電子

电子的發現 電子是目前我們所知道的構成物質的基本成分之一。它有一定的質量、一定的電荷以及一系列其他的性質。它的運動規律,我們也知道得相当清楚。然而我們对於电子的一切認識並不是那一位物理学家在一朝一夕之間完成的。而是在很長的年代中,經过無數科学家繼续不断、一再深入地研究自然現象的結果。在科学研究的範圍內,人們对於自然現象的認识过程是一個逐步深入的过程。平時的研究工作僅為人們对於自然界的認識积累更多的事实和数據。到了具有重大意义的發現出現之     

坡密子和胶子球

讨论了高能强子 -强子散射过程中的坡密子以及坡密子的 QCD内容 .认为坡密子有可能就是具有量子数 IG=0 + ,JPC=2 + +的张量胶子球 ξ( 2 2 30 ) .用雷其化胶子球模型计算了高能质子 -质子散射截面和坡密子 -核子的耦合参数 β.理论结果与实验的要求一致. The pomeron in high energy hadron hadron scattering as well as the QCD nature of the pomeron are discussed. We claimed that the pomeron may be the tenser glueball ξ(2 230) with quantum number I G =0 +, J PC =2 ++ . Under this reggeized glueball model the cross section of high energy proton proton scattering and the coupling parameter of the pomeron nucleon, β , are calculated. The theoretical results of the present model are in good agreement with experimental data.     

声子角动量与手性声子

在经典的物理学理论中,声子广泛地被认为是线极化的、不具有角动量的.最近的理论研究发现,在具有自旋声子相互作用的磁性体系(时间反演对称性破缺)中,声子可以携带非零的角动量,在零温时声子除了具有零点能以外还带有零点角动量;非零的声子角动量将会修正通过爱因斯坦-德哈斯效应测量的回磁比.在非磁性材料中,总的声子角动量为零,但是在空间反演对称性破缺的六角晶格体系中,其倒格子空间的高对称点上声子具有角动量,并具有确定的手性;三重旋转对称操作给予声子量子化的赝角动量,赝角动量的守恒将决定电子谷间散射的选择定则;此外还理论预测了谷声子霍尔效应.     

孤立子

近几年来,在数学、物理、工程技术等许多领域的文献中,经常可以看到孤立子 (Soliton)这样一个陌生字眼。虽然这个新概念诞生在本世纪六十年代,而它的前身──孤立波(Solitary Wave)的发现要追溯到一百多年前英国科学家J.S.罗素(Russell)的一次壮观的奇遇。这事发生在1834年8月,他报导说:我观察过一次船的运动,这条船被两匹马拉着沿一条狭窄的运河迅速前进。突然船停了,被船体带过来的水聚集在船头周围,激烈地震荡着,然后突然离开船头,一个圆形的、光滑的、轮廓分明的巨大孤立水峰急速在水面上平移。在行进中,它的外形和速度并不改变。我…     

声子

前言 声子(phonon)是固体物理和近代声学中的一个重要基本概念.但一般固体物理、统计物理和声学的教科书或参考书中,对这一概念的介绍非常简单,甚至有一些不妥的说法,如认为“声子就是晶格振动中的简谐振子.”[1]为了使大家对声子有一个准确而完整的概念,本文拟就声子的引入、声子的性质进行较为详细的讨论.一、声子概念的引入 声子的概念首先是在研究晶格振动时引入的[2].晶格振动是晶体中诸原子(离子)集体在作微振动,其结果表现为晶格中的格波. 由量子力学可知,用经典力学的物理量来描述微观粒子,只能在一定的近似程度内做到.当作为粒子处…     

轻子和层子的复合模型

本文评述了近年中关于轻子和层子复合模型的工作,讨论了其中理论方面和唯象方面的问题并介绍了一些有代表性的模型。     

拓扑声子与声子霍尔效应

拓扑学与物理的结合是近几十年物理学蓬勃发展的一个新领域,它不仅活跃在量子场理论以及高能物理中,更广泛地存在于凝聚态物理体系中,包括量子(反常、自旋)霍尔效应和拓扑绝缘体(超导体)等.声子是凝聚态体系中热输运的主要载体;最近由于各种声子器件的发现,声子学得到了广泛的关注.本文介绍了声子的拓扑性质以及声子的霍尔效应现象,分别评述了在破坏时间反演对称、破坏空间反演对称、以及同时破坏时间和空间反演对称三种情况下所产生的声子霍尔效应、声子谷霍尔效应等相关物理研究进展.最后对拓扑学在其他声学体系中的应用做了简单介绍,并进一步讨论了其未来的发展方向.     

