Adsorption of styrene on Ag(1 1 1)

Temperature-programmed desorption (TPD) and reflection absorption infrared spectroscopy (RAIRS) have been used to investigate the adsorption, desorption and molecular conformation of styrene adsorbed on Ag(1 1 1) at 100 K. Styrene adsorbs and desorbs molecularly. Three peaks are resolvable in TPD—257 K (α1), 187 K (α2) and 167 K (α3)—depending on the coverage. RAIRS indicates that the α1 and α2 adsorption states are in contact with silver surface. For α1, the aromatic ring lies parallel to the Ag(1 1 1) surface and for α2, nearly parallel. Although the α3 state in TPD is ascribed to the bulk-like multilayer desorption, RAIRS indicates that, as-dosed, this coverage region is separable into two components—a second layer and subsequent layers. In the second layer, the principle axis of styrene lies between 5° and 8° away from the surface normal, making a T-like configuration with the first layer. For subsequent layers, the RAIRS data are consistent with a mixture of orientations.