RESUMO
We have developed an acceptance-cone-tunable (ACT) electron spectrometer for the highly efficient constant-energy photoelectron mapping of functional materials. The ACT spectrometer consists of the hemispherical deflection analyzer with the mesh-type electrostatic lens near the sample. The photoelectron trajectory can be converged by applying a negative bias to the sample and grounding the mesh lens and the analyzer entrance. The performance of the present ACT spectrometer with neither rotating nor tilting of the sample is demonstrated by the wide-angle observation of the well-known π-band dispersion of a single crystalline graphite over the Brillouin zone. The acceptance cone of the spectrometer is expanded by a factor of 3.30 when the negative bias voltage is 10 times as high as the kinetic energy of photoelectrons.
RESUMO
In order to investigate local structures of electrolytes in electrochemical reactions under the same scan rate as a typical value 100 mV/s in cyclic voltammetry (CV), we have developed an in operando observation system for electrochemical reactions by soft X-ray absorption spectroscopy (XAS) with a potential modulation method. XAS spectra of electrolytes are measured by using a transmission-type liquid flow cell with built-in electrodes. The electrode potential is swept with a scan rate of 100 mV/s at a fixed photon energy, and soft X-ray absorption coefficients at different potentials are measured at the same time. By repeating the potential modulation at each fixed photon energy, it is possible to measure XAS of electrochemical reaction at the same scan rate as in CV. We have demonstrated successful measurement of the Fe L-edge XAS spectra of aqueous iron sulfate solutions and of the change in valence of Fe ions at different potentials in the Fe redox reaction. The mechanism of these Fe redox processes is discussed by correlating the XAS results with those at different scan rates.
RESUMO
This paper presents development of an X-ray pixel detector with a multi-port charge-coupled device (MPCCD) for X-ray Free-Electron laser experiments. The fabrication process of the CCD was selected based on the X-ray radiation hardness against the estimated annual dose of 1.6 × 10(14) photon/mm(2). The sensor device was optimized by maximizing the full well capacity as high as 5 Me- within 50 µm square pixels while keeping the single photon detection capability for X-ray photons higher than 6 keV and a readout speed of 60 frames/s. The system development also included a detector system for the MPCCD sensor. This paper summarizes the performance, calibration methods, and operation status.
RESUMO
A novel variably polarized angle-resolved photoemission spectroscopy beamline in the vacuum-ultraviolet (VUV) region has been installed at the UVSOR-II 750 MeV synchrotron light source. The beamline is equipped with a 3 m long APPLE-II type undulator with horizontally/vertically linear and right/left circular polarizations, a 10 m Wadsworth type monochromator covering a photon energy range of 6-43 eV, and a 200 mm radius hemispherical photoelectron analyzer with an electron lens of a +/-18 degrees acceptance angle. Due to the low emittance of the UVSOR-II storage ring, the light source is regarded as an entrance slit, and the undulator light is directly led to a grating by two plane mirrors in the monochromator while maintaining a balance between high-energy resolution and high photon flux. The energy resolving power (hnu/Deltahnu) and photon flux of the monochromator are typically 1 x 10(4) and 10(12) photons/s, respectively, with a 100 microm exit slit. The beamline is used for angle-resolved photoemission spectroscopy with an energy resolution of a few meV covering the UV-to-VUV energy range.
