Search

We searched for a long-living component in the collision of 238U+238U between 6.09 A and 7.35 A MeV. The experiment was performed at GANIL using the spectrometer VAMOS, tuned for observing reactions with kinematics similar to quasi-fission events. Theoretical calculations indicate that reactions with strong energy dissipation and a large number of transferred nucleons are correlated to a time delay in the decay of the giant system. We detected events of such type in the focal plane of VAMOS. These events present an excitation function increasing with bombarding energy. [ABSTRACT FROM AUTHOR]

We have studied an effect of neutron and triton transfer reactions on the p +^6He elasticscatteringat25 MeV bymeansofcoupled - reaction - channelcalculations. Itisfoundthatwhenthetransferreactionsareexplicitlyincludedinthecalculationstheimaginarypartoftheinput$ p + $6He optical model potential has to be reduced by 52 percent while its real part enhanced by 15 percent in order to fit the elastic-scattering data. The effect of transfer channels on the real part of this potential is somewhat weaker than that of 6He breakup reported previously. However, for the imaginary part, the effect of transfer channels is dominant. It is concluded that while the breakup contribution to proton elastic scattering mainly affects the real part of the bare potential, the contribution of transfer channels affects mainly its imaginary part. [ABSTRACT FROM AUTHOR]

Energy integrated reaction cross-section measurements of around sixty neutron-rich nuclei covering the region of closed shells N = 20 and N = 28 were performed at intermediate energy (30-65 A . MeV) using direct method. In this experiment, silicon detectors were used as active targets. The reduced strong absorption radii, r02, for 19 new nuclei (27F, 27,30Ne, 33Na, 28, 34-35Mg, 36-38Al, 38-40Si, 41-42P, 42-44S and 45Cl) are deduced for the first time. An additional 60 radii, also measured in this experiment, are compared to results from literature. A new quadratic parametrization is proposed for the nuclear radius as a function of the isospin in the region of closed shells N = 8 and N = 28. According to this parametrization, the skin effect is well reproduced and anomalous behaviour on the radii are observed in 23N, 29Ne, 33Na, 35Mg, 44S, 45Cl and 45Ar nuclei. [ABSTRACT FROM AUTHOR]

Abstract: Mass measurements of very neutron-rich nuclei near the and 28 shell closures are presented. Seven masses have been determined for the first time and the precision of 36 masses has been significantly improved. These results are used to investigate the evolution of the odd–even staggering of binding energies with neutron number. Special attention is paid to the evolution of the shell closure as the neutron dripline is approached. Changes in shell structure are observed around for the P and S isotopes but not for Si. This may be interpreted as a persistence of the shell closure at or as the result of a very sudden onset in deformation at 42Si. [Copyright &y& Elsevier]

The structure of the light exotic nucleus 8He was investigated using direct reactions of the 8He SPIRAL beam on a proton-rich target. The (p,p'') scattering to the state, the (p,d)7He and (p,t)6He transfer reactions, were measured at the energy . The light charged particles (p,d,t) were detected in the MUST Si-strip telescope array. The excitation spectrum of 8He was extracted from the (p,p'') reaction. Above the known excited state at 3.6 MeV, a second resonance was found around 5.4 MeV. The cross sections were analyzed within the coupled-reaction channels framework, using microscopic potentials. It is inferred that the 8He ground state has a more complex neutron-skin structure than suggested by previous models assuming a pure configuration. [Copyright &y& Elsevier]

Abstract: The weakly-bound 8He nucleus exhibits a neutron halo or thick neutron skin and is generally considered to have an structure in its ground state, with the four valence neutrons each occupying states outside the α core. The 8He()6He reaction is a sensitive probe of the ground state structure of 8He, and we present a consistent analysis of new and existing data for this reaction at incident energies of 15.7 and , respectively. Our results are incompatible with the usual assumption of a pure structure and suggest that other configurations such as may be present with significant probability in the ground state wave function of 8He. [Copyright &y& Elsevier]

Abstract: The and reactions were measured in inverse kinematics at and analyzed within the coupled reaction channels framework, the cross section being particularly large. We find that coupling to pickup has a profound effect on the elastic scattering, and that these strong coupling effects should be included in analyses of proton elastic and inelastic scattering. Through its modification of the elastic scattering wave functions this coupling will strongly affect the extraction of spectroscopic information such as the relationship between neutron and proton nuclear deformations, with important consequences for our understanding of the structure of exotic nuclei. [Copyright &y& Elsevier]