Luminescence centers in ceramics of yttrium, scandium, and bismuth oxytungstates

An investigation is made of the luminescence spectra of Me₂WO₆ ceramics (Me=Y, Sc, Bi). The spectra were decomposed into elementary components by the Alentsev—Fock method. Radiation hands with a maximum at 3.02 eV in the Y₂WO₆ luminescence spectrum, at 2.8 eV in the ScWO₆ spectrum, and at 2.93 eV in the Bi₂WO₆ spectrum are assigned to the light emission of self-localized Frenkel excitons. The bands with maxima at 2.25 and 1.75 eV in the Y₂WO₆ spectrum, at 2.36 and 1.9 eV in the Sc₂WO₆ spectrum, and at 2.35 and 1.9 eV in the Bi₂WO₆ spectrum are related to oxygen vacancies. Translated from Zhurnal Prikladnoi Spektroskopii, Vol 67, No. 2, pp. 273–275, March–April, 2000.     

AgI(Cr2O3)复合离子导体的光谱研究

本文研究了AgI(Cr₂O₃)复合离子导体的红外吸收光谱,近紫外、可见反射光谱。发现复合离子导体的两种谱图均与纯AgI,Cr₂O₃的不同。红外吸收光谱在882—889cm^-1处有一新吸收峰。电子谱中,AgI从430nm开始向长波方向表现的光离解特性消失。本来Cr₂O₃由配位场效应而引起的d—d吸收跃迁以410nm,530nm为中心的反射谱带,现在410nm处的谱带消失。530nm处的谱带稍有红移,且随加入Cr₂O₃量的增多而强度减弱。代之以整个紫外、可见区的较强吸收。对此,结合透射电子显微镜的分析,用双声子耦合和介质的变形极化以及配位场理论对AgI(Cr₂O₃)复合离子导体的声子谱和电子谱进行了解析。 关键词：     

Investigation of the luminescence spectrum of UO2MoO4

By time-resolved spectroscopy the intrinsic emission spectrum of UO₂MoO₄ at 4.2 K is obtained. The main progressions in the vibronic structure are identified as couplings with the A_g correlation field components of the symmetric and asymmetric UO₂ stretching modes. The intrinsic zero-phonon line in the emission and excitation spectrum is shown to be split both by the crystal field and correlation field. The steady-state emission spectrum at 4.2 K is dominated by emission from traps. The vibronic structure of the trap emission reveals that all traps are distorted uranyl groups.     

Experimental studies of the magnetic excitations in the 1D Ising-antiferromagnet CsCoCl3

The electronic Raman and infrared absorption spectrum within the ⁴T_1g ground term of the one dimensional antiferromagnet CsCoCl₃ is investigated. At 2K three magnon lines are observed whereas above the magnetic phase transition at 8K the number of lines is increased to twelve. No drastic change of the magnon spectrum is observed in passing the Neél temperature at 21.5K. The magnon spectrum could still be observed at 150K. Theoretically the one-exciton spectrum is described within the molecular field approximation, using an exchange coupling between nearest neighbours along the spin chains only. Satisfactory agreement is obtained between measured and calculated energies.     

An incoherent inelastic neutron scattering study of NH4TaWO6

The incoherent inelastic neutron scattering spectrum of the defect pyrochlore, NH₄TaWO₆, has been determined at 20 K. The appearance of the spectrum indicates that the NH ₄ ⁺ ion is distorted from its free ion tetrahedral geometry. A profile refinement method has been used to fit a calculated spectrum to the data based on an ion of C _3v symmetry.     

CF3CDCl2分子红外多光子光热吸收谱

本文报道用铂丝光热吸收池作为探测器得到了CF₃CDCI₂的红外多光子吸收谱。并发现在线性吸收谱中944cm^-1处的吸收峰在多光子吸收谱中分裂为947cm^-1和927cm^-1两个吸收峰。这一现象与科里奥利力和非谐性引起的简正振动的耦合作用有关。这样,在用CF₃CDCI₂/CF₃CHCI₂体系分离氘同位素时,可以根据这一新结果选择更合适的激发波长。实验还发现在线性吸收谱中986cm^-1处的吸收峰在多光子吸收谱中出现约6cm^-2的红移。这种红移现象起源于分子振动能级的非谐性。 关键词：     

Free exciton luminescence lineshape of Hg0.3Cd0.7Te

The photoluminescence spectrum of Hg_0.3Cd_0.7Te at 77K includes a narrow, high energy free exciton line. This experimental spectrum is in good agreement with the theoretical free exciton lineshape, the Gaussian broadening of this line is due to alloy inhomogeneity, and the binding energy of the bound exciton with respect to the free exciton at 77K is 13 ± 4 meV.     

Magnetic properties of R4Co3 (R = Gd, Y) compounds as observed by NMR

The zero field spin echo nmr spectrum of Gd₄Co₃ taken at 4.2 K is analysed and discussed on the basis of having magnetic moments of Co atoms at different structural lattice sites. For Y₄Co₃ the spin echo nmr spectrum taken as a function of the external field is discussed and explained on the basis of the coexistence of Co atoms carrying localized magnetic moments and paramagnetic Co atoms in this compound at determined structural sites.     

