1,4-Bis (β-Pyridyl-2-Vinyl) Benzene (P2VB) and 2,5-Distyryl-pyrazine (DSP) as Blue Laser Dyes

Solutions of P2VB and DSP in dimethyl-sulphoxide (DMSO) of concentration ca. 10 –3 M/l act as laser dyes on pumping with nitrogen laser. P2VB and DSP are lasingin the ranges 390–440 nm (λ max = 416 nm) and 435–465 nm (λ max = 447 nm) respectively.An equimolar mixture of P2VB and DSP behaves as an energy transfer dye laser (ETDL)and is lasing in the range 429–455 nm (λ max = 438 nm). Such ETDL system obeys along range coulombic energy transfer mechanism with a critical transfer distanceR 0 = 7.5 nm. The fluorescence quantum yields of both dyes have been measured, and in DMSO φ f= 0.46 and 0.35 for P2VB and DSP respectively. Both dyes show a remarkable photostability upon nitrogen laser excitation. This hasbeen attributed to the role of the 337 nm light in inducing a back photo-chemicalreaction of the initially formed photoproducts consisting mainly of photo-oligomersand cis-photoisomers.