Transient-field g-factor measurement of the first 2+states in the N=82 nuclei 140Ce, 142Nd and 144Sm

The g-factor of the first 2+states in three stable N=82 nuclei, 140Ce, 142Nd and 144Sm, have been measured using the transient magnetic field technique. The levels under study were Coulomb excited with 110–116 MeV 32S beams and spin precession after passing a thin polarized iron foil was measured. The field strength has been checked using the first 2+state in 148Sm as internal calibration. The obtained values were 0.97 (9), 0.84 (7), 0.76 (11) for 140Ce, 142Nd and 144Sm, respectively. These remarkably lower values with respect to shell-model predictions in a proton subspace are explained in terms of neutron core excitation by quasiparticle random-phase-approximation calculations.