高剥离类钠离子3s2S—3d2电四极矩E2光谱跃迁的理论计算

 利用全相对论性多组态Dirac-Fock平均能级方法系统地计算了高剥离类钠离子3s²S—3d²D(Z=14～103）电四极矩E2光谱跃迁的能级间隔，跃迁几率和振子强度，计算中考虑了核的有限体积效应，Breit修正和QED修正，所得结果和最近的实验数据及理论计算值进行了比较，计算结果表明：高原子序数的高荷电离子的电四极矩E2光谱跃迁的跃迁几率和中性原子的电偶极E1的相当，在ICF和MCF高温高密度激光等离子体中，电四极矩E2光谱跃迁过程不容被忽视。     

Be,Mg和Ca原子电四极矩E2~1D—~1S跃迁的能级和跃迁概率

利用多组态DiracFock广义扩展平均能级(MCDFEAL)方法系统地计算了重要的中性原子Be,Mg和Ca单光子电四极矩E21D—1S光谱跃迁的能级间隔和跃迁概率,计算中考虑了重要的核的有限体积效应,Breit修正和QED修正,所得结果和最近的实验数据及理论计算值进行了比较.此外还从理论上预言了Ba和Mg单光子电四极矩E21D—1S光谱跃迁概率过程,在库仑规范中,跃迁概率A(Be)=38849s-1,跃迁概率A(Mg)=23572s-1和跃迁概率A(Ca)=481s-1.     

Be,Mg和Ca原子电四极矩E2^1D—^1S跃迁的能级和跃迁概率

利用多组态Dirac-Fock广义扩展平均能级（MCDF－EAL）方法系统地计算了重要的中性原子Be,Mg和Ca单光子电四极矩E2^1D－^1S光谱跃迁概率,计算中考虑了重要的核的有限体积效应,Breit修正和QED修正,所得结果和最近的实验数据及理论计算值进行了比较,此外还从理论上预言了Ba和Mg单光子电四极矩E2^1D－^1S光谱跃迁概率过程,在库仓规范中,跃迁概率A（Be)=3884.9s^-1,跃迁概率A（Mg)=2357.2s^-1和跃迁概率A（Ca)=48.1s^-1。     

高剥离类镁等电子序列的磁偶极MI和电四极E2光谱跃迁理论研究

利用全相对论性多组态Dirac-Fock广义平均能级方法,系统地计算了类镁离子3s3p 磁偶极M1 3 P2-3P1 和电四极E2 3 P2-3P0(Z=20～103)光谱跃迁的能级间隔、跃迁几率和振子强度.计算中考虑了原子核的有限体积效应,进行了高阶Breit修正和QED修正,所得到的能级间隔和最近的实验数据及理论计算值进行了比较.计算结果表明高原子序数的高荷电离子的磁偶极矩M1和电四极矩E2跃迁几率和中性原子的电偶极E1的相当,在ICF和MCF高温激光等离子体中,磁偶极矩M1和电四极矩E2跃迁过程不容被忽视.     

高剥离类镁等电子序列的磁偶极M1和电四极E2光谱跃迁理论研究

利用全相对论性多组态Dirac-Fock广义平均能级方法，系统地计算了类镁离子3s3p磁偶极Ml^3P2--^3P1和电四极E2 ^2P2--^3P0(Z=20-103)光谱跃迁的能级间隔、跃迁几率和振子强度。计算中考虑了原子核的有限体积效应，进行了高阶Breit修正和QED修正，所得到的能级间隔和最近的实验数据及理论计算值进行了比较。计算结果表明：高原子序数的高荷电离子的磁偶极矩M1和电四极矩E2跃迁几率和中性原子的电偶极E1的相当，在ICF和MCF高温激光等离子体中，磁偶极矩M1和电四极矩E2跃迁过程不容被忽视。     

偶偶核21+态电四极矩的局域关联与对数NpNn系统性规律

相邻原子核2₁⁺态的电四极矩之间的局域关联可由轴对称转子模型和非简谐振子模型推导得到。这种局域关联所对应的偏微分方程可以约束电四极矩的N_pN_n系统性演化,进而可以推得:在对数坐标的N_pN_n scheme中,电四极矩应具有线性演化特征。这一特征与偶偶核2₁⁺态的激发能及其跃迁至基态的约化跃迁几率的N_pN_n系统性规律类似。实验数据也证实了2₁⁺态电四极矩局域关联及对数N_pN_n线性演化特征是比较可靠的。使用这些局域关联与N_pN_n系统演化规律,还对未知电四极矩进行了预言,同时也减少了Ba同位素电四极矩实验数据上的不确定性。     

