The Experts below are selected from a list of 23253 Experts worldwide ranked by ideXlab platform
K H Johnson - One of the best experts on this subject based on the ideXlab platform.
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recent applications of the scf xα Scattered Wave method to complex molecules and solids
International Journal of Quantum Chemistry, 2009Co-Authors: K H JohnsonAbstract:Recent applications of the SCF-Xα Scattered–Wave method to metal coordination systems, biological molecules, and localized states in complex solids are outlined.
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a Scattered Wave model of electronic structure of eu2 in bamgal10o17 and associated excitation processes
Journal of Luminescence, 2002Co-Authors: K C Mishra, M Raukas, A Ellens, K H JohnsonAbstract:The excitation spectrum of a commercial blue phosphor, BaMgAl10O17:Eu2+ (BAM) has been investigated assuming a distribution of the activator ions at three different sites: Beevers–Ross, anti-Beevers–Ross and mid-oxygen sites in the intermediate plane. The energy levels and Wavefunctions of the Eu2+ ions located at these sites have been calculated using the self-consistent field Xα Scattered Wave cluster molecular orbital approach (SCF-Xα-SW-MO). The molecular orbital eigenvalues are then utilized to develop an energy level diagram and the associated excitation spectrum. A comparison of the calculated excitation peaks with those from experiment provides support for distribution of Eu2+ ions at multiple sites in BAM.
W Wurth - One of the best experts on this subject based on the ideXlab platform.
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orientation and bonding of thiophene and 2 2 bithiophene on ag 111 a combined near edge extended x ray absorption fine structure and xα Scattered Wave study
Surface Science, 2000Co-Authors: P Vaterlein, M Schmelzer, J Taborski, T Krause, F Viczian, M Basler, R Fink, E Umbach, W WurthAbstract:The adsorption of thiophene and 2,2′-bithiophene on Ag(111) was studied using temperature programmed desorption and near-edge X-ray-absorption fine-structure (NEXAFS). The assignment of the NEXAFS resonances is supported by Xα Scattered-Wave calculations. For thiophene we identify a compressed and a relaxed monolayer species. Whereas the molecules in the latter state are adsorbed parallel to the surface, they are adsorbed in an inclined geometry in the compressed monolayer. For 2,2′-bithiophene, in contrast, we find a mono- and a bi-layer species, which are both adsorbed in a flat-lying geometry on the Ag(111) surface. All adsorption species are weakly bound to the surface and comprise of undissociated molecules. In addition we demonstrate an X-ray-induced partial polymerization of thiophene multilayers.
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adsorption induced bending of a triatomic molecule near edge x ray absorption fine structure spectroscopy investigation of n2o adsorbed on different ni 111 surfaces
Physical Review Letters, 1996Co-Authors: P Vaterlein, J Taborski, T Krause, R Fink, E Umbach, B Basler, V Wustenhagen, W WurthAbstract:A monolayer of N2O/Ni(111), a submonolayer species, and a monolayer of N2O/Ni\(111\)+O p[2×2] were studied using near-edge x-ray absorption fine-structure spectroscopy. From the polarization dependence we derive bent N2O molecules for the monolayer species whereas the two other species remain linear upon adsorption. Using the Xα-Scattered-Wave method the polarization dependence of the three π* resonances was calculated explicitly for linear and bent N2O molecules. The calculations reproduced the experimental results quantitatively, yielding a bond angle of 165° for the monolayer species.
Peter Monk - One of the best experts on this subject based on the ideXlab platform.
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on the use of transmission eigenvalues to estimate the index of refraction from far field data
Inverse Problems, 2007Co-Authors: Fioralba Cakoni, David Colton, Peter MonkAbstract:We consider the scattering of time harmonic electromagnetic plane Waves by a bounded inhomogeneous medium and show that under certain assumptions a lower bound on the index of refraction can be obtained from a knowledge of the smallest transmission eigenvalue corresponding to the medium. It is then shown by numerical examples that this eigenvalue can be determined from a knowledge of the far field pattern of the Scattered Wave, thus providing a practical method for estimating the index of refraction from far field data.
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the electromagnetic inverse scattering problem for partly coated lipschitz domains
Proceedings of The Royal Society A: Mathematical Physical and Engineering Sciences, 2004Co-Authors: Peter MonkAbstract:We consider the inverse-scattering problem of determining the shape of a partly coated obstacle in R 3 from a knowledge of the incident time-harmonic electromagnetic plane Wave and the electric far-field pattern of the Scattered Wave. A justification is given of the linear sampling method in this case and numerical examples are provided showing the practicality of our method.
