Optical Absorption Spectroscopy of Molecules Adsorbed on Ni(111) and Energy Transfer from the exp 3 eta pi * State of Pyrazine to Ni(111) and Ag(111) Surfaces

摘要

Changes in the optical response of a Ni(111) surface as a result of adsorption of molecules is measured with a spectroscopic rotating analyzer ellipsometer. For the molecules pyridine, pyrazine, and naphthalene condensed onto the nickel surface at low temperature, the changes in optical response can be described with a dielectric model which treats the adsorbed phase as a separate continuous medium of well-defined thickness and complex refractive index. For annealed layers less than 100 A thick, the absorption coefficient corresponds well with the known optical absorption spectrum of these molecules. When a wide variety of molecules are chemisorbed onto the Ni(111) surface, the modification of the optical response can no longer be described by considering the optical properties of the adsorbate alone. Rather, every molecule studied revealed a single broad absorption maximum at 4.2 eV.