Investigation of GeS (001)

Various possibilities of the preparation of the clean GeS surface were studied. The LEED pattern of the (001) face of the GeS cleaved in situ exhibits clear ordinary reflections. The dimensions of the surface unit mesh agree well to within experimental error (6%) with the corresponding dimensions of the bulk unit cell.The author wishes to thank Dr M.imeková for performing scanning electron microscopy pictures and Dr K.Jurek CSc. for EDAX measurements. Special thanks go to Dr M.Závtová who called my attention to this interesting material.     

Photoelectric properties of linear oligoaniline derivatives

Dark conductivity and photoconductivity were measured on polycrystalline layers and single crystals of the arylamine type compounds. The photoconductivity process is largely affected by the effects of trapping of the charge carriers followed by their thermal releasing from traps. The activation energy of photoconductivity is determined by the depth of the traps, similarly to the activation energy of the dark conductivity at lower temperatures. At laboratory temperatures and higher ones the activation energy of the dark conductivity is determined by the position of the Fermi level.The author is indebted to Dr B.Sedláek and Dr J.Honzl for their interest, to Dr K.Ulbert for support, valuable discussion, and critical reading of the whole paper, to Dr K.Vacek for discussion and surveying the paper, to Dr M.Tlusáková for sample preparation, to Mr J.Obrda M. Sc. for assistance in measurements of the photoconductivity of single crystals, and to Mrs V.Berdychová and Mrs J.Vaková for technical assistance.     

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.     

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.     

The CNDO-MO study of oxygen impurity states in AlN crystal

Deep levels due to oxygen impurity have been theoretically studied by the quasimolecular approach. The calculation of the orbital spectra was performed using the CNDO/2 method. Some important quantities (transition energies, width of valence band, effective charges etc.) were estimated. The results obtained agree qualitatively well with experimental data but quantitatively are still about 20% in error. Some reasons for the above discrepancy are briefly discussed.The authors are very grateful to Dr. J.Kubátová and Dr. S.Paesová for helpful discussions of the experimental investigations of aluminum nitride and to Dr. J.Pastrák for his interest in this work and discussion of results.     

On ferromagnetic resonance damping in metals

The Landau-Lifshitz damping coefficient is defined in terms of spin-orbital torque correlations in the one-electron model and estimated as a function of the orbital collision frequency. The formal results are compared with previous studies and the results of a numerical calculation for nickel are compared with known experimental data.I would like to thank Dr. L.Hodges for a copy of his thesis and Dr. A. V.Gold, Dr. J. R.Anderson, Dr. V.Dvoák, Dr. Z.Frait and Mr. M.Kolá for valuable discussions at various stages of this work.     

Vavilov-Cherenkov radiation in the biaxial triglycine sulphate crystal

Some properties of the Vavilov-Cherenkov radiation in the biaxial triglycine sulphate crystal have been analysed. The radiation properties have been studied for the cases of protons moving along the main three dielectric axes. The measurements were performed with the 660 MeV proton beam.A quantitative agreement of experiment with Muziká's theoretical calculations on the directional properties was observed. In all the cases a qualitative agreement concerning azimuthal distribution of the radiation intensity of the extraordinary waves of both polarities as well as concerning the polarization properties predicted by Obdrálek's formulae has been obtained.Dedicated to the Memory of Professor . Muziká.On leave from Department of Nuclear Physics, Comenius University, Bratislava, Czechoslovakia.The authors are grateful to Prof. V. P.Dzhelepov, Director of the Laboratory of Nuclear Problems, to Prof. L. I.Lapidus for support of the experiment as well as to Prof. L. M.Belyaev and I. V.Gavrilova (the Institute of Crystallography of the USSR Academy of Sciences) for supplying triglycine sulphate crystals, to J.Obdrálek (Charles University, Prague) for fruitful discussions and helpful advice, to Dr. R.Pose for assistance in obtaining negative colour film, to E.Janikova and R.Janik for great assistance in the experiment.     

Photon counting statistics of superposition of one-mode coherent light and chaotic light consisting of two Lorentzian spectral lines

The approximate photon counting distribution si calculated for the polarized superposition of one-mode coherent light and chaotic light consisting of two Lorentzian spectral lines. Further the exact and approximate third factorial moments of the photon counting distribution are proposed in this case. Also the second factorial moment for the superposition of one-mode coherent light and chaotic light consisting ofn Lorentzian spectral lines is given.The authors thank Dr. Z.Braunerová from Laboratory of Computer Science of Palacký University for performing the numerical calculations and Dr. V.Peinová for some verifying calculations.     

Luminescent properties of A1N activated by europium

The concentration and temperature dependence of emission and excitation spectra was measured on powder A1NEu phosphors. It was shown that A1N: Eu has two luminescent modifications which depend on the activator concentration. At low activator concentration the wide emission band is found in the blue-green region, while at high concentration it is in green region. The excitation spectra of A1NEu consist of wide bands extended from 40×10³ cm^–1 to 22 × × 10³ cm^–1. The emission and excitation spectra are interpreted as transitions between energy levels of Eu²⁺ ions (4f⁷4f⁶ 5d transitions). The structure of the Eu²⁺ luminescent centres and the temperature dependence of luminescence are discussed.The authors thank Dr. M.Polcarová for the RTG measurements and Mrs. I.Míková for the spectral analysis of the A1N: Eu samples. The authors are also grateful to Prof. M.Trlifaj, Dr. J.Pastrák and Dr. J.Kubátová for valuable discussions.     

