Core-Level Binding-Energy Shifts Due to Reconstruction on the Si(111) 2 × 1 Surface

High-resolution photoemission spectra of the Si $2p$ level for freshly cleaved Si(111) reveal two additional core-level structures which are shifted relative to the bulk. The observed shifts are 0.59±{}0.04 eV to lower and 0.3±{}0.03 eV to higher binding energy, respectively. These shifted peaks, which vanish with increasing contamination of the surface, are shown to be directly correlated with reconstruction on the Si(111) 2×{}1 surface.