Giorgio Margaritondo

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We report on x-ray photoemission and absorption measurements on ruthocuprate and SrRuO3 samples. The ruthocuprates include samples that are both weak ferromagnets and superconductors for part of the phase diagram. The results indicate that adding hydrogen changes the many-body response on the CuO2 planes. The results further indicate that ferromagnetic order alters the core level states. We discuss implications of these data.

Angle-resolved photoemission spectroscopy reveals very surprising strain-induced effects on the electronic band dispersion of epitaxial La2-xSrxCuO4-delta thin films. In strained films we measure a band that crosses the Fermi level (E-F) well before the Brillouin zone boundary. This is in contrast to the flat band reported in unstrained single crystals and in our unstrained films, as well as in contrast to the band flattening predicted by band structure calculations for in-plane compressive strain. In spite

The ability to couple high-resolution specimen imaging with chemical state analysis allows problems in biology and medicine to be approached in a novel and powerful way. Element specific chemical state analysis can be performed at tunable synchrotron X-ray sources through core level absorption spectroscopy, and a number of methods have been developed to routinely use this technique at the microscopic scale relevant to cellular phenomena. A diverse range of biological specimens has been studied in the MEPHIS

A comparison of photoemission spectra from Ag clusters deposited on silicon oxide and on cleaved silicon substrate has allowed us to discriminate initial and final state effects in the binding energies of the valence band and of the 3d core level of the metal.

Recent, striking examples of x-ray image sharpening are based on Fresnel edge diffraction. A simple model shows that image sharpening can be achieved under less stringent conditions as could be thought. The extreme spatial coherence of third-generation synchrotron sources appears helpful but not strictly necessary, and high time coherence is not an essential requirement. These conclusions, consistent with the results of other authors, strongly enhance the potential impact in medical x-ray applications, mate

High-resolution angle-resolved photoemission and core-level photoemission measurements were performed on single crystal samples of the quasi-one-dimensional material (TaSe4)(2)I and the cuprate superconductor Bi2Sr2CaCu2O8+x. Resistivity measurements were performed on both materials. X-ray diffraction, transmission electron microscopy (TEM), and AC susceptibility measurements were performed on the cuprate samples. The data indicate that photoemission studies provide key information in understanding the phys

EXPERIMENTAL evidence of the preferential uptake of aluminium by GABAergic neurones and glial cells was provided by synchrotron spectromicroscopy studies. We observed rat cerebellar cultures enriched for GABAergic neurones or glial cells exposed to aluminium ions, detecting the presence and identifying the chemical status of aluminium on cell structures.

Special relativity (SR) determines the properties of synchrotron radiation, but the corresponding mechanisms are frequently misunderstood. Time dilation is often invoked among the causes, whereas its role would violate the principles of SR. Here it is show ...

We performed a photoemission investigation of the electronic structure of PrNiO3 and NdNiO3 through the first order (paramagnetic) metal to (antiferromagnetic) insulator transition. Surprisingly, the data reveal a temperature-dependent loss of spectral weight near the chemical potential, which extends well below the coincident metal-insulator (T-MI) and magnetic (T-Neel) transition temperatures. This is in contrast with the behavior in SmNiO3 and EuNiO3, where the two transitions are separate. The spectral

We present a fundamental development step of a new technique to read and digitize ancient handwritten documents. Chemical analysis by x-ray fluorescence and x-ray tomography enabled us to decipher words and drawings from inside a closed, 200-pages 18 th ce ...

In order to investigate FeSO4, ZnSO4 (the two of main metal compositions of Shanghai PM2.5 (particle matter with those aerodynamical diameter

I discuss some of the didactic problems in the introduction to quantum physics based on the concept of photon. I specifically argue that the derivation of the photon energy from the relativistic Doppler shift offers stimulating didactic opportunities. A detailed form of this derivation reveals the subtle link between relativity and quantization, and also helps in elucidating the meaning of the invariance of the speed of light

We present several examples of the applications of a novel microradiology approach based on unmonochromatized synchrotron x-rays. The approach - mostly implemented on the ICPCIR (International Consortium on Phase Contrast Imaging and Radiology) Beamline at ...

