In the neutron-deficient 182-186Hg isotopes the so-called intruder states come down in excitation energy to the vicinity of the near-spherical states, yielding the low-lying non-yrast energy levels. The mixing between the states of the coexisting configurations gives rise to transitions with a strong electric monopole component, often referred to as a fingerprint of shape coexistence.
Coulomb excitation studies have been performed at the ISOLDE facility on even mass mercury isotopes and revealed the coexistence of the prolate and the weakly-deformed oblate configurations in these nuclei.
Recent data from decay spectroscopy at ISOLDE indicate very high internal conversion coefficients (ICC) for the 2+→ 2+ transitions, suggesting the strong mixing between the two shape configurations. These new spectroscopic data (i.e. the ICC and the branching ratios) were used in a re-analysis of the Coulomb excitation yields from REX-ISOLDE, providing a unique opportunity to extract the electromagnetic matrix elements and the electric monopole transition strengths ρ2(E0).
The new results from the GOSIA calculations for 182Hg and 184Hg will be presented, compared with theory and interpreted in a two-level mixing model. The very recent decay spectroscopy experiment at the ISOLDE Decay Station (IDS) will be discussed, as well as the future Coulomb excitation experiments at ISOLDE.