X-ray spectra and electronic structure of high Tc superconductors

At the present moment spectral investigations have been done for two types of ceramic oxidic HTSC: La2-xSrxCuO4 and YBa2Cu3O7. These investigations had the following purposes: 1. Thorough investigation of energy band structure and distribution of partial densities of states of HTSC in a wide energy interval as well as experimental testing of band structure calculations. 2. Analysis of electron structure of HTSC on the surface and within the bulk. 3. Determination of the oxidation degree of constituent atoms in HTSC and, first of all, the presence of Cu3+ ions, EXAFS and XANES studies of the short order in HTSC. Before discussing the obtained results the authors review briefly what information one can be obtained from X-ray and photoelectron spectra