By employing metastable impact electron spectroscopy (MIES) and ultraviolet photoelectron spectroscopy (UPS) together with work-function measurements, three adsorption states of benzene have been identified on the clean Mo(100) surface at 100 K: a chemisorbed layer, a second physisorbed layer with the aromatic rings plane parallel to the surface, and at higher coverages, an adsorbed layer with ...