On the mechanism of rendering visible dislocations on the surface of iron crystals by anodic dissolving

The paper contains further results of studying dislocations rendered visible by anodic dissolving on the surface of single crystals of alpha-iron. The influence of the crystallographic orientation of the surface is investigated, the effect of carbon is confirmed and the anodic process is studied. The mechanism of dissolving of the crystal is given and a new more suitable method of rendering dislocations visible is derived.

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The author thanks F. Kroupa and J. Hejduk for critical remarks and discussion.     

New derivation of Bardeen-Shockley formula for mobility of electrons in homopolar semi-conductors

The Bardeen-Shockley formula for the mobility of an electron or hole in a homopolar semi-conductor is derived in a different way to that in which its authors obtained it. The interaction energy of the electron with the acoustic lattice oscillations is derived in an original way. A new possibility for determining the energy gap is given.

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Wavelength distribution of X-rays in the focus of a monochromator and an estimate of the influence of this distribution on precision measurements of lattice constants

Wavelength distribution in the focus of a Johansson type monochromator is computed assuming the tube focus emissivityG(), reflection curveR() and wavelength distribution of the incident radiationJ(-₀) are known. It is shown e.g. that the centre of gravity may be shifted in accordance with the position of the crystal on the focal circle which may considerably influence precision measurements of lattice parameters.

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, G(,) R() J(-₀) . , , , .

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The author is grateful to Z. Hemanová for carrying out all the computations very carefully.     

Stationary states of an electron in the field of a hole in an ionic crystal

An approximate solution is given of the Schrödinger equation for S-states of an electron in the field of a hole, when the potential energy of the electron has the form — e²/r [1+exp (–qr].

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s- , –e²/r [1+exp (–qr].

     

On the electroluminescence of powdered zinc sulphide layers

The experimental study of the dependence of the electroluminescence brightness on the voltage confirms the correctness of the mechanism of electroluminescence, based on impact ionization in parts of the crystal where the electric field is concentrated. A study of the photoluminescent and electroluminescent spectra of phosphors containing two activators (copper and an element of rare earth) permits the determination of the magnitude of the volume of the crystal in which electroluminescence occurs. A study of the influence of the stored light sum on the brightness of electroluminescence and a study of the rate of growth of the variable and constant components of electroluminescence point to the fact that the excitation is transferred from the region of field concentration to the whole volume of the crystal.

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The change in primary extinction during decomposition of a super saturated solid solution 1. System Al-Ag

On the basis of the correlation of diffraction data (intensity and width) of a precipitate with the intensity of reflection of a matrix solid solution it is shown that the change in primary extinction during the decomposition of a solid solution of Agin Alis caused by the precipitation of the phase Ag₂Aland not by the production of lattice defects (zones, stacking faults).

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I. Al-Ag

( ) , Ag Al Ag₂Al, ( , ).

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Reported in part at the VIth Scientific Technical Conference on the Application of X-rays held in Leningrad in 1958.

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The author thanks M. Mikovský for preparing the single crystals of the alloy Al-Ag having a high primary extinction and J. Laek and Prof. J. Bedná for carefully checking their homogeneity and chemical composition.     

Three variations in the intensity of cosmic radiation in the first half of 1958

The time courses are given of three variations in the intensity of cosmic radiation, which occurred in the first half of 1958. The measuring apparatus is described and the energies of the particles recorded a reestimated. The paper is the partial result of systematic measurements of the intensity of cosmic radiation carried out in Czechoslovakia in the International Geophysical Year.

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1958

, 1958 . . , .

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The authors heartily thank the Institute of Geomagnetism in Krasnaja Pachra, near Moscow, and especially its director, Prof. M. B. Pukov, and Dr Ju. M. Kopylov for the neutron counters.The authors wish to thank Prof. V. Petrílka, corresponding member of the Czechoslovak Academy of Sciences, and Prof. L. Jurkiewicz, from the Academy of Mining and Heavy Industry in Cracow for help in the work and Academician J. Novák, who made possible the numerical evaluation of the data in the Mathematical Institute of the Czechoslovak Academy of Sciences. Especial thanks go to F. Pilát and B. Slavík for their great help in setting up the apparatus and to all colleagues who took part in the measurements.     

On the problem of the permittivity dispersion of barium titanate

The complex permittivity of multidomain single crystals of BaTiO₃ was measured in the decimetre and centimetre wave bands and it was proved that in this frequency region there is dispersion of the permittivity. Apparatus for measuring the permittivity of substances with a high is described and the influence of the inhomogeneity of the field in the sample on the characteristics of the cavity resonator is calculated. Present theories of the high-frequency properties of BaTiO₃ are discussed from the point of view of the experimental results.

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BaTiO₃ , . . BaTiO₃.

     

On the energy balance in the optics of metals

On the basis of the boundary conditions of the electromagnetic theory an explicit calculation of the absorption in a thin metallic film was carried out with the result that transport and interference components were found to exist. By applying the method to a simple metal-dielectric boundary the physical interpretation was given of the energy balance, which had hitherto been regarded as unclear. It was also explained why the reversibility principle fails when applied to a metal-dielectric boundary.

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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 application of the thermodynamics of irreversible processes to welding arcs

The self-regulation of an inert gas shielded metal welding arc is dealt with briefly. A thermodynamic equation is derived for the self-regulation of such an arc.

