Daniel Cossart

Bio: Daniel Cossart is an academic researcher from University of Paris. The author has contributed to research in topics: Emission spectrum & Ion. The author has an hindex of 12, co-authored 19 publications receiving 468 citations.

Emission spectra of seven fluorobenzene cations

Abstract: The emission spectra of C6F6 +, C6F5H+, the three C6F4H2 + and two C6F3H3 + (1, 2, 4 and 1, 3, 5) cations were obtained in the gas phase, in a special discharge tube. Symmetry and mode correlation of the fundamental frequencies of the parent neutral molecules enabled the isodynamic molecule method to be used for achieving vibrational analysis of the ion spectra. The vibronic structure in each emission spectrum is interpreted. Dynamic Jahn-Teller effects are shown to occur in the degenerate ground state of C6F6 + and of 1, 3, 5-C6F3H3 +, in particular irregular ground-state progressions in mode 6 are observed. Extensive Jahn-Teller calculations were made for 1, 3, 5-C6F3H3 +; frequencies and intensities in its progressions are in good agreement with the results of calculations based on the linear coupling model of Longuet-Higgins et al., using a deperturbed frequency ω = 477–484 cm-1 and a dimensionless interaction parameter D = 0·13-0·10. A review of the vibrational data of photoelectron spectra and Rydbe...

Rotational band contours of the first electronic transition origin bands of p-xylyl and p-fluorobenzyl

Abstract: The origin bands of the gas phase discharge emission spectra of the p-xylyl and p-fluorobenzyl radicals were photographed at high resolution. The observed band contours were fitted by computer-simulated type B rotational bands; this indicates that the transition moment in both cases is along the b in-plane short axis and corresponds to a 1 2 A 2-1 2 B 2 first electronic transition, as found previously in benzyl itself. For reasonable geometrical models of the ground state (methyl-group reduced to a mass-point in p-xylyl), A″, B″ and C″ rotational constants and their variations ΔA, ΔB and ΔC during the transition are determined. The band origins are found to be at 21700·5 ± 0·2 and 21524·0 ± 0·2 cm-1 respectively in p-xylyl and p-fluorobenzyl, with observed band maxima which are at 4606·57 A or 21702·05 cm-1 and 4644·14 A or 21526·48 cm-1, respectively. Four band sequences are identified in both spectra and assignments of the vibrational modes involved are discussed. In p-xylyl are also shown and discussed...

Multimode molecular dynamics beyond the Born-Oppenheimer approximation

Abstract: Mise au point. Theorie des effets de couplage vibronique multimodes. Probleme a 2 etats. Couplage vibronique mettant en jeu des modes et des etats degeneres. Effets du couplage vibronique multimodes en spectroscopie. Comportement statistique des niveaux d'energie vibroniques. Intersections coniques et evolution temporelle de la fluorescence