Understanding core-level decay processes in the high-temperature superconductors

A highly correlated $\mathrm{Cu}{\mathrm{O}}_n$ cluster model is utilized to interpret the core-level Auger and x-ray emission decay spectra for $\mathrm{Y}{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-x}$ and CuO. The evidence indicates that the initial core-level shakeup states relax to states of the same symmetry before the core-level decay, provided they have a shakeup excitation energy much greater than the core-level width.