Hyperfine depolarization

Another unusual feature of CuCl and CuBr is the presence of two Mu centers with nearly identical isotropic hyperfine parameters. One of the centers, Mu7, occurs preferentially at low temperatures but is metastable as evidenced by a thermally activated transition to the second center, Mu77 (see Fig. 13). As the temperature increases, the effects of this transition first appear as an increse of the Mu7 depolarization rate (lifetime broadening). At higher temperatures the transition becomes fast enough so that... 

Let us consider the hyperfine depolarization effect caused by the presence of nuclear spin that is not oriented or aligned by light but acts as a randomly oriented flywheel to reduce the average polarization of fluorescence. The emission process can be effected by the presence of nuclear spin J, even if the hyperfine structure is unresolved by the detection apparatus. For this purpose one has to multiply each polarization moment fq in Eq. (5.34) by a coefficient g(K which is equal to [177, 402]... 

Since 1 for J 3> I the hyperfine depolarization must be considered only if J is comparable to I. 

The /i+ moderation processes involve dominantly electro static interaction and there is no muon depolarization in strong axial magnetic fields (B 0.16 T) [10]. At low fields the tof = 0 atomic states are populated to 50 % which means a corresponding reduction of the polarization due to the muon spin oscillation at the hyperfine frequency Avhfs-... 

A fuller treatment of hyperfine depolarization may he found in Zare (1988), pp. 239-241. 

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