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Spectroscopie $\gamma$ des noyaux riches en neutrons autour de N=20

Abstract : There is an island of inversion around $^{32}$Mg (12 protons, 20 neutrons) in contradiction with a shell closure N=20. It means a coexitence of spherical and deformed shapes.
This work is devoted to the study of $\gamma$ ray spectroscopy for nuclei in this region, based on an experiment done at GANIL with a composite secondary beam produced by fragmentation. The originality of the method used here lies in the possibility to study simultaneously several nuclei, and for each of them to explore sevral reaction channels. The VAMOS spectrometer was used for the identification of the ejectiles. The $\gamma$-rays were detected with EXOGAM, a germanium clover array. The detectors used before and after the target allowed for a unique identification and a selection of the reaction channel : inelastic scattering, transfer and fragmentation reaction. In this thesi the following nuclei were studied : $^{28}$Ne, $^{30-32}$Mg, $^{31-34}$Al, $^{33-35}$Si, $^{35}$P. New $\gamma$-rays have been observed. The $\gamma$-rays angular distributions and $\gamma$-$\gamma$ angular correlations have been measured for some transitions. Assignment of spins and parities has been proposed for some states. In particular, in n{34}$Si, the $3^-$ assighment is confirmed and a new candidate for the second $0^+$ has been proposed. In $^{32}$Mg, the state at 2.321 MeV is confirmed, for which conflicting assignment existed, is deducted from the present data as a $4^+$, and a $6^+$ state is proposed.
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https://tel.archives-ouvertes.fr/tel-00193046
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Submitted on : Friday, November 30, 2007 - 1:54:30 PM
Last modification on : Thursday, February 1, 2018 - 1:33:10 AM
Long-term archiving on: : Monday, April 12, 2010 - 5:37:49 AM

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  • HAL Id : tel-00193046, version 1

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Marie Gelin. Spectroscopie $\gamma$ des noyaux riches en neutrons autour de N=20. Physique Nucléaire Expérimentale [nucl-ex]. Université de Caen, 2007. Français. ⟨tel-00193046⟩

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