The oxygen content determines the transport properties of Ba2YCu3O7+x and EuBa2Cu3O7+x, and in particular their superconducting behavior at high temperatures. The authors studied the changes in the Ba2YCu3O7+x electronic structure which are caused by modifications in the amount of oxygen. The modifications were achieved either by thermal annealing or by exposure to `white' synchrotron radiation which causes ox

We present recent results of the study of surface properties and quantum efficiency (QE) of CsI photocathodes prepared on various substrates. Microanalysis methods provide laterally resolved surface morphology and chemical composition of the photoemissive film. Integral measurements of the QE of CsI were done with a monochromator system and a RICH device. It was shown that CsI films deposited on large area Ni- or Ni-Au-coated printed circuit electrodes have a uniform crystalline structure and an average QE

CsI photocathodes were studied in order to evaluate their potential use as large photoconverters in RICH detectors for the PID system at ALICE (LHC in heavy ion collider mode). It has been demonstrated that a quantum efficiency comparable to the reference value obtained on small samples can be obtained on CsI layers evaporated on large pad electrodes operated in a MWPC at atmospheric pressure. We present a survey of the results obtained in the laboratory on small samples irradiated with UV-monochromatic bea

Synchrotron-radiation sources have become, since the late 1960's, one of the fundamental experimental tools for surface and interface research. Only recently, however, a related type of photon sources - the free-electron lasers (FELs) - has begun to make important contributions to this field. For example, FELs have been used to reach unprecedented levels of accuracy and reliability in measuring semiconductor interface energy barriers. We review some of the present and proposed experiments that are made poss

High-resolution angle-resolved photoemission (ARPES) displays quasi-one dimensional (1D) electronic states in the insulating molybdenum red bronze K0.33MoO3, in good qualitative agreement with band structure calculations. Combined ARPES, optical conductivity, and electrical resistivity data underline the importance of defects which pin the Fermi level within the gap. The ARPES line shape exhibits the same strong-coupling features observed in the blue bronze K0.3MoO3, a related 1D Peierls conductor. We specu

The third generation sources of soft X-rays, ALS and ELETTRA, have been producing data in surface and interface science for over two years. The impact of their ultrahigh brightness is quite evident, particularly as far as photoemission techniques are concerned. We illustrate this point with a short review of very recent examples from ELETTRA, in the specific domains of time resolution, high lateral resolution and high energy resolution.

It is shown that an elementary semi-quantitative approach explains essential features of the X-ray free-electron laser mechanism, in particular those of the gain and saturation lengths. Using mathematical methods and derivations simpler than complete theor ...

Giorgio Margaritondo

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Photoabsorption and core-level photoemission study of ruthocuprates

Strain and high temperature superconductivity: Unexpected results from direct electronic structure measurements in thin films

Synchrotron spectromicroscopy in medicine and biology

Binding-Energies and Cluster Formation at Low Metal-Deposition - Ag on Si and Sio2

Coherence-based edge diffraction sharpening of x-ray images: A simple model

Progress in understanding VUV photoemission in low-dimensionality systems

Aluminum in Rat Cerebellar Primary Cultures - Glial-Cells and Gabaergic Neurons

The relativistic foundations of synchrotron radiation

Electronic-structure evolution through the metal-insulator transition in RNiO3

Virtual reading of a large ancient handwritten science book

Synchrotron microradiography study on acute lung injury of mouse caused by PM2.5 aerosols

Quantization, Doppler shift and invariance of the speed of light: some didactic problems and opportunities

Real-time radiology in the microscale

Oxygen stoichiometry and the electronic structure of high-temperature superconductors

Microanalysis surface studies and photoemission properties of CsI photocathodes

Review of the development of cesium iodide photocathodes for application to large RICH detectors

Free-Electron Laser Spectroscopy of Surfaces and Interfaces

Electronic structure of a quasi-one-dimensional insulator: The molybdenum red bronze K0.33MoO3

Latest photoemission developments: Time resolution, microanalysis, order parameters

A simplified description of X-ray free-electron lasers