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.

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