YAG晶体色心的EPR谱

本文描述了8种YAG样品的室温和77K的EPR谱.从这些谱的参数与光谱的实验数据对照,认为晶体中有三种顺磁性的色心,其中g～2.00和g～1.98两条顺磁谱相应于光谱2×10~4cm~(-1)～3.4×10~4cm~(-1)的吸收带,为YAG基质晶体中的缺陷俘获一个电子构成的电子型缺陷中心;而 g～30.60的顺磁谱线与氧空位和掺杂的金属离子Mg~(2+) 、Cr~(3+)有关,推测为氧空位团或氧空位与金属离子构成的S>1/2的复合顺磁中心缺陷.YAG晶体随着在大气氛中高温退火,氧的进入和金属离子的掺入,造成电子和空间体积的不平衡,从而使晶体色心浓度加大.     

LiNbO_3与掺铁LiNbO_3晶体的光谱性能

在 L i Nb O3中掺进 Fe2 O3生长了 Fe∶ Li Nb O3晶体。对晶体进行氧化、还原处理 ,测试了 Fe∶ Li Nb O3晶体的吸收光谱以及 Li Nb O3和 Fe∶ L i Nb O3晶体的拉曼光谱 ,研究了氧化还原处理对晶体的光谱影响。     

Divalent cerium and praseodymium ions in crystals of alkaline-earth fluorides

We have studied the absorption spectra of radiation-induced divalent cerium and praseodymium ions in crystals of alkaline-earth fluorides. Using ab initio quantum-mechanical methods, we have calculated absorption spectra of divalent praseodymium ions in CaF₂ crystals for the first time. The theoretical spectrum agrees rather well with the experimentally registered spectra.     

Production of pseudoscalar bosons upon stimulated Raman scattering in dielectric media

Conditions for the emergence of pseudoscalar vibrational excitations in the spectra of spontaneous and stimulated Raman scattering in molecular liquids and crystals are determined. The spectra of spontaneous and stimulated Raman scattering by pseudoscalar bosons are measured experimentally for several liquids and crystals.     

“Anomalous” spectral photoresistive field effect in CdS crystals caused by the screening of the electron-hole interaction

The changes observed in low-temperature (T = 77 K) near-band-edge photoconductivity spectra of CdS crystals in response to an external transverse electric field applied to the sample surface have been investigated. An analysis of the “anomalous” character of these changes for a number of crystals has revealed a significant role of the near-surface effects of screening of the electron-hole interaction in the formation of near-band-edge photoconductivity spectra of CdS crystals with a technological excess of cadmium near the surface. It has been shown that the depletion (enrichment) transverse electric field leads to a weakening (enhancement) of screening effects in the photoconductivity spectra of the CdS crystals.     

Luminescence of uranium ions in sodium fluoride crystals

The luminescence spectra of bulk and fiber sodium fluoride crystals activated with uranium ions have been analyzed. Luminescence of uranium centers at temperatures of 8.5 and 300 K is considered and the features of the luminescence spectra of these centers in crystals of different dimension are analyzed. The luminescence spectra are simulated with allowance for the spectral-line profiles. Possible models of uranium centers are considered.     

铝酸镧单晶体中Ce3+的能级结构和荧光特性

采用提拉法成功生长了纯LaAlO₃和掺铈的LaAlO₃单晶体.测试了它们的远红外吸收谱，紫外吸收谱，荧光谱.根据吸收光谱确定了晶体中Ce³⁺的能级结构，利用这一能级结构模型较好地解释了Ce：LaAlO₃晶体的荧光光谱. 关键词： Ce：LaAlO3 吸收光谱 能级 荧光光谱     

Stray-light induced artefacts in absorption spectra of crystalline oligothiophenes

The absorption spectra of oligothiophene single crystals and thin films are discussed in terms of stray light induced experimental artefacts. After typical experimental problems have been overcome, absorption spectra can be collected over a wide spectral range in the UV-Vis region that has often not been included in the literature data. A clear similarity is found between the absorption spectra of single crystals and highly ordered thin films. Received 10 April 2002 Published online 13 August 2002     

Electromagnetic fluctuations in anisotropic dielectric crystals

Landau and Lifschitz's theory of electromagnetic (EM) fluctuations in dielectric media is applied to anisotropic dielectric crystals. In the limit of zero damping the spectra of the autocorrelation functions of the EM-field in unaxial crystals are calculated. With the aid of these spectra a generalized Planck's law of radiation is reported.     

