Nuclear quadrupole interaction in metals: Experiments, calculations, models

The results obtained from the investigation of the nuclear quadrupole interaction in metals, mostly at impurities, are reviewed. Examples of the experimental work are primarily taken from studies at ISOLDE/CERN. For the determination of the nuclear quadrupole moments Q, necessary to extract the electric field gradients from the measured coupling constants, various methods have been employed. Band structure calculations both for pure systems and also for impurities have been performed with the FLAPW density functional method. The theoretical understanding achieved for sp-impurities in simple noncubic metals is described.