Natural linewidth of the Ag(111)L-gap surface state as determined by photoemission spectroscopy

The Ag(111) surface state in the L gap has been measured at T=30 K by high-resolution photoemission spectroscopy (ΔE=3.7 meV). The experimental linewidth (full width at half maximum) at normal emission is less than 10 meV, from which an internal lifetime width of the surface states of Γₜₒₜ=6.2±0.5 meV is deduced. This value agrees with theoretical predictions but is smaller than the result obtained by a recent low-temperature scanning tunneling experiment, which gave a lifetime width equivalent to Γ=9.8±1.2 meV.