PHOTOPHYSICAL PROPERTIES AND LASER CHARACTERISTICS OF A NEW RIGID AMINOCOUMARIN DYE LASING IN THE BLUE-GREEN REGION

The photophysical properties of a new dye, 7-Diethyl AminoCoumarin wit h a Rigid substitution in the 3-position (referred to as DARC) have be en studied in three solvents: dioxane, DMF and DMSO. The dye has been found to have a fluorescence quantum efficiency (phi(fl)) between 0.40 and 0.80 in these solvents. The dye-laser performance of this dye has also been investigated in dioxane, DMF and DMSO, under nitrogen-laser pumping and compared with that of the commercially available standard laser dye, Coumarin 515 (C-515). A tuning range of nearly 70 nm was o btained in the blue-green region with an efficiency up to 80% of that of the standard dye. The observed characteristics of the dye are expla ined in terms of the sructural rigidization of the dye in the 3-positi on which inhibits the formation of the Twisted Intramolecular Charge T ransfer (TICT) conformation in the excited state leading to an enhance ment of the phi(fl) and a considerable improvement in the laser perfor mance.