Coulomb excitation of the even- A cadmium nuclei

Abstract

Coulomb excitation of the first 2 + states of the even- A cadmium nuclei was produced by 2.7 and 3.0 MeV protons to obtain accurate B(E2, 0 → 2) values (absolute error ±4%). The B(E2, 0 → 2) obtained for 114Cd is (0.576±0.023) e 2 b 2 and agrees well with the value of (0.567±0.018) e 2 · b 2 by Glenn and Saladin but disagrees with the recent value of (0.509±0.009) e 2 · b 2 by Simpson et al. obtained in the course of their measurement of the static quadrupole moment of the 2 + state. Ge(Li) detectors have been used to measure the angular distribution of γ-rays following Coulomb excitation with 11 MeV 4He ions in 106–116Cd. The angular distributions of the γ-rays from the 2′ → 2 transition by direct E2 Coulomb excitation have been obtained with an accuracy sufficient to establish the magnitude and sign of δ ≡ 〈2‖ M( E2)‖2′〉/ 〈2‖ M( M1)‖2′〉 . The values for δ are near −1.5 for 108,110,114,116Cd, −(8.4 −4.7 +100) or −(0.6±0.2) and −(3.5 −0.8 +0.9) or −(0.87±0.10) for 106Cd and 112Cd, respectively. The B(M1 2′ → 2) are large, being between (0.4 and 3) × 10 −2(e h ̵ /2 Mc) 2 . In addition, the angular distributions of the γ-rays from the 2″ → 2 transitions in 112Cd and 114Cd were determined and are consistent with two positive values of δ. Improved values for the branching ratio of cascade/ crossover transitions for the decay of the 2′ and 2″ states have been obtained. With this information the ratios B(E2, 2′ → 2)/ B(E2, 2 → 0) have been revised downward 10 to 40% from those given in a previous paper. The 2′ state in 106Cd and 108Cd is above the 4 + state in energy.