Search results for "Tungsten"
showing 10 items of 372 documents
EXAFS Study of PressureInduced Phase Transition in SrWO4
2005
Pressure-induced scheelite-to-wolframite structural phase transition in SrWO4 was studied using two complementary techniques—x-ray absorption spectroscopy and x-ray diffraction (XRD). In situ XRD and W L3-edge EXAFS measurements were performed using the synchrotron radiation. The experiments were done at room temperature in the pressure range from 0 to 30 GPa using the diamond anvil cell. The XRD results unambiguously show that SrWO4 transforms from the tetragonal scheelite phase to the monoclinic wolframite-type phase at about 11.7 GPa. Locally this transition appears as a change of the tungsten ions coordination from regular tetrahedral to distorted octahedral. The analysis of the EXAFS d…
Photocurrent spectroscopy study of passive films on hafnium and hafnium–tungsten sputtered alloys
2003
Abstract Anodic and air-formed films on sputtered Hf and W–Hf alloys of different composition have been investigated by Rutherford back scattering, photocurrent spectroscopy (PCS) and transmission electron microscopy (TEM) techniques. In alkaline solutions the PCS data suggest the formation on Hf metal of a duplex layer with anodic hafnia covered by an external layer of composition close to HfO(OH) 2 . This last compound is also present on Hf air-formed films. In acidic solutions the initial oxy-hydroxide film disappears at high anodising potentials ( V f >10 V). In the case of W–Hf alloys films of different composition and semiconducting behaviour are formed by air exposure or by anodising…
AN EXPERIMENTAL PROOF OF THE BACK-SCATTERING MODEL FOR DICHROIC EFFECTS IN VUV PHOTOEMISSION
2002
The energy dependence of the circular dichroism in the angular distribution of photoelectrons (CDAD) was investigated from the shallow Cs 5p core levels. Cesium was prepared in a hexagonal ordered monolayer on W(110). The results are mainly influenced by scattering of the photoelectrons within the adlayer. At low energies, the behavior observed is described by means of a model that treats only the back-scattering of photoelectrons at the potential step between the adlayer and the substrate. It leads to a simple method determining the position of the monolayer with respect to the substrate. In this approach, the back-scattering model is matched with the measured energy dependence of the CDA…
Direct measurement of the radiative tail in electron scattering from atomic nuclei
1985
We have made a direct measurement of the radiative tail of the eleastic peak from several tungsten targets. The measured data have been compared to the results expected for both internal and external bremsstrahlung contributions. Even for targets as thick as 4% of a radiation length of tungsten, agreement between the results of the experiment and the predictions of the theory has been found to be unexpectedly good.
FIRST RESULTS WITH THE RISING ACTIVE STOPPER
2008
This paper outlines some of the physics opportunities available with the GSI RISING active stopper and presents preliminary results from an experiment aimed at performing beta-delayed gamma-ray spectroscopic studies in heavy-neutron-rich nuclei produced following the projectile fragmentation of a 1 GeV per nucleon 208 Pb primary beam. The energy response of the silicon active stopping detector for both heavy secondary fragments and beta-particles is demonstrated and preliminary results on the decays of neutron-rich Tantalum ( Ta ) to Tungsten ( W ) isotopes are presented as examples of the potential of this technique to allow new structural studies in hitherto experimentally unreachable he…
Nanoscale X-ray detectors based on individual CdS, SnO2 and ZnO nanowires
2021
Abstract The development of nanoscale X-ray sensors is of crucial importance to achieve higher spatial resolution in many X-ray-based techniques playing a key role in materials science, healthcare, and security. Here, we demonstrate X-ray detection using individual CdS, SnO 2 , and ZnO nanowires (NWs). The NWs were produced via vapor–liquid–solid technique and characterized using X-ray diffraction, scanning, and transmission electron microscopy . Electrical measurements were performed under ambient conditions while exposing two-terminal NW-based devices to X-rays generated by a conventional tungsten anode X-ray tube. Fast and stable nanoampere-range X-ray beam induced current (XBIC) in resp…
Messung der Spinpolarisation von 900 eV-Elektronen nach elastischer Streuung an Schwermetallfolien in Abh�ngigkeit von der Targettemperatur
1967
900 eV electrons are elastically scattered by solid targets of tungsten, platinum and gold. The angular dependence of the scattered intensity and of spin polarizationP(Θ) is investigated as a function of the target temperature. The influence of hydrogen on the scattering process by a gold target is investigated too.
Direct evidence of secondary recoiled nuclei from high energy protons
2008
The production of secondary recoiled particles from interactions between high energy protons and microelectronics devices was investigated. By using NAND Flash memories, we were able to directly obtain analog information on recoil characteristics. While our results qualitatively confirm the role of nuclear reactions, in particular of those with tungsten, a quantitative model based on Monte Carlo and device-level simulations cannot describe the observed results in terms of recoils from proton-W reactions. © 2006 IEEE.
Complex chemistry with complex compounds
2016
In recent years gas-phase chemical studies assisted by physical pre-separation allowed for the investigation of fragile single molecular species by gas-phase chromatography. The latest success with the heaviest group 6 transactinide seaborgium is highlighted. The formation of a very volatile hexacarbonyl compound Sg(CO)6 was observed similarly to its lighter homologues molybdenum and tungsten. The interactions of these gaseous carbonyl complex compounds with quartz surfaces were investigated by thermochromatography. Second-generation experiments are under way to investigate the intramolecular bond between the central metal atom of the complexes and the ligands addressing the influence of re…
Electron recombination with tungsten ions with open f-shells
2017
We calculate the electron recombination rates with target ions W$^{q+}$, $q = 18$ -- $25$, as functions of electron energy and electron temperature (i.e. the rates integrated over the Maxwellian velocity distribution). Comparison with available experimental data for W$^{18+}$, W$^{19+}$, and W$^{20+}$ is used as a test of our calculations. Our predictions for W$^{21+}$, W$^{22+}$, W$^{23+}$, W$^{24+}$, and W$^{25+}$ (where the experimental data are not available) may be used for plasma modelling in thermonuclear reactors. The results for the temperature dependent rates for each ion are fitted with the standard analytical expressions to make them easy to use. All of these ions have an open e…