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Recherche de la symétrie tétraédrique dans le noyau 156Gd par spectroscopie γ

Abstract : Theoretical calculations using realistic mean-eld method suggest the existence of nuclear shapes with tetrahedral and/or octahedral symmetries in some rare earth nuclei around 156Gd and 160Yb. In nuclei with exact tetrahedral symmetry, the E2 intra-band transitions are predicted to vanish completely or to be very weak. This work is devoted to an experimental research of the tetrahedral symmetry in the nucleus 156Gd. An experiment has been carried out with the JUROGAM - rays detector at Jyväskylä by using the fusion - evaporation reaction 154Sm(, 2n)156Gd. In analysis, the branching ratios of two parity negative bands were determined, the angular distribution has been analyzed to determine the nature of one inter-band transition between these two bands. The transitions strength ratios determined are of the same order of magnitude as previous experiments, and some upper limits have been established for the lowest spin. The missing of the E2 transitions below the (I^π≺9)states in the odd spin parity negative band were conrmed. The results of this work reinforced the hypothesis of the tetrahedral symmetry in the nucleus 156Gd. -ray spectroscopy is the major tool used for this work. Detection principles and -ray simulations are detailed in the document. The simulation, based on realistic events, has been realised to compare the response function of two multidetectors EUROBALL and AGATA. The results show that under certain conditions the rst phase of AGATA (demonstrator) is also a tool to search for rare events
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Submitted on : Tuesday, February 1, 2011 - 4:19:07 PM
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  • HAL Id : tel-00561660, version 1

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Quang Tuyen Doan. Recherche de la symétrie tétraédrique dans le noyau 156Gd par spectroscopie γ. Autre [cond-mat.other]. Université Claude Bernard - Lyon I, 2009. Français. ⟨NNT : 2009LYO10202⟩. ⟨tel-00561660⟩

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