X-ray absorption spectroscopy studies of high- T c superconductors

X-ray absorption spectroscopy measurements on rare-earth (R) and Ba sites in the new superconducting oxides and in binary rare-earth oxides are discussed. All of the near-edge spectra appear to manifest a continuum resonance feature whose energy is quantitatively well correlated with the R–O and Ba–O bond lengths. Evidence supporting a second such feature related to the R/Ba interatomic distance is also presented. Finally, simultaneous consideration of both of these features appears consistent with the inverse square-law expectation for the interatomic distance dependence of the energies of these spectra features.