Angle-resolved photoemission study of the electronic structure of beryllium: Bulk band dispersions and many-electron effects

Angle-resolved photoemission spectra from Be(0001) in the photon energy range 10-120 eV are presented and discussed. The band structure along $\Delta$ is determined and compared with our calculation using an ab initio self-consistent pseudopotential method in the local-density formalism. The occupied bandwidth, characterized by the ${\Gamma }_1^{+}$ symmetry point energy, is found to be 11.1±0.1 eV, which is in excellent agreement with the calculated value of 11.16 eV. The most shallow occupied symmetry point on $\Delta$, ${\Gamma }_3^{+}$, is found at 4.8±0.1 eV, while the calculated value is 4.32 eV. The lowest-energy unoccupied band is in good agreement with the calculation with the exception of some extra structure near the plasmon threshold. This extra structure is associated with interaction between the excited electron and plasmons. The peak widths for photon energies below 33 eV are in reasonable agreement with widths predicted for hole lifetimes in the homogeneous electron gas.