Résultats et simulation en spectroscopie γ des noyaux déformés : cas des noyaux isomériques et tétraédriques

Abstract : Major part of this work is about the realization and complete analysis of an experiment for study of isomeric states in 138,139,140Nd nuclei. This was performed at Jyväskylä laboratory (Finland) using a fusion-evaporation reaction with 48Ca beam on a thin 96Zr target. Experimental setup consisted in the target position gamma ray detector JUROGAM II which was coupled with the RITU recoil separator and the GREAT focal plane detector array. This particularly well adapted setup permit to manage γ spectroscopy of the interest nuclei around isomeric states. Indeed, we used prompt-delayed matrix to separate rays that come onto isomeric states and these who decay from them. Then, correlations between the two components permit to establish feeding transitions of isomeric states. During this experiment, a new isomeric state was also highlighted in 139Nd with spin 23/2+, which was predicted and interpreted in Cranked-Nilsson-Strutinsky calculation. Finally, very clean time spectra allow to determine precisely life-time of four states in four nuclei. This PhD is also made of a part of analyze on experimental search for fingerprints of tetrahedral symmetry in 156Gd using high fold gamma ray spectroscopy. Thanks to a large number of triple coincidence events, we managed a detailed spectroscopy of this nucleus. Particularly, we found out 13 new transitions in positive parity bands. As a complement of this work, we have done GEANT4 simulations about the detection limit of weak intensity transitions by AGATA multidetector. Indeed, tetrahedral symmetry predicts vanishing of E2 transitions at lower spin states and simulations permit to determine observation limit of these transitions with different version of AGATA
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Autre [cond-mat.other]. Université Claude Bernard - Lyon I, 2010. Français. 〈NNT : 2010LYO10199〉
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Aurélie Vancraeyenest. Résultats et simulation en spectroscopie γ des noyaux déformés : cas des noyaux isomériques et tétraédriques. Autre [cond-mat.other]. Université Claude Bernard - Lyon I, 2010. Français. 〈NNT : 2010LYO10199〉. 〈tel-00639798v2〉



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