arXiv subjects

Long Zhu

Publications and source records attributed to Long Zhu.

31 records · Page 2Linked to original sources

arXiv2023

Deep insight into charge equilibration and the effects on producing neutron-rich isotopes around N = 126 in the multinucleon transfer reactions

The dynamics of the charge equilibration (CE) and the effects on the production of the neutron-rich isotopes around $N = 126$ in multinucleon transfer reactions are still not well understood. In this Letter, we investigate the mechanism of the CE from different viewpoints by using the extended version of the dinuclear system model (DNS-sysu) and the improved quantum molecular dynamics (ImQMD) model. From the macroscopic and microscopic dynamical viewpoints, we find incomplete CE for the mass asymmetry reaction systems even in the very deep collisions, and the behavior of "inverse CE" that the tendency of the fragments is away from the $N/Z$ value of the compound system in the reaction $^{140}$Xe + $^{198}$Pt. Unlike the slow process presented in the ImQMD model, the behavior of fast equilibration with the characteristic time $\sim$ 0.52 zs is obtained based on the DNS-sysu model, which is consistent with the experimental data. By performing the systematic calculation, the correlation between the CE and the mass asymmetry of the reaction systems is clarified, which not only accounts for the observed intriguing phenomena of the CE but also provides essential information for producing the neutron-rich isotopes around $N = 126$.

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arXiv2023

The optimal detection angles for producing N=126 neutron-rich isotones in the multinucleon transfer reactions

The challenge of isotopic identification over a wide angular distribution has limited the measurement of neutron-rich nuclei produced via the multinucleon transfer (MNT) process. To investigate the optimal detection angles for the N=126 isotones, we propose a method to construct the reasonable scattering angles of the MNT products in the dinuclear system (DNS-sysu) model. The reactions $^{136,144}$Xe + $^{208}$Pb are investigated. The calculated results are in rather good agreement with the available experimental data in the reaction $^{136}$Xe + $^{208}$Pb. The entrance channel effects on the scattering angle are investigated. It is found that the scattering angular distribution strongly depends on the isospin and the impact parameter of the collision system. The optimal angle ranges for detecting $N=126$ neutron-rich nuclides $^{204}$Pt, $^{203}$Ir, $^{202}$Os, and $^{201}$Re in the $^{136}$Xe + $^{208}$Pb reaction at the incident energy $E_{c.m.} = 526MeV$ are predicted. Our results suggest that the angle range $45^{\circ} \leqslant θ_{\mathrm{lab}} \leqslant 50^{\circ}$ is most favorable for detecting unknown N=126 isotones. Given the current difficulties in separating and identifying experimental MNT fragments, the results of this work could provide significant contributions to future experiments.

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arXiv2023

Temperature of the hot $α$-source: a guidance to probe the Bose-Einstein condensation of $α$ clusters in the heavy-ion collision

Recent experimental efforts were made to explore the Bose-Einstein condensation in multi-$α$ system using the heavy-ion collisions. This Letter provides a explanation why no signatures were observed and a guidance for future experiments. More precisely, a harmonic oscillator model is developed to study the multi-$α$ source at or near zero temperature. The temperature and particle population of the multi-$α$ sources observed in the current experiments are extracted. It is found that almost no $α$ particles occupy the ground state in those multi-$α$ sources. The critical temperature for the multi-$α$-condensed states are predicted, which provides a guidance for the future experiments to probe the Bose-Einstein condensation of $α$ clusters in the heavy-ion collisions.

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arXiv2022

A tensor decomposition model for evaluating isotopic yield in neutron-induced fission

