Dinuclear System Research Articles

Fission within dinuclear system approach

The improved scission-point statistical model based on the dinuclear system approach is employed to describe spontaneous fission, electromagnetic-, neutron-, charged-particle- and heavy-ion-induced fission of even–even pre-actinides, actinides and superheavy nuclei and to analyze the correlations between various observables. The key element of the model is the calculation of potential energy surfaces. The evolution of fission observables with increasing excitation energy is shown to be related with the widening and migration of the minima in the potential energy surface. Conservation of asymmetric shapes of mass and charge distributions of the fission fragments at high enough excitation energies of fissioning nuclei Hg, Pb, Rn, Ra, Th, U, Cf, Fm and No is predicted. At some critical excitation energy, the saturation of the symmetric component of charge and mass yields is demonstrated. For fissioning [Formula: see text]Hg, [Formula: see text]Fm and [Formula: see text]No, transitions from two-peaked to single-peaked mass distributions are predicted. The origin of the transition between asymmetric and symmetric fission modes with variations of neutron number and excitation energy is explored. For [Formula: see text]Hg(i.f.), [Formula: see text]Hg(i.f.), [Formula: see text]Fm(i.f.), [Formula: see text]Fm([Formula: see text], [Formula: see text]) and [Formula: see text]Fm(s.f.), the unexpected difference (symmetric or asymmetric) between the shapes of charge and mass distributions is predicted for the first time. The dependence of the neutron excess ratio of fission fragments on the fragment charge number is studied. A method is suggested for experimental verification of the multi-chance fission assumption. A possible explanation of the anomaly in charge yield of Mo/Sn fragments in the fission reaction [Formula: see text]U([Formula: see text], [Formula: see text]) at low excitation energies found by [Formula: see text]–[Formula: see text] coincidence spectroscopy is presented.

A new dynamical mechanism of incomplete fusion in heavy-ion collisions

The incomplete fusion has been proved as the emission of the α particle from the very mass-asymmetric state the dinuclear system during its evolution to complete fusion which is hindered due to the increase in the intrinsic fusion barrier related with the large rotational energy. The results of the dinuclear system model have confirmed that the incomplete fusion in heavy-ion collisions occurs at a large orbital angular momentum (L>30ħ) when the sufficient part of the initial collision energy removes as centrifugal energy.

From a Dinuclear System to Close Binary Cosmic Objects

Applying the ideas from microscopic objects to macroscopic stellar and galactic systems, the evolution of compact di-stars and di-galaxies is studied in the mass asymmetry coordinate. The formation of stable binary systems is analyzed. The role of symmetrization of an initially asymmetric binary system is revealed in the transformation of gravitational energy into internal energy of stars or galaxies accompanied by the release of a huge amount of energy. For the contact binary stars, the change of the orbital period is explained by evolution to symmetry in mass asymmetry coordinates. The matter transfer in binary black holes is studied. The conditions for the merger of black holes in a binary system are analyzed regarding the radiation of gravitational waves. Using the model based on the Regge-like laws, the Darwin instability effect in binary systems is discussed. New analytical formulas are derived for the period of orbital rotation and the relative distance between the components of a binary system. The impossibility of the appearance of a binary cosmic object from a single cosmic object is revealed.

Contributions of quasifission and fusion-fission in the Mg24 + Hf178 reaction at 145 MeV laboratory beam energy using the Boltzmann-Uehling-Uhlenbeck model

Background: Understanding the mechanism of the quasifission reaction is important, because it is an essential competitor to the fusion reaction leading to superheavy elements. However, it is a challenge to separate the quasifission and fusion-fission components.Purpose: This paper provides a dynamics description of the $^{24}\mathrm{Mg}+^{178}\mathrm{Hf}$ reaction at laboratory beam energy of 145 MeV, and studies contributions of quasifission and fusion-fission in the reaction.Method: The Boltzmann-Uehling-Uhlenbeck model is improved to study the heavy-ion collision at incident energy near the Coulomb barrier. A method is developed to determine the window of the dinuclear system during the evolution.Results: It is shown that the fusion occurs with a large percentage in the central collision, and the quasiinelastic scattering occurs mainly in the peripheral collision. The quasifission competes with the fusion in collisions with small impact parameters. It is found that the cross sections of quasifission decrease and those of fusion increase with increasing surface energy or incompressibility. The mass-angular correlation of the quasifission events shows the mass asymmetry. The fragments emitted at the front angle are targetlike fragments and those at the back angle are projectilelike fragments. Furthermore, the differential cross sections at the angles ${0}^{\ensuremath{\circ}}$ and ${180}^{\ensuremath{\circ}}$ are larger than that at ${90}^{\ensuremath{\circ}}$.Conclusions: By comparing the calculations of the mass distribution and mass-angular correlation to the data, it is deduced that the compound nucleus fission plays a main role and accounts for the characteristic of fragment observables in the $^{24}\mathrm{Mg}+^{178}\mathrm{Hf}$ reaction at laboratory beam energy of 145 MeV.

