Dynamical Fragment Production as a Mode of Energy Dissipation in Heavy-Ion Reactions

Tōke, J.; Agnihotri, D. K.; Baldwin, S. P.; Djerroud, B.; Lott, B.; Quednau, B.; Skulski, W.; Schröder, W.; Sobotka, L. G.; Charity, R. J.; Sarantites, D. G.; Souza, R. T. de

doi:10.1103/physrevlett.77.3514

Cited by 39 publications

(51 citation statements)

References 22 publications

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“…An intense emission of intermediate mass fragments (IMF) at mid-velocity has been put into evidence [1,2,3,4,5,6,7] in collisions of heavy ions in the Fermi regime, i.e. at bombarding energies from 30 to 50 AMeV.…”

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confidence: 99%

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Intermediate Mass Fragment Emission Pattern in Peripheral Heavy-Ion Collisions at Fermi Energies

et al. 2002

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Section: 70lm 2570pqmentioning

confidence: 99%

“…5 AMeV as a function of the Total Kinetic Energy Loss of the reaction. This pattern shows that for peripheral reactions most of IMF's are emitted at mid-velocity.…”

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Intermediate Mass Fragment Emission Pattern in Peripheral Heavy-Ion Collisions at Fermi Energies

et al. 2002

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“…For such a case excitation functions are build using (2). Experimentally, it is found that B do not depend on N IMF [7,9]. We have however tested three different functional dependences of B on N IMF .…”

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“…Next, values of B close to experimental measurements [7,9] (B = 40MeV constant whatever N IMF ) are considered. For this realistic value, B…”

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Some remarks on reducibility and thermal scaling in nuclear fragmentation

Wieloch

Durand

1997

Z Phys A - Particles and Fields

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The relationship between fragment multiplicity N IMF and total transverse energy E t in nuclear fragmentation is studied with help of simple analytical considerations. It is suggested that the recent claim about reducibility and thermal scaling is due to an auto-correlation between E t and p the elementary probability deduced from the binomial-like behaviour of N IMF . 25.70.-z; 25.70.Lm Multifragmentation of nuclear species, i.e. the emission of several intermediate mass fragments on a very short time scales has been claimed to be reducible to an elementary process exhibiting a binomial-like behaviour (the so-called 'reducibility'). The two parameters, the elementary probability p for emitting an inert Intermediate Mass Fragment (IMF) and the number of attempts m undertaken by the system to emit such a fragment govern the fragment multiplicity N IMF distribution. Moreover, the dependence of log(1/p) vs 1/ √ E t , where E t is the total transverse energy of Light Charged Particles (LCP's) and IMF's was found to be linear suggesting thermal scaling [1, 2, 3]. There is no clear consensus in the literature about such a statement [4,5,6,7]. PACS:As the characteristics of IMF's enter both in the determination of E t and p, there is a question to which extent auto-correlation effects could play a role. In this short note, we investigate this problem by simple analytical considerations, taking into account some basic experimental facts such as mean transverse energy of LCP's and IMF's as well as the gaussian-like distribution of LCP's multiplicity n as a function of N IMF .For a sake of simplicity, we assume that n has a gaussian shape for a given N IMF [8]. Each gaussian has a constant width, σ n = 6.0, and the same amplitude. Centroids of the gaussians corresponding to a given number of IMF's have a value A N IMF = N IMF as illustrated in Fig. 1. Next we define total transverse energy of LCP's and charged fragments, E t , as:on leave

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“…The different features are transversal angular distribution and a lower bound of projectile energy that this squeezing mode to happen. There are experimental signals for dynamical particle emission [6,7]. In contrast to diabatic emission of particles [8] limited to beam energies much below the Fermi energy we consider here the case of faster processes around the Fermi energy.…”

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Squeezing mode in nuclear collisions

Morawetz¹,

Lipavský²

2001

Phys. Rev. C

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The time dependent Schroedinger equation is solved analytically for a simplified model of moving infinite walls. A new knock-out mode is described which might occur during heavy ion collisions. The outer shell-nucleons are ionised due to the increase of level energy when two nuclei are approaching fast enough. This is analogous to the Mott effect but in contrast occurs only if the reaction time is short enough that no common ionisation threshold in the compound system is established. To demonstrate this pure nonequilibrium effect a simulation of realistic heavy ion collision by a nonlocal Boltzmann equation is performed.When a system with bound states is exposed to a compression beyond certain values the bound states break off and decompose into their constituents. This pressure ionisation known as the Mott transition is well established in different fields of physics [1][2][3][4]. Alternatively in a many body system the density could be increased. The theoretical treatments agree in that the ionisation threshold is lowered faster than the binding energy with increasing density which leads to a cross-over and ionisation at the Mott density. These treatments rely on the fact that one has a certain degree of equilibration in the system, at least that the system has one unique ionisation threshold. This situation is however somewhat different when processes occur far from equilibrium. Then there might be not enough time to establish a common threshold in the system. In particular if two nuclei approach each other in a heavy ion collision it takes a certain time before a compound system is established or decomposition happens at higher energies. One can easily imagine that there will be no common ionisation threshold for the 2 nuclei at the early stage of reaction. Instead we will show that this leads to a new escaping mode by squeezing states which should lead to the nonequilibrium emission of particles. The principle phenomena has already been investigated in the past as light nonequilibrium particle emission [5]. Here we will show that with the help of an exactly solvable model of time dependent Schroedinger equation a new effect arise not described so far. The different features are transversal angular distribution and a lower bound of projectile energy that this squeezing mode to happen. There are experimental signals for dynamical particle emission [6,7]. In contrast to diabatic emission of particles [8] limited to beam energies much below the Fermi energy we consider here the case of faster processes around the Fermi energy. After presenting the exactly solvable model we will confirm this mode by realistic simulations which will show a transversal distribution and low energy of emitted particles while diabatic emitted particles are longitudinal peaked.Another intuitive picture is the following. The Pauli principle will forbid over-occupation of states, which should result in a Fermi gap which is closed during dissipation. Before this quasi -equilibration happens one has essentially the situation that an outer...

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Dynamical Fragment Production as a Mode of Energy Dissipation in Heavy-Ion Reactions

Cited by 39 publications

References 22 publications

Intermediate Mass Fragment Emission Pattern in Peripheral Heavy-Ion Collisions at Fermi Energies

Intermediate Mass Fragment Emission Pattern in Peripheral Heavy-Ion Collisions at Fermi Energies

Some remarks on reducibility and thermal scaling in nuclear fragmentation

Squeezing mode in nuclear collisions

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