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Two experiments have been performed, concerning the interpretation of the EL process mechanism. The first deals with the behavior of the EL output at liquid helium temperature. The small decrement of the luminescence at 4.2K, demonstrates that the thermal regeneration of electron-hole pairs, invoked in the Fisher model, does not occur in practice. The second experiment, performed by striking the EL comets with an U.V. light spot, shows that a transport of carriers takes place from the comet head towards the tail. Even this experiment disagrees with the Fisher model. On the contrary, both the experiments well support an alternative EL model already proposed by the writers. (Author)

The light distribution along a single EL line is investigated as a function of frequency and amplitude of the applied voltage. It is found that the brightness decreases from the head towards the tail of the comet following the exponential law: B = B(o)e to the minus x/L power; where L, being almost constant versus the frequency, depends linearly on the amplitude of the exciting voltage. Theoretical considerations, founded on a model previously advanced, are developed which show how these new experimental results can be readily accounted for. (Author)

Experiments have been performed on the Thermoluminescence (TL) due to Electroluminescent (EL) excitation of ZnS(Cu) single crystals. Two major glow peaks are found respectively at 35 and 100K, the first being characteristic of EL excitation. The measured activation energies of these glow peaks turn out to be 0.00361 eV and 0.0931 eV and the kinetics order approximately 0.5 and 1. The integrated light intensity of the first glow peak overcomes that of a single EL brightness wave at the same voltage by a factor of about 10,000. With reference to the EL model previously put forward by us these experimental results can be accounted for satisfactorily. The first peak in fact appears due to electrons trapped at the broken bonds lying along the EL defect and the second peak is produced by electrons scattered during the direct bias injection and successively trapped in the bulk ZnS. (Author)

A series of experiments on the electroluminescence (EL) featured by AgCl at liquid nitrogen temperature. The specimens used were single crystals of unintentionally doped or Mn doped AgCl, either as grown and cut, annealed, plastically deformed, or previously irradiated with UV light. The current vs voltage and the brightness vs voltage characteristics were investigated, as well as the topography of the light pattern at low magnification. The results obtained, described in a detailed way in the text, confirm and extend the little already known about the EL of silver halides. Definite differences are found with respect to the case of the Destriau effect exhibited by ZnS electroluminors. (Author)

A novel model of the Destriau effect (ac EL in ZnS(Cu)) is presented that looks capable of interpreting in a consistent way all the principal experimental features of EL. This result is obtained through consideration of the semiconducting properties of definite partial dislocations bordering stacking faults in hexagonal structure basal planes. After a thorough critical survey of existing theories, the crystal defect spoken of is described and its properties illustrated, showing how they lead to the occurrence of the Destriau effect. (Author)

The paper discusses results of measurements about the time dependence of the monochromatic components of the light emitted by Electroluminescent ZnS single crystals, Cu activated, subjected to a sinusoidal voltage. The light was analyzed with a spectrometer and its time dependence was digitally recorded using a time-to-pulse height conversion technique. The light of two crystals, one (labelled A) exhibiting blue and green EL, the second (labelled B) exhibiting blue, (very weak green) and red EL, was analyzed at 77 degrees K. Both with respect to the exciting voltage and to each other the spectral components of crystals A and B appear nearly 'in phase', although small time lags, of the order of 0.1 period, different for each component, were actually measured. Between the alternances of the exciting voltage the light does not fall to zero, the relative importance of the continuous light pedestal being different for the various spectral bands. No obvious relationship, however, with the decay times has been found. These results are compared with the few data available from the literature and their relevance as to the mechanism of the EL is briefly discussed. (Author), See also Part B, AD-662 625.