Work function changes produced by chemisorption due to site heterogeneity

A quantum theory of elastic scattering of atoms from crystal surfaces is presented, based on a hard corrugated surface model. It is shown in detail how the rainbow effect arises and determines the diffraction probabilities, such a rainbow effect being the quantum analogon of McClure's classical rainbow. Further topics considered are the influence of a potential well and the reasons why diffraction hardly occurs from metal surfaces. The basis for a possible extension to inelastic scattering is sketched.     

Rainbow Interferometry with Wire Diffraction for Simultaneous Measurement of Droplet Temperature,Size and Velocity

A rainbow measurement technique is presented which measures simultaneously the size, temperature and velocity of individual droplets in a spray. The technique is based on rainbow interferometry in combination with diffraction by a wire placed in the spatial filter of the scattered-light detector. A photomultiplier detects the wire diffraction pattern superimposed on the rainbow interference pattern created by a droplet scattering laser light. The velocity is determined from the equivalent geometric wire shadow. The necessary sphericity validation is performed by comparing the Airy and the ripple droplet diameters, resulting from the respective interference structures. The temperature is recovered from the position of the wire diffraction pattern relative to the main rainbow maximum. The technique was applied to a water spray at ambient temperature. The results showed the importance of nonsphericity detection.     

Structure of ultrathin oxide layers on metal surfaces from grazing scattering of fast atoms

The structure of ultrathin oxide layers grown on metal substrates is investigated by grazing scattering of fast atoms from the film surface. We present three recent experimental techniques which allow us to study the structure of ordered oxide films on metal substrates in detail. (1) A new variant of a triangulation method with fast atoms based on the detection of emitted electrons, (2) rainbow scattering under axial surface channeling conditions, and (3) fast atom diffraction (FAD) for studies on the structure of oxide films. Our examples demonstrate the attractive features of grazing fast atom scattering as a powerful analytical tool in surface physics.     

On the diffraction of He by a Ni(110) surface

The diffraction of low-energy He atoms by a Ni(110) surface is studied using hard and soft wall models for the elastic scattering. The effects of thermal vibrations and inelastic processes on the He intensities are estimated. It is shown that the experimental spectra imply a corrugation height along the [001] direction that is maximally 0.12 au. A value of 0.30 au, calculated recently within a scheme that assumes the repulsive interaction to be proportional to the electron density of unperturbed Ni(110), leads to “double rainbow” diffraction patterns qualitatively different from those observed.     

Simple approach to refraction effects in atom-surface scattering

A simple method of calculating low energy atom-surface diffraction intensities is presented for the case in which the scattering is dominated by a single rainbow pattern. Good agreement is obtained when these calculations are compared with recent results for the scattering of He by a Pt(997) surface.     

Diffractive scattering in the Ericson model for the S matrix

The elastic scattering of spinless charged particles on nuclei is considered within the strong-absorption model proposed by Ericson for the S matrix in the angular-momentum representation. Our analytic method for summing partial-wave amplitudes, which is based on a generalization of the Abel-Plana formula, makes it possible to take into account the contributions from the possible singularities of the S matrix in the right-hand half-plane of the complex-valued variable l. The uniform asymptotic behavior obtained in the present study for the scattering amplitude offers a fresh view on the origin of the diffraction patterns in the angular distributions of elastically scattered heavy particles. Special attention is given to Coulomb-nuclear interference (in particular, to refraction phenomena) in the case of scattering into the classically allowed region (illuminated region) and the classically forbidden region (shadow region). In contrast to other analytic results, our solutions to the diffraction problem within the Ericson model do not give grounds whatsoever to draw profound analogies either with Fresnel diffraction in optics or with the phenomenon of rainbow scattering in classical mechanics.     

模压彩虹全息片的衍射效率及其测量

从理论上估算了模压彩虹全息片的最高衍射效率，与实测数据做了对照；说明了用透射观察法和反射观察法评价光刻胶母版衍射效果有很大差别，并分析了产生差别的原因；提出了测量模压彩虹全息片衍射效率的光学系统与测量方法，叙述了如何解决研制中的技术问题     

Dependence of the atomic structure and surface relief of platinum foils on the annealing and rolling conditions

The effect of cold rolling, polishing, and thermal annealing conditions on the atomic structure and surface geometry of platinum foils has been studied. The surface morphology has been analyzed using low-energy electron diffraction, atomic force microscopy, and scanning tunneling microscopy. The chemical composition of the surface has been evaluated by Auger electron spectroscopy. It has been demonstrated that a variation in the conditions used for the preparation of the samples makes it possible to produce surfaces with different degrees of perfection from atomically smooth to rippled, fractal, and diffraction-disordered surfaces.     

Description of elastic heavy-ion scattering within the Glauber-Sitenko approach

Analytic expressions for the amplitudes of elastic nucleus-nucleus scattering for various collision regimes are derived within the Glauber-Sitenko approach. The procedure used to do this employs an extended optical potential of the Woods-Saxon type and takes into account the deflection of trajectories by a strong Coulomb field. A comparison of the analytically calculated cross sections with numerical results and experimental data shows that the approach in question can be successfully used in the energy range from 10 to 100 MeV per nucleon. It is demonstrated that, for a preset potential, it is possible to find angular ranges dominated by specific patterns of scattering, such as classical or rainbow scattering and Fresnel or Fraunhofer diffraction.     

