Edge cathode luminescence of zinc-selenide single crystals at high levels of excitation

Investigating cathode-luminescence spectra over a broad range of temperature at high levels of excitation (G 10²⁷ cm^–3 · sec^–1) permits the establishment of the experimental conditions for the observation of a multiplasmon structure in studying electron-hole plasma of zinc-selenide single crystals.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 69–73, July, 1989.     

Luminescence of mixed crystals of silver halides at high excitation densities

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 5, pp. 826–831, November, 1991.     

The temperature dependence of the edge emission of GaSe single crystals at high excitation levels

The temperature dependence of five edge emission lines of GaSe at high excitation levels has been investigated by using the second harmonic of a neodymium-glass laser. The following lines were indentified at 77.3K:hv_B = 2.102 ± 0.002 eV, annihilation of free excitons; hv_C = 2.082 ± 0.003 eV, Auger recombination of free excitons; hv_D = 2.072 ± 0.003 eV and hv_E = 2.055 ± 0.004 eV, annihilation of free excitons with emission of optical phonons (LO₁ = 31 meVandLO₂ = 45 meV, respectively); hv_G = 2.036 ± 0.004 eV, radiative recombination at indirect transition with emission of LO₁ phonons.     

Exciton system heating in ZnSe single crystals under laser excitation

The way to determine the effective temperature of the excitonic system from the study of the edge luminescence high energy region is motivated. Experimental data on the exciton heating in ZnSe single crystals under laser excitation are presented. The effective temperature of excitons T_x has reached 158 K at the lattice temperature T_L = 77 and the peak excitation intensity 2.7 MW cm^?2 (hv₀ = 3.50), while the excess temperature of the excitons (T_x ? T_L) increases as a square root of the pump intensity. Exciton-hot-electron, exciton-hot-photon, exciton-exciton interactions and excitonic Auger process are considered as possible causes of the exciton system heating.     

Luminescence of rare gas crystals at high excitation densities for VUV laser applications

Exciton densities of the order of 10¹⁸ cm^–3 are generated in 0.1–0.3 mm thick surface layers in an area of 10×20 mm² of optically clear rare gas crystals. The quantum efficiencies at 126 nm (Ar), 145 nm (Kr), and 172 nm (Xe) remain near 0.5 even for the highest excitation densities. The corresponding gain coefficients of 2.6 cm^–1 (Ar) to 18 cm^–1 (Xe) exceed those of high pressure gas lasers by a factor of 20. Stimulated emission is inferred by observing the line narrowing, the dependence of intensities and time courses on excitation density and amplification measurements. The net gain coefficient is reduced however to 0.5–1 cm^–1 by transient absorption of excited centers and scattering by irradiation induced defects. The results are analysed by a system of rate equations for the excitation, relaxation, quenching, and amplification processes. A peculiar temperature dependence of the quantum efficiencies and time courses is attributed to electron trapping at grain boundaries.     

Luminescence of AgCl crystals at room temperature after ruby laser excitation

Emission spectrum of pure AgCl crystals at room temperature after ruby laser excitation was measured. The emission consists of a continuous fluorescence band with the maximum at about 460 nm which is at sufficiently high excitation intensities covered with characteristic line structure emission. The appearance of continous emission at this temperature was in accordance with experimental results explained by the increase of the radiative transition probability in AgCl crystals.     

Relaxation processes at high excitation levels and Bose-Einstein condensation of excitons in ZnTe crystals

The singularities of low-temperature emission spectra obtained for ZnTe crystals excited resonantly by a strongly monochromatic source are investigated. The possibility of attaining the coherent luminescent emission due to the exciton-exciton interaction under these conditions is proved. The appearance of the non-polarized needle-like peak and the processes of inelastic interaction of polaritons of the upper polariton branch (UPB) as well as the disappearance of the Raman component are interpreted as the spectral attributes of Bose-Einstein condensation of UPB polaritons.     

Low-voltage red cathodoluminescence of ZnSe single crystals

Red cathodoluminescence from low-resistivity ZnSe:Cu, Al crystals has been observed under the excitation of low-energy electron beams below 50 V. Dependence of current and brightness on applied voltage as well as the emission spectrum are presented. The red emission of ZnSe tends to be subjected to degradation, while the blue and the green of ZnS previously observed do not.     

Luminescence of uranyl nitrate trihydrate crystals at high exciting-light intensities

The characteristic features of the luminescence of uranyl nitrate crystals at high excitation power densities have been considered. It is shown that there occurs accumulation of excitations in a system of uranyl centers, whereas the presence of forced absorption enhances the migration processes over the uranyl complexes. An increase in the power density of excitation leads to the amplification of interaction of the lower excited electronic states and to an increase in the degree of the system nonadiabaticity. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 6, pp. 743–746, November–December, 2005.     

uhf Photoconductivity measurement at high excitation levels

A contactless method is described for measuring photoelectric properties of semiconductors at uhf, employing losses introduced in a resonator by photoconductivity. The possibility of experimental measurement of the filling coefficient of the working range of a uhf generator is demonstrated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 11–14, June, 1979.     

Luminescence of the semimagnetic semiconductor CdMnTe in the wavelength range 370–400 nm at high excitation levels

Luminescence of the semimagnetic semiconductor CdMnTe was studied. It was revealed that, in the near-UV range, the luminescence spectrum of CdMnTe contains a band whose position does not depend on the Mn concentration in the solid solution. The temperature and lux-watt characteristics of the band were investigated, and time-resolved measurements were performed. The totality of the data obtained permits the conclusion that the revealed band can be attributed to the luminescence of clusters of a metastable cubic modification of manganese telluride.