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| Titel |
Coil homogeneity and the effect of rotor filling on the spectral resolution |
| VerfasserIn |
A. E. Berns, P. Conte |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250020955
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| Zusammenfassung |
| Spectral resolution depends upon the length (N) of the transform interval: N=F/Δf, where Δf
is the smallest frequency difference which can be distinguished at a given sampling frequency
F. Δf depends on the signal width, which, in turn, is influenced by the relaxation time of the
sampled signal. Relaxation time is affected by the external magnetic field and the applied
pulse sent to the sample through the transmitter/receiver coil. The pulse length homogeneity
throughout this coil is a major factor affecting NMR resolution and also the sensitivity of the
measurement. So far, this fact is only considered when small sample amounts are
used, where care should be taken to place the sample in the centre of the coil to
maximize the signal. However, no work has been presented as to how much the top
and bottom part of the sample might worsen the spectral resolution of the NMR
spectrum.
In this work NMR experiments have been performed where constant sample amounts of 2
mm fill height have been measured at different heights in the rotor. At every height the
absolute signal intensity and the half height width of the signals were determined as
indicators for sensitivity and spectral resolution. Furthermore relaxation times at different
heights were determined. Subsequently a rotor was filled with humic acid in the determined
optimal region and compared to spectra of a fully filled rotor and a rotor where the top and
bottom areas were filled to determine the contribution of the centre and outer regions in the
rotor. |
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