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1.
在晶体拉曼散射张量的计算中,晶体空间群的C-G系数具有重要作用,本文利用本征函数法~[1],计算了一大类光学材料的结构空间群的C-G系数,同时给出波矢选择定则和C-G序列。  相似文献   

2.
D6h结构空间群C—G系数的计算   总被引:1,自引:1,他引:0  
在晶体拉曼散射张量的计算中,晶体空间的C-G系数具有重要作用。本文利用本征函数法,计算了一大类光学材料的D6h结构空间群的C-G系数,同时给出波矢选择定则和C-G序列。  相似文献   

3.
郝伟  刘凤艳 《光散射学报》1999,11(2):96-106
本文简要介绍了计算C G系数的生群元矩阵方程法,给出计算二十面体群C G系数时采用的简化计算方法,并给出了Ⅰ群C G系数的计算结果。  相似文献   

4.
一种新型晶体GdCa4O(BO3)3的非线性光学性能研究   总被引:1,自引:0,他引:1  
计算和测量了GCOB晶体的相位匹配曲线,理论计算与实验测量结果符合的很好。用电光调Q的Nd:YAG激光器对5mm和匠GCOB晶体进行了倍频研究,得到了26.7%的倍频转换效率。并与同样长度的BBO晶体进行比较,得出了GCOB晶体的有效非线性光学系数接近BBO晶体的有效非线性光学系数的结论。  相似文献   

5.
O8h结构磁空间群C-G系数的计算   总被引:6,自引:0,他引:6  
磁空间群相对于以往的空间群,在对物理图像的描述上更准确、更深刻。如它可在考虑晶体对称性的同时,也考虑到自旋磁矩的作用,因而它的C-G系数更加重要。本文利用本征函数法,计算了面心立方结构Oh^8磁空间群的C-G系数,以及波矢选择规则和C-G序列。  相似文献   

6.
众所周知晶体空间群的C G系数在晶体学中有重要的意义。而磁空间群的C G系数尚无人计算。本文利用磁群共表示理论构造出磁空间群的不可约表示 ,进而利用本征函数法计算了O1 0h 结构磁空间群的C G系数。  相似文献   

7.
我们采用超声“脉冲回波重合法”技术[1],测定了立方晶体钇铝柘榴石(YAG:)的二阶弹性常数,以及它们在静水压和单轴应力条件下,随压力变化,获得了三阶弹性常数.它们分别是:C11=334.78GPa,C12=109.95GPa,C44=115.25GPa,和C111=-3377.66GPa,C112=-841.16Gpa,C123=-32.86Gpa,C144=-37.66Gpa,C166=-579.38Gpa,C456=-114.60Gpa.根据这些数据,我们还计算了YAG:N_d ̄(3+)晶体的德拜温度以及Gruneisen参数,以及YAG:N_d ̄(3+)的状态方程.  相似文献   

8.
D_(6h)~4结构空间群C-G系数的计算   总被引:2,自引:0,他引:2  
在晶体拉曼散射张量的计算中 ,晶体空间群的C G系数具有重要作用 ,本文利用本征函数法[1] ,计算了六角密排结构D46h空间群的C G系数 ,同时给出波矢选择规则和C G序列。  相似文献   

9.
利用二维氢原子的SU(2)对称性,在Bargmann空间导出了二维氢原子的Clebsch-Gordan系数。  相似文献   

10.
热稳定法拉第旋转TbYbBiIG磁光单晶及性能   总被引:1,自引:0,他引:1  
张守业  张志良 《光学学报》1997,17(5):26-629
采用高温溶液法,以Bi2O3/B2O3为助熔剂成功地生长出掺铋复合稀土铁石榴石(TbYbBi)3Fe5O12(简称TbYbBiIG)晶体。晶体外形规则,最大尺寸为7×6×4mm3,X射线衍射分析证实,生长的晶体为TbYbBiIG单相单晶体,扫描电镜能谱分析其组成为Tb2.06Yb0.46Bi0.48Fe5O12。在1.0μm~1.7μm波段测量出晶体法拉第旋转谱和光吸收谱。当λ=1.55μm时,在10°C~80°C温度范围内测得法拉第旋转θF的温度系数为dθF/dT=-2.3×10-2deg·mm-1K-1。研究结果表明,TbYbBiIG单晶体在近红外波段θF约为YIG单晶的3倍,温度系数小,是制作高性能光隔离器的一种好材料  相似文献   

11.
In this paper we describe experiments conducted with high-power lasers that are attempting to replicate, for a very short time and in miniature, conditions found in the Sun. Experiments to date have reached conditions in the outer part of the Sun. To reach the Sun's centre requires compression of material to very much greater than solid density and heating to over ten million degrees. To achieve this, a new class of experiments and a new generation of high-power lasers are required.  相似文献   

12.
肖伯钧 《大学物理》2003,22(5):22-24
讨论了银道面内的引力场强分布和太阳在银河系中所受引力与到银心距离r的关系,指出引力场强g并不是与r的平方成反比,这是由于银河系的大小和形状不能忽略造成的.强调了万有引力定律的适用条件.  相似文献   

