DISCRIMINATION OF S-CIS S-TRANS CONFORMERS OF JET-COOLED METHYL CINNAMATE BY POPULATION LABELING SPECTROSCOPY/

The S-1-S-0 electronic spectrum of methyl cinnamate in a supersonic je t has been investigated to discriminate the transitions of the s-cis/s -trans conformers. Population labelling spectroscopy was applied to th e conformer discrimination, and vibronic bands belonging to each confo rmer were identified. The relative population was estimated from the f luorescence quantum yields obtained by lifetime measurements. It was f ound that both conformers exist almost equally in a supersonic jet. Th e conformer identification of the vibronic bands was carried out based on the difference of the red-shift of their hydrogen-bonded complexes with methanol.