Light-induced electron emission from polymethylphenyl siloxane oils

Light-induced electron emission from tetramethyl tetraphenyl trisiloxane, (Dow-Corning silicone oil DC704) and trimethyl pentaphenyl siloxane (Wacker Chemie silicone oil AN175) has been measured as a function of photon energy. Absolute quantum yield and threshold energy were determined. The threshold energy of 7.5 eV for both siloxanes is comparable to the thresholds of other polymethylphenyl siloxanes with phenyl/methyl ratios of 1/3 and 1/18, which have been investigated by the authors. The quantum yield as a function of photon energy shows a systematic change with variation of the phenyl/methyl ratio. This dependence on the molecular structure is ascribed to a change of the initial ionization quantum yield.