الفهرس 
b-Operation of the dye laserOnly 14 pages are availabe for public view
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Abstract
The emission , excitation and absorption spectra together with the fluorescence and photochemical quantum yields of some diolefinic derivatives have been studied in different media including organic solvents as well as micellar and microemulsion media. Both 4- [2-(2-pyridyl)etheny1] and 4- [2-(4-pyridyl) ethenyl] chalcones show a large positive solvatochromic effect. The fluorescence quantum yields (of) also increase substantially as the medium viscosity increases with a subsequent decrease in the photochemical quantum yield (Oc) values . The present series of compounds undergo excited state molecular aggregation in concentrated solutions giving excimer-like emission that coincides with emission from crystalline samples. The enthalpies of photoassociation have been estimated. The 4- [2-(2-pyridyl)ethenyl ] chalcone derivative acts as an efficient quencher of the fluorescence of 1,4-biscl3-pyridyl-2-viny1)benzene (P2VB) laser dye via a static - type mechanism. The emission characteristics , solution lifetimes,and molecular association of methyl iodide derivative of the laser dye 1,4-bis(8-pyridyl-2-viny1)benzene (P2VB.MeI) together with isoelectronic dye 1,4-bis(4-pyridyl-2-viny1)benzene (P4VB) are reported. Both compounds undergo molecular aggregation with subsequent excimer formation.