Polarization dependence of core-level X-ray photoemission spectra in anisotropic solids

A theoretical prediction of polarization-dependent XPS in anisotropic solids is given, with Cu 2p- and 3p- XPS in La₂CuO₄ as an example. The XPS due to the dipole p → s transition is shown to exhibit an appreciable polarization dependence, which originates from the multiplet-coupling between the core hole and anisotropic Cu 3d electrons. The polarization-dependent 3p → εs process can be made to dominate an almost polarization-independent 3p → εd process by tuning the incident photon energy to the Cooper minimum of the 3p → εp transition at about 22eV above the threshold.