved.
Abstract: A new method for computing the prime implicants of a Boolean function from an arbitrary sum-of-products form is given. It depends on the observation that the prime implicants of a Boolean function can be obtained from the prime implicants of its subfunctions with respect to a fixed but arbitrary variable. The problem of obtaining all irredundant sums from the list of all prime implicants and an arbitrary list of implicants representing the function is solved. The irredundant sums are in one-to-one relation to the prime implicants of a positive Boolean function associated with these lists. The known formulas of Petrick, Ghazala, Tison, Mott, and Chang are obtained as special cases and incompletely specified functions can also be handled. We give a complete and simple method for finding the positive Boolean function mentioned above. The paper is self-contained and examples are included.
44 citations
TL;DR: In this article, the leading term of the n-th order Raman cross section for incident and scattered frequencies near or above the energy gap in semiconductors using an uncorrelated electron-hole continuum and a momentum independent electron-phonon interaction was calculated.
TL;DR: In this article, the effective mass Hamiltonian for excitons in uniaxial crystals is discussed by means of a modified perturbation approach, which gives upper and lower limits for the exact energies.
Abstract: The effective mass Hamiltonian for excitons in uniaxial crystals is discussed by means of a modified perturbation approach. This approximation scheme gives upper limits for the exact energies; the validity of the approach is tested by deriving lower limits for the exact energies. The spacing of the two limits is shown to be satisfactorily small in a wide range of the anisotropy parameter. This parameter free approach leads to energies, which show good agreement with the results of involved variational calculations. In addition analytical expressions are obtained for the wave functions, which are easy to handle and can be used in more complex situations e.g. to include the description of external field influences.
Der Effektiv-Massen-Hamilton-Operator fur Exzitonen in uniaxialen Kristallen wird mit Hilfe einer modifizierten Storungsrechnung behandelt. Das Naherungsverfahren liefert obere Grenzen fur die exakten Energien. Der Gultigkeitsbereich der Naherung wird mit Hilfe von unteren Grenzen fur die exakten Energien diskutiert. Es wird gezeigt, das fur einen grosen Bereich des Anisotropieparameters der Abstand der oberen und unteren Grenzen zufriedenstellend klein ist. Fur die Energien liefert dieses parameterfreie Verfahren Ergebnisse, die mit aufwendigen Variationsrechnungen gut ubereinstimmen. Zusatzlich werden analytische, anisotropieabhangige Wellenfunktionen erhalten, die sehr leicht hand-habbar sind und zur konsistenten Behandlung weiterer Effekte, z. B. auserer Felder, ver-wandt werden konnen.
TL;DR: In this paper, a cryptoradical mechanism is proposed which involves no free stannyl radicals; the reagent directly attacks 1 or 2, benzophenone acting as a low energy leaving group.
TL;DR: In this paper, an empirical linear-combination-of-atomic-orbitals energy-band model is described for simple-cubic and fcc TlCl, TlBr, and TlI which explains optical data and reproduces existent a priori band structures.
Abstract: An empirical linear-combination-of-atomic-orbitals energy-band model is described for simple-cubic and fcc TlCl, TlBr, and TlI which explains optical data and reproduces existent a priori band structures. This band model is used to discuss the type of bonding in the polymorphs, and to check the applicability for ten-electron systems of the Phillips-van Vechten dielectric theory of bonding.
TL;DR: In this article, it was shown that the nuclear polarisation is built up in radical pairs Me 3 Sn··SnMe 3 1 1 1, which is not observed in hexamethylditin.
TL;DR: In this paper, the authors present solche Singularit~iten kurz 2-dimensionale Spitzen, deren minimale Aufltisungen zyklisch sind.
Abstract: Die vorliegende Arbeit liefert einen Beitrag zum Studium der tokalen Ringe in den Spitzen der Hilbertschen Modulgruppe eines reell quadratischen Zahlk6rpers. Im Hinblick auf die yon Hirzebruch [t0] beschriebene AufliSsung dieser Singularit~iten ist es naheliegend, allgemeiner 2-dimensionale normale Singularitiiten zu betrachten, deren minimale Aufltisungen zyklisch sind. Wir nennen solche Singularit~iten kurz 2-dimensionale Spitzen. Sei (S, p) eine 2-dimensionale Spitze. Ein numerisches Maf3 ftir die Singularit~it liefert die lokale Hilbertfunktion hs,p, die wie folgt definiert ist. Sei znn~ichst allgemeiner (9 ein noetherscher lokaler Ring (auch Stellring genann0 mit maximalem Ideal /f, dann ist die Hilbertfunktion h e definiert durch
TL;DR: In this article, the thermally stable solids Re 2 (CO) 8 [μ-InRe(CO) 5 ] 2 and Re 4 (CO 12 [μ 3 -InRe (CO), 5 ] 4 could be obtained by treatment of In with Re 2(CO), 10 in a bomb tube and a mechanism of the formation of the latter cluster from the first one is proposed.
TL;DR: In this paper, the interaction of an electron-hole pair is studied in a polar semiconductor, each particle being coupled to the lattice by the Frohlich interaction, and the results are discussed in connection with exciton screening in the thallous and cuprous halides.
