Superheavy Nuclei Research Articles

The Study of Multi-Nucleon Transfer Reactions for Synthesis of New Heavy and Superheavy Nuclei

The Study of Multi-Nucleon Transfer Reactions for Synthesis of New Heavy and Superheavy Nuclei

Manifestation of Reflection-Asymmetric Deformation in the Structure of Superheavy Nuclei

Manifestation of Reflection-Asymmetric Deformation in the Structure of Superheavy Nuclei

The Fusion-by-Diffusion model as a tool to calculate cross sections for the production of superheavy nuclei

This article summarizes recent progress in our understanding of the reaction mechanisms leading to the formation of superheavy nuclei in cold and hot fusion reactions. Calculations are done within the Fusion-by-Diffusion (FBD) model using the new nuclear data tables by Jachimowicz et al. (At Data Nucl Data Tables 138, 101393, 2021). The synthesis reaction is treated in a standard way as a three-step process (i.e., capture, fusion, and survival). Each reaction step is analysed separately. Model calculations are compared with selected experimental data on capture, fissionlike and fusion cross sections, fusion probabilities, and evaporation residue excitation functions. The role of the angular momentum in the fusion step is discussed in detail. A set of fusion excitation functions with corresponding fusion probabilities is provided for cold and hot synthesis reactions.

Microscopically Derived Grodzins Relation and Prediction of the Excitation Energies of the $$2_{1}^{ + }$$ States for Some Superheavy Nuclei

Microscopically Derived Grodzins Relation and Prediction of the Excitation Energies of the $$2_{1}^{ + }$$ States for Some Superheavy Nuclei

An improved unified formula for alpha -decay and cluster radioactivity of heavy and superheavy nuclei

Improved NRDX empirical formula for alpha - and cluster decay half-lives is modified by adding the effects of angular momentum, isospin asymmetry and parity. The coefficients are determined using the latest experimental data for alpha -decay half-lives of 573 nuclei and the available 22 cluster decay half-lives. The modified formulas produced the alpha - and cluster decay half-lives and agree with calculations of other similar formulas. We used the new formulas to calculate the half-lives of cluster emissions of the SHN with Z=120, 122, 124, and 126, which have not yet been experimentally synthesized.

Exotic symmetries as stabilizing factors for superheavy nuclei: Symmetry-oriented generalized concept of nuclear magic numbers

We introduce the concept of the nuclear octupole fourfold (i.e., applying simultaneously to all the four octupole deformations ${\ensuremath{\alpha}}_{30}$, ${\ensuremath{\alpha}}_{31}$, ${\ensuremath{\alpha}}_{32}$, and ${\ensuremath{\alpha}}_{33}$) neutron ``magic number'' $N=196$ and discuss the physical consequences of its presence. Our theoretical predictions are obtained using the realistic phenomenological mean-field approach with the deformed Woods-Saxon potential, the latter employing the new parametrization optimized in our preceding articles. Correlations among 4 parameters in the set of 12 parameters of the Woods-Saxon potential are detected and removed employing Monte Carlo approach leading to stabilization of the predictive power of the modeling. Our main focus is examining the impact of the four-fold octupole magic number $N=196$ on the stability properties of superheavy nuclei with $114\ensuremath{\le}Z\ensuremath{\le}130$ and $166\ensuremath{\le}N\ensuremath{\le}206$. Calculations suggest that majority of the examined nuclei are either spherical or octupole deformed, octupole-tetrahedral geometry playing the dominating role lowering the ground-state energy by up to 8 MeV. The origin and manifestations of this domination are illustrated and discussed. It turns out that, in several cases, alternative point-group symmetries may lead to noticeable lowering of the nuclear energy; this concerns the ${C}_{2v}$ geometry associated with ${\ensuremath{\alpha}}_{31}$, the ${D}_{3h}$ geometry related to ${\ensuremath{\alpha}}_{33}$, and ${D}_{2d}$ corresponding to the combination of ${\ensuremath{\alpha}}_{32}$ and ${\ensuremath{\alpha}}_{20}$ quadrupole component.

