[en] The tungsten-carbon multilayer system has been studied using x-ray scattering techniques as a function of multilayer period and annealing. Grazing incidence x-ray scattering shows that interatomic arrangements in the W-rich layers depend strongly on their proximity to the interface with the C-rich layers. Amorphous interface layers are stabilized by intermixing of W and C during deposition into local structures similar to those in the tungsten carbides. Further intermixing and structural relaxation in the amorphous state occurs on annealing these structures. This interatomic structural interpretation is consistent with trends in the observed x-ray optical properties

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[en] An in-line polarimeter including phase retarder and linear polarizer was designed and commissioned on undulator beamline 7.0 for the purpose of converting linear to circular polarization for experiments downstream. In commissioning studies, Mo/Si multilayers at 95 eV were used both as the upstream, freestanding phase retarder and the downstream linear polarized. The polarization properties of the phase retarder were characterized by direct polarimetry and by collecting MCD spectra in photoemission from Gd and other magnetic surfaces. The resonant birefringence of transmission multilayers results from differing distributions of s- and p-component wave fields in the multilayer when operating near a structural (Bragg) interference condition. The resulting phase retardation is especially strong when the interference is at or near the Brewster angle, which is roughly 45 degrees in the EUV and soft x-ray ranges

[en] Uranium materials display a wide range of thermal, electrical and magnetic properties, often exotic. For more than a decade there have been efforts to use photoemission spectroscopy to develop a systematic and unified understanding of the 5f electron states giving rise to this behavior. These efforts have been hampered by a paucity of systems where changes in transport properties are accompanied by substantial spectral changes, so as to allow an attempt to correlate the two kinds of properties within some model. The authors have made resonant photoemission measurements to extract the 5f spectral weight in three systems which show varying degrees of promise of permitting such an attempt, Y_1-xU_xPd₃, U(Pd_xPt_1-x)₃ and U(Pd_xCu_1-x)₅. They have also measured U 4f core level spectra. The 4f spectra can be modeled with some success by the impurity Anderson model (IAM), and the 5f spectra are currently being analyzed in that framework. The IAM characterizes the 5f-electrons of a single site by an f binding energy ε_f, an f Coulomb interaction and a hybridization V to conduction electrons. Latent in the model are the phenomena of 5f mixed valence and the Kondo effect

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[en] The pristine state and soft X-ray induced decomposition of two aromatic amino acids, viz. phenylalanine and tyrosine, have been studied by means of XPS and NEXAFS. The spectroscopic data on the radiation decomposition have been supplemented by a mass-spectral analysis of desorbed species in the residual gas. Despite very similar chemical structures, the two amino acids show a drastically different behavior towards ionizing radiation: phenylalanine degrades very quickly whereas tyrosine shows a prominent stability against radiation damage. Reasons for this difference are discussed in relation to radical-mediated reactions responsible for the decomposition

[en] Investigation of the initial oxidation and interface formation of cubic silicon carbide for the silicon rich β-SiC(100) 3?2 surface reconstruction by high resolution synchrotron radiation-based soft x-ray photoemission spectroscopy is described. The surface is exposed to low doses of molecular oxygen ranging from 1 up to 10 000 L, at surface temperatures from 25 to 500 deg C. Significant formation of SiO₂ is found for the surface at room temperature, with the rate of oxidation increasing with temperature. Valence band data and Si 2p core level spectra show that even at low exposures, significant oxidation is taking place, with a surface reactivity to oxygen much larger than for silicon surfaces. The oxidation products, which are grown at very low temperatures (≤ 500 ^oC) include SiO₂ as a dominant feature but also substoichiometric oxides Si⁺¹, Si⁺², Si⁺³, and significant amounts of mixed oxide products involving C atoms (Si-O-C)