NNR IN RAPIDLY ROTATED METALS By - Nottingham eTheses ...

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Although most metals of the lanthanide series possess at least
one isotope with a magnetic moment, relatively little work has been
done on the NMR spectra of the rare earth metals. This is presum-
ably due in part to the difficulty in obtaining specimens of a
sufficiently high purity. Nevertheless it is worth noting that
considerations such as those described above rule out all but
europium, ytterbium and perhaps lanthanum as specimens which might
profitably be subjected to the magic angle rotation technique.
With these metals, however, there is also the additional complicat-
ion that they are readily oxidized and hence have to be kept from
contact with the air.
With the experimental system available the list of metals,
apart from the rare earths, which could usefully be investigated
by rotation at the magic angle was found to be reduced to six:
copper, tin, aluminium, cadmium, vanadium and niobium. Investi-
gations have already been carried out on the effect of specimen
rotation on the NMR spectra of copper(59) and ß-tin(116). Hence,
since the work on aluminium has been described in the preceding
chapter, detailed in this chapter are a series of measurements on
powdered specimens of vanadium, niobium and cadmium. Although
samples of all three metals were spun at speeds up to 5 kHz, the
static linewidths of vanadium and niobium were found to be too
large to be affected by spinning rates of this magnitude.
8.2 VANADIUM
Vanadium powder with a stated purity of 99.5% and a particle
size of less than 75 um was obtained commerically from Koch-Light
Laboratories. Because of the difficult nature of the annealing