Zentrallinien-NMR an stark quadrupolar gestörten Kernen in molekularen und ionischen Kristallen
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Date
2022
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Abstract
Dynamische Prozesse in molekularen und ionischen Kristallen werden mithilfe der Zentrallinien-NMR an den stark quadrupolar gestörten Kernen 11B und 17O untersucht. Dazu werden 11B-Relaxationszeiten in Orthocarboran gemessen und diese bezüglich der Moleküldynamik interpretiert. In Natriumnitrat wird der Dreiplatzsprung des planaren Nitrations mittels 17O-NMR untersucht. Diese Dynamik wird mit NMR-Spektren, stimulierte Echos und Relaxationszeiten untersucht. Mithilfe von Simulationen können aus gemessenen Spektren Sprungraten bestimmt werden. Ein 17O Hochtemperaturspektrum von Natriumnitrat wird mithilfe gemittelter Tensoren beschrieben. Die Reorientierungsdynamik in Natriumnitrat weist eine Aktivierungsenergie von EA = 0,38 eV auf. Als Beispiel für einen Tetraedersprung wird Kaliumpermanganat mithilfe der 17O-NMR untersucht. Hier wird mithilfe von stimulierten Echos eine Aktivierungsenergie von EA = 0,35 eV für die Sprünge der Sauerstoffatome bestimmt. Auch für Kaliumpermanganat werden die Relaxationszeiten gemessen und bezüglich der Reorientierungsdynamik interpretiert.
Dynamic processes in molecular and ionic crystals are investigated using central line NMR on the strongly quadrupolar perturebed nuclei 11B and 17O. For this purpose, 11B relaxation times are measured in orthocarborane and interpreted in terms of molecular dynamics. In sodium nitrate, the three side jump of the planar nitrate group is studied by 17O NMR. The dynamics of the ion are investigated by NMR spectra, stimulated echoes and relaxation times. Combining the results from simulations with measured spectra, jump rates are determined. A 17O high temperature spectrum of sodium nitrate is described using averaged tensors. The reorientational dynamics in sodium nitrate has an activation energy of EA = 0.38 eV. As an example for a tetrahedral jump, potassium permanganate is studied using 17O NMR. Here, with the aid of stimulated echoes, an activation energy of EA = 0.35 eV is determined for the jumps of oxygen atoms. The relaxation times are also measured for potassium permanganate and interpreted with respect to the reorientational dynamics.
Dynamic processes in molecular and ionic crystals are investigated using central line NMR on the strongly quadrupolar perturebed nuclei 11B and 17O. For this purpose, 11B relaxation times are measured in orthocarborane and interpreted in terms of molecular dynamics. In sodium nitrate, the three side jump of the planar nitrate group is studied by 17O NMR. The dynamics of the ion are investigated by NMR spectra, stimulated echoes and relaxation times. Combining the results from simulations with measured spectra, jump rates are determined. A 17O high temperature spectrum of sodium nitrate is described using averaged tensors. The reorientational dynamics in sodium nitrate has an activation energy of EA = 0.38 eV. As an example for a tetrahedral jump, potassium permanganate is studied using 17O NMR. Here, with the aid of stimulated echoes, an activation energy of EA = 0.35 eV is determined for the jumps of oxygen atoms. The relaxation times are also measured for potassium permanganate and interpreted with respect to the reorientational dynamics.
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Keywords
NMR, Festkörper NMR, Quadrupolkerne, Dynamik in Festkörpern