Shape Coexistence in ¹⁵¹Gd

Abstract

<p>The level structure of the odd-A transitional nucleus ¹⁵¹Gd has been studied by means of the ¹⁴⁹Sm(α,2n)¹⁵¹Gd reaction through ϒ-ray singles, ϒ-ray angular distributions, ϒ-ϒcoincidence and conversion electron measurements.</p> <p>A number of rotational band-like structures have been observed, indicating that the nucleus is deformed when produced in this reaction. A rotational band built on one of the states populated in the reaction conforms well to present theory and indicates that the nucleus has a large deformation when this state is populated. The order bands are not well explained by present theory, although a much smaller nuclear deformation is indicated.</p> <p>The implication is that the Nilsson model, in its present stage of development, is inadequate for treating nuclei such as ¹⁵¹Gd. Further theoretical work is necessary particularly in the treatment of multiple particle states where j is not a good quantum number and the core is not a rigid rotor.</p>