Rules of thumb for synthesizing superheavy elements

Synthesizing any elements in the eighth period using either cold or hot fusion reactions remains a big challenge to date. The quasifission mechanism restricts complete fusion to an indeterminably low evaporation residue (ER) cross-section for superheavy nuclei. The entrance channel parameters of the heavy-ion reaction, the fission barrier of the compound nucleus, the deformation parameters of the projectile and target nuclei, and the kinetic energy of the projectile are mainly responsible for governing the scale of the quasifission. The role of these factors has been examined explicitly by the experimental ER cross-sections. Thorough comparisons lead us to infer that the entrance channel criteria contribute to a much lower extent than the deformation parameters do. The effect of deformation can be categorized into four rules as validated by all the reactions used except one Uue. The null result from this reaction is explained by the improper choice of the projectile energy, as shown theoretically by means of a statistical model approach, which is valid for a system having a large nucleon number so as to intrinsically have a high density of excited states. The optimal selection of the beam energy sets another rule. Therefore, these five rules can be treated as the rules of thumb for synthesizing the superheavy elements. Application of the first four rules can enable us primarily to spot a suitable reaction, and finally, exploitation of the fifth rule chooses the most appropriate reaction at a preferable excited energy to achieve the highest ER cross-section for a superheavy element.

Medium-dependent relativistic NN potential: Application to fusion dynamics

In-medium effects are introduced in the microscopic description of the effective nucleon-nucleon (NN) interaction potential entitled DDR3Y in terms of the density-dependent nucleon-meson couplings within the Relativistic-Hartree-Bogoliubov (RHB) approach. The nuclear densities of the interacting target and projectile nuclei and NN potentials are obtained for non-linear NL3$^*$ and TM1 parameter sets within the relativistic mean-field approach and density-dependent DDME1 and DDME2 parameter sets within the Relativistic-Hartree-Bogoliubov (RHB) formalism. The DDR3Y NN potential and the densities are used to obtain the nuclear potential by adopting the double folding approach. This nuclear potential is further used to probe the fusion dynamics within the $\ell-$summed Wong model for a few {\it even-even} systems leading to the formation of light, heavy and superheavy nuclei. The calculations are also performed for the relativistic R3Y, density-dependent and independent M3Y interaction potentials for the comparison. We observed that the DDR3Y NN potential gives a better overlap with the experimental data as compared to non-relativistic M3Y and DDM3Y NN potentials. From the comparison of R3Y and DDR3Y interactions, it is manifested that the inclusion of in-medium effects in terms of density-dependent nucleon-meson couplings raises the fusion barrier and consequently decreases the fusion and/or capture cross-section. Moreover, the nuclear densities, as well as the relativistic R3Y NN potential obtained for the NL3$^*$ parameter set, are observed to give a comparatively better fit to the experimental data.

Properties and synthesis of the superheavy nucleus Fl114298

The one-nucleon separation energy ${S}_{n}$, two-nucleon separation energy ${S}_{2n}$, one-proton separation energy ${S}_{p}$, two-proton separation energy ${S}_{2p}, \ensuremath{\alpha}$-decay energy ${Q}_{\ensuremath{\alpha}}, \ensuremath{\alpha}$-decay half-life and spontaneous fission half-life of $Z=114$ isotopes and $N=184$ isotones are calculated by the finite-range droplet model (FRDM2012). It is found that $N=184$ is a neutron magic number, and $Z=114$ is a proton magic number. The properties of $Z=114$ isotopes and $N=184$ isotones provide a vital signal that $_{114}^{298}\mathrm{Fl}$ may be a spherical double-magic nucleus and also the center of the stability island of superheavy nuclei. Based on this, we began to investigate the optimal conditions for the synthesis of superheavy nucleus $_{114}^{298}\mathrm{Fl}$ within the dinuclear system model. To produce such neutron-rich compound nucleus, we consider using the extremely neutron-rich radioactive beams to bombard actinide targets. The evaporation residue cross section of superheavy nuclei synthesized by radioactive beam is analyzed in detail. Finally, we suggest that for the synthesis of $_{114}^{298}\mathrm{Fl}$, the radioactive beam-induced fusion reaction $^{64}\mathrm{Ti}+^{238}\mathrm{U}$ in the $4n$ evaporation channel with an excitation energy of 43 MeV is optimal.

