Primary photochemical processes of excited phenols in ethanol

The primary photochemical processes of phenols in ethanol solution are stud ied by nanosecond laser flash photolysis. Transient signals in photolysis a t 266 nm are recognized as belonging to solvated electrons, phenoxyl radica ls, and the triplet state of the phenol. The onset of the T-T absorption sp ectrum of phenol is around 450nm. In addition to the absorption around 400 nm, phenoxyl radicals were found to exhibit a broad, weak absorption band i n the red region where the extinction coefficient is determined to be 300 /- 150 M-1 cm(-1) at 580 nm. A delayed fluorescence of phenol, assigned to T-T annihilation, is observed in the region 310-360 nm. Laser dose dependen t decay kinetics of solvated electrons is explained by their reaction with the triplet state of the phenol. Simple model calculations show that the ra te constant of this latter reaction is approximately 10(2) times larger tha n that for reaction with the corresponding ground-state phenol.