共查询到20条相似文献,搜索用时 15 毫秒
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F.E. Faradzhev N.M. Gasanly A.S. Ragimov A.F. Goncharov S.I. Subbotin 《Solid State Communications》1981,39(4):587-589
Raman spectra of InS single crystals have been studied at different hydrostatic pressures up to 1.2 GPa. Mode-Grüneisen parameters have been obtained for Raman-active normal modes. It is shown that the variations observed in Raman spectra with growing pressure can be interpreted from the standpoint of the structural phase transition D122h → D174h in InS as the hydrostatic pressure continues to increase. The transition pressure has been evaluated at (7 ± 1) GPa. 相似文献
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K. I. Shmulovich Yu. E. Gorbaty G. V. Bondarenko 《Russian Journal of Physical Chemistry B, Focus on Physics》2012,6(8):907-911
The shifts of the main bands in the Raman spectra during isothermal pressurization up to 140 MPa for anthracene and 1 M solutions of NaClO4 and Na2WO4 are measured using an optical cell with sapphire windows. The resulting shifts in the maxima of the spectral bands (from 0.6 to 1.1 cm?1 per 100 MPa) are close to the published value for a 1 M Na2SO4 aqueous solution. 相似文献
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The temperature variation of the second order Raman spectra of RbI has been theoretically studied in three basic symmetries on the basis of the modified Born and Bradburn theory. The phonon frequencies and corresponding eigenvectors have been determined at the room temperature by employing a three body force shell model. It has been assumed that the major factor which governs the temperature dependence of Raman intensity is the occupation number and the changes in the phonon eigen data and the polarizability parameters with temperature have been ignored. Calculations have been made at three temperatures namely, 300,90 and 23 K and the theoretical results have been compared to the experimental Raman spectra. 相似文献
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Tsutomu Sato 《Pramana》1983,21(6):375-384
The first-order Raman spectra ofE
gandA
1g
modes in MnF2 crystal were measured at temperatures from 4.2 to 563 K, and the values of the linewidths obtained. The temperature dependence
of the linewidths was analyzed by the phonon dispersion curves based on the rigid ion model, and the result showed that it
was caused approximately by the cubic anharmonic term in crystal potential energy. 相似文献
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F. Venturini M. OpelR. Hackl H. BergerL. Forró B. Revaz 《Journal of Physics and Chemistry of Solids》2002,63(12):2345-2348
We report electronic Raman scattering measurements on Bi2Sr2(Y1−xCax)Cu2O8+δ single crystals at different doping levels. The dependence of the spectra on doping and on incoming photon energy is analyzed for different polarization geometries, in the superconducting and in the normal state. We find the scaling behavior of the superconductivity pair-breaking peak with the carrier concentration to be very different in B1g and B2g geometries. Also, we do not find evidence of any significant variation in the lineshape of the spectra in the overdoped region in both symmetries, while we observe a reduction of the intensity in B2g upon decreasing photon energies. The normal state data are analyzed in terms of the memory-function approach. The quasiparticle relaxation rates in the two symmetries display a dependence on energy and temperature which varies with the doping level. 相似文献
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We have observed Raman scattering in NH4C? from 105K to 295K and up to 7kbar hydrostatic pressure, including the disordered phase II and the ordered phase IV. The pressure dependences of internal and lattice modes are reported, as well as that of the libration mode. The results are applied to several theories of the potential barrier to rotation. 相似文献
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Daniel P. Pereira Paulo C. de Oliveira Claudio M.R. Remédios Sanclayton G.C. Moreira Francisco F. de Sousa J. Mendes Filho P.T.C. Freire F.E.A. Melo 《Solid State Communications》2012,152(12):1023-1026
High-temperature Raman scattering measurements of KDP doped with Ni (1% weight) were performed over the spectral range 50–1200 cm?1. The X-ray powder diffraction patterns taken at room temperature and analyzed by Rietveld refinement showed that doped samples of KDP:Ni have the same tetragonal structure of a pure KDP crystal, but with a contraction of the crystalline cell. The behavior of the high-temperature Raman spectra indicate that two phase transitions occur, one at 413 K and another one at 443 K. These phase transitions occur at temperatures below the thermal dehydratation point, 488 K. DTA and TGA measurements reveals that KDP:Ni and pure KDP have the same thermal dehydratation temperature. 相似文献
