Nonquasiparticle structure in the photoemission spectra from the Be(0001) surface and determination of the electron self energy

Complex structure in photoemission spectra of Be(0001) surface states near the Fermi energy is observed and explained as the effect of strong electron-phonon coupling. The weak momentum dependence of the electron-phonon contribution to the electron self energy {Σ} is exploited to determine {Σ} by direct inversion of the spectra.