Abstract: The interaction of an electron-hole pair is studied in a polar semiconductor, each particle being coupled to the lattice by the Frohlich interaction. The theory of Gross and Tulub is used for the description of a single polaron. This theory which gives satisfactory results for both intermediate and strong coupling is then generalized to the problem of two interacting polarons. For not too strong coupling the effective electron-hole potential will be presented in form of a series with increasing powers of the coupling constant. The first term of this series gives the well known Haken potential, whereas the higher terms are corrections to the potential which will become important for stronger coupling. The results are discussed in connection with exciton screening in the thallous and cuprous halides.
Die Wechselwirkung eines Elektron–Loch-Paars wird in einem polaren Halbleiter unter-sucht, bei dem jedes Teilchen uber die Frohlich-Wechselwirkung an das Gitter gekoppelt ist. Fur die Beschreibung eines einzelnen Polarons wird die Theorie von Gross und Tulub benutzt. Diese Theorie, die sowohl Fur mittlere als auch starke Kopplung befriedigende Ergebnisse liefert, wird dann auf das Problem zweier wechsehvirkender Polaronen ver-allgemeinert. Das effektive Elektron–Loch-Potential wird, Fur nicht zu starke Kopplung, in Form einer Reihe nach wachsenden Potenzen der Kopplungskonstante dargestellt. Der erste Term dieser Reihe liefert das bekannte Haken-Potential, wohingegen die hoheren Terme Potential-Korrekturen darstellen, die Fur starkere Kopplung wichtig werden. Die Ergebnisse werden in Zusammenhang mit der Abschirmung von Exzitonen in den Thallium-und Kupferhalogeniden diskutiert.
TL;DR: T1I-layers with simple cubic and f.c. structure have been prepared by evaporation of CsI and RbI, and the optical absorption spectra of these layers have been measured for the first time as discussed by the authors.
TL;DR: In this article, a chain reaction with S H 2 mechanism and attack of R at the Hg was described, which is called Me 3 M 2 Hg (M = Si, Ge) under irradiation (daylight).
TL;DR: In this article, a planar Re2In2-metal ring with a Re-Re distance of 3.232° and an acute angle at the bridging atom In of 71.07° are consistent with the existence of a Re - Re bond.
Abstract: Re2(CO)8{μ-InRe(CO)5}2 kristallisiert in der Raumgruppe P 21/n mit den Gitterparametern a = 6.788(2) A, b = 16.352(3) A; c = 12.519(3) A und β = 89.23(5)° mit zwei Formeleinheiten (Z = 2) pro Elementarzelle. Das Molekul enthalt einen ebenen Re2In2-Metallring, in dem der Re-Re-Abstand = 3.232(1) A und der spitze Winkel am Bruckenatom In von 71.07(3)° eine Bindung zwischen den Rheniumatomen aufzeigen. Die Re-Atome der beiden Re(CO)5-Liganden liegen in trans-Stellung zur Re2In2-Ringebene. Die Mittelwerte der ubrigen Bindungsabstande betragen: In - Re = 2.766(1) A, Re - C = 1.98(2) A, C - O = 1.14(2) A.
Single Crystal X-Ray Analysis of Compounds with a Covalent Metal-Metal Bond, III. The Molecular and Crystal Structure of Octacarbonyl-bis[μ-(pentacarbonylrhenium)indium(III)]-dirhenium
Re2(CO)8{μ-InRe(CO)5}2 crystallizes in the space group P 21/n with the lattice parameters a = 6.788(2) A, b = 16.352(3) A; c = 12.519(3) A, and β = 89.23(5)° with two formula units in the cell. The molecule contains a planar Re2In2 ring, in which the Re-Re distance of 3.232(1) A and the acute angle at the bridging atom In of 71.07(3)° are consistent with the existence of a Re - Re bond. The Re atoms of the two Re(CO)5 ligands have a trans-configuration with respect of the plane of the Re2In2-metal ring. The mean values for the remaining bond distances are: In - Re = 2.766(1) A, Re - C = 1.98(2) A, C - O = 1.14(2) A.
TL;DR: In this article, the trifluormethyljod-Verbindungen CF 3 JO, CF 3 JOF 2 and CF3 JO 2 konnen ausgehend von CF 3J, CF3JF 2 oder CF3 JF 4 durch Ozonisierung oder durch Umsetzung mit SiO 2 dargestellt werden.
TL;DR: In this paper, an SH2 reaction at the Si is found: (kind = 2.5 × 104 1 mol−1 s−1) a "cage" effect leads to the formation of disilane or digermane, respectively.
TL;DR: In this paper, die Darstellung und die Eigenschaften des Brommonofluorid-Pyridin-Komplexes werden beschrieben.
TL;DR: In this paper, die Stabilitat der zweidimensionalen Stromung einer viskoelastischen Flussigkeit im Raum zwischen zwei ebenen festen Wanden, die einen Winkel miteiander bilden, untersucht.
Abstract: In dieser Arbeit wird die Stabilitat der zweidimensionalen Stromung einer viskoelastischen Flussigkeit im Raum zwischen zwei ebenen festen Wanden, die einen Winkel miteiander bilden, untersucht. Der Winkel zwischen den beiden Ebenen und der Durchflus pro Lange sind zwei charakteristische Parameter der Stromung. Es wird gezeigt, das bei gegebenem Winkel fur bestimmte Bereiche des Durchflusses stationare Storstromungen existieren.
TL;DR: In this paper, the cyclopentadienyltin(IV) halides CpnSnHal4−n (Hal = Cl, Br, I) can be prepared by stoichiometric alkylation of SnHal4, some also by halogenation of Cp2Sn.