Effect of Gamma Radiation on Optical and EPR Absorption Spectra of Phosphate and Fluoride Glasses Containing Lead

The induced optical and EPR absorption spectra of phosphate and fluoride glasses containing lead are investigated. It is revealed that exposure to gamma radiation leads to the formation of radiation-induced defects responsible for the induced absorption band with a maximum at 12500–13500 cm⁻¹ and the EPR signal in the form of an almost symmetric line with a g factor of 1.999 and a linewidth of ≈26 Oe. Analysis of the intensities of the absorption bands and the EPR signals in the spectra of glasses with low terbium, tin, and carbon contents and the study of their thermal bleaching demonstrate that the color centers are electron traps, whereas the paramagnetic centers are hole-trapping centers. Examination of the change in the parameters of the absorption bands in the spectra of glasses with different R ₂O contents (R = Na, K, Rb, Cs) makes it possible to determine the location of the color centers associated with the Pb⁺ ions in the structure. It is established that the glasses under investigation are characterized by the nonlinear absorption of radiation at a wavelength of 1.06 μm. The mechanism of formation of radiation-induced defects is considered. Original Russian Text Copyright ? 2005 by Fizika i Khimiya Stekla, Bocharova, Karapetyan.     

An Alternative Model for Photochromism of Glasses: Reversible Injection of Carriers from a Microcrystal and Its Surface States into Point Defects of Glass

The radiation-induced absorption spectra of photochromic homogeneous silicate glasses and heterogeneous borosilicate glasses containing AgCl, AgBr, or CuCl microcrystals are analyzed. The inference is made that these spectra contain the bands of traditional radiation-induced color centers (RICCs) in glasses and the bands of halide defects in microcrystals. The band model of the photochromic process in the microcrystal–surface states–glass system is proposed on the basis of the performed analysis with due regard for burning of the exciton hole in the induced spectrum of CuCl-containing glass. This model makes it possible to explain a large number of experimental data.     

Interaction of radiation-induced defects of glasses with CdSe and CdS nanocrystals

The influence of X-ray irradiation on the absorption spectra of commercial light filters based on the glasses containing selenium, cadmium, and sulfur has been investigated. The light filters were preliminary subjected to the heat treatment, which resulted in the precipitation of nanocrystals in the glass matrix. The irradiation leads to stationary partial bleaching of glasses. Analysis demonstrates that the difference spectra contain the induced absorption bands of conventional radiation-induced color centers of alkali silicate glasses and a fine structure. The fine structure closely resembles the known difference spectra obtained under the action of the external constant or low-frequency alternating electric field on glasses containing CdSe nanocrystals. The conclusion is drawn that the stable radiation-induced centers of the glass at the interface with nanocrystals serve as a source of the Coulomb field affecting the energy levels of the size quantization of the nanocrystals. It is suggested that nanocrystals of the type of the CdS_xS_1−x solid solutions in these glasses are either lacking or do not manifest themselves in the spectra after irradiation.     

Interaction of radiation-induced defects of glasses with CdSe and CdS nanocrystals

The influence of X-ray irradiation on the absorption spectra of commercial light filters based on the glasses containing selenium, cadmium, and sulfur has been investigated. The light filters were preliminary subjected to the heat treatment, which resulted in the precipitation of nanocrystals in the glass matrix. The irradiation leads to stationary partial bleaching of glasses. Analysis demonstrates that the difference spectra contain the induced absorption bands of conventional radiation-induced color centers of alkali silicate glasses and a fine structure. The fine structure closely resembles the known difference spectra obtained under the action of the external constant or low-frequency alternating electric field on glasses containing CdSe nanocrystals. The conclusion is drawn that the stable radiation-induced centers of the glass at the interface with nanocrystals serve as a source of the Coulomb field affecting the energy levels of the size quantization of the nanocrystals. It is suggested that nanocrystals of the type of the CdS_xS_1−x solid solutions in these glasses are either lacking or do not manifest themselves in the spectra after irradiation.     

Gamma-Ray-Induced Coloration in Solids; Application to Glass Systems

General aspects of radiation-induced coloration in solids are discussed. It is considered that the most significant initial effect of the radiation is to produce free electrons and trapped holes in a track. The decay of the track from the initial condition is described in some detail, assuming (a) that the rate of diffusion of electrons from the track is small compared with the rates of other processes and (b) that primary processes which form color centers can be considered to be independent of secondary processes which cause destruction of color centers. A method of calculation is described which gives the concentration of color centers formed at various doses. With plausible assumptions for the parameters, agreement with the data of Schulman et al. on a silver phosphate glass is obtained. The treatment of glasses less simple than the silver phosphate glass is also discussed.     

