Power Reflection,Transmission and Absorption Coefficients for a Moving Plasma Slab

Expressions for power reflection (R), transmission (T) and absorption (A) coefficients for p-polarized wave for a warm, collisional, magnetized and moving plasma slab (with sharp boundaries and thickness d₀) are investigated. The effects of plasma slab velocity (β=v/c), electron density (ωp/ω)² and plasma temperature (K_BT) on reflection (R), transmission (T) and absorption (A) coefficients are discussed numerically. It is observed that for the value β=?0.6, reflection coefficient (R) becomes more than unity, whereas absorption coefficient (A) becomes quite negligible while transmission coefficient (T) shows oscillatory behaviour. The variation with plasma frequency (ω_p/ω)² shows that at lower plasma frequency (ω_p/ω)²=0.2 transmission (T) and absorption (A) coefficients are minimum while reflection coefficient (R) is maximum.     

Solutions to the reflection equation and integrable systems for N = 2 SQCD with classical groups

Integrable systems underlying the Seiberg-Witten solutions for the N = 2 SQCD with gauge groups SO(n) and Sp(n) are proposed. They are described by the inhomogeneous XXX spin chain with specific boundary conditions given by reflection matrices. We attribute reflection matrices to orientifold planes in the brane construction and briefly discuss its possible deformations.     

Resonant diffraction in stishovite near the <Emphasis Type="Italic">K</Emphasis> absorption edge of silicon

The X-ray resonant diffraction in a stishovite crystal near the K absorption edge of silicon (E _K = 1839 eV) is studied theoretically. For such a long wavelength, the only possible Bragg reflection is the 100 reflection, which is forbidden by the space group of the crystal. It can be excited solely due to anisotropy of the X-ray scattering amplitude. The crystal symmetry is used to determine the polarization and azimuthal dependence of the reflection intensity. Since this reflection is single, it can be detected upon diffraction from a powder, which substantially widens the possibilities of investigations. The numerical calculations of the energy dependences of the forbidden reflection intensity and the absorption coefficient demonstrate that the dipole-quadrupole, quadrupole-quadrupole, and dipole-octupole contributions to the resonant diffraction and absorption are small and that the dipole-dipole contribution is the most important one.     

Reflection of cold atoms from an array of current-carrying wires

We report the realization of a new type of magnetostatic mirror for slowly moving atoms which comprises a planar array of parallel wires alternately carrying electric current in opposite directions. One of the features of this atomic mirror is that the magnetic field may be readily varied, switched or modulated by altering the current in the wires. Reflection signals close to 100% at a pulsed current of 3 A are demonstrated for a beam of free-falling laser-cooled cesium atoms at normal incidence. The current dependence of the reflection signals exhibits structure which is associated with the sequential onset of reflection of cesium 6² S _1/2 , F=4 atoms in the m=+4, +3, +2 and +1 magnetic states. Measurements of the spatial distribution of the reflected atoms indicate the reflection is predominantly specular at currents of 3 A. Received: 31 August 1998 / Accepted: 6 October 1998     

Bragg reflection waveguide: Anti-mirror reflection and light slowdown

The effect of the light group velocity reduction in dielectric Bragg reflection waveguide structures (SiO₂/TiO₂) in the vicinity of the cutoff frequency is studied experimentally. The effect of anti-mirror reflection specific to Bragg reflection waveguides is described and employed to detect slow light. Experiments were performed using Ti:sapphire laser pulses ∼100 fs in length. The group index n _g ∼ 30 with a fractional pulse delay (normalized to the pulse width) of ∼10 is demonstrated. The problems and prospects of the implementation of slow-light devices based on Bragg reflection waveguide structures are discussed.     

Cavitation and the tensile strength of liquids under dynamic stressing

This paper discusses the differences between the results of various measurements of the effective tensile strength (F _c ) of liquids in experiments involving a pulse of tension (‘negative pressure’) created by the reflection of a pressure pulse at a boundary. Using a modified ‘bullet-piston’ (B-P) pulse reflection apparatus, measurements presented herein show that degassed, deionized water is capable of sustaining tensions an order of magnitude greater than previously reported in B-P work. Results are also reported for a series of Newtonian silicone oils which show a similar dependence of F _c on the shear viscosity (μ) as a previous study though the absolute values of F _c are greater.     

Surface scattering of electrons on copper whiskers and its influence on the electrical resistivity at 4.2 K

The effect of specimen size on the electrical resistivity at 4.2 K of copper whiskers having transverse dimensions in the order of the electron mean-free path was measured. The experimental data are interpreted by means of a modified Nordheim formula adapted to the exact theory of Dingle. Assuming for copper the value of the productQ ₀·λ obtained from the free electron model a specularity parameterp for the surface scattering of conduction electrons is deduced from the diameter dependence of the sample resistivity. Values ofp=0.45 (up to 0.66 in an individual case) andp=0.18 are calculated exhibiting that significant specular reflection is present. Differences in the amount of specular reflection appear to arise from differences in the microscopically observed surface conditions of the whiskers.     

