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含多种玻璃生成体氧化物玻璃的振动光谱和结构 总被引:7,自引:0,他引:7
本文报导了以下三种含多种玻璃生成体氧化物玻璃系列的喇曼光谱和红外光谱:Ⅰ.SiO_2、P_2O_5-SiO_2、GeO-SiO_2以及GeO-P_2O_5-SiO_2。Ⅱ.15Na_2O·15BaO·10R_mO_n·60SiO_2、R_mO_n-B_2O_3、Al_2O_3、Ga_2O_3、SiO_2、GeO_2、TeO_2、Nb_2O_5。Ⅲ.以10%B_2O_3、GeO_2、TeO_2逐步代替15Na_2O·15BaO·70SiO_2中的SiO_2。注释了各振动峰值的相应的化学键振动方式,分析了在含碱金属和碱土金属氧化物玻璃中和在无碱和碱土金属氧化物玻璃中GeO_2和TeO_2的不同结构状态,指出含Al_2O_3玻璃的结构是均匀的,而含B_2O_3玻璃的结构是不均匀的. 相似文献
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群速度色散会限制太赫兹量子级联激光器频率梳的稳定以及频谱宽度.对于太赫兹量子级联激光器频率梳,其色散主要由器件增益、波导损耗、材料损耗引起.研究基于4.2 THz量子级联激光器双面金属波导结构,通过建立德鲁德模型,利用有限元法计算了激光器的波导损耗;器件未钳制的增益由费米黄金定则计算得到,结合增益钳制效应,计算了器件子带电子跃迁吸收以及镜面损耗,得到了器件钳制后的增益;利用Kramers-Kronig关系得到了器件的增益、波导损耗、材料损耗引起的色散,结果表明器件的激射区域存在非常严重的色散(–8×10~5—8×10~5 fs~2/mm).同时,计算了一种基于Gires-Tournois干涉仪结构的色散,结果表明,该结构的色散具有周期性,可以用于太赫兹量子级联激光器的色散补偿. 相似文献
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基于耦合场量子受激拉曼散射的太赫兹波辐射 总被引:5,自引:3,他引:2
使用两块长度各为65 mm的MgO:LiNbO3和无掺杂LiNbO3晶体,以1064nm的Q开关Nd:YAG激光器作为抽运光源,在12 mJ/pulse的抽运光能量下得到频率范围为0.34~2.90 THz的电磁辐射.分析表明,激光入射使LiNbO3晶体中具有电磁特性的横光学声子可以和入射光子形成耦合场量子.作为一种电磁特性的元激发,LINbO3晶体的耦合场量子的辐射场频率覆盖部分太赫兹频段范围,并可通过耦合场量子受激拉曼散射过程辐射THz波.根据耦合场量子辐射理论,通过分析晶体的耦合场量子色散特性曲线,可以确定该晶体能否辐射THz波及其带宽范围. 相似文献
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本文基于一种阶梯槽交错双栅周期慢波结构模型,获得了该结构中的电磁场分布公式.通过场匹配方法,求出了该结构的高频色散方程和耦合阻抗表达式.以W波段行波管用的阶梯槽交错双栅为例,利用本文公式和CST-MWS电磁软件比较计算了色散和耦合阻抗特性,分析了阶梯尺寸参数对高频特性(基模色散、+1次空间谐波归一化相速和耦合阻抗)的影响.结果表明,理论和CST-MWS软件模拟有很好的一致性;相对矩形交错双栅,改善了色散特性,拓展了基模带宽,同时具有足够大的耦合阻抗和适合工程应用的机械强度,在一定程度上可以弥补矩形交错双栅周期慢波结构的不足. 相似文献
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J. Petzelt I. Mayerová Č. Bárta L. D. Kislovskii 《Czechoslovak Journal of Physics》1973,23(8):845-854
Far infrared (30–430 cm?1) reflectivity measurements of Hg2Cl2 and Hg2Br2 single crystals have been performed in polarized light. The spectra, which are in agreement with group-theoretical predictions, were analyzed by the oscillator fitting procedure and Kramers-Kronig method. The results are compared with the existing data from other measurements and the large anisotropy of polar modes is briefly discussed. The polarization vectors of all long-wavelength symmetry modes were determined group-theoretically. 相似文献
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Janusz Mrozek Vedene H. Smith Jr. Dennis R. Salahub Piet Ros Alon Rozendaal 《Molecular physics》2013,111(3):509-517
Self consistent field-Xα molecular orbital calculations have been performed for Si2 and Cl2 using both the scattered-wave (SW) and LCAO discrete-variational (DV) versions of the method. For Si2 an SW calculation including f partial waves yields orbital densities in good agreement with those from methods which do not involve the muffin-tin approximation for the potential. The present results afford a further comparison relevant to the recent discussion (see, M. Schlüter et al. [9]) of the relative accuracy of various pseudocharge densities compared with real charge densities. The deformation density from the Xα-SW calculation is in good agreement with that from the DV-Xα method and also with that from the linear muffin tin orbital method (J. Harris and R. O. Jones [8]). Differences between the valence electron distribution which is usually discussed in connection with pseudopotential schemes, and the density distribution including the 2s and 2p core electrons are delineated. For Cl2, the Xα-SW deformation density shows positive lobes along lines through the atoms perpendicular to the bond axis, is negative for most of the area between the atoms and also shows negative lobes behind the atoms. This deformation map is in good qualitative agreement with the DV-Xα map and also with recent ab initio results with the exception of a small region at the centre of the bond in which the DV-Xα and ab initio results show an excess of electrons compared with the promolecule whereas the Xα-SW results show a deficiency. Comparisons with X-ray results on solid chlorine are inconclusive so that experimental electron scattering data on gas phase chlorine will be required to resolve this difference. 相似文献
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The temperature dependences of the conductivity and the thermoelectric coefficient in TlFeS2 and TlFeSe2 samples have been investigated in the temperature range 85–400 K. The variable-range hopping conduction has been established. It is found that the density of localized states N F near the Fermi level is 1.7×1018 and 3.3×1018 eV?1 cm?3, and the average hopping length R is 109 and 104 Å for TlFeS2 and TlFeSe2, respectively. The non-Arrhenius (activationless) behavior of the hopping conductivity is established in the temperature region T<200 K for TlFeS2 and T<250 K for TlFeSe2. 相似文献
