[en] The spectra of fluorescence and fluorescence excitation of tetraazachlorin and tetraazabacteriochlorin substituted at the reduced pyrrole rings have been investigated at 290 and 77 K; the fluorescence quantum yield and life time have been measured at 290 K; the fluorescence polarization spectra have been obtained at 77 K. Quantum-chemical calculations have been performed for a series of porphin derivatives: porphin-chlorin-bacteriochlorin-tetraazaporphin (porphyrazine)-tetraazachlorin- tetraazabacteriochlorin by the CNDO/S method with the use of molecular geometry acquired by the AM1 and PM3 optimization. The visible and UV absorption spectra and the fluorescence polarization spectra are adequately described by the CNDO/S calculation results, as well as the spectral changes in the series porphyrazine-tetraazachlorin-tetraazabacteriochlorin and from bacteriochlorin to tetraazabacteriochlorin. Strong quenching of fluorescence on the pyrrole rings reduction in the porphyrazine macrocycle has been found. It is shown that this quenching cannot be wholly explained by the increase in the rate constant of the S₁→S₀ internal conversion which may be due to the lowering of the S₁ level. Supposedly, the increase in the rate constant of the S₁→T₁ intersystem crossing is due to participation of intermediate triplet levels in this process

[en] The luminescence of Eu³ ions in ultradispersion diamond powder activated through the impregnation with the Eu(NO₃)₃ · H₂O solution and thermotreated at different temperatures is studied. The multiple increase in the efficiency of exciting the 5D₀ state of the Eu³⁺ ions as compared to the analogous thermotreated europium nitric acid salt is identified in the charge transfer band. The above effect is explained by the increase in the degree of the Eu-O bond covalence and by the change in the activator coordination polyhedron due to the formation of the Eu-O-C chemical bonds

[en] Photoluminescence (PL) and photoexcitation (PE) spectra of porous silicon (PS) films, which had the initial porosity 50-60% and were formed on p-type substrates and subjected to anodic oxidation and chemical etching, are investigated. It is found that the amorphous phase of etched PS does not manifest itself on PE spectra but influences PL spectra of PS. Features of PE spectra before and after etching and PL as well as PE spectra time evolution can be interpreted within a framework of the model of quantum confinement, in which mechanical stresses of silicon crystallites of PS are taken into account

[en] Results are reported from a study of the optical properties of porous alumina films obtained by anodizing in a water solution of sulfuric acid and modified by thermal annealing in air at T ≥ 850 C. A comparative analysis of the data shows that the near-UV and visible photoluminescence of alumina anodized in a sulfuric acid solution is caused primarily by oxygen divacancies (F₂, F₂⁺ and F₂²⁺ centers), while sulfate ions have little effect on the luminescence properties of anodic alumina in this spectral range. (authors)

[en] Concentration and temperature dependences of luminescent intensity of Tm³⁺ ions in yttrium oxide at ultraviolet and infrared excitations were measured. It was done assumption about main role of interband cross-relaxation of Tm³⁺ excited states in forming of this dependences. The impurity of secondary rare-earth ions may influence essentially on temperature dependence of the anti-Stokes luminescence intensity by removing the position of maximum

[en] This is a study of the luminescence properties of coatings formed on aluminum alloys by anodizing in electrolytic solutions based on oxalic, sulfuric, and tartaric-sulfonic acids. At least two emission centers, with band maxima in the ranges of 390-410 and 470-510 nm, can be reliably identified in the photoluminescence spectra. The first type of center is characterized by single-band photoluminescence excitation spectra and the second, by two-band spectra. An analysis of the two-band photoluminescence excitation (PLE) spectra in the range of 470-510 nm shows that the position of the narrow short-wavelength PLE spectrum near 272 nm is independent of the type of acid used in the anodization process. The position and shape of the other PLE spectral bands depend both on the type of acid used and on the processing of the alloy or alumina surfaces. It is assumed that defect-free alumina centers are responsible for the 272 nm PLE band, while the other photoluminescence bands are caused primarily by different divacancies of oxygen (F₂⁺, F₂, and F₂⁺² centers) whose origin is governed by the type of electrolyte. (authors)

[en] Research of thin films, obtained by high-frequency multipulse f ~20-30 kHz laser action on zinc oxide ceramics in vacuum and deposited on a quartz substrate are conducted. The morphology of obtained films is studied using atomic force microscopy. Features of its spectra of Raman scattering and photoluminescence spectra are revealed and discussed. (authors)

[en] We have measured the spectral-luminescent characteristics of tetraphenyltetraazaporphin and a substituted tetraphenyltetraazachlorin, a new potential absorber and emitter for the near IR region, in solutions at 293 and 77 K as well as the quantum yields of fluorescence and singlet oxygen generation. It has been shown that the changes in the excited electronic states energy in passing from tetraphenyl substituted to octaphenyl substituted compounds are not minor. Based on performed quantum-chemical calculation, an explanation of this property is given. It has been found that, for tetraazaporphin, the tetraphenyl substitution results in decreasing the quantum yields of fluorescence and singlet oxygen generation whereas, for tetraazachlorin, on the contrary, tetraphenyl substitution results in the rise of their values. (authors)

[en] The spectral-luminescence properties of a tetraazachlorin derivative with a norbornene fragment annelated to a reduced pyrrole ring and its complexes with zinc and palladium have been studied at 293 and 77 K. For the norbornene-substituted free base, differences in fluorescence from unsubstituted tetraazachlroin and its dibenzobarrelene-substituted analog are found. The fluorescence lifetime is observed to rise by ∼7 times for the free base and by ∼1.6 ties for the Zn complex on going from 293 to 77 K. An essential dependence of the photophysical parameters on the nature of the solvent is noted. The fluorescence polarization spectrum of the norbornene-substituted tetraazachlorin reveals in the Soret band region at least four electronic transitions. For the Pd complex, weak phosphorescence in the near IR region has been detected; the 0-0 band maximum is at 990 nm and the singlet-triplet interval amounts to 5800 cm^-1, which is larger by 400 cm^-1 than for Pd tetraazaporphine. The quantum yields of the photosensitized formation of singlet oxygen have been determined using a relative luminescence method. (authors) Key words norbornene-substituted tetraazachlorin - Zn and Pd complexes - absorption spectra - fluorescence spectra - fluorescence polarization spectra - phosphorescence spectra - quantum yield - fluorescence lifetime - singlet oxygen formation

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