NMR investigations of dynamical processes in orientationally ordered and disordered NaCN,RbCN and CsCN |
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Authors: | S Elschner J Petersson |
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Institution: | 1. Fachbereich Physik-Technische Physik, Universit?t des Saarlandes, D-6600, Saarbrücken, Federal Republic of Germany
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Abstract: | The nuclear spin lattice relaxation timeT 1 of the23Na,85Rb,87Rb,133Cs,14N nuclei is measured in NaCN, RbCN and CsCN as a function of temperature below and above the ferroelastic phase transition temperatureT c. BelowT c the behaviour ofT 1 of the alkali nuclei renders possible to determine the flip frequency of the CN molecules and its temperature dependence. AboveT c from the14NT 1 the correlation time τc of the rotational motions of the CN molecules and its temperature dependence is determined. An empirical rule is verified demonstrating that atT c the correlation times take nearly the same values for all cyanides. For the high and low temperature phases one obtains atT c about τc=5·10?13s and τc=5·10?11s, respectively. The results are discussed with respect to the mechanism of the phase transition. |
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