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Using Ni(AcO)2·4H2O as a catalytic precursor and PhSiH3, a simple and efficient catalytic system was synthesized for reducing FAs with high conversion under relatively mild conditions.

The nanocrystalline MnxFe3−xO4 (x=0, 1.18, 1.56, and 1.9) spinel ferrite thin films were investigated by means of the x-ray absorption spectroscopy and x-ray magnetic circular dichroism at the Mn and Fe L2,3 edges. The cationic distributions of thin spinel ferrite films for x=1.18 and 1.56 were determined using a crystal field atomic multiplets scheme for arbitrary symmetry. The results are compared with the distribution of cations obtained from the differential thermogravimetry analysis of fine powders of corresponding compositions.

A beamline using a Low Energy Monochromator Optimized at Normal incidence (LEMON) has been designed to match the bending magnet radiation characteristics of ELETTRA, the third generation source in Trieste. The beamline will use 4×6 mrad2 of the emitted radiation cone and will be equipped with two interchangeable monochromators: one Normal Incidence Monchromator (NIM) and one Toroidal Grating Monochromator (TGM), both sharing the same focusing optics, entrance and exit slits. The expected performance of the beamline will be a photon energy range from 5 to 200 eV, a resolving power ranging from 100 000 to 500 and a photon flux up to 1×1011 ph/s/0.1BW on the sample.

Resonant photoemission synchrotron radiation measurements of Fe 3 d states performed on Cd 1− x Fe x Se and Zn 1− x Fe x Se samples, with several x concentrations, are reported. Three Fe-related features have been identified: a weak one located above the top of the host material valence bands and the other two extending over the first 4 eV. The influence of the Se MVV Auger transition is analyzed. The observed features have been discussed in terms of a ligand field approach and assigned to the crystal field levels derived from the Fe 2+ ion final state configurations.

(1999). The elettra circular polarization beamline and electromagnetic elliptical wiggler insertion device. Synchrotron Radiation News: Vol. 12, No. 4, pp. 34-38.

The optical properties of the semiconducting compounds (Me = Ti, V, Cr, Mn, Fe, Co, and Ni) crystallizing in the zinc-blende structure have been investigated. Reflectivity spectra of these materials have been taken at room and liquid nitrogen temperatures. The measurements have been performed in the 4 - 25 eV energy range using synchrotron radiation from the ADONE storage ring in Frascati. Comparisons between the reflectivity spectra of the ternary systems and those of the host crystal ZnSe have been made, and models explaining the influence of the transition metal ions on the electronic structure of the host crystal ZnSe have been discussed.

The described synchrotron radiation beam line, based on a double monochromator with different incidence angles, has been devised to ally in a short length the working possibilities of both vacuum ultraviolet and soft X-ray monochromators as well as to preserve the degree of circular polarization of the radiation emitted by the source. The design philosophy and the predicted performances of the diffraction and the focusing systems are described and the heat load on the beam line optical elements is discussed. Some practical details concerning the beam line, now under construction, are presented.

The absorption coefficient of several diluted magnetic semiconductors was measured below the fundamental absorption edge of the pure host compound at room temperature using the photoacoustic technique. Several absorption bands have been detected and assigned to electronic transitions between the crystal field split 3d levels of the transition metal ion. In addition, weak absorption thresholds have been observed and assigned to the ionization of the transition metal d states. An energy level diagram of the d states has been discussed.The absorption coefficient of several diluted magnetic semiconductors was measured below the fundamental absorption edge of the pure host compound at room temperature using the photoacoustic technique. Several absorption bands have been detected and assigned to electronic transitions between the crystal field split 3d levels of the transition metal ion. In addition, weak absorption thresholds have been observed and assigned to the ionization of the transition metal d states. An energy level diagram of the d states has been discussed.

The Fe related density of states of Cd 1−x Fe x Se has been investigated by means of synchrotron radiation photoemission. Energy distribution curves of the ternary compound Cd 1−x Fe x Se are presented and compared with those of the binary compound CdSe. Two Fe related structures are easily observed for all photon energies investigated (30 eV – 60 eV), whereas a third structure could be found only in the resonant photoemission region. An analysis of the costant initial state spectra suggests an atomic like interpretation of the experimental observations.

