Core-level photoemission from graphite

Abstract

Core-level photoemission spectra of graphite have been measured at very high resolution. The C $1s$ level is found to have a lifetime width with an upper limit of $165\ifmmode\pm\else\textpm\fi{}15\mathrm{meV},$ which is considerably narrower than previously reported. The width is still substantially larger than that observed for carbon ionic states in small molecules. We argue that the additional broadening in the solid state is not due to a surface core-level shift or initial-state band formation, but may be due to unresolved final-state phonon broadening.