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the linear sampling method for solving the electromagnetic inverse medium problem
Inverse Problems, 2002Co-Authors: Houssem Haddar, Peter MonkAbstract:We consider the inverse scattering problem of determining the shape of an inhomogeneous scatterer in 3 from a knowledge of the time harmonic incident electromagnetic Wave and the far-field pattern of the Scattered Wave with frequency in the resonance region. The approach used is the linear sampling method which does not require a priori knowledge of the characteristics of the medium.
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the linear sampling method for solving the electromagnetic inverse scattering problem
SIAM Journal on Scientific Computing, 2002Co-Authors: Houssem Haddar, Peter MonkAbstract:We consider the inverse scattering problem of determining the shape of an obstacle in $\mathbb R$ from knowledge of the time harmonic incident electromagnetic Wave and the far-field pattern of the Scattered Wave with frequency in the resonance region. The approach used is the linear sampling method which does not require a priori knowledge of either the boundary condition or the connectivity of the scattering obstacle. Numerical examples are given for the case of both a simply connected perfect conductor and multiply connected obstacles satisfying an impedance boundary condition on the boundary of one component and satisfying a perfect conducting boundary condition on the boundary of another component.
P Vaterlein - One of the best experts on this subject based on the ideXlab platform.
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orientation and bonding of thiophene and 2 2 bithiophene on ag 111 a combined near edge extended x ray absorption fine structure and xα Scattered Wave study
Surface Science, 2000Co-Authors: P Vaterlein, M Schmelzer, J Taborski, T Krause, F Viczian, M Basler, R Fink, E Umbach, W WurthAbstract:The adsorption of thiophene and 2,2′-bithiophene on Ag(111) was studied using temperature programmed desorption and near-edge X-ray-absorption fine-structure (NEXAFS). The assignment of the NEXAFS resonances is supported by Xα Scattered-Wave calculations. For thiophene we identify a compressed and a relaxed monolayer species. Whereas the molecules in the latter state are adsorbed parallel to the surface, they are adsorbed in an inclined geometry in the compressed monolayer. For 2,2′-bithiophene, in contrast, we find a mono- and a bi-layer species, which are both adsorbed in a flat-lying geometry on the Ag(111) surface. All adsorption species are weakly bound to the surface and comprise of undissociated molecules. In addition we demonstrate an X-ray-induced partial polymerization of thiophene multilayers.
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adsorption induced bending of a triatomic molecule near edge x ray absorption fine structure spectroscopy investigation of n2o adsorbed on different ni 111 surfaces
Physical Review Letters, 1996Co-Authors: P Vaterlein, J Taborski, T Krause, R Fink, E Umbach, B Basler, V Wustenhagen, W WurthAbstract:A monolayer of N2O/Ni(111), a submonolayer species, and a monolayer of N2O/Ni\(111\)+O p[2×2] were studied using near-edge x-ray absorption fine-structure spectroscopy. From the polarization dependence we derive bent N2O molecules for the monolayer species whereas the two other species remain linear upon adsorption. Using the Xα-Scattered-Wave method the polarization dependence of the three π* resonances was calculated explicitly for linear and bent N2O molecules. The calculations reproduced the experimental results quantitatively, yielding a bond angle of 165° for the monolayer species.
F Simonetti - One of the best experts on this subject based on the ideXlab platform.
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multiple scattering the key to unravel the subWavelength world from the far field pattern of a Scattered Wave
Physical Review E, 2006Co-Authors: F SimonettiAbstract:: For more than a century the possibility of imaging the structure of a medium with diffracting Wave fields has been limited by the tradeoff between resolution and imaging depth. While long Wavelengths can penetrate deep into a medium, the resolution limit precludes the possibility of observing subWavelength structures. Near-field microscopy has recently demonstrated that the resolution limit can be overcome by bringing a probing sensor within one Wavelength distance from the surface to be imaged. This paper extends the scope of near-field microscopy to the reconstruction of subWavelength structures from measurements performed in the far-field. It is shown that the distortion undergone by a Wave field as it travels through an inhomogeneous medium and the subsequent generation of local evanescent fields encode subWavelength information in the far-field due to multiple scattering within the medium. This argument is proved theoretically and supported by a limited view experiment performed with elastic Waves in which an image with a resolution better than a third of the Wavelength is achieved.
