title: Optical properties of protonated Rhodamine 19 isomers in solution and in the gas phase.
abstract: Visible light absorption and fluorescence of three positional isomers of protonated Rhodamine 19 (o-, m- and p-R19H(+)) were studied in solution and in the gas phase. In solution, strong solvatochromic effects lead to spectral shifts between rhodamine isomers. In contrast, in the gas phase, these species were found to exhibit very similar fluorescence, while pronounced differences were observed in the absorption spectra. The o-R19H(+) was found to have the largest Stokes shift in the gas phase (around 10 nm), suggesting that an intramolecular relaxation operates in the excited electronic state for this isomer. Several mechanisms for this relaxation are proposed, such as the change of the dihedral angle between the carboxyphenyl group and the xanthene chromophore or that between the carboxylic group and the phenyl ring.
authors.affiliation: Department of Chemistry and Applied Biosciences, ETH Zurich, CH-8093 Zürich, Switzerland.
authors.forename: Konstantin
authors.initials: K
authors.lastname: Chingin
authors.forename: Roman M
authors.initials: RM
authors.lastname: Balabin
authors.forename: Vladimir
authors.initials: V
authors.lastname: Frankevich
authors.forename: Huanwen
authors.initials: H
authors.lastname: Chen
authors.forename: Konstantin
authors.initials: K
authors.lastname: Barylyuk
authors.forename: Robert
authors.initials: R
authors.lastname: Nieckarz
authors.forename: Alexey
authors.initials: A
authors.lastname: Fedorov
authors.forename: Renato
authors.initials: R
authors.lastname: Zenobi