Dinuclear System Research Articles

Production mechanism and prediction cross sections of unknown neutron-rich 263–265,267–269Lr isotopes in multinucleon transfer reactions based on the dinuclear system model

Within the framework of the dinuclear system model, the production cross sections for producing the new neutron-rich Lr isotopes in the multinucleon transfer reactions with 249Bk and 254Es targets were predicted. The results show that the 124Sn + 254Es reaction has the highest production cross sections, followed by the 130Te + 249Bk reaction. As far as the existing experimental techniques are concerned, 130Te + 249Bk is the most suitable choice. With experimental techniques developing in the future, 124Sn + 254Es is preferable when the thick 254Es target can be prepared. The optimal energy for producing the new neutron-rich Lr isotopes is 1.1 times the Coulomb barrier for both reaction systems, and both reactions produced 263–265,267–269Lr isotopes. The production mechanism of Lr isotopes has been investigated in the 130Te + 249Bk reaction. It is found that the production of Lr isotopes mainly originates from the contribution of quasifission. And the contribution of quasifission gradually decreases with the increase of the incident angular momentum. The final production cross sections for 263–265,267–269Lr in 130Te + 249Bk reaction at E c.m. = 1.10V C are 0.22 μb, 0.13 μb, 0.15 μb, 4.45 nb, 0.62 nb, and 0.03 nb, respectively

Production of unknown Fl isotopes in proton evaporation channels within the dinuclear system model

The production of Fl isotopes in proton evaporation channels is investigated systematically within the dinuclear system model. Because the proton evaporation is the easiest for Mc isotopes among the isotopes around $Z=114$, one can synthesize Fl isotopes in the proton evaporation channel. The calculated ER cross sections by the DNS model reproduce the experimental data very well. The dependence of the production cross sections on projectile isospin in capture, fusion, and survival processes in $^{32,34,36}\mathrm{S}+^{255}\mathrm{Es}$ reactions is studied. The capture cross sections and survival probability in the $^{36}\mathrm{S}+^{255}\mathrm{Es}$ reaction are the largest, while the fusion probability in the $^{32}\mathrm{S}+^{255}\mathrm{Es}$ reaction is the highest. The reaction $^{48}\mathrm{Ca}+^{244}\mathrm{Am}$ is a promising candidate to synthesize the unknown isotope $^{290}\mathrm{Fl}$ with the maximum ER cross section of 4.07 pb in the $p1n$ evaporation channel. Another new isotope $^{291}\mathrm{Fl}$ can be produced in the $^{54}\mathrm{Cr}+^{239}\mathrm{Pa}$ reaction and the production cross section is estimated to be 0.11 pb.

Single and multiple site Cu(II) catalysts for benzyl alcohol and catechol oxidation reactions

Cu(II) catalysts both in homogeneous and heterogeneous form were synthesized to bring the distinction between the single and multiple site catalysis. The single site mononuclear complexes with axial occupancy of Cl- and CH3COO- ligand and the acetate, imidazolate bridged dinuclear Cu(II) complexes were tested for selective oxidation of benzyl alcohol and catechol oxidation. The reactivity of the complexes was compared with the multiple site copper oxide (CuO) nanocatalyst derived from the metal complex precursor. The single site Cu(II) catalyst showed much superior activity in the selective oxidation of BA compared to the dinuclear and the CuO-nanocatalyst. The oxidation of catechol to o-benzoquinone was however found to be catalyzed more preferably by the di-nuclear systems. The high lability of Cl- and -OOCH3 groups in the mononuclear complexes allowed the incoming oxidant, substrate as well as the solvent (acetonitrile, CH3CN) molecules to interact with the active Cu-centre and thereby favoured the benzyl alcohol oxidation. Both the experimental and theoretical studies provided a conclusive idea about the reaction mechanism of benzyl alcohol and catechol oxidation. UV–vis, cyclic voltammetric study and density functional theory (DFT) calculations provided the strong evidence for the formation of Cu-CH3CN complex during benzyl alcohol oxidation. FTIR and Raman study substantiated by the theoretical calculations indicated for the formation of Cu- hydroperoxo species during the catalytic studies. The kinetics study revealed for the 1st order kinetic for the catechol oxidation and the DFT study predicted for the exothermic nature of the catechol oxidation process.

