Calculated photoemission and x-ray emission spectra of ${\mathrm{Bi}}_2$${\mathrm{Sr}}_2$${\mathrm{CaCu}}_2$${\mathrm{O}}_8$

Angle-integrated photoemission and inverse photoemission (IP) spectra of ${\mathrm{Bi}}_2$ ${\mathrm{Sr}}_2$ ${\mathrm{CaCu}}_2$ ${\mathrm{O}}_8$ were calculated using the single-scatterer final-state approximation and densities of states obtained from a highly precise local-density band calculation. The photoemission spectra of the valence band show mainly Cu d states for high photon energies, and an increasing O p contribution with decreasing photon energies, which brings about qualitative changes in the spectra. The Bi contribution is small in all valence-band spectra, but the unoccupied Bi p states give rise to a peak in the IP spectrum. The calculated O-Kα x-ray emission spectrum (XES) is found to be narrower than might be expected from the O p density of state (DOS) alone due to the different core-level positions for the inequivalent oxygen atoms. By contrast, the calculated Cu $L_{\mathrm{III}}$ XES closely resembles the Cu d contribution to the DOS.