Electric Quadrupole Field in `HfOCl2·8H2O' Crystals

The perturbed angular correlation of 133-482 keV cascade in Ta 181 has been measured with the source in the form of HfOCl 2 ·8H 2 O crystals with magnetic fields up to 20 kG. The experimental values of G 2 and G 4 , when compared with the theoretical values of Abragam and Pound, give the quadrupole interaction frequency ω E 0 =(118±20) Mc/s. The experimental values obtained under the presence of external magnetic field show the effect of time dependent fields present in this crystal.