New low-energy-electron-diffraction fine structure on W(110) and effect of hydrogen chemisorption

High-resolution low-energy-electron-diffraction (LEED) measurements of the specular beam from W(110) are presented. A new LEED fine structure associated with the ($\overline{2}0$) beam threshold is observed and studied in detail. The evolution of this feature under hydrogen chemisorption is also examined. Modification of the fine-structure line shape with gas coverage is explained by a gradual change in the scattering properties of the substrate rather than by a transformation of its surface potential barrier. The strengthening of the fine structure with gas exposure could be indicative of an ordered chemisorption in an interstitial site for hydrogen on W(110).