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

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out the time t' between the second. and third pulses and the ampli-
tude of the resulting echo was monitored with the PGI. The value
of T1D was obtained by plotting In V(t') versus -t'/TID.
5.9 SAMPLE PREPARATION
5.9.1 CUPROUS HALIDES
Three cuprous halides exist in the solid state, CuCl,
CuBr and CuI (CuF is unstable at ordinary temperatures
(73)).
Reagent grade specimens of each of these compounds were used together
with pure specimens of CuBr and Cul obtained from Alfa Inorganic.
In each case about 1 cm3 of polycrystalline material was sealed
into glass phials under vacuum. At low temperatures induced piezo-
electric vibrations in the crystallites caused severe distortion
of the detected decay curves and hampered the determinations of T1.
In order to overcome this problem thin aluminium foil was wound
around the samples to act as a Faraday shield. Mechanical vibrat-
ion in the foil was suppressed by coating the surface with low
temperature varnish.
5.9.2 METALS
The penetration of an rf field into a plane conducting
surface is governed by the equation
H(d) - H(O) exp(-d/U)
where Q, the skin depth, is given by