XAFS Studies and Chemical Shifts of Thallium LIII X-Ray Absorption Edges in Some of its Model Compounds and Superconducting Oxides

摘要

The position, shape and XAFS of X-ray absorption discontinuities have been used to deduce structural and chemical bonding information on model compounds of thallium and its superconducting oxides. It is observed that the LIII absorption edges of thallium shift towards the high energy side with respect to the position of the discontinuity in thallic oxide in all the systems investigated. The valence state of the metal ion in these compounds and electronegativity were compared in relation to chemical shifts. On the basis of our X-ray chemical shift data we have determined the valence state of the thallium ion in its superconducting oxides.