Abstract
The role that occupied $d$ bands play in the inelastic lifetime of bulk and surface states in Ag is investigated from the knowledge of the quasiparticle self-energy. In the case of bulk electrons, $sp$ bands are taken to be free-electron like. For surface states, the surface band structure of $sp$ states is described with the use of a realistic one-dimensional hamiltonian. The presence of occupied $d$ states is considered in both cases by introducing a polarizable background. We obtain inelastic lifetimes of bulk electrons that are in good agreement with first-principles band-structure calculations. Our surface-state lifetime calculations indicate that the agreement with measured lifetimes of both crystal-induced and image-potential induced surface states on Ag(100) and Ag(111) is considerably improved when the screening of $d$ electrons is taken into account.
Highlights
Our surface-state lifetime calculations indicate that the agreement with measured lifetimes of both crystal-induced and image-potential-induced surface states on Ag100͒ and Ag111͒ is considerably improved when the screening of d electrons is taken into account
Our surface-state lifetime calculations indicate that the agreement with measured lifetimes of both the nϭ0 crystal-induced and the lowestlying nϭ1 image-potential induced surface states on silver surfaces is considerably improved when the screening of d electrons is taken into account
The impact of d-electron screening on the dynamics of the Shockley surface hole on Ag111͒ is entirely due to the reduction of the screened interaction between the excited hole and the Fermi sea
Summary
Electron scattering in the bulk and at the surface of solid materials has attracted great interest, as the Coulomb interaction between excited electrons and the remaining electrons of the solid is fundamental in many physical and chemical phenomena, such as charge transfer or electronically induced adsorbate reactions at surfaces. A basic quantity in photoelectron spectroscopy and quantitative surface analysis is the quasiparticle lifetime, which sets the duration of the excitation and combined with the velocity yields the mean free path of the excited state. Image states are Rydberg-like states trapped in the image-potential well outside the surface of a solid with a projected band gap near the vacuum level. Theoretical work based on many-body calculations of the electron self-energy predicted both Shockley and image-state lifetimes that are, in the case of Cu and other metal surfaces, in good agreement with experiment.. We report calculations of the inelastic lifetime of both bulk and surface states in Ag, as obtained from the knowledge of the complex quasiparticle self-energy by combining the dynamics of sp valence electrons with a simplified description of the occupied d bands. We present the results of calculations of the lifetime of bulk excited electrons with energies below the vacuum level, the first three image states on Ag100͒, and both the Shockley and first image state on Ag111͒. Atomic units are used throughout, i.e., e2ϭបϭmeϭ
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