Mass-split dependence of the pre- and post-scission neutron multiplicities for fission of 251Es

doi:10.1016/0375-9474(87)90213-2

Nuclear Physics A

Volume 472, Issue 2, 28 September 1987, Pages 318-332

https://doi.org/10.1016/0375-9474(87)90213-2 Get rights and content

Abstract

Pre- and post-scission neutron multiplicities have been measured as a function of fission mass-split for the reactions of 105 and 120 MeV ¹⁹F with ²³²Th. The post-scission multiplicities show no evidence for persistence of the sawtooth yield observed for spontaneous fission of ²⁵²Cf; the dependence on mass-split is not consistent with the random neck rupture model. The pre-scission multiplicities show no evidence of quasi-fission for asymmetric mass-splits. It is proposed that pre-scission neutron multiplicity measurements should be a useful tool in studying quasi-fission produced by reactions with heavier projectiles.

References (38)

D.J. Hinde et al.
Phys. Rev. Lett.
(1984)
D.J. Hinde et al.
erratum
(1984)
U. Jahnke et al.
Phys. Rev. Lett.
(1986)
S.B. Kaufman et al.
Nucl. Instr. Meth.
(1974)
V.E. Viola et al.
Phys. Rev.
(1985)
J.R. Leigh et al.
Phys. Rev. Lett.
(1979)
J.R. Leigh et al.
Phys. Lett.
(1985)
C.J. Bishop et al.
Nucl. Phys.
(1970)
Z. Fraenkel et al.
Phys. Rev.
(1975)
J. O. Newton et al., to be...
A. Gavron et al.
Phys. Rev.
(1987)

K. Lützenkirchen et al.

Nucl. Phys.

(1986)

A. Gavron et al.

Phys. Rev. Lett.

(1981)

A. Gavron et al.

erratum

(1982)

E. Holub et al.

Phys. Rev.

(1983)

D. Ward et al.

Nucl. Phys.

(1983)

W.P. Zank et al.

Phys. Rev.

(1986)

D.J. Hinde et al.

Nucl. Phys.

(1986)

P. Grange et al.

Phys. Rev.

(1986)

H. Delangrange et al.

Z. Phys.

(1986)

U. Brosa et al.

Z. Phys.

(1983)

Cited by (101)

