X射线衍射的发现

简单介绍了埃瓦尔德(Ewald P P)、劳厄(von Laue M)和布拉格父子(Bragg W H及Bragg W L)在1912年发现X射线衍射方面的贡献．1911年埃瓦尔德在索末菲的指导下在慕尼黑大学从事博士论文研究，劳厄在与他的讨论中了解到晶格的平移周期与X射线的波长属于同一量级，因此想到在二维光栅的两个衍射方程组中再加一个类似的方程，就可以描述X射线在三维晶体中的衍射．在此假设的指导下，Friedrieh W和Knipping P在1912年4月开始用CuSO4后来用闪锌矿(立方ZnS)进行实验，很快就得到X射线衍射的证据．这不但证明了X射线的波动性，还确定了晶体的三维周期性．老布拉格在1912年夏得知这个消息，与他儿子小布拉格一道尝试用X射线的粒子性解释它，并由小布拉格在剑桥大学重复这个实验．根据衍射斑点的椭圆形状和从Pope与Below那里学到的晶格理论(由此得知ZnS具有面心立方晶格)，小布拉格将X射线在晶体中的衍射看作是X射线从一些晶格平面的反射，从而推导出著名的布拉格方程．布拉格父子开拓了X射线晶体结构分析这门新兴学科，从简单的无机化合物和矿物，逐渐发展到有机化合物和生物大分子．劳厄和布拉格父子分别强调慕尼黑和剑桥的优良科学环境对发现X射线衍射的重要性．鉴于埃瓦尔德在发现X射线衍射的作用及他后来在倒易格子及动力学衍射理论方面的贡献，不少晶体学家认为他也应获得诺贝尔物理奖．     

X射线衍射进展简介

100年前,劳厄等证明X射线对硫酸铜晶体具有衍射能力,揭开了X射线衍射分析晶体结构的序幕.100年的发展,X射线衍射已经成为自然科学乃至医学、考古、历史学等众多学科发展的必备技术.文章介绍了X射线衍射现象的发现历史,X射线运动学和动力学理论的发展概况,并举例说明了X射线衍射在粉末多晶体、单晶体和人工功能晶体以及人工薄膜材料中的具体应用情况,最后简要展望了X射线衍射技术的发展前景.     

纪念劳厄发现晶体X射线衍射90周年编者的话

20 0 2年和 2 0 0 3年分别是劳厄 (vonLaueMax)发现X射线晶体衍射和布拉格 (BaggWL)建立布拉格方程90周年 .劳厄和布拉格的发现是 2 0世纪物理学意义深远的大事 .1895年伦琴发现X射线后 ,关于X射线的本质是不清楚的 ,一种观点认为是穿透性很强的中性微粒 (粒子学说 ) ,另一种观点认为是波长较短的电磁波 (波动学说 ) .应该说 ,劳厄的发现 ,除了他本人具备坚实的物理基础 ,敏锐的洞察能力以及当时劳厄所在的慕尼黑大学高水平的学术研究环境等因素外 ,还直接得益于与埃瓦尔德 (EwaldPP)的一次谈话 .通过与埃瓦尔德的讨论 ,劳厄酝酿出一个…     

利用改进型衍射理论对直边衍射效应的解释

利用改进型衍射理论MTPO（Modified Theory of Physics Optics）对直边衍射现象做出了解释．用数值模拟方法得出了直边衍射场强随衍射角度的变化曲线，并与广泛采用的菲涅耳近似衍射方法结果进行比较，发现在很大的角度空间上，二者所得出的衍射场强与精确解吻合较好．但在入射波的几何传播方向上，即边缘上的衍射场强分布，MTPO方法则具有更高的准确度．     

多层膜劳厄透镜对8keV X射线的聚焦性能模拟研究

基于多层膜技术的劳厄(Laue)透镜能实现硬X射线纳米级聚焦,在X射线微纳分析领域具有重要的应用前景.基于衍射动力学理论,分析了X射线在多层膜劳厄透镜中的传播,计算了不同结构的多层膜劳厄透镜对8 keVX射线的聚焦性能.结果表明,最外层厚度为5 nm的倾斜多层膜劳厄透镜可获得5.7 nm的聚焦光斑和26%的平均衍射效率...     

劳厄对晶体衍射的发现

介绍了劳厄提出晶体衍射思想的科学背景及当时的实验过程,并探讨在劳厄发现晶体衍射的过程中其科学思想的形成及X射线晶体衍射的发现带给我们的启示及影响．     

晶体X射线衍射的发现及其深远影响

1912年4月,弗里德里希、克里平和劳厄成功地观察到X射线透过硫酸铜晶体后的衍射斑点!随后劳厄推导出描述晶体衍射的著名劳厄方程.由于晶体X射线衍射的发现,劳厄于1914年荣获诺贝尔物理学奖.1912年10月,W.L.布拉格通过X射线透射ZnS晶体实验,推导出了著名的布拉格方程.1915年布拉格父子荣获诺贝尔物理学奖.晶体X射线衍射的发现对自然科学的影响是深远的.2012年是劳厄发现晶体X射线衍射100年,文章回忆了这段光辉的历史及其对科学技术所产生的深远影响,以怀念科学先驱们对科学技术的贡献,弘扬他们对科学研究的认真严谨的科学态度、勇于创新的科学精神和谦逊无私的品德.     

