FIELD SHIFTS IN HAFNIUM-II

By means of classical interference spectroscopy, using enriched isotope samples, the isotope shift between Hf-178 and Hf-180 has been measured for 33 transitions in the Hf II spectrum. For the pure Russell-Saunders terms 5d(2)6s 4F and 2F the parametric analysis yields a field-shift difference of 17(2) mK produced by the second-order interaction of the electrostatic operator and the field-shift operator. Semi-empirical calculations based on the non-relativistic Hartree-Fock method reproduce this value as well as the experimental field shifts if a factor of 1.68(6) is used to scale the ab initio electron densities at the nucleus. The corresponding factor for the Hf atom is much smaller. This leads to a re-evaluation of screening ratios for Hf and to a more accurate value of the nuclear parameter lambda-178,180(HF) = 0.072(4) fm2.