Experimental verification of the theory of the successive production of striations in a glow discharge

The properties of the wave of stratification in the plasma of the positive column in a glow discharge in neon are measured. The measurements are compared with the results of the theory of the successive production of striations and good agreement is found.

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In conclusion the author thanks M. Novák for help in measuring and evaluating the experimental results, and F. Kroupa and V. Krejí for carefully reading this paper and for valuable remarks.     

Microwave relaxation and phenomenological damping in thin films

The relation between relaxation timeT, frequency swept resonance linewidth , and phenomenological damping is given by =2/T=(_x+_y), where _x,y = (H ₀+(N _x,y –N _z ) 4M _s ).N _x,y,z are sample demagnetizing factors,H ₀ is the effectivez-directed static field, 4M _s is the saturation induction, and is the gyromagnetic ratio. This fairly simple but general relation shows that the numerical relation between damping and relaxation at a given frequency can be quite different for in-plane and normally magnetized thin films. For thesame loss processes, so thatT andT are equal, is larger than . For permalloy films at 1 GHz, =15 . In addition, the conventional field swept linewidth, H=/, is simply related to only forN _x =N _y . Both and H are geometry dependent and do not provide an intrinsic measure of the relaxation. These results are confirmed by both resonance and transient response experiments. The large values of for large angle switching may also be partially explained by this analysis because the relevant magnetization motion is due to a demagnetizing field normal to the film plane.Visiting scientist on leave fromRaytheon Company, U.S.A. Supported by the Japan Society for the Promotion of Science.     

Martensitic transformation and change in the lattice periods of methane in the low-temperature region

The study establishes the generality of the fcc-bct martensitic transformation mechanisms in methane and steels in which the martensite phase is in the form of two alternating types of structural domains (a packet of thin twins {110}101). This finding made it possible to decribe the crystallogeometric connection between the - and -phases in methane by the Kurdyumov-Sachs orientation relations and to explain the low-temperature lattice anomalies of -martensite.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 73–78, February, 1989.We thank L. V. Skibina and M. M. Chernik for their useful discussions of the work done in the course of the present investigation.     

Some remarks on variable range hopping—in particular in the quantum Hall regime

An expression for the heat conductivity _xx is derived in the effective medium approximation. Mott type formulas are obtained for _xx and the Peltier coefficient _xx . Using percolation theory in a three-dimensional system the Wiedemann-Franz ratio was found to depend on the temperature like . The Mott type formulas were evaluated in a similar way for a two-dimensional system in the quantum Hall regime within the high-field percolation model. In contrast to previous calculations of the high field hopping conductivity _xx , the results are fully consistent with the experimental data on _xx and the density of states at the Fermi level. Finally, _xx is estimated which together with _xx and _xy =ie ²/h(i=0,1,2,...), determines both thermopower coefficients _xx and _xy .Dedicated to Professor W. Brenig on the occasion of his 60th birthday     

The rotation of bloch walls

A Bloch wall has an integral magnetic moment which is due to the spatial distribution of the magnetic moments of the spin. The external magnetic field thus acts on the wall with a torque, which leads to the rotation of the sub-domains and therefore to deformation of the walls. A theory of this rotation is given and from it a microphysical model of the undulatory surface structure in uniaxial ferromagnets is derived. Experiments performed on magnetoplumbite single crystals fully confirm the theoretical assumptions.

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. , , . , . , , .

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Our thanks go to J. Fousek and Z. Málek who by reading this paper contributed greatly to the clarity of its presentation.     

Quantum mechanics without the projection postulate

I show that the quantum state can be interpreted as defining a probability measure on a subalgebra of the algebra of projection operators that is not fixed (as in classical statistical mechanics) but changes with and appropriate boundary conditions, hence with the dynamics of the theory. This subalgebra, while not embeddable into a Boolean algebra, will always admit two-valued homomorphisms, which correspond to the different possible ways in which a set of determinate quantities (selected by and the boundary conditions) can have values. The probabilities defined by (via the Born rule) are probabilities over these two-valued homomorphisms or value assignments. So any universe of interacting systems, including those functioning as measuring instruments, can be modelled quantum mechanically without the projection postulate.     

