The main advances in the field of multinucleon transfer reactions at energies close to the Coulomb barrier are reviewed. After a short presentation of the experimental techniques and some gleams from ...the theory the new data are presented. The possibilities offered by the coupling of large gamma-array detectors with tracking spectrometers are discussed.
The barrier distributions extracted from quasielastic excitation functions are analyzed in terms of a semiclassical model that incorporates both the excitation of the surface degrees of freedom and ...the exchange of neutrons and protons. It is shown that quasielastic cross sections receive sizable contributions from transfer reactions in all measured energy range.
Absolute cross sections for isotopically identified products formed in multinucleon transfer in the (136)Xe+(198)Pt system at ∼8 MeV/nucleon are reported. The isotopic distributions obtained using a ...large acceptance spectrometer demonstrated the production of the "hard-to-reach" neutron-rich isotopes for Z<78 around the N=126 shell closure far from stability. The main contribution to the formation of these exotic nuclei is shown to arise in collisions with a small kinetic energy dissipation. The present experimental finding corroborates for the first time recent predictions that multinucleon transfer reactions would be the optimum method to populate and characterize neutron-rich isotopes around N=126 which are crucial for understanding both astrophysically relevant processes and the evolution of "magic" numbers far from stability.
One and two proton transfer channels have been measured in 116Sn+60Ni with the magnetic spectrometer PRISMA by making an excitation function at several bombarding energies, from above to well below ...the Coulomb barrier. The total kinetic energy loss distributions show the predominance of quasi-elastic processes in the sub-barrier regime. The data have been compared with calculations performed with the GRAZING program, based on semiclassical formalism, and in the Distorted Wave Born Approximation (DWBA), which provided a good theoretical description of the extracted transfer probabilities for the one proton transfers. The much larger values of the experimental two proton transfers compared with those evaluated within an independent particle transfer mechanism, indicate the presence of strong proton-proton correlations. The results complement the ones of the previously analyzed one- and two-neutron transfers, providing significant new information on the subject compared to past works.
We present some of the recent experimental results in heavy-ion transfer reactions obtained with the large solid angle magnetic spectrometer PRISMA at energies close to the Coulomb barrier. We focus ...on a series of experiments that have been carried out to study the nucleon-nucleon correlations for closed shell and superfluid systems. They are discussed together with the newest results concerning the proton transfer channels above and below the Coulomb barrier. The second set of the experiments was performed to study the production mechanism of heavy neutron-rich nuclei and the related effects of secondary processes.
•The last generation large solid angle magnetic spectrometers for very heavy ions.•Transfer of multiple pairs, providing valuable information on nucleon-nucleon correlations.•The study of the ...properties of the heavy binary partner via transfer reactions.
Significant advances have been achieved in the last years in the field of multinucleon transfer reactions. The advent of the last generation large solid angle magnetic spectrometers pushed the detection efficiency more than an order of magnitude above previous limits, with a significant gain in mass resolution for very heavy ions. Further, the coupling of these spectrometers to large gamma arrays allowed to perform gamma-particle coincidences. One can thus detect the transfer strength to the lowest excited levels of binary products and perform gamma spectroscopy for nuclei moderately far from stability, especially in the neutron-rich region. Via transfer of multiple pairs valuable information on nucleon-nucleon correlations can also be derived, especially from measurements performed below the Coulomb barrier. There is growing interest in the study of the properties of the heavy binary partner, since the transfer mechanism may allow the production of (moderately) neutron rich nuclei in the Pb and in the actinides regions, crucial also for astrophysics. Present studies are relevant for future studies with radioactive beams.
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The response function of the magnetic spectrometer PRISMA is studied via a Monte Carlo simulation that employs a ray tracing code to determine the trajectories of individual rays through the ...electromagnetic fields. The calculated response is tested on angular and energy distributions provided by theoretical calculations for the
48
Ca +
64
Ni multinucleon transfer reaction and applied to the corresponding experimental data.
New {gamma} transitions have been identified in argon isotopes in {sup 40}Ar + {sup 208}Pb multiple transfer reactions by exploiting, in a fragment-{gamma} measurement, the new generation of magnetic ...spectrometers based on trajectory reconstruction coupled to large {gamma} arrays. The coupling of single-particle degrees of freedom to nuclear vibration quanta was discussed. The interpretation of the newly observed states within a particle-phonon coupling picture was used to consistently follow, via their excitation energies, the evolution of collectivity in odd Ar isotopes. The proposed level schemes are supported by the results of sd-pf shell-model calculations, which have been also employed to evaluate the strength functions of the populated states.
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Excited states of the rubidium isotopes
37
87, 89, 91
Rb have been studied at the INFN Legnaro National Laboratory. Measurements of the
γ
-ray decay of fragments produced in binary grazing ...reactions resulting from the interaction of a beam of 530 MeV
96
Zr ions with a
124
Sn target have been complemented by studies of the
γ
-ray decay of fission fragments produced in the interaction of a beam of 230 MeV
36
S ions with a thick
176
Yb target. The structure of the yrast states of
37
87, 89, 91
Rb has been discussed within the context of spherical shell-model and cranked Nilsson-Strutinsky calculations.
PRISMA is a magnetic spectrometer for heavy ions under construction at Legnaro, with very large solid angle (80 msr), wide momentum acceptance (± 10%) and good mass resolution via TOF measurement; it ...will be dedicated to the study of nuclear dynamics and nuclear structure with stable and exotic ion beams. This is a review of its main features and of the present status of the project.
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