Heidelberg 2015 – scientific programme

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MO: Fachverband Molekülphysik

MO 10: Experimental Techniques

MO 10.2: Talk

Tuesday, March 24, 2015, 14:45–15:00, PH/SR106

Polarisation Infrared Spectroscopy on Oriented Substrates (PIROS) - A case study on Phenazine — Michaela Braun, Gernot Engler, Katharina Hunger, •Alexander Wohlert, Karl Kleinermanns, and Michael Schmitt — Universität, Düsseldorf, Germany

Vibrationally induced changes of the molecular dipole moment give rise to different band types in infrared spectroscopy. According to the projection of the molecule's normal modes onto the inertial axes of the molecule these bands can be classified as a, b or c types. In case of molecules with C2v-, D2- or D2h-symmetry the inertial axes and the components of the dipole moment are parallel to each other and therefore the molecules normal modes can easily be classified. In crystals or molecules oriented in films on surfaces, the absorption of polarized IR light depends on the orientation of the molecules with respect to the surface and the plane of polarization of the light. Since the dipole moment changes have a well-defined orientation with respect to the molecular frame, defined by the main inertial axes, the orientation of the molecules on a surface can be determined from the dependence of the IR intensities using polarized IR light, while rotating the sample along the axis of the He-Ne-Laser-beam. To test this method we chose the phenazine molecule since it has D2h symmetry.