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

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the corresponding values of d (T1Z/T1D). The errors quoted again
refer to the distribution of values obtained in each case.
Using the same technique Tunstall and Brown (72) measured T1D
and 6 in samples of pure filed annealed powder over the temperature
range 1.3-295 K. Although their measured 6 value at room temper-
ature was 2.25 they interpreted the recorded temperature dependence
as indicating a contribution due to a quadrupolar thermal reservoir
and concluded that the value of 6 relating the true dipolar relaxat-
ion time to Tlz was in fact 2.15 ± 0.07. From room temperature
measurements of the spin-lattice relaxation in the rotating frame
113
(Tlp) Fradin and Rowland(d
) measured 6 as 2.65. Pifer
a CW slow passage saturation method and obtained a value of
(114) used
2.07 ±'0.02 at 273 K. At liquid helium temperatures experimental
values of 6 have been consistently greater than 2.5(18'72,115)
The measurements reported here indicate that the method of sample
preparation contributes to the measured values of T1D and hence Ö.
The recorded 6 value for the filed powder (c) is somewhat lower than
Tunstall and Brown's uncorrected value from a similar sample at 295 K.
On the other hand the value for powder (a) agrees with their corrected
value to within experimental error and is in excellent agreement with
that reported by Pifer. Such an occurrence may well be fortuitous,
however, because no details of Pifer's samples are included. With
the simplifying assumption of a spherical Fermi surface the theoret-
ical value for 6 is 2.06(72). The experimental value for the pure
sprayed powder therefore fits present theory very well. It remains
to be seen whether this value is independent
predicts.
of temperature as theory