Scattering of He atoms from rough surfaces

Three diverse rough surfaces have been studied using inelastic He scattering. The first is an ion bombarded Ag(110) surface where a broadened specular peak remains visible but scattering remains entirely elastic as viewed by the incoherent component. The second is a cleaved Te(10 ) surface composed of helical chains where the roughness originates from thermal oscillations and scattering is almost entirely inelastic. Thirdly, a glass (7740) disc is shown to be physically rough but the surface is sufficiently rigid to yield largely elastic incoherent scattering.     

Scattering of waves from nonlinear media with rough surfaces

Abstract

Reflection and scattering of waves from plane and statistically rough interfaces between nonlinear media are studied theoretically. New hysteresis-type dependences of the reflection and transmission coefficients on the amplitude of the incident wave and on the angle of incidence are predicted. Scattering diagrams for diffusely reflected and transmitted fields are calculated. It is found that when the dielectric constant is a steep function of the incident amplitude, nonlinearity suppresses the Bragg resonant scattering mechanism. Smooth roughness of the boundary is shown to enhance the penetration of evanescent waves into nonlinear media.     

Scattering on rough surfaces with alpha-stable non-Gaussian height distributions

We study the electromagnetic scattering problem on a random rough surface when the height distribution of the profile belongs to the family of alpha-stable laws. This allows us to model peaks of very large amplitude that are not accounted for by the classical Gaussian scheme. For such probability distributions with infinite variance the usual roughness parameters such as the RMS height, the correlation length or the correlation function are irrelevant. We show, however, that these notions can be extended to the alpha-stable case and introduce a set of adapted roughness parameters that coincide with the classical quantities in the Gaussian case. Then we study the scattering problem on a stationary alpha-stable surface and compute the scattering coefficient under the first-order Kirchhoff and small-slope approximations. An analytical formula is given in the high-frequency limit, which generalizes the well known geometrical optics approximation. Some numerical results are given and discussed.     

Transition radiation from rough surfaces

The light emission of normally incident 77 keV electrons on silver surfaces of different roughness has been investigated. The roughness was quantitatively determined by measuring the scattered light of a normally incident laser beam. In addition to the transition radiation, which is expected for smooth surfaces, light emission of surface plasmons via surface roughness occurs. The shape and the intensity of the spectral distribution of this emission show a characteristic change with the surface roughness.     

Scattering by random rough surfaces: Study of direct and inverse problem

In order to study the problems of scattering by rough metallic surfaces, we have used Maxwell’s equations in covariant form within the framework of a non-orthogonal coordinates system adapted to the geometry of the problem. Electromagnetic fields are written in Fourier’s integral form. The solution is found by using a perturbation method applied to the smooth surface problem; this is fully justified when the defects are of small magnitude.For the direct problem, the mean value of diffraction intensity is obtained for random rough surfaces of finite conductivity by computer simulation.In the case of the inverse problem, the reconstruction of the profile of the metal surface from values of the diffraction intensity, obtained by simulation, is found using an iterative algorithm.     

Scattering by rough surfaces in a conical configuration: experimental Mueller matrix

A simple method for measuring the Mueller matrix associated with rough surfaces in a conical configuration is presented. I present result of experimental measurements of the Mueller matrix for the angular distribution of the light scattered by a one-dimensional gold-coated randomly rough surface in a conical configuration. Effects related to the phenomenon of enhanced backscattering are reported.     

Scattering from very rough metallic and dielectric surfaces: a theory based on the modified Kirchhoff approximation

This paper presents a theory of scattering from very rough metallic and dielectric surfaces using the first- and second-order Kirchhoff approximations (KA) modified with the angular and propagation shadowing. The shadowing functions limit the single and double scattered waves which are illuminated and not shadowed by the surface. The theoretical results are compared with the Monte Carlo simulations showing the range of validity of the theory. The theory is applicable to the range where the RMS height is close to a wavelength and the RMS slope is close to unity, and the second medium is lossy. The second-order scattering includes two waves travelling in opposite directions on the surface, giving a physical explanation of the enhanced backscattering.     

Scattering of scalar fields by rough surfaces. Accounting for multiple scattered waves

Physical Engineering Institute, Moscow. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 34, No. 5, pp. 565–574, May, 1991.     

Scattering of molecular beams from surfaces

Molecular beam scattering from surfaces offers a unique method for studying elementary gas-solid collisions. Recent technological advances have made it possible to study elastic and inelastic scattering from clean surfaces characterized by LEED and Auger spectroscopy. These experiments have provided information on surface structures, with and without adsorbed gases, on the gas-surface interaction potential, and on inelastic collisions involving phonon annihilation and creation. These recent measurements are reviewed and discussed in terms of the latest theoretical work.     

White light scattering from non-Gaussian rough surfaces

Optics and Spectroscopy - A method is proposed for calculating the spectral correlation function of light intensity scattered from non-Gaussian rough surfaces. The correlation function of a...     

弹性波在固体自由粗糙平界面上的散射

利用散射幅度矩阵的概念来处理弹性波在粗糙界面弹性介质中的散射问题。利用微扰近似解边界方程,对散射幅度进行求解,得到了散射幅度的0阶、1阶和2阶解。同时分析了粗糙起伏高度符合高斯分布时,散射幅度的数学期望值和方差,它们分别代表平均场和声场在偏离镜面方向的起伏。最后进行了实验。     

Scattering of electromagnetic waves from two-dimensional perfectly conducting random rough surfaces - study with the curvilinear coordinate method

We present a method giving the bi-static scattering coefficient of two-dimensional (2-D) perfectly conducting random rough surface illuminated by a plane wave. The theory is based on Maxwell's equations written in a nonorthogonal coordinate system. This method leads to an eigenvalue system. The scattered field is expanded as a linear combination of eigensolutions satisfying the outgoing wave condition. The boundary conditions allow the scattering amplitudes to be determined. The Monte Carlo technique is applied and the bi-static scattering coefficient is estimated by averaging the scattering amplitudes over several realizations. The random surface is represented by a Gaussian stochastic process. Results are compared to published numerical and experimental data. Comparisons are conclusive.     

Scattering from a rough layer of a random medium

This paper deals with scattering from a random-medium layer with rough boundaries. The fluctuations of the surface heights and medium permittivity are assumed to be small and smooth. All random quantities are assumed to be stationary and independent of each other. After the introduction of approximate boundary conditions, the system of partial differential equations is transformed into an integral equation where the fluctuations of the problem are represented as a zero-mean random operator. Employing smoothing, integral equations for the coherent fields are obtained. Use of the Helmholtz operator leads to solution for the coherent propagation constant while the boundary operators lead to coherent Fresnel coefficients. The characteristics of the results are illustrated by considering several examples.     

Scattering of linear molecules from solid surfaces

Scattering of linear molecules, which are internally deactivated initially, from solid surfaces is investigated classical mechanically. The solid is modeled with a three-dimensional isotropic Debye solid whose surface is essentially flat but thermally roughened by lattice vibration, and the molecule is described as a rigid body, which interacts with the solid via an exponential potential wall and a stationary attractive potential well. A variation in the interaction energy due to thermal roughening of the surface and due to nonsphericity of the molecule being regarded as perturbations on the system, a second order perturbation theory is developed to construct a Gaussian velocity distribution function of molecules scattered off the exponential wall and still moving inside the potential well. Among the molecules in the distribution, those with sufficient energy to escape from the potential well are regarded as being scattered into the free space. This model shows that the major differences between the scattering of monatomic molecules and that of linear ones result from less normal momentum transfer to the linear molecules than to the monatomic ones.