The distribution of silicon in single crystals of Fe-Si alloys grown from the melt

A method of measuring the distribution of the silicon concentration in single crystals of Fe-Si alloys was elaborated on the basis of determining the relative Seebeck coefficient of these alloys with respect to the reference metal. The dependence of the relative Seebeck coefficient of Fe-Si alloys versus copper on the concentration of silicon was measured in the range of 2–12 weight % Si. The distribution of silicon in a series of single crystals of Fe-Si alloys grown from the melt was also determined.The author thanks the members of the department of the mechanical properties of solids of the Institute of Physics, Czechoslovak Academy of Sciences, and especially the head of the department, Ing. B. esták, CSc., for making it possible to prepare the single crystals and for discussion of the paper. He also thanks Dr. M. Matyá, CSc., for valuable remarks and Ing. Z. Kubita for passing on his experience in the use of the measuring method. He is indebted to members of the analytical laboratory of the State Research Institute for Materials Protection, the analytical laboratory of the Metals Research Institute and the chemical department of the. Institute of Physics, Czechoslovak Academy of Sciences, for careful analyses of the samples.     

Microhardness and structure transformations of Al-15 at.% Zn alloy aged at elevated temperatures

The microhardness changes on ageing in single crystals of the Al-15 at.% Zn alloy at the temperatures of 201 °C and 222.5 °C are presented in this paper. The gradual decomposition of the solid solution was simultaneously studied from X-ray diffraction measurements. The results reveal the mutual correlation between the individual structural stages and the microhardness of this alloy.Cukrovarnická 10, Praha 6, Czechoslovakia.In conclusion the authors wish to express their thanks to Doc. Dr. V. Syneek CSc. for many stimulating discussions, to Ing. J. Laek CSc. for the careful chemical analyses of the investigated alloy and to Ing. P. Bartuka CSc. for the private communication of his results from the electron-microscopic study. Our thanks are also due to Mr. Z. iký and Mr. J. Bauer for assistance in measurements.     

HF heating of a plasma column at frequencies below the electron cyclotron frequency

Dispersion of waves, excited by the helical structure in a plasma column and the heating of a tail of the electron distribution function is studied at frequencies below the electron plasma and the electron cyclotron frequency.We wish to thank Dr. R.Klíma for valuable discussions and Dr. J.Lacina and Mrs. P.Jaroová for the computational work. We also thank Dr. L.Bárdo, Dr. L.Kryka and Dr. G. L.Khorosanov from Sukhumi Institute, USSR, for their help during different stages of the experiment. We are indebted to Mr. J.Dvoák, Mr. F.Jiránek and Mr. B.usta for their expert technical assistance.     

Absorption edge and photoconductivity of CuPbAsS3 Single crystals

Absorption curves of CuPbAsS₃ have been measured in the temperature range 90÷300 K. Their analysis leads to conclusion that the absorption edge of CuPbAsS₃ is due to allowed indirect electronic transitions between the valence and conduction band extrema. The forbidden-gap width, its temperature dependence and energies of three interacting phonons have been determined. The temperature shift of the photoconductivity band is in agreement with that of the forbidden gap in CuPbAsS₃.Leninovo nám. 565, Pardubice, Czechoslovakia.The authors are indebted to Dr. Vl. Syneek and Mrs V. Míková from the Institute of Solid State Physics, Czechosl. Acad. Sci., Prague for advice and help in orientation of prepared crystals.     

Dispersion relations for forward pion-pion scattering and their consistency with Wolf pion-pion phase shifts

It is shown that the Wolf pion-pion phase shifts are in reasonable agreement with dispersion relations for forward scattering. The extent to which the inaccuracies of the experimental data might modify this agreement is examined.At attempt is made to explain some discrepancies which arise probably from too broad a -meson peak.The author is indebted to Dr. M. Petrá for valuable discussions, to P. Bóna for help with some calculations and to Dr. J. Mikloko from the Computing Centre of the Slovak Academy of Sciences for programming and computation. He is also indebted to Dr. G. Wolf and to Dr. F. Meiere for sending a copy of their papers prior to publication.     

Mathematical models for quantum point-contact spectroscopy

We sketch here two mathematical models intended to describe the point-contact spectroscopical experiments. A new item is added to the list of recently discovered applications of the self-adjoint extensions theory.The paper represents an extended version of the lecture given by one of the authors at the 8th Congress of IAMP, Marseille, July 1986.On leave of absence fromNuclear Physics Institute, Czechosl. Acad. Sci., 250 68 e near Prague, Czechoslovakia.On leave of absence fromNuclear Centre, Charles University, V Holeovikách 2, 180 00 Prague, Czechoslovakia.     

