Lifetime measurements and shape coexistence in Sr-97

Delayed gamma rays from neutron-rich A = 97 fission fragments were measured using the Lohengrin spectrometer at the high-flux reactor of the Institut Laue-Langevin in Grenoble. Several lifetimes of excited states in Sr-97 were measured using the fast-timing technique. The nucleus Sr-97 exhibits shape coexistence and is located exactly at the border of the spherical (N = 60) ground-state deformation. It is of particular interest to study the shape-coexisting structures at the spherical-deformed border (N = 59). The determined lifetimes within this work are compared to an interacting boson-fermion model calculation that is based on the microscopic energy density functional to provide a better understanding of the spherical-deformed border in strontium isotopes