Physics of theBe(101¯0)Surface Core Level Spectrum

Photoelectron diffraction has been utilized to confirm the theoretical prediction that the surface core level shifts observed for $\mathrm{Be}\left(10\overline{1}0\right)$ have been improperly assigned. The original assignment based upon the relative intensity of the shifted components was intuitively obvious: the peak with the largest shift of $-0.7\mathrm{eV}$ with respect to the bulk was associated with the surface plane, the next peak shifted by $-0.5\mathrm{eV}$ stems from the second layer, and the third peak at $-0.22\mathrm{eV}$ from the third and fourth layers. First-principles theory and our experimental data show that the largest shift is associated with the second plane, not the first plane.