Two-photon-induced excited-state intramolecular proton transfer process in 1-hydroxyanthraquinone

Two-photon-induced excited-state intramolecular proton transfer (ESIPT) process of 1-hydroxyanthraquinone has been investigated by using a fluorescence up-conversion technique. The emission spectrum by two-photon excitation was identical with that by one-photon excitation. In temporal profiles, the fastest decay component shorter than 120 fs was interpreted to indicate the occurrence of ESIPT accompanied with the delocalization of excited-state wave function. The decay components of 2.5 and 18 ps were assigned to vibrational cooling and rotational diffusion processes, respectively. Time-zero anisotropy value was measured close to 0.53, which is accounted to be two-photon absorption process.