[en] 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 Fe⁶¹ we have applied the TDPAD method. This method (like most of measurements of nuclear moments) requires an oriented ensemble of nuclei. The orientation of Fe^61m was achieved via the fragmentation of Ni⁶⁴ 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 Kr⁸⁶ 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 Fe⁶⁸ and Ni⁷². 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 Ti⁶⁰, Fe⁷⁰ and Co^71,73. (author)

[en] We report preliminary results from ultra-fast time-delayed γγ(t) measurements on exotic nuclei just below ¹⁰⁰Sn. The measurements were performed at the LISE spectrometer in GANIL. Nuclei of ⁹⁴Ru and ⁹⁶Pd were populated in the isomeric states via the fragmentation of energetic ¹¹²Cd beam. Preliminary lifetime or lifetime limits are reported for the 6⁺, 4⁺, and 2⁺ states in ⁹⁶Pd and the 4⁺ and 2⁺ states in ⁹⁴Ru. These results indicate an unexpected and strong quenching of the B(E2) strength for the 4⁺ to 2⁺ E2 transition in ⁹⁶Pd in comparison with model predictions and the equivalent B(E2) strength in ⁹⁴Ru. The sequence of quenched B(E2) rates for the 8⁺ → 6⁺ E2 transition in ⁹⁴Ru, 4⁺ → 2⁺E2 transition in ⁹⁶Pd and for the 8⁺ → 6⁺ E2 transition in ⁹⁸Cd, seems to represent a systematic pattern along the N=50 neutron number just below Z=50 and could imply a weak N=50 shell closure when approaching the doubly magic ¹⁰⁰Sn. (author)

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[en] An island of isomers have recently been observed on both sides of the N=40 shell below the Ni isotopes. Isomeric states in the 65Fe and 67Fe allow the knowledge of the single particle structure around the g9/2 shell. Moreover, the excitation energy of the first 2+ and 4+ states in the 68Fe have been established by β-γ correlation. The evolution of the structure of the Fe isotopes going far away from the valley of stability is, for the first time, given for N>40

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[en] We studied the performances of the LaBr₃:Ce scintillator when optically coupled to NaI:Tl and CsI:Na in a Phoswich detector for the R and D phase of the gamma ray calorimeter PARIS (Photon Array for the studies with Radioactive Ion and Stable beams). This detector has the purpose to measure γ-energies in a wide range (100 keV–40 MeV), and it will be used principally as a part of the SPIRAL2 instrumentation at GANIL. In this communication we report on the study of the light yield and energy resolution for gamma detection realized by coupling the phoswiches with various photomultiplier tubes, providing different characteristics. We were interested in investigating the possible degradation of the scintillation light produced by the LaBr₃:Ce due to the presence of NaI:Tl/CsI:Na crystals, before being detected on the photocathode. For this purpose we realized all the measurements employing a standard ADC and QDC read-out system leading the possibility to perform a gate-based event selection. In this study we measured an energy resolution of 4.6% with an uncollimated ¹³⁷Cs source for a 50.8×50.8×50.8 mm³ LaBr₃:Ce coupled to a 50.8×50.8×152.4 mm³ NaI:Tl. This value is 30% bigger than the energy resolution measured for a 50.8×50.8×101.6 mm³ stand-alone LaBr₃:Ce but still in the specifications for the PARIS collaboration physics list.

[en] In the experiment performed at GANIL (France) we have studied the β-delayed particle emission of the T_z = -3/2 ³³Ar and T_z = -2 ³²Ar proton emitters. Protons are emitted within the wide window (around 10 MeV) of excited states in ³³Cl and ³²Cl feeding the ground and the excited states of ³²S and ³¹S. Proton-γ coincidences have been used to determine the B(GT) strength in this region of excitation energy allowing us to reassign proton transitions to higher excited state with respect previous studies. The main motivation to revisit these nuclei is the increase of granularity and sensitivity of the charged particle detectors and the high sensitivity and large angular coverage obtained by the use of the CLOVER detectors.

[en] The aim of this work is to revisit the decay of Argon ³²Ar with special emphasis in the p-γ coincidences. The study was motivated by the increase in granularity and sensitivity of the charged particle detectors and by the high sensitivity and large angular coverage obtained by the use of CLOVER detectors

[en] We report on the first measurement of the g factor of the J^π = 9/2⁺ isomeric state in ⁶⁵Ni. (d,p) reactions on enriched ⁶⁴Ni and ⁶²Ni have been used in order to populate and spin orient the J^π = 9/2⁺ isomeric states in ⁶⁵Ni and ⁶³Ni. The hyperfine field of the Ni target, oriented by an external magnetic field, was used in order to obtain a sufficient number of spin precessions within the relatively short life time of the isomers. The g factor obtained, g(^65mNi) = -0.296(3), is in good agreement with the g factors of other 9/2⁺ states in the region and with shell-model calculations