电多极矩跃迁选择定则的对称分析

只有由群的对称性才可能导出每个不可约表示的对称性波函数, 即对称化基函数.也只有由群的对称性才可能导出电子状态跃迁的最一般选择定则 , 即电偶极跃迁E1, 电四极跃迁E2 和 电八极跃迁E3跃迁的选择原则. 本文以 和 为例, 导出电多积跃迁的选择原则. 角动量的选择定则只是特例. 并用方法SAC-CI/6-31G 计算了 H2O和 CC的基态以及其激发态的激发能和振子强度.本文只适合单光子过程. 计算都与理论相合.     

γ跃迁中K选择定则的完整形式

从γ跃迁概率和原子核的转动谱,以及科里奥利耦合项出发,讨论了K禁戒及其消除,给出了γ跃迁中△K的取值范围和完整的K选择定则的数学形式,准确体现了K选择定则的内在涵义.     

含有复杂耦合的介观LC电路能级跃迁的选择定则

包含小型固态器件的介观电路因其易于集成、可大规模化的特点,在众多可能实现量子计算的方案中备受关注。本文利用正则量子化方法,给出了含有复杂耦合的介观LC电路的量子化方案,得到了该系统的能量算符;通过与一维量子谐振子相类比,并借助于幺正变换,导出了系统的能级公式及其态矢量表达式。在此基础上,讨论了介观电路两支路中电容器某一极板上的电荷量及穿过两线圈的等效磁通量在基态下的均方量子涨落。另外,考虑到一旦受到外电磁场的辐照,介观电路的状态将会改变,并可在相应能级之间发生跃迁,利用“不变本征算符”方法,得到了该系统能级跃迁的选择定则。     

稀土离子激活发光材料中能级跃迁的选择定则

能级跃迁的选择定则可用于判别含稀土离子的发光材料中的光吸收、能量传递和发光及非辐射能量弛豫过程是否发生.本研究中,我们根据跃迁所涉及到的电子组态、稀土离子所处格位的对称性、跃迁所涉及到的多重态及晶格振动情况进行了细致地讨论分析.对于光吸收和发射过程,我们得到了和相关文献报道一致的结果,并对有些结果进行了更细致的解释.对...     

欣赏对称

文章从一般对称、守恒、相对论、量子物理及对称自发缺损几方面漫谈对称性是物理学的基本属性 .     

半导体中多光子吸收跃迁速率的全量子理论分析

本文从非线性光学中辐射跃迁速率的表达式出发,在全量子理论下,导出了半导体中任意阶多光子吸收跃迁速率的一般表达式。理论分析结果表明,n光子吸收跃迁速率与光强的n次方和n阶光子相干度成正比。本文在多能带及二能带理论模型下,对多光子吸收跃迁速率的一般表达式进行了化简,并对非线性相互作用项对跃迁速率的贡献,作了讨论。     

非整数量子跃迁

证明频率为v的辐射引起的量子跃迁中,跃迁系统始末两态能量差不必是hv的整数倍。跃迁的玻尔条件和光电效应的爱因斯坦定律都是微扰近似的结果,在强激光引起的跃迁中不成立。We prove that in the quantum transition of a system induced by the radiation of frequency v, the energy difference between the initial and the final states of the system is not necessarily being an integer multiple of hv. The Bohr condition for quantum transitions and the Einstein law for photo-electric effects are approximate results of perturbation. They are violated in the transitions induced by intense lasers.     

在Feshbach-Kerman-Koonin多步理论中P及Q空间的跃迁

存在直接作用时, 在哈密顿量中将包括非对角元, 并导致Feshbach,Kerman和Koonin预平衡反应多步复合理论中P和Q空间的耦合, 得到了理论上更严格的Feshbach, Kerman和Koonin预平衡反应多步复合理论与复合核反应Hauser-Feshbach理论的统一表示, 也改进了与实验结果的符合.     

The binatural orbitals of electronic transitions

The well-known natural orbitals are defined as eigenfunctions of a one-particle reduced density operator, and can be obtained from a computed density matrix by diagonalization. Similarly, in this article we define the binatural orbitals, which are obtained for a pair of wave functions by a singular value decomposition of a reduced transition density matrix. The pair of states would usually be eigenstates of the electronic Hamiltonian, and the binatural orbitals then serve as a useful tool for the analysis of the transition between these states. More generally, application to any two state functions gives important information as to how the two states differ. Some examples are shown.     

