I. Chudáček

The kinetics of the triboluminescence of zinc sulphide I

The paper proposes a two-stage model of the time dependence of triboluminescence as a function of the magnitude of the applied exciting pressure; it is confirmed by the results of measuring the time dependence of triboluminescence. The decay of triboluminescence excited by a blow and by friction is measured. The spectral dependence of triboluminescence in ZnS-Mn was found. It has the same form as in photoluminescence and in addition contains maxima corresponding to the electric discharge in air.

The influence of pressure on recombination centres in piezoelectric luminophores

The present paper shows that a recombination centre of the Cu+-[S−] type in the ZnS lattice has “local” piezoelectric properties. On the basis of this fact some phenomena of triboluminescence are explained and a periodic generator of light is proposed.

Some physical properties of ZnS crystals grown from the vapour phase

Wurtzite-type crystals with wide regions of high purity and good optical properties have been grown in a few hours by an improved flow method. Dislocations have been found to be mainly arranged inside isolated striation regions where a weak green fluorescence and phosphorescence has been observed. Under bending deformation the crystals show a plastic behaviour that is not directly correlated to the mean dislocation density of the samples. Rupture has been found at about 103 kg/cm2.

Energy spectrum of α particles emitted from sources of different thicknesses

The shape of the energy distribution of all α particles emitted by sources of different thicknesses was investigated. The energy distribution N(E) dE found can be expressed by a semi-empirical formula, which on the whole agrees with experiment. The source of α particles was uranium oxide U308.The energy distribution was measured with AGFA K2 nuclear emulsions 200 μthick. Altogether 3,602 trajectories of α particles in the nuclear emulsions of five plates were measured.

Drift mobility of holes in some photoconductive polymeric structures in the glass transition region

SummaryDrift mobility of holes in poly(N-vinylcarbazole) PVCA and its mixtures with poly(N-epoxypropylcarbazole) PEPCA was measured in a broad temperature range. Sensitivity of charge transport to the dynamic phenomena in the glass transition region was observed. Release of molecular motions near the glass transition temperature causes broadening of the transit time distribution and reversible decrease of the activation energy of drift mobility.

Luminescence of poly(N-vinylcarbazole) in the solution and solid state

Fluorescence spectra of poly(N-vinylcarbazole) have been studied as a function of various environments and temperature. Fluorescence spectra have been excited with UV light from 200 W Xenon lamp or with second-harmonics of a pulsed ruby laser. Polymer films and powders show exclusively excimer fluorescence at room temperature. At high intensities of excitation the observed fluorescence spectra have a weak quasiperiodic structure.

Intensitive dependence of luminescence and photoconductivity for the electron-electron, electron-exciton and exciton-exciton interactions

Analytical solutions of the equations of kinetics were found for stationary states at specific external conditions, especially for high excitation intensities. This allowed us to establish analytical expressions of the lux-lux and lux-ampere characteristics and use them in analyzing the type of recombination mechanism, which corresponds to certain dependence of luminescence or photoconductivity on the excitation intensity.

Radiothermoluminescence curves of polymeric materials in the region of releasing frozen molecular motions: 1. The shift of radiothermoluminescence maxima resulting from variation cooling rate

SummaryThe glass transition peak of radiothermoluminescence (RTL) curves in a statistical butadiene — styrene copolymer shows a distinct dependence on the cooling rate prior to irradiation. The higher the cooling rate, the lower the intensity and the temperature of the RTL glow curve maximum. These experimental findings are in accordance with a recently proposed theory of RTL in terms of glass transition phenomenology.

Temperature dependence of the intensity of fluorescence of poly(n-vinylcarbazole) films

SummaryThe fluorescence spectra of thin films of poly(N-vinylcarbazole), PVCA, were measured at temperatures between 103 K and 535 K by constant excitation light intensity. Below 300 K, the corrected spectra were divided into bands belonging to different emitting species of PVCA. Temperature changes of the intensity of fluorescence of the two main excitation energy traps in PVCA are discussed using the simplified kinetic model of Johnson. Local anomalies on the curves of intensity of excimer fluorescence versus temperature measured at constant wavelength reflex the γ- and δ- relaxation regions in PVCA.

Behaviour of a Thermoplastic Charged Surface in the Vicinity of the Softening Point

SummaryConditions of formation and stability of „frost effect” on layer of polystyrene with a very thin surface film prepared by crosslinking in an electric discharge were studied for different starting electric potentials of the surface. It was found that during the rise of the temperature of the sample the surface potential falls and a stable frost exists in a certain temperature interval. The explanation of the observed phenomena is based on Cressmans expression for electrocapillar effect and on effects connected with dilatation of the basic layer and artificial film on its surface.