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Prof. em. Dr. Manfred Zeidler

Institut für Physikalische Chemie
Prof. em. Dr. Manfred Zeidler
RWTH Aachen University

Landoltweg 2
Raum 115
52056 Aachen
Germany

Telefon: +49-241-80-99361

e-mail

 

Research

The research carried out in our group concentrates around the topic of structure and dynamics in molecular liquids. Experimental as well as theoretical methods are employed.
 Structural investigations are conducted with the experimental methods of diffraction either of X-rays or of neutrons. At the institute we have our own X-ray diffractometer especially designed for liquid work, whereas for neutron diffraction we need powerful sources like the high-flux reactor at the Institute Laue-Langevin in Grenoble (France). 

In neutron diffraction it is advantageous to measure samples of different isotopic substitutions for the same molecule, because this is the prerequisite to disentangle atom-atom spatial correlations leading to a detailed description of structure. This description is in terms of geometrical arrangements of molecules, including the center of mass distribution as well as orientational correlations.

Investigations of the dynamics are carried out with the experimental methods of nuclear magnetic relaxation, spin-echo diffusion and quasielastic neutron scattering. The nuclear magnetic resonance measurements are carried out with the institute's own 250 MHZ and 300 MHz spectrometers, while for the scattering experiments different spectrometers at the nuclear center in Jülich are used. These experiments yield time correlation functions or their typical time constants, which are related to diffusion coefficients for rotational and translational molecular motions respectively. The temperature and pressure dependences of these motions are followed over a wide range.

With knowledge of the intermolecular potentials one can derive all above mentioned experimental quantities. For this purpose the methods of statistical thermodynamics are employed; either one relies on analytical expressions derived for dense fluids or one uses computer simulation methods. Both approaches are followed in our group, in order to reconstruct useful potentials from our experiments.