Vibronic spectrum of the U2 isoelectronic center in Si: In

The photoluminescence spectrum of Si:In measured at 2 and 4 K using samples from several suppliers has been found to be preparation sensitive. In particular, intensity variations allow us to distinguish a sharp no-phonon line at 1.118 eV, variously referred to as U₂ of P, and its associated vibronic spectrum from the In(NP) lines and their phonon replicas. Whereas the intensity of the latter did not show preparation sensitivity, the former has been observed to change by three orders of magnitude. The U₂ vibronics form a broad-structured spectrum containing density-of-states features. The appearance of phonons other than those conserving crystal momentum demonstrates the exciton is bound to a low symmetry site. In addition, the spectrum includes a peak at 1.109 eV, called R, and a shoulder at 1.107 eV which involves too small an energy loss to be density-of-states related, and these features are most likely modes of the U₂ impurity complex. This complex has been tentatively identified as an isoelectronic center composed of an indium-phosphorus nearest-neighbor substitutional pair.     

Luminescence centers in bismuth-containing oxytungstate ceramics

We have studied the photoexcitation and luminescence spectra of Bi₂WO₆, Y₂WO₆ and Y₂WO₆:Bi ceramics. We used the Alentsev-Fock method to decompose the spectra into elementary components. The emission bands with maximum at 2.93 eV in the luminescence spectrum of Bi₂WO₆, 3.02 eV in the luminescence spectrum of Y₂WO₆, and 2.95 eV in the luminescence spectrum of Y₂WO₆:Bi are assigned to luminescence of self-localized Frenkel excitons. The bands with maxima at 2.35 eV and 1.90 eV in the spectrum of Bi₂WO₆, 2.25 eV and 1.75 eV in the spectrum of Y₂WO₆, and 2.35 eV and 1.85 eV in the spectrum of Y₂WO₆:Bi are connected with oxygen vacancies. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 688–691, September–October, 2007.     

Optical absorption spectrum of diammonium nickel bis(tetrafluoroberyllate) hexahydrate

The optical absorption spectrum of diammonium nickel bis (tetrafluoroberyllate) hexahydrate (NH₄)₂Ni(BeF₄)₂.6H₂O has been investigated at the laboratory and liquid nitrogen temperatures. The spectrum is characteristic of the Ni²⁺ ion in an octahedral crystal field. Splitting of one of the bands at the liquid nitrogen temperature are attributed to the spin-orbit interaction.     

Raman spectroscopy of the sampleite group of minerals

Raman and infrared spectroscopy enabled insights into the molecular structure of the sampleite group of minerals. These minerals are based upon the incorporation of either phosphate or arsenate with chloride anion into the structure, and as a consequence the spectra reflect the bands attributable to these anions, namely, phosphate or arsenate with chloride. The sampleite vibrational spectrum reflects the spectrum of the phosphate anion and consists of ν₁ at 964 cm⁻¹, ν₂ at 451 cm⁻¹, ν₃ at 1016 and 1088 cm⁻¹ and ν₄ at 643, 604, 591 and 557 cm⁻¹. The lavendulan spectrum consists of ν₁ at 854 cm⁻¹, ν₂ at 345 cm⁻¹, ν₃ at 878 cm⁻¹ and ν₄ at 545 cm⁻¹. The Raman spectrum of lemanskiite is different from that of lavendulan consistent with a different structure. Low wavenumber bands at 227 and 210 cm⁻¹ may be assigned to CuCl transverse/longitudinal (TO/LO) optic vibrations. Raman spectroscopy identified the substitution of arsenate by phosphate in zdenekite and lavendulan. Copyright © 2007 John Wiley & Sons, Ltd.     

Raman spectrum of α and β-Pb3(PO4)2

The Raman spectrum of Pb₃(PO₄)₂ exhibits a progressive modification from the α to the β phase spectrum. No discontinuities are observed at the transition point.One soft mode of A_g type due to a translation mode parallel to the binary axis appears in the α phase.A strong broadening of the Rayleigh line is also observed above and below the transition point.     

Fourier spectrum of the signal generated at the point of period tripling bifurcation accumulation

The object of consideration is universal rules observed in the Fourier spectrum of the signal generated at the point where bifurcations tripling the complex analytical map period are accumulated. The difference in the intensities of subharmonics at frequencies corresponding to neighboring levels in the hierarchical levels in the spectrum is characterized by constant γ = 21.9 dB, which is an analogue of constant γ_F = 13.4 dB for the Feigenbaum critical point. Physical observations of the spectrum at the point of period tripling bifurcation accumulation are presented.     

