Experimental studies of the competition between fusion and quasifission in the formation of heavy and superheavy nuclei

Hinde, David; Dasgupta, M.; Simpson, E. C.

doi:10.1016/j.ppnp.2021.103856

Cited by 32 publications

(7 citation statements)

References 313 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Quasi-fission trajectories were searched for up to approximately 30 zs contact times. Although a slow quasi-fission component with longer contact times is observed experimen- tally [2], this upper limit is of the order of the longest quasifission times observed in TDHF calculations [6]. We therefore consider that the system has fused when the contact time reaches τ ∼ 31 zs (unless an increase of elongation indicates a likely quasi-fission at a later time, in which case the calculations is run up to τ ∼ 35 zs), which occurs essentially below critical angular momentum L c that depends on the orientation of the target.…”

mentioning

confidence: 93%

“…In the latter two cases, a compound nucleus is formed with equilibrated internal degrees of freedom in such a way that the fission process only depends on its excitation energy and angular momentum. On the other hand, quasi-fission is an outof-equilibrium mechanism occurring when two heavy collision partners transfer a significant amount of nucleons through mass equilibration, before separating in fission-like fragments without the intermediate formation of a compound nucleus [1] (see [2] for a recent experimental review).…”

mentioning

confidence: 99%

“…Our goal is now to investigate quasi-fission modes in 50 Ca+ 176 Yb collisions which, in the case of fusion, would form the 226 Th compound nucleus. Quasi-fission is known to rapidly increase with the charge product Z 1 Z 2 of the reactants [2]. Although experimental signatures of quasi-fission have been found in systems with Z 1 Z 2 as small as 736 in the 16 O+ 238 U reaction [60], the lightest system in which quasifission reactions have been observed in TDHF calculations is 50 Cr+ 180 W (Z 1 Z 2 = 1776) [44].…”

mentioning

confidence: 99%

See 2 more Smart Citations

Comparison of fission and quasi-fission modes

Simenel,

McGlynn,

Umar

et al. 2021

Preprint

View full text Add to dashboard Cite

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.

show abstract

mentioning

confidence: 93%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Comparison of fission and quasi-fission modes

Simenel,

McGlynn,

Umar

et al. 2021

Preprint

View full text Add to dashboard Cite

show abstract

“…Similar shell effects could also affect the formation of fragments in quasifission reactions [19][20][21][22][23][24][25]. Quasifission occurs when two heavy-ions collide, fully dissipate their relative kinetic energy, and transfer nucleons from the heavy fragment to the lighter one within a few zeptoseconds (10 −21 s) to a few tens of zeptoseconds [26][27][28] (see also [29] for a recent experimental review on quasifission). This slow mass drift towards symmetry could eventually be stopped by shell effects in the fragments.…”

Section: Introductionmentioning

confidence: 99%

Time-dependent Hartree-Fock study of quasifission trajectories in reactions forming $^{294}$Og

McGlynn¹,

Simenel²

2023

Preprint

View full text Add to dashboard Cite

Background: Fission modes in superheavy nuclei are expected to be impacted by quantum shell effects. Similar shell effects may be present in quasifission reactions, acting to hinder the mass equilibration process in heavy-ion collisions.Purpose: To investigate quasifission mechanisms in five different reactions forming 294 Og as a compound nucleus and compare quasifission trajectories with predicted fission modes.Methods: The potential energy surface (PES) of 294 Og is calculated using the static Hartree-Fock approach with BCS pairing correlations. Quasifission trajectories for central collisions at various energies are studied with the time-dependent Hartree-Fock theory.Results: The exit channel strongly depends on initial mass asymmetry and orientation, but it only exhibits small dependences in the reaction energy. The 48 Ca+ 246 Cf reaction is affected by the PES topology, leading to either fusion or asymmetric fission. Spherical shell effects associated with the Z = 50 magic gap hinder charge and mass equilibrations in 126 Sn+ 168 Er, resulting in large total kinetic energies and compact scission configurations.Conclusions: Quasifission trajectories can be interpreted in terms of the underlying PES for low excitation energies. Future investigations of quasifission with temperature and angular momentum dependent PES could be considered.

show abstract

“…Experimentally, the fusion probability can be extracted from the measurement of fusion-evaporation residue cross sections [39,40], comparing the width of fragment mass distribution with the width expected in the case of pure fusion-fission [21,41,42], or the analysis of the fragment angular distribution [43][44][45]. Recent years, many efforts have been made to measure the fusion probability and lots of progresses have been achieved [46]. Very recently, experimentalists have extracted the fusion probabilities for both cold-fusion and hot-fusion reactions [21,35,45].…”

Section: Introductionmentioning

confidence: 99%

Microscopic study of the compound nucleus formation in cold-fusion reactions

Sun,

Guo

2022

Preprint

View full text Add to dashboard Cite

The understanding of the fusion probability is of particular importance to reveal the mechanism of producing superheavy elements. We present a microscopic study of the compound nucleus formation by combining timedependent density functional theory, coupled-channels approach, and dynamical diffusion models. The fusion probability and compound nucleus formation cross sections for cold-fusion reactions 48 Ca+ 208 Pb, 50 Ti+ 208 Pb, and 54 Cr+ 208 Pb are investigated and it is found that the deduced capture barriers, capture cross sections for these reactions are consistent with experimental data. Above the capture barrier, our calculations reproduce the measured fusion probability reasonably well. Our studies demonstrate that the restrictions from the microscopic dynamic theory improve the predictive power of the coupled-channels and diffusion calculations.

show abstract

Experimental studies of the competition between fusion and quasifission in the formation of heavy and superheavy nuclei

Cited by 32 publications

References 313 publications

Comparison of fission and quasi-fission modes

Comparison of fission and quasi-fission modes

Time-dependent Hartree-Fock study of quasifission trajectories in reactions forming $^{294}$Og

Microscopic study of the compound nucleus formation in cold-fusion reactions

Contact Info

Product

Resources

About