Azulene Revisited: Picosecond Decay of the S1 State in the Gas Phase and in Solution

In this paper we report the results of an experimental study of picosecond time‐resolved relaxation dynamics of the S1 state of the azulene molecule in solution and in the low pressure gas phase, utilizing consecutive two‐photon excitation S0 → S1(v) → S2 (or S3), with the exciting and the monitoring picosecond pulses chosen at the same wavelength. The nonradiative electronic relaxation times for azulene in solution were τnr = 4 ± 3 ps for S(v = 5), excited at 530 nm, and τnr = 3 ± 2 ps for S(v = 2), excited at 625 nm, while for the “isolated” molecule case τnr = 4 ± 3 ps for S(v = 2), excited at 625 nm. The electronic relaxation rate of the S1 manifold exhibits only a weak dependence on the excess vibrational energy Ev up to Ev = 4800 cm−1. The electronic relaxation rate is practically unaffected by solvent perturbations, as appropriate for the statistical limit of intramolecular radiationless transitions.