Le Journal de Physique Colloques 12/1986; 47(C-8). DOI: 10.1051/jphyscol:1986820


Nous présentons un spectromètre simple, spécialement construit pour les mesures de ReflEXAFS. Il utilise un tube de rayons-X conventionnel associé à un miroir parabolique. Un monochromateur à deux cristaux (LiF) permet d'obtenir une résolution de 8,5 eV à 8 keV. Le faisceau incident est monitoré par un compteur proportionnel et le faisceau réfléchi est mesuré par un compteur à scintillation (NaI) qui permet d'éliminer les harmoniques par discrimination d'énergie. Le spectromètre est utilisable de 7 à 18 keV. Les spectres relatifs à la surface d'un échantillon de nickel avant et après oxydation thermique sont présentés. A simple spectrometer using a conventional X-ray generator has been constructed for ReflEXAFS measurements at glancing angle. The X-ray source is a sealed X-ray tube with a parabolic mirror. A monochromator with two flat LiF crystals is used. The energy resolution amounts to 8.5 eV at 8 keV. A proportional counter monitors the incident X-ray intensity and a NaI scintillation detector measures the intensity of the reflected beam. This system is free from fluctuations of the incident X-ray intensity and harmonics can be rejected with the energy discrimination. The range of energy is 7 to 18 keV. The ReflEXAFS spectra related to the surface of a nickel sample and a thermally oxided nickel sample are presented.

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    ABSTRACT: The final stages of the spreading of nonvolatile polymer droplets on smooth solid surfaces have been studied by the technique of x-ray reflectivity. Clean and silanated silicon wafers which are substrates corresponding, respectively, to high and low positive spreading parameters S, have been investigated. In both cases the equilibrium state has been characterized and compared with recent theoretical predictions. We show that for a high S value, the final state cannot be viewed as a dense homogeneous film, whereas for a low S value, the theoretical "pancake" picture could be appropriate.
    EPL (Europhysics Letters) 07/2007; 6(5):431. DOI:10.1209/0295-5075/6/5/010 · 2.10 Impact Factor

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