Raman Scattering in Three-Dimensional Photonic Crystals

The optical properties of three-dimensional photonic crystals associated with the form of reflection spectra from their surface (appearance of a forbidden gap in the energy spectrum) and with the specific features of Raman scattering are analyzed. Idealized models of the energy band structure of photonic crystals are studied. Expressions for the group velocity of photons with energy close to the forbidden gap are derived. Experimental results on the Raman scattering in photonic crystals based on artificial opal as well as in fused silica are discussed. Bands due to quantum-size effects (presence of nanoclusters in fused silica and nanoglobules forming the lattice of globular photonic crystals) were manifested in the spectra of inelastic light scattering. It is proposed to use photonic crystals for the creation of sensitive sensors of organic and inorganic substances using modern Raman techniques.     

Crystalloluminescence and temporary mechanoluminescence of As2O3 crystals

Crystalloluminescence and temporary mechanoluminescence of As₂O₃ crystals are investigated. The crystalloluminescence spectra are similar to the photoluminescence and mechanoluminescence (of fresh crystals, in CO₂ atmosphere) spectra. The mechanoluminescence spectra of freshly grown crystals taken in air consist of the superposition of the photoluminescence and nitrogen emissions. The mechanoluminescence spectra of old crystals of As₂O₃ consist of only the nitrogen emission. The total number of crystalloluminescence flashes is linearly related to the total mass of the crystals grown. The mechanoluminescence intensity increases with the mass of the crystals. The mechanoluminescence intensity decreases with the age of the crystals and the rate of decrease increases with increasing temperature of the crystals. Different possibilities of crystalloluminescence and mechanoluminescence excitations in As₂O₃ crystals are explored and it is concluded that crystalloluminescence and mechanoluminescence are of different origins.     

KCl crystals with a silver impurity: From point defects to oriented AgCl microcrystals in a crystalline host

This paper presents the first unambiguous optically detected magnetic-resonance (ODMR) evidence that AgCl crystals embedded in the KCl lattice and retaining the host orientation are formed in KCl crystals grown with a 2–3 mol % silver impurity. ODMR spectra were obtained of self-trapped holes, shallow electronic centers, and self-trapped excitons, which are typical of AgCl, and a number of substantially different ODMR spectra were also obtained. The differences between the ODMR spectra observed in samples cleaved from different parts of a KCl: AgCl crystal are probably accounted for by embedded AgCl crystals varying in size from large micro-to nanocrystals.     

Hole traps in GaSe:Co single crystals

In order to clarigy the nature of the cobalt related hole traps (CRHT) in GaSe single crystals, GaSe:Co single crystals were grown by the Bridgman method and the optical absorption spectra, the photoconductivity spectra and the thermally stimulated current (TSC) were investigated. The energy levels of the CRHT in GaSe:Co single crystals were located at 0.18, 0.28, 0.38, 0.49 and 0.57 eV above the valence band. The optical absorption peaks and the photoconductivity peaks corresponding to the CRHT were observed in the wavelength range from 650 to 950 nm and these peaks are respectively attributed to the carrier transitions from the CRHT to the indirect conduction band of GaSe:Co single crystals.     

