X-ray absorption coefficient of rubidium in the K-edge region

A high-resolution absorption spectrum of rubidium vapor in the vicinity of K edge is converted to absolute absorption coefficient by a set of measurements on a RbNO3 solution. Specific problems arising in absolute absorption measurements with synchrotron light and with conventional X-ray sources are discussed

Comparison of AES and EXAFS analysis of a thin CuxAly\mathrm{Cu_x Al_y} layer on Al substrate

A layer of copper with the thickness of 0.5 μm was sputter deposited on a commercially available aluminum foil with the thickness of 30 μm. The composition of elements within the coating was determined with Auger Electron Spectroscopy (AES) depth profiling, while the structure was determined with Extended X-Ray Absorption Fine Structure (EXAFS) and X-Ray Diffraction (XRD). Samples were exposed to a low pressure weakly ionized hydrogen plasma with a high H density. Due to extensive recombination of hydrogen atoms on copper surface the samples were heated to 300°C so that diffusion of elements within the coating took place. After the plasma treatment, the samples were analyzed with AES and EXAFS again. The AES depth profiles showed that a rather uniform coating consisting of 66 at.% of Al and 33 at% of Cu was formed. Comparison of the shape of the main Auger LMM peak of pure Cu and that of Cux Aly coating showed a substantial difference. The XRD analysis showed the presence of crystalline CuAl2 phase. However, the EXAFS analysis showed that the coating was not a stoichiometric CuAl2, but rather the Cu\Al solid solution rich in CuAl2

Separation of weak EXAFS signal from atomic background in Br and Rb samples

In EXAFS analysis of Rb-doped silicate glasses and of cetyl- trimethylammonium bromide (CTAB) adsorbed on carbon black, the spline approximation of the atomic background is inadequate. Instead, a residuum obtained from absorption spectra of Rb and Br ions in aqueous solution after removal of the structural signal is used. Another iteration cycle whereby the residuum from one sample in the atom-ion pair is used in analysis of the other one, gives satisfactory convergence. In this way, definite FEFF models of Rb glass and CTAB are constructed, and a better approximation for atomic absorption obtained as residual