表面上方微粒及微粗糙度偏振光散射特性

为了区分由表面上方微粒和表面微粗糙度两种散射机理引起的散射光,利用偏振双向反射分布函数,并借助于由,■,■组成的正交右手基组表示了入射电场和散射电场。从理论上给出了两种不同散射机理在不同偏振状态下的双向反射分布函数与入射面外方位角之间的变化关系,并通过对这两种散射机理下的偏振双向反射分布函数的比较发现,利用p偏振入射产生的p偏振散射光(BRDFpp)可以将表面上方微粒和表面微粗糙度两种散射机理区分开来。     

Enhanced specular scattering by a single particle near a perfectly reflecting surface

The scattering of electromagnetic waves by a single particle situated randomly near a perfectly reflecting surface is considered in the dipole approximation with allowance for an infinite number of scatterings. It is shown that the rescattered waves lead to an increase in the effective scattering cross section and suppress the enhanced specular scattering of the p-polarized wave compared with the s-polarized wave. ISTOK, Fryazino, Moscow region; State Pedagogical Institute of Elabuga, Tatarstan, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 7, pp. 860–869, July, 1997.     

Normal-incidence scattering of surface plasmon polaritons by one-dimensional nanoindentations: a multimodal description

In this paper a theoretical study is made on the scattering of surface plasmon polaritons by a finite periodic array of one-dimensional rectangular grooves. Our approach is based on a multimodal expansion technique. We have found that the geometrical parameters of the array can be properly tuned to achieve optimal performance of the structure either as a Bragg reflector or as a converter of surface plasmon polaritons into light. Most importantly, such functionalities can be fully achieved with a relatively small number of grooves. PACS  73.20.Mf; 78.67.-n; 41.20.Jb     

Wave scattering functions and their application to multiple scattering problems

Scattering functions arise naturally in standard treatments of the effects of a material object or surface embedded in a uniform field. The most commonly used scattering function describes the far-field modulation imparted at large distances to a spherical wavefront eminating from the scatterer. The purpose of this is to develop the properties of the spectrum of scattered plane waves as an exact generalized scattering function. The linearity of the wave equations guarantees that such a representation exists; moreover, it is possible to derive the generalized scattering function from the far-field scattering function by analytic continuation. Although these properties are known, recent theoretical developments have motivated us to reexplore the interrelations among the far-field scattering function, the Green's function and various forms of the generalized scattering function as well as the symmetry properties of the generalized scattering function imposed by reciprocity. For multiple-scattering objects that can be separated by parallel planes, a system of difference equations is developed that fully accommodates the mutual interaction among the scatterers. The mutual interaction equations were developed earlier, but we show here that they can be transformed into the form that would be obtained by using the Foldy-Lax-Twersky formalism. This reinforces the equivalence between wave-space and configuration space formulations of the scattering problems.     

On the quantum mechanical description of scattering by a dissipative and diffusive scattering centre

A partial integro-differential equation is formulated for the Wigner transform of the quantum mechanical reduced density operator describing the time evolution of a “macroscopic” coordinate under the influence of coupling to a large number of “intrinsic” degrees of freedom. The equation contains integral operators which lead to energy dissipation and diffusion and reduces to a transport equation of the Fokker-Planck type if the form factors in the integrands are treated in appropriate (harmonic) approximations. The stationary solution of the partial integro-differential equation is obtained numerically for scattering by a conservative potential and by a dissipative and diffusive scattering centre in one spatial dimension.     

Fluctuation-induced electromagnetic interaction of a moving particle with a plane surface

The most general (nonrelativistic) formulas for the force of attraction to the surface and for the drag of a nonrelativistic atom moving parallel to it, as well as for the lateral and normal forces acting on a moving dipole molecule and on a charged particle (in the case of parallel and perpendicular motion), are derived for the first time in the framework of the fluctuational electromagnetic theory. The dependences of these forces on the velocity, temperature, separation, and dielectric properties of the atom and the surface are derived. The effect of the nondissipative resonance interaction between a moving neutral atom and the field of surface plasmons, as well as the possible emergence of a positive (accelerating) force acting on the atom (nanoprobe), is substantiated theoretically. The role of dynamic fluctuational forces and their possible experimental measurement when using the quartz microbalance technique and an atomic-force microscope (in the dynamic mode), as well as during deceleration of atomic beams in open nanotubes, are considered. The correctness of the obtained results is confirmed by their agreement with most of the available theoretical relations derived by other authors.     

New approach to a description of relativistic particle collisions

Relativistic particle collisions are described by the 2-form of a cross product of particle momentum 1-forms. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 42–45, December, 2008.     

