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The absorption spectra of thin films (CsCl)1–x(CuCl)x were studied at T = 90 K in the spectral range 2–6 eV. From the analysis of the spectra, the formation of CsCu2Cl3 and Cs2CuCl3 compounds in the CsCl–CuCl system was created. The Cs2CuCl3 compound is stable only in a vacuum; in air, it apparently decomposes into CsCu2Cl3 with a disordered crystal lattice and CsCl. The exciton spectrum of both compounds is interpreted on the basis of transitions in the Cu+ ion. The one-dimensional character of excitons in CsCu2Cl3 and the two-dimensional character in Cs2CuCl3 were established. [ABSTRACT FROM AUTHOR]

The absorption spectra of RbCu2Cl3 and Rb2Cu3Cl5 thin films were studied in the 2−6 eV spectral and 90−450 K temperature ranges. The localization of excitons in CuCl 4 3 − structural elements of crystal lattice of compounds, three-dimensional nature of excitons in RbCu2Cl3 and two-dimensional nature of excitons in Rb2Cu3Cl5 were established. The exciton spectra of RbCu2Cl3 and Rb2Cu3Cl5 thin films were interpreted based on the transitions in the Cu+ ion. [ABSTRACT FROM AUTHOR]

Formation of compounds RbPbI3 and Rb4PbI6 in the RbI-PbI2 system is revealed, and their absorption spectra are investigated in an energy interval of 2-6 eV and at temperatures from 90 to 500 K. It is established that the low-frequency exciton excitations are localized in PbI64- structural elements of the crystal lattice, they are classified as excitons of intermediate coupling and are of a three-dimensional character in RbPbI3 and a quasi-two-dimensional one in Rb4PbI6. [ABSTRACT FROM AUTHOR]

The excitonic absorption spectra of thin films of the solid solutions Rb2(Cd1-xZnx)I4 have been studied for the first time. It is determined that the spectra of the solid solutions are stable and consist of two bands which genetically originate from the initial bands of the compounds Rb2CdI4 and Rb2ZnI4. It is shown on the basis of the structure of the crystal lattices of the compounds that the concentration dependence of the spectral position of the excitonic bands AI and AII is related with the transfer of excitons between CdI4 and ZnI4 tetrahedra along the b axis of the solid solutions. The experimental result is in good agreement with the calculation of the energies EAI(x) and EAII(x) on the basis of a theory similar to the theory of Davydov splitting of excitonic bands in molecular crystals. [ABSTRACT FROM AUTHOR]

The absorption spectrum of Rb2ZnI4 thin films in the spectral region 3–6 eV is investigated in the temperature range 90–290 K. It is found that the compound is a direct-gap insulator and that the low-frequency excitations are localized in the ZnI42- structural layers of the crystal lattice and are of a quasi-two-dimensional character. For T<200K the temperature dependence of the spectral absorption and the half-widths of the long-wavelength exciton band exhibits thermal memory effects due to precursors of the low-temperature phases. [ABSTRACT FROM AUTHOR]

The excitonic absorption spectra of thin films of the solid solutions Rb2(Cd1-xZnx)I4 have been studied for the first time. It is determined that the spectra of the solid solutions are stable and consist of two bands which genetically originate from the initial bands of the compounds Rb2CdI4 and Rb2ZnI4. It is shown on the basis of the structure of the crystal lattices of the compounds that the concentration dependence of the spectral position of the excitonic bands AI and AII is related with the transfer of excitons between CdI4 and ZnI4 tetrahedra along the b axis of the solid solutions. The experimental result is in good agreement with the calculation of the energies EAI(x) and EAII(x) on the basis of a theory similar to the theory of Davydov splitting of excitonic bands in molecular crystals. [ABSTRACT FROM AUTHOR]