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Pear shape in neutron deficient Xe isotopes – Experiment preparation

Internship in experimental nuclear physics

The shape of an atomic nucleus is one of its fundamental properties. It results from a delicate balance between microscopically, macroscopically and symmetry effects. The existence of nuclei with stable deformed shapes was realized early in the history of nuclear physics. The observation of large quadrupole moments led to the suggestion that some nuclei might have spheroidal shapes, which was confirmed by the observation of rotational band structures and since such a shape is symmetric under space inversion, all members of the rotational band will have the same parity. Instead, nuclei that present a reflection-asymmetric shape, as for example octupole, will develop low-lying negative-parity states. The study of the octupole shape is of general interest in nuclear physics because it is related to the topics of parity breaking, dipole moment and reflection asymmetry in nuclear matter. The octupole degree of freedom is used in the description of the alpha clustering in light nuclei, asymmetric fission and cluster emission in heavy compound nuclei. In a recent accepted experiment at the GANIL facility, we will address specific aspects of the collectivity development when approaching the N=Z line in light Xe isotopes by performing a precise lifetime measurement of excited states in 112Xe. Through the lifetime of the 5- state and its branching ratios, we will address the question of the enhancement of the octupole correlation (or pear shape) closer to 100Sn.  In addition, the quadrupole degree of freedom will be investigated through the lifetime of the 2+ and 4+ measured for the first time.

The experiment will be performed in 2018 at the GANIL facility as a part of a larger experimental campaign using the advanced AGATA, NEDA and DIAMANT arrays. This large scale experimental setup will be installed in autumn 2017 at GANIL.

A PhD thesis is proposed in the GANIL group to analyze the experimental data.

The successful candidate will participate in the preparation of this experiment by performing advanced GEANT4 simulations. The candidate will also participate in the 2017 experimental campaign using the AGATA array at GANIL.

Expected skills:

Master in fundamental nuclear physics. C++ programming

This internship leads to a PhD.

Contact : Emmanuel CLEMENT
GANIL, BP 5027, 14 076 Caen cedex 05

Tél. 02 31 45 49 08 Fax : 02 31 45 44 21
e-mail : clement_at_ganil.fr

 

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