M. Fauerbach

Role of intruder configurations in 26,28Ne and 30,32Mg

Abstract The energies and reduced transition probabilities B(E2;0g.s.+→2+) for the lowest Jπ=2+ excited states in the neutron-rich radioactive isotopes 26,28 Ne and 30,32 Mg were measured via intermediate energy Coulomb excitation. The data suggest that the interaction between coexisting 0ℏω (normal) and 2ℏω (intruder) configurations significantly perturbs the energy of the 21+ state in 28 Ne, while the data on 26 Ne and 30 Mg can be well understood in the context of 0ℏω configurations alone. Nilsson model calculations suggest that if these nuclei have static axially symmetric deformations, they are prolate.

Mass dependence of the effective isovector charge in the sd-shell

In order to map out a possible mass and isospin dependence of the effective charges in the sd-shell, we performed an intermediate energy Coulomb excitation experiment with the semi-magic, proton-rich nucleus 38Ca. The transition between the first excited state (21+, E*=2206u200akeV) and the ground state (0gs+) was studied, and the reduced transition strength and the proton transition matrix element were deduced. The nucleus 38Ca was chosen for this study, as it is at the upper mass end of the sd-shell, and will together with already existing high precision data for the lower mass end of the shell most clearly show a systematic trend in the effective charges. Our study also helps to fill the void of available high quality data for proton-rich nuclei in this mass region. We compare our data to theoretical shell model predictions with mass dependent, and mass independent effective charges, and to experimental values of the neutron-rich mirror nucleus 38Ar.