X-ray absorption around the oxygen K and the Cu ${\mathit{L}}_{\mathrm{III}}$ edge of ${\mathrm{Tl}}_2$${\mathrm{Ba}}_2$${\mathrm{Ca}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{10\mathrm{-}\mathrm{\delta }}$ high-${\mathit{T}}_{\mathit{c}}$ superconductors with different oxygen content δ, was measured. Near the O 1s edge, three distinct pre-edge peaks with maxima at 528.3, 529.4, and 530.6 eV, respectively, are revealed. They are ascribed to core-level excitations of oxygen 1s electrons to empty states which have predominantly oxygen 2p character, located in ${\mathrm{CuO}}_2$, BaO, and TlO planes, respectively. A strong dependence of ${\mathit{T}}_{\mathit{c}}$ on oxygen hole concentration at O(1) and O(1)’ sites in the ${\mathrm{CuO}}_2$ layer is found. Near the Cu 2${\mathit{p}}_{3/2}$ edge, two main peaks are observed. The peak at 931.2 eV is ascribed to a 2p3${\mathit{d}}^{10}$ final state. This implies a predominately ${\mathrm{Cu}}^{2+}$ ground state which has mainly 3${\mathit{d}}^9$ character. The peak at 933 eV is ascribed to a 2p3${\mathit{d}}^{10}$L final state. This peak shows an intensity increase with ${\mathit{T}}_{\mathit{c}}$, i.e., with ligand hole concentration, and is believed to arise from a formally ${\mathrm{Cu}}^{3+}$ ground state which has mainly 3${\mathit{d}}^9$L character. No evidence of a monovalent (${\mathrm{Cu}}^{1+}$) 3${\mathit{d}}^{10}$ ground state was found.

• Received 28 May 1991

DOI:https://doi.org/10.1103/PhysRevB.45.10051