Investigation of a 290 ns − isomeric state in 117Sb and evidence for shape coexistence

A 290 ns 23 2 − isomeric state has been identified at 3230.6 keV excitation in 117Sb populated in the 115In(α, 2n) reaction at Eα = 27 MeV. The decay scheme was investigated by pulsed beam γ-ray spectroscopy. From TDPAD measurements on molten and solid metallic In targets, the g-factor, g = +0.437 (5), and a lower limit for the electric quadrupole moment, ¦Q¦ > 1.7 b , have been determined. The experimental data indicate that the 1 g 9 2 −1 , proton shell-model intruder excitation responsible for coexistence in odd-mass Sb nuclei is present in the structure of some high spin states in 117Sb. The [π(1 g 9 2 −1 ) ⊗ ν(1 h 11 2 2 d 3 2 ) 7 − ] 23 2 − configuration has been assigned to the isomeric state on the basis of the measured g-factor. The enhanced E2 isomeric transition probability and the lower limit established for the electric quadrupole moment indicate an increased collectivity associated possibly with a deformation of the 290 ns 23 2 − isomeric state in 117Sb.