摘要
Synchrotron-radiation photoemission spectroscopy has been used to search for differences in the electronic structure of superconducting and non-superconducting members of this novel family of compounds. We find no evidence of a Fermi edge for non-superconducting compounds, which is present for superconducting compounds. This result confirms that the absence of a Fermi edge in the early 1-2-3 photoemission spectra is an extrinsic effect. Studies of the resonating copper satellite did not produce evidence of Cu 1+ states. © 1989.