球形核振动中非简谐项的影响

本文在β,γ表象中考虑了非简谐项的影响,对四极表面振动的能量,E2跃迁及2₁⁺态的电四极矩进行了计算,并与实验作了比较。     

镁Mg3s~(21)S_0-3s3d~1D_2单光子电四极矩跃迁的研究

用原子束技术—激光共振电离—飞行时间质谱探测离子信号的方法，观察到了原子束中镁Ｍｇ３ｓ２１Ｓ０－３ｓ３ｄ１Ｄ２单光子电四极矩共振跃迁，并对实验结果进行了判断和分析。     

锶Sr,钡Ba和镭Ra的单光子电四极矩光谱跃迁的理论研究

用带有Ｂｒｅｉｔ和ＱＥＤ修正的全相对论多组态Ｄｉｒａｃ－Ｆｃｃｋ平均能级（ＭＣＤＦ－ＡＬ）模型,计算了碱土金属Ｓｒ、钡Ｂａ和镭Ｒａ的单光子电四极矩＾１Ｄ－＾１Ｓ跃迁的光谱能量间隔,最大跃迁几率和振子强度。计算中考虑了重要的相对论效应、电子关联效应和核的有限体积效应,所得的结果与国外早期发表的结果进行了比较,此外还首次从理论上预言了镭Ｒａ的单光子电四极矩＾１Ｄ－１Ｓ光谱跃迁。     

镁Mg2s^21S0—3s3d^1D2单光子电四极矩跃迁的研究

用原子束技术－激光共振电离－飞行时间质谱探测离子信号的方法，观察到了原子束中镁Ｍｇ３ｓ＾２１Ｓ０－３ｓ３ｄ＾１Ｄ２单光子电四极矩共振跃迁，并对实验结果进行了判断和分析。     

Phase transitions in 2D and 3D non-Heisenberg ferromagnets with temperature-dependent anisotropy

A model of a non-Heisenberg ferromagnet is considered in which the single-ion anisotropy constant is linearly dependent on temperature. The conditions are found under which phase transitions occur in 2D and 3D non-Heisenberg ferromagnets as the temperature is varied. It is shown that, in the case where the biquadratic interaction is dominant, quadrupole states can occur in the system, which are specified by the orientation of the quadrupole moment. As the temperature is varied, a phase transition between quadrupole states can occur in 2D magnets. Depending on the ratios between the material constants, this transition can be either a second-order phase transition with the continuously changing orientation of the principal axes of the quadrupole moment tensor or a first-order phase transition with hysteresis through a state with a nonhomogeneous distribution of the principal axes of the quadrupole moment tensor. In 3D magnets, the phase transition between quadrupole states is of the first order with hysteresis. Phase diagrams of the system are constructed.     

Competing interactions, the renormalization group, and the isotropic-nematic phase transition

We discuss 2D systems with Ising symmetry and competing interactions at different scales. In the framework of the renormalization group, we study the effect of relevant quartic interactions. In addition to the usual constant interaction term, we analyze the effect of quadrupole interactions in the self-consistent Hartree approximation. We show that in the case of a repulsive quadrupole interaction, there is a first-order phase transition to a stripe phase in agreement with the well-known Brazovskii result. However, in the case of attractive quadrupole interactions there is an isotropic-nematic second-order transition with higher critical temperature.     

