Double quantum transitions in paramagnetic resonance

The theory of double quantum transitions of the M=±2 type, with regard to inhomogeneously broadened spin systems is studied in this paper with the approximation ²T₂T₃ 1. We suppose that the inhomogeneous broadening is formed by an inhomogeneous crystal field. The obtained results describe the magnitude of absorption as a function of the h.f. power and also describe the shape of the absorption curve. It is demonstrated that in inhomogeneously broadened spin systems the absorption curve of double quantum transitions has the form of the difference of two different Lorentz's curves and that at the saturation ( ²T₂T₁ 1) the absorption increases with the cube of the h.f. field intensity. The shape of the curves is expressed by means of phenomenological relaxation constants of the system.

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M=±2 ²T₂T₃ 1. , - . . , ( ²T₂T₁ 1) . .

     

Les absorbants de son resonants

Résumé Dans la présente étude, on trouve un bref résumé des travaux de l'auteur, de ses collègues et collaborateurs, concernant l'utilisation des résonateurs dans l'acoustique architecturale. On explique tout d'abord le problème de l'inpluence des résonateurs sur la durée de la réverbération des salles. Se basant sur des considérations théoriques, l'auteur déduit le critère de l'emplacement le plus favorable des matières absorbant le son dans le résonateur même et discute la possibilité de l'absorption totale du son par le résonateur. Dans le cas des systèmes de résonateurs pareils disposés régulièrement sur les murs, le diapason pouvant être obtenu d'une importante absorption est relativement faible. En se servant de systèmes résonants d'absorption comportant plusieurs couches de résonateurs, reliés en série, le diapason de l'absorption importante peut être notablement élargi. L'auteur explique la corrélation du coefficient d'absorption et de l'angle d'incidence de l'onde sonore. En conclusion, on mentionne des exemples de l'utilisation pratique des résonateurs d'absorption les plus simples pour obtenir la caractéristique de l'absorption de fréquence exigée. On discute aussi le problème de l'influence des vibrations simultanées de la paroi extérieure du système de résonance sur la caractéristique de l'absorption du son.

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. . . , , . , , . . ; .

     

Новый метод измерени я магнитокалорическ ого эффекта у ферромагни тных полупроводнико в

, .     

Anti-parallel ferroelectric domains in surface space-charge layers of BaTiO3

It is shown on simplified models of a surface space-charge layer of a single crystal of BaTiO ₃ that in the surface region, in which the direction of the electric field is opposite to the direction of spontaneous polarization inside the crystal, anti-parallel domains can exist. The dimensions of these domains are determined. The use of the results obtained is proposed for interpreting the microrelief of the etch figures and for explaining the different phases of the polarization reversal process of a single-domain single crystal of BaTiO ₃.

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BatiO₃

BaTiO₃ , , , . . BaTiO₃.

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The author would like to thank J. Kaczer, Z. Málek and V. Dvoák of the Institute of Physics, Czechoslovak Academy of Sciences, for valuable remarks on this paper and H. Havlíková for carefully carrying out the numerical calculations.     

РАДИАЦИОННЫЙ ЗАХВАТ НЕЙТРОНА ЯДРАМИ Sc,Fe, Cu,Mo, Cd и La

, . 20–1000 keV Sc, Fe, Cu, Mo, Cd La.

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The radiative capture of a neutron on Sc, Fe, Cu, Mo, Cd and La nuclei

The energies and intensities of the transitions of a compound nucleus, produced by the capture of a neutron, were measured by means of a single-crystal scintillation spectrometer. The region of energies 20–1000 keV was measured on Sc, Fe, Cu, Mo, Cd and L a nuclei.

     

Honeycomb domain structure

A theory is given of a new structure produced when demagnetizing uniaxial single crystals (e.g. magnetoplumbite) in a field normal to thec axis. The experimental results fully support the theory on the assumption that domain structures produced under normal conditions are metastable. Methods are given by which stable structures can be prepared from such metastable ones. On the basis of these results opinions are expressed as to the nucleation of plate and honeycomb structures, produced either by reducing the field from saturation or by cooling below the Curie point.

