On the character of three 8⁺ states in ¹⁹²Pb

Abstract

Three low-lying 8⁺ states have been identified in ¹⁹²Pb . A newly observed cascade of $\gamma$ -rays built directly on the 8⁺ ₁ state is compared to the previously identified, weakly rotational band above the 11^- $\pi$ i _13/2 , h _9/2 isomer in the same nucleus, and to analogous structures in ¹⁹⁴Pb . The similarity of all four structures lends support to the suggestion that the 8⁺ ₁ configurations are of a similar oblate deformation to the 11^- isomers. The excitation energies of all three 8⁺ states in ¹⁹²Pb and ¹⁹⁰Pb are compared to systematics. The possibility that one of the 8⁺ states in ¹⁹²Pb is associated with a prolate shape is discounted.