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Diagram, valence-to-core, and hypersatellite Kβ X-ray transitions in metallic chromium
Publication . Zeeshan, Faisal; Hoszowska, Joanna; Dousse, Jean Claude; Sokaras, Dimosthenis; Weng, Tsu Chien; Alonso-Mori, Roberto; Kavčič, Matjaz; Guerra, Mauro; Sampaio, Jorge Miguel; Parente, Fernando; Indelicato, Paul; Marques, José Pires; Santos, José Paulo; LIBPhys-UNL; DF – Departamento de Física; John Wiley & Sons, Ltd.
We report on measurements of the Kβ diagram, valence-to-core (VtC), and hypersatellite X-ray spectra induced in metallic Cr by photon single and double K-shell ionization. The experiment was carried out at the Stanford Synchrotron Radiation Lightsource using the seven-crystal Johann-type hard X-ray spectrometer of the beamline 6-2. For the Kβ diagram and VtC transitions, the present study confirms the line shape features observed in previous works, whereas the K h β hypersatellite transition was found to exhibit a complex spectral line shape and a characteristic low-energy shoulder. The energy shift of the hypersatellite relative to the parent diagram line was deduced from the measurements and compared with the result of extensive multiconfiguration Dirac–Fock (MCDF) calculations. A very good agreement between experiment and theory was found. The MCDF calculations were also used to compute the theoretical line shape of the hypersatellite. A satisfactory agreement was obtained between the overall shapes of the experimental and theoretical spectra, but deviations were observed on the low- and high-energy flanks of the hypersatellite line. The discrepancies were explained by chemical effects, which were not considered in the MCDF calculations performed for isolated atoms.
Theoretical and experimental determination of K - And L -shell x-ray relaxation parameters in Ni
Publication . Guerra, Mauro; Sampaio, J. M.; Parente, F.; Indelicato, P.; Hönicke, P.; Müller, M.; Beckhoff, B.; Marques, J. P.; Santos, J. P.; LIBPhys-UNL; DF – Departamento de Física; American Physical Society
Fluorescence yields (FY) for the Ni K and L shells were determined by a theoretical and an experimental group within the framework of the International Initiative on X-ray Fundamental Parameters (FPs) collaboration. Coster-Kronig (CK) parameters were also measured for the L shell of Ni. Theoretical calculations of the same parameters were performed using the Dirac-Fock method, including relativistic and QED corrections. The experimental values for the FY and CK were determined at the PTB laboratory in the synchrotron radiation facility BESSY II, Berlin, Germany, and are compared to the corresponding calculated values.
High-precision measurements of n=2→n=1 transition energies and level widths in He-and Be-like argon ions
Publication . Machado, J.; Szabo, C. I.; Santos, J. P.; Amaro, P.; Guerra, Mauro; Gumberidze, A.; Bian, Guojie; Isac, J. M.; Indelicato, P.; DF – Departamento de Física; LIBPhys-UNL; American Physical Society
We performed a reference-free measurement of the transition energies of the 1s2p1P1→1s21S0 line in He-like argon, and of the 1s2s22p1P1→1s22s21S0 line in Be-like argon ions. The highly charged ions were produced in the plasma of an electron-cyclotron resonance ion source. Both energy measurements were performed with an accuracy better than 3 parts in 106, using a double flat-crystal spectrometer, without reference to any theoretical or experimental energy. The 1s2s22p1P1→1s22s21S0 transition measurement is the first reference-free measurement for this core-excited transition. The 1s2p1P1→1s21S0 transition measurement confirms recent measurement performed at the Heidelberg electron-beam ion trap. The width measurement in the He-like transition provides test of a purely radiative decay calculation. In the case of the Be-like argon transition, the width results from the sum of a radiative channel and three main Auger channels. We also performed multiconfiguration Dirac-Fock calculations of transition energies and rates and have done an extensive comparison with theory and other experimental data. For both measurements reported here, we find agreement with the most recent theoretical calculations within the combined theoretical and experimental uncertainties.
Reference-free measurements of the 1s2s2p 2 P1/2,3/2o →1s22s 2S1/2 and 1s2s2p 4P5/2→1s22s 2S1/2 transition energies and widths in lithiumlike sulfur and argon ions
Publication . Machado, Jorge; Bian, Guojie; Bian, Guojie; Paul, Nancy; Trassinelli, M.; Amaro, Pedro; Guerra, Mauro; Szabo, Csilla I.; Gumberidze, A.; Isac, J. M.; Santos, José Paulo; Desclaux, J. P.; Indelicato, Paul; LIBPhys-UNL; DF – Departamento de Física; American Physical Society
We have measured the widths and energies of the 1s2s2p2P1/2,3/2→1s22s2S1/2 transitions in lithiumlike sulfur and argon, as well as the energies of the forbidden 1s2s2p4P5/2→1s22s2S1/2 M2 transition in both elements. All measurements were performed with a double-flat-crystal spectrometer without the use of any reference line. The transition energy measurements have accuracies ranging from 2.3 to 6.4 ppm depending on the element and line intensity. The widths and the intensity ratios of the 1s2s2p2P1/2,3/2→1s22s2S1/2 lines have also been measured. These are reference-free measurements of transitions in core-excited lithiumlike ions and have an accuracy comparable to the best relative measurements. We have also performed multiconfiguration Dirac-Fock calculations of the widths, energies, and intensity ratios. An extensive comparison between existing experimental results and theory is performed, and Bayesian techniques are employed to extract the energy of the 1s2p24P1/2→1s22p2P1/2 transition in sulfur and identify contaminant transitions.
New insights into the red and green pigments in the illuminated foral charter of Setubal (1515) by combined use of μ-Raman and X-ray fluorescence spectrometry
Publication . Guerra, Mauro; Carvalho, Maria Luisa; Le Gac, Agnès; Manso, Marta; Mortari, Camila; Longelin, Stephane; Pessanha, Sofia; LIBPhys-UNL; DF – Departamento de Física; DCR - Departamento de Conservação e Restauro; AIP - American Institute of Physics
The richly decorated foral charter attributed by D. Manuel I of Portugal, in 1515, to the village of Setubal, was studied using Energy Dispersive X-ray Fluorescence spectrometry and Raman micro-spectroscopy. An in situ characterization of the pigments used in the production of this masterpiece showed a very different pigment palette choice when compared to other similar Manueline charters. The red and green pigments are particularly puzzling, as the widely used mercury- and copper-based pigments, vermillion and malachite, respectively, were not found in the illuminated frontispiece. Instead, the cheaper lead-based pigment minium was used in the King's flag, while a mixture of copper sulfates was found for the green color, identified by means of micro-Raman spectroscopy. This result led to a new look at the conception that only one Royal workshop existed for the elaboration of Manueline foral charters.
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Fundação para a Ciência e a Tecnologia
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SFRH
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SFRH/BPD/92455/2013