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, (, ) , c. , , , , , . , . , .

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In conclusion the authors would like to thank C. Novák from the Institute of Technical Physics, Czechoslovak Academy of Sciences, for checking the calculation of the harmonic analysis and Z. Málek and J. Eousek for carefully reading the paper and for valuable remarks.     

ДАЛЬНЕЙШИЕ ИССЛЕДОВ АНИЯ ФИЛЬТРА ДВОЙНОГ О ЛУЧЕПРЕЛОМЛЕНИЯ

, 4, (1954), 53. . .     

Vacuum Einstein spaces with axial symmetry

Four classes of solutions are found to the equations R=–2_{; ;} and g _;=0 in three-dimensional space with metric gdxdx and signature (+ ––), equivalent to the Einstein equations R_ij=0 in a vacuum for the metric . The metric ds² assumes axial symmetry and symmetry with respect to the reflection .Translated from Izvestiya Uchebnykh Zavedenii, Fizika, No. 9, pp. 43–45, September, 1976.     

The connection between low-gradient form of the positive column in oxygen and moving striations

The method of sliding photomultipliers was used to study the connection between two forms of the positive column in oxygen — the so-called low-gradientT-form and the highgradientH-form — and the presence of moving striations in the positive column. It was shown that in theT-form of a positive column striations are always present which move from the cathode to anode with a velocity of several thousand metres/sec. The highgradient form of theH-positive column, on the other hand, is not striated. The non-single-valuedness of the value of the longitudinal electric field in a discharge in oxygen is thus explained by the presence or absence of phenomena of a time variable character.

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— - H - — . , - , /. , , . , , , .

     

Das Verteilungsgesetz der Ferromagnetischen Bereiche vom Standpunkt des Aktivierungsfeldes aus Betrachtet

Zusammenfassung Unter der Voraussetzung, daß das Ahtivierungsfeld für die reversible Bewegung der Blochschen Wände dem Maxwellschen Verteilungsgesetz unterliegt, wird die Entstehung des Maximums der inneren Reibung im Wechselfeld theoretisch erläutert. Weiter wird die Lösung der Differenzialgleichung für die Bewegung einer Blochschen Wand bei gleichzeitiger Wirkung des Wechselfeldes und der Torsionsbeanspruchung gegeben. Die Messung bei einigen Torsionsfrequenzen ermöglicht die Bestimmung gewisser mikroskopischer Konstanten.

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, . . .

     

МОДЕЛИРОВАНИЕ ЭЛЕКТ РОННО-ОПТИЧЕСКИХ СИС ТЕМ С ОСЕВОЙ СИММЕТРИЕЙ П РИ ПОМОЩИ СЕТИ СОПРОТИВЛЕНИЙ

The paper explains the theory of modelling electrostatic fields by a resistance network. The conditions, which the resistance network must satisfy, are derived and the question of modelling electrodes of different shapes is solved. The finished network and the results obtained on it when modelling a jet for a linear h-f accelerator of electrons are described. Particular attention is paid to the influence of a space charge, the modelling of which is an advantage of this method.

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1- , 1964., , .

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Hermiticity of Quantum Observables Versus Commutation Relations

In order to obtain sum rules and spectral representations the Hermiticity property , A = A, of observables is used. It is shown that for certain and the property turns out to be inconsistent with the commutation relations that contain A. The known Schwinger paradox is explained by this inconsistency.     

On the probability of double beta decay

Double beta decay is discussed in relation to parity non-conservation. Two possible ways of neutrino-less double beta decay (allowed and forbidden) are investigated and the half-life of decay is calculated. For allowed transitions we obtain for Ca⁴⁸ an estimatedT1/2=2×10¹⁹ years. The negative results of the experiments by Lukjanov et al., who give the valueT1/2=0.7×10¹⁹ years for the lower limit of the half-life of double beta decay of Ca⁴⁸, cannot therefore be regarded as a definitive solution of the question, whether the neutrino is a Dirac or Majorana particle. Further study of double beta decay, aimed at finding higher values of the lower limit of half-life, are of considerable importance for theory.

