Nuclear Quadrupolar Relaxation m Liquid Alloys and Nearest Neighbour Dynamics*

A theory of the quadrupolar relaxation rate, R q , for ideal liquid binary metallic mixtures is presented. The theory predicts cancellation after a few tenths o f a picosecond o f the two and three particle correlation terms in the fluctuation o f the electric field gradient (EFG) for pure metals, and prevailing o f the three particle term for binary mixtures. This is due to the high symmetry in the arrangement o f the atoms around a probe nucleus. The prevailing o f the three particle term in binary systems leads to a longer correlation time (a few picoseconds) o f the fluctuating EFG and explains the experimentally observed higher values o f Rq and their quadratic concentration dependence. The validity o f the theory has been confirmed by experi­ mental data. Deviations for some real systems are discussed.