Influence of the Pauli exclusion principle on heavy-cluster radioactivity

The effects of the Pauli exclusion principle are investigated regarding the calculations of the nuclear cluster radioactivity using the double-folding formalism. To this purpose, the variation in the internal kinetic energy is considered at the overlapping regions between the densities of the two interacting nuclei as a modification term by employing the extended Thomas-Fermi approach. The effects of the Pauli exclusion principle on the internal energy of the dinuclear system and the standard deviation of the calculated half-lives from their corresponding experimental data are discussed. The results reveal that considering such corrections in calculating the double-folding potential leads to lower standard deviations, which are more consistent with experimental data than other semiempirical formulas.

Effect of deformation dependence and mirror nucleus corrections energy on multinucleon transfer reaction cross sections

Multinucleon transfer reactions are currently a powerful way to synthesize neutron-rich nuclei. To explore the effect of nucleus deformation and mirror nucleus shell correction energy in the nucleus mass model on the calculation of multinucleon transfer reaction cross sections in the dinuclear system (DNS) model, three macroscopic microscopic mass models are selected and the transfer reaction cross sections are calculated for 136Xe+208Pb and 64Ni+238U by improved DNS model+GEMINI++, respectively. The mirror nucleus shell correction energy does not improve the accuracy of the cross section of the transfer reaction. The introduction of a different dependence of the Coulomb and surface energy on the deformation can improve the calculation of the transfer reaction cross section when the projectile and target nuclei are deformed nuclei.

A combined experimental and theoretical study of covalent vs noncovalent dimer formation in vanadium(V) complexes with Schiff base ligands

This manuscript reports the synthesis, spectroscopic and X-ray characterization of three new vanadium(V) complexes, namely [VO2L1] (1), (μ-O)2[V(O)(L2)2]·2CH3CN (2) and (μ-O)2[V(O)(L3)2]·CH3CN (3) [HL1 (2-ethoxy-6-((quinolin-8-ylimino)methyl)phenol), HL2 (2-(1-(2-(methylamino)ethylimino)propyl)phenol) and HL3 (2-(1-(2-(ethylamino)ethylimino)propyl)phenol)]. Complex 1 is a mononuclear dioxovanadium(V) system containing a five coordinated metal center, whilst complexes 2 and 3 are centrosymmetric dinuclear systems with two [(L)V = O] moieties [(L2)- for 2 and (L3)- for 3], which are linked together through asymmetrically bridging oxygen atoms. DFT calculations have been used to rationalize the different behavior of complex 1, that is related to the lack of strong H-bond donors and strong ability to self-assemble via electrostatically enhanced π-stacking interactions. Moreover, the strength of π–π and CH–π interactions has been evaluated and the interactions have been characterized by several computational tools like MEP, QTAIM and NCI Plot.

Production cross sections of new neutron-rich isotopes with Z=92–106 in the multinucleon transfer reaction Au197+Th232

