EXPERIMENTAL-DETERMINATION OF THE UNOCCUPIED BANDS OF W(110)

Inverse photoemission from W(110) has been used to determine the dispe rsion of the unoccupied energy bands along the tungsten GAMMASIGMAN li ne. The critical points are determined to be GAMMA12 at 2.6 eV, N1 at 2.2 eV, and the lower limit of N4 at 3.2 eV. The upper bound of the li fetime broadening is estimated as 0.3-0.4 eV at 2-3 eV above E(F). The image state is observed at 4.5 eV above E(F), or 0.7 eV in binding en ergy, relative to the vacuum level.