Direct experimental determination of the K2pand Cl2pcore-level binding energy shifts between molecular and solid KCl: Line broadening effects

Abstract

Using a technique used previously for metals, the K $2p$ and Cl $2p$ photoelectron spectra of KCl have been measured from the molecular vapor and nonconductor solid simultaneously---a direct measurement for a nonconductor. The Cl $2p$ core level in bulk-solid KCl has a 0.79-eV larger binding energy than its molecular KCl counterpart, but the K $2p$ core level in bulk-solid KCl has a 3.75-eV smaller binding energy than in molecular KCl. After correction for the instrumental resolution, the Cl $2p$ experimental linewidths (FWHM) for both molecular (0.40 eV) and solid spectra (0.56 eV) are much smaller than the corresponding K $2p$ molecular and solid linewidths (0.88 and 0.93 eV, respectively). It is concluded that final-state vibrational splitting is the dominant factor in determining both molecular and solid-state linewidths, with phonon broadening being a smaller effect for the solid.