Effects of surface adhesion of nonequilibrium charge carriers in the photoconductivity spectra of CdS crystals

The relaxation of low-temperature (T = 77 K) edge photoconductivity (PC) spectra of CdS crystals of the first group1 caused by the removal of the transverse electric field is investigated. A clearly manifested inversion of the fine (exciton) structure is found in the spectra during their relaxation to the initial form (existing before the application of the field). It is shown that the observed relaxation changes in the PC spectra of CdS are due to relaxation of the nonequilibrium surface charge appearing as a result of trapping of a part of the charge, induced by the transverse field into the sample, by slow surface states (adhesion levels). The experimental data on the effect of preliminary illumination by self-radiation on the edge PC spectra of the first-group CdS crystals indicating the existence of surface adhesion levels with a high density in these crystals are presented.     

Pure nuclear reflexes and combined hyperfine interactions in YIG

Mössbauer spectra of oriented YIG single crystals were taken and the numerical analysis using the transmission integral yielded a consistent set of hyperfine interaction parameters. They are in good agreement with theoretical values obtained by MO-calculations which included clusters up to 62 ions. Finally pure nuclear reflexes are predicted for single crystals and two theoretical spectra are given.Dedicated to U. Gonser on his 60. birthday     

无缺陷PbWO4晶体光学性质的模拟计算

利用完全势缀加平面波局域密度泛函近似研究PbWO4（PWO）晶体的光学性质.计算了完整的PWO晶体的电子结构、复数折射率、介电函数、光电导谱和吸收光谱.介电函数的虚部、吸收光谱、折射率等的峰值位置存在一一对应关系,这与电子从价带到导带的跃迁吸收有关.完整的PWO晶体在可见光范围内没有吸收,所以完整的PWO晶体是无色透明的晶体.     

Solid solutions of paradichlorobenzene in paradibromobenzene with vacancies present in their structure

The results of polarization studies of the low-frequency optical Raman spectra of solid solutions of paradibromobenzene with p-dichlorobenzene (10% paradichlorobenzene) are reported. The spectra of lattice vibrations of the mixed crystals are calculated, and it is shown that vacancies can be present in their structure, in agreement with the experimental spectra. The existence of vacancies is manifested by the appearance of secondary lines in the low-frequency spectrum, in the vicinity of 70 cm⁻¹. The intensities of the lines are related to the number of vacancies. The diffusion activation energies in mixed crystals of paradibromobenzene with paradichlorobenzene with vacancies present in their structure are calculated at different temperatures on the basis of the method of atom-atom potentials. It is shown that the activation energy in these mixed crystals is not as dependent on the temperature variation and the crystallographic direction as in crystals of the constituent components. Fiz. Tverd. Tela (St. Petersburg) 39, 1564–1566 (September 1997)     

Kinetics of transformation of Eu<Superscript>2+</Superscript> dimers in NaCl crystals in a static magnetic field of 15 T

A static magnetic field of up to 15 T is found to affect the photoluminescence excitation spectra of NaCl: Eu crystals. The magnetic field has an effect on the excitation spectra starting at the stage at which dimers are formed through diffusion in the crystals. At earlier stages of impurity aggregation, the magnetic field affects the kinetics of dimer accumulation. It is revealed that the dimer transformation stimulated by the magnetic field involves stages that last for 10–15 min at room temperature in a static magnetic field of 15 T and, hence, are shorter than the aggregation time. Luminescence studies of dimers, which are the main dislocation stoppers in NaCl: Eu crystals, make it possible to explain the specific features of the magnetoplastic effect observed previously in these crystals.     

Yb:Y3Al5O12/Y3Al5O12复合晶体的制作和光谱性能

采用热键合技术,制作中运用不同的工艺参量制作出12片Yb:Y3Al5O12/Y3Al5O12(Yb:YAG/YAG)复合.晶体.利用偏光显微镜对其键合界面进行了观察,研究了样品的透射光谱,从而确定出复合晶体合适的制作工艺.通过透射光谱的形状和透射率来表征复合晶体键合界面的质量.研究表明Yb:YAG/YAG复合晶体键合质量较好,可实现一体化.