ADSORPTION OF BENZENE ON MO(100) AND MGO(100) MO(100) STUDIED BY ULTRAVIOLET PHOTOELECTRON AND METASTABLE IMPACT ELECTRON SPECTROSCOPIES/

By employing metastable impact electron spectroscopy (MIES) and ultrav iolet photoelectron spectroscopy (UPS) together with work-function mea surements, three adsorption states of benzene have been identified on the clean Mo(100) surface at 100 K: a chemisorbed layer, a second phys isorbed layer with the aromatic rings plane parallel to the surface, a nd at higher coverages, an adsorbed layer with the molecular planes es sentially perpendicular to the surface. The rapid appearance of the up right (edge-on) phase for benzene adsorbed on the MgO-covered Mo(100) surface suggests that the adsorption dynamics on MgO are similar to th ose for the Mo(100) surface, but no chemisorbed layer forms for the Mg O surface. In addition, it was found that benzene adsorption on the Mg O-covered Mo(100) surface does not lead to perfectly formed, closely p acked layers. (C) 1998 Elsevier Science B.V. All rights reserved.