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[en] The low-temperature luminescent spectra of single crystals of CdS and CdSe laser-excited above the exciton absorption edge are investigated. In addition to the normal luminescence the spectra contain a series of narrow lines (LO lines) corresponding to emission from hot excitons and shifted into the Stokes region relative to the exciting line by energies of 2, 3, 4, etc. times the LO phonon energy. The optical orientation of the hot excitons was ascertained from a study of the polarization of these lines. The observation of orientation for excitation by linearly polarized light confirms that excitons are involved in the formation of the LO lines. The observed degree of linear polarization of the LO lines can be explained on the basis of a simple model of scattering involving two polariton branches (a ''photonic'' branch and an ''excitonic'' branch). It is possible to separate out the contribution made to the depolarization of the LO lines by exciton scattering on LO phonons. Defect-induced depolarization is also observed

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[en] Photoluminescence (PL) spectra of HgI₂ tetragonal modification in the temperature range of 4.2-77 K were studied. It is shown that the most intensive at T=4.2 K lines in λ_x=531.8 nm and λ₂=532.2 nm PL spectrum appear during the emitting recombination of excitons localized on mercury and iodine vacancies, accordingly. The nature of luminescence bands at 543, 538, 560 and 635 nm is discussed

[en] It is shown for the first time through the x-ray and optical methods that there exist crystal areas with package defects (PD) in the CdS_1-xSe_x crystals (by x = 0.10 - 0.50). The x-ray studies showed, that package defects are present in all studied samples. The PD effect in the CdS_1-xSe_x solid solutions of various composition on their exciton reflection spectra and photoluminescence are studied. New exciton bands are determined in the crystals with high PD content. The resonance radiation of free excitons and corresponding phonon reiterations are observed in the CdS_1-xSe_x crystals for the PD phase. The effect of reabsorption, which may lead to change in the form of the nonphonon radiation line (doublet formation), is analysed. It is noted, that change in the form of the photoluminescence exciton line, conditioned by the PD, indicates its complex structure

[en] The effect of localizing excitons by heterogeneity of solid solution composition near crystals surface, providing for appearance of new unusual peculiarities in the optical exciton spectra is studied. The above mentioned peculiarities, identified in the CdS_1-xSe_x reflection exciton spectra with low Se content (x ≅ 0.01), were studied within the temperature range of 4.2-200 K. The models of localizing exciton potentials, providing for the most adequate description of the reflection experimental spectra, are determined. The nonlinear model potentials, accounting for the diffusion mechanism of structural heterogeneity origination and the crystal real surface state, were applied in the process of analysis. High sensitivity of the auxiliary structure forms in the reflection spectra to the type and parameters of the near-surface potential zone is established