title: Vibronic Quasi-Free Rotation Effects in Biphenyl-Like Molecules. TD-DFT Study of Bifluorene.
abstract: In this paper, we investigate the vibronic shape of the lowest UV-visible absorption band of biphenyl-like systems, using the bifluorene molecule as a workhorse. The molecule is here regarded as a one-dimensional two-level system, whose ground and excited states are simulated with time-dependent density functional theory and semiempirical methods. The vibrational Schrödinger equation is then numerically solved along the torsional coordinate, and the vibronic shape of the absorption band is modeled. Comparisons with the harmonic approximation, with or without the Franck-Condon approximation, are performed. This study confirms that a vibronic effect is most likely responsible for the strong dissymmetry of the lowest UV-visible absorption band of biphenyl-like systems and that, for such systems, the experimental data should be extracted using the whole absorption band, instead of a Gaussian fit on the first part of the band, as it is often done when a superposition between several electronic transitions is suspected.
authors.affiliation: Université de Lyon, École Normale Supérieure de Lyon, Laboratoire de Chimie, UMR 5182 du CNRS, 46 Allée d'Italie, F-69364 Lyon Cedex 07, France, and Université Lyon 1 and CNRS UMR 5180 du CNRS Sciences Analytiques, Chimie Physique Théorique, Bat. Paul Dirac (210), 43 Boulevard du 11 Novembre 1918, F-69622 Villeurbanne Cedex, France.
authors.forename: Rémy
authors.initials: R
authors.lastname: Fortrie
authors.affiliation: Université de Lyon, École Normale Supérieure de Lyon, Laboratoire de Chimie, UMR 5182 du CNRS, 46 Allée d'Italie, F-69364 Lyon Cedex 07, France, and Université Lyon 1 and CNRS UMR 5180 du CNRS Sciences Analytiques, Chimie Physique Théorique, Bat. Paul Dirac (210), 43 Boulevard du 11 Novembre 1918, F-69622 Villeurbanne Cedex, France.
authors.forename: Henry
authors.initials: H
authors.lastname: Chermette