Time-Resolved Thermal Lensing Studies on Metastable Species

Time-resolved thermal lensing (TRTL) techniques have been applied to resolve photophysical and ther-modynamic parameters for various metastable species, of which the relaxation dynamics are dominated by the radiationless transition. Using 1H-phenalen-1-one as a sensitizer, the lifetime (), absolute quantum yield and efficiency of generation (S T) of singlet molecular oxygen (1g) have been determined in various or-ganic solvents. In particular, through the development of an ultrasensitive detecting system, TRTL studies on the relaxation dynamics of O2( 1 g) become feasible in aqueous solution. In another application, based on the TRTL technique in combination with the O2 sensitization experiment, the T1-S0 energy gap of the pro-ton-transfer tautomer in 3-hydroxyflavone, which is otherwise inaccessible due to the dominant radiationless deactivation, has been deduced to be ~ 8500 1020 cm-1