Numerically stable solution of coupled channel equations: The local reflection matrix

The second order linear Schrödinger equation is transformed to a first order nonlinear differential equation for a quantityp=(iq ^–1 –)/(iq ^–1 +). In a coupled channel problem all quantities occurring in this equation includingq (the WKB wave number) are matrices andp may be calledlocal reflection matrix. This quantity is closely related to the logarithmic derivative of the Schrödinger function but has no singularities in the classically allowed region. In the asymptotic region where the potential is constant the local reflection matrix approaches the physical reflection matrix. In a pure reflection problem (with an infinite potential on one side) this is the fullS-matrix, in a transmission problem (with an activation barrier of finite height) unitarity of theS-matrix can be used to determine most quantities of physical interest fromp. While standard logarithmic derivative methods can become instable for transmission problems the solution with the local reflection matrix is completely stable both for reflection and transmission problem.     

Characterization of a template process for conducting cluster-assembled wires

Bismuth and antimony clusters have been deposited onto spin coated PMMA layers patterned by electron-beam exposure. The probability of reflection or adhesion of the clusters from the PMMA depended on its surface roughness, determined by the electron-beam exposure dose. The Bi and Sb clusters exhibited a significantly higher probability of reflection from unexposed PMMA than from Si₃N₄ (grown by plasma enhanced chemical vapor deposition) despite the approximately equal surface roughness of these layers. By exploiting this difference in adhesion/reflection, a cluster-assembled wire was grown between four-point planar electrodes. Four-probe electrical measurements yielded linear current-voltage (I(V)) characteristics whilst non-linear I(V) characteristics were obtained from two-probe measurements. An established model provided good agreement with two-probe conductance-voltage and resistance-temperature data. Tunneling barriers between the cluster wire and the planar electrodes are believed to have caused the non-linear two-point I(V) characteristics.     

Polarization stokes polarimetry of the amplitude and phase characteristics of surface plasmon polariton resonance

The amplitude and phase characteristics of internal reflection of gold nanofilms have been investigated using polarization modulation of electromagnetic radiation in the Kretschmann geometry. The component Q (the difference between the reflection coefficients R _s ² and R _p ² for the s and p polarizations, respectively) and the component V of the Stokes vector (the difference between the phases of the orthogonal components of linearly polarized radiation) of light reflected from a half-cylinder of the total internal reflection with gold films of different thicknesses on its flat surface have been measured as a function of the angle of incidence of light in the wavelength range 500–1000 nm. It has been demonstrated that, in the range of parameters corresponding to the manifestation of the plasmon polariton resonance (the angle of incidence of light, the wavelength, the metal film thickness), the dispersions of the amplitude and phase characteristics are in quantitative and qualitative agreement with the model concepts of a classical oscillator.     

Amplitudes of two-channel scattering by a two-dimensional potential barrier with a constant height

The immersing method is used to solve the two-channel scattering problem in the case of concrete potential. In particular, we consider the particle scattering by a two-dimensional barrier which is constant in the scattering direction and is arbitrary in the transverse direction. For this case the scattering amplitudes t ₁, t ₂, r ₁, and r ₂ are determined. Expressions for the transmission and reflection amplitudes are obtained for the case of δ-potential. The behavior of the scattering amplitudes in the limit k ₂ → 0 is studied. It is also shown that the ratio of products of transmission and reflection amplitudes for two channels does not depend on the coordinate of the middle of coordinate.     

Interferential polychromatic filters

The reflection properties of one-dimensional generalized Cantor-like multilayer (GCLM) are investigated numerically in the visible range. Strong correlation between the stack geometry and the properties of the optical reflection spectra is found, namely spectral scalability and sequential splitting. The construction of multilayer systems according to the definite Cantor distribution brings improvements to the reflection properties. In particular, the widening of the band gap and the thin peak appearance in the reflection spectra whose number increases with the division number in the (GCLM). Optical properties of (GCLM) inserted between two periodic stacks are numerically investigated. We chose SiO₂(L) and TiO₂ (H) as two elementary layers. The study configuration is H(LH)⁵[GCLM]^PH(LH)⁵ which forms an effective interferential filter in the visible spectral range. We show that the number of resonator peaks is dependent on the repetition of the number P of the (GCLM). The best performances are obtained in particular for the symmetrical configurations of the (GCLM) and especially for P an odd number.Received: 10 July 2003, Published online: 30 January 2004PACS: 61.44.Br Quasicrystals - 42.70.Qs Photonic bandgap materials - 42.79.Ci Filters, zone plates, and polarizers     

