Timescales of Quantum Equilibration, Dissipation and Fluctuation in Nuclear Collisions

Simenel, C.; Godbey, K.; Umar, A. S.

doi:10.1103/physrevlett.124.212504

Cited by 56 publications

(35 citation statements)

References 45 publications

(88 reference statements)

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“…It was found that the up limitation of impact parameter for synthsis of superheavy element Z = 116 was L = 56 h, mainly because the dissipatting energy of colliding system reached equilibrium almostly. The boundary line between CF and MNT have been found, which is around 5.7×10 −21 s. It is worth mentioning that our calculations for equilibrium timescales of fragment mass asymmetry and kinetic dissipation are consistant with those calculations from TDHF and TDRPA [60].…”

Section: Resultsmentioning

confidence: 51%

Rare Isotope Formation in Complete Fusion and Multinucleon Transfer Reactions in Collisions of 48Ca +248Cm around Coulomb Barrier Energies

Chen,

Niu,

et al. 2022

Preprint

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Within the framework of dinuclear system model, the reaction mechanisms for synthesizing targetlike isotopes from Bk to compound nuclei Lv are thoroughly investigated in complete and incomplete fusion reaction of 48 Ca + 248 Cm around Coulomb barrier energies. Production cross section of 292,293 Lv as a function of excitation energy in fusion-evaporation reactions and target-like isotopic yields in multinucleon transfer reactions are evaluated, in which a statistical approach is used to describe the decay process of excited nuclei. The available experimental data can be reproduced well with the model reasonably. The products of all possible formed isotopes in the dynamical preequilibrium process for collision partners at incident energy E lab = 5.5 MeV/nucleon are exported, systematically. It is found that the quasi-fission fragments are dominant in the yields. The optimal pathway from target to compound nuclei shows up along the valley of potential surface energy. The effective impact parameter of two colliding partners leading to compound nuclei is selected from head on collison to semicentral collision with L = 52 h. The timescale boundary between complete fusion and multinucleon transfer reactions is about 5.7×10 −21 s with effective impact parameters. Synthesis cross section of unknown neutron-rich actinides from Bk to Rf have been predicted around several nanobarn.

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Section: Resultsmentioning

confidence: 51%

Rare Isotope Formation in Complete Fusion and Multinucleon Transfer Reactions in Collisions of 48Ca +248Cm around Coulomb Barrier Energies

Chen,

Niu,

et al. 2022

Preprint

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“…where t s is the sticking time and t m is the mass equilibrium time constant, determined experimentally to be 5.2 × 10 −21 s [23]. This value later confirmed by fully microscopic calculations [54]. The mass ratio of the target-like nuclei is (1 − M R ).…”

Section: Discussionmentioning

confidence: 55%

Energy dissipation and suppression of capture cross sections in heavy ion reactions

et al. 2021

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Background: At energies above the capture barrier, coupled-channels (CC) calculations with a standard nuclear potential diffuseness (0.65 fm) increasingly overestimate experimental capture cross section as the charge product (Z 1 Z 2 ) of the colliding nuclei increases. It has been suggested this may be linked to energy dissipation outside the capture barrier. Purpose: We investigate quantitatively the role of energy dissipation in suppressing capture in heavy ion fusion reactions. Method: The yields of sequential fission, including that resulting from deep inelastic collisions, and of fission following capture were determined simultaneously for collisions of 18 O, 30 Si, 34 S, and 40 Ca + 232 Th at a range of energies around the respective capture barriers. Results:The ratio of experimental to CC capture cross sections was found to decrease with increasing Z 1 Z 2 . Conversely, the ratio of sequential fission to capture-fission increased with increasing Z 1 Z 2 . The sum of sequential and capture fission agrees quite well with the CC cross sections. Conclusions: The experimental capture fission and sequential fission cross sections, and their comparison with CC calculations, give a consistent picture that the increase in density overlap at the capture barrier with increasing Z 1 Z 2 of the colliding nuclei is correlated with increasing energy dissipative processes. These compete increasingly strongly with capture as the Z 1 Z 2 of the reaction increases. For the 40 Ca reaction, the total fission yield exceeds expectations from capture model calculations, indicating that deep inelastic processes occur both from trajectories that would have led to capture and also from more peripheral trajectories.

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“…For instance, the total kinetic energy of the fragments is well approximated by the Viola systematics [3,4], indicating a slow, damped relative motion of the fragments. In addition, the timescale for quasi-fission reactions [1,5,6] is of the same order as the minimum average timescale for the evolution from the compound system to the formation of the final fragments which is about 20 − 50 zs [7]. Another similarity is that both reaction mechanisms are impacted by quantum shell effects.…”

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confidence: 91%

Comparison of fission and quasi-fission modes

Simenel,

McGlynn,

Umar

et al. 2021

Preprint

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Quantum shell effects are known to affect the formation of fragments in nuclear fission. Shell effects also affect quasi-fission reactions occurring in heavy-ion collisions. Systematic time-dependent Hartree-Fock simulations of 50 Ca+ 176 Yb collisions show that the mass equilibration between the fragments in quasi-fission is stopped when they reach similar properties to those in the asymmetric fission mode of the 226 Th compound nucleus. Similar shell effects are then expected to determine the final repartition of nucleons between the nascent fragments in both mechanisms. This observation opens the possibility to explore asymmetric fission modes of superheavy nuclei with quasi-fission reactions.

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Timescales of Quantum Equilibration, Dissipation and Fluctuation in Nuclear Collisions

Cited by 56 publications

References 45 publications

Rare Isotope Formation in Complete Fusion and Multinucleon Transfer Reactions in Collisions of 48Ca +248Cm around Coulomb Barrier Energies

Rare Isotope Formation in Complete Fusion and Multinucleon Transfer Reactions in Collisions of 48Ca +248Cm around Coulomb Barrier Energies

Energy dissipation and suppression of capture cross sections in heavy ion reactions

Comparison of fission and quasi-fission modes

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