Décroissance $\beta$ et moments magnétiques comme outils pour sonder la structure nucléaire. Etude des noyaux riches en neutrons autour de N=40

Abstract : The evolution of nuclear structure in nuclei far from the β stability line is one of the "hot topics" in modern experimental and theoretical nuclear physics.
The present thesis is devoted to the study of structure of neutron-rich nuclei around N=40. The evolution of the neutron g9/2 orbital with increasing number of neutrons is one of the key points defining the structure of these nuclei at low excitation energy.
We used for this investigation as experimental tools the magnetic dipole moments measurements and the β decay spectroscopy.
For the measurement of the gyromagnetic factor of the 9/2+ isomeric state in 61Fe we have applied the TDPAD method. This method (like most of measurements of nuclear moments) needs an oriented ensemble of nuclei. The orientation of 61mFe was achieved via the fragmentation of 64Ni at 55 MeV/u and the selection of the fragment momentum with the LISE spectrometer at GANIL. The experimental device was specially conceived to preserve the alignment up to the implantation point. The measured value of the g factor was compared with large-scale shell model and Hartree-Fock-Bogoliubov model predictions.
The nuclei studied via β decay were produced by the fragmentation of 86Kr at 58 MeV/u. For the selection of reaction products we used for the first time the LISE2000 spectrometer and for the detection of γ rays four EXOGAM clover detectors. We measured 5 new lifetimes and 4 lifetimes with a higher precision. From the prompt βγ coincidences we identified new states in the daughter nuclei, as it is the case of the first 2+ excited states in 68Fe and 72Ni. The results were compared with the predictions of the large-scale shell model. Other transitions were observed for the first time in βγ decay of 60Ti, 70Fe and 71,73Co.
Document type :
Theses
Nuclear Theory. Université de Caen, 2003. French


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Submitted on : Friday, February 13, 2004 - 1:41:02 PM
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Iolanda Matea. Décroissance $\beta$ et moments magnétiques comme outils pour sonder la structure nucléaire. Etude des noyaux riches en neutrons autour de N=40. Nuclear Theory. Université de Caen, 2003. French. <tel-00004655>

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