The effect of electron irradiation on the optical properties of the natural armenian zeolite-clinoptilolite

Infrared (IR) absorption and luminescence in chemically and radiation-modified natural Armenian Zeolite (clinoptilolite) samples have been studied. The luminescence was studied in 390–450 nm and 620–710 nm wavelength bands, and the IR measurements were carried out in the 400–5400 cm⁻¹ range. It is shown that the luminescence intensity depends on the content of pure clinoptilolite in the samples and, probably on the distribution of “passive” luminescence centers over Si and Al sites that became “active” under radiation or chemical treatment. The samples of electron irradiated clinoptilolite have higher luminescence intensity than the chemically and thermally treated ones. A decrease in the intensity of IR absorption bands at 3550 cm⁻¹ and 3650 cm⁻¹ was found after irradiation.     

Luminescence excitation spectra and characteristics of luminescence centers with overlapping absorption bands

For an ensemble of different types of luminescence centers with overlapping absorption bands, with no restrictions on the optical densities, we have obtained relations describing the luminescence excitation spectra for each type of center. We consider transformations of the relations in some limiting cases. We suggest a procedure for using the equations obtained to determine the characteristics of the luminescence centers. Some of these procedures have been experimentally implemented in study of intrinsic radiation color centers in lithium fluoride crystals. We have determined the ratios of the luminescence quantum yields for F₂ and F₃⁺ color centers, and we have observed that a major role is played by nonradiative transitions in deactivation of the first excited singlet state of F₃⁺ centers. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 3, pp. 365–371, May–June, 2008.     

Analysis of the latent structure of luminescence and absorption spectra of thallium complexes

Comprehensive investigations of luminescence, excitation, and absorption spectra as well as of the luminescence kinetics of a frozen LiCl-Tl⁺ solution are carried out. It is established that the luminescence spectrum consists of four components. One component is caused by luminescence of the matrix and the remainder by luminescence of one luminescence center, namely, by the saturated complex of thallium TlCl₂(H₂O)Cl₄. The absorption spectrum consists of three components. Their parameters have been evaluated. Each component of the luminescence spectrum is excited in several components of the absorption spectrum. It is found that the luminescence spectrum components and their intrinsic absorption bands are located differently on the frequency axis. These data are similar to those obtained for other activated solutions of electrolytes. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 1, pp. 75–78, January–February, 2000.     

Synthesis and luminescence of a folic acid-europium chelate conjugate

We have synthesized a folic acid–europium complex conjugate which shows promise for biomedical applications. We have studied the absorption spectra, the luminescence spectra, and the luminescence excitation spectra of folic acid–spacer–amino-substituted phenanthroline and folic acid–spacer–europium chelate conjugates, and also of the individual components of the synthesized triads. All the spectral luminescence data obtained confirm that a folic acid–europium complex conjugate is fogrmed. Binding of the synthesized conjugate to a folate receptor on HeLa tumor cells is demonstrated.     

Recording of selective intracavity absorption at doubled frequencies of multimode laser radiation

We carried out measurements of the spectral distribution of wideband dye laser generation intensity within the limits and in the vicinity of an absorption line with its simultaneous recording at the frequencies of the fundamental and second harmonics of laser radiation. In the laser cavity we placed optical cuvettes with active and absorbing media, as well as selecting and nonlinear-optical elements. We show that at double frequencies the contrast of the narrow-band hole in the multimode laser generation spectrum increases. The gain in the concentration sensitivity of measurements depends in this case on the value of the absorption coefficient being determined. Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70, F. Skorina Ave., 220072, Minsk, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 4, pp. 516–521, July–August, 1998.     

Luminescent method for determining low concentrations of a substance in optically dense media

We have developed a method for quantitative luminescent analysis of multicomponent media. To carry out this method, we need to use a standard luminescent probe and have overlap between the luminescence excitation spectra of the probe and the analyte substance. We have shown that the method is applicable for analysis of scattering media with different absorption optical densities, including optically dense media. We have demonstrated that it is invariant relative to changes in the experimental geometry and the parameters of the medium. A broad range of measurable values is characteristic of the method. Its sensitivity is determined by the sensitivity of the luminescence intensity measurements. We have determined concentrations of organic substances in the range ~10^–10 to 10^–11 g/cm³.     

