Structure effects in the charge radius of spherical nuclei

Abstract

Isotope and isomer shifts of the nuclear charge radius are calculated using the pairing plus quadrupole model. To accomplish this, the nuclear system is divided into a core plus a few valence particles. Monopole polarization of the core by the particles is taken into account in a phenomenological manner by assuming that the particles interact independently with the core. Quadrupole polarization of the core by the particles is estimated with the help of an effective quadrupole charge determined by fitting B(E2) transition rates of even-mass nuclei. The independent particle configuration of the valence nucleons is admixed by the pairing plus quadrupole interaction and the resulting wave functions are used to calculate isotope and isomer shifts of the charge radius. The results of even-mass to even-mass isotope shifts show good agreement with experiment, while the odd-even staggering effects observed in the isotope shift cannot be obtained. Good agreement is obtained for the few isomer shifts which have been measured.