The fusion excitation function of 48Ca+48Ca has been measured above and well below the Coulomb barrier, thereby largely extending the energy range of a previous experiment down to very low cross ...sections. This system has a negative Q-value for compound nucleus formation. The fusion cross section decreases steadily below the barrier with no conspicuous change of slope below ≃300 μb. Coupled-channels calculations using a Woods–Saxon potential indicate that a large diffuseness parameter is needed to reproduce the sub-barrier cross sections. A close analogy with the case of 36S+48Ca, with Q>0, is pointed out. The sign of the Q-value does not influence fusion cross sections down to the 300–600 nb level.
Neutron rich nuclei around 48Ca have been measured with the CLARA–PRISMA setup, making use of 48Ca on 64Ni binary reactions, at 5.9 MeV/A. Angular distributions of γ rays give evidence, in several ...transfer channels, for a large spin alignment (≈70%) perpendicular to the reaction plane, making it possible to firmly establish spin and parities of the excited states. In the case of 49Ca, states arising from different types of particle–core couplings are, for the first time, unambiguously identified on basis of angular distribution, polarization and lifetime measurements. Shell model and particle–vibration coupling calculations are used to pin down the nature of the states. Evidence is found for the presence, in the same excitation energy region, of two types of coupled states, i.e. single particle coupled to either 48Ca or 50Ca simple configurations, and particle–vibration coupled states based on the 3− phonon of 48Ca.
Fusion reactions of 58,64Ni+124Sn Galtarossa, F; Jiang, CL; Stefanini, A M ...
EPJ Web of Conferences,
01/2016, Volume:
117
Conference Proceeding, Journal Article
Peer reviewed
Open access
In order to better understand the influence of transfer in sub-barrier nuclear reactions, cross sections for the system 58,64Ni+124Sn have been measured down to 0.5-1 µb and compared to detailed ...coupledchannel calculations. In agreement with a phenomenological Q-value systematics, calculations show the importance of including the coupling to the transfer channel for these heavy systems. No clear evidence of fusion hindrance is observed, probably due to the fact that the cross sections measured in this experiment are not low enough for the appearance of that phenomenon.
Fusion cross sections have been measured in the 40Ca + 58Ni and 40Ca + 64Ni systems at beam energies ranging from Elab = 104.75 MeV to 153.5 MeV using the Laboratori Nazionali di Legnaro ...electrostatic deflector. Distributions of barriers have been extracted from the experimental data. Preliminary coupled channel calculations were performed and hints of effects of neutron transfers on the fusion below the barrier in the 40Ca + 64Ni are discussed.
This study is concerned with the search for entrance channels suitable to synthesize elements with Z>118. Mass–energy distributions as well as capture cross-sections of fission-like fragments have ...been measured for the reactions 64Ni+238U→302120 and 48Ca+238U →286112 at energies near the Coulomb barrier. Compound nucleus fission cross-sections were estimated from the analysis of mass and total kinetic energy distributions. The cross-section drops three orders of magnitude for the formation of the compound nucleus with Z=120 obtained in the reaction 64Ni+238U compared to the formation of the compound nucleus with Z=112 obtained in the reaction 48Ca+238U at an excitation energy of the compound nucleus of about 45 MeV. From our analysis it turns out that the reaction 64Ni+238U is not suitable for the synthesis of element Z=120.
The fusion excitation function of 48Ti + 58Fe has been measured in a wide energy range around the Coulomb barrier, covering 6 orders of magnitude of the cross sections. We present here the ...preliminary results of this experiment, and a full comparison with the near-by system 58Ni + 54Fe where evidence of fusion hindrance shows up at relatively high cross sections. The sub-barrier cross sections of 48Ti + 58Fe are much larger than those of 58Ni + 54Fe. Significant differences are also observed in the logarithmic derivatives, astro-physical S-factors and fusion barrier distributions. The influence of low-energy nuclear structure on all these trends is pointed out and commented. Coupled-channels calculations using a Woods-Saxon potential are able to reproduce the experimental results for 48Ti + 58Fe. The logarithmic derivative of the excitation function is very nicely fit, and no evidence of hindrance is observed down to around 1 μb. The fusion barrier distribution is rather wide, flat and structureless. It is only in qualitative agreement with the calculated distribution.
The sub-barrier fusion excitation function of 40Ca + 96Zr has been measured down to cross sections ≃2.4µb, i.e. two orders of magnitude smaller than obtained in the previous experiment, where the ...sub-barrier fusion of this system was found to be greatly enhanced with respect to 40Ca + 90Zr, and the need of coupling to transfer channels was suggested. The purpose of this work was to investigate the behavior of 40Ca + 96Zr fusion far below the barrier. The smooth trend of the excitation function has been found to continue, and the logarithmic slope increases very slowly. No indication of hindrance shows up, and a comparison with 48Ca + 96Zr is very useful in this respect. A new CC analysis of the complete excitation function has been performed, including explicitly one- and two-nucleon Q >0 transfer channels. Such transfer couplings bring significant cross section enhancements, even at the level of a few µb. Locating the hindrance threshold, if any, in 40Ca + 96Zr would require challenging measurements of cross sections in the sub-µb range.
The two reactions,
16O
+
12C and
18O
+
12C were studied in the energy range between 5 and 10 MeV per nucleon. The binary fragments were identified at the large scattering angles using the kinematic ...coincidence method. The energy distributions of the dominant binary channels, and the angular distributions of the strongest populated states are presented. The differences between the two entrance channels are discussed. The evolution of the reaction mechanism from quasi-elastic to fully damped processes are presented as a function of bombarding energy, scattering angle, excitation energy and number of transferred nucleons.
Large acceptance magnetic spectrometers, such as PRISMA installed at Laboratori Nazionali di Legnaro, gave a further boost to the renewed interest for multinucleon transfer reactions in the last ...decade. The large solid angles of these devices and the high resolving powers of their detection systems allowed to investigate the transfer process around and well below the Coulomb barrier and to perform nuclear structure studies in several mass regions of the nuclide chart when coupled with large γ-ray arrays such as CLARA. Selected results obtained with the PRISMA-CLARA set-up in odd argon isotopes populated by using the multinucleon transfer process and in sub-barrier transfer measurements are presented in this contribution. The status of an ancillary detector which is being developed for PRISMA in order to perform kinematical coincidence measurements is also reported.
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