固体中的极化子与双极化子

离子晶体通常具有较高的介电常数,带电粒子在晶体中会引起介电极化,其作用相当于一个可以束缚粒子的势阱.若粒子在势阱中的状态是稳定的,就有可能形成所谓的极化子与双极化子.本文采用一种简化的处理方法,将晶体材料当作各向同性的均匀介质,主要利用经典物理图像和三维量子谐振子模型,分别计算了介质中极化子与双极化子的基态能量,并进行了简要的理论分析.     

轻子和层子的复合模型

本文评述了近年中关于轻子和层子复合模型的工作,讨论了其中理论方面和唯象方面的问题并介绍了一些有代表性的模型。     

三光子矢量模型

本文指出,由Feynman,Vernon和Hellwarth建立的二能级系统的光学Rabi进动模型,不仅可以推广应用于双光子共振相干作用过程的讨论,也能推广应用到三光子共振相干作用过程。利用此模型和绝热跟随近似,得到了在强场和(或)共振条件下不同于微扰论结果的三级极化公式。讨论了三级共振非线性效应中出现饱和的问题。 关键词：     

Application of the Bogolyubov inequality to the calculation of thermodynamic functions of triatomic molecules

The Bogolyubov inequality is used in the calculation of the vibrational part of of thermodynamic functions of triatomic molecules where the vibrations are anharmonic. By variation of parameters in the approximate Hamiltonian, we obtain the best agreement between the free energy of the system based on the approximate Hamiltonian, and the exact free energy-of the system. The method is applied to the calculation of the thermodynamic functions for H₂O and C₃.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 3–6, January 1983.     

The large-amplitude motions in quasi-symmetric top molecules with internal C3v rotors: The vibration-torsion-rotation Hamiltonian of a two-top molecule

An expression for the vibration-torsion-rotation Hamiltonian of a molecule with triatomic nonrigid frame and two internal C_3v rotors has been derived. Three large-amplitude motions, namely skeletal bending and two torsions, are removed from the vibrational problem and are considered together with the rotational problem. The Hamiltonian obtained is applicable to any two-C_3v-top molecule with triatomic linear or bent frame. The zeroth-order skeletal bending-torsion-rotation Hamiltonian is derived and the method of solving the corresponding Schrödinger equation is discussed. The Hamiltonian obtained with only slight modifications is shown to be applicable to any single-C_3v-top molecule with a quasi-linear tetratomic nonrigid frame or to the problem of the large-amplitude bending motion in a pentatomic quasi-linear molecule.     

Vibration-inversion-rotation spectra of ammonia. A vibration-inversion-rotation Hamiltonian for NH3

A new model Hamiltonian has been developed to study the vibration-inversion-rotation energy levels of ammonia. In this model the inversion motion is removed from the vibrational problem by allowing the molecular reference configuration to be a function of the large amplitude motion coordinate. The treatment follows closely that developed by Hougen, Bunker, and Johns for the study of triatomic molecules.The numerical methods that have been used to solve the zeroth-order Hamiltonian describing the inversion-rotation energy levels of NH₃ and ND₃ in the ground vibrational state are discussed. Certain group-theoretical problems concerning the symmetry classification of the states of ammonia are also discussed.     

动力学对称群方法对三原子分子高激发振动态的理论研究

利用动力学对称群方法研究了弯曲三原子分子的振动高激发态能谱-该方法显示：三原子分子的动力学对称性为U₁(4)U₂(4),则三原子分子的Hamiltonian量可写成代数的各元素之和,通过李代数处理而求得分子代数Hamiltonian量的本征值,进而得到分子的振动能谱-并具体计算了O₃分子- 关键词：     

Perturbative Handling of the Renner-Teller Effect and Spin-Orbit Coupling in Δ Electronic States of Triatomic and Tetra-atomic Molecules

Second-order perturbative formulae for handling the Renner-Teller effect combined with the spin-orbit coupling in Δ electronic states of triatomic and symmetric (ABBA-type) tetra-atomic molecules with linear equilibrium geometry are derived via two schemes for partition of the model Hamiltonian. The formulae for triatomic molecules are employed to compute the spectrum of the X⁵Δ_g state of FeH₂. The parameters entering the model Hamiltonian are generated by means of ab initio calculations.     

