We present a new experimental method to correlate the isotopic composition of intermediate mass fragments (IMF) emitted at mid-rapidity in semi-peripheral collisions with the emission timescale: IMFs emitted in the early stage of the reaction show larger values of
40 Ca+ 40,48 Ca, 46 Ti reactions at 25 MeV/A have been studied using the 4π CHIMERA detector. An isospin effect on the competition between incomplete fusion and dissipative binary reaction mechanisms has been observed. The probability of producing a compound system is observed to be lower in the case of N≈Z colliding systems as compared to the case of reactions induced on the more neutron rich 48 Ca target. Predictions based on CoMD-II calculations show that the competition between fusion-like and dissipative reactions, for the selected centrality, can strongly constraint the parameterization of symmetry energy and its density dependence in the nuclear equation of state.Pacs: 21.65. Ef, 21.65.Mn, 25.70.Jj, 25.70.Lm Collisions between heavy ions with different neutronproton asymmetries offer a unique opportunity to study the equation of state (EOS) of asymmetric nuclear matter [1][2][3][4]. Accessing the density dependence of the symmetry energy has recently attracted the interest of the community due to its implications in both nuclear physics and astrophysics of neutron stars [2,5,6]. The isotopic composition of fragments produced in multifragmentation phenomena is being extensively studied at intermediate beam energies (E/A=20-100 MeV) bearing important information on the symmetry energy [7]. One aspect not yet fully investigated is represented by the effect of the isospin asymmetry on the fate of hot nuclear systems. The combined effects of the symmetry energy and of the repulsive Coulomb interaction can significantly affect the reaction mechanism and the rate of production of hot compound nuclei in heavy-ion reactions at low and intermediate energies [8][9]. The isospin N/Z-asymmetry can also play an important role in opening different decay channels for a hot nuclear system once this has been produced. In this respect, the limiting temperature of a nucleus is expected to depend on both its mass and its isotopic composition [10][11][12]. Experimentally, the observation of small isotopic effects on the temperatures of projectile spectators in relativistic heavy-ion collisions have been interpreted as a signal of no isospin dependence of nuclear limiting temperatures [13]. At lower beam energies, a mass and N/Z-asymmetry dependence in limiting temperatures have been explored by studying the population of the Giant Dipole Resonance (GDR) at high excitation energies [14]. A small difference in the limiting GDR excitation energy has been observed when comparing a symmetric N~Z system to a neutron rich system [15]. All these findings stimulate attempts to link N/Z effects on measured observables to the nuclear symmetry energy and its density dependence in the equation of state.In this work we explore isospin effects in heavy residue (HR) remnants produced in incomplete fusion reactions between projectile and targets with different N/Z asymmetries. The results on the competition between incomplete fusion and binary dissipative mechanisms are compared to simulations performed with a microscopic mode...
In-plane and out-of-plane angular correlations of fission fragments detected in coincidence with projectile residues produced in nuclear collisions 19 Fϩ 238 U at 115, 120, and 125 MeV have been investigated. The data are described assuming sequential fission decay of targetlike nuclei produced in peripheral transfer reactions.
Multi-breakup processes for the 124 Sn+ 64 Ni system at 35 MeV/nucleon have been studied with the forward part of the CHIMERA detector. An extensive comparison between experimental data corresponding to almost complete ternary events and constrained molecular dynamics (CoMD-II) calculations suggests different characteristic times in the selected processes. This is in agreement with previous studies of the same reaction already published concerning the prompt intermediate-mass-fragment emission. Stimulated by CoMD-II calculations, we investigate the existence of more complex dynamical multi-breakup processes occurring on the same time scale. A detailed study of the rotational dynamics leading to slower dynamical fission processes is also presented.
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