Role of elastic scattering in electron dynamics at ordered alkali   overlayers on Cu(111)
  Scanning tunneling spectroscopy of p(2x2) Cs and Na ordered overlayers on Cu(111) reveals similar line widths of quasi two-dimensional quantum well states despite largely different binding energies. Detailed calculations show that 50% of the line widths are due to electron-phonon scattering while inelastic electron-electron scattering is negligible. A frequently ignored mechanism for ordered structures, i.e., enhanced elastic scattering due to Brillouin zone back folding, contributes the remaining width. 
C. Corriol, V.M. Silkin, D. Sanchez-Portal, A. Arnau, E.V. Chulkov,   P.M. Echenique, T. von Hofe, J. Kliewer, J. Kroeger, a...