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

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the temperature range 77-600 K, but no estimates of Debye temper-
atures were included. Indeed their results indicated that for all
three compounds, in the temperature range 77-300 K, the temperature
dependence was best described by a relationship of the form
T1 = cT x where x takes the values 1.7,2.0 and 2.1 for CuI, CuBr
and CuCl respectively. The results for CuCl and CuBr are a reason-
able approximation to the functional form of equation (6.1) for
temperatures above about 10D" However, Guenther and Hultsch's
low temperature experimental Tl values for all three cuprous halides,
and CuI in particular, are shorter than those reported here. This
suggests a possible contribution to the measured spin-lattice relax-
ation times from paramagnetic impurities, perhaps an excess of
copper ions as they themselves note in the case of CuI.
From equation (6.1) it follows that in each of the halides the
ratio. of T1 for
65Cu
to that for
63Cu should be equal to (63Q/65Q)2.
From pure quadrupole resonance measurements (63Q/65Q)2 is equal
to 1.168 ± 0.001(82). Table 6.2 lists the ratio of T1 values for
65Cu and 63Cu as found over the temperature range of the theoretical
fit to Van Kranendonk's function. The results from all three
cuprous halides can be seen to be in satisfactory agreement with
the theory.
Over the limited temperature range of measurements on 79Br
the ratio of T1 values for 81Br and 79Br was 1.35 t 0.10. The
value for (79Q/81Q)2 as derived from direct measurement of th rntin
of the quadrupole moments is 1.433 ± 0.002(83). The agreement bet-
ween the two values is reasonable.
The ratio of the measured T1 values for 63Cu and 81Br
was also independent of temperature. Domngang and Wucher (80)
in CuBr