Optically Detected Electron Spin Resonance of Aromatic Ketones Adsorbed on Surfaces: Al2 O3 Powder and Single Crystal, Ag Film and Molecular Crystals

Abstract

Over the past years, much interest has been directed to the study of molecules adsorbed on surfaces, particularly because of the applicability to industrial surface chemistry. Optically detected electron spin resonance in the phosphorescent triplet state, has been shown to be a powerful method of probing adlayer molecules on surfaces. Aromatic ketones were chosen for the adsorption study because the phosphorescent excited triplet state of benzophenone and benzoyl and pyridyl ketones has been well characterized. The adsorption onto the powdered and single crystals of Al2O3 was accomplished from a cyclohexane solution. For the adlayers on molecular crystals, several observations are noteworthy. Adsorption leads to adlayer-substrate interaction, resulting in the formation of an interface. The total phosphorescence rate constants for each of the magnetic sublevels are given also as a function of the silver film thickness.