الفهرس 
Absorption and fluorescence processesOnly 14 pages are availabe for public view
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Abstract
In the present study we report two new laser dyes namely 1,4-bis [ P-(2- quinolyl) vinyl] benzene ( BQVB ) and 2,5-bis-2-(2-naphthyl) vinyl pyrazine (B2NVP). An early-reported laser dye 1,4-bis [ P-(2-benzoxazolyl) vinyl]benzene ( BBVB ) has been further investigated. An anthracene organic dye that is 9-Phenyl 10- methoxyanthracene (PMA) has also been investigated. The diolefinic dye 1,4-bis [ P-(2-quinolyl) vinyl] benzene ( BQVB ) is an efficient fluorescer with $f values as high as 0.82 in n-heptane. The dye exhibits low values of the excited state lifetimes of ca. 0.4 ns . Both electronic absorption and fluorescence spectra are sensitive to medium acidity and in acidic media a strong fluorescence is obtained at 500 nm. The laser activity of BQVB has been investigated. Dye solution in N,N-dimethylformamide@MF) gives laser emission around 450 nm upon excitation by 337.1 nm nitrogen laser pulse. The excited state absorption S 1+S2 of BQVB has been measured using laser flash photolysis and in DMF the S1+S2 absorption occurs at ca.762 nm. Energy transfer from BQVB to rhodamine 6G and to molecular oxygen has been studied. The quantum yields for the trans-cis photoisomerization ($,) of BQVB in different organic solvents are also measured The low temperature absorption spectra of BBVB, BQVB and B2NVP have been measured in ethanolic solutions. Quantum-chemical calculations using PPP minimization program have been performed. B2NVP dye acts as a laser dye upon pumping with nitrogen laser (hex.=337. 1). B2NVP in dimethylformarnide (DMF) gves amplified spontaneous emission (ASE) maximum at about 470 tun. from the experimental result, the excited state absorption (ESA) occurs at around 500 run for B2NVP solutions in DMF and is assigned to S 1 +Sn absorption. This ESA inevitably reduces the laser efficiency of the dye.