The surface- and bulk-derived components of the Si 2p core levels, acquired by photoemission from Si(111)-(7×7), show strong and different oscillations caused by extended fine structure above the 2p edge. An analysis of these oscillations yields the bulk and surface bond lengths which agree well with the known structure. The heretofore controversial issues of the photoemission escape depth and the atomic origin of the surface core levels are resolved.

• Received 9 August 1993

DOI:https://doi.org/10.1103/PhysRevLett.71.2955