Heidelberg 2015 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 19: Electronic Spectroscopy

MO 19.3: Vortrag

Donnerstag, 26. März 2015, 15:15–15:30, PH/HS1

Geometry changes of ortho- and meta-Tolunitrile upon S1 -> S0 excitation: comparison of the effect of substituent positions in push-pull systems — •Felix Gmerek and Michael Schmitt — Heinrich-Heine-Universität, Düsseldorf, Germany

The nuclear structure of a molecule follows its electronic structure in the specific electronic state. Therefore, it is strongly influenced by electron pushing or pulling substituents and can easily be investigated by electronic spectroscopy.

Tolunitriles represent small push-pull-systems with an electron-pushing methyl-group and an electron-pulling cyano-group.

In this project, the ortho- and meta-isomers were investigated to compare the effects of different substituent positions.

According to the Franck-Condon-principle the fluorescence intensities depend on the geometry changes. Therefore the excited state geometry can be described by a displacement of the ground state, which is derived from the Franck-Condon-factors and the rotational constant changes.

The rotational constant changes upon electronic excitation have been measured by Alvarez-Valtierra et al. [1]. Additionally Franck-Condon-factors were obtained by single vibronic level fluorescence spectroscopy of the electronic origin and six vibronic bands for both isomeres.

[1] personal communication