Speaker
Description
Shape coexistence in the neutron-deficient lead region around $N \approx 104$ has been discovered in different nuclei especially in the mercury isotopes, where a staggering effect was found between even- and odd-mass nuclei using charge radii measurements [1,2]. In addition the study of the even-even $^{182,184,186,188}$Hg isotopes via Coulomb excitation reactions showed a mixing of weakly deformed oblate and more deformed prolate configurations which coexists at low excitation energies [2,3].
To investigate collective behavior of low-lying states on top of the $(1/2^-)$ ground-state in $^{185\mathrm{g}}$Hg and the different deformed ($13/2^+$) isomeric state in $^{185\mathrm{m}}$Hg, a Coulomb excitation experiment was performed at HIE-ISOLDE. The complete separation of the isomer and ground state in $^{185}$Hg using RILIS offers an unique opportunity to study the weakly oblate deformed and strongly prolate deformed structures. The $^{185\mathrm{g,m}}$Hg beams were accelerated onto $^{120}$Sn and $^{48}$Ti targets with an energy of 4 MeV/u. The emitted $\gamma$ rays were detected utilising the Miniball array in coincidence to the scattered particles measured in the DSSSD detector. Preliminary results of excited states of $^{185\mathrm{g,m}}$Hg will be shown for both targets. Excited states in $^{185\mathrm{g}}$Hg were populated and identified up to a spin of $25/2^-$. The signature partner band of the ground-state band was observed and established through the identification of several mixed $M1+E2$ transitions between both. Comparisons with neighboring odd-mass Hg and Pt isotopes reveal similar band structures. The preliminary GOSIA analysis to extract deformation parameters will be presented.
[1] J. Bonn et al., Zeitschrift für Physik A Hadrons and Nuclei 276(3), 203 (1976)
[2] N. Bree et al., Physical Review Letters 112, 162701 (2014)
[3] B. Marsh et al., Nature 14, 1163 (2018)
[4] K. Wrzosek-Lipska et al., The European Physical Journal A 55, 130 (2019)
This project was supported by BMBF Projects 05P21KCI1, 05P24KCI1 and by the UK Science and Technology Facilities Council. The project has received funding from the European Unions Horizon Research and Innovation programme under Grant Agreement No. 101057511.