声学劳厄衍射和描述劳厄衍射斑的晶格模型

波在晶格中的衍射是波动学和固体物理学领域中的重要课题。本文第一部分描述了一个与在晶格中X射线的劳厄衍射相似的声学实验;第二部分主要讨论描述立方晶体中劳厄衍射斑的晶格模型。     

从劳厄发现晶体X射线衍射谈起

文章从劳厄发现晶体X射线衍射的前因后果谈起．劳厄的这个发现产生了两个新学科，即X射线谱学和X射线晶体学．文中还回顾了布拉格父子对这两个新学科所作的重大贡献，并阐述了X射线晶体学的深远影响．     

晶体X射线劳厄衍射分束特性研究

本文基于X射线衍射动力学分析了劳厄晶体的分束特性,模拟了晶体吸收和入射光角发散对于透射光和衍射光摇摆曲线的影响,定量给出晶体衍射面内角调节范围和晶体加工厚度对于劳厄衍射分束比的调制.在实验中,采用分析晶体和分束晶体的消色散配置限制入射光角发散的影响,实现300μm厚Si(220)晶体面内角调节劳厄衍射分束的精确测量,并得到300μm, 400μm和500μm厚度Si晶体分束比的调节范围,实现了透射光和衍射光强度的定量调制.     

Method of categorical extension of Cayley-Klein groups

The method of categorical extension of the Cayley-Klein groups is developed. The method uses the Cayley-Klein spaces as objects of the Cayley-Klein category endowed with all possible linear relations or bilinear forms as morphisms. Presented at the International Colloquium “Integrable Systems and Quantum Symmetries”, Prague, 16–18 June 2005.     

Center-symmetric dimensional reduction of hot Yang-Mills theory

It is expected that incorporating the center symmetry in the conventional dimensionally reduced effective theory for high-temperature SU(N_c) Yang-Mills theory, EQCD, will considerably extend its applicability towards the deconfinement transition. The construction of such a center-symmetric effective theory for the case of two colors is reviewed and lattice simulation results are presented. The simulations demonstrate that unlike EQCD, the new center-symmetric theory undergoes a second order confining phase transition in complete analogy with the full theory.     

The propagation of infinitesimal disturbances in an ultrarelativistic gas according to the method of elementary solutions

It has recently been shown that a linearized relativistic BGK model can be reduced, in the ultrarelativistic limit, to a system of three uncoupled transport equations for thermal, sound, and shear waves. The equation describing the propagation of thermal waves is the well-known one-speed neutron transport with isotropic scattering in the conservative case. In this paper the solution of the half-space problem for the equation describing the propagation of shear and sound waves is given according to Case's elementary solutions method.     

Matrix string theory

Via compactification on a circle, the matrix mode] of M-theory proposed by Banks et a]. suggests a concrete identification between the large N limit of two-dimensional N = 8 supersymmetric Yang-Mills theory and type IIA string theory. In this paper we collect evidence that supports this identification. We explicitly identify the perturbative string states and their interactions, and describe the appearance of D-particle and D-membrane states.     

Review of chiral perturbation theory

A review of chiral perturbation theory and recent developments on the comparison of its predictions with experiment is presented. Some interesting topics with scope for further elaboration are touched upon.     

The Symmetrical Foundation of Measure,Probability, and Quantum Theories

Quantification starts with sum and product rules that express combination and partition. These rules rest on elementary symmetries that have wide applicability, which explains why arithmetical adding up and splitting into proportions are ubiquitous. Specifically, measure theory formalizes addition, and probability theory formalizes inference in terms of proportions. Quantum theory rests on the same simple symmetries, but is formalized in two dimensions, not just one, in order to track an object through its binary interactions with other objects. The symmetries still require sum and product rules (here known as the Feynman rules), but they apply to complex numbers instead of real scalars, with observable probabilities being modulus squared (known as the Born rule). The standard quantum formalism follows. There is no mystery or weirdness, just ordinary probabilistic inference.     

A discussion on the origin of quantum probabilities

We study the origin of quantum probabilities as arising from non-Boolean propositional-operational structures. We apply the method developed by Cox to non distributive lattices and develop an alternative formulation of non-Kolmogorovian probability measures for quantum mechanics. By generalizing the method presented in previous works, we outline a general framework for the deduction of probabilities in general propositional structures represented by lattices (including the non-distributive case).     

Fluorescence versus laser effect: Towards a unified theory

A single evolution equation is established to treat the mechanisms of fluorescence and the laser effect, using a mixed representation, classical for the electromagnetic field and quantum for the dipoles. The model approach takes advantage of the principle of conservation of energy for the system of electromagnetic field and dynamic dipole. A resulting nonlinear differential equation is derived and is shown to sustain two fixed points associated with fluorescence and laser emission. The existence of a pumping threshold is confirmed for the laser effect. In particular the pumping rate determines whether light will be emitted by fluorescence or by the laser effect, and there is no pumping that engenders fluorescence and laser emission simultaneously. The initial physical conditions, chosen to integrate the evolution equation in time, assume a nonvanishing electric polarization of the emitting dipole rather than a nonvanishing electromagnetic field. The distribution function accounting for the thermal fluctuations of the random initial polarization is also calculated.