The electron paramagnetic resonance in reduced BaTiO3 crystals

The electrcn-spin resonance of reduced BaTiO₃ crystals, which was studied by Z. roubek and K. d'ánský [Czech. J. Phys.B 13 (1963), 309], is interpreted as the resonance of the Ti³⁺ ion. The facts which favour this interpretation are discussed. The distortion of the oxygen ions surrounding the Ti³⁺ ion has been taken into account in order to explain the measured electron paramagnetic resonance spectrum. Considering the crystal-field model of C_4v point-group symmetry, the Stark energy-level separations of the Ti³⁺ ion and the values of theg factors are calculated.The authors would like to thank Dr. E. imánek for many very helpful discussions and Dr. H. Arend for helpful comments.     

Thermal conductivity of semiconducting amorphous CdGeAs2

The thermal conductivity of amorphous semiconducting CdGeAs₂ was studied between 100 and 300°K. The Debye model was used for the calculation of the mean free path of phonons which was found to be 10 Å at 300°K and was related to the basic structure units of amorphous CdGeAs₂.Thanks are due to Mrs. J. Beránková, Mr. J. Kapar and Mrs. J. Trepeová for the preparation of the amorphous CdGeAs₂ used in this work and for the measurements of the thermal parameters, and to Dr. J. urek and Dr. S. Kolník from the College of Transport Engineering, ilina, for the sound velocity measurements.     

Optical behaviour of cobalt and nickel ions in different media

The absorption and diffusion of different solutions and crystals of NaCl and KCl containing bivalent cobalt and níckel ions were measured. The kinds of complexes are determined from the results and their importance in the luminescence process is discussed.The experimental part of this work was completed in December 1961 during his stay in the Inst. Sol. State Physics, Prague.The authors would like to thank Dr. J. Trnka, M. Lébl and J. Kunzl, Dr. J. Dolejí and M. Závtová for their effective help in preparing the samples and valuable discussions and K. Listoová for carrying out some of the experiments.     

On the effect of trapped particles in the regime of cyclotron resonance

The motion of particles in a finite amplitude wave, propagating obliquely to the homogeneous magnetostatic field is discussed. As follows from simple integral properties, in the neighbourhood of Doppler-shifted cyclotron resonance similar trapping effects appear as in a plasma without magnetostatic field. Consequences of this trapping are discussed, in particular, the possibility of a strong absorption of the wave, and the origin of stochastic instabilities caused by the perturbation of an effective trapping potential and leading to the acceleration of particles.The author is indebted to Dr. R.Klíma, Dr. J.Lacina and Dr. P.unka for interesting discussions and to Dr. .Körbel, Mrs. P.Jaroová and Mrs. A.Harmáková for numerical calculations.     

Effect of structure transformations on the microhardness of Al-15at.% Zn alloy

The ageing of single crystals of Al-15 at. % Zn alloy was studied at the temperature of 205 °C by X-ray diffraction and by measurement of microhardness. A close correlation of individual structure stages with microhardness was found on ageing the alloy.In conclusion the authors would like to express their thanks to Doc. Dr. V. Syneek CSc. for helpful discussion, to Ing. J. Laek CSc. for the careful chemical analyses of the investigated alloy and to Mr. Z. iký and Mr. S. Pazour for assistance in measurements.     

The structure of the nucleon in bootstrap theory

On the basis of the self-consistency theory and the bootstrap dynamics the N + N form factor with one nucleon off the mass shell is calculated in the static model. It is shown that this form factor is an analytic function with analytic properties prescribed by the postulates of S-matrix theory. In addition to the correct analytic properties the form factor fulfils the unitarity condition if and only if certain relations among the meson-baryon coupling constants and among the masses of the baryons are fulfilled. The required ratios of coupling constants are the same as those derived by Chew and by Abers et al. in their static bootstrap model. Moreover the new condition for the mass of -resonance is obtained here.The author would like to thank Dr. M. Petrá, M. Dubec and J. Piút for interesting discussions.     

The effective mass of holes in CdSb from reflectivity measurements

From the measured reflectivity near the plasma edge the effective mass of free holes in Ag-doped CdSb was determined. In the studied concentration rangem _b ^* >m _a ^* >m _c ^* is valid. The dependence of the effective mass on the concentration of free holes indicates a strong non-parabolicity of the bands.The authors wish to thank Dr. B. Rheinländer for discussions and information about his results before publication. Mrs. D. Vaková carried out the measurements on UR-10 Zeiss, Mrs. V. Míková prepared the single crystals, Mr. J. Kapar oriented them by X-ray diffraction and Dr. L. Satoura determinedN and. The authors thank them for their help.     

