High-resolution electron energy loss spectroscopy study on chemisorption of hydrogen on Cu(1 1 1)

The chemisorption of atomic hydrogen on the Cu(1 1 1) surface at 100 K was studied with high-resolution electron energy loss spectroscopy. At low H coverage (below 0.5 ML), two loss features were observed and attributed to the perpendicular and parallel modes of atomic H adsorbed at a single site on the surface, respectively. The observation of two vibrational modes allows an unambiguous assignment of adsorption at a threefold hollow site on Cu(1 1 1). At high H coverage (above 0.5 ML), a new loss feature was also found in the specular direction in addition to the saturated low-coverage features. The new high-coverage feature is assigned to absorbed H at a subsurface site, following the thermal desorption studies and the theoretical predictions on the H absorption into the Cu(1 1 1) surface.