title: Influence of solvent and substituent on excited state characteristics of laser grade coumarin dyes.
abstract: Absorption and fluorescence emission of 4 and 7 substituted coumarins viz. C 440, C 490, C 485 and C 311 have been studied in various polar and non-polar organic solvents. These coumarin dyes are substituted with alkyl, amine and fluorine groups at 4- and 7-positions. They give different absorption and emission spectra in different solvents. The study leads to a possible assignment of energy level scheme for such coumarins including the effect on ground state and excited state dipole moments due to substitutions. Excited state dipole moments of these dyes are calculated by solvetochromic data experimentally and theoretically these are calculated by PM 3 method. The dipole moments in excited state, for all molecules investigated here, are higher than the corresponding values in the ground state. The increase in dipole moment has been explained in terms of the nature of excited state and resonance structure.
authors.affiliation: Department of Applied Physics, Guru Jambeshwar University, Haryana, Hisar, India. vijay_kumar_sharma@hotmail.com
authors.forename: Vijay K
authors.initials: VK
authors.lastname: Sharma
authors.forename: P D
authors.initials: PD
authors.lastname: Saharo
authors.forename: Neera
authors.initials: N
authors.lastname: Sharma
authors.forename: Ramesh C
authors.initials: RC
authors.lastname: Rastogi
authors.forename: S K
authors.initials: SK
authors.lastname: Ghoshal
authors.forename: D
authors.initials: D
authors.lastname: Mohan
mesh_terms: D004396:Coloring Agents / Q000737:chemistry* / Q000494:pharmacology; D003374:Coumarins / Q000032:analysis / Q000737:chemistry*; D008027:Light; D008956:Models, Chemical; D012997:Solvents / Q000494:pharmacology; D013053:Spectrophotometry
chemical_list: D004396:Coloring Agents; D003374:Coumarins; D012997:Solvents; C030123:coumarin