A DENSE AND CO FREE BENZENE STRUCTURE ON RH(111)

The adsorption of benzene on Rh(lll) was investigated by using low-energy electron diffraction (LEED), thermal desorption spectroscopy (TDS), and angle-resolved ultraviolet photoelectron spectroscopy (ARUPS). Under very good vacuum conditions we found a (root 19x root 19)R23.4 degrees pure benzene adsorption structure which could be converted to the c(2 root 3x4)rect and (3x3) structures by admission of CO. The adsorption symmetry, the possible adsorption sites, the orientation of the benzene molecules, and the molecular interaction in the adsorbate layer were investigated with ARUPS. The structure exhibits a work function change of Delta e Phi = -1.47 eV, indicating one of the highest benzene densities on Rh(lll) observed so far. A considerable dispersion of the 2a(lg)-derived band of the adsorbate layer was observed.