Effects of nuclear orientation on the mass distribution of fission fragments in the reaction of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mmultiscripts><mml:mi mathvariant="normal">S</mml:mi><mml:mprescripts /><mml:none /><mml:mrow><mml:mn>36</mml:mn></mml:mrow></mml:mmultiscripts><mml:mo>+</mml:mo><mml:mmultiscripts><mml:mi mathvariant="normal">U</mml:mi><mml:mprescripts /><mml:none /><mml:mrow><mml:mn>238</mml:mn></mml:mrow></mml:mmultiscripts></mml:math>

Nishio, K.; Ikezoe, H.; Mitsuoka, S.; Nishinaka, I.; Nagame, Y.; Watanabe, Yutaka; Ohtsuki, T.; Hirose, K.; Hofmann, S.

doi:10.1103/physrevc.77.064607

Cited by 118 publications

(109 citation statements)

References 21 publications

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“…In this case, each orientation of the deformed nucleus may encounter a different mean-field evolution [82,83]. Such orientation dependence of reaction mechanisms has been experimentally studied in quasifission with actinide targets [84][85][86][87][88][89][90] and confirmed in TDHF studies [25,33,42]. In particular, these studies have shown that collisions of a spherical projectile with the tip of prolately deformed actinides lead to fast quasifission (with contact time smaller than 10 zs) while collisions with the side of the actinide may induce longer contact times, larger mass transfer, and possible fusion.…”

Section: Formalism a Tdhf And Dc-tdhf Approachesmentioning

confidence: 99%

Shape evolution and collective dynamics of quasifission in the time-dependent Hartree-Fock approach

2015

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Background: At energies near the Coulomb barrier, capture reactions in heavy-ion collisions result either in fusion or in quasifission. The former produces a compound nucleus in statistical equilibrium, while the second leads to a reseparation of the fragments after partial mass equilibration without formation of a compound nucleus. Extracting the compound nucleus formation probability is crucial to predict superheavy-element formation crosssections. It requires a good knowledge of the fragment angular distribution which itself depends on quantities such as moments of inertia and excitation energies which have so far been somewhat arbitrary for the quasifission contribution.Purpose: Our main goal is to utlize the time-dependent Hartee-Fock (TDHF) approach to extract ingredients of the formula used in the analysis of experimental angular distributions. These include the moment-of-inertia and temperature.Methods: We investigate the evolution of the nuclear density in TDHF calculations leading to quasifission. We study the dependence of the relevant quantities on various initial conditions of the reaction process.Results: The evolution of the moment of inertia is clearly non-trivial and depends strongly on the characteristics of the collision. The temperature rises quickly when the kinetic energy is transformed into internal excitation. Then, it rises slowly during mass transfer.Conclusions: Fully microscopic theories are useful to predict the complex evolution of quantities required in macroscopic models of quasifission.

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Section: Formalism a Tdhf And Dc-tdhf Approachesmentioning

confidence: 99%

Shape evolution and collective dynamics of quasifission in the time-dependent Hartree-Fock approach

2015

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“…Many experimental studies have been performed to understand the mechanisms at play in the quasi-fission process since its discovery [11][12][13][14][15][16][17][18][19]. Various theoretical models [20][21][22] have also been developed to help in the interpretation of these experimental data.…”

Section: Pb Targets Ormentioning

confidence: 99%

Dissipative dynamics in quasifission

Oberacker¹,

Umar²,

Simenel³

2014

Phys. Rev. C

113

158

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“…To define the smooth trends in quasifission, a large number of MAD measurements have been selected, for beam energies somewhat above the capture barrier (typically by ∼ 6%). Here the known effects of deformation alignment [10,11,17,19] and shell structure observed in measurements at below-barrier energies [14,20] are much reduced [11,21,22]. However the beam energies should not be too far above the capture barriers, otherwise high angular momenta would be introduced in the collisions, which would then not be representative of heavy element formation reactions.…”

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Systematic study of quasifission characteristics and timescales in heavy element formation reactions

Hinde

Williams

Mohanto

et al. 2016

EPJ Web of Conferences

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Superheavy elements can only be created in the laboratory by the fusion of two massive nuclei. Mass-angle distributions give the most direct information on the characteristics and time scales of quasifission, the major competitor to fusion in these reactions. The systematics of 42 mass-angle distributions provide information on the global characteristics of quasifission. Deviations from the systematics reveal the major role played by the nuclear structure of the two colliding nuclei in determining the reaction outcome, and in hindering or favouring heavy element production.To form very heavy and superheavy elements (SHE), heavy-ion fusion reactions are used. Their cross sections can be significantly suppressed [1] by quasifission [2]. This dynamical non-equilibrium process results when the combined system formed after capture separates into two (fission-like) fragments in times ∼10 −20 s, before a compact compound nucleus is formed. The probability of quasifission (P QF ) can be very large, with the corresponding probability of compound nucleus formation (P CN = 1 -P QF ) being lower than 10 −3 in unfavourable cases. Understanding the competition between quasifission and fusion is thus very important in predicting the best fusion reactions to use to form new isotopes of heavy and super-heavy elements.A key quantity characterizing quasifission is its "sticking time" between capture of the two nuclei inside the entrance channel potential barrier [4] and breakup (scission). Quasifission mass-angle distributions (MAD) first measured at GSI in the 1980s [2,5] showed that quasifission timescales could often be shorter than the rotation time of ∼10 −20 s. However, subsequently only a few measurements [6,7] were made until recent years, when an extensive series of experiments (using the Australian National University Heavy Ion Accelerator Facility and CUBE spectrometer) were carried out [3,[8][9][10][11][12][13][14][15][16]. The kinematic coincidence technique used in the measurements [2,3,17] provides direct information on the mass-ratio of the fragments at scission; thus, the data are represented in terms of mass ratio M R , rather than pre-or According to the characteristics of the MAD (minimum mass yield at symmetry, mass-angle correlation with peak yield at symmetry, and no significant mass-angle correlation), they are assigned as type MAD1, MAD2 and MAD3 respectively [3]. There is a clear correlation between the MAD class and the entrance channel charge product. Other entrance channel characteristics are important in determining the sticking times and MAD characteristics, including neutron richness [14,18], and shell structure including static deformation [11] and magic numbers [14].To improve our quantitative understanding of the role of shell structure in the dynamics of quasifission, we make an analogy with the liquid drop model approach to nuclear masses, in which localized shell effects can be quantified when the underlying smooth (liquid drop) trends are well defined. To define the smooth trends in ...

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Effects of nuclear orientation on the mass distribution of fission fragments in the reaction ofS36+U238

Cited by 118 publications

References 21 publications

Shape evolution and collective dynamics of quasifission in the time-dependent Hartree-Fock approach

Shape evolution and collective dynamics of quasifission in the time-dependent Hartree-Fock approach

Dissipative dynamics in quasifission

Systematic study of quasifission characteristics and timescales in heavy element formation reactions

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