Photoluminescence spectra of the perovskite-like KMgF 3 doped with both Ag + and OH − impurities, measured in the energy range 3–7 eV under excitation at 9.2 eV with Synchrotron light, reveal an energy transfer process from Ag + to OH − ions.

In this paper we present partial densities of states for spin-polarized antiferromagnetic phase of Zn0.5 Co0.5 Se as well as schematic layouts of the bands, obtained using the ab initio self-consistent semi-relativistic linear muffin tin orbital method. We also present, from theoretical point of view, the analysis of influence of the transition metal cobalt on the electronic structure of a pure ZnSe.

We have studied the oxidation of quaternary InGaAsP materials by NO2, using Auger electron spectroscopy for both elemental and chemical analysis of the surface. We report that NO2 induces a preferential oxidation, forming oxides of Ga, In, and P. The As remains unoxidized. From Ar+ ion milling we find that the oxide layers are fairly thin (less than 10 A), even at high exposures (greater than 1000 L) of NO2, where we obtain a saturation coverage of approximately 0.3 ML (monolayers). We have also measured electron energy loss spectra (EELS) and observe the disappearance of the surface plasmon loss feature upon oxide formation.

In this paper we present a comprehensive study of the tetrahedral semiconductor ZnSe crystallizing in the zincblende structure. The electronic structure of ZnSe has been determined first using the ab initio self-consistent linear muffin-tin orbital method with a local-density form of the exchange-correlation functional. Then it has been adjusted to reproduce the experimental energy positions of the Zn 3d bands and of the optical gap. The adjusted electronic structure, densities of states and interband optical properties are presented and compared with previous calculations. Good agreement with experimental photoemission and bremsstrahlung isochromat measurements was found after including an energy-dependent lifetime broadening. We measured the reflectivity of ZnSe with high resolution from 4 to 30 eV and the high-energy region of the spectra has been interpreted on the basis of the present calculation.

The Sn on the Si(100) system constitutes an epitaxial interface of Group-IV elements. Its phase diagram presents several surface reconstructions, whose structure depends on the Sn adlayer coverage and the annealing temperature. The interfaces of Sn grown at room temperature on Si(100)(2 × 1) and the superstructures obtained after annealing have been studied by means of inverse photoemission (IPES), and Auger and LEED spectroscopy, to characterize the electronic empty states of the different overlayer phases and relate them with other electronic properties. Sn/Si(100) systems, both at room temperature deposition and after thermal treatment, present the onset of a metallic overlayer for tin coverages above 1 ML. For the interfaces grown at room temperature the IPES spectra with Sn thicknesses below 1 ML show a peak at about 1.0 eV above the Fermi level. At the E F level no emission is present. The IPES spectra of Sn/Si(100) after annealing clearly show that the empty states evolution can be related to the kind of reconstruction observed by LEED. These results indicate the formation of interfaces with peculiar properties. In particular in the Sn/Si(100)c(8 × 4) system the phase is semiconducting and the gap is reduced; a new prominent state appears at 1.1 eV above E F . The role played at the interface by the Sn-Sn dimers, related to the dimensionality, is discussed.

We have measured at room temperature the photoacoustic spectra of Cd1−x Fe x Te(0

This paper describes the conceptual design of a bending magnet synchrotron radiation beamline based on a double-incidence plane grating monochromator. One of the bending magnets of the ELETTRA storage ring has been considered as a reference source assuming a beam energy of 1.5 GeV and a stored current of 400 mA. The monochromator covers the energy range from 6 eV to 200 eV, with three gratings (one in normal incidence and two in grazing incidence condition) achieving a resolving power of the order of 10 000 and delivering a photon flux of approximately 10 13 [photons/s/1% bandwidth]. The image dimensions onto the sample are 0.5 × 1 mm.

The design of a beamline, covering the energy range from 5 to 200 eV, based on a double incidence spherical gratings monochromator designed for ELETTRA bending magnet radiation is described. The monochromator consists of two interchangeable sets of gratings working one at normal incidence and the other at grazing incidence, to cover the entire spectral interval. The photon energy range of interest is covered with five gratings (two at normal and three at grazing incidence) achieving a resolving power of the order of 10000 and a photon flux approximately 1012 (photons/s/0.1% bandwidth/mm2) at the sample position.

