Photoemission study of the final band in Ag(111)

For direct transitions in angle-resolved photoemission from a single crystal, the final electronic states inside the crystal can be approximately described by a free-electron-like band for energies higher than approximately=30 eV above the Fermi level. The authors report a determination of the dispersion relation for this band in Ag along the (111) direction over a wide photon energy range (40-180 eV), from which the inner potential (average electrostatic potential in the solid within the Hartree approximation) and the energy-dependent electron effective mass are deduced. The effective mass is found to increase from approximately 1.00 m at 54 eV to 1.08 m at 149 eV above the Fermi level (m is the free electron mass). This result is compared with existing many-body model calculations. The present study is also relevant to the problem of surface state resonance in this system discussed previously.