Fission Barrier Research Articles

Isospin composition of fission barriers

Isospin composition of fission barriers

Survival probabilities of compound superheavy nuclei towards element 119

To synthesize superheavy element 119 is becoming a highly concerned issue as several experimental projects in major laboratories are being pursued. This work studied the survival probabilities of compound superheavy nuclei after multiple neutron emissions based on microscopic energy dependent fission barriers, demonstrating a significant role of triaxial deformation in decreasing the first fission barriers in the heaviest region. Together with the fusion cross sections by the dinuclear system model, the optimal energy and the residual cross section of 243Am(48Ca, 3n)288Mc are reproduced. Finally the cross sections and optimal beam energies of 54Cr+243Am and 50Ti+249Bk reactions are estimated, providing clues for the synthesis of new elements.

Microscopic description of spontaneous fission based on a Gogny energy density functional including tensor contributions

This paper extends previous studies on the impact of tensor forces in fission dynamics of neutron-deficient Thorium isotopes to other isotopic chains of heavy actinides and low-mass super-heavy nuclei. Calculations are carried out within a mean-field framework based on the Gogny-D1S parametrization supplemented with the D1ST2a perturbative tensor term as driving force. Fission barrier heights and spontaneous fission half-lives are used as benchmarks to analyze the impact of the tensor term. A significant reduction of fission barrier heights and half-lives is associated with the tensor component of the force.

Machine learning study of fission barriers in superheavy nuclei

Machine learning study of fission barriers in superheavy nuclei

Examination of static fission properties of 236\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{236}$$\\end{document}U and 233\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{233}$$\\end{document}Th using Cassinian oval parametrization within the macroscopic–microscopic approach

We have conducted a thorough analysis of the potential energy surfaces (PES) in 236\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{236}$$\\end{document}U and 233\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{233}$$\\end{document}Th using the Cassini-ovals parameterization within the macro–micro approach. We employed the state-of-the-art immersion water flow (IWF) method to study the saddles on four-dimensional energy grids encompassing reflection-asymmetric shapes. For 233\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{233}$$\\end{document}Th, we computed the adiabatic potential energy surfaces by minimizing configurations with one blocked neutron within ten levels below and above the Fermi level. Our results show satisfactory agreement with empirical and experimental estimates for both nuclei, specifically regarding the first and second fission barriers. This suggests that our method holds promise in efficiently describing non-compact shapes while reducing the dimensionality of the space without sacrificing accuracy. Interestingly, employing Cassinian oval parameterization fails to reveal a pronounced, hyper-deformed third minimum in the potential energy landscape. Instead, only a shallow third minimum is observed for 233\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{233}$$\\end{document}Th, while in 236\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{236}$$\\end{document}U, this minimum ultimately vanishes. This finding holds significant importance when considering the modeling of fission cross-sections.

Small cross section of the synthesis of darmstadtium in the Ca48+Th232 reaction

The smallness of the cross section of evaporation residues formed in the hot fusion reaction Ca48+Th232 is analyzed by the dinuclear system model (DNS). The capture probability has been calculated by solving the dynamical equations of motion for the relative distance between the centers of mass of the DNS nuclei. Fusion of nuclei is considered as evolution of the DNS to a stable compound nucleus. The fusion probability has a bell-like shape and quasifission is one of reasons causing smallness of the yield of the evaporation residues products. Another reason is the decrease of the fission barrier for the isotopes Dm275–285 related with the shell effects in the neutron structure. The agreement of the theoretical results obtained for the yield of the evaporation residues with the experimental data measured in the Factory of Superheavy Elements of Joint Institute for Nuclear Research is well. Published by the American Physical Society 2024

Inner fission barriers of uranium isotopes in the deformed relativistic Hartree-Bogoliubov theory in continuum

Abstract The inner fission barriers of the even-even uranium isotopes from the proton to the neutron drip line are studied with the deformed relativistic Hartree-Bogoliubov theory in continuum. A periodic evolution for the ground state shapes is shown with the neutron number, i.e., spherical shapes at shell closures N=126, 184, 258, and prolate dominated shapes between them. In analogy to the shape evolution, the inner fission barriers also exhibit a periodic behavior: peaks at the shell closures and valleys in the mid-shells. The triaxial effect to the inner fission barrier is evaluated using the triaxial relativistic mean field calculations plus a simple BCS method for pairing. With the triaxial correction included, good consistency in the inner barrier heights is found with the available empirical data.
Besides, the evolution from the proton to the neutron drip line is in accord with the results by the multi-dimensionally constrained relativistic mean field theory. A flat valley in the fission barrier height is predicted around the neutron-rich nucleus 318U which may play a role of fission recycling in the astrophysical r-process nucleosynthesis.

