Evidence for a short lifetime and a long lifetime regime in the deep inelastic collisions between 40Ca and 64Ni at 182 MeV

doi:10.1016/0375-9474(77)90489-4

Nuclear Physics A

Volume 293, Issues 1–2, 12–19 December 1977, Pages 230-247

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Abstract

Deep inelastic collisions have been studied in the reaction ⁴⁰Ca + ⁶⁴Ni at 182 MeV bombarding energy. It is clearly shown that provided the energies over the interaction barrier are similar, heavy and light systems show the same trends. The charge distributions and the total kinetic energy loss are shown to be related to the interaction time and are discussed in the framework of a diffusion model. The total cross section of the DIC process is compared with other exit channel cross sections.

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Interplay of neutron–proton equilibration and nuclear dynamics
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There is a rich body of work exploring the details of these reactions and deducing the mechanisms at work. For important early results and helpful reviews, see Refs. [12–24]. For moderately higher energies (from around the Fermi energy to around the balance energy) the fusion channel is suppressed in favor of incomplete fusion, a broader phase space of deep inelastic collisions, and the onset of multi-fragmentation.
Neutron–proton equilibration in heavy-ion collisions proceeds atop a landscape of deformed topography and large density changes. The rapidly-varying landscape is created by the collision dynamics. The collision dynamics influences the neutron–proton equilibration, but just as importantly the different migration of the protons and neutrons influences the dynamics. To fully appreciate either the reaction dynamics or the neutron–proton equilibration, one must understand both. This review explores decades of work on both topics, and highlights the connections to the nuclear equation of state in nuclear experiment, theoretical prediction, and astrophysical observation.
Intermediate mechanisms in fission-like fragmentation in the 32S + 59Co and 32S + 63Cu reactions
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The fission-like fragmentation of the ³²S + ⁵⁹Co and ³²S + ⁶³Cu composite systems has been studied at incident energies E/A ≈ (4–5) MeV/nucleon. Mass, energy and angular distributions of the fission-like fragments were obtained from time-of-flight measurements. The mean total kinetic energies of the fragments are found to be fully relaxed, whereas a strong angular dependence is observed in the mass distributions. The data are interpreted in terms of a dynamical model based on the transport theory.
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Experimental evidence and theoretical concepts for the equilibration of the neutron-to-proton ratio, $N Z$ , of the fragments from binary dissipative heavy-ion collisions are reviewed. Data on nuclide distributions, characterized by the mean value of the neutron- and proton numbers, their variances and covariance as a function of the dissipated energy are discussed. Despite serious experimental and methodical difficulties there are common features emerging from these data, suggesting that the dynamical evolution of the dinuclear system may be seen as an independent-particle exchange process being constrained by the underlying potential energy surface (PES). The relevance of shell effects and differences in the transfer probabilities for neutrons and protons at small energy losses seem to underline the single particle nature of the exchange process. On the other hand, models stressing the possible role of collective, high-frequency isovector modes in the rapid relaxation of the neutron-excess degree of freedom have been advanced. Such collective quantal fluctuations have not been revealed with clarity by experiment. Discrepancies between data and mutually conflicting theoretical predictions are mainly found in the early phase of dissipative collisions. This may be connected with non-equilibrium phenomena preceding the establishment of a local equilibrium of the intrinsic degrees of freedom.
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Nuclear Physics A

Abstract

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Phys. Rev. Lett.

Nucl. Phys.

Phys. Lett.

Cited by (21)

Interplay of neutron–proton equilibration and nuclear dynamics

Intermediate mechanisms in fission-like fragmentation in the <sup>32</sup>S + <sup>59</sup>Co and <sup>32</sup>S + <sup>63</sup>Cu reactions

N Z-equilibration and nucleon exchange in dissipative heavy-ion collisions

Experimental evidence of intermediate mechanisms in the <sup>32</sup>S+<sup>59</sup>Co reaction

The interaction of 605 MeV <sup>63</sup>Cu with <sup>197</sup>Au

Various aspects of the radial and tangential energy dissipation in heavy ion collisions at bombarding energies in the range 4 - 12 MeV.A.