Berlin 2008 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 8: POSTERS Dynamics and Diffusion
CPP 8.5: Poster
Monday, February 25, 2008, 16:45–19:00, Poster A
NMR surprizes with thin slices and strong gradients — •Achim Gädke1, Benjamin Kresse1, and Nikolaus Nestle2 — 1Institute of Condensed Matter Physics, Technische Universität Darmstadt — 2present address: BASF AG Ludwigshafen GKP/P, G201
In the context of our work on diffusion-relaxation-coupling [1] in thin excited slices, we perform NMR experiments in static magnetic field gradients up to 200 T/m [2]. For slice thicknesses in the range of 10 µm, the frequency bandwidth of the excited slices becomes sufficiently narrow that free induction decays (FIDs) become observable despite the presence of the strong static gradient. The observed FIDs were also simulated using standard methods from MRI physics [3]. Possible effects of diffusion during the FID duration are still minor at this slice thickness in water but might become dominant for smaller slices or more diffusive media. Furthermore, the detailed excitation structure of the RF pulses was studied in profiling experiments over the edge of a plane liquid cell. Side lobe effects to the slices will be disucssed along with approaches to control them. The spatial resultion achieved in the profiling experiments furthermore allows the identification of thermal expansion phenomena in the NMR magnet. Measures to reduce the temperature drift problems are presented.
[1] A. Gädke, N. Nestle 2005 Diffusion Fundamentals 3 38.1-38.12
[2] I. Chang, F. Fujara, B. Geil, G. Hinze, H. Sillescu, A. Tölle, J. Non-Cryst. Sol. 172-174, (1994) 674-681
[3] T. H. Jochimsen, A. Schäfer, R. Bammer, M. E. Moseley, J. Mag. Res. 180 (2006), 29-38