A rumor propagation model based on nuclear fission

The propagation of online rumors is rapid, and its propagation mechanism has always been a research difficulty. In this paper, the network rumors are compared to the nuclear fission process, and a network rumors propagation model is constructed. First, the initial online rumors are compared to neutrons, uranium nuclei are compared to individual rumor receivers, and fission barriers are compared to individual active propagation thresholds. Second, the process of nuclear fission is analyzed and the degree of energy accumulation is used to compare the social impact of online rumors. Finally, the online rumor propagation model based on nuclear fission is constructed. Through experimental simulation, it has been shown that compared to classic infectious disease models, this model can better describe the propagation process of rumors in social networks. Through research and analysis, suggestions for suppressing rumors have been proposed, providing new ideas and references for future researchers.

Fission barriers with the Weizsäcker-Skyrme mass model* *Supported by the National Natural Science Foundation of China (12265006, U1867212) and the Guangxi Natural Science Foundation (2017GXNSFGA198001)

Based on the Weizsäcker-Skyrme (WS4) mass model, the fission barriers of nuclei are systematically studied. Considering the shell corrections, macroscopic deformation energy, and a phenomenological residual correction, the fission barrier heights for nuclei with can be well described, with an rms deviation of 0.481 MeV with respect to 71 empirical barrier heights. In addition to the shell correction at the ground state, the shell correction at the saddle point and its relative value are also important for both deformed and spherical nuclei. The fission barriers for nuclei far from the -stability line and super-heavy nuclei are also predicted with the proposed approach.

Fission valleys and favored isotopes emitted from 310\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{310}$$\\end{document}126

The decay channels for the superheavy nucleus 310\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{310}$$\\end{document}126 are studied under the binary macroscopic–microscopic method. The macroscopic part is calculated as the heavy-light interacting charged liquid drops, linked through the finite range Yukawa-plus-exponential force. The microscopic energy is calculated based on the spheroidally deformed two-center shell model. The proton and neutron single-particle levels are introduced in the binary Strutinsky procedure. The resulting shell corrections are added to the macroscopic part to obtain the fission barriers. The dynamical part follows by introducing the Werner–Wheeler inertia. The final lifetimes are calculated for all possible isotopic channels around the most favored heavy-light fragment pairs.

Effects of triaxial deformation on the fission barrier in the Z = 118 − 120 nuclei* *Supported by the National Natural Science Foundation of China (Grant Nos. 12205076 and 12047504), the China Postdoctoral Science Foundation (Grant No. 2020M670012), and the Launching Fund of Henan University of Technology (Grant No. 2021BS047).

By using potential energy surface (PES) calculations in the three-dimensional space (β 2, γ, β 4) within the framework of the macroscopic-microscopic model, the fission trajectory and fission barrier for Z = 118(Og), 119, 120 nuclei has been systematically investigated. The calculated PES includes macroscopic liquid-drop energy, microscopic shell correction and pairing correction. Taking the 294Og176 nucleus as an example, we discuss the next closed shell after Z = 82 and N = 126 with the calculated Woods–Saxon single-particle levels. Then, the results of PES in 294Og is illustrated from the (X, Y) scale to the (β 2, γ) scale. The γ degree of freedom reveals the shape evolution clearly during the fission process. The structure near the minimum and saddle point of the PES in the Z = 118, 119, 120 nuclei is demonstrated simultaneously. Based on the potential energy curves, general trends of the evolution of the fission barrier heights and widths are also studied. The triaxial deformation in these superheavy mass regions plays a vital role in the first fission barrier, showing a significant reduction in both triaxial paths. In addition, the model-dependent fission barriers of proton-rich nuclei 295Og, 296119, and 297120 are analyzed briefly. Our studies could be valuable for synthesizing the superheavy new elements in the forthcoming HIAF and other facilities.

