Characteristics of the fragments produced in central collisions of129Xe+natSnfrom 32Ato 50AMeV

Abstract

Characteristics of the primary fragments produced in central collisions of129 Xe + nat Sn from 32 to 50 AMeV have been obtained. By using the correlation technique for the relative velocity between light charged particles (LCP) and fragments, we were able to extract the multiplicities and average kinetic energy of secondary evaporated LCP. We then reconstructed the size and excitation energy of the primary fragments. For each bombarding energy a constant value of the excitation energy per nucleon over the whole range of fragment charge has been found. This value saturates at 3 AMeV for beam energies 39 AMeV and above. The corresponding secondary evaporated LCP represent less than 40% of all produced particles and decreases down to 23% for 50 AMeV. The experimental characteristics of the primary fragments are compared to the predictions of statistical multifragmentation model (SMM) calculations. Reasonable agreement between the data and the calculation has been found for any given incident energy. However SMM fails to reproduce the trend of the excitation function of the primary fragment excitation energy and the amount of secondary evaporated LCP's.

Systematic study of the symmetry energy within the approach of the statistical multifragmentation model

“…Reconstruction of primary fragments could provide a better understanding. Correlation techniques may provide a powerful tool for primary fragment reconstruction [2,27]. A small dependence on E ⋆ is observed for any mass range (except for C Although the output values are still higher than the expected values, they present a behavior similar to the one observed for primary fragments and appear to be only shifted by a constant offset.…”

“…Several works aimed to reconstruct primary fragments from measured quantities [2,27]. Nevertheless, in the majority of the experiments such information is not available.…”

“…However, quantitative information is difficult to extract as most fragments, produced in excited states [2,3], decay to lighter stable isotopes on a typical time scale of ∼ 10 −20 s [4], before being detected. These latter fragments are commonly referred to as secondary fragments.…”

“…These latter fragments are commonly referred to as secondary fragments. Previous work has evaluated the excitation energies of primary fragments [2,3] and indicated that secondary decay may distort the signatures of the symmetry energy contained in primary fragment observables [5,6]. It is therefore important to study model predictions for observables that can be calculated for both primary and secondary fragments.…”

Coulomb chronometry to probe the decay mechanism of hot nuclei

“…The question we want to address in this paper is the underlying mechanisms responsible for these threefragment events: are they the result of deeply-inelastic reactions (followed by fission of one of the two partners, or with the third fragment resulting from a neck formed between projectile and target), or do they result from the decay of a composite system (not necessarily fullyequilibrated) ? Is the break-up a sequential continuation of low-energy fission processes to higher available energies, or is it a precursor of the simultaneous nuclear disassembly (multifragmentation) observed at higher energies for this same system [14,15]?…”