# Shape coexistence in the neutron-deficient lead region: A systematic study of lifetimes in the even-even $^{188-200}$Hg with GRIFFIN

## TL;DR

This study measures lifetimes of excited states in neutron-deficient $^{188-200}$Hg isotopes using advanced gamma timing techniques, providing data that supports the onset of state mixing in $^{190}$Hg and compares well with theoretical models.

## Contribution

It offers the first systematic lifetime measurements of multiple states in $^{188-200}$Hg using fast timing, enhancing understanding of shape coexistence in this region.

## Key findings

- Confirmed the onset of state mixing in $^{190}$Hg.
- Provided precise B(E2) values for comparison with models.
- Supported the presence of shape coexistence phenomena.

## Abstract

Lifetimes of $2^+_1$ and $4^+_1$ states, as well as some negative-parity and non-yrast states, in $^{188-200}$Hg were measured using $\gamma-\gamma$ electronic fast timing techniques with the LaBr$_3$(Ce) detector array of the GRIFFIN spectrometer. The excited states were populated in the $\epsilon/\beta^+$-decay of $J^\pi =7^+/2^-$ $^{188-200}$Tl produced at the TRIUMF-ISAC facility. The deduced B(E2) values are compared to different interacting boson model predictions. The precision achieved in this work over previous ones allows for a meaningful comparison with the different theoretical models of these transitional Hg isotopes, which confirms the onset of state mixing in $^{190}$Hg.