Fusion and quasi-fission dynamics in nearly-symmetric reactions

Wang, Ning; Zhao, Kai; Li, Zhuxia

doi:10.1007/s11433-015-5726-z

Cited by 12 publications

(11 citation statements)

References 56 publications

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“…On the other hand, different theoretical approaches have also been developed: e.g. a dynamical model based on Langevin-type equations of motion [5][6][7][8][9][10][11][12], dinuclear system model (DNS) [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28], and improved quantum molecular dynamics model (ImQMD) [29][30][31][32][33][34][35][36][37][38]. Although those models can describe both peripheral and damped collisions, including fusion and quasifission (QF) processes, they are to some extent empirical containing model parameters.…”

Section: Introductionmentioning

confidence: 99%

Microscopic description of production cross sections including deexcitation effects

Sekizawa

2017

Phys. Rev. C

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Background: At the forefront of the nuclear science, production of new neutron-rich isotopes is continuously pursued at accelerator laboratories all over the world. To explore the currently-unknown territories in the nuclear chart far away from the stability, reliable theoretical predictions are inevitable.Purpose: To provide a reliable prediction of production cross sections taking into account secondary deexcitation processes, both particle evaporation and fission, a new method called TDHF+GEMINI is proposed, which combines the microscopic time-dependent Hartree-Fock (TDHF) theory with a sophisticated statistical compoundnucleus deexcitation model, GEMINI++.Methods: Low-energy heavy ion reactions are described based on three-dimensional Skyrme-TDHF calculations. Using particle-number projection method, production probabilities, total angular momenta, and excitation energies of primary reaction products are extracted from the TDHF wavefunction after collision. Production cross sections for secondary reaction products are evaluated employing GEMINI++. Results are compared with available experimental data and widely-used GRAZING calculations. Results:The method is applied to describe cross sections for multinucleon transfer processes in MeV) reactions at energies close to the Coulomb barrier. It is shown that the inclusion of secondary deexcitation processes, which are dominated by neutron evaporation in the present systems, substantially improves agreement with the experimental data. The magnitude of the evaporation effects is very similar to the one observed in GRAZING calculations. TDHF+GEMINI provides better description of the absolute value of the cross sections for channels involving transfer of more than one protons, compared to the GRAZING results. However, there remain discrepancies between the measurements and the calculated cross sections, indicating a limit of the theoretical framework that works with a single mean-field potential. Possible causes of the discrepancies are discussed. Conclusions:In order to perfectly reproduce experimental cross sections for multinucleon transfer processes, one should go beyond the standard self-consistent mean-field description. Nevertheless, the proposed method will provide valuable information to optimize production mechanisms of new neutron-rich nuclei through its microscopic, non-empirical predictions.

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Section: Introductionmentioning

confidence: 99%

Microscopic description of production cross sections including deexcitation effects

Sekizawa

2017

Phys. Rev. C

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“…The GRAZING has recently been extended to incorporate transfer-induced fission, which is referred to as GRAZING-F [26]. To describe damped collisions, a dynamical model based on Langevin-type equations [9][10][11][12][13][27][28][29][30], the dinuclear system (DNS) model [14][15][16][17][31][32][33][34][35][36][37][38], and the improved quantum molecular dynamics model (ImQMD) [39][40][41][42][43][44] have been extensively developed. Despite numerous successes in describing measurements, they are to some extent empirical, containing adjustable parameters.…”

Section: Introductionmentioning

confidence: 99%

Time-dependent Hartree-Fock calculations for multinucleon transfer and quasifission processes in theNi64+U238reaction

2016

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Background: Multinucleon transfer (MNT) and quasifission (QF) processes are dominant processes in lowenergy collisions of two heavy nuclei. They are expected to be useful to produce neutron-rich unstable nuclei. Nuclear dynamics leading to these processes depends sensitively on nuclear properties such as deformation and shell structure.Purpose: We elucidate reaction mechanisms of MNT and QF processes involving heavy deformed nuclei, making detailed comparisons between microscopic time-dependent Hartree-Fock (TDHF) calculations and measurements for the 64 Ni+ 238 U reaction.Methods: Three-dimensional Skyrme-TDHF calculations are performed. Particle-number projection method is used to evaluate MNT cross sections from the TDHF wave function after collision.Results: Fragment masses, total kinetic energy (TKE), scattering angle, contact time, and MNT cross sections are investigated for the 64 Ni+ 238 U reaction. They show reasonable agreements with measurements. At small impact parameters, collision dynamics depends sensitively on the orientation of deformed 238 U. In tip (side) collisions, we find a larger (smaller) TKE and a shorter (longer) contact time. In tip collisions, we find a strong influence of quantum shells around 208 Pb.Conclusions: It is confirmed that the TDHF calculations reasonably describe both MNT and QF processes in the 64 Ni+ 238 U reaction. Analyses of this system indicate the significance of the nuclear structure effects such as deformation and quantum shells in nuclear reaction dynamics at low energies.

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“…The main shortcoming of empirical CC approaches is the choice of the distribution function of barriers which are responsible for couplings of relative motion to intrinsic degrees of freedom. In most of the empirical CC approaches, the barrier distribution has only one maximum, while the experimental barrier distributions extracted from the capture excitation functions, i. been also used to explore the fusion dynamics [50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65]. In recent years, Sargsyan et al developed a quantum diffusion approach [66][67][68] for describing the capture process, which is based on the quantum master equation for the reduced density matrix.…”

Section: Introductionmentioning

confidence: 99%

Systematics of capture and fusion dynamics in heavy-ion collisions

Wang

Wen

Zhao

et al. 2017

Atomic Data and Nuclear Data Tables

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We perform a systematic study of capture excitation functions by using an empirical coupled-channel model. In this model, a barrier distribution is used to take effectively into account the effects of couplings between the relative motion and intrinsic degrees of freedom. The shape of the barrier distribution is of an asymmetric Gaussian form. The effect of neutron transfer channels is also included in the barrier distribution. Based on the interaction potential between the projectile and the target, empirical formulas are proposed to determine the parameters of the barrier distribution.Theoretical estimates for barrier distributions and calculated capture cross sections together with experimental cross sections of 220 reaction systems with 182 Z P Z T 1640 are tabulated. The results show that our empirical formulas work quite well in the energy region around the Coulomb barrier. This model can provide prediction of capture cross sections for the synthesis of superheavy nuclei as well as valuable information on capture and fusion dynamics.

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Fusion and quasi-fission dynamics in nearly-symmetric reactions

Cited by 12 publications

References 56 publications

Microscopic description of production cross sections including deexcitation effects

Microscopic description of production cross sections including deexcitation effects

Time-dependent Hartree-Fock calculations for multinucleon transfer and quasifission processes in theNi64+U238reaction

Systematics of capture and fusion dynamics in heavy-ion collisions

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