title: Nonlinear transmission and excited-state absorption in fluorene derivatives.
abstract: The nonlinear transmission and the excited-state absorption spectra of three fluorene derivatives exhibiting large two-photon absorptivity were measured by the third harmonic of a picosecond Nd:YAG laser. We analyzed their capability for exhibiting stimulated emission in polar solvents and found that asymmetrical fluorene compounds with a diphenylamino substituent exhibited large Stokes shifts (approximately 8000 cm(-1)), high quantum yields (approximately 0.9-1.0), and no optical gain over their entire fluorescence spectral region. In contrast, a symmetrical fluorene derivative with vinylphenylbenzothiazole substituents in positions 2 and 7 underwent lasing under one-photon excitation by use of picosecond pulsed irradiation.
authors.affiliation: Department of Chemistry and College of Optics and Photonics, University of Central Florida, P.O. Box 162366, Orlando, Florida 32816-2366, USA. kbelfiel@mail.ucf.edu
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Belfield
authors.forename: Mykhailo V
authors.initials: MV
authors.lastname: Bondar
authors.forename: Florencio E
authors.initials: FE
authors.lastname: Hernandez
authors.forename: Alma R
authors.initials: AR
authors.lastname: Morales
authors.forename: Olga V
authors.initials: OV
authors.lastname: Przhonska
authors.forename: Katherine J
authors.initials: KJ
authors.lastname: Schafer