Recherche de la Vibration Géante de Paires & Mesure du temps de vie du premier état excité 2+ du 74Zn par méthode plunger.

Abstract : My PhD consist of two independent parts. Firstly I participated in and analyze an experiment done at GANIL. This experiment was performed to study the evolution of the structure of neutron rich zinc isotopes, by measuring the life time of the first excited 2+ state of 74Zn by plunger technique. A secondary radioactive beam of 74Zn at 34MeV/u was used. This beam was produced by in-flight fragmentation using the first half of the LISE spectrometer, whereas the second half of the spectrometer was used to identify the final reaction product. The EXOGAM array and the differential Plunger technique provided information on the in-beam gamma spectroscopy and life time of the excited states from picoseconds to tens of picoseconds. We extracted a life time of the first excited 2+ state of 74Zn of t = 29(3) ps. A comparison with the Coulomb excitation experiment results done at ISOLDE [Wall 09], allowed us to extract the first quadrupole moment of a neutron rich zinc isotope, where the g9=2 neutron orbital (with more than 40 neutrons), starts to be filled. The second part of my PhD was focused on the realization and the analysis of two transfer reactions (120Sn(p; t)118Sn and 208Pb(p; t)206Pb) done at iThemba LABs (Cape Town - South Africa). These two experiments were performed to identify the Giant Pairing Vibration (GPV), using the Missing Mass Method. This collective mode which is analogous to a giant resonance corresponds to a coherent excitation of pairs in the next major shell above the Fermi level. This giant resonance, predicted by many theoretical calculations (QRPA [Khan 09] and TDHFB [Avez 08]), still is, despite some early efforts, without any conclusive experimental confirmation. The two experiments were performed using optimal conditions to observe the GPV : - a proton beam at low energy (50 and 60 MeV), to populate mainly low spin states, - a spectrometer (K600) used at lowest angle (7° and 0°) in order to get the maximum of the L=0 (pairing vibration) transfer cross section. Although we did not observe any clear evidence of the GPV, we were able to set an upper limit on the two neutrons transfer cross section populating the GPV in these nuclei.
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Nuclear Theory. Université Paris Sud - Paris XI, 2010. French


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Submitted on : Friday, September 9, 2011 - 2:10:46 PM
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B. Mouginot. Recherche de la Vibration Géante de Paires & Mesure du temps de vie du premier état excité 2+ du 74Zn par méthode plunger.. Nuclear Theory. Université Paris Sud - Paris XI, 2010. French. <tel-00621090>

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