The multinucleon transfer reactions $^{197}\mathrm{Au}+^{232}\mathrm{Th}, ^{186}\mathrm{W}+^{232}\mathrm{Th}$, and $^{238}\mathrm{U}+^{232}\mathrm{Th}$ are investigated within the framework of dinuclear system (DNS) model with a decay model gemini$++$. The calculated isotopic production cross sections in the $^{136}\mathrm{Xe}+^{249}\mathrm{Cf}$ reaction at ${E}_{\mathrm{c}.\mathrm{m}.}=567\phantom{\rule{0.28em}{0ex}}\mathrm{MeV}$ can reproduce the experimental data well. Due to the subshell closures, the behavior of ``inverse'' quasifission process is found in the collisions of $^{186}\mathrm{W}+^{232}\mathrm{Th}$ and $^{197}\mathrm{Au}+^{232}\mathrm{Th}$. The reaction $^{197}\mathrm{Au}+^{232}\mathrm{Th}$ is more advantageous to produce neutron-rich isotopes with $Z=92--106$ than $^{186}\mathrm{W}+^{232}\mathrm{Th}$ and $^{238}\mathrm{U}+^{232}\mathrm{Th}$, because it has the lowest value of the potential energy that needed to overcome in the nucleon transfer process. Furthermore, the incident energy dependence of isotopic production cross sections in the reaction $^{197}\mathrm{Au}+^{232}\mathrm{Th}$ is studied. It is found that ${E}_{\mathrm{c}.\mathrm{m}.}=756.47$ MeV is more suitable for producing new isotopes with $Z=92--98$, while ${E}_{\mathrm{c}.\mathrm{m}.}=690.69$ MeV is the optimal incident energy for $Z=99--106$. The effect of incident energy on the interaction time is also investigated. The production cross sections of 88 unknown neutron-rich transuranium nuclei are predicted with the cross sections at the order of ${10}^{\ensuremath{-}6}$ to $10\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{b}$.

Examination of promising reactions with Am241 and Cm244 targets for the synthesis of new superheavy elements within the dinuclear system model with a dynamical potential energy surface

Two actinide isotopes, $^{241}$Am and $^{244}$Cm, produced and chemically purified by the HFIR/REDC complex at ORNL are candidates for target materials of heavy-ion fusion reaction experiments for the synthesis of new superheavy elements (SHEs) with $Z>118$. In the framework of the dinuclear system model with a dynamical potential energy surface (DNS-DyPES model), we systematically study the $^{48}$Ca-induced reactions that have been applied to synthesize SHEs with $Z=112$--118, as well as the hot-fusion reactions with $^{241}$Am and $^{244}$Cm as targets which are promising for synthesizing new SHEs with $Z=119$--122. Detailed results including the maximal evaporation residue cross section and the optimal incident energy for each reaction are presented and discussed.

Dynamics of charge equilibration and effects on producing neutron-rich isotopes around N=126 in 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 $N = 126$.

Direct Activation of the C(sp3)-NH2 Bond of Primary Aliphatic Alkylamines by a High-Valent CoIII,IV2(μ-O)2 Diamond Core Complex.

Aliphatic alkylamines are abundant feedstock and versatile building blocks for many organic transformations. While remarkable progress has been made to construct C-N bonds on aliphatic and aromatic carbon centers, the activation and functionalization of C(sp3)-NH2 bonds in primary alkylamines remain a challenging process. In the present work, we discovered an unprecedented method to directly activate the C(sp3)-NH2 bond of primary alkylamines by a high-valent dinuclear CoIII,IV2(μ-O)2 diamond core complex. This reaction results in the installation of other functional groups such as halides and alkenes onto the α-carbon center concomitant with the 2-e- oxidation of the nitrogen atom on the amino group to form NH2OH. These results shed light on future development enabling versatile functionalization of primary alkylamines based on the dinuclear cobalt system. Moreover, our work suggests that a related high-valent copper-oxo intermediate is likely generated in the ammonia monooxygenase catalytic cycle to affect the oxidation of NH3 to NH2OH.

Manifestation of Pairing Modes in Nuclear Collisions

We discuss the possible manifestation of pairing dynamics in nuclear collisions beyond the standard quasi-static treatment of pairing correlations. These involve solitonic excitations induced by pairing phase difference of colliding nuclei and pairing dynamic enhancement in the di-nuclear system formed by merging nuclei.

Tuning Nuclearity of Biradical-Ln Functional Compounds with Single-Molecule Magnet Behavior and Near-Infrared Luminescence

