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

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from Cerac Inc. (USA). The stated purity was 99.999% and the
particle size was less than 40 um, as compared to the value of
the skin depth at 13MHz of 30 Um.
8.4.2 KNIGHT SHIFT DETERMINATIONS
Previous room temperature estimates of the isotropic
Knight shift of cadmium metal as performed against aqueous solut-
ions of cadmium chloride and cadmium nitrate have yielded values
in the range 0.39-0.43%(120,129-134). Recently however it has been
shown (135)
that there exists a considerable range of chemical shifts
between the cadmium resonances from different aqueous solutions of
cadmium salts. These chemical shifts vary not only between the
different salts but also between different concentrations of the
same salt. The measured Knight shift depends therefore upon the
particular reference sample chosen.
The Knight shift of both isotopes was measured here using the
double rotor box described in Section 5.4. Rotors containing the
solid powder slugs were spun at speeds up to 4.5 kHz in a magnetic
field of 1.45 T. By employing the DL 102 signal averager the ref-
erence frequency and phase of the PSD could be adjusted so as to
measure the resonance frequency of the metal to an accuracy of ±20 Hz.
Preliminary measurements were performed against saturated solutions
of CdC12. The signal strengths were extremely poor so in order to
shorten the spin-lattice relaxation time the salt was dissolved in
a 1% molar aqueous solution of MnCI2. Against this reference and
at a temperature of 300 K the Knight shifts for 111Cd and 113Cd were
measured as 4155 ±4 ppm and 4154 ±4 ppm. The errors quoted arise
largely from the uncertainty in defining the centre frequency of the