Electrochromism and reversible changes in the position of fundamental absorption edge in cathodically deposited amorphous WO3

Amorphous WO₃ (a-WO₃) films have been produced by electrodeposition from a sodium tungstate-based aqueous electrolyte. Their coloration under the action of cathode current in 1N H₂SO₄ is accompanied by a reversible shift of ∼0.42 eV in the fundamental absorption edge of the oxide towards higher quantum energies. The shift of the edge is proportional to the change in the potential of the WO₃ electrode being colored and is caused by the sequential filling, by injected electrons, of levels in the energy spectrum of electronic states formed by the unoccupied d-orbitals of W⁶⁺ centers. The optical characteristics of the W⁵⁺ centers which are formed in this case (color centers of electrochromic material) depend on whether a particular tungsten atom has a double bond to the oxygen atom (WO type bond). At the initial stage of coloration, injected electrons are captured mainly by the W⁶⁺ centers that have no such bonds. Then, W⁶⁺ centers with WO bonds, which have a higher position of the unoccupied d-orbitals on the energy scale, are also filled; this is accompanied by the appearance of an extra absorption band with maximum at ∼2 eV in the optical spectrum of films.     

Spectroscopic Features of Silica Glasses Doped with Tin

The absorption, photoluminescence, and photoluminescence excitation spectra are investigated for tin-doped silica glasses synthesized by different methods. In all the glasses studied, two new centers belonging to the tin dopant in the SiO₂ network are revealed in addition to the well-known oxygen-deficient center with the absorption band at 4.9 eV. One new center is associated with the absorption band at 5.9 eV and the photoluminescence bands at 2.7 and 3.6 eV, whereas the other center is characterized by the absorption band in the range of 4.56 eV and the photoluminescence band at 2.95 eV. Both new centers are identified as oxygen-deficient centers. The latter center is an analog of the centers observed in pure silica glasses synthesized in a nitrogen atmosphere and in germanosilicate glasses prepared by the MCVD and SPCVD methods. It is revealed that the formation of the oxygen-deficient center is one of the main channels of incorporating tin into the SiO₂ network in all tin-containing silica glasses. Consideration is given to the reasons for the lower efficiency of the photodecay of oxygen-deficient centers in the SiO₂ network in tin-containing glasses as compared to that in germanosilicate glasses and for the relatively high efficiency in the formation of the photoinduced refractive index in optical fibers with a core consisting of tin-containing silica glass.     

ESR Study of Devitrification Processes

The radiation-induced ESR centers in glasses with different Ti concentrations were studied to elucidate crystallization processes in the glass. The parameters of the induced ESR absorption associated with the T ₂ center were investigated systematically as a function of heat treatment. The induced T ₂ centers in the glasses containing small concentrations of Ti characteristically decreased in intensity as nucleation began and disappeared completely in devitrified samples. A mechanism is proposed for the destruction of the T ₂ center as nucleation proceeds to crystallization. Supporting X-ray diffraction evidence is given. The systematic decrease in the ESR intensity of this radiation-induced center provides a means of monitoring devitrification processes in glasses.     

Studies on Nonmetals During Irradiation: V, Growth and Decay of Color Centers in Barium Aluminoborate Glasses Containing Cerium

The radiation-induced absorption of a group of barium aluminoborate glasses was studied in a new facility for measuring optical absorption during irradiation with γ-rays. The results demonstrate that this technique provides significant new information on the kinetics of the radiation-induced coloring of glasses and suggest that most previous measurements are, at best, suspect. Barium aluminoborate glasses, both with and without Ce, were prepared under normal and reducing conditions. The coloring during irradiation and the decay after irradiation can be characterized by the absorption at 3.0 e V and at 2.25 or 1.90 e V. The Ce-free base glass continued to color as long as irradiated and, at a given dose, the absorption was at least 2 or 3 times that of the other glasses. The totally reduced 1% Ce glass colored to a constant level in the uv, but in the visible the coloring increased to a maximum and then decreased to a constant value. The partially reduced 1% Ce glass also colored to a constant value in the uv, but in the visible the original absorption decreased slightly. All the coloring curves recorded during irradiation are described accurately by expressions that include one or more increasing saturating exponential terms and may contain one linear or one decreasing saturating exponential term. After irradiation the coloring curves decrease and can be resolved accurately into one or more decreasing exponential components. Futhermore, all the observed coloring-curve features were derived from relatively simple kinetics.     

