MEASUREMENT OF ELECTRIC FIELD GRADIENT AROUND IMPURITIES IN CERTAIN ALLOYS OF ALUMINUM

Using field-cycling double resonance, we have measured the quadrupolar couplings at different neighboring sites around seven impurities in aluminum. For the Ag, Mg, and Zn alloys, the field gradients at the nearest-neighbor sites are found to be greater than that at the next sites, while for the In, Ga, Ge, and Si alloys, the field gradients are greatest at the second-neighbor site and have a surprisingly high value. A study of the method is presented: In particular, we discuss the role of the cross-relaxation process between the quadrupole reservoir of the spins on the same shell around the impurity and the dipolar reservoir of the whole system. © 1969 The American Physical Society.