Resonant X-Ray Emission Spectroscopy in La2CuO4and CuO

Resonant X-ray emission spectra (RXES) due to the Cu 3 d →2 p electronic transition under the Cu 2 p →3 d resonant excitation in La 2 CuO 4 and CuO are theoretically investigated. It is predicted that, with this spectroscopy, one can obtain direct information on the difference of the a 1 g states between La 2 CuO 4 and CuO, which is a characteristic difference in the electronic states between the so-called p -type high- T c superconductors and CuO, as has been shown in our theoretical analysis of the Cu 2 p -XES under the excitation of a Cu 2 p electron to a high energy continuum. Strong polarization dependence of the Cu 2 p -RXES enables us to determine the electronic structure. It is pointed out that the 2 p -RXES is a powerful probe in the study of the 3 d electronic states in transition metal compounds subjected to the crystal field, anisotropic hybridization and 3d multiplet couplings.