Search results for "absorption spectroscopy"
showing 10 items of 828 documents
EXAFS study of the local structure of crystalline and nanocrystalline Y2O3using evolutionary algorithm method
2015
Temperature-dependent local structure and lattice dynamics of yttria (Y2O3) were studied by X-ray absorption spectroscopy. Novel method, which combines the reverse Monte Carlo and evolutionary algorithm techniques, was applied for the analysis of extended X-ray absorption fine structure at the Y K-edge. This approach allowed us to reconstruct 3D atomic structure models of crystalline and nanocrystalline Y2O3.
Modification of LiF structure by irradiation with swift heavy ions under oblique incidence
2013
The structural modifications of LiF irradiated with swift heavy ions under oblique angles have been investigated using AFM, SEM, chemical etching, nanoindentation and optical absorption spectroscopy. LiF crystals were irradiated under incidence angles of 30 and 70 degrees with 2.2 GeV Au (fluence 57?l011 ions-cm2) and 150 MeV Kr ions (fluence 1012?1014 ions?cm?2). Structural study on sample cross-sections shows that two damage regions ? (1) nanostructured zone and (2) dislocation ? rich zone, which are typical for irradiations at normal incidence, appear also in samples irradiated under oblique angles. However in the latter case a more complex structure is formed that leads to stronger ion-…
Vacuum-ultraviolet absorption of hydrogenated and deuterated silanol groups and interstitial water molecules in amorphousSiO2
2005
Vacuum-ultraviolet (VUV) absorption cross sections of hydrogenated and deuterated silanol groups (SiOX, where $\mathrm{X}=\mathrm{H}$ or D) as well as interstitial water molecules $({\mathrm{X}}_{2}\mathrm{O})$ in amorphous $\mathrm{Si}{\mathrm{O}}_{2}$ $(a\text{\ensuremath{-}}\mathrm{Si}{\mathrm{O}}_{2})$ were determined between photon energies of 7 and $8.2\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. The absorption bands for the deuterated species are blueshifted compared to those for the hydrogenated ones by $\ensuremath{\sim}0.1\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}0.2\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ as a result of a decrease in the zero-point energy associat…
Optical absorption of magnesia-supported gold clusters and nanoscale catalysts: Effects due to the support, clusters, and adsorbants
2005
Polarization-resolved optical spectra of magnesia-supported gold clusters ${\mathrm{Au}}_{N}∕\mathrm{Mg}\mathrm{O}$ $(N=1,2,4,8)$, bound at a surface color center ${F}_{s}$ of the MgO(100) face, are calculated from the time-dependent density functional theory. The optical lines for $N=1,2$ are dominated by transitions that involve strong hybridization between gold and ${F}_{s}$ states whereas for $N=4,8$ intracluster transitions dominate. The theoretical optical spectra are sensitive to cluster structure and adsorbants (here CO and ${\mathrm{O}}_{2}$ molecules on ${\mathrm{Au}}_{8}∕{F}_{s}@\mathrm{Mg}\mathrm{O}$) which suggests polarization-resolved optical spectroscopy as a powerful tool t…
Hardening in LiF induced by fast Ni ions and recovery of properties under annealing
2005
The recovery of hardness and optical absorbance of LiF crystals irradiated with 640 MeV nickel ions under annealing at 450–810 K is investigated. Recovery of the hardness of irradiated crystals is initiated at temperatures above 530 K, at which a transition from a complex absorption spectrum to a spectrum with only one broad peak at 275 nm is observed. Activation energy of 0.13 eV ± 0.02 eV, which is close to that necessary for migration of H centers, is obtained from the annealing data. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Colour centres in LiBaF3 crystals
1998
Abstract The origin of the absorption bands in LiBaF 3 created by X-ray irradiation at RT has been investigated. It is found that three absorption bands at 270, 320 and 430 nm represent different electron transitions within a radiation defect effectively created in LiBaF 3 single crystals. Following the Mollwo–Ivey relation we discuss investigations of optical dichroism, magnetic optical dichroism, as well as the assumptions regarding the accumulation kinetics of these absorption bands, the F centre being the main radiation defect created by X-rays in undoped LiBaF 3 crystals at RT.
Transient absorption spectra and relaxation kinetics in Nb-doped PbWO4 scintillating crystals
2001
Abstract The spectra and relaxation kinetics of absorption induced by a pulsed electron beam were studied for undoped and Nb-doped PbWO 4 single crystals. A significant influence of Nb doping on transient absorption was found. The influence of Nb doping on the relaxation kinetics is proposed to be due to an oxygen vacancy involving electron–hole recombination. A delay was observed (35– 50 ns ) between the growth of F-centers and the irradiation pulse. A large portion of the F-centers decays within ∼16 μs due to recombination with mobile holes. The prolonged recombination processes are responsible for the decrease of the scintillation yield in PbWO 4 : Nb crystals.
Synchrotron Radiation-Based Micro-XANES and Micro-XRF Study of Unsuccessfully Produced Egyptian Blue from the Late Hellenistic Production Site of Kos…
2021
International audience; This paper examines the production technology of Egyptian blue, an ancient artificial pigment, through the investigation of an unsuccessfully produced pellet derived from the Hellenistic production site of Kos (Dodecanese, Greece). This heterogeneous material was investigated by a combination of laboratory and synchrotron radiation-based (SR) techniques: scanning electron microscopy coupled with energy-dispersive Xray spectrometry, micro-Raman spectroscopy, high-resolution SR micro-X-ray fluorescence spectroscopy, and SR micro-X-ray absorption near-edge structure spectroscopy (XANES), at the ID21 beamline of the European Synchrotron Radiation Facility. Principal comp…
Scintillation properties of possible cross-luminescence materials
1993
Abstract Employing X-ray and gamma-ray excitation, we studied the scintillation properties of KMgF 3 , KYF 4 :Rb, K 2 YF 5 , KLuF 4 , RbMgF 3 , KZnF 3 and BaTm 2 F 8 crystals. The first four crystals produce intrinsic cross-luminescence (CL) with a decay time of about 1.5 ns. Intrinsic CL was not observed for the other crystals. Emission spectra, results of decay time measurements, and estimates for the absolute light yield are presented.
Multiple scattering theory for non-local and multichannel potentials.
2012
International audience; Methodological advances in multiple scattering theory (MST) in both wave and Green's function versions are reported for the calculation of electronic ground and excited state properties of condensed matter systems with an emphasis on core-level photoemission and absorption spectra. Full-potential MST is reviewed and extended to non-local potentials. Multichannel MST is reformulated in terms of the multichannel density matrix whereby strong electron correlation of atomic multiplet type can be accounted for in both ground and excited states.