title: Structural and solvent dependence of superexciplex.
abstract: In this paper, we show that a few coumarin dye solutions exhibit dual amplified spontaneous emission (ASE) spectra under pulsed laser excitation, though all these solutions exhibit only one fluorescence band under steady-state conditions. The anomalous band, appearing only in ASE spectra, had been attributed to the superexciplex--a new molecular species. This is made of two excited molecules and is obtainable only under pulsed laser excitation. This complex is different from the well known excimer or exciplex, wherein only one atom or molecule is in the excited state. The superexciplex is possible with the two polar excited molecules coming together to form an excited state association, with the solvent acting as some sort of bridge. With very polar dye molecules, such an association is possible even with the inert benzene acting as a bridge; otherwise solvents like ethyl acetate, with an oxygen atom, is necessary for the linkage.
authors.affiliation: Department of Physics, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia.
authors.forename: V
authors.initials: V
authors.lastname: Masilamani
authors.forename: A S
authors.initials: AS
authors.lastname: Aldwayyan
mesh_terms: D004396:Coloring Agents / Q000737:chemistry* / Q000528:radiation effects; D003374:Coumarins / Q000737:chemistry* / Q000528:radiation effects; D007834:Lasers; D008968:Molecular Conformation; D015394:Molecular Structure; D012997:Solvents; D013050:Spectrometry, Fluorescence; D013053:Spectrophotometry; D013816:Thermodynamics
chemical_list: D004396:Coloring Agents; D003374:Coumarins; D012997:Solvents