Observation of a new surface state on Cu(001)

High-resolution angle-resolved photoemission studies of the Cu(001) surface demonstrate the existence of a surface state which has not previously been reported. The state is located in a relative bulk band gap near the Fermi energy at the X̄ point of the two-dimensional Brillouin zone. Its energy position and dispersion are in excellent agreement with recent calculation for this surface. Comparisons are made of this state's natural energy width and dispersion with similar states on other copper surfaces.