Intramolecular enantiomerism as revealed from Raman optical activity spectrum

An algorithm is employed to retrieve the differential bond polarizabilities (DBP) of the C‐C bonds from the Raman optical activity spectrum of (‐)β‐pinene. (‐)β‐pinene possesses two stereo centers (chiral centers) and a local mirror reflection that interchanges the S type part and R type part in one molecular. It is demonstrated that this local mirror reflection could induce an approximate (or symmetry breaking) mirror reflection that reverses the signs of the DBP of the pair bond coordinates that are related to each other by the mirror reflection.This can be called intramolecular enantiomerism (IE). More cases of IE are discussed by the analysis of (‐)α‐pinene, (R)‐(+)‐4‐isopropyl‐1‐methylcyclohexene and (R)‐(+)‐3‐methylcyclohexanone together with previously studied limonene case. Copyright © 2015 John Wiley & Sons, Ltd.     

Observation of channeling and volume reflection in bent crystals for high-energy negative particles

Deflection due to planar channeling and volume reflection in short bent silicon crystals was observed for the first time for 150 GeV/c negative particles, π⁻ mesons, at one of the secondary beams of the CERN SPS. The deflection efficiency was about 30% for channeling and higher than 80% for volume reflection. Volume reflection occurs, in spite of the attractive character of the forces acting between the particles and the crystal planes, in a wide angular range of the crystal orientations determined by the crystal bend angle.     

Baryon asymmetry at the weak phase transition in the presence of arbitrary CP violation

The interactions of fermions with the domain-wall bubbles produced during a first-order phase transition are considered. An exact solution of the Dirac equation’s fermion propagation is obtained for a wall profile incorporating a position-dependent CP-violating phase. The reflection coefficients through the wall are computed for particles and antiparticles. The asymmetry in the reflection coefficients is especially high (a resonance effect) when the energy and mass of the incident particles are E/m=Δθ/2, where Δθ is the phase variation across the wall width. We compute the chiral-charge flux through the wall surface and the corresponding baryon asymmetry of the Universe. It agrees in sign and magnitude with the observed baryonic excess ϱB/s ≈ 10^-10 for a larnge of parameters and CP violation. As a function of Δθ, the ratio ϱb/s reaches a maximum for large values of Δθ (m ≈ m _top). The text was submitted by the author in English.     

Brewster angle for anisotropic materials from the extinction theorem

We explore the physical origin of the Brewster angle in the external and internal reflections associated with an anisotropic material. We obtain the expressions of the reflected fields and the existence condition of the Brewster angle by using the extinction theorem. It is found that the Brewster angle will occur if the total contribution of the material’s electric and magnetic dipoles to the reflected field becomes zero. In internal reflection, the requirements on the material parameters ε and μ for the Brewster angle are the same as those in external reflection, and the Brewster angle is just the refraction angle in external reflection at the incidence of the external Brewster angle. The results of the present paper are applicable to dielectric and magnetic materials, including metamaterials. PACS 73.20.Mf; 78.20.Ci; 41.20.Jb; 42.25.Fx     

半导体远红外反射镜中反射率和相位研究

以GaAs材料为例，研究了半导体远红外反射镜中的反射率和相位.通过拟合不同掺杂浓度下样品的远红外反射谱，得到了自由载流子的弛豫时间随掺杂浓度变化的经验公式，并把该规律应用到数值计算中.详细讨论了反射镜的结构和材料参数对反射率R和相位φ的影响.根据腔体内吸收率最高的判据得到了最优的反射镜的参数，并计算了这种优化后的反射镜的波长选择特性.最后，通过远红外反射光谱的测量，从实验上验证了这种反射镜的实际效果. 所得结论为半导体远红外器件中的反射镜设计提供了参考. 关键词： 远红外反射镜 反射率 相位     

Spectroscopy of phonon and vibronic states of YbAl3(BO3)4 single crystal

The polarized Raman and reflection spectra of a single crystal YbAl₃(BO₃)₄ at room temperature were studied. Raman active vibrational modes A ₁, E _TO, and E _LO are identified. In the Raman spectrum, we detected an intense line at a frequency of 1018 cm⁻¹, which refers to internal vibrations of the BO₃ group and is known to be promising for use in amplifiers based on stimulated Raman scattering. From the simulation of reflection spectra by the method of dispersion analysis the frequencies of A ₂ vibrational modes were determined. Intense bands observed in the low-temperature transmission spectra in the range of f-f transitions in the Yb³⁺ ion are attributed to electron-phonon transitions. The Raman lines are compared with electron-phonon lines in the transmission spectrum.     

Reflection,transmission, and conversion of acoustic surface waves incident normally onto a quartz wedge with planeY,X-cut

The reflection, transmission, and conversion of an acoustic surface wave (SAW), incident normally onto the edge of a quartz wedge withY,X-cut planes are investigated as functions of the wedge angle. A maximum amplitude reflection coefficient of 80% was measured at 100° wedge angle.