Femtosecond Intramolecular Proton Transfer and Vibrational Relaxation in the Liquid Phase

Abstract

Photoinduced intramolecular proton transfer in benzotriazoles is directly monitored by femtosecond spectroscopy. Proton transfer in the excited state occurs on a 100 fs time scale and is followed by radiationless deactivation of the reaction product with time constants of about 150 fs. The reaction cycle is completed by the subpicosecond proton back-transfer in the electronic ground state. The back-reaction creates vibrationally hot molecules which cool down within 40 ps by collisional interaction with the surrounding solvent.