München 2019 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 49: Structure and Dynamics of Nuclei IX

HK 49.2: Talk

Thursday, March 21, 2019, 14:30–14:45, HS 14

Shape coexistence in ¹⁷⁸Hg — •Claus Müller-Gatermann, Christoph Fransen, Alfred Dewald, Thomas Braunroth, Alina Goldkuhle, Julia Litzinger, Marcel Beckers, Karl-Oskar Zell, Andrey Blazhev, and Jan Jolie — Institut für Kernphysik, Köln, Deutschland

Since the first application of isotope-shift measurements a sharp shape transition in the ground states of light odd-mass mercury isotopes was observed, and shape coexistence near the Z=82 shell has been an actively studied phenomenon. In neutron-deficient even-mass mercury isotopes a weakly deformed oblate ground-state band is found to coexist with a more deformed prolate band. The prolate states are interpreted as a π(4p-6h) excitation across the Z=82 shell gap. The energy of this prolate structure is lowest in ¹⁸²Hg and shows a parabolic trend of excitation energy as a function of the neutron number. So far ¹⁸⁰Hg is the most exotic nucleus for which lifetimes of excited states are known. These can be used to determine model-independent B(E2)-values and absolute values of deformation employing the rotor model. A breakdown of the shape-coexistence is predicted with further decreasing neutron number. We will present lifetime measurements of excited states in ¹⁷⁸Hg using the Recoil Distance Doppler-Shift (RDDS) method. The recoil-decay tagging (RDT) technique was applied to select the ¹⁷⁸Hg nuclei and associate the prompt γ-rays with the correlated characteristic ground state α-decay.