Picosecond dynamics of the S2 excited state of azulene and its van der Waals complexes with Ar and Xe

The dynamics of the second excited singlet (S2) states of jet-cooled azulene (Az) and its van der Waals complexes with one and two atoms of Ar and Xe have been investigated. Quantum interference effects due to restricted intramolecular vibrational redistribution in azulene have been reinterpreted. Lifetime shortening in the 1:1 and 1:2 complexes with Xe is attributed to an enhancement of the rate of S2T1 intersystem crossing by the external heavy atom effect. Excitation of the complexes to states with Evib > Eb produces energy-resolved fluorescence decays which exhibit sequential intramolecular vibrational redistribution-vibrational predissociation.