Sequential fission and the influence of <sup>208</sup>Pb closed shells on the dynamics of superheavy element synthesis reactions
2023, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Measured binary quasifission mass spectra in reactions with actinide nuclides show a large peak in yield near the doubly-magic ²⁰⁸Pb. This has generally been attributed to the enhanced binding energy of ²⁰⁸Pb causing a valley in the potential energy surface, attracting quasifission trajectories. To investigate this interpretation, binary quasifission mass spectra and cross-sections have been measured at near-barrier energies for reactions of ⁵⁰Ti with actinide nuclides from ²³⁸U to ²⁴⁹Cf. Cross-sections have also been deduced for sequential fission (a projectile-like nucleus and two fragments from fission of the complementary target-like nucleus). Binary cross-sections fall from ∼70% of calculated capture cross-sections for ²³⁸U to only ∼40% for ²⁴⁹Cf, with a compensating increase in sequential fission cross-sections. The data are consistent with the ²⁰⁸Pb peak originating largely from sequential fission of heavier fragments produced in more mass-asymmetric primary quasifission events. These are increasingly suppressed as the heavy quasifission fragment mass increases above ²⁰⁸Pb. The important role of sequential fission calls for re-interpretation of quasifission characteristics and dynamics in superheavy element synthesis reactions.
Comparison of fission and quasi-fission modes
2021, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
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 ⁵⁰Ca+¹⁷⁶Yb 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 ²²⁶Th compound nucleus. Similar shell effects are then expected to determine the final repartition of nucleons between the nascent fragments in both mechanisms. Future experimental studies that could test these observations are discussed.
Experimental studies of the competition between fusion and quasifission in the formation of heavy and superheavy nuclei
2021, Progress in Particle and Nuclear Physics
Citation Excerpt :
From energy and time-of-flight, the mass of the detected fission fragment can be deduced. Si detectors have been used to measure fission angular distributions [18,34] and mass distributions [17,35], and sometimes both in combination. Through interpolation in angle, measurements with these detectors have also provided distributions of both mass and angle [36,37], more recently referred to as mass–angle distributions (MADs).
Quasifission competes with fusion, and can suppress the cross sections for formation of heavy elements by orders of magnitude. Its understanding is important both to map out opportunities to synthesise superheavy elements and isotopes, and to understand the non-equilibrium dynamics that controls heavy ion reactions. A review of experimental studies of quasifission is presented, summarising significant insights obtained experimentally over the last 40 years. Possible origins for conflicting results are discussed, to try to identify and/or resolve outstanding discrepancies between different investigations at different times. Work in the last 10 years has highlighted the strong influence of the nuclear structure of the two colliding nuclei on the competition between quasifission and fusion. New approaches to separate the yields of quasifission and fusion–fission are discussed.
Zeptosecond contact times for element Z=120 synthesis
2020, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
The synthesis of new superheavy elements beyond oganesson (Z=118) requires fusion reactions with projectile nuclei with proton numbers larger than that of ⁴⁸Ca (Z=20), which has been successfully employed for the synthesis of elements with Z=112-118. In such reactions, fusion is drastically hindered by fast non-equilibrated dynamical processes. Attempts to produce nuclei with Z=120 using the ⁶⁴Ni+²³⁸U, ⁵⁸Fe+²⁴⁴Pu, ⁵⁴Cr+²⁴⁸Cm, and ⁵⁰Ti+²⁴⁹Cf reactions have been made, which all result in larger Coulomb forces than for ⁴⁸Ca-induced reactions, but no discovery has been confirmed to date. In this work, mass and angle distributions of fission fragments from these reactions have been measured with large angular coverage to aid in selection of the most promising projectile-target combination that would favor fusion. The results yield information on reaction contact times, with the longest exhibited by ⁵⁰Ti+²⁴⁹Cf.
Interplay of neutron–proton equilibration and nuclear dynamics
2019, Progress in Particle and Nuclear Physics
Neutron–proton equilibration in heavy-ion collisions proceeds atop a landscape of deformed topography and large density changes. The rapidly-varying landscape is created by the collision dynamics. The collision dynamics influences the neutron–proton equilibration, but just as importantly the different migration of the protons and neutrons influences the dynamics. To fully appreciate either the reaction dynamics or the neutron–proton equilibration, one must understand both. This review explores decades of work on both topics, and highlights the connections to the nuclear equation of state in nuclear experiment, theoretical prediction, and astrophysical observation.
Shell effects in quasi-fission in reactions forming <sup>226</sup>Th compound nucleus
2024, arXiv

View all citing articles on Scopus

¹: Present address: Research Center for Nuclear Physics, Osaka University, Mihogaoka 10-1, Ibaraki, Osaka 567, Japan.

View full text

A position sensitive time of flight detector for heavy ion ERD
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 371, 2016, pp. 125-131
S. Eschbaumer, …, G. Dollinger
Fabrication and characterization of thin $^{142, 150}$ Nd targets for the study of dynamics of heavy-ion induced reactions
Vacuum, Volume 186, 2021, Article 110053
Saumyajit Biswas, …, A. Chakraborty
Test of microchannel plates in magnetic fields up to 4.5 T
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Volume 845, 2017, pp. 588-590
A. Yu Barnyakov, …, A.A. Katcin
Separated flow operation of the SHARAQ spectrometer for in-flight proton-decay experiments
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Volume 830, 2016, pp. 233-242
M. Dozono, …, S. Shimoura
Using pulse shape analysis to improve the position resolution of a resistive anode microchannel plate detector
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Volume 804, 2015, pp. 144-148
Davinder Siwal, …, R.T deSouza
Time of flight assisted $Δ E - E$ method for enhanced isotope separation capabilities in heavy ion elastic recoil detection analysis
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 406, Part A, 2017, pp. 10-14
S. Eschbaumer, …, G. Dollinger

Mass-split dependence of the pre- and post-scission neutron multiplicities for fission of 251Es

Abstract

Phys. Rev. Lett.

erratum

Phys. Rev. Lett.

Nucl. Instr. Meth.

Phys. Rev.

Phys. Rev. Lett.

Phys. Lett.

Nucl. Phys.

Phys. Rev.

Phys. Rev.

Nucl. Phys.

Phys. Rev. Lett.

erratum

Phys. Rev.

Nucl. Phys.

Phys. Rev.

Nucl. Phys.

Phys. Rev.

Z. Phys.

Z. Phys.

Mass-split dependence of the pre- and post-scission neutron multiplicities for fission of ²⁵¹Es