اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدEvolution of the decay mechanisms in central collisions of $Xe$ + $Sn$ from $E/A$ = 8 to 29 $MeV$
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Collisions of Xe+Sn at beam energies of $E/A$ = 8 to 29 $MeV$ and leading to fusion-like heavy residues are studied using the $4pi$ INDRA multidetector. The fusion cross section was measured and shows a maximum at $E/A$ = 18-20 $MeV$. A decomposition into four exit-channels consisting of the number of heavy fragments produced in central collisions has been made. Their relative yields are measured as a function of the incident beam energy. The energy spectra of light charged particles (LCP) in coincidence with the fragments of each exit-channel have been analyzed. They reveal that a composite system is formed, it is highly excited and first decays by emitting light particles and then may breakup into 2- or many- fragments or survives as an evaporative residue. A quantitative estimation of this primary emission is given and compared to the secondary decay of the fragments. These analyses indicate that most of the evaporative LCP precede not only fission but also breakup into several fragments.
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item[Background]Heavy-ion reactions from barrier up to Fermi energy. item[Purpose]Reaction and fusion cross sections determination. Fusion reactions induced by $^{129}Xe$ projectiles on $^{nat}Sn$ targets for energies ranging from $8$ A.MeV to $35$ A
.MeV were measured with the INDRA $4pi$-array. The evaluation of the fusion/incomplete fusion cross sections for the incident energies from 8 to 35 A.MeV is the main purpose of this paper. item[Method] The reaction cross sections are evaluated for each beam energy thanks to INDRA $4pi$-array. The events are also sorted in order to focus the study on a selected sample of events, in such a way that the fusion/fusion incomplete cross section is estimated. item[Results] The excitation function of reaction and fusion cross sections were measured for the heavy and nearly symmetric system $^{129}Xe + ^{nat}Sn$ from 8 to 35 A.MeV. item[Conclusions] The fusion-like cross-sections evaluated show a good agrement with a recent systematics for beam energies greater than 20 A.MeV. For low beam energies the cross-section values are lower than the expected ones. A probable reason for these low values is in the fusion hindrance at energies above/close the barrier.
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