Lifetime measurements and shape coexistence in 97 Sr

Delayed γ 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 97Sr were measured using the fast-timing technique. The nucleus 97Sr exhibits shape coexistence and is located exactly at the border of the spherical (N≤58) and deformed (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.