Inflammatory lung injury is associated with endothelial cell mitochondrial fission and requires the nitration of RhoA and cytoskeletal remodeling

Higher levels of extracellular nicotinamide phosphoribosyltransferase (eNAMPT), a TLR4 agonist, are associated with poor clinical outcomes in sepsis-induced acute lung injury (ALI). Little is known regarding the mechanisms by which eNAMPT is involved in ALI. Our recent work has identified a crucial role for mitochondrial dysfunction in ALI. Thus, this study aimed to determine if eNAMPT-mediated inflammatory injury is associated with the loss of mitochondrial function. Our data show that eNAMPT disrupted mitochondrial bioenergetics. This was associated with cytoskeleton remodeling and the loss of endothelial barrier integrity. These changes were associated with enhanced mitochondrial fission and blocked when Rho-kinase (ROCK) was inhibited. The increases in mitochondrial fission were also associated with the nitration-mediated activation of the small GTPase activator of ROCK, RhoA. Blocking RhoA nitration decreased eNAMPT-mediated mitochondrial fission and endothelial barrier dysfunction. The increase in fission was linked to a RhoA-ROCK mediated increase in Drp1 (dynamin-related protein 1) at serine(S)616. Another TLR4 agonist, lipopolysaccharide (LPS), also increased mitochondrial fission in a Drp1 and RhoA-ROCK-dependent manner. To validate our findings in vivo, we challenged C57BL/6 mice with eNAMPT in the presence and absence of the Drp1 inhibitor, Mdivi-1. Mdivi-1 treatment protected against eNAMPT-induced lung inflammation, edema, and lung injury. These studies demonstrate that mitochondrial fission-dependent disruption of mitochondrial function is essential in TLR4-mediated inflammatory lung injury and identify a key role for RhoA-ROCK signaling. Reducing mitochondrial fission could be a potential therapeutic strategy to improve ARDS outcomes.

Determination of fission barrier height of Fr210 and Ra210 via neutron measurement

Fission barrier heights of short-lived nuclei away from line of β stability are not known reliably. Low-energy fission of Fr210 and Ra210, produced by (d,p) and (d,n) transfer reaction on the re-accelerated unstable beam Fr209 was investigated at HIE-ISOLDE. Four Timepix3 pixel detectors were installed on the body of the ACTAR TPC demonstrator chamber. Polyethylene converters were used for the detection of fast neutrons. Since no significant background was observed, it was possible to measure the spatial distribution of emitted neutrons reflecting the fission excitation function. Subsequent simulations employing the results of the code and available data on fission fragment distributions allowed to estimate directly the value of the fission barrier height for the neutron-deficient nucleus Fr210. This first direct measurement confirmed the reduction of the fission barrier compared to available theoretical calculations by 15–30%. Published by the American Physical Society 2024

Size limits and fission channels of doubly charged noble gas clusters.

Small, highly charged liquid droplets are unstable with respect to spontaneous charge separation when their size drops below the Rayleigh limit or, in other words, their fissility parameter X exceeds the value 1. The absence of small doubly charged atomic cluster ions in mass spectra below an element-specific appearance size na has sometimes been attributed to the onset of barrierless fission at X = 1. However, more realistic models suggest that na marks the size below which the rate of fission surpasses that of competing dissociative channels, and the Rayleigh limit of doubly charged van der Waals clusters has remained unchartered. Here we explore a novel approach to form small dicationic clusters, namely by Penning ionization of singly charged noble gas (Ng) clusters that are embedded in helium nanodroplets; the dications are then gently extracted from the nanodroplets by low-energy collisions with helium gas. We observe Ngn2+ ions that are about 40% smaller than previously reported for xenon and krypton and about 20% for argon. These findings suggest that fission barriers have been underestimated in previous theoretical work. Furthermore, we measure the size distributions of fragment ions that are produced by collisional excitation of mass-selected dications. At lowest collision gas pressure, dicationic Kr and Xe clusters that are smaller than previously observed are found to evaporate an atom before they undergo highly symmetric fission. The distribution of fragments resulting from fission of small dicationic Ar clusters is bimodal.

