Copper-related information from the oxygen1sresonant x-ray emission in low-dimensional cuprates

Incident- and outgoing-photon polarization dependences of O $1s$ x-ray emission spectrum (XES) in low-dimensional cuprate systems are investigated through model calculations using finite-size cluster models which include several copper sites. It is shown that the O $1s$ resonant XES provides information on the Cu-related excitations such as the Cu $\mathrm{dd}$ excitations and the charge-transfer (CT) excitations, in addition to the oxygen proper excitations. In particular, the lowest-energy CT between the neighboring ${\mathrm{CuO}}_4$ plaquettes accompanies Zhang-Rice singlet formation. Even the Cu $3d$ spin flip can be observed as an inelastic scattering peak. Thus the O $1s$ resonant XES can be a nice tool to investigate metal-ion-related excitations in oxides.