New solid-state lasers and their application potentials

In recent years, Nd:YAG-lasers have found increasing interest in many fields of high-power applications that formerly had been the domain of CO₂-lasers. This was mainly due to several consequences of their wavelength, such as a higher absorptivity, lower sensitivity against laser-induced plasmas and, in particular, the use of flexible glass fibres for beam handling. Disadvantages like poor beam quality and low efficiency are being effectively reduced by recent developments of diode-pumped systems. Some promising concepts based on different pumping techniques and crystal geometries — rods, discs, fibres — will be discussed in view of attainable beam quality and means of power scaling. The second part of the paper will deal with investigations aimed at utilizing the beneficial properties of Nd:YAG-lasers, especially for welding. In particular, the advantages of the twin-focus technique are discussed in some detail with regard to power scaling, process improvements and flexibility increase. Based upon experience, the extension to a multi-focus technique is proposed by presenting experimental data obtained with lamp-pumped high-power lasers and results of numerical modelling. This evidence demonstrates the potential for industrial applications and provides an idea of what can be expected from the new generation of diode-pumped solid-state lasers with high beam quality.     

Atom scattering as a probe of the surface electron-phonon interaction at conducting surfaces

An atomic projectile colliding with a surface at kinetic energies in the thermal or hyperthermal range interacts with and is reflected by the electronic density well in front of the first layer of target atoms, and it is generally accepted that the repulsive interaction potential is proportional to the density of electrons extending outside the surface. This review develops a complete treatment of the elastic and inelastic scattering of atoms from a conducting surface in which the interaction with the electron density and its vibrations is treated using electron-phonon coupling theory. Starting from the basic principles of formal scattering theory, the elastic and inelastic scattering intensities are developed in a manner that identifies the small overlap region in the surface electron density where the projectile atom is repelled. The effective vibrational displacements of the electron gas, which lead to energy transfer through excitation of phonons, are directly related to the vibrational displacements of the atomic cores in the target crystal via electron-phonon coupling. The effective Debye-Waller factor for atom-surface scattering is developed and related to the mean square displacements of the atomic cores. The complex dependence of the Debye-Waller factor on momentum and energy of the projectile, including the effects of the attractive adsorption well in the interaction potential, are clearly defined. Applying the standard approximations of electron-phonon coupling theory for metals to the distorted wave Born approximation leads to expressions which relate the elastic and inelastic scattering intensities, as well as the Debye-Waller factor, to the well known electron-phonon coupling constant λ. This treatment reproduces the previously obtained result that the intensities for single phonon inelastic peaks in the scattered spectra are proportional to the mode specific mass correction components λ_Q,ν defined by the relationship λ = 〈λ_Q,ν〉. The intensities of elastic diffraction peaks are shown to be a weighted sum over the λ_Q,ν, and the Debye-Waller factor can also be expressed in terms of a similar weighted summation. In the simplest case the Debye-Waller exponent is shown to be proportional to λ and for simple metals, metal overlayers, and other kinds of conducting surfaces values of λ are extracted from available experimental data. This dependence of the elastic and inelastic scattering, and that of the Debye-Waller factor, on the electron-phonon coupling constant λ shows that measurements of elastic and inelastic spectra of atomic scattering are capable of revealing detailed information about the electron-phonon coupling mechanism in the surface electron density.     

High-energy scattering by a superposition of two power potentials

For a superposition of two power potentials the scattering amplitude and the total cross section are evaluated making use of the high-energy formula derived byBlankenbecler andGoldberger. The scattering amplitude is expressed by a finite sum of impact-parameter pole contributions in analogy to Regge poles in the angular momentum plane. It is shown that each pole contribution can be expressed in terms of known functions. Furthermore the large momentum transfer asymptotics of an impact parameter pole is investigated in detail.     

Simple surface interaction mechanism for magnetic substate excitation by inelastic scattering

A simple model is presented to explain the marked behaviour of the de-excitation γ-pattern in certain recent inelastic -particle scattering experiments from even nuclei (0⁺→2⁺ excitation). The model is a slight generalization of the well-known ring-locus model in that it is based on a ring locus of finite angular width. The dependence of the inelastic angular distribution and the reaction-plane γ-pattern on the parameters of the ring locus is discussed.     

New model interaction potential for the description of charged particle motion in matter

A new model interaction potential, in the form of a screened Coulomb potential, is proposed. Analytical expressions are derived for the stopping power of ions in elastic collisions. A program is written for Monte Carlo calculations of the ion ranges in an amorphous substance, taking inelastic losses into account in the continuous-slowing approximation and taking elastic collisions into account in the approximation of the new model interaction potential. The ranges of Cu and Rb ions in C and B targets are calculated. The results of the calculations are in good agreement with experiment.