Results 1 - 10 of 27
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[en] Precision spectroscopy of the Muonium Lamb shift and fine structure requires a robust source of 2S Muonium. To date, the beam-foil technique is the only demonstrated method for creating such a beam in vacuum. Previous experiments using this technique were statistics limited, and new measurements would benefit tremendously from the efficient 2S production at a low energy muon (<20 keV) facility. Such a source of abundant low energy μ has only become available in recent years, e.g. at the Low-Energy Muon beamline at the Paul Scherrer Institute. Using this source, we report on the successful creation of an intense, directed beam of metastable Muonium. We find that even though the theoretical Muonium fraction is maximal in the low energy range of 2–5 keV, scattering by the foil and transport characteristics of the beamline favor slightly higher μ energies of 7–10 keV. We estimate that an event detection rate of a few events per second for a future Lamb shift measurement is feasible, enabling an increase in precision by two orders of magnitude over previous determinations.
[en] Full text: We have studied the crystal chemistry of the Ruddlesden-Popper (RP) phases LaSr3(Fe,Co,Ga)3O10-d with tetragonal symmetry by Neutron Powder Diffraction (NPD) and X-ray Absorption Spectroscopy (XAS) with b different contents of Fe, Co and Ga. NPD data shows the oxygen vacancies are located at the oxygen crystal sites at the central octahedra of the perovskite block in the RP structure. Fe, Co and Ga cations are not homogeneously distributed, showing a sort of preference for particular crystal sites in the perovskite block. For instance, Fe cation tends to accommodate rather at sites with a lower concentration of oxygen vacancies, i.e. at the crystal sites of the perovskite layers next the rock salt layer, whereas Co and more markedly Ga prefer the sites at the central perovskite layer. This cationic distribution was confirmed by Extended X-ray Absorption Fine Structure (EXAFS) analysis, which shows the average coordination number of Fe is always higher than the coordination number obtained for Co and Ga. X-rays Absorption Near Edge Structure (XANES) analysis suggests that the average valence of Fe is always higher than Co and both are higher than 3+ of Ga cations. The results of both EXAFS and XANES analyses are in agreement with the preferential location of the oxygen vacancies at the central perovskite layer where Co and Ga cations are majorly located according to NPD data. The combination of NPD and XAS has been proven effective to assess the crystal chemistry and defect structure of the LaSr3FexCoyGa3-x-yO10-d system. (author)
[en] The synchrotron radiation accelerator facility, so called light source accelerator, becomes widespread all over the world. Especially, the 3rd generation light source is applied to almost of the institute as a most useful machine for material structure science. As it spreads, the machine components is standardized to be able to respond to requirements of light performance from various beam line users. For this standardization, this report overviews how the superconducting technology has been treated as accelerator technology and future perspective of superconducting application in light source accelerator. (author)
[en] Full text: QUATI (QUick X-Ray Absorption Spectroscopy for TIme-Resolved experiments) is a beamline dedicated to high quality X-ray absorption spectroscopy experiment sand in-situ/in operando studies, in XANES (X-Ray Absorption Near Edge Structure) and EXAFS (Extended X-ray Absorption Fine Structure) modes, allowing measurements in the time scale of milliseconds. A multi technique approach will be performed: XRD, Raman, and IR coupled with XAFS experiments. X-ray Emission Spectroscopy (XES) and related techniques will be accessible by a Von Hamos spectrometer, this choice is to enable fast scan acquisition. (author)
[en] Promoting the use of neutron measurement techniques is essential for maintaining and improving the high technological capabilities of the Japanese manufacturing industry. We introduce an example analyzing a lithium secondary battery by using the Bragg edge imaging method, and then make recommendations on what should be done to disseminate to industry use. (author)
[en] Full text: Europium-doped hydroxyapatite has attracted considerable scientific attention to smart drug delivery scaffold applications because of its biocompatible and traceable luminescence features. In this sense, to investigated the europium incorporation mechanism and photoluminescence properties in the presence of surfactant organic molecules the europium doped-hydroxyapatite samples were synthesized via co-precipitation with hexadecyl trimethylammonium bromide (CTAB) micelles mediated approach. Results of the X-ray absorption spectroscopy techniques (XANES and EXAFS) showed that Eu3+ ions were incorporated preferentially at the Ca (1) site with local charge compensating via oxygen interstitial ion for samples calcined under air at 450 °C/4 h °C. Europium(III) luminescence analysis suggested that Ca site symmetry became distorted in CTAB medium. (author)
