Laser excited emission spectroscopy of azulene in the gas phase

In this paper we present the results of an experimental study of the radiative decay of the two lowest singlet states Si and S-z of the azulene molecule in the gas phase excited by a Q switched ruby laser ( 14 400 cm ^-1) and by its second harmonic (28 800 cm~J). Spectroscopic information has been obtained concerning the energy resolved spectra of the Si→So and of the S2→Si emission. The quantum yield data for the Si→So decay led to an estimate of the nonradiative decay time of 5i. The branching ratio between the Si→So and the Sr→Si emissions was utilized for the evaluation of the 52→Si radiative decay time. The study of the consecutive two photon So→Si→Sa excitation leads to an estimate of the S₁→S₂ absorption cross section near the electronic origins of the two excited states. The decay characteristics of the lowest excited singlet state of the "isolated" azulene molecule confirm the theoretical prediction concerning nonradiative electronic relaxation in the statistical limit.