Spectra and structure of hexavalent uranium nanoclusters with mixed acido ligands in the coordination sphere

We have obtained and spectroscopically studied mixed acido ligand (Cl, I) uranyl complexes. We used IR absorption spectra to analyze the nature of incorporation of neutral molecules (in particular, dimethylsulfoxide) into the inner coordination sphere of uranium that that do not completely exhaust the coordination capacity of the central uranium atom. We have observed a good correlation between the frequencies of the totally symmetric stretching vibration of the ion in the IR absorption and luminescence. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 1, pp. 100–103, January–February, 2009.     

Nonlinear energy absorption of femtosecond laser pulses in noble metals

We use calorimetry to determine the energy absorption of femtosecond (fs) laser pulses as a function of incident fluence for Ag, Ag alloys (Ag–Cu and Ag–Pt), and Pt. At low fluences, the measured absorption agrees well with reflectivity data derived from ellipsometry measurements. For Ag and Ag–Cu, the absorbed energy increases nonlinearly with the incident fluence for fluences larger than approximately half of the melting threshold. Near this threshold, the absorption increases by a factor of 3–4. Similar nonlinear absorption is not observed in Pt or Ag–Pt. We propose that the nonlinear absorption is caused by the excitation of d-band electrons below the Fermi surface. For pulse widths longer than 850 fs, the observed nonlinear absorption in Ag diminishes, indicating that diffusive transport and not ballistic transport is the major mechanism of cooling at this excitation level.     

Optical spectra of aqueous solutions of glutamine-tryptophan associates

The optical density and luminescence ability of aqueous solutions of glutamine-tryptophan depend on the degree of oxidation of the initial dry substances of dipeptide. Glutamine-tryptophan has a high associating ability, which increases if stored. The general form of the optical absorption and luminescence spectra of the associates differs little from the spectra of monomers. Among the spectral-optical symptoms of association of a substance in a solution for glutamine-tryptophan, we discovered the hypochromism and narrowing of the absorption spectra and shortening of the fluorescence lifetime. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 4, pp. 436–439, July–August, 2000.     

Dynamics of formation of the composition,structure, and spectral characteristics of uranium complexes

We have examined general rules for the change of frequency of stretching vibrations of UO ₂ ²⁺ (uranyl) as a function of U-O and uranium-ligand interatomic distances. We analyzed the behavior of these frequencies as a function of donor number (DN) of the organic ligand by studying IR absorption and visible luminescence spectra. A linear correlation was found. We proposed spectroscopic methods for determining the DN of ligands, which are difficult to estimate by other methods, and the composition and structure of uranium complexes. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 4, pp. 433–438, July–August, 2007.     

Spectral-luminescent parameters of the amniotic fluid

Absorption and luminescence excitation and emission spectra of the amniotic fluid from females with a normal course of pregnancy and with fetation anomalies are investigated. It is shown that the amniotic fluid manifests, in addition to an intense UV luminescence, a luminescence in the range of 380–650 nm. The first luminescence peak with λ_max = 430–450 nm is most likely due to the presence of NADH₂ and hormones in the amniotic fluid, whereas the peak located at longer wavelengths with λ_max = 520–540 nm is due to pigments (bilirubin, etc.). Differences in absorption spectra of the amniotic fluid in the case of the normal course of pregnancy and upon its pathologies are established. Luminescence emission and excitation spectra of the amniotic fluid in cases of intrauterine fetation pathologies are shifted toward the longwave region compared to normal pregnancy cases. It is concluded that the spectral-luminescent analysis of the amniotic fluid can be used as an additional rapid test for monitoring of intrauterine fetal pathologies. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 6, pp. 939–942, November–December, 1998.     

Raman spectroscopy of carbon nitride films deposited using the filtered cathodic vacuum-arc technique combined with a radio-frequency nitrogen-ion beam

TiO₂–Fe₂O₃ semiconducting films were prepared by the resistive evaporation method on a glass substrate. Impedance and optical absorption measurements were made on these samples. From the impedance analysis (assuming an equivalent RC circuit), it was observed that the admittance and impedance functions are frequency dependent. From the optical absorption spectrum, the energy band-gap value was found to be 1.15 eV. The charge-carrier concentration (N) is calculated by using Mott–Schottky relations. I-V measurements were also made on these samples. Received: 2 November 1999 / Accepted: 24 August 2000 / Published online: 9 November 2000     

Optical properties of CuInS2 nanoparticles in the region of the fundamental absorption edge

Glasses are obtained that contain CuInS₂ nanoparticles dispersed in a silicate matrix. The absorption and luminescence spectra of the glasses containing CuInS₂ nanocrystals with particle dimensions of 10–70 nm are studied. The possible reasons for the longwave shift of the fundamental absorption edge and inconsistency of the crystal structure of the CuInS₂ nanoparticles with a chalcopyrite lattice are discussed. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 3, pp. 387–393, May–June, 1998.     