Utilizing an hexadentate nitronyl nitroxide biradical bisNITbpym, two series of biradical-4f clusters, namely [Tb2(hfac)6(bisNITbpym)2]·CHCl3 (1), [Dy2(hfac)6(bisNITbpym)2] (2), and [Ln4(hfac)12(bisNITbpym)2] (LnIII = YIII3, TbIII4 and YbIII5) (bisNITbpym = 2,2′-dipyridyl-5,5′-bis(1′-oxyl-3′-oxido-4′,4′,5′,5′-tetramethyl-4,5-hydro-1H-imidazol-2-yl); hfac = hexafluoroacetylacetonate), have been smoothly obtained via regulating the ratio of LnIII metal to biradical bisNITbpym. In compounds 1 and 2, the bisNITbpym ligand links two TbIII ions to yield a dinuclear pattern. Meanwhile, 3–5 exhibit an annular tetranuclear structure with biradical bisNITbpym, enwrapping and bridging four LnIII ions. Single-molecule magnet behavior of the Dy derivate is confirmed through frequency-dependent ac signals. Furthermore, this comparative exploration of dinuclear and tetranuclear systems indicates that spatial symmetries around LnIII ions have an important impact on magnetic dynamics. Near-infrared luminescence and slow magnetic relaxation have been observed in the YbIII derivative, which can act as a promising multifunctional probe in the aspect of fluoroimmuno assays. Our present work not only successfully acquires a multifunctional YbIII-based compound but also achieves the regulation of nuclearity and magnetic property of the nitronyl nitroxide biradical-LnIII system.

Quasifission barrier of heavy ion fusion reactions leading to the formation of the superheavy nucleus 120302

We study the quasifission barriers of different fusion reactions leading to synthesis of the superheavy element $Z=120$ using the dinuclear system approach. In particular, the influence of the projectile-target orientation and angular momentum on quasifission barriers has been investigated. The quasifission barrier height is observed to be maximum when the angle of orientation of projectile-target is about ${90}^{\ensuremath{\circ}}$ (tip-tip orientation). The role of entrance channel effects on quasifission barriers is investigated, and also suggested are suitable empirical formulas for the same. The striking results leading to larger quasifission barriers, whose cross sections are $>10$ fb, are also mentioned. As a result, the current research might be valuable in developing corrective techniques for future experimental attempts to synthesize superheavy nuclei with $Z=120$.

Interpretation of the Incomplete Fusion of Nucleus as Quasifission of Dinuclear System

Interpretation of the Incomplete Fusion of Nucleus as Quasifission of Dinuclear System

Influence of entrance channel on production cross sections of exotic actinides in multinucleon transfer reactions

Within the framework of the dinuclear system model, the influence of mass asymmetry and the isospin effect on the production of exotic actinides have been investigated systematically. The isotopic yields populate in multinucleon transfer reactions of Ca(48), Kr(86), Xe(136), and U(238) bombarding on Cm(248) are analyzed and compared to the available experimental data. Systematics on the production of unknown actinides from Ac to Lr via the available stable elements on the earth (from Ar to U) as projectiles-induced reactions with $^{232}$Th, $^{238}$U and $^{248}$Cm are investigated thoroughly. Potential energy surface and total kinetic energy distribution for the reaction system are calculated and can be used to predict the production cross-section trends. It is found that the heavier projectile leads to the wider isotopic chain distribution for the same target. The heavier target-based reactions prefer to produce plenty of exotic actinides through both mechanisms of deep-inelastic and quasi-fission reactions. Isospin relaxation plays a crucial role in the colliding process, resulting in actinide isotopic distribution tends to shift to the drip lines. Massive new actinides have been predicted at the level of nanobarn to millibarn. The optimal projectile-target combinations and beam energies were proposed for the forthcoming experiments.

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.

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.

Production of unknown neutron-rich isotopes with Z=99–102 in multinucleon transfer reactions near the Coulomb barrier

Multinucleon transfer reactions provide a possible access to the synthesis of new neutron-rich isotopes. Within the theoretical framework of a hybrid model combining the dinuclear system model and the GRAZING model together, the transfer reaction is investigated in $^{86}\mathrm{Kr}+^{248}\mathrm{Cm}$. In this work, it is found that the hybrid model can reproduce experimental transfer cross sections well. After the verification of the hybrid model, the transfer reactions $^{112,124,132}\mathrm{Sn}+^{249}\mathrm{Cf}$ are investigated by the influence of charge equilibration on the production cross sections of the exotic nuclei. The neutron-deficient projectile $^{112}\mathrm{Sn}$ shows advantages of producing neutron-deficient nuclei, while $^{124,132}\mathrm{Sn}$ are favorable to produce neutron-rich nuclei. In order to obtain available production cross sections of the unknown neutron-rich isotopes with $Z=99\text{\ensuremath{-}}102$, the dependence of cross sections on incident energy in the reaction $^{132}\mathrm{Sn}+^{249}\mathrm{Cf}$ is also investigated. It is found that the reaction $^{132}\mathrm{Sn}+^{249}\mathrm{Cf}$ at 510 MeV is a potential candidate to produce unknown neutron-rich isotopes of trans-target.

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.