Radiationless Deactivation of Singlet Excited States of Complex Molecules in the Gas Phase

The ways of degradation of electronic excitation energy of singlet states of complex molecules in the gas phase with various character of dependence of the quantun yield and lifetime of fluorescence on the excess vibrational energy of excited molecules, ΔE* vib , are discussed. From the analysis of literature data on phthalimide and anthracene derivatives and perylene, and also from the results of investigations conducted in the present study for 9,10-dimethylanthracene and 9,10-diphenylanthracene it follows that in the majority of cases radiationless degradation of electronic excitation energv is realized both by means of intersystem crossing and internal conversion. For all studied molecules, with the exception of anthracene, an increase in intersystem crossing with increasing ΔE* vib of excited singlet state is observed, while the internal conversion probability may either increase or decrease. In particular, an