Spectroscopic Isotope Shift and Nuclear Polarization

Staggering of term values of odd isotopes with respect to those of the even ones is discussed. The validity of the static picture of nuclei as applied to their interaction with electrons is examined. It is found that the partial excitation of nuclei by atomic electrons results in polarization effects which lower the energy by amounts comparable to the observed irregularities and staggering. Correlations of observed shifts with the formation of stable shells are also discussed in a tentative way.