Observed trends in the x-ray photoelectron and Auger spectra of high-temperature superconductors

X-ray photoelectron spectra and Auger-electron spectra are reported for ${\mathrm{La}}_2$Cu${\mathrm{O}}_4$ and Y${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$ in the tetrahedral and orthorhombic crystal structures; they are compared to previously reported data for Cu, ${\mathrm{Cu}}_2$O, and CuO. These data reveal large electron-electron interaction effects. The magnitude of these interaction effects correlate with the transition temperatures of the superconducting oxides.