Modeling of neutral-atom scattering at the surface of a crystal for the case of grazing incidence

The features of the angular distributions of accelerated neutral atoms at grazing angles of incidence on the Al(001) surface are studied using the mathematical modeling method. The interaction of accelerated atoms with crystal-lattice atoms and the electronic properties and atomic structure of the Al(001) surface are calculated using the electron-density-functional method. The angular distributions of scattered atoms are modeled by taking into account their interaction with several atomic layers in the crystal lattice and atomic displacements during thermal oscillations. The influence of crystal surface-layer relaxation on rainbow scattering, i.e., the difference between the distances of planes on the surface and in the volume, is established. The possibilities of using the effect of rainbow scattering to study the structural features of a crystal surface are discussed.     

舞台用复制拼版彩虹镜的研制

对刻划光栅进行第一次浇注,经拼版第二次浇注制得电铸模板,再通过第三次特殊浇注进行批量复制,然后真空镀铝、保护而成舞台用复制硬质彩虹镜(反射型)。其特点是:衍射效率高于目前的全患彩虹镜,且价廉,适于推广使用。     

Defining the size and location of the slit in rainbow holography

A simple method is described for defining the size and location of the slit in a rainbow holography optical system in order to guarantee the optimal observation conditions of the reconstructed image. A brief explanation of the basic principles of rainbow holography is given and the projection of viewing slits and pseudoscopic, or orthoscopic, images is considered. An application of the method for afocal systems used in rainbow holography is presented.     

Some peculiarities for grazing incidence neutron diffraction from 3D near-surface nanostructures

Neutron diffraction at grazing incidence was simulated for the regularly ordered nanostructures on the surface and in the near-surface volume of a homogeneous matrix. Silicon was used as a matrix material and nanoparticles consisting of gold or nickel. This allowed obtaining a good scattering contrast between the matrix and nanoparticles and, as a result, high contrast diffraction patterns. It is shown that the modified kinematic approximation which takes into account the refraction of a neutron wave at the interface makes it possible to obtain a reasonable agreement with the available experimental data. In addition, it was demonstrated that in contrast to the traditional diffraction on point-like scattering centers, some unusual systematic absences could be observed due to the experiment geometric conditions and the finite geometric sizes of the nanoparticles. The results demonstrate that modified kinematic approximation can be successfully used to model non-specular neutron scattering from near-surface nanostructures and thereby facilitate the interpretation of experimental results.     

采用随机振动法抑制白光处理系统中的颗粒噪声

本文提出在白光信息处理中,可通过使滤波孔在傅里叶面彩虹状衍射谱附近做随机振动的方法,达到抑制光栅编码片的振幅型颗粒噪声.改善其输出信噪比的目的,并给出了相应的实验结果.     

Analysis of top and bottom surface structure in thin (001) Au films by high resolution transmission electron microscopy

Using computer-generated models of the (001) surface of Au a number of image computations were performed for high energy electron diffraction to match experimental transmission electron micrographs. With a multislice dynamical electron diffraction formalism it was possible to generate images from thin films which contained one roughened surface or both top and bottom surfaces roughened. Here, it will be demonstrated that the computer generated micrographs can be used to show both bulk lattice periodicities of 2.03 Å and the surface lattice of 2.86 Å and that these features are separable in real electron micrographs under favorable imaging conditions.     

A study on the Fresnel diffraction of 6He by means of different microscopic density distributions

The elastic scattering of the halo nucleus ⁶He from heavy targets such as ¹⁹⁷Au and ²⁰⁸Pb has been investigated in order to explain the Coulomb rainbow peak due to the Fresnel-type diffraction observed in the experimental data. In order to examine the role of nuclear potential to describe ⁶He + ¹⁹⁷Au and ⁶He + ²⁰⁸Pb systems, we have used the no-core shell model, few-body and Gaussian-shaped density distributions at various energies. The microscopic real parts of the complex nuclear potential have been obtained by using the double-folding model for each of the density distribution and the phenomenological imaginary potentials have been taken as the standard Woods-Saxon shape. We have observed that fewbody and Gaussian-shaped density distributions have given standard Fresnel-type diffraction results, a classical scattering pattern with Coulomb rainbow peak whereas the nuclear potential obtained by using the no-core shell-model density distribution has provided the reduction at Fresnel peak and has given more consistent results with the experimental data.     

投影彩虹全息术

本文提出一种新的彩虹全息图的记录方法——投影彩虹全息术.这种技术简化了彩虹全息图的记录过程,在某些方面克服了传统方法的限制,制作的投影彩虹全息图具有大景深、大视角和高分辨率的特点.文中介绍了投影彩虹全息图的记录和再现的原理,分析了它的基本性能,并讨论了一些成功和可能的应用.     

彩虹全息图和普通全息图的空间频率带宽

本文从菲涅耳-基尔霍夫衍射理论出发,从单狭缝彩虹全息图入手,具体分析了物、狭缝、参考光源及全息片在不同相对位置时全息图的空间频率带宽,得出了在各种情况下对彩虹全息图和普通全息图都普遍适用的统一公式,为在实际应用中压缩空间频率带宽及胶片选取、了解全息图对目标的空间频率损失提供理论上的根据。 关键词：     

The scattering of the field of a point source by an axisymmetric screen with a variable impedance

The method of continued boundary conditions is used to solve the acoustic diffraction problem for the case of a field generated by a point source and diffracted by an axisymmetric screen, with generalized impedance boundary conditions being satisfied at the screen surface. Two types of impedance boundary conditions are considered, which differ; at zero impedance one of them takes the form of the Dirichlet boundary condition, while the other the takes the form of the Neumann boundary condition. Both stationary and non-stationary diffraction problems are investigated. Numerical results are obtained for screens with parabolic and spherical shapes.