A contribution to the theory of ferromagnetic resonance at high power levels

The instability of spin waves at ferromagnetic resonance is discussed. An equation of the stationary state of spin wavesk0 is derived by means of the quantum theory of spin waves. It is shown when discussing this equation that the concept of the critical uniform precession angle may be obtained when using an approximation which neglects the action of spin wavesk0 backward on their own excitation. We believe we are justified in supposing that, due to this effect, a stable stationary state can exist even above the critical amplitude of uniform precession, given by theories up to now.

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. k0. , , k0 . , , , , .

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In conclusion the author thanks G. A. Smolenskij for enabling him to carry out this work in his laboratory. Thanks also go to the theoretical staff of the Institute of Semi-conductors of Acad. Sci. USSR in Leningrad for valuable discussions, especially to A. I. Anselm, V. L. Gurevic and J. A. Firsov.     

Локалъная чувствите лъностъ фотокатодов фотоумножителей

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The local sensitivity of photo-multiplier photo-cathodes

The influence of the non-uniform distribution of the sensitivity of a photo-multiplier photo-cathode on the spectrum shape of the output pulses from a scintillation detector is studied. Methods of scanning the local sensitivity and determining its distribution function are described. The theory was compared qualitatively with measurement on a slow-neutron detector from a mixture of zinc sulphate and boric acid.

     

Single crystal diffraction patterns of germanium. Part II

The rocking curves of Ge (111), (220), (333) for CuK ₁ radiation were measured by means of the triple-crystal diffractometer. Perfect silicon single crystals, cut parallel to the (111) plane were used in the monochromator part of the triple-crystal diffractometer. The results prove the suitability of such a monochromator for studying diffraction patterns.

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. II

(rocking curves) (111), (220), (333) CuK ₁ . , (111). .

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In conclusion the authors thank A. Haruý for preparing the germanium single crystals and they are indebted to V. Smutná and A. Irra for the care with which they carried out various tasks.     

ФОТОЯДЕРНЫЙ ЭФФЕКТ Н А НИКЕЛЕ, МЕДИ И ЦИНКЕ

, - 17,6 , . , (8±4)·10^–23, (7±4)·10^–23 (4±2)·10^{–23 2}. , - .     

Depth distribution of x-rays in electron microprobe analysis

The dependence of the relative intensityk on the thin film thickness has been measured. This dependence has enabled us to verify the Monte Carlo simulation. From the experimentally determined dependence, distributions of X-rays in the specimen ((z) functions) have been derived. It has been found that the intensities calculated by the present Monte Carlo model are always higher than those measured.The authors wish to thank Prof. R. Kuel of the Faculty of Mathematics and Physics, Charles University, Prague, for the measurement of the sputtered thin films thickness.     

Die magnetische Suszeptibilität der ternären Systeme halbleitender Verbindungen

Zusammenfassung Im vorliegenden Artikel wird der Versuch unternommen, die für die Suszeptibilität der binären Systeme zutreffenden empirischen Beziehungen auf die ternären halbleitenden Systeme auszudehnen. Die Richtigkeit der Erwägungen wird an den Systemen Zn-Cd-Sb, In-Ga-Te und an einigen festen Lösungen anderer halbleitender Verbindungen überprüft. Im Artikel wird weiter gezeigt, daß sich im Falle, wenn sich die Suszeptibilitäten der Komponenten des ternären Systems additiv verhalten, zur Berechnung der molaren Suszeptibilität einer festen Lösung die Mischungsregel verwenden läßt, was im Gegenteil in diesem Falle als Kriterium dienen kann, ob zwei den Erfordernissen der Additivität der Suszeptibilitäten der Bestandteile Genüge leistende Stoffe eine feste Lösung oder ein mehrphasiges System bilden.

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, , . Zn-Cd-Sb, In-Ga-Te . , , , , , , , , , .

