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

The enemies and reduced transition probabilities B(E2;0(g.s.)(+) --> 2(+)) for the lowest J(pi) = 2(+) excited states in the neutron-rich radioactive isotopes Ne-26,Ne-28 and Mg-30,Mg-32 were measured via intermediate energy Coulomb excitation. The data suggest that the interaction between coexisting 0 (h) over bar omega (normal) and 2 (h) over bar omega (intruder) configurations significantly perturbs the energy of the 2(1)(+) state in Ne-28, while the data on Ne-26 and Mg-30 can be well understood in the context of 0 (h) over bar omega configurations alone. Nilsson model calculations suggest that if these nuclei have static axially symmetric deformations, they are prolate. (C) 1999 Published by Elsevier Science B.V. All rights reserved.