Dresden 2011 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 11: Poster: New Instruments and Methods

CPP 11.17: Poster

Montag, 14. März 2011, 17:30–19:30, P2

Spin-Flip NMR Spectroscopy as a Tool for Structure Investigations — •Günter Hempel and Matthias Roos — Martin-Luther-Universität, Institut für Physik, Betty-Heimann-Straße 7, D-06120 Halle

We propose a NMR procedure which can give information about molecular structure also in disordered systems. This method is based on polarization exchange between neighboured 1H nuclei. The exchange rate is proportional to the coupling constant which depends on length and orientation of the spin-spin connection vector with respect to the magnetic field.

Because of the particular structure of the effective Hamiltonian, the oscillations survive relatively long time which can lead to rather high accuracy of the determination of the frequency and subsequently of the structural parameters. Coarsely spoken, we burn holes into the proton polarization and follow the subsequent re-filling of the holes. In microsecond range the oscillatory behaviour mentioned above is observed, and at millisecond scale spin-diffusion processes dominate.

This method was applied to liquid-crystal compounds to study certain bond angles in the mesomorphic phases which are not accessible by scattering methods. Furthermore, we could estimate spin-diffusion constants in liquid crystals and polymeric materials.