Directional uv photoemission from (100) and (110) molybdenum surfaces

A study of the (100) and (110) molybdenum surfaces by directional photoemission spectroscopy is presented. Energy distribution spectra formed by photoelectrons emitted normal to the surfaces have been measured for photon energies between 10.2 and 21.2 eV. The results are discussed in terms of calculated band structure within the framework of the $K_{\parallel }$-conservation assumption. A good agreement is found between the main features of the experimental spectra and the emission expected from the band structure along the corresponding symmetry line in the Brillouin zone, assuming essentially direct-transition and surface-emission processes. Two extra structures are interpreted in terms of surface states or resonances: on the (100) surface, 0.5 eV below $E_F$; on the (110) surface, 4.5 eV below $E_F$ in the $s$-$d$ hybridization gap.