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 $T=30\mathrm{}\hspace{0.5em}\mathrm{K}$ by high-resolution photoemission spectroscopy $(\Delta E=3.7\mathrm{}\hspace{0.5em}\mathrm{meV}).\mathrm{}$ 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 ${\Gamma }_{\mathrm{tot}}=6.2\mathrm{}\pm 0.5\hspace{0.5em}\mathrm{meV}$ 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 $\Gamma =9.8\mathrm{}\pm 1.2\hspace{0.5em}\mathrm{meV}.$