Normally unoccupied states on C(111) (diamond) (2×1): Support for a relaxedπ-bonded chain model

A normally unoccupied electronic state on the reconstructed (2×{}1) surface of C(111) (diamond) is characterized with angle-resolved two-photon photoelectron spectroscopy. The state is seen in the bulk band gap, lying 4.8 eV above the valence-band maximum. Comparison between the measured dispersion of this band and published theoretical band-structure calculations supports a relaxed Pandey {π}-bonded chain model of the surface reconstruction.