Macroscopic velocity of ions in a weakly ionized plasma in the crossed fields

Macroscopic velocity of energetic ions from energy spectra measured with electrostatic microanalyzer in the direction along and against the drift was found. It turned out, that in the investigated range of velocities a little below the critical one it is possible to describe the macroscopic motion of ions by the drift theory.The authors wish to thank Dr JanVáa and Prof.Jií Kracík for their interest and support, DrPavel unka for many helpful discussions, Mr J.Dvoák for his technical assistance throughout the work and Mr J.Zubec for manufacturing of the microanalyzer.     

Interferometric measurement of plasma density in the range 1019–1022 m−3

A laser interferometer, operating at the wavelength =0·337 mm suitable for the plasma density measurements in the range 10¹⁹–10²² m^–3 as well as a simple construction of the HCN laser are described.The authors wish to thank Dr. P.unka for fruitful discussions and Dr. J.Musil for the design and construction of the detector.     

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.     

Internal friction in cd+zn alloy single crystals

Internal friction measurements were used for the examination of Cd + Zn alloy single crystals. It was established that the interaction energy between solute Zn atoms and dislocations in basal planes is 0·12 eV.The authors thank Dr. P.Luká, CSc., for valuable discussions.     

Internal conversion of the 84·23 keV transition in170Yb

The conversion coefficient _K=1·48±0·07 and the total conversion coefficient = =8·05±0·2 have been determined by means of the 4 scintillation counter.The authors are obliged to Mrs.Boukalov, Mrs.Vladykov and MissStíteská for the assistance in the elaboration of this paper.     

Corrections to the exponential decay law: Are they observable?

Corrections to the exponential decay law are theoretically expected to be non-zero but very small. A possibility was discussed during the last few years that they could be found experimentally by frequently repeated measurements performed on an unstable system. We give here an estimate of the considered effect for charged kaons in the hydrogen bubble chamber; this estimate shows that it is out of the question to find the corrections in this type of experiment.The authors are indebted to Dr, J.Formánek and Dr. V.imák for helpful discussions and comments.     

The influence of the skineffect on the disaccommodation of the initial permeability

The very sensitive and convenient ac techniques of the disaccommodation measurements in metals are substantially influenced by the skineffect. This influence has been calculated in higher approximations and it is shown that the influence of the skineffect depends not only on the frequency of the measuring field and on the diameter and material constants of the cylindrical specimen but also on the relaxation strength, i.e., on the concentration of relaxators. The second approximation is relatively simple and it can be used for the correction of ac experimental data in most cases, whereas the first approximation which has been used till the present day is applicable only for very small relaxation strength up to about 1%.The author would like to thank Dr. B.esták and Dr. V.Roskovec for helpful discussions.     

On the role of water in some optical properties of alumino-phosphate glasses containing manganese

Optical absorption in broad frequency range (150–5×10⁴ nm) and thermoluminiscence (TL) of the manganese doped alumino-phosphate glasses with two modifiers (Mg, Sr) were measured. It was found that with prolonged melting time the absorption bands at 3·1 m, 5·3 and 5·9 m decrease, new band at 4·2 m appears and that one in UV at about 235 nm increases. Simultaneously the solubility of the glasses in water increases. At longer melted and irradiated glasses the band of electron centres at 210 nm increases while that one of hole centres at 550 nm decreases. These changes are due to the escape of water bonded on two non-bridging oxygens, as well as to the hydrolysis of the melt and oxidation of divalent magnanese. The role of modifiers is also pointed out.The authors would like to express their gratitude to Dr. L.Pajasov á, E.Linhartová and M.Frýbová for careful measurements and PhMr K.ermák for the performing of solubility measurements.     

A computational method of determination of constants of spin Hamiltonian of fine structure ESR spectra

In the case of strong electric crystal fields one cannot use the well-known method of determination of constants of the spin Hamiltonian based on the perturbation theory. This method results in less accurate values of determined constants. In the paper is presented a new method which uses exact numerical diagonalization of the matrix of spin Hamiltonian for determination of constants. The constants determined by this method satisfy the exact solution of the equations for the resonance transitions. This method causes practically no error in the determined constants.The autor would like to thank to Prof. Ing. M.Ráko, Dr. Sc. and Ing. O.Bartko for discussions, and to A.Kotuliaková and G.Petrá for help with the construction of the program.     

On path integrals and relativistic quantum mechanics

A proposal for formulation of relativistic quantum mechanics in terms of path integrals is presented.We are deeply indebted to Dr. M.Petrá for many stimulating discussions.     

The influence of the α′-precipitates on the electrical conductivity of Al-21·8 AT. % Zn alloy at higher temperatures

The applicability of the classical theoretical formulae for electrical conductivity of disperse metallic systems was experimentally verified on the Al-21·8 at. % Zn alloy. This alloy represents a two-phase system in the investigated temperature interval 276–302 °C. The conductivity values calculated for the system consisting of discrete spheres randomly distributed within the continuous matrix were compared with the measured isothermal deviationsR _f from the ideal resistivity, corresponding to the hypothetical continuous solid solution at the same temperature. The temperature 308 °C for the stable solvus was derived by extrapolation ofR _f s values.I would like to express my thanks to Doc. Dr. V.Syneek CSc., for stimulating author's interest in this problem and for providing helpful discussions. The author is indebted to Mrs.Mendlová for careful evaluation of experimental data.