Preequilibrium emission and incomplete fusion of low and medium mass heavy ion systems

Gonin, Marc; Coffin, J. P.; Guillaume, G.; Jundt, F.; Wagner, P.; Fintz, P.; Heusch, B.; Malki, A.; Fahli, Ahmed; Kox, S.; Merchez, F.; Mistretta, J.

doi:10.1103/physrevc.38.135

Cited by 20 publications

(17 citation statements)

References 25 publications

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“…This results in an intermediate nucleus with mass A = 66 and about 380 MeV excitation energy, i.e. with an average excitation energy of e=5.8 MeV/ nucleon, in good agreement with values found in 4~ fusion reactions on 27A1 [23], 45Sc [6], natNi [5] and 6SZn [24] at bombarding energies 26-35 MeV/u. However, our value substantially exceeds the maximum excitation energy claimed in [9] as limit for residue production in the symmetric Si reaction.…”

Section: Discussionsupporting

confidence: 82%

Light-particle emission versus evaporation residue formation in collisions of40Ar onnatCa at 30 MeV/u

Gentner

Bellm

Lassen

et al. 1993

Z. Physik A - Hadrons and Nuclei

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Abstract.The closely associated phenomena of preequilibrium emission and evaporation residue formation in fusion-like reactions were studied in central collisions between 4~ and ha*Ca at 30 MeV/u. Heavy reaction products were taken in coincidence with neutrons and light charged particles. The preequilibrium neutron data agree very well with predictions of a quantal phase-space model which, in addition to the mean field, takes two-body collisions properly into account. Preequilibrium emission ends in thermally equilibrated hot nuclei with an average excitation energy of about 6 MeV/u. The combined results show a striking interrelation between the 'missing mass' and light-particle multiplicities: the mass difference between the full compound mass and the observed residues can be explained quantitatively by the emission of only neutrons and light charged particles with Z < 2 during the entire course of energy dissipation.

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Section: Discussionsupporting

confidence: 82%

Light-particle emission versus evaporation residue formation in collisions of40Ar onnatCa at 30 MeV/u

Gentner

Bellm

Lassen

et al. 1993

Z. Physik A - Hadrons and Nuclei

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“…It was found that the preequilibrium particles were mostly produced by the lightest partner. This finding was obtained from the masses and velocities of the evaporation residues [t0-13] as well as from a direct measurement of the preequilibrium particles [6][7][8]. The heavy partner participates almost entirely with the fusion mechanism.…”

Section: Introductionmentioning

confidence: 98%

Influence of the mass asymmetry of the entrance channel on incomplete fusion processes

Pieńkowski

Lléres²,

Nifenecker³

et al. 1989

Z. Physik A - Atomic Nuclei

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The angular and velocity distributions of incomplete fusion residues have been measured, around 30 AMeV projectile incident energy, for a number of systems with varying mass asymmetries, from the most asymmetric S + Cu, to the almost symmetric Ar + Ca. The main experimental finding is that the parallel width of the velocity distribution increases sharply for decreasing asymmetries, while the perpendicular width remains nearly constant. Using, as data, the widths and mean values of the velocity distributions, it was possible to derive the number of preequilibrium particles emitted by the projectile and by the target. It was found that target emission becomes noticeable only when the center of mass velocity of the target, at nuclear contact, exceeds approximately 2.5 cm/ns. This underlines the relevance of the center of mass velocities in the preequilibrium emission and incomplete fusion processes.

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“…With the hypothesis that the clusters, once formed, cannot recombine [15] and generate smaller clusters, the dynamics describe the rate at which the different nuclear species are formed as well as that at which the system deexcites and expands in space. The predictions of this model have been tested with various experimental systems [7,15,16]. Recently, this model has been implemented to simulate the whole decay process on an event by event basis [17].…”

Section: The Pep Calculationmentioning

confidence: 98%

“…One has to keep in mind that these calculations consider a single CN for the initial thermalized system. It is well established, however, that in incomplete fusion a set of nuclear species is formed in this intermediate phase of the reaction [7]. The introduction of such a distribution would appreciably lower the excitation energy of the initial CN.…”

Section: The Heavy Fragmentsmentioning

confidence: 98%

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Preequilibrium versus thermalized light-charged particle emissions in the40Ar (1100MeV)+24Mg reaction. Dynamical calculations

Malki¹,

Coffin²,

Guillaume³

et al. 1991

Z. Physik A - Hadrons and Nuclei

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In an attempt to separate preequilibrium and thermalised emissions of light particles in low impact parameter heavyion collisions, the 4~ + 24Mg reaction has been studied at 27.5 MeV/nucleon. Exclusive measurements have permitted us to examine, in some detail, heavy fragments and charged particles (p, d, t, e-particle). The fragments recognized as evaporation residues have been selected and, due to inverse kinematic conditions, the related preequilibrium and statistical emissions of light particles resulting from incomplete fusion reaction appear to be distinguishable to a fair extent. This separation is fully supported by Monte Carlo calculations. Some experimental characteristics of the light particles have been examined and compared to the predictions of dynamical calculations. These calculations, associating a preequilibrium (interpreted as prompt emitted particles) model with a statistical-decay model, follow the evolution of the collision from the point of contact between the projectile and the target to the final evaporation-residue formation on an event by event basis. The predictions of these calculations have been compared to experimental data and satisfactory agreement is achieved for fragment-mass distribution, proton-energy spectra, and proton-angular distribution.

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Preequilibrium emission and incomplete fusion of low and medium mass heavy ion systems

Cited by 20 publications

References 25 publications

Light-particle emission versus evaporation residue formation in collisions of40Ar onnatCa at 30 MeV/u

Light-particle emission versus evaporation residue formation in collisions of40Ar onnatCa at 30 MeV/u

Influence of the mass asymmetry of the entrance channel on incomplete fusion processes

Preequilibrium versus thermalized light-charged particle emissions in the40Ar (1100MeV)+24Mg reaction. Dynamical calculations

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