After constructing yield tensors with three dimensions for 851 fission products and filling the tensors with the independent yield data from the ENDF/B-VIII.0 database, the tensor decomposition algorithm is applied to predict the independent isotopic yield in fission, which resulting in the Fission Yield Tensor Decomposition (FYTD) model. The fission yields of 235U and 239Pu are set as missing values and then predicted. The predictions for235U fissions by the FYTD model agree with the ENDF/B-VIII.0 data and are better than those by the Talys and BNN+Talys models. Furthermore, we predict not only the mass distribution but also the isotopic yields in the fissions. For fast neutron-induced fission of 239Pu, 98% predictions of the isotopic yields by the FYTD model agree with the ENDF/B-VIII.0 data within 1 order of magnitude. The fission yields of 238Np, 243Am, and 236Np that do not exist in the ENDF/B-VIII.0 database are predicted and compared with those in the JEFF-3.3 database, as well as the experimental data. Good agreement demonstrates the predictive ability of the FYTD model for the target nucleus dependence. The scalability of the yield tensor decomposition model over the incident neutron energy degrees of freedom is examined. After adding a set of 2 MeV neutron-induced 239Pu fission yield data into the yield tensor, the 2 MeV neutron-induced fission yields of 235U and 239Pu are predicted. The comparison with the experimental data shows that the predictions are similar to those by the GEF model in the peak area but more accurate in the valley area. Finally, the yields of the ratio of isomeric states and neutron excess of the products as a function of product charge number are also studied. The FYTD model can capture the multi-dimensional dependence of the fission yield data and make reasonable predictions.

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arXiv2020

Providing physics guides in Bayesian neural networks from input layer: case of giant dipole resonance predictions

The Bayesian neural network (BNN) has been applied to evaluate and predict the nuclear data. However, how to provide physics guides in BNN is a key but an open question. In this work, the case study on giant dipole resonance (GDR) energy is presented to illustrate the effectiveness and maneuverability of the method to provide physics guides in BNN from input layer. The Spearman's correlation coefficients are applied to assess the statistical dependence between nuclear properties in the ground state and the GDR energies. Then the optimal ground-state properties are employed as the input layer in the BNN for evaluating and predicting the GDR energies. Those selected ground-state properties actively contributes to reduce the predicted errors and avoid the risk of the non-physics divergence. This work gives a demonstration to find effects of the GDR energy by using the BNN without the physics motivated model, which may be helpful for discovering physics effects from the complex nuclear data.

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arXiv2019

Selection of projectiles for producing trans-uranium nuclei in transfer reactions within an improved dinuclear system model

The multinucleon transfer process is one promising approach for producing neutron-rich heavy nuclei. The favorable projectile-target combinations play a key role in experiments. As one important approach to investigate the multinucleon transfer process, one new version of the dinuclear system (DNS) model is developed. The improved version of the DNS model is shown in detail. Based on deformation degree of freedom in the improved DNS model, one way of calculating excitation energies of primary fragments is proposed. And the remarkable improvements for describing experimental data of producing trans-uranium nuclei is noticed. To produce trans-uranium nuclei, the collisions of 48Ca, 136Xe, and 238U projectiles with the 238U target are investigated within the improved DNS model. Based on the potential energy surface, the influence of projectiles on the probabilities of transferring neutrons and protons from the projectiles to the target are studied. One behavior is found that the transfer probabilities strongly depend on the projectiles in the neutron stripping process, while relatively weak projectile dependence is noticed in the proton transferring process. The 136Xe and 238U projectiles show great advantages of cross sections for producing neutron-rich trans-uranium nuclei, although the fission probabilities are large.

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arXiv2019

Advantages of the multinucleon transfer reactions based on 238U target for producing neutron-rich isotopes around N = 126

The mechanism of multinucleon transfer (MNT) reactions for producing neutron-rich heavy nuclei around N = 126 is investigated within two different theoretical frameworks: dinuclear system (DNS) model and isospin-dependent quantum molecular dynamics (IQMD) model. The effects of mass asymmetry relaxation, N=Z equilibration, and shell closures on production cross sections of neutron-rich heavy nuclei are investigated. For the first time, the advantages for producing neutron-rich heavy nuclei around N = 126 is found in MNT reactions based on 238U target. We propose the reactions with 238U target for producing unknown neutron-rich heavy nuclei around N = 126 in the future.