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Mikrophy'sikalische Vorgänge,die die Entstehung der Schnellen Schichtungswellen in der Neonglimmentladung bedingen

Zusammenfassung Im nachstehenden Artikel werden mikrophysikalische Vorgänge behandelt, die das Auftreten schneller Schichtungswellen in Neonglimmentladungen veranlassen können. Es werden sowohl die qualitativen Abhängigkeiten, als auch die ziffernmäigen Werte der Parameter der Schichtungswellen mit den charakteristischen Gröenwerten der in diesem Entladungstypus vor sich gehenden Vorgänge verglichen. Auf Grund der vorgenommenen Vergleiche kann gesagt werden, da die Relaxationszeiten der schnellen Wellen durch die Diffusionslebensdauer der atomaren, bzw. molekularen Ionen gegeben sind.

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Zum Schlu danken wir F. Kroupa und V. Krejí für die aufmerksame Lesung der Arbeit und wertvolle Hinweise.     

Bunching phenomena during electron injection into the betatron

Under favourable conditions electrons injected into the betatron give rise to high-frequency oscillations. An experimental investigation of the properties of the oscillations is presented, in which new experimental material is added to an earlier paper [1] and the hypothesis regarding the nature of the oscillations is corrected.The oscillations are due to azimuthal bunching of the injected or captured electrons. The bunching is caused by a regenerative amplification of space-charge density fluctuations. The amplification is produced by the negative mass instability mechanism theoretically investigated by Nielsen, Sessler and Symon [2] and Kolomenskij and Lebedev [3].Bunching of the injected electrons is the primary cause of the capture of electrons injected into a static or slowly varying magnetic field. Bunching of the captured electrons represents a limitation in the magnitude of the capturable charge.

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, I.

, , . , [1] . . . , [2] [3]. , . .

     

On the theory of permeability disaccommodation in an alternating field

Néel's theory of diffusion magnetic after-effect is used to show that the disaccommodation of the initial permeability in an alternating field of sufficiently high frequency is equal to the disaccommodation determined by the ballistic method.

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, , .

     

The quantum efficiency of the internal photo-electric effect in indium antimonide

A method is described for measuring the relative quantum efficiency of the internal photo-electric effect in semi-conductors by simultaneously measuring the photo-magnetoelectric and photo-conductive effect. The results of measurements on indium antimonide are given. The quantum efficiency begins to increase if the energy of the photon exceeds 0·47 eVat room temperature. The quantum efficiency as a function of the energy of the photon is analysed on the basis of the conception of impact ionization and it is shown that a study of the structure of this curve can supply information on the, band structure of a semi-conductor in the region of high energies of electrons and holes.

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. . , 0,47 eV . , .

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The authors thank M. Závtová and M. Vantuchová for efficient help with the measurements, K. mirous and V. Vrchovská for preparing the material, E. Antoník for critical remarks and M. Matyá and A. Müller for determining the constants of the material.     

The basic equations of the dynamics of the continuous distribution of dislocations III. special problems

The basic equations of the dynamics of the continuous distribution of dislocations analogical to Maxwell equations are derived in a series of papers [I, II, III]. The analogy of the elastic and electromagnetic fields is analyzed. In part [III] some special problems are discussed, such as the density of the forces acting on the dislocations, the energy dissipation during the movement of dislocations, which is expressed by an equation analogical to Ohm's law. The equations derived in the previous parts in four-dimensional symbolics are considered in the three-dimensional differential and integral form. It is found that in special cases the relations become the known ones of elastodynamics, hydrodynamics and the static theory of the continuous distribution of dislocations. It is found that Kröner's method of integrating the equations of the dislocation field by means of so-called incompatibility tensors is analogical to the integration of the Maxwell equations by means of Hertz vectors. The analogy between the elastic dislocation field and the electromagnetic field is discussed in detail.

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III.

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Two-barrier detector

The paper describes the principle of a detector with two opposite surface barriers and the experimental verification of its functioning. The detector permits double the effective depth to be attained on the material with a given bias voltage. The principle of opposite barriers also permits a reduction in the system of dE/dx andE detectors to one detector.

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. . dE/dx E .

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The authors thank A. Irra for carefully preparing the plates, K. Putz and J. imková for very effective help in measuring on the cyclotron and the members of of the cyclotron staff for their cooperation.     

A note on the Watanabe theory of weak interactions

It is shown that according to the Watanabe theory of weak interactions a resonant scattering of electrons by protons must take place. The resonant energy depends on the massm _B of the intermediate boson. Form _B=2300m _e this energy is about 213 MeV in the centre of the mass system (c. m. s.). The energy width at resonance is 1·4 MeV.

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, . , , . _{m B}=2300_{m B} , 213 MeV -. 1,4 MeV.

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The author would like to thank Professor V. Votruba for suggesting this note and for valuable advice and help during the work.     

Die Energiezufuhr von Einem Longitudinalen Wechselmagnetfeld an Ein Torsionspendel mit Ferromagnetischer Aufhängung

Zusammenfassung In der vorliegenden Arbeit werden einige Ergebnisse, die an ferromagnetischen Proben erhalten wurden, beschrieben. Verwendet wurde Kupferdraht, auf welchen Nickelschichten von verschiedener Dicke niedergeschlagen wurden. Die Proben zeigen, daß dabei die innere Reibung im magnetischen Wechselfeld unter den Wert, der der magnetischen Sättigung entspricht, fallen kann, und daß am Torsionspendel unter bestimmten Umständen erzwungene Schwingungen entstehen.

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Two-quantum annihilation of polarized positrons

The cross-section for the two-quantum annihilation-in-flight of partially polarized beams of particles, obtained by using the polarization density matrix, is given. The formula includes the special results of L. A. Page [1]. The annihilation of a longitudinally polarized positron with a transversally polarized electron is discussed. Computations are made in a centre-of-mass system with summing over photon polarizations.

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Abbreviated version of a diploma-thesis for the degree graduate physicist.

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The author wishes to express his sincere gratitude to Professor V. Votruba and Dr. L. Valenta for suggesting this work and for many helpful discussions and criticisms.