Experimental determination of the unoccupied bands of W(110)

Inverse photoemission from W(110) has been used to determine the dispersion of the unoccupied energy bands along the tungsten ΓN line. The critical points are determined to be Γ12 at 2.6 eV, N1 at 2.2 eV, and the lower limit of N4 at 3.2 eV. The upper bound of the lifetime broadening is estimated as 0.3-0.4 eV at 2-3 eV above EF. The image state is observed at 4.5 eV above EF, or 0.7 eV in binding energy, relative to the vacuum level. © 1993 The American Physical Society.