Fast proton-induced fission of 238U from threshold to 40 MeV

The fast proton-induced fission of 238U has been analyzed from the threshold up to 40 MeV. Fission observables and isotope production were analyzed using TALYS and our own programs. Fission process was described by Brosa model. In the fast proton interaction, residual nuclei by mean of different (p,p’), (p,xn), (p,xp), (p,xα) (x=1,2,…,n) and other processes are formed. In the case of 238U, residual nuclei can also fission, contributing to the investigated observables and isotope production. Comparing theoretical results and experimental data from literature, parameters of the optical potential, fission barrier and type of nucleus deformation were extracted. Cross sections and isotope yields obtained in neutron-induced fission process were compared with proton case and with EXFOR data.

Influence of temperature-dependent shell corrections on the prediction of production cross sections for superheavy nuclei

In the framework of the dinuclear system model, we introduce a formula accounting for temperaturedependent shell corrections to assess their influence on the fission barrier calculations and, consequently, the survival probability of excited nuclei. Our approach considers the excitation energy’s effect on the fission barrier, a crucial aspect in determining the likelihood of a nucleus persisting. Leveraging experimental data with associated errors, we constrain the region of the shell correction damping factor. Employing this refined methodology, we predict the production cross sections for the novel superheavy element (SHE) with atomic number Z=119. Specifically, at the 54Cr(243Am,3n)294119 reaction, cross sections are anticipated to range between 3-27 femtobarns (fb), while for the 51V(248Cm,3n)296119 reaction, they are projected to span 21-180 fb. These predictions offer valuable insights into the formation dynamics of this exotic superheavy element.

Complete kinematics studies of fission reactions induced by quasi-free nucleon scattering collisions

Measurements of spallation, fragmentation and Coulomb-induced fission reactions in inverse kinematics have provided valuable data in the last decades to accurately investigate the fission dynamics and nuclear structure at large deformations of a large variety of stable and non-stable heavy nuclei. To go further, quasi-free scattering (QFS) reactions in inverse kinematics are proposed as a new surrogate method to induce fission, which allows to reconstruct the excitation energy of compound fissioning systems by using the four-momenta of the two outgoing nucleons. This new approach would permit therefore to correlate the excitation energy with the charge and mass distributions of the fission fragments and with the fission probabilities, given for the first time direct access to the simultaneous measurement of the fission yield dependence on temperature and fission barrier heights of exotic heavy nuclei, respectively. The first experiment based on this approach was recently performed at the GSI/FAIR facility and a description of the methodology based on model calculations is given here.

Cluster aspects of collinear cluster tri-partition (CCT)

New results demonstrating the so-called Ni-bump being the most populated mode of the collinear cluster tripartition (CCT) of 252Cf(sf) are presented. The physical scenario of this effect is discussed. It is tested by calculations of potential energy surfaces for the fission of the intermediate fragments formed after first rupture of the mother nucleus. Fission barriers are extracted and mass asymmetries at saddles are compared with the masses of the fission fragments that take part in the Ni-bump.

Progress on Brussels-Skyrme atomic mass models on a grid: stiff neutron matter equation of state

We report here the current developments on the Brussels-Skyrme-on-a-Grid (BSkG) atomic mass models. In comparison with our previous models, BSkG3 improves the infinite nuclear matter (INM) properties which opens its applications to neutron stars. The results presented here show that BSkG3 preserve the excellent agreement with experimental nuclear masses and radii, together with fission barriers of actinides obtained by BSkG1 and BSkG2, while the nuclear matter properties are considerably improved.

Deformation studies on thorium isotopes

The study of the deformation on thorium nuclei are important in nuclear physics due to its fissile nature. Thermally fissile isotopes have importance in energy production. The quadrupole and hexadecapole deformation parameters are important as they provide information on nuclear shape, size and moments of nuclei. The shape degree of freedom plays an important role in determining the fission barrier. In the present study, the quadrupole and hexadecapole deformation parameters of thorium nuclei were estimated by using the relativistic mean-field theory, with density dependent meson exchange interaction DD-ME2 and the density dependent point-coupling interaction DD-PC1. The estimated results of quadrupole deformation parameter are comparable with the available data and the minima point towards the neutron numbers N=126 and 184. The hexadecapole deformation parameter of thorium nuclei are positive along the stability line, negative towards the drip lines and zero at neutron number N=126 and 184.