     

Theory of ferromagnetic resonance line shape in insulators

The paper discusses the absorption of the energy of a high-frequency field by a magnetic sample from the point of view of the interaction of spin waves with photons and spin waves amongst themselves. A general expression for the form of the absorption curve is derived, using the method known from the quantum theory of radiation and assuming very weak fields.

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The author thanks S. Krupika, Candidate of Sciences, for the exceptional interest taken in this work, for advice and a number of helpful and critical remarks.     

The complex conductivity of the plasma of a d-c glow discharge in Ne

In paper [1] Fang derived an expression for the complex conductivity of plasma assuming that the distribution function of the electrons is Maxwellian and the collision frequency is directly proportional to their velocity. Since the assumptions are approximately satisfied in the positive column of a d-c glow discharge in Ne, the applicability of Fang's relation is investigated for this case.

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[1] , . , .

     

The Gelfand-Levitan equation and its application to the scattering of neutrons on protons

The Gelfand-Levitan equation for the kernelP(r, r) (withrr) is formulated and then applied for determining the scattering potential in the scattering of slow neutrons on protons (for the case when the dependence of the nuclear forces on the spins can be neglected and onlys-scattering need be considered). The potentials obtained are the same as the Bargmann ones, found by a different method.

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- P(r, r) ( rr). , ( s- ). , .

     

Studies on the microstructure of phase transitions in two kinds of liquid crystals by PAT and DSC

The positron lifetime and DSC measerments for EBBA and DOBAMBC have been made with heating and cooling clycles. The experimental results show that a shorter lifetime (₁) is essentially independent of temperature while the longer lifetime (₂) and the intensity (I ₂) change abruptly double or triple with temperature. Consequently, the EBBA has only nematic phases while the DOBAMBC has two liquid-crystalline phases (smectic C* and smectic A) with transition temperatures as follows: for EBBA, solid nematic (304.5 K), nematic isotropic (356.5 K), isotropic nematic (356.5 K), nematic solid (301 K); and for DOBAMBC, solid smectic C* (346 K), smectic C* smectic A (357.5 K), smectic A isotropic (389 K). These critical temperatures are in accordance with the transition temperatures measured by DSC. In addition, the difference in the solid-nematic transition temperature in the heating and cooling cycles was also observed. A discussion about the correlation of the observed changes in lifetime (₂) with the changes in molecular orientational order (S) and dielectric anisotropy () is presented.     

Change in primary extinction during decomposition of supersaturated solid solution II. Al-Cu 4% alloy-formation of G.P. zones

The change in integrated intensity of the (200) reflections of a solid solution during the formation of G.P. zones was measured and compared with the change in the character of the diffuse streaks corresponding to them. It was found that the. formation of G.P. zones does not lead to a decrease in primary extinction despite the great changes in the distribution of the copper atoms. It was shown that the formation of a precipitate accompanied by the formation of crystallographically incoherent boundaries greatly decreases the primary extinction.

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. II. 1-u 4%: [. . ]

(200) . . , . , . . , . , , , .

     

Optical constants of thin germanium films

The paper gives the values of the optical constants of thin films of germanium obtained by evaporating germanium in a vacuum onto glass slides in the region of 0·35–0·78 for an index of absorptionk and 0·35–2·5 for refractive indexn. The results are compared with the values obtained by other authors and with the values ofn andk for single crystals. It is shown that these values for thin films and single crystals slightly differ quantitatively but agree fairly well qualitatively, which had not been sufficiently the case in previous papers.

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, , 0,35 0,78 k 0,35–2,5 n. n, k . , , , , .

     

Канал кратковременн ого силъноточного электрического разр яда

, ( 10² sec, , 10⁴ A), .

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Channel of short-time high-intensity electric discharge

By the spatial expansion of the radial cross-section of the channel of the given type of discharge (duration 10² sec and maximum intensity smaller than 10⁴ A)and by measuring some of its electrical quantities information was obtained on its channel and the influences bringing about the forming process.