Electronic excitations of Sc3+ impurity in α-Al2O3 crystals

Optical properties, including luminescence, of scandium-doped α-Al₂O₃ crystals have been studied in the VUV range. An absorption band associated with the scandium impurity was observed at the fundamental-absorption edge of crystalline corundum. A strong luminescence band peaking at 5.6 eV, which is most effectively excited within the 7.7–8.8-eV interval, was found. The kinetic and polarization characteristics of this luminescence were studied within the temperature range 6–500 K. An excitation model of the impurity complex and the mechanism of its relaxation are discussed. Fiz. Tverd. Tela (St. Petersburg) 40, 653–654 (April 1998)     

Recombination kinetics in nonlinear defective LiB3O5 crystals

A study of recombination kinetics in LiB₃O₅ (LBO) crystals by time-resolved luminescence and absorption spectroscopy is reported. An investigation of the kinetics of transient optical absorption (TOA) and luminescence under ns-scale electron-beam excitation performed within a broad temperature range of 77–500 K and a 1.2–5-eV spectral interval has established that the specific features in the recombination kinetics observed in LBO involve electronic, B²⁺, and hole, O⁻, trapping centers. The TOA and luminescence kinetics, as well as their temperature dependence, are interpreted by a model of competing hole centers. Relations connecting the kinetics parameters and the temperature dependence to the parameters of the main LBO point defects are presented. Fiz. Tverd. Tela (St. Petersburg) 40, 2008–2014 (November 1998)     

Thermoluminescence of corundum containing anion defects following ultraviolet laser and x irradiation

The thermoluminescence of single crystals of corundum containing anion defects following x-ray and laser excitation is investigated. Its features in the luminescence bands of F, F⁺, and Cr³⁺ centers are studied. Synchronous measurements of the thermoluminescence and thermally stimulated exoelectron emission are performed by the fractional glow technique following x-ray and laser excitation of the samples. It follows from the results obtained that several traps are active in the temperature range of the principal dosimetric peak (400–500 K). The spectral sensitivity curve contains maxima corresponding to absorption bands of F, F⁺, and Al _i ⁺ centers. A possible mechanism for the recombination luminescence of F centers is discussed. It is found that the material exhibits high sensitivity to small doses of ultraviolet laser radiation. Zh. Tekh. Fiz. 67, 72–76 (July 1997)     

Absorption and emission properties of Bi-doped Mg–Al–Si oxide glass system

A new Bi-doped Mg–Al–silicate glass is suggested and investigated. It can be fabricated by moderate-temperature routine technology. The characteristic relaxation time of 300–800 μs in combination with the high quantum yield (up to 85%) and wide excitation spectrum makes this glass a promising laser material. The obtained quadratic dependence of the visible absorption intensity is an argument in favor of the hypothesis that the absorption and infrared luminescence in Bi-doped glasses are caused by Bi₂ dimers.     

Methods for fine-tuning frequencies of absorption of actinide complexes to frequencies of laser generation lines

On the basis of analysis of relationships relating, among themselves, the positions of bands in the spectra of electron and IR absorption of uranyl complexes in solutions and the donor ability of neutral ligands, the possibility is shown for fine-tuning frequencies of absorption of complexes to frequencies of argon- and CO₂-laser generation lines and using them in the development of methods of control over chemical reactions involving actinides. Belarusian State University, 4, F. Skorina Ave., Minsk, 220050, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 3, pp. 420–422, May–June, 1999.     

Thermally stimulated luminescence of yttrium oxide in a transparent dielectric medium

The thermally stimulated luminescence of Y₂O₃ in contact with a dielectric is investigated. The measurements were carried out in an atmosphere of dry air, in glycerol, ethylene glycol, and water. Shifting of the spectrum of thermally stimulated luminescence and decrease in the luminescence intensity with an increase in the dielectric constant of the medium were revealed. A discussion of the results is presented. I. I. Mechnikov Odessa State University, 2, Dvoryanskaya St., Odessa, 270026, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 3, pp. 462–463, May–June, 1998.