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In BaF2 crystals, the linewidth of certain core band-conduction band excitons shows strong temperature dependence, while the corresponding linewidths in CaF2 and SrF2 do not. Calculations of the broadening due to the temperature-independent Auger effect are in good agreement with experimental data. 相似文献
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We have studied the peak effect (PE) phenomenon in single crystals of weakly pinned superconductors CeRu2 and 2H-NbS2. 2H-NbS2 is iso-structural and iso-electronic to 2H-NbSe2, whose similarity with CeRu2 as regards the PE representing the order-to-disorder transformation of the flux line lattice was claimed some time ago. We
report on the step change in equilibrium magnetization across the peak effect in CeRu2. We also present the vortex phase diagram of 2H-NbS2 obtained from the magnetization data, and compare the PE phenomenon in 2H-NbS2 and 2H-NbSe2. 相似文献
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Effects of chemical substitution in CeRu2Si2, a well-studied heavy fermion system and YbPd2Si2 have been investigated through magnetic susceptibility and x-ray diffraction in the systems CeRu
x
Si2, CeRu2−x
Os
x
Si2, CeRu2Si2−x
Ge
x
and YbPd2Si2−x
Ge
x
. Replacing silicon by germanium generates normal chemical pressure effect, namely, Ce and Yb atoms in CeRu2Si2 and YbPd2Si2 became more and less magnetic respectively. With increasing Ge concentration, CeRu2Si2−x
Ge
x
exhibits larger susceptibility at low temperature, goes to an antiferromagnetic state and finally becomes ferromagnetic.
In YbPd2Si2−x
Ge
x
, increasing Ge concentration drives Yb atoms to more divalent state. Electronic effects are more pronounced in CeRu2−x
Os
x
Si2 though CeRu2Si2 and CeOs2Si2 have very nearly the same lattice parameters. It is conjectured that CeRu2Si2−x
Ge
x
may be the first Ce-based heavy fermion having a magnetic ground state.
The authors felicitate Prof. D S Kothari on his eightieth birthday and dedicate this paper to him on this occasion. 相似文献
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In the infrared spectra of molecules with more than one C-H bond the symmetric and antisymmetric stretching bonds often overlap,
causing uncertainty in the intensity analysis. For CH2Cl2 and CD2Cl2 in the vapour state, the two bands overlap to such an extent that Straley who takes it as one band attributes it to antisymmetric
stretching while Saekiet al assign it to the symmetric stretching. Following the method of analysis initiated in this laboratory, we have solved this
problem by ultimately obtaining intensities separately forA
1 andB
2 species. The band is mostly due to the symmetric stretching, 0.06 out of the total of 0.31 contributing toB
2. Thus, this gives a method of separating the intensities of bands which are highly overlapping.
Presented at the Symposium on Crystallography and Crystal Physics, Osmania University, Hyderabad held on 5–7, December 1977. 相似文献
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A. Garnier D. Gignoux B. Ouladdiaf D. Schmitt T. Shigeoka 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(3):423-427
Single crystal magnetization measurements and powder neutron diffraction on tetragonal ErRu2Ge2 as well as anisotropy of the paramagnetic susceptibility and specific heat measurements on ErRu2Si2 are presented. Besides the huge crystal field contribution to the uniaxial anisotropy, which favors the basal plane, a strong
in-plane anisotropy is evidenced. From these features and neutron diffraction experiments it is shown that magnetic structures
of these materials are double-Q and accordingly non-colinear below their Néel temperature (5.2 and 6.0 K for Ge and Si based compounds, respectively). The
magnetic structures induced during the metamagnetic processes are discussed.
Received 24 December 1999 相似文献
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We have applied the pseudopotential theory to the calculation of exciton states and binding energies for the ionic crystals CaF2, SrF2, and BaF2, using a transfer model. Because of the satisfying agreement between our results and the experimental data in each case, we assume this pseudopotential formalism will describe transfer exciton states and energies in other ionic crystals. 相似文献
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The in-plane and out-of-plane resistivities of both 2H-TaSe2 and 2H-NbSe2 were determined down to 10 K. For both compounds, the resistivity anisotropy shows notably a slope change at temperatures where a CDW transition is expected to occur. On the other hand, for both compounds the resistivity anisotropy at the lowest temperature of measurement is much greater than expected by the Lawrence–Doniach model, which relates the critical magnetic field anisotropy to the normal state resistivity anisotropy for 3D-anisotropic superconductors. 相似文献