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

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 coexistin g 0 (h) over bar omega (normal) and 2 (h) over bar omega (intruder) configu rations significantly perturbs the energy of the 2(1)(+) state in Ne-28, wh ile 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.