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利用群理论详细分析了磷酸二氢钾(KDP)晶体的拉曼振动模式,得出了其拉曼振动模的归类?并采用拉曼光谱仪测量了Z切退火KDP晶体X(ZZ)X,Z(XY)Z和Y(XY)X三种散射配置和未退火KDP晶体Z(XY)Z配置下的拉曼光谱?根据拉曼选择定则得出X(ZZ)X,Z(XY)Z和Y(XY)X散射配置下的拉曼峰分别对应A1,B2(LO)?B2(TO)对称类振动模,但在Z(XY)Z配置下的拉曼光谱中除了B2模,还观察到了A1模,而在Y(XY)X配置下的拉曼光谱中只有B2模,且退火和未退火晶体Z(XY)Z配置下的拉曼光谱无明显差别,此结果表明KDP晶体的对称性降低,在背向散射时A1模也具有角度特性,但与晶体的内应力无关,这是由KDP晶体内部结构决定的? 相似文献
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利用群理论详细分析了磷酸二氢钾(KDP)晶体的拉曼振动模式,得出了其拉曼振动模的归类。并采用拉曼光谱仪测量了Z切退火KDP晶体X(ZZ)珡X,Z(XY)珚Z和Y(XY)X三种散射配置和未退火KDP晶体Z(XY)珚Z配置下的拉曼光谱。根据拉曼选择定则得出X(ZZ)珡X,Z(XY)珚Z和Y(XY)X散射配置下的拉曼峰分别对应A1,B2(LO),B2(TO)对称类振动模,但在Z(XY)珚Z配置下的拉曼光谱中除了B2模,还观察到了A1模,而在Y(XY)X配置下的拉曼光谱中只有B2模,且退火和未退火晶体Z(XY)珚Z配置下的拉曼光谱无明显差别,此结果表明KDP晶体的对称性降低,在背向散射时A1模也具有角度特性,但与晶体的内应力无关,这是由KDP晶体内部结构决定的。 相似文献
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Raman scattering and optical absorption in crystalline S4N4 have been measured both as a function of pressure at 295 K and low temperatures. Polarized single crystal Raman data were also obtained as an aid in the assignment of the Raman active phonons. The pressure coefficients of the Raman active external and S-S stretching modes show a discontinuity near 7 kbar indicative of a second order phase change. The optical absorption edge at about 2.5 eV of a sublimed film of S4N4 shows red shifts of 1.3 × 10?5 eV bar?1 and 6.3 × 10?4 eV K?1 with pressure and temperature respectively. In the light of these results, the electronic, vibrational and structural properties of the crystal are discussed. 相似文献
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The experimental Raman spectra of graphene exhibit a few intense two-phonon bands, whichare enhanced through double-resonant scattering processes. Though there are manytheoretical papers on this topic, none of them predicts the spectra within a single model.Here, we present results for the two-phonon Raman spectra of graphene calculated by meansof the quantum-mechanical perturbation theory. The electronic and phonon dispersions,electronic lifetime, electron-photon and electron-phonon matrix elements, are all obtainedwithin a density-functional-theory-based non-orthogonal tight-binding model. We studysystematically the overtone and combination two-phonon Raman bands, and, in particular,the energy and polarization dependence of their Raman shift and intensity. We find thatthe ratio of the integrated intensities for parallel and cross polarized light for alltwo-phonon bands is between 0.33 and 0.42. Our results are in good agreement with theavailable experimental data. 相似文献
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The temperature dependence of the Raman bands of Cr4+ modes which show enhanced intensities due to pre‐resonance effects is reported from 293 to 673 K in chromium‐doped titanite (CaTiOSiO4). Some aspects of the temperature dependence of Raman bands in pure, synthetic titanite which have not been previously published are also included in this study. Two Raman‐active components of Ag and Bg symmetry, respectively, of the symmetric Si–O mode in titanite are predicted under P21/a symmetry and also been identified in this phase for the first time. The one component of Bg symmetry disappears just above the antiferroelectric–paraelectric transition at ~500 K in accordance with the predictions under A2/a symmetry for the high‐temperature phase. Two resonance‐enhanced components of the Cr4+–O stretch are also evident in the P21/a phase and only one could be identified in the A2/a phase, again in accordance with group‐theoretical predictions. These observations can be used to characterize the P21/a and A2/a phases of pure synthetic and chromium‐doped titanite. The temperature dependence of the Cr4+–O modes can be approximated by two‐dimensional Ising behavior with the critical exponent β ≈ 1/8 below 450 K. Between 450 and 498 K, anomalous behavior is observed and this could be due to the appearance of mobile anti‐phase boundaries (APBs). Anomalous behavior also persists to temperatures above 500 K. The half‐width of the Ti–O stretching mode reflects the influence of the order parameter (Ti–O displacements) as well as mobile anti‐phase boundaries. No evidence could be found of the existence of other ions such as Cr4+‐ions in Ti‐sites and/or Cr3+‐ions also in Ti‐positions in Cr‐doped titanite in the Raman spectra using different laser lines to excite the spectra. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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