Double-Electron Excitations in L-edges X-ray-Absorption Spectra of W, Ir and Cs Oxide Compounds

Very strong double-electron excitations have been observed for the first time in the W, Ir L 3-edge and Cs L 1,2,3-edges X-ray-absorption spectra of tungsten and iridium oxide thin films and cesium oxide containing glasses. They are expressed as peaks with a width of several electron-volts located at the absorption background above the edge. The positions of these features are in good agreement with atomic calculations in the Z+1 approximation. They can be attributed to the transitions 2p4d → 5d5d for the L 2,3-edges and 2s4d → 6p5d for the L 1-edge with the dipole selection rules for the angular and total angular momentum ΔL=±1, ΔJ=0,±1.

Surfactant Association: Recent Theoretical and Experimental Developments

A theoretical model describing the association of ionic surfactants into rod-shaped micelles is combined with an approximate formula for the viscosity increase induced by rod-shaped aggregates. It is shown that most of the thermodynamic parameters of the association model can be obtained from viscosity measurements. The approach is applied to micellar solutions of hexadecylpyridinium salts. The pronounced effect of counter-ion concentration on the growth of rod-shaped micelles can be attributed to a slightly higher degree of counter-ion association in the cylindrical part than in the end portions. An attempt is made to explain the finding that the degree of counter-ion association is virtua…

Local Environment of Co2+ Ions in β″-Alumina Crystals

XAFS STUDIES OF OCTAHEDRAL AMORPHOUS OXIDES

The relationships between the structures of octahedral and tetrahedral amorphous oxides, studied by XAFS spectroscopy, are considered. It was found that a-WO3, a-MoO3, a-V2O5 thin films and glasses have strongly distorted, but well defined, oxygen octahedra, which are joined by vertices (a-WO3, a-MoO3) or by vertices and edges (a-V2O5), and form a random network. At the same time, a-IrO2 and a-NiO have less distorted oxygen octahedra, which form the rutile type and rock salt type nanocrystalline structures. The variation of the structure with the change of the metal valence is considered and the possibility of small radius polaron detection by XAFS is discussed.