Rotational isomerization in a chemisorbed layer: ethyl formate on Ni(111)

Reflectance absorbance infrared spectroscopy (RAIRS) and thermal desorption data for ethyl formate on Ni(111) display a surface coverage dependence consistent with rotational isomerization within the chemisorbed layer. The (Z)-gauche adsorbate conformation is selectively populated at low surface coverages, and conversion to the (E)-trans conformation occurs as the surface coverage is increased. This interconversion sets in at coverages where lateral interactions within the adsorbed layer become evident, thereby suggesting an important role for steric effects.