Experimental observation of the M1 scissors mode in 254No

We present the first experimental evidence of the scissors mode in the superheavy nucleus 254No produced in the 208Pb(48Ca, 2nγ))254No reaction. The spectrum of γ rays emitted by the excited 254No nuclei shows an enhanced γ-ray yield for transition energies of ≈2.5 MeV. By measuring the linear polarization properties of the emitted γ rays, we confirm that the transitions in the enhancement region are predominantly of magnetic-dipole character, characteristic for the scissors mode. To further characterize the enhanced γ-ray yield, simulations of the electromagnetic decay of 254No were performed. The observed enhancement is reproduced by including an M1 component in the γ strength function with total strength B(M1↑)=11.8(19)μN2. This is in good agreement with the integrated M1 strength from sum-rule estimates and new calculations within the quasi-particle random-phase approximation presented here. Our results provide a stringent test of phenomenological formulae for the scissors mode currently used in stellar nucleosynthesis calculations. We find that those formulae are not satisfactory, and we recommend using sum-rule estimates assuming a rigid-body moment of inertia instead for describing the scissors mode in superheavy nuclei.

Influence of Spin-Orbit Strength in Superheavy Nuclei

Influence of Spin-Orbit Strength in Superheavy Nuclei

Kinetic Energy Distribution in Multi-Step Neutron Emission from Superheavy Nuclei

Kinetic Energy Distribution in Multi-Step Neutron Emission from Superheavy Nuclei

ROLE OF ISOVECTOR-ISOSCALAR COUPLING ON CHARGE RADIUS OF HEAVY AND SUPERHEAVY NUCLEI

We have investigated the effect of the isovector-isoscalar coupling on the finite nuclei and nuclear matter properties, the neutron skin thickness of 208Pb, and the charge radius on heavy and superheavy nuclei calculated by the relativistic mean-field (RMF) model. In this work, we generates two parameter sets, i.e., PTE16 and PTE31. The numbers 16 and 31 denote the isovector-isoscalar coupling terms, while T and E denote the tensor coupling and electromagnetic exchange terms, respectively. We found that PTE16 and PTE31 are compatible with the constraints obtained by R. Essick, et al., arXiv: 2102.10074v1 [nucl-th] (2021). We also found that the increase of the isovector-isoscalar coupling terms gives a significant effect on the binding energy and the charge radius on heavy nuclei except for the charge radius of 208Pb. Increased of the isovector-isoscalar coupling terms make the values of charge radius prediction increase too, but vice versa for the neutron skin thickness and nuclear matter prediction. PTE31 yields symmetry energy J = 31.521 MeV, slope L = 57.643 MeV, and neutron skin thickness = 0.21419 fm. While the β2 correction (for deform nuclei) does not always give a significant effect on the charge radius.

Fission barriers of superheavy nuclei for emitted fragment isotopes near proton magic numbers

Fission barriers for supposed doubly magic $^{298}\mathrm{Fl}$ are calculated using a specialized binary macroscopic-microscopic method. The microscopic effects are obtained from the developed binary Strutinsky shell correction method. The main input data are the proton and neutron energy levels calculated with the deformed two-center shell model. One is able in this way to provide the microscopic transition via the level schemes, from the parent to two overlapped and finally separated level schemes. The macroscopic part is acquired by the deformed charged liquid drop model with the double Yukawa-plus-exponential finite range potential. The method is applied to the reactions accompanied by isotopes of Sn and Pb within the fission channels, as being favored by strongly negative shell corrections.

