Electronic elementary excitation in the far UV‐spectral region core level exciton and core hole polarization

Abstract

AbstractAn electronic elementary excitation of a crystal is considered which might be of interest for the interpretation of the structures of far UV reflectance and photoemission spectra associated with transitions from core levels into conduction bands. The primarily generated strongly localized core hole polarizes the electronic subsystem. The polarization is accompanied by the generation of a secondary less strongly localized hole to which the conduction band electron is bound. The excitation energy is lowered by the polarization energy of the core hole as compared to the excitation energy of an exciton. The static polarization energy and polarization charge density are calculated for a core hole of the Ga atom by means of the Thomas‐Fermi approximation. Polarization energies of several eV are obtained which decrease nearly inverse proportionally with hole radius. The influence of the polarization energy on UV reflectance and photoemission spectra is discussed. It is concluded that the core hole polarization energy contributes to the difference between band distances obtained by reflectance and photoemission measurements, supposed the dispersion of the polarization energy is important.