硅材料场致等效二阶极化率张量的研究

具有反演对称中心的硅单晶在电场作用下体内的反演对称中心消失,因而理论上应产生偶数阶非线性极化率。从理论上根据矢量与张量的作用,利用(eχf2f)=χ(3).E这一关系和张量变换理论系统地阐述了硅材料在内建电场或外加电场的作用下,具体在方向分别沿[111][、110]和[001]的电场作用下,得到的等效二阶极化率张量(eχf2f)分别与C3v、C2v和C4v点群的二阶极化率张量具有相同的形式,说明在物理性质方面,硅的对称性由Oh群在相应方向电场作用下分别被降低为C3v、C2v和C4v群,因此应该具有相应对称性晶体的二阶非线性光学性质;提出了电场E沿任意方向时硅的等效二阶极化率张量e(χf2f)的计算方法,对研究硅材料和其他具有反演对称中心材料的场致二阶非线性光学性质实验具有指导意义。     

Sideband-resolved spectroscopy on the 4 2S(1/2)-3 2D(5/2) transition in single calcium ions by use of fundamental waves of diode lasers

The 4 2S(1/2)-3 2D(5/2) electric quadrupole transition in calcium ions, which is expected to be used in calcium-ion optical frequency standards, is spectroscopically investigated with a laser system that uses only fundamental waves of diode lasers as light sources. Four Zeeman components allowed by the selection rules for the electric quadrupole transition are identified. As for one Zeeman component, one large carrier and accompanying smaller first sidebands are observed, which implies that Lamb-Dicke confinement of the ion is achieved. The compact and reliable system for spectroscopy of single calcium ions described is advantageous for realization of practical optical frequency standards.     

Landau theory of shape phase transitions in the cranked interacting boson model

Landau theory of phase transitions is applied to quadrupole shapes of rotating atomic nuclei within the interacting boson model (IBM) with cranking. It is shown that the coherent-state method must be generalized to allow for non-Hermitian quadrupole tensors of the coherent-state coefficients, which results in important modifications of the cranking shape-phase diagram compared to previous non-IBM studies of rotating nuclei. The parameter space has two surfaces of the first-order phase transitions and a curve of the second-order phase transition at their intersection. The phase structure of the cranked IBM closely resembles systems with competing superconducting and normal phases.     

Sodium-23 MAS NMR study on nuclear quadrupole interaction in NA(1-x)Ag(x)NO2.

Ag-impurity effects on the first- and second-order quadrupole interaction (QI) at ²³Na site in an isomorphic mixed system, Na_1−xAg_xNO₂ (x=0, 0.0084, 0.026, 0.079, 0.094, 0.16), have been investigated by employing ²³Na (I=3/2) magic angle spinning nuclear magnetic resonance (MAS NMR) technique. The central transition (CT) and satellite transition (ST) are simultaneously observed with this system. From the spectral analysis, the quadrupole parameter and its distribution width are obtained as a function of Ag concentration. From the intensity loss of CT MAS centerband and of the envelope function of ST MAS sidebands due to impurities, the range of their influence on the second- and first-order QI is estimated. The estimated ranges contain the second and first neighbouring Na sites from the resonating ²³Na nucleus for the first- and second-order QI, respectively.     

Nuclear quadrupole resonance spectrum and transition from the incommensurate phase to the commensurate phase of a crystal

The relationships describing the nuclear quadrupole resonance spectrum in the vicinity of the transition from the incommensurate phase to the commensurate phase of a crystal are derived in the adiabatic approximation. It is demonstrated that the intensity of the nuclear quadrupole resonance peaks depends on the mutual orientation of the order parameter and the electric field gradient.     

Orbital angular momentum exchange in the interaction of twisted light with molecules

In the interaction of molecules with light endowed with orbital angular momentum, an exchange of orbital angular momentum in an electric dipole transition occurs only between the light and the center of mass motion; i.e., internal "electronic-type" motion does not participate in any exchange of orbital angular momentum in a dipole transition. A quadrupole transition is the lowest electric multipolar process in which an exchange of orbital angular momentum can occur between the light, the internal motion, and the center of mass motion. This rules out experiments seeking to observe exchange of orbital angular momentum between light beams and the internal motion in electric dipole transitions.     

关于三维各向同性谐振子径向矩阵元计算的讨论

根据广义Laguerre多项式的数学性质，导出了较为简单的三维各向同性谐振子径向矩阵元的普遍公式,并在这基础上计算了一些重要特殊情形的径向矩阵元: 矢径r整数次幂的平均值，电偶极跃迁矩阵元和电四极跃迁矩阵元. 关键词： 三维各向同性谐振子 径向矩阵元 广义Laguerre多项式 偶极跃迁 四极跃迁