The gamma decay of neutron-rich nuclei around 48Ca was measured at Legnaro National Laboratory (Italy) with the PRISMA-CLARA setup, following the multi-nucleon transfer reaction 48Ca on 64Ni at 282 MeV. Evidence is found for a large spin alignment (of the order of 70%), perpendicular to the reaction plane. As a consequence, angular distributions and polarizations of gamma-rays allow to firmly establish, for the first time, spin and parities of excited states in several nuclei, such as Ca, Sc and K. In addition, lifetime measurements, performed with the Differential Plunger Technique, help establishing the nature of these states, in comparison with predictions based on shell model and particle-vibration coupling calculations. In the case of 49Ca, evidence is found for the presence, in the same excitation energy region, of two types of coupled states, i.e. particle-vibration coupled states based on the 3- phonon of 48Ca and single particle coupled to either 48Ca or 50Ca simple configurations. In the latter case, the measured B(Elambda) value gives also the possibility to disentangle between equivalent configurations based on the two different core states. Furthermore, we note that the 9/2+ state at 4017 keV in 49Ca represents one of the few fully established examples of particle-vibration coupling in nuclei with mass A<100, showing the robustness of nuclear collectivity in rather light systems. The cases of 47Ca and 50Ca will be also discussed in detail, where particle-phonon couplings and pairing effects play a crucial role. The present work makes clearly visible the multifaceted nature of particle-core coupling interactions in the atomic nucleus, giving also a warning to simple generalizations of coupling schemes. It also clearly demonstrates the feasibility of complete in-beam gamma-spectroscopy with heavy-ion transfer reactions, providing a method that can be further exploited in the future with heavy targets and radioactive beams.
Complete gamma-spectroscopy of n-rich nuclei around 48Ca with multi-nucleon transfer reactions / S. Leoni. ((Intervento presentato al convegno Advances in radioactive isotopes science : ARIS tenutosi a Leuven, Belgium nel 2011.
Complete gamma-spectroscopy of n-rich nuclei around 48Ca with multi-nucleon transfer reactions
S. LeoniPrimo
2011
Abstract
The gamma decay of neutron-rich nuclei around 48Ca was measured at Legnaro National Laboratory (Italy) with the PRISMA-CLARA setup, following the multi-nucleon transfer reaction 48Ca on 64Ni at 282 MeV. Evidence is found for a large spin alignment (of the order of 70%), perpendicular to the reaction plane. As a consequence, angular distributions and polarizations of gamma-rays allow to firmly establish, for the first time, spin and parities of excited states in several nuclei, such as Ca, Sc and K. In addition, lifetime measurements, performed with the Differential Plunger Technique, help establishing the nature of these states, in comparison with predictions based on shell model and particle-vibration coupling calculations. In the case of 49Ca, evidence is found for the presence, in the same excitation energy region, of two types of coupled states, i.e. particle-vibration coupled states based on the 3- phonon of 48Ca and single particle coupled to either 48Ca or 50Ca simple configurations. In the latter case, the measured B(Elambda) value gives also the possibility to disentangle between equivalent configurations based on the two different core states. Furthermore, we note that the 9/2+ state at 4017 keV in 49Ca represents one of the few fully established examples of particle-vibration coupling in nuclei with mass A<100, showing the robustness of nuclear collectivity in rather light systems. The cases of 47Ca and 50Ca will be also discussed in detail, where particle-phonon couplings and pairing effects play a crucial role. The present work makes clearly visible the multifaceted nature of particle-core coupling interactions in the atomic nucleus, giving also a warning to simple generalizations of coupling schemes. It also clearly demonstrates the feasibility of complete in-beam gamma-spectroscopy with heavy-ion transfer reactions, providing a method that can be further exploited in the future with heavy targets and radioactive beams.
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