The character of cyclotron instability of hydromagnetic waves

The method of energy balance is used for calculating the growth rate of hydromagnetic waves ( _H in the regime of a cyclotron resonance. The HM waves are propagated at an angle to the external magnetic field. A tenuous beam of charged particles with a finite Larmor radius penetrating through a cold plasma is assumed to be responsible for the cyclotron instability process.The author is grateful to Assoc. Prof. Dr. A. Hruka CSc. for helpful discussions and remarks concerning the problem. He is also indebted to Mrs. E. Lomecká for the graphical work.     

The gauge invariance,kinematical singularities and the electro- and photopion production amplitudes

The kinematical singularities connected with the gauge invariance are considered and the conventional sets of invariant amplitudes discussed. A new set of invariant amplitudes for electro-production of pions on nucleons is proposed, which contains the transversal subset of photo-production amplitudes, is free of kinematical singularities and more convenient for practical calculations.I would like to thank Dr. M. Petrá for a valuable discussion on some points, Dr. P. Lichard and Dr. J. Piút for useful remarks and Dr. F. A. Berends for a valuable correspondence. I am also indebted to Prof. Moorhouse for drawing my attention to some important papers and sending me a preprint of one of them.     

Some properties of the gas discharge in a magnetron geometry

The discharge in a magnetron geometry was experimentally investigated. At pressures less than 10^–2torr a high-voltage discharge (similar to corona discharge) burns, which discontinuously turns into glow discharge when the pressure is rising. Magnetic field changes the glow discharge in a similar way as the rising of pressure does (the cathode regions are getting shorter, etc.). The pressures and magnetic fields were found in which the positive column occupies 3/4 of the discharge space (gap distance 4 cm) and where an electric field 100 V/cm can be measured.The authors wish to thank Dr. P.unka and Dr. V.Kopecký for a valuable discussion and J.Dvoák and A.Kapar for technical assistance throughout the measurement.     

A simple model of thin-film point contact in two and three dimensions

We treat a free spinless quantum particle moving on a configuration manifold which consists of two identical parts connected in one point. Most attention is paid to the three-dimensional case when these parts are halfspaces with Neumann condition on the boundary; we also discuss briefly a more general boundary conditions. The class of admissible Hamiltonians is constructed by means of the theory of self-adjoint extensions. Among them, particularly important is a two-parameter family whose elements are invariant with respect to exchange of the halfspaces; we compute the transmission coefficient for each of these extensions. We discuss also the motion on two planes considered in our recent paper, obtaining another characterization of the admissible Hamiltonians. In conclusion, the two situations are compared as models for point-contact spectroscopical experiments in thin metal films.On leave of absence fromNuclear Physics Institute, Czechosl. Acad. Sci., 250 68 e near Prague, Czechoslovakia.On leave of absence fromNuclear Centre, Charles University, V Holeovikách 2, 180 00 Prague 8, Czechoslovakia.     

Influence of Ge and Ag impurities on the thermal conductivity of semiconducting amorphous As2Se3

The thermal conductivity of amorphous semiconducting As₂Se₃ is studied in the temperature range from 100 to 300°K and the influence of germanium and silver impurities is shown. The mean free path of phonons is determined and the observed change of the thermal conductivity is explained by the change of the velocity of sound in amorphous As₂Se₂ containing germanium.Presented by L. toura at the Meeting on Electronic Structure, Optical and Transport Effects in Amorphous and Liquid Semiconductors, Prague, May 1965.The authors are indebted to Dr. J. urek and Ing. I. Turek from the Department of Technical Physics of the College of Transport Engineering in ilina for measuring the velocity of sound in the investigated materials and to Mrs M. Kaparová and J. Trepeová for their help in the experimental work.     

Photostructural changes in some ternary Ge-Sb-S chalcogenide layers

The changes of optical transmission and of the index of refraction were studied in flash evaporated Ge-Sb-S layers. Photobleaching, photodarkening and photoinduced crystallization were observed depending on the composition of layers. The effects are qualitatively explained using the idea of photoinduced atoms and/or chemical bonds rearrangement.Spolená laborato VCHT a FZÚ SAV, Leninovo n. 565, 532 10 Pardubice, Czechoslovakia.We are very grateful to Dr. V. Hulínský, University of Chemical Technology, Prague, for scanning microscope measurements.     

States and homomorphisms on the Pták sum

Summing of a Boolean algebra and a quantum logic has been defined by P. Pták and studied by, e.g., V. Jani, Z. Rieanová, O. Nánásiová, and C. A. Drossos. It was shown that there is a special case when this structure is a direct product. Drossos has studied the connection between this structure and a Boolean power. In this paper we investigate the conditions when the Pták sum is a free product and when the connection is between the center ofL and the structure of states onBL.