Adsorption of CO on NI (311). Investigations with HREELS

HREELS investigations of CO adsorption on the NI (311) surface are presented. The results show a striking similarity to CO adsorption on the Ni (110) surface which proves that the crucial structural features that govern the adsorption behavior are the close packed rows. In addition to the on top and bridge sites occupied at the Ni (110) surface there is evidence that threefold adsorption sites are occupied as well on the Ni (311) surface at saturation at low temperatures. Our results also support the reliability of the frequency rule of CO adsorption at on top and bridge sites if one takes into account the coverage dependence of the frequencies. Coadsorption with hydrogen drastically changes the adsorption behavior of CO.