POLARIZED FLUORESCENCE MEASUREMENTS OF JET-COOLED 2,5-DIPHENYLFURAN AND VANDERWAALS COMPLEXES

Picosecond-resolution time-correlated single-photon counting experiments have been used to monitor polarized fluorescence time profiles of jet-cooled 2,5-diphenylfuran (PPF) and some van der Waals aggregates. Recurrences of the fluorescence polarization anisotropy over 1-5 ns have been used to deduce mean rotational constants, and to assign structures for 1:1 van der Waals aggregates with argon and methane. In contrast with stilbene, the complexing species are found to be centrally bound on PPF. Also, the structures of higher aggregates are directly assigned; for PPF/Ar2 and /(CH4)2, the complexing species are shown to be attached to opposite faces of the planar PPF molecule (i.e. the 1,1 isomer is observed).