Lie algebraic approach to the time-dependent quantum general harmonic oscillator and the bi-dimensional charged particle in time-dependent electromagnetic fields

We discuss the one-dimensional, time-dependent general quadratic Hamiltonian and the bi-dimensional charged particle in time-dependent electromagnetic fields through the Lie algebraic approach. Such method consists in finding a set of generators that form a closed Lie algebra in terms of which it is possible to express a quantum Hamiltonian and therefore the evolution operator. The evolution operator is then the starting point to obtain the propagator as well as the explicit form of the Heisenberg picture position and momentum operators. First, the set of generators forming a closed Lie algebra is identified for the general quadratic Hamiltonian. This algebra is later extended to study the Hamiltonian of a charged particle in electromagnetic fields exploiting the similarities between the terms of these two Hamiltonians. These results are applied to the solution of five different examples: the linear potential which is used to introduce the Lie algebraic method, a radio frequency ion trap, a Kanai–Caldirola-like forced harmonic oscillator, a charged particle in a time dependent magnetic field, and a charged particle in constant magnetic field and oscillating electric field. In particular we present exact analytical expressions that are fitting for the study of a rotating quadrupole field ion trap and magneto-transport in two-dimensional semiconductor heterostructures illuminated by microwave radiation. In these examples we show that this powerful method is suitable to treat quadratic Hamiltonians with time dependent coefficients quite efficiently yielding closed analytical expressions for the propagator and the Heisenberg picture position and momentum operators.     

The molecular Hamiltonian in internal coordinates

A systematic approach for the derivation of the exact translational–rovibronic (non-relativistic) Hamiltonian for a polyatomic molecule consisting of N nuclei and n electrons is presented. All coupling terms which contribute to the total energy are identified. The Hamiltonian is greatly simplified by taking the internal coordinates (bond lengths and bond angles) as the vibrational variables. The translational–rovibronic Hamiltonian of triatomic molecules are considered as an application for this general formulation.     

Photodissociation dynamics of triatomic molecule in presence of pulsed and bichromatic laser field

The photodissociation dynamics of a triatomic molecule in the presence of pulsed and bichromatic electric field have been investigated. We have considered MgH₂ molecule in its ground state potential energy surface. The time-dependent Fourier Grid Hamiltonian method is invoked to follow the dissociation dynamics as a function of field strength, frequency, phase difference, etc.     

New ab initio Potential Energy Surfaces for Cl(2P3/2, 2P1/2)+H2 Reaction

采用多参考组态相互作用的计算方法和很大的基组构造了Cl+H₂反应体系的一组新的三维从头算势能面. 该势能面包含Cl+H₂体系的能量最低的三个绝热态,并在非绝热近似下转化为四个非绝热势能面. 另外,旋轨耦合矩阵元也基于Breit-Pauli Hamil-tonian计算得到. 对角化这四个非绝热势能和两个旋轨耦合矩阵元组成的全耦合Hamiltonian,得到了三个考虑旋轨耦合后的绝热势能面.基于这组新势能面的非绝热动力学计算结果与最新的实验符合得很好,很好地解释了     

Stereodynamics of chemical reactions: quasi-classical,quantum and mixed quantum-classical theories

In this review, some benchmark works by Han and coworkers on the stereodynamics of typical chemical reactions, triatomic reactions H + D₂, Cl + H₂ and O + H₂ and polyatomic reaction Cl+CH₄/CD₄, are presented by using the quasi-classical, quantum and mixed quantum-classical methods. The product alignment and orientation in these A+BC model reactions are discussed in detail. We have also compared our theoretical results with experimental measurements and demonstrated that our theoretical results are in good agreement with the experimental results. Quasi-classical trajectory (QCT) method ignores some quantum effects like the tunneling effect and zero-point energy. The quantum method will be very time-consuming. Moreover, the mixed quantum-classical method can take into account some quantum effects and hence is expected to be applicable to large systems and widely used in chemical stereodynamics studies.