Picosecond Time-Resolved Dispersion Spectroscopy Using the Interference between Population and Thermal Phase Gratings

A new method is presented for measuring directly the dispersion spectrum of short-lived transients, based on heterodyne transient grating spectroscopy. The light diffracted from a preformed thermal phase grating is used as a local oscillator, in phase with the light diffracted from the population phase grating. Time-resolved dispersion spectra measured upon photoinduced electron transfer reaction between 9,10-dicyano-anthracene and anisole in acetonitrile are presented. These spectra and the corresponding absorption spectra obtained by Kramers-Kronig transformation are compared with those deduced from the homodyne transient grating spectra. Potential applications of this technique are discussed.     

Interaction of Gamma Rays with Calcium Aluminoborate Glasses Containing Holmium or Erbium

The optical absorption spectra of nominally pure and rare-earth-ion-doped (Ho³⁺ or Er³⁺) calcium aluminoborate (cabal) glasses were measured from 190 to 900 nm before and after γ-ray irradiation. The induced absorption spectra, calculated as the difference between the spectra of the irradiated and the unirradiated glasses, exhibit the characteristic absorption bands caused by the respective rare-earth ions. The intensity of the induced bands depends on the rare-earth oxide content. The response of the cabal glass to γ-ray irradiation is related to the formation of color centers associated with the intrinsic defects in the lattice structure of the cabal glass. The rates of formation and annihilation of the color centers are believed to approach saturation or equilibrium with prolonged irradiation.     

Colors of dope and yamn of spun-dyed cellulose acetate

A method of color control of bulk-dyed cellulose acetate is described, based on the transmittance spectrum of the dope. Control can be effected only if the spectrum is recorded from thick samples which amplify the absorption from small amounts of impurities that later cause unacceptable color differences on the yarn. The calculation of the reflectance spectrum, and hence the color, of the yarn from the transmittance spectrum of the dope by Kubelka-Munk theory is not satisfactory due to faint turbidity of the ‘bright’ dope. The reflectance spectrum of the yarn can be calculated from a series expansion of the experimental Lambert law absorption coefficient with very satisfactory results. A fully computer-managed color-control method is employed successfully in industrial practice.     

还原增感立方体AgCl微晶光电子衰减特性

利用微波吸收介电谱检测技术测得了还原增感立方体氯化银微晶光电子衰减随增感条件的变化规律。实验发现,随增感条件的不同,增感中心发生了由空穴陷阱作用向深电子陷阱作用的转变。当增感中心起空穴陷阱作用时通过俘获空穴,降低了光电子与光空穴的复合几率,提高了光电子的利用率,从而有利于潜影的形成。由此得到在增感浓度一定时的最佳增感时间和最佳增感温度的组合。     

Effect of Different Treatments on Decay of Radiation-Induced Color Centers in Potassium Lead Silicate Glass

The influence of short-term heating or cooling and exposure to visible light on the bleaching of a gamma-irradiated glass stored at 20°C is investigated by photometry. The decay of radiation-induced color centers is retarded under the action of heating and gradually regains its initial rate after the heating ceases. The transient stage can be described as relaxation. It is revealed that isothermal photobleaching does not exhibit a similar aftereffect.     

从技术特性看卤化银照相和数码照相的前景(Ⅰ)

通过比较普通彩色胶卷与普通电子照相机 CCD及 CMOS的结构及其成像效率 ,分析了卤化银照相和数码照相的进展及其前景。预测彩色胶卷的成像效率有可能提高若干倍 ,它取决于入射光子的吸收效率以及吸收光子后转换成卤化银颗粒潜影中心的效率的提高；预测彩色胶卷在影像质量和成本方面相对于数码相机的优势将继续保持 ,因为 CCD的成像率由入射光子的吸收效率和光子被吸收后转换成光电子的效率决定 ,这两种效率都已经非常高 ,几乎没有改进的余地 ,而 CMOS则可以使数码照相机再上一个新台阶。     

Color Centers in Sulfur-Doped Silica Glass: Spectroscopic Manifestations of an Interstitial Molecule S2

The absorption and luminescence spectra of color centers in sulfur-doped silica glass are investigated. It is demonstrated that the most intense bands of absorption at 280 nm and luminescence at 385 nm have a resolved vibrational structure. These bands are assigned to interstitial molecules S₂, which are weakly bound to the glass network. The proposed model provides a simple interpretation of the shift observed for the luminescence excitation band with respect to the corresponding absorption band.     