The polarized reflectance spectrum of a novel organic conductor (BEDT-TTF)2ClO4(C2H3Cl3)0.5

The polarized reflectance spectrum of a novel organic conductor, (BEDT-TTF)₂ClO₄(C₂H₃Cl₃)_0.5 was measured at room temperature over the spectral region from 340 cm^-1 to 25000 cm^-1. The reflectance spectrum provided an evidence for the anisotropic two-dimensional character of this material. The optical conductivity spectrum exhibits the existence of an optical band gap of about 0.2 eV, suggesting that this material is a semimetal rather than a metal.     

Simultaneous excitation of cavity resonance and surface plasmon resonance in Ag/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/Ag layer structure

Simultaneous excitation of cavity resonance (CR) and surface plasmon resonance (SPR) was observed in the angular spectrum by substituting Ag/Al₂O₃/Ag layers for the metal film in a Kretschmann structure. Two reflective valleys, elicited respectively by CR and SPR, appeared at different positions in the angular spectrum. The former is the sum of enhanced transmission of CR and absorption of the metal, expressed in the reflection spectrum and extremely insensitive to the changes of the surface environment (refractive index). The latter behavior is like that when two metal films are stuck together: it has almost the same resonance depth and width, and is extremely sensitive to the changes of the surface environment. Moreover, two SPR peaks could be excited simultaneously at one angle but with different wavelengths in the frequency spectrum, which is not seen in traditional Kretschmann structures.     

Anelastic Relaxation Mechanisms Characterization by Mössbauer Spectroscopy

Anelastic behavior of crystalline solids is generated by several microstructural processes. Its experimental study yields valuable information about materials, namely: modulus, dissipation mechanisms and activation enthalpies. However, conventional techniques to evaluate it are complicated, expensive, time consuming and not easily replicated. As a new approach, in this work a Mössbauer spectrum of an iron specimen is obtained with the specimen at repose being its parameters the “base parameters.” After that, the same specimen is subjected to an alternated stress–relaxation cycle at frequency ω ₁ and a new Mössbauer spectrum is obtained under this excited condition; doing the same at several increasing frequencies ω _n in order to scan a wide frequencies spectrum. The differences between the Mössbauer parameters obtained at each excitation frequency and the base parameters are plotted against frequency, yielding an “anelastic spectrum” that reveals the different dissipation mechanisms involved, its characteristic frequency and activation energy. Results are in good agreement with the obtained with other techniques     

石英玻璃衬底上纤锌矿Mg0.25Zn0.75O薄膜的结构及光学性能

Mg_xZn_1-xO材料是一种新型光电功能材料.采用溶胶凝胶法在石英玻璃上制备了Mg_0.25Zn_0.75O薄膜,理论结合实验研究了Mg_0.25Zn_0.75O薄膜的结构和光学性能.研究表明,石英玻璃衬底上Mg_0.25Zn_0.75O薄膜呈六方纤锌矿结构,薄膜均匀,平均粒径约为20nm.吸收光谱表明吸收带边始于3 关键词： 0.25Zn_0.75O薄膜')" href="#">Mg_0.25Zn_0.75O薄膜 溶胶凝胶法 石英玻璃衬底 紫外发光     

Carbon dioxide concentration and temperature in flames by raman spectroscopy

The interpretation and prediction of high temperature Raman spectra for CO₂ in flames requires a more detailed treatment of the upper vibrational states than is required for room-temperature spectra. A method for calculating these upper state contributions is presented and is used to evaluate the results of a series of experiments. Laser Raman CO₂ spectra have been obtained for CH₄-air, CO₂ seeded CH₄-air, and CO-air flames. The results indicate that both the high and low temperature CO₂ spectra agree with the theoretical predictions. Comparison of the CO₂ temperature to the N₂ temperature, both measured at the same position in the flames, indicates a better prediction of temperature from the N₂ spectrum than from the CO₂ spectrum. Accurate values for the CO₂ concentrations, however, can be determined from a comparison of the CO₂ spectrum with the N₂ spectrum.     

Charged particle oscillator and hollow cathode He(II) lamps for high resolution photoelectron studies: C 2 s spectrum of CH 4 and Hg 5 d5/2 spectrum of (CH 3) 2Hg

Charged particle oscillator and hollow cathode He discharge lamps are described, and the performances of the two lamps in the same spectrometer are compared. Both lamps give high percentages of He(II) radiation, but the hollow cathode lamp gives higher overall He(I) and He(II) intensifies and has greater long term stability. The observed resolution for He(II) studies (～ 25 meV) is the same for both lamps. The C 2 s spectrum of CH ₄ and the Hg 5 d_5/2 spectrum of (CH ₃) ₂Hg demonstrate the performance of the hollow cathode lamp. In the CH ₄ spectrum, a vibrational progression is observed, and attributed to the totally symmetric stretching mode. The linewidth of individual components increases at higher binding energy. The high resolution of the (CH ₃) ₂Hg spectrum enables us to identify additional peaks not previously seen in this spectrum. The Hg 5 d orbital energy-ordering for Me ₂Hg is reassigned.