Data are presented which indicate the existence of F-spin multiplets for the shape-coexistent intruder states of sequences of nuclei differing by an α particle. We argue that these intruder F-spin multiplets, or, equivalently, F-spin analog states, occur because of their larger and more nearly equal values of ${\mathit{N}}_{\mathrm{\pi }}$${\mathit{N}}_{\nu }$.

• Received 19 November 1990

DOI:https://doi.org/10.1103/PhysRevC.43.R926