Reaction mechanisms and multifragmentation processes in64Zn+58Niat

Abstract

Reaction mechanisms and multifragmentation processes have been studied for 64 Znϩ 58 Ni collisions at intermediate energies with the help of antisymmetrized molecular dynamics ͑AMD-V͒ model calculations. Experimental energy spectra, angular distributions, charge distributions, and isotope distributions, classified by their associated charged particle multiplicities, are compared with the results of the AMD-V calculations. In general the experimental results are reasonably well reproduced by the calculations. The multifragmentation observed experimentally at all incident energies is also reproduced by the AMD-V calculations. A detailed study of AMD-V events reveals that, in nucleon transport, the reaction shows some transparency, whereas in energy transport the reaction is much less transparent at all incident energies studied here. The transparency in the nucleon transport indicates that, even for central collisions, about 75% of the projectile nucleons appear in the forward direction. In energy transport about 80% of the initial kinetic energy of the projectile in the centerof-mass frame is dissipated. The detailed study of AMD-V events also elucidates the dynamics of the multifragmentation process. The study suggests that, at 35A MeV, the semitransparency and thermal expansion are the dominant mechanisms for the multifragmentation process, whereas at 49A MeV and higher incident energies a nuclear compression occurs at an early stage of the reaction and plays an important role in the multifragmentation process in addition to that of the thermal expansion and the semitransparency.

Experimental reconstruction of excitation energies of primary hot isotopes in heavy ion collisions near the Fermi energy

“…10(a) are E M X ∼ 0. 16 MeV, E T X ∼ 0.05 MeV, and the total error E X ∼ 0.17 MeV. The error contribution from the multiplicity becomes larger partially because the contribution comes from the first term and Q value term in Eq.…”

“…An accurate modeling of these processes is not simple. Global features of the characteristic experimental observables, such as multiplicities, mass or charge distributions, and energy spectra or the mean energy of the fragments, have been well reproduced by both statistical multifragmentation models, such as microcanonical Metropolitan Monte Carlo model (MMMC) [1,2] and the statistical multifragmentation model (SMM) [2][3][4][5][6][7][8][9][10], and by transport-based models, such as antisymmetrized molecular dynamics (AMD) [11][12][13][14][15][16][17][18], stochastic mean field model (SMF) [19][20][21], and Improved quantum statistical model (ImQMD) [22][23][24][25][26], although they are based on quite different assumptions. The statistical models utilize a freeze-out concept.…”

Compatibility of localized wave packets and unrestricted single particle dynamics for cluster formation in nuclear collisions

“…The answer will depend on the type of reaction which we want to describe. AMD/D has been applied, with a reasonable success, to various reaction systems in the medium energy region not only for nuclear collisions [9,19,20,21] but also for nucleon induced fragmentation reactions [22]. However, these successes do not mean that AMD/D is valid for all kinds of reactions.…”

Experimental reconstruction of primary hot isotopes and characteristic properties of the fragmenting source in heavy-ion reactions near the Fermi energy

“…[66,67] suggests that the multifragmentation in the AMD simulations reflects a large fluctuation of the virtual "freezeout" in space, density and time and causes a variety of cluster generation at early stages of the reaction. The experimental observation of the power law distribution for A ≥ 15 may suggest that there ia a virtual "freezeout" volume for the production of the heavier fragments, but for the production of the lighter fragments dynamical processes, such as semi-transparency [64,68], neck-emissions and so on, become more important.…”