నైరూప్య

Spectral behavior and laser activity ofN,N-bis (3- hydroxypyrimidenyl) 3, 4, 9, 10-perylenebis(dicarboximide) (HPyPBD)

S.A.Azim

The photophysical properties such as singlet absorption, molar absorptivity, excitation and fluorescence spectra as well as fluorescence quantum yield ofHPyPBDhave beenmeasured in different solvents. Both electronic absorption and fluorescence spectra are not sensitive to medium polarity, while the fluorescence quantum yield (f) is solvent dependent. HPyPBD dye displays molecular aggregation in water. The photochemical quantum yield (c) of contact ion pair formation has been determined in carbon tetrachloride upon irradiation with 525 nm lights. Dye solution in DMF gives weak laser emission around 560 nm upon pumping with 337.1 nm nitrogen laser pulses. The excitation energy transfer from 9, 10- diphenylanthracene (DPA) to HPyPBD has been studied to improve the laser emission of HPyPBD. The values of energy transfer rate constant kET and critical transfer distance (Ro) indicate a Förster type energy transfer mechanism. The geometrical and electronic structures of HPyPBD molecule, in both the ground and excited states, have been elucidated using AMI and ZINO/S semiemperical quantumcalculations.