Local fluctuations and quadrupolar relaxation: liquid lead alloys

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Abstract
The nuclear spin relaxation rate R has been studied in liquid alloys Pb1-CXC with X=Li, As, Ag, In, Sn, Sb, Te, Au, Tl and Bi at various concentrations C, and for X=In, Sb, Bi as a function of temperature T at C=0.5. The 47 mu s isomer 207mPo, for which the quadrupolar contribution to R, RQ, is dominant, was used as the probe nucleus; it was produced and aligned by the nuclear reaction 206Pb ( alpha , 3n) and the relaxation rate was measured by the perturbed angular distribution technique. For most of the alloys studied here the contribution to RQ due to density fluctuations, RQNN, dominates. Thus these data complement the earlier measurements by the authors of alloys where the concentration fluctuation contribution, RQCC, dominated. They confirm the earlier findings that the magnitude of RQ in alloys is essentially determined by the valence difference between the partner elements and that the long-range components of the interaction are decisive for quadrupolar relaxation (i.e. distances larger than the nearest-neighbour distance).