Search results for "electromagnetic [current]"

Effects of Ionising Radiation on Optical Properties of Lithium Niobate Single Crystals

2005

Studies of thermal and γ-irradiation effects on the optical properties in congruent lithium niobate single crystals containing Mg and Gd dopants including samples with double dopants Y, Mg are reported. Formation of defects at irradiation and thermal treatment of the samples is explored by analysis of the behaviour of electron absorption spectra. Considerable increase of absorption with the dose of γ-radiation is observed at 500 nm. The changes of absorption examined under different conditions are explained by creation and destruction of Nb 4+ defects.

Local structure of copper nitride revealed by EXAFS spectroscopy and a reverse Monte Carlo/evolutionary algorithm approach

2016

Physica scripta 91(5), 054003 (2016). doi:10.1088/0031-8949/91/5/054003

Low Temperature Optical Absorption by Magnons in KNiF3 and NiO Single-Crystals

2000

Optical absorption spectra of KNiF3 and NiO stoichiometric single-crystals were measured at 5 K in the range from 4000 to 50000 cm-1. The observed bands are interpreted based on the energy levels diagram for Ni2+ (3d 8 ) ion in a cubic crystal field. The crystal-field parameter Dq is equal to 766 cm-1 in KNiF3 and 890 cm-1 in NiO. Particular attention is paid to the band due to the magnetic-dipole 3A2g(F)→3T2g(F) transition, located at 7700 cm-1 in KNiF3 and at 8900 cm-1 in NiO. We show that the energy difference between the two peaks, located at the low energy side of the band, is related to the zone-center (k=0) one-magnon energy, so that the low-energy peak is attributed to the pure exci…

Optical, X-ray absorption and photoelectron spectroscopy investigation of the Co site configuration in Zn1−xCoxO films prepared by pulsed laser depos…

2007

Abstract In this paper, we investigate the Co site configuration in Zn1−xCoxO thin films by means of different spectroscopic techniques. Thin films were prepared by pulsed laser deposition with Co proportion from 1% to 30%. The Co 2p doublet observed in the X-ray photoelectron spectra exhibits the spin–orbit splitting and shake-up satellites typical of Co+2 ionization states. X-ray absorption spectra at the Co K-edge, taken in fluorescence mode, unambiguously show that Co atoms are in tetrahedral configuration substituting for Zn over the whole composition range. Optical absorption spectra provide further evidence of the tetrahedral coordination of Co cations, both through the internal tran…

Thickness Inhomogeneity Effect in EXAFS Spectroscopy

2005

In many cases x-ray absorption spectra measured in transmission mode are degraded by an inhomogeneity in thickness of the samples. As a result, the EXAFS amplitude is decreased and information about the coordination numbers is distorted. To avoid this influence, it is necessary to prepare a homogeneous sample. But, for powder samples, thick inhomogeneous foils, and sputtered films this is not possible. Absorption spectra on these samples should be corrected for the thickness inhomogeneity effect.To correct an absorption spectrum it is necessary to know the sample thickness distribution function. We propose a method of solving an integral equation for a distribution function as an inverse pr…

Molecular dynamics simulations of EXAFS in germanium

2011

AbstractClassical molecular dynamics simulations have been performed for crystalline germanium with the aim to estimate the thermal effects within the first three coordination shells and their influence on the single-scattering and multiple-scattering contributions to the Ge K-edge extended x-ray absorption fine structure (EXAFS).

Analysis of extended x-ray absorption fine structure data from copper tungstate by the reverse Monte Carlo method

2014

The static disorder and lattice dynamics of crystalline materials can be efficiently studied using reverse Monte Carlo simulations of extended x-ray absorption fine structure spectra (EXAFS). In this work we demonstrate the potentiality of this method on an example of copper tungstate CuWO4. The simultaneous analysis of the Cu K and W L3 edges EXAFS spectra allowed us to follow local structure distortion as a function of temperature.

Optical Spectra and Direct Optical Transitions in Amorphous and Crystalline ZnO Thin Films and Powders

2010

Comparative studies of ZnO crystalline and amorphous thin films and nanocrystalline powders are reported. The UV-visible optical spectra were analyzed with special attention paid to the direct optical bandgap. Atmospheric radio-frequency barrier torch discharge and pulsed hollow cathode sputtering techniques for the film fabrication were used. For the crystalline films, similar values of the direct optical bandgap were found independent of the growth method used. The analysis of the amorphous films and powders revealed a pronounced Urbach-like exponential absorption tail approaching the bandedge. For the powders, the bandgap energies were larger than those for the crystalline and amorphous …

Far-infrared intersubband absorption inp-typeGaAs/AlxGa1−xAssingle heterojunctions under uniaxial compression

2001

Thermal behavior of absorbing and scattering glass media containing molecular water impurity

2005

The effect of the presence of molecular water impurity of various concentrations in absorbing and scattering glass media on the temperature field in a layer subjected to thermal infrared radiation is investigated. The analysed medium is treated as a multicomponent medium consisting of glass matrix and water impurity. The effect of radiation on the medium is expressed by heat sources in each component due to absorption of radiation. It is shown that the presence of water impurity in the glass medium should be accounted for in order to predict the temperature distribution during radiation action. The effect of scattering of radiation by water molecules on thermal and diffusive processes in th…