Valley selection rule in a Y-shaped zigzag graphene nanoribbon junction

The valley valve effect was predicted in a straight zigzag graphene nanoribbon （ZGR） p/n junction. In this work, we address a possible valley selection rule in a Y-shaped ZGR junction. By modeling the system as a three-terminal device and calculating the conductance spectrum, we found that the valley valve effect could be preserved in the system and the Y-shaped connection does not mix the valley index or the pseudoparities of quasiparticles. It is also shown that the Y-shaped ZGR device can be used to separate spins in real space according to the unchanged valley valve effect. Our finding might pave a way to manipulate and detect spins in a multi-terminal graphene-based spin device.     

The black-box fast multipole method

A new O(N)$O(N)$ fast multipole formulation is proposed for non-oscillatory kernels. This algorithm is applicable to kernels K(x,y)$K(x\text{,}y)$ which are only known numerically, that is their numerical value can be obtained for any (x,y)$(x\text{,}y)$. This is quite different from many fast multipole methods which depend on analytical expansions of the far-field behavior of K  , for |x-y|$|x-y|$ large. Other “black-box” or “kernel-independent” fast multipole methods have been devised. Our approach has the advantage of requiring a small pre-computation time even for very large systems, and uses the minimal number of coefficients to represent the far-field, for a given L²$L^2$ tolerance error in the approximation. This technique can be very useful for problems where the kernel is known analytically but is quite complicated, or for kernels which are defined purely numerically.     

Quantum phase transitions in electronic systems

Quantum phase transitions occur at zero temperature when some non‐thermal control‐parameter like pressure or chemical composition is changed. They are driven by quantum rather than thermal fluctuations. In this review we first give a pedagogical introduction to quantum phase transitions and quantum critical behavior emphasizing similarities with and differences to classical thermal phase transitions. We then illustrate the general concepts by discussing a few examples of quantum phase transitions occurring in electronic systems. The ferromagnetic transition of itinerant electrons shows a very rich behavior since the magnetization couples to additional electronic soft modes which generates an effective long‐range interaction between the spin fluctuations. We then consider the influence of rare regions on quantum phase transitions in systems with quenched disorder, taking the antiferromagnetic transitions of itinerant electrons as a primary example. Finally we discuss some aspects of the metal‐insulator transition in the presence of quenched disorder and interactions.     

C原子、离子光电离过程的规律研究

基于Dirac-Slater自洽场方法,计算了C原子及各价离子从低能到高能的光电离截面。通过各种理论计算结果的比较,分析了Kramers公式的适用性。定量地考察了多极效应和相对论效应在不同能区对光电离截面的影响,并研究了光电离截面随光子能量、壳层、电离度变化的规律。     

Coarse-graining approach to first-order phase transitions

On an example of a simple spin system with two ground states and no symmetry, we show how to control low-temperature systems near first-order phase transitions by a straightforward renormalization group argument. The method, as opposed to the Pirogov-Sinai approach, also works for complex Hamiltonians.     

局域单PT对称势中多级孤子的传输特性研究

具有Parity-Time(PT)对称性的光学系统是近年提出的一种新型光学结构,在光开关、光子信息处理器件等方面具有潜在的应用。研究了局域单PT对称光学系统中双级孤子和三级孤子的存在范围与稳定特性。研究结果表明:多级孤子存在一临界传播常数,传播常数对应了线性模下的本征值。双级孤子和三级孤子仅能在较深的PT对称势中才能稳定地传输。多级孤子的稳定性的范围随着PT对称势的深度增加而扩大;孤子的能量随着传播常数的增大而增加,但随着PT对称势的调制深度的增加而减少。     

非局域非线性介质中多极表面光孤子的解析解及其稳定性分析

本文主要对非局域非线性介质中存在的多极表面亮孤子进行了研究. 理论研究表明多极表面孤子也可以被看做是具有反对称振幅分布的体孤子的一半, 由此我们可以给出多极表面孤子的解析解. 其次, 用数值计算的方法给出了它的数值解, 比较结果表明数值解与解析解基本符合. 最后, 研究了本模型下的多极表面孤子的稳定性, 发现二极表面孤子的不稳定区间比四极体孤子的不稳定区间小, 另外, 二极以上的表面孤子皆不稳定.