Search results for "iTED"
showing 10 items of 2408 documents
Structure sensitive investigations on luminescence centres in Mn-activated LiBaF3 dosimeters
2008
Abstract Prior to x-irradiation the photoluminescence (PL) of Mn-activated LiBaF3 shows a Mn 2 + emission band at 710 nm; the corresponding excitation bands are between 210 and 620 nm. After x-irradiation the PL emission spectrum shows a band peaking at about 610 nm which is tentatively assigned to a perturbed Mn 2 + emission; the intensity of all PL emission bands is increased. Structure sensitive investigations on the radiation-induced emission band were done by detecting electron paramagnetic resonance (EPR) induced changes in the integral PL emission at a temperature of 1.5 K. The analysis of the angular dependent PL-EPR spectra, recorded for different orientations of the magnetic field…
Photoluminescence of neodymium and erbium doped NaLaF4 material
2013
Abstract In the course of this research several NaLaF 4 samples doped with different Er 3+ and Nd 3+ concentrations have been synthesized. For these samples photoluminescence spectra, kinetics and excitation spectra have been measured. It has been found that when samples containing Nd 3+ and Er 3+ impurities are excited in specific Nd 3+ bands not only Nd 3+ but also Er 3+ luminescence bands appear. The studies of the decay kinetics show that there is an energy transfer from Nd 3+ to Er 3+ , moreover “green” and “red” Er 3+ luminescence bands appear as result of two different energy transfer mechanisms. In addition, photoluminescence processes in Nd 3+ ions are investigated. Based on the ob…
The dependence of dichroism in VUV-photoemission on the optical properties of adsorbates: Cs-monolayer on W(110)
1998
Abstract We report on the dependence of dichroic photoemission excited by polarised light on the angle of photon incidence. We measured the difference in the angle-resolved photoemission intensities from Cs-5p semi-corelevels excited by photons of opposite helicity, known as CDAD and of orthogonal linear polarisation—LDAD. We found that the dependence of dichroism on the angle of incidence can not be described by the equations used in the photoemission model for free atomic states. A complex consideration of the parallel and perpendicular components of the vector potential of the exciting light is needed, including the phase shift between these components. The phase shift is produced by the…
Bulk sensitive photo emission spectroscopy of compounds
2007
This work reports about bulk-sensitive, high energy photoelectron spectroscopy from the valence band of CoTiSb excited by photons from 1.2 to 5 keV energy. The high energy photoelectron spectra were taken at the KMC-1 high energy beamline of BESSY II employing the recently developed Phoibos 225 HV analyser. The measurements show a good agreement to calculations of the electronic structure using the LDA scheme. It is shown that the high energy spectra reveal the bulk electronic structure better compared to low energy XPS spectra.
State-to-State Quantum Dynamics Calculations of the C plus OH Reaction on the Second Excited Potential Energy Surface
2011
Accurate three-dimensional quantum-mechanical scattering calculations using a time-indepedent hyperspherical method have been performed for the C((3)P) + OH(X(2)Π) → CO(a(3)Π) + H((2)S) reaction on the second excited potential energy surface of 1(4)A″ symmetry. State-to-state reaction probabilities at a total angular momentum J = 0 have been computed in a wide range of collision energies. Many pronounced resonances have been found, espcially at low energy. The product vibrational distributions are noninverted. The present results therefore suggest that the title reaction proceeds via a long-lived intermediate complex. An approximate quantum-mechanical rate constant has also been calculated,…
Excitation processes of the blue luminescence in crystalline SiO 2 probed by synchrotron radiation measurements
2007
Luminescence properties of crystalline α-quartz were investigated by time-resolved spectroscopy under pulsed synchrotron radiation excitation in the vacuum ultraviolet range. Our results evidence that two emission bands overlap at 2.7 eV, both being observed only at low temperature. The first contribution is excited by band-to-band transition and is related to the radiative recombination of a self trapped exciton occurring in a time scale of a few ms, the second is associated with defects induced in quartz by γ- and β-radiation, is excited at 7.6 eV and its lifetime is 3.6 ns at T = 10 K. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Self-trapped exciton in Li2GeO3
1997
Abstract Self-trapped excitons (STE) are discovered in Li2GeO3 crystal. The PL band at 2.7 eV with a strong Stoke's shift is excited in the intrinsic absorption range of Li2GeO3 crystal, in which the optical gap is situated at 6 eV. The activation energy of the STE luminescence thermal quenching is not monoenergetic and is situated in the range 40–100 meV. The luminescence is strongly polarized. The decay kinetics can be characterized by τ = 0.9 ms at 45 K. At 5 K it can be approximated by fast (0.6 ms) and slow (4–2.5 ms) components. Decay kinetics is determined by triplet state of STE splits in zero magnetic field. Two different excited triplet states (centers) have the average ODMR param…
Coexisting electron emission mechanisms in small metal particles observed in fs-laser excited PEEM
2007
Abstract Silver cluster films deposited on Si(1 1 1) were investigated by spectroscopic photoelectron microscopy using fs-laser excitation tuneable between hν = 1.45–1.65 eV and 2.9–3.3 eV. With increasing coverage the films grown as stepped wedges first exhibit clusters of few nanometers diameter with narrow size distributions that later agglomerate forming larger islands up to about 100 nm diameter. The cluster films have been characterized by SEM, AFM and HR-TEM. In the 3.1 eV range the small clusters emit more effectively and the dependence of electron yield on laser power follows a quadratic power law. Microspectroscopy reveals that the Fermi level onset is sharp(
Electronic spectra of tetrathiafulvalene and its radical cation: analysis of the performance of the time-dependent DFT approach
2002
Abstract The electronic spectra of tetrathiafulvalene and its radical cation have been studied within the framework of the time-dependent density functional theory by using a conventional hybrid functional. The behaviour of the method has been analyzed through the computed vertical excitation energies for the low-lying electronic excited states. Although the procedure provides a correct description of many of the features of the spectra, deviations in the range 0.4–0.7 eV have been obtained for several transitions, from which one can conclude misleading assignments.
Temperature and excitation energy dependence of decay processes of luminescence in Ge-doped silica
2003
We report experimental results on the time decay of photoluminescence at 4.2 eV in Ge-doped silica. This optical emission is assigned to a singlet-singlet transition between electronic states localized on an oxygen deficiency nearby a Ge atom and its radiative decay rate is in competition with an intersystem crossing mechanism that populates an excited triplet state. We investigate the dependence of the lifetime of this photoluminescence on the temperature, in the 6--295 K range, and on the excitation energy, in the ultraviolet and vacuum ultraviolet region. The mean value of the decay time decreases on increasing the temperature, in agreement with the phonon-assisted nature of the intersys…