13.
The disagreement between the experimental and calculated positions of the first convergence zone are known from many publications. The most probable cause for such a disagreement, namely, the incorrect specification of the input data for the calculations, is considered. The lack of simultaneity between the hydrological surveys of the region and the acoustic experiments is emphasized. The experimental data obtained by the author in five ocean regions are presented. These data characterize the diurnal variability of the distance from the source to the nearest boundary of the convergence zone. The relations proposed by different researchers for calculating the sound speed from the temperature, salinity, and hydrostatic pressure are analyzed. It is shown that these relations lead to a substantial difference in the estimated depth dependence of the hydrostatic gradient of the sound speed. The position of the first convergence zone is calculated for the propagation conditions determined by vertical temperature and salinity profiles with the subsequent recalculation of these profiles into sound speed profiles by using eight different formulas known from the literature. It is shown that different formulas lead to different values of the distance to the first zone; this difference is substantially greater than that between the calculations and experiment. The necessity of improving the recalculation relations in view of the experimental data on sound propagation in natural oceanic waveguides, including the data on the actual positions of the convergence zones, is emphasized.  相似文献   

14.
Coulomb interaction in the hydrogen-like atom is investigated by using the scattering amplitude free from singularities. The quasipotential method makes it possible to obtain new contributions to the fine shift of energy levels to the sixth order in the fine-structure constant.  相似文献   

15.
Five major hyperfine interaction techniques, detected by nuclear radiation, originated in the short time span between 1950 and 1965. The coincidence with the demographic expansion, especially in Europe, of university education led to the creation of many new research laboratories applying these promising techniques in solid state physics, chemistry and biology. Since the turn of century many of the early pioneers are going into retirement, leading to a decline in activities in Europe, compensated in some degree by an increase in activities outside Europe. The organisation of the 2007 HI/NQI-conference was impeccable and took place in a superb setting. Thanks to all those involved in its organization.  相似文献   

16.
The biharmonic equation arises in a variety of problems in applied mathematics, most notably in plane elasticity and in viscous incompressible flow. Integral equation methods are natural candidates for the numerical solution of such problems, since they discritize the boundary alone, are easy to apply in the case of free or moving boundaries, and achieve superalgebraic convergence rates on sufficiently smooth domains, regardless of shape. In this paper, we follow the work of Mayo and Greenbaum and make use of the Sherman-Lauricella integral equation which is a Fredholm equation with bounded kernel. We describe a fast algorithm for the evaluation of the integral operators appearing in that equation. When combined with a conjugate gradient like algorithm, we are able to solve the discretized integral equation in an amount of time proportional to N, where N is the number of nodes in the discretization of the boundary.  相似文献   

17.
We consider associated production of squarks and gluinos with the lightest supersymmetric particle (LSP), or states nearly degenerate in mass with it. Though sub-dominant to pair production of color SU(3)-charged superpartners, these processes are directly sensitive to the wavefunction composition of the lightest neutralinos. Exploiting event-shape variables - including some introduced here for the first time - we are able to identify the composition of the LSP by selecting events involving a single high-pT jet recoiling against missing transverse energy. We illustrate the proposed technique on a set of benchmark cases and propose methods for applying these results in more realistic experimental environments.  相似文献   

18.
A method of determining the exact solutions to the Burgers equation on the basis of the Darboux transformation is described. It is shown that a single application of the Darboux transformation to the homogeneous Burgers equation transforms the latter into the inhomogeneous equation describing acoustic wave propagation against transonic flow in the de Laval nozzle. In this case, the contraction ratio of the nozzle is fixed and determined by the viscosity coefficient of the medium. Based on the exact solution of the homogeneous Burgers equation, for the aforementioned problem of the flow in the nozzle, all the possible regular steady-state solutions are presented and the evolution of nonstationary solutions is investigated. The algorithm of a multiple Darboux transformation, which allows an increase in the strength of inhomogeneity, i.e., in the contraction ratio of the nozzle, is determined. This approach leads to a discrete set of possible contraction ratios at which exact solutions can be obtained. The Crum’s theorem is used to derive a formula that allows determination of the exact solutions to the inhomogeneous Burgers equation from the solutions to the homogeneous heat transfer equation. It is noted that, in fact, the proposed algorithm of the multiple Darboux transformation makes it possible to decrease the viscosity coefficient of the medium in a discrete way.  相似文献   

19.
The adequacy of the model of high-temperature precipitation in dislocation-free silicon single crystals to the classical theory of nucleation and growth of second-phase particles in solids has been considered. It has been shown that the introduction and consideration of thermal conditions of crystal growth in the initial equations of the classical nucleation theory make it possible to explain the precipitation processes occurring in the high-temperature range and thus extend the theoretical basis of the application of the classical nucleation theory. According to the model of high-temperature precipitation, the smallest critical radius of oxygen and carbon precipitates is observed in the vicinity of the crystallization front. Cooling of the crystal is accompanied by the growth and coalescence of precipitates. During heat treatments, the nucleation of precipitates starts at low temperatures, whereas the growth and coalescence of precipitates occur with an increase in the temperature. It has been assumed that the high-temperature precipitation of impurities can determine the overall kinetics of defect formation in other dislocation-free single crystals of semiconductors and metals.  相似文献   

20.
Using the property of the simplest invariant built from the covariant derivatives of the curvature tensor to change sign on the Schwarzschild horizon, and the relativistic quadratic geodesic deviation equation to express the invariant in terms of locally measurable quantities, viz., separation, relative velocity and acceleration of test particles, a scheme is presented which can, in principle, be used by an imaginary observer to detect by local measurements the passage through the event horizon in the Schwarzschild spacetime.  相似文献   

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