This report is an attempt to assess the validity of the binary collisions approximation by comparing TRIM and molecular dynamics in calculating the backscattering of carbon ions off a graphite surface. The TRIM calculations were performed for an amorphous target with smooth surface. In the molecular dynamics calculations, a recently available semi-empirical many body potential by Tersoff was used. The calculations were made for a perfect crystal at zero temperature, consisting of 1342 atoms in five layers. The probability of reflection was calculated as a function of energy and angle of incidence of the projectile. Compared with the binary collisions calculations, molecular dynamics predicts a significantly higher backscattering probability. For instance, at normal incidence TRIM shows less than one per cent reflection in the whole energy range up to 1 keV, whereas in molecular dynamics the reflection yield peaks around 20 eV with more than 40% reflection. The case of a head-on collision with a surface at normal incidence is discussed in detail.

A new chemoenzymatic procedure to obtain pure enantiomeric 2-arylpropionic acids is described. The one pot synthesis of (±)-2-arylpropionic acids is carried out by addition of dichlorocarbene to the O bond of arylmethylketones and hydrogenolysis of the addition product. The racemic mixture is resolved by enantiospecific hydrolysis of the racemic ethyl esters using native lipase from Candida rugosa . The good yields, the accessibility of the starting arylmethylketones and the stereospecificity of the enzymatic hydrolysis make the process interesting in order to obtain the same non steroidal antiinflammatory drugs such as Ibuprofen or Naproxen.

We report on inverse photoemission studies (IPES) obtained on freshly pealed InSe. The spectra have been taken with a Geiger-Muller-type detector and a resulting resolution of about 0.4 eV. The electron beam was not collimated thus leading to angle-integrated spectra. The data show peaks at 2.3, 5.1 and a broad feature at 7.5 eV above E F . The results are compared with previous theoretical calculations.

During 1989, following a brief all carbon phase, JET was operated with an evaporated beryllium film on all the plasma facing surfaces and then, in a third phase, with bulk beryllium used for the belt limiters and one set of antenna protection tiles. Subsequent analysis of wall components and long term samples (LTS) using Beta Backscatter and Ion Beam Analysis has been conducted to determine the condition of the First Wall and its deuterium inventory after beryllium operation. Ex-situ analysis of components where deposition occurs during operation shows mixed carbon and beryllium layers with an approximate ratio 1:1 and some localised higher Z components. The deuterium inventory situation is littled changed by the introduction of beryllium. Similar surface levels of deuterium, ~1 × 1022 atoms m−2, have been seen for both carbon and beryllium belt limiter tiles.

Collector probes were exposed to the first evaporation of beryllium in the JET vessel and to the first few plasma shots thereafter. The probes were removed under ultrahigh vacuum to an on-line analysis facility before, during and after the sequence of pulses. The amount of Be deposited during evaporation, and the amount of impurity species collected during the plasma pulses, were thus determined. Carbon was observed from the first pulse, despite the coverage of the limiters with Be, and the co-deposition with Be led to carbide formation. Oxygen was gettered very effectively by the evaporated Be layers well away from the plasma, but less efficiently where plasma deposition occurred.

En este trabajo se realiza una evaluación de los datos reportados en la literatura de la adsorción de mezclas binarias de benceno-ciclohexano y benceno-n-alcanos en sílica gel y de los valores obtenidos en esta investigación del sistema benceno-ciclohexano-sílica gel con la finalidad de determinar el área superficial del adsorbente. Se ha encontrado que el valor del área superficial de las muestras de sílica en la adsorción de soluciones de benceno-ciclohexano está en el orden de 22% por defecto, con respecto al área superficial obtenida por adsorción de nitrógeno gaseoso, y de 9% por exceso, en el caso de la adsorción de soluciones de benceno con n-alcanos, This work embodies the results of an evaluation of liquid phase adsorption data reported in literature of binary mixtures of benzene with cyclohexane, benzene with n-alkanes in sílica gel and values obtained in this investigation in the benzene-cyclohexane-sílica gel system with the purpose of determining the surface areas of the adsorbents The surface areas per gram of adsorbent, determined from liquid adsorption data of solutions of benzene with cyclohexane are 22 per cent smaller than those obtained from nitrogen gas adsorption and 9 per cent greater in the case of solutions of benzene with n-alkanes.

