X-ray absorption study of the O 2p hole concentration dependence on O stoichiometry in YBa2Cu3Ox

Abstract
A detailed x-ray absorption study of the oxygen K edge of YBa2Cu3Ox is presented. A preedge peak is observed for all samples with x6.4 which we argue to be due to holes in the O 2p band. By comparison to LixNi1xO the x dependence of the number O 2p holes in YBa2Cu3Ox is determined.