Predictions for the synthesis of the Z=120 superheavy element

The possible stable and radioactive beam-induced hot fusion reactions for the production of new superheavy element (SHE) $Z=120$ are investigated within the dinuclear system model. Our investigation shows that the reaction $^{45}\mathrm{Sc}+^{252}\mathrm{Es}$ has a relatively large evaporation residue cross-section (ERCS) for the synthesis of SHE $Z=120$ due to its slightly larger mass asymmetry. In addition, we analyzed the effects of fission barrier and neutron separation energy of superheavy nuclei on ERCS. To synthesize the double-magic $Z=120$ and $N=184$ nucleus predicted by the relativistic mean-field model, some radioactive beam-induced fusion reactions, which can be performed in available experimental equipment, for producing superheavy nucleus $^{304}120$ in neutron evaporation channels are investigated systematically. We find that the hot fusion reaction $^{50}\mathrm{Ca}+^{257}\mathrm{Fm}$ in the $3n$ evaporation channel is optimal for synthesizing the superheavy nucleus $^{304}120$. We hope these predictions will shed new light timely for the recent experiments on the synthesis of $Z=120$ superheavy element and the search for superheavy stability islands.

Fission channels for fragment isotopes from Fl298 with magic nucleon numbers

Short-lived systems such as superheavy nuclei decay mainly by $\ensuremath{\alpha}$ emission. However, fission fragment emission is also probable, as theoretical calculations prove it. $^{298}\mathrm{Fl}$ dynamics decay is studied with a specialized binary macroscopic-microscopic method combined with the mass inertia tensor. The multidimensional WKB tunneling method is used to obtain the penetrabilities and half-lives. The calculations are applied to fission channels around the isotopes of two presumably favored fragments, Pb and Sn. The choice is due to their proton magicity shell correction favorable fission valleys.

Experimental investigation of cross sections for the production of heavy and superheavy nuclei

Experimental investigation of cross sections for the production of heavy and superheavy nuclei

Unified description of α decay and cluster radioactivity using the neural network approach and universal decay law

The α decay and cluster radioactivity half-life of nuclei are calculated uniformly. The universal decay law (UDL) (Qi et al 2009 Phys. Rev. Lett. 103 072501) is refitted to include minimum angular momentum effect and unpaired nucleon effect. The UDL formula and neural network approach to describe α decay and cluster radioactivity half-life calculations were improved. We used the UDL formulas and neural network approach to predict the cluster radioactivity half-life of actinide nuclei and α decay half-life of superheavy nuclei Z = 117–120. We hope to contribute to the discovery of new atomic nucleus cluster radioactivity phenomena and theoretical studies of α decay of superheavy nuclei.

Phosphate Glass Detectors for Heavy Ion Identification

The problem of the boundaries of the Mendeleev table of chemical elements is closely related to the understanding of the properties of nuclear matter. In this regard, the synthesis of superheavy nuclei on accelerators and the registration of their decay products are of fundamental scientific interest. The Joint Institute of Nuclear Research in Dubna (JINR) conducts research on the synthesis of superheavy nuclei on the new DC-280 cyclotron (the Factory of Superheavy Elements). As part of the development of this experiment, the possibility of using phosphate glass as a material for detectors of heavy and superheavy nuclei is being considered. This issue requires test experiments to study the recording properties of the glass at different irradiation and treatment conditions. The article presents a method for identifying heavy ions in phosphate glass detectors under various conditions by the geometric characteristics of ion tracks. The results obtained indicate the possibility of using the KNFS-3 phosphate glass detectors for registration and identification of accelerated superheavy nuclei.

Production of neutron-rich heavy nuclei around $$N = 162$$ in multinucleon transfer reactions

Within the framework of the dinuclear system model, the production mechanism of neutron-rich heavy nuclei around \(N = 162\) has been investigated systematically. The isotopic yields in the multinucleon transfer reaction of \(^{238}\)U + \(^{248}\)Cm are analyzed and compared with the available experimental data at GSI. Systematics on the production of superheavy nuclei via the collisions of \(^{238}\)U on actinide nuclides \(^{252,254}\)Cf, \(^{254}\)Es and \(^{257}\)Fm is investigated thoroughly. It is found that the shell effect is of importance in the formation of neutron-rich nuclei around \(N~=~162\) owing to the enhancement of fission barrier and neutron separation energy. The fragments in the multinucleon transfer reactions manifest the broad isotopic distribution and are dependent on the beam energy. The polar angles of the fragments tend to the forward emission with increasing the beam energy. The production cross sections of new isotopes are estimated and the heavier targets are available for the neutron-rich superheavy nucleus formation. The optimal reaction system and beam energy are proposed for the future experimental measurements.