Dynamics of excited-state proton transfer from 1-naphthol to urea

The excited-state intermolecular proton transfer from 1-naphthol to urea has been studied in methanol. In the absence of urea, the excited 1-naphthol (ROH*) decays exponentially in methanol. However, upon the addition of urea, the decay becomes non-exponential. It is attributed to a geminate recombination of an ion-pair in the solvent cage. The quenching constant of ROH* by urea and some rate constants are evaluated by using both the steady-state fluorescence and picosecond fluorescence decay measurements.