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31.
The optical properties of ultrathin Au films on silicon have been studied in the infrared over a wide frequency range from 200 to 10,000 cm(-1). Thick films show a Drude behavior; i.e., with increasing frequency the transmission increases; for films below the percolation threshold at about 5 nm a negative slope for the frequency-dependent transmission is observed. When the thickness is further reduced, between 1 and 3 nm an anomaly occurs: the relative transmission reaches maximum values above 100% compared with the bare substrate, indicating an antireflection coating of nanometer thickness for light of 5 microm wavelength. This anomaly can be explained in the framework of effective-medium theories. 相似文献
32.
Summary. The combination technique is a method to reduce the computational time in the numerical approximation of partial differential
equations. In this paper, we present a new technique to analyze the convergence rate of the combination technique. This technique
is applied to general second order elliptic differential equations in two dimensions. Furthermore, it is proved that the combination
technique for Poisson's equation convergences in arbitrary dimensions.
Received September 25, 1997 / Revised version received October 22, 1998 / Published online September 7, 1999 相似文献
33.
Hans-Christian Herbig Srikanth B. Iyengar Markus J. Pflaum 《Letters in Mathematical Physics》2009,89(2):101-113
We discuss BFV deformation quantization (Bordemann et al. in A homological approach to singular reduction in deformation quantization,
singularity theory, pp. 443–461. World Scientific, Hackensack, 2007) in the special case of a linear Hamiltonian torus action.
In particular, we show that the Koszul complex on the moment map of an effective linear Hamiltonian torus action is acyclic.
We rephrase the nonpositivity condition of Arms and Gotay (Adv Math 79(1):43–103, 1990) for linear Hamiltonian torus actions.
It follows that reduced spaces of such actions admit continuous star products.
相似文献
34.
We construct a nontrivial cyclic cocycle on the Weyl algebra of a symplectic vector space. Using this cyclic cocycle we construct an explicit, local, quasi-isomorphism from the complex of differential forms on a symplectic manifold to the complex of cyclic cochains of any formal deformation quantization thereof. We give a new proof of Nest-Tsygan's algebraic higher index theorem by computing the pairing between such cyclic cocycles and the K-theory of the formal deformation quantization. Furthermore, we extend this approach to derive an algebraic higher index theorem on a symplectic orbifold. As an application, we obtain the analytic higher index theorem of Connes-Moscovici and its extension to orbifolds. 相似文献
35.
Kowarik S Gerlach A Sellner S Schreiber F Pflaum J Cavalcanti L Konovalov O 《Physical chemistry chemical physics : PCCP》2006,8(15):1834-1836
We study the growth and structure of thin films of the organic semiconductor rubrene during organic molecular beam deposition (OMBD) on silicon oxide in situ and in real time using X-ray scattering. Using in situ grazing incidence diffraction (GID) we find a small degree of local order but an otherwise largely disordered structure, consistent with out of plane scans. Monitoring the surface morphology in real time during growth, we find relatively smooth films (surface roughness sigma below approximately 15 A for thicknesses up to at least 600 A) and a significant delay before the onset of roughening. This anomalous roughening in the beginning and crossover to normal roughening later during growth may be related to conformational changes of rubrene in the early stages of growth. 相似文献
36.
A stable iterative solver for the simulation of optical waves in metals using finite difference frequency domain (FDFD) method is presented. The corresponding discretization of Maxwell's equations enables simulating electromagnetic waves in structures when materials with negative permittivity are involved. Convergence of the iterative solver is proved for positive and negative permittivities. Numerical results are presented for a thin‐film silicon solar cell structure containing silver back contact. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
37.
Christoph Pflaum 《Numerische Mathematik》1998,79(1):141-155
A multilevel algorithm is presented that solves general second order elliptic partial differential equations on adaptive
sparse grids. The multilevel algorithm consists of several V-cycles in - and -direction. A suitable discretization provide that the discrete equation system can be solved in an efficient way. Numerical
experiments show a convergence rate of order for the multilevel algorithm.
Received April 19, 1996 / Revised version received December 9, 1996 相似文献
38.
Using the method of continuous projective resolutions established by Alain Connes, we calculate the continuous Hochschild homology and cohomology groups of the Fréchet algebra of smooth functions on a manifold M. These (co)homology groups are allowed to take values in the Fréchet space E of smooth sections of a vector bundle E over M and in the strong dual E*. Moreover, we show that in the cohomological case the differential and continuous Hochschild cohomologies are naturally isomorphic. 相似文献
39.
Due to the complex lateral structure of Distributed Feedback lasers (DFB) and Master Oscillator Power Amplifiers (MOPAs), one-dimensional methods like the classical Transfer Matrix Method (TMM) are not suitable for simulating the optical wave in these devices. Therefore, we applied Trigonometric Finite Wave Elements (TFWE) that generalize the TMM in two or three dimensions. By coupling the dynamic wave equation with simplified temperature and drift-diffusion models, we can simulate the dynamic behavior of DFB lasers and MOPAs. Furthermore, by Fourier transformation, we can calculate the modes of the laser cavity and the corresponding wavelengths. By this approach, the influence of injection current and temperature on the resulting modes and output power can be analyzed in detail. 相似文献
40.
B. Lins F. Pflaum R. Engelbrecht B. Schmauss 《Applied physics. B, Lasers and optics》2011,102(2):293-301
We present initial results of an investigation of the near infrared absorption spectrum of 15NH3 between 6468 and 6692 cm−1. A widely tunable external cavity diode laser is used in a direct absorption setup to determine the line positions and line
strengths of several lines in that spectral range. Line data measurements on a 14NH3 sample are used for validation of the setup by comparison of the results with available literature data. The presented overview
measurements on absorption lines of 15NH3 have been performed to serve as a starting point for candidate line selection for prospective isotopic ratio measurements
of 14NH3 and 15NH3. 相似文献