Shape coexistence in the Pb region: A systematic study of the even ^188-200Hg with GRIFFIN

Shape coexistence is a unique phenomenon of the atomic core in which the nucleus assumes intrinsically different shapes in a small energy range. Two of the main model-independent probes used to study this phenomenon are the measurement of transition strengths, in particular B(E2) and ρ²(E0).

The n-deficient Pb region is characterized by clear examples of shape coexistence. A large isotope shift was observed in the light Hg isotopes that expresses the differently shaped potentials existing in these nuclei causing deformation [1]. Only recently a COULEX experiment observed shape coexistence for ^182-188Hg  [2]. Still, there are plenty of key elements not measured yet, especially in the transitional isotopes between the stable ²⁰⁰Hg and the midshell ¹⁹⁰Hg.

A systematic study on the decay of the n-deficient ^188-200mTl into Hg was done using GRIFFIN, at TRIUMF-ISAC. Key results of the experiment will be presented, with special emphasis on the lifetimes of the first 2⁺, 4⁺ and some non-yrast states. High statistics results on conversion-electrons, angular correlations and precise branching ratios, which greatly help in forming a complete picture of the band structure of these isotopes, will be discussed.

[1]Phys. Let. B, 38:308, 1972.

[2]Phys. Rev. Lett. 112, 162701, 2014.