Coulomb excitation of 106, 108, 110Pd

Abstract

States in the two-phonon energy region of 106, 108, 110Pd have been investigated via Coulomb excitation, which was effected with 9 and 10 MeV alpha particles and 42–49 MeV oxygen ions. A triplet of states of probable spin-parities 0 +, 2 + and 4 + was observed in each nucleus. Transition rates were extracted from the gamma-ray yields and angular distributions. Although the B(E2) values for transitions from these states to the first 2 + states are large compared to the single-particle estimate, they are consistently smaller than the prediction of the quadrupole-phonon model. The B(E2; 2′ → 0) values are about equal to the single-particle estimate; the B(M1; 2′ → 2) values scatter around 10 −3 × (eħ/2Mc) 2. A third 2 + state was observed in 110Pd at 1212.2 keV. The B(E2) value for its ground state transition is of the order of 1/10 the single-particle value. A state was also Coulomb excited in each nucleus at about 2 MeV. It is attributed to octupole vibrations of the nucleus. The values for ɛ B(E3; 3 → 0), where ɛ is the ratio for decay to the first 2 + state to the total decay, in single-particle units are 25, 19 and 17 for 106, 108, 110Pd, respectively.