Comparison of methods of parameric correction for evaluating metamerism

In practice, most metameric pairs do not achieve colorimetric equality for a set of reference conditions. These parameric pairs are composed of a residual color difference and a metameric difference. Three techniques have been used to correct this residual color difference: an additive correction in L*a*b*, a multiplicative correction in XYZ (recommended by the CIE), and parameric decomposition where the batch's spectrum is adjusted. Parameric decomposition can be viewed as batch correction using three “colorants” (process primaries) where the color‐mixing model is linear in reflectance. Most often, Cohen and Kappauf's Matrix R technique is used where the primaries are color matching functions. Alternative primaries were derived from a Munsell Book of Color and an automotive paint system using principal component analysis (PCA) and independent component analysis (ICA). 1,152 parameric pairs about 24 color centers were synthesized using the paint system and Kubelka–Munk turbid‐media theory. Each parameric pair was corrected to a metameric pair using these methods. Spectral accuracy was evaluated by comparing the corrected spectra to metameric reference spectra calculated using Kubelka–Munk batch correction. The Matrix R technique had the worst spectral accuracy under the reference conditions while both PCA and ICA had similar and reasonable accuracy. The special index of metamerism, change in illuminant, was calculated for each parameric pair using these various correction techniques to achieve colorimetric equality. The Matrix R and CIE‐recommended multiplicative techniques were statistically significantly worse than parameric decomposition using Munsell Book of Color PCA and ICA and automotive ICA process primaries. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 293–303, 2007     

Interaction of γ-rays with Some Alkali-Alkaline-Earth Borate Glasses Containing Chromium

The change in the visible spectra of some irradiated ternary borate glasses containing chromium has been studied by increasing the γ-ray doses with changing alkali content or increasing chromium concentration. In the glass without chromium, the γ-rays induce two absorption bands which are attributed to the formation of positive hole centers, whereas in the glass containing chromium at least three absorption bands are observed. The results showed that the visible absorption bands before and after γ-ray irradiation exhibited changes with the radiation dose and/or the chemical composition of the glass. The response of the glasses to γ irradiation is related to the creation of defect color centers, the approach of a saturation condition, and the possible photochemical effect on the transition metal.     

不同接种物启动Anammox-EGSB反应器的污泥性能

分别以厌氧产甲烷污泥（AMS）、新鲜厌氧氨氧化污泥（FAS）和储藏厌氧氨氧化污泥（SAS）作为接种物,研究了厌氧氨氧化膨胀颗粒污泥床（Anammox-EGSB）反应器启动过程中的污泥性能。结果表明,3种接种物启动Anammox-EGSB反应器的有效性为：FAS＞SAS＞AMS;启动过程中3种接种物的生物含量（VSS/SS比）上升,污泥粒径增大,沉降速度加快,反应活性提高,颜色趋向鲜红,Anammox性能逐渐改善,细胞悬液在相似文献   

Gamma Radiation-Induced Changes in Trombay Nuclear Waste Glass Containing Iron

Alkali-based barium borosilicate glasses having similar composition to the Trombay nuclear research reactor waste base glass containing iron were prepared and irradiated by gamma rays. The radiation-induced defect centers were investigated using electron paramagnetic resonance (EPR) technique. The results showed the formation of silicon hole centers and electron trap centers apart from boron-based oxy hole centers in the glass due to the irradiation. The EPR Hamiltonian parameters for these radicals were evaluated by simulation technique using Bruker SIMFONIA computer program. Glasses with varying iron content were irradiated with the same dose to evaluate the effect of iron content on the defect center concentration. A spin counting technique was employed to evaluate the number of defect centers produced in each glass. It was observed that the defect center concentration reduced as a function of increasing iron content. This was attributed to the charge trapping process of ferric ions in the amorphous system.