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- . - ( ) . ⁴⁸ T1/2210¹⁹ . - . [1] ( - ⁴⁸ T1/2 0,710¹⁹ ), , . - .

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In conclusion the author thanks Prof. I. S. apiro for suggesting this work and help in elaborating it.     

Охлаждение накалива емой проволоки в подз вуковом потоке

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Magnetization coils without iron core for high field intensities

A new theory of rectangular coils without an iron core is described which amends the old one of Fabry and Bitter. It enables us to compute field intensities in coils having very small openings, which the old theory could not do.

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, , , .

     

On surface layers on BaTiO3 single crystals

The possibility of explaining the existence of a surface layer on BaTiO₃ crystals by the presence of Schottky defects in the crystal is investigated. The magnitude of the potential difference between the surface and the interior of the crystal and the thickness of the surface layer, which at temperatures of over 400°C agrees with the measured values, are calculated for the cubic phase from a simplified ionic model.

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BaTiO₃

iO₃ . , 400° .

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In conclusion the author would like to thank Dr. M. Trlifaj and V. Janovec, candidates of physics and mathematics, for valuable remarks.     

Ermüdungserscheinungen der infrarotbestrahlten Silber-Cäsium-Photokathoden

Zusammenfassung In dieser Arbeit werden die Erscheinungen der normalen und anomalen, durch Infrarotstrahlung verursachten und von uns schon früher an diesen Photokatoden beobachteten Ermüdung von Silber-Cäsium-Photokathoden untersucht. Diese Erscheinungen wurden an durchsichtigen sowie undurchsichtigen, durch verschiedene Technologien zubereiteten Photokathoden festgestellt. Es wurden Messungen der Strahlungsintensitäts-, Temperatur- und Spektralverteilungsabhängigkeit der normalen und anomalen Ermüdung durchgeführt. Es werden die Ursachen der Unübereinstimmigkeit im Vergleich mit Arbeiten von De Boer und Teves besprochen. Ferner wurden die Zeitverläufe der Ermüdung bei der Abwechslung der Bestrahlungs- und Dunkelzyklen studiert.

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, , . , . , . . .

     

The elastic coupling between longitudinal and transversal vibrations of isotropic rods I. Rods of square and rectangular cross-section

A new approximate method for theoretically calculating longitudinal vibration frequencies of isotropic homogeneous rods of square and rectangular cross-section is given. We divide a three-dimensional longitudinal vibration into three one-dimensional ones; the coupling between the principal strains in question is assumed to be linear, similarly as in the static case of simple tension. The coupling between the deformations is realized by variable coupling parameters or depending on the order of vibrations (contrary to Rayleigh's correction where Poisson's ratio is the coupling parameter). These parameters are defined by the condition that the corresponding frequency must be minimized (stationary).Up till now Giebe and Blechschmidt [2] have given the best approximate method of calculation. The series of their calculated frequencies corresponds to the measuredones nearly as well as the frequencies calculated by us. The theory described here, however, contains a richer spectrum of frequencies and at the same time explains the frequencies measured in the range of the so-called dead zone, which is the weak point of Giebe's and Blechschmidt's theory.

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I.

. ; , . , ( , ). , ( ). [2]. , , . , , , , . . , .

     

ПРИМЕНЕНИЕ ПАРАМАГН ИТНОГО РЕЗОНАНСА ДЛЯ ИССЛЕДОВАНИЯ РЕАКЦИЙ СВОБОДНЫХ РА ДИКАЛОВ

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The use of paramagnetic resonance in studying the reactions of free radicals

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Type N solutions of the vacuum scalar-tensor field equations

All solutions of the vacuum relativistic scalar-tensor field equations R=–,, are given in the case where the Weyl tensor is of Petrov-Penrose type N. These eight solutions are listed according to the Petrov-Plebaski classification of their trace-free Ricci tensor components and belong to the three classes[T–3S]_[1–1] (R,N), [3T–S]_[1–1](R,N) and [4N]_[2](O,N).