Prolate-to-oblate shape phase transitions in neutron-rich odd-mass nuclei

Abstract

We investigate the prolate‑to‑oblate shape phase transitions in the neutron‑rich Pt, Os, and Ir nuclei in the mass region A ≈ 190. The IBM-fermion Hamiltonian, used for odd‑mass ^185–199Pt, ^185–193Os, and ^185–195Ir, is partly derived from microscopic HFB calculations with the Gogny‑D1M interaction; remaining parameters are fitted to experimental odd‑mass spectral data. Calculated observables—especially low‑energy excitation spectra and effective deformation parameters—indicate a systematic shape transition with neutron number across all three isotopic chains, mirroring trends in neighboring even–even nuclei.