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arXiv2018

Dynamical properties and secondary decay effects of projectile fragmentation in 107,124Sn + 120Sn collisions at 600 MeV/nucleon

The formation of the projectile spectator and the fragmentation processes in 107,124Sn + 120Sn collisions at 600 MeV/nucleon are studied with the isospin-dependent quantum molecular dynamics (IQMD) model. The minimum spanning tree algorithm and the ratio of parallel to transverse kinetic quantities are applied to identify the equilibrated projectile spectator during the dynamical evolution. The influence of secondary decay on fragmentation observables is investigated by performing calculations with and without the statistical code GEMINI. The validity of the theoretical approach is examined by comparing the calculated product yields and correlations with the experimental results of the ALADIN Collaboration for the studied reactions.

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arXiv2018

Production cross sections for exotic nuclei with multinucleon transfer reactions

The main progresses in the multinucleon transfer reactions at energies close to the Coulomb barrier are reviewed. After a short presentation of the experimental progress and theoretical progress,the predicted production cross sections for unknown neutron-rich heavy nuclei and the trans-uranium nuclei are presented.

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arXiv2018

Free-Space Data-Carrying Bendable Light Communications

Bendable light beams have recently seen tremendous applications in optical manipulation, optical imaging, optical routing, micromachining, plasma generation and nonlinear optics. By exploiting curved light beams instead of traditional Gaussian beam for line-of-sight light communications, here we propose and demonstrate the viability of free-space data-carrying bendable light communications along arbitrary trajectories with multiple functionalities. By employing 39.06-Gbit/s 32-ary quadrature amplitude modulation (32-QAM) discrete multi-tone (DMT) signal, we demonstrate free-space bendable light intensity modulated direct detection (IM-DD) communication system under 3 different curved light paths. Moreover, we characterize multiple functionalities of free-space bendable light communications, including bypass obstructions transmission, self-healing transmission, self-broken trajectory transmission, and movable multi-receiver transmission. The observed results indicate that bendable light beams can make free-space optical communications more flexible, more robust and more multifunctional. The demonstrations may open a door to explore more special light beams enabling advanced free-space light communications with enhanced flexibility, robustness and functionality.

physics.optics↗

arXiv2016

Effects of entrance channel on fusion probability in hot fusion reactions

Within the framework of the dinuclear system (DNS) model, the fusion reactions leading to the compound nuclei 274Hs and 286Cn are investigated. The fusion probability as a function of DNS excitation energy is studied. The calculated results are in good agreement with the available experimental data. The obtained results show that the fusion probabilities are obviously enhanced for the reactions located at high place in potential energy surface, although these reactions may have small values of mass asymmetry. It is found that the enhancement is due to the large potential energy of the initial DNS.

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arXiv2016

Quantum-Classical Correspondence Principle for Work Distributions in a Chaotic System

We numerically study the work distributions in a chaotic system and examine the relationship between quantum work and classical work. Our numerical results suggest that there exists a correspondence principle between quantum and classical work distributions in a chaotic system. This correspondence was proved for one-dimensional (1D) integrable systems in a recent work [Jarzynski, Quan, and Rahav, Phys. Rev. X 5, 031038 (2015)]. Our investigation further justifies the definition of quantum work via two point energy measurements.

cond-mat.stat-mech↗

arXiv2015

Production of heavy neutron-rich nuclei in transfer reactions within the dinuclear system model

The dynamics of nucleon transfer processes in heavy-ion collisions is investigated within the dinuclear system model. The production cross sections of nuclei in the reactions $^{136}$Xe+$^{208}$Pb and $^{238}$U+$^{248}$Cm are calculated and the calculations are in good agreement with the experimental data. The transfer cross sections for the $^{58}$Ni+$^{208}$Pb reaction are calculated and compared with the experimental data. We predict the production cross sections of neutron-rich nuclei $^{165-168}$Eu, $^{169-173}$Tb, $^{173-178}$Ho, and $^{181-185}$Yb based on the reaction $^{176}$Yb+$^{238}$U. It can be seen that the production cross sections of the neutron-rich nuclei $^{165}$Eu, $^{169}$Tb, $^{173}$Ho, and $^{181}$Yb are 2.84 $μ$b, 6.90 $μ$b, 46.24 $μ$b, and 53.61 $μ$b, respectively, which could be synthesized in experiment.

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