[en] Electron bombardment can produce surface modifications of the analysed sample. The electron beam effects on solid surfaces which have been discussed in the published literature can be classified into the following four categories: (1) heating and its consequent effects, (2) charge accumulation in insulators and its consequent effects, (3) electron stimulated adsorption (ESA), and (4) electron stimulated desorption and/or decomposition (ESD). In order to understand the physico-chemical processes which take place under electron irradiation in an Al-O system, we have carried out experiments in which, effects, such as heating, charging and gas contamination, were absent. Our results point out the role of an enhanced surface diffusion of oxygen during electron bombardment of an Al (111) sample. The importance of this phenomenon and the contribution of near-elastic scattering of the primary electrons (5 keV) to the increase of the oxidation degree observed on Al (111) are discussed, compared to the generally studied effects

[en] The results presented are only at 90 deg c.m., for the isospin state T=1 and T=0 at 310, 430, 520 and 600MeV, and for the isospin state T=1 at 635 and 670MeV. A comparison with the up-to-date phase shift analysis is given

[en] Results are reported on initial steps of plutonium alloys (stabilized in phase δ by few percents of gallium) oxidation by oxygen and water vapor. Kinetics observed with oxygen for exposures up to 500 Langmuir are presented. Results are compared with those obtained previously on pure plutonium. First results concerning water vapor adsorption are also presented. They evidence a different initial oxidation and in particular hydroxyl radicals are present in the oxide formed

[en] Elements of low atomic number can be studied by electron energy loss, secondary electron emission and Auger emission. Auger electron spectroscopy is correlated with the inner shell ionization mechanism and atomic relaxation. Electron energy loss spectrometry is related either to collective phenomena like plasmon excitations, or to the excitation of molecular electronic states. The secondary electron emission of contaminated layers results from the desexcitation of these excited states. Using these results, we characterized graphite, carbon segregated on aluminium and organic layers, by excitation of π (6 eV) and sigma (25 eV) orbitals. Molecular hydrogen, adsorbed on Pt, Ta and Al, produces a 13 eV electron energy loss. Adsorbed Oxygen on clean aluminium produces an electron energy loss at 7 eV. The cross section of sigma→sigma* orbital excitation is approximately 10² times higher than the inner K-level carbon ionization cross section. Molecular electronic level desexcitation produces a secondary electron emission at an energy equivalent to that of the electron energy loss value

[en] The understanding of the hydriding mechanism of the uranium 0.2 wt% vanadium alloy lead us to study the influence of temperature (from room temperature to about 200⁰C) and hydrogen pressure (up to 10⁵Pa) on the reaction kinetic, using ultra-high vacuum technology to minimize the effect of gaseous impurities. After a short nucleation stage, the reaction rate remains constant and takes values higher than those already reported in the literature. The hydriding process cannot be described by a single activated mechanism. A complex hydrided zone is observed under the spall front of the reaction, displaying a double-layer structure: thin hydride precipitates are detected into the underlying metal up to a few microns depth

[en] Electron bombardment can produce surface modifications of the analysed sample. The electron beam effects on solid surfaces which have been discussed in the published litterature can be classified into the following four categories: (1) heating and its consequent effects, (2) charge accumulation in insulators and its consequent effects, (3) electron stimulated adsorption (ESA), and (4) electron stimulated desorption and/or decomposition (ESD). In order to understand the physico-chemical processes which take place under electron irradiation in an Al-O system, we have carried out experiments in which effects, such as heating, charging and gas contamination, were absent. Our results point out the role of an enhanced surface diffusion of oxygen during electron bombardment of an Al (111) sample. The importance of this phenomenon and the contribution of near-elastic scattering of the primary electrons (5 keV) to the increase of the oxidation degree observed on Al (111) are discussed, compared to the generally studied effects

No abstract available

[en] Knowledge of the hydriding mechanism of the U-0.2 wt.% V alloy led us to study the influence of temperature (from room temperature to about 200⁰C) and hydrogen pressure up to 10⁵ Pa on the reaction kinetics, using ultra-high vacuum technology to minimize the effect of gaseous impurities. After a short nucleation stage, the reaction rate remains constant and takes values higher than those already reported in the literature. The hydriding process cannot be described by a single activation mechanism. A complex hydrided zone is observed under the spall front of the reaction, displaying a double-layer structure; thin hydride precipitates are detected in the underlying metal up to a depth of a few microns. (orig.)

[en] The pp analyzing power was measured simultaneously with the spin correlation parameter A_oonn(pp) using polarized proton beam and the Saclay frozen spin polarized target. In the analysis A_oono=A_ooon was assumed, as required, by TRI. The measurements at 0.88 and 1.1 GeV were carried out in the angular region 25 deg ≤ Θ_CM ≤ 60 deg. These data complete previous measurements in the angular range of Θ_CM from 45 deg to 90 deg. Between 1.3 and 2.7 GeV the measurements were performed in two overlapping angular region: 25deg ≤ Θ_CM ≤ 55 deg and 50 deg ≤ Θ_CM ≤ 95 deg. The shape of the angular distribution changes considerably with increasing energy. The evolution of the angular distribution A_oono=f(Θ) or A_oono=f(-t) is discussed in a separate contribution to this conference concerning the t-dependence of A_oono at all energies

[en] Electron bombardement can produce surface modifications of the analysed sample. The main mecanisms, responsible for such effects, are reviewed (heating, electrical effect, electron stimulated desorption, electron stimulated adsorption). Their importance are discussed in the framework of scanning electron microscopy and Auger electron spectroscopy. Results which point out the role of an enhanced diffusion of impurities during electron bombardment of silicon and aluminum samples are described. The importance of this phenomenon is discussed, compared to these generally studied