[en] Full text: The search for new structures, new synthetic paths, and new processing technologies is crucial for the future of electronic devices. In this work, we present an innovative and easy method to prepare polymeric nanoparticles using graphene oxide (GO) as an alternative to traditional surfactants, using the concept of Pickering emulsions. Graphene oxide colloidal dispersion was sonicated along with toluene solutions of the organic semiconductive polymer poly[2,7-(9,9-bis(2- ethylhexyl)-dibenzosilole)-alt-4,7- bis(thiophen-2-yl) benzo-2,1,3-thiadiazole] (PSiF-DBT). The effect of PSiF-DBT concentration (4.5 and 7.5 mg mL-1) and effect of the pH on the GO dispersion were considered in thin films of GO:PSiF-DBT. The molecular structure and molecular orientation of these organic thin films were investigated by near-edge X-ray absorption fine structure (NEXAFS). Ultrafast electron dynamics in the low-femtosecond regime was evaluated by resonant Auger spectroscopy using the core-hole clock (CHC) method . Infrared spectroscopy (IR), scanning and transmission electron microscopy (SEM and TEM) and atomic force microscopy (AFM) images were also performed. The results indicated that the polymer concentration and pH of the medium have a direct influence on the morphology and in the electronic properties of the materials. Infrared spectroscopy suggests the anchoring of Si atoms from the PSiF-DBT in oxygenated groups of graphene oxide, corroborating angle-resolved NEXAFS data that suggests an upright-standing molecular orientation for the thiophene units and a lying-down orientation for the benzothiadiazole units. Resonant Auger spectroscopy indicated that the charge transfer is faster for higher ratio of PSiF:GO in the film. (author)
[en] In various transition metals with different crystal structures, we have demonstrated the validity of sparse modeling (SpM) for the analysis of extended X-ray absorption fine structure (EXAFS). The target data are EXAFS oscillations of Ni, Co, and Fe foils, and these materials have face centered cubic, hexagonal close-packed, and body centered cubic structures, respectively. The SpM method provides the sparse radial distribution functions associated with the respective crystal structures. Although an assumption of crystal structure is required to extract insightful information concerning structural fluctuations in the conventional analysis method, the SpM method allows us to estimate more accurate Debye–Waller factors without such assumption. (author)
[en] Full text: In this study, local and electronic structure of Sr0.998Pr0.002Ti1-yAlyO3 (SrTiO3:Pr,Al) mesocrystals prepared via hydrothermal route were correlated with photoluminescence spectra. Scanning electron microscopy (SEM) images confirm the microcube-shaped morphology and X-ray diffraction measurements revealed pristine structure with Pm3m space group for all SrTiO3:Pr,Al samples without spurious phases. Extended X-ray absorption fine structure (EXAFS) results at Ti K-edge indicate the formation of O vacancies and an increase of the local disorder as a function of Al content. X-ray absorption near edge structure (XANES) at Ti K-, LII,III- and O K-edges, as well as our calculated projected density of states, show Ti off-center displacement, a small deviation from the cubic structure and the local symmetry breaking associated with the hydrothermal method and with dependence of Al incorporation. Photoluminescence spectra for SrTiO3:Pr,Al samples show the expected emissions for the Pr3+ ions incorporated into SrTiO3 lattice. The intensity of some emissions increases as a function of Al content up to 3 at. %. This increasing is associated with the disorder caused by Al, resulting in lower symmetry around Pr3+ sites, which can increase the probabilities of the transitions for Pr3+ ions due to the mixing of the opposite parity in 4f configurational levels. For higher Al concentrations, Pr emissions show a decrease, which is attributed to the quenching of the photoluminescence due to O vacancies. Furthermore, a broad emission is also observed, which is associated with the fact that the intrinsic defects, which are created as a result of hydrothermal route and Al incorporation, can originate intermediary electronic levels in the the band gap. (author)
[en] The cryogenic double Penning-trap experiment Alphatrap aims to test bound-state quantum electrodynamics (BS-QED) under extreme conditions by measuring the magnetic moment (g-factor) of electrons bound to the nucleus of heavy highly charged ions(HCIs). The bound electrong-factor is measured employing the double-trap techniquewhich uses the continuous Stern-Gerlach effect (CSGE) for a nondestructive detectionof the spin state of the ion. The result of this thesis is twofold. In order to improve the achievable precision of future measurements the implementationof sympathetic laser cooling is envisaged. For this purpose a laser system was integrated into the existing setup and laser cooling of Be was demonstrated for the first time at Alphatrap. For the axial temperature of a single beryllium ion an upper limit of 69(30) mK can be given. This demonstration paves the way for further developments towards sympathetic laser cooling of HCIs. Furthermore, the optical access to the Penning trap was used for high-precision laser spectroscopy of the magnetic dipole fine structure transition in the ground state of boronlike argon Ar with an unsurpassed relative uncertainty of the absolute frequency of 9.4×10. To this end, a novel spectroscopy scheme was demonstrated for the first time, which uses the CSGE and does not require a detection of fluorescence. This proof-of-principle method can be extended to other systems, opening up new possibilities to test BS-QED in the strongest electromagnetic fields by investigating the optical hyperfine structure in heavy HCI by means of laser spectroscopy.