Regensburg 2010 – scientific programme
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SYMR: Symposium Nuclear Magnetic Resonance: from Applications in Condensed-Matter Physics to New Frontiers
SYMR 8: Glasses and Glass Transition
SYMR 8.5: Talk
Wednesday, March 24, 2010, 15:15–15:30, H48
Studying the dynamics of water molecules on a complex lattice: KOH doped tetrahydrofuran clathrate hydrate — •Helge Nelson1, Catalin Gainaru1, Andre Nowaczyk1, Sebastian Schildmann1, Burkhard Geil2, and Roland Böhmer1 — 1Experimentelle Physik III, Fakultät für Physik, TU Dortmund — 2Institut für Physikalische Chemie, Universität Göttingen
Because of kinetic hindrance during the freeze-out of the protons in clathrate hydrates an orientational glass transition is observed. By adding minute amounts of ionic dopants, e.g., KOH, the timescale of ordering can be accelerated significantly and an ordered phase is reached [1]. We applied a combination of dielectric and 2H-NMR techniques to study the lattice dynamics of the water molecules in a temperature range from 30 K to 260 K. The 2H-NMR techniques include temperature dependent lineshape analysis, measurement of relaxation times, and the stimulated-echo technique. This combination allows the observation of dynamics in a broad frequency and temperature window. We found several reorientational processes on the lattice, which are absent in the undoped sample. In addition we were able to detect the phase transition into the proton ordered phase with both dielectric and NMR measurements close to 62 K.
[1] see O. Yamamuro, et al., Physica B 213, 405 (1995) and references cited therein.
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