Regensburg 2010 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 24: Glasses and Glass Transition I (jointly with DY and DF)

CPP 24.5: Vortrag

Mittwoch, 24. März 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.