This work embodies the results of an evaluation of liquid phase adsorption data reported in literature of binary mixtures of benzene with cyclohexane, benzene with n-alkanes in sílica gel and values obtained in this investigation in the benzene-cyclohexane-sílica gel system with the purpose of determining the surface areas of the adsorbents The surface areas per gram of adsorbent, determined from liquid adsorption data of solutions of benzene with cyclohexane are 22 per cent smaller than those obtained from nitrogen gas adsorption and 9 per cent greater in the case of solutions of benzene with n-alkanes. En este trabajo se realiza una evaluación de los datos reportados en la literatura de la adsorción de mezclas binarias de benceno-ciclohexano y benceno-n-alcanos en sílica gel y de los valores obtenidos en esta investigación del sistema benceno-ciclohexano-sílica gel con la finalidad de determinar el área superficial del adsorbente. Se ha encontrado que el valor del área superficial de las muestras de sílica en la adsorción de soluciones de benceno-ciclohexano está en el orden de 22% por defecto, con respecto al área superficial obtenida por adsorción de nitrógeno gaseoso, y de 9% por exceso, en el caso de la adsorción de soluciones de benceno con n-alcanos

The experimental results of photoacoustic measurements of several transition metals in wide gap II-VI semiconductors performed at room temperature are presented. The observed intra-atomic as well as photoionization transitions in two different host matrix are assigned and discussed.

A dedicated beamline with a broad energy range of photons and with high flux and a high degree of circular polarization has been designed for the ELETTRA storage ring. The beamline exploits the circularly polarized radiation produced by an electromagnetic elliptical wiggler and cover the (5–1200) eV photon energy range using a double‐incidence spherical grating monochromator.

The possibility of using reflection multilayers as wide band circular polarizers in the VUV and soft X-ray region (5-300 eV) is theoretically considered by means of a realistic model. An optimization method for the phase-shifting performances of such multilayer polarizers is proposed and the performances of different multilayers working in several energy windows are discussed.

We have measured at room temperature the photoacoustic spectra of Cd1-xFexTe (0

The phaseshifting properties of multilayer transmission filters in the XUV region are examined. The possibility of changing the polarization state of electromagnetic radiation from linear to circular by means of such devices is carefully considered using a realistic model and proper optimization criteria. The performances of different transmission multilayers in some energy windows are presented.

Surface probes have been exposed at JET with all-carbon walls, when beryllium was evaporated onto graphite limiters, and with beryllium limiters. The aims have been to study the impurity content in the scrape-off, erosion and deposition, and the pumping of deuterium by codeposition with carbon and beryllium. Thermally activated erosion makes it difficult to study time resolved erosion close to the LCFS. In the all-carbon machine, the carbon density in the outboard scrapeoff between the belts was estimated to ~ 20% of the deuterium. With a fresh Be coating on the limiters, carbon in the SOL was initially suppressed, but increased from discharge to discharge. The D/C ratio in codeposition layers was three times larger with Be-evaporation than in all-carbon conditions. Edge profiles determined from impurity deposition became flatter during RF heating and current ramp down.

Sputtering of UF 4 by electronic excitation with fast ions has unexpectedly shown very high sputtering yields and an energy distribution of sputtered particles which decays rapidly on the high energy side. A description of the data in terms of a “thermalised ion explosion spike” has been proposed. The present discussion uses the same data to support a radically different model in which electronic relaxation generates uranium halide dimers on the surface of the UF 4 as the result of a normal energy cascade. Electronically produced sputtering of these dimers can account for the very high sputtering yields and the model accurately describes the observed energy distribution of emitted material.

A combination of angular distribution and energy spectra of sputtered atoms from amorphous UO2 material bombarded with Ar+ ions in the range 5-20 keV has given some insight into the relative importance of bulk and surface binding potentials in this material. For the energy spectra the data are well described over some 4 decades in energy by a theoretical model which includes both E B and E s terms. The surface binding term is constant at ∼1.4 eV throughout the range of argon ion energies but the effective bulk energy term EB varies from ∼3 to ∼30 eV.