1,721,011 research outputs found
Light-scattering From Rough Surfaces - General Incidence Angle and Polarization
No full textThe amplitudes of the diffracted fields from a rough surface, for light of general polarization and incidence angle, are found by the classical method of Rayleigh and Fano. Explicit formulas are then obtained for the differential reflected intensity of P- and S-polarized light as well as for the decrease in reflection coefficient of S, P, and circularly polarized light due to the excitation of surface plasmons. The results are valid to first order in the surface roughness and are confirmed by additional calculations based on other perturbative methods, both classical and quantum mechanical. The discrepanies found in some cases with the recent results of Maradudin and Mills are analyzed and explained. © 1975 The American Physical Society
DEBYE-WALLER FACTOR IN ATOM SURFACE SCATTERING - ELASTIC AND INELASTIC CHANNELS
No full textExplicit expressions for the Debye-Waller factor for the elastic and one-phonon channels are presented to lowest order in the phonon displacement, using a hard wall model to represent the atom-surface interaction. The periodicity of the crystal is accounted for; thus we explicitly generalize to all elastic channels the reflectance result found by Garcia et al. within the plane-surface model, and we include the contribution of the umklapp processes to the inelastic channels. We show how for high incident energy of the atom all Debye-Waller factors reduce to the standard result
Atomic holography: does a polarized light beam improve the image?
No full textPerforming three measurements (holograms) on the same sample with the same beam but different polarization, spurious spots can be reduced and the holographic image appears to be better. The change of polarization requires nothing more than a rotation of the sample around the beam's direction. For the reconstruction of the image one applies the standard Fourier transform (FT) techniques on a combination of the holograms obtained. The resulting image is better than that obtained with an unpolarized beam
Light-scattering From Rough Surfaces
No full textWe have reconsidered the theory of the scattering and absorption of light incident on a medium of dielectric constant ε that is bounded by a rough surface, when the roughness can be treated as a perturbation of the perfectly flat surface. We obtain explicit formulas for perpendicularly incident light by several different methods, both classical and quantum mechanical and compare our results with those obtained by previous authors. In particular, we consider the case of a metal of dielectric constant 1-ωp2ω2 and discuss the excitation of surface plasmons. We show why the results obtained by Elson and Ritchie by a quantum-mechanical method based on a coordinate transformation do not agree in some cases with the results of the classical theory and with the results of a straightforward quantum treatment that is applicable only to normal incidence. We introduce a new coordinate transformation that does not suffer from the limitations of that used by Elson and Ritchie and thereby allows their general method to be applied, with correct results, for general polarization and incidence angle
OPTICAL-PROPERTIES OF ROUGH SURFACES - GENERAL THEORY AND SMALL ROUGHNESS LIMIT
No full textThe diffraction of electromagnetic waves from the rough surface of a material of finite permittivity is examined for the case where the wavelength of the incident radiation is comparable to the dimensions of the surface roughness. Two methods of calculation studied are the Rayleigh method and the extinction-theorem integral-equation method. The latter is shown to have a unique exact solution. This property is, in turn, used to show how the Rayleigh method can be modified to give convergent results. The extinction theorem is also used to reduce the Rayleigh equations to a simpler form. These reduced equations, which are extremely convenient to use in the case of small roughness, are applied in this case to find perturbative expressions for the reflected field and for the surface-plasmon dispersion relatio
Theory of Three Wave Mixing of Volume-EM, Surface Acoustic Waves and Surface Polaritons
No full textThis paper deals with the theory of light scattering from a thin metallic film where corrugations exists at both surfaces. The scattering cross section for backward and forward diffraction is computed by solving perturbatively the Maxwell equations to first order in the corrugation amplitude. A comparison is made with the experimental results presented in the preceding paper where the corrugations are of dynamic character (surface elastic waves). The different behaviour of the backward and forward cross sections is explained in terms of interference effects
A Method for Determining Surface States by Complex Extension of Tight-Binding
No full textA method is developed for calculating surface states and the composition of the surface wave functions. The formulation is made for tight-binding Hamiltonians. The present scheme is based on the extension of the bulk bands in the complexk-plane. The surface is viewed as a boundary condition of the Schrödinger difference equation of the infinite crystal. At points of high symmetry of the two-dimensional Brillouin zone, this approach gives analytic expressions for surface states and allows one to determine the composition of real and evanescent waves which make up the wave function of the semi-infinite crystal. It provides an attractive computational method that can also be used to study reconstructed surfaces
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
GAS SURFACE INTERACTIONS AND PHYSISORPTION - PROCEEDINGS OF THE UNITED-STATES ITALY SEMINAR ON GAS SURFACE INTERACTIONS AND PHYSISORPTION, CHARLOTTESVILLE, VA 4-7 JUNE 1984 - PREFACE
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