Natural linewidth of the Ag(111)<b><i>L</i></b>-gap surface state as determined by photoemission spectroscopy

Abstract

The Ag(111) surface state in the L gap has been measured at $T=30 \mathrm{K}$ by high-resolution photoemission spectroscopy $(\ensuremath{\Delta}E=3.7 \mathrm{meV}).$ 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 ${\ensuremath{\Gamma}}_{\mathrm{tot}}=6.2\ifmmode\pm\else\textpm\fi{}0.5 \mathrm{meV}$ 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 $\ensuremath{\Gamma}=9.8\ifmmode\pm\else\textpm\fi{}1.2 \mathrm{meV}.$