Improvement of evaporation residual cross sections for superheavy nuclei using a neural network method

Synthesizing heavier superheavy nuclei (Z>118) in the laboratory and probing the charge limit of atomic nuclei are difficult problems in the field of nuclear physics. Theoretically accurate calculations of the evaporation residual cross section (ERCS) play the key roles for synthesis of new superheavy nuclei. In this work, based on the neural network method, the evaporation residual cross sections of superheavy nuclei calculated by the dinuclear system model are improveded to make the theoretical results closer to the experimental values, which substantially increased the accuracy of the theoretical description. In particular, the results for the evaporation of 5 neutrons are greatly improved.

Theoretical study on the production of neutron-rich transuranium nuclei with radioactive beams in multinucleon transfer reactions

The production of neutron-rich transuranium nuclei with $Z=93--98$ in multinucleon transfer reactions induced by radioactive beams $^{92}\mathrm{Kr}, ^{132}\mathrm{Sn}$, and $^{144}\mathrm{Xe}$ with actinide target $^{238}\mathrm{U}$ is investigated within the dinuclear system model with decay code gemini$++$. The isotopic distributions for reactions $^{136}\mathrm{Xe}+^{248}\mathrm{Cm}$ and $^{136}\mathrm{Xe}+^{249}\mathrm{Cf}$ are calculated and compared with the available experimental data. Theoretical calculations can reproduce the experimental results well. Both the $N/Z$ ratio equilibration mechanism and driving potential dominate the transfer process of nucleons. Reaction $^{132}\mathrm{Sn}+^{238}\mathrm{U}$ is an optimal projectile-target combination to obtain large production cross sections of neutron-rich isotopes with $Z=93--98$. The corresponding optimal incident energy is also explored. The production cross sections of 41 unknown neutron-rich transuranium isotopes with cross sections greater than 1 nb are predicted. The reaction $^{132}\mathrm{Sn}+^{238}\mathrm{U}$ at ${E}_{\mathrm{c}.\mathrm{m}.}=521.3$ MeV shows huge advantages in producing neutron-rich transuranium nuclei with $Z=93--98$.

Possibilities of synthesizing new proton-rich nuclei with 40 ≤ Z ≤ 60 using multinucleon transfer reactions * *Supported by the ational Natural Science Foundation of China (12175064, U2167203). Hunan Provincial Education Department (Key project 20A290)

Multinucleon transfer reactions near the Coulomb barrier are investigated based on the improved dinuclear system (DNS) model, and the deexcitation process of primary fragments are described using the statistical model GEMINI++. The production cross sections of Ca+ Sn and Ni+ Te based on the DNS model+GEMINI++ are calculated and compared with experimental data. The calculated results reproduce experimental data. The cross sections of fusion-evaporation, fragmentation, and multinucleon transfer reactions in the region are also provided in this paper. The results show that in the region, fusion-evaporation and fragmentation reactions have good results in the relatively proton-rich region, but in the extreme proton-deficient region, the MNT reaction is still promising for synthesizing proton-rich nuclei.

Tetrazine Chelate Ligands Bridging Two [Ru(acac)2] Fragments: Mixed Valency and Radical Complex Formation

AbstractUsing bis(3‐methyl‐2‐pyridyl)‐1,2,4,5‐tetrazine 1, 3‐(2‐pyrimidyl)‐6‐methyl‐1,2,4,5‐tetrazine 2 and bis(2‐pyrimidyl)‐1,2,4,5‐tetrazine=bmtz as ligands, the complexes 3=[Ru(acac)2(1)], 4={[Ru(acac)2]2(1)], 5={[Ru(acac)2]2(bmtz)], and 6={[Ru(acac)2]2(2)] were prepared and identified by structure analysis of crystallized material. The one‐electron oxidized form 6(PF6) was also studied structurally, suggesting a Class II mixed‐valent situation. The neutral dinuclear systems exhibit two reversible oxidation processes with comproportionation constants 109.2<Kc<1014.1 and one reduction which were analyzed UV/vis/NIR and EPR spectroscopically. Oxidation produces largely metal‐based mixed‐valent cations with very weak intervalence absorptions in the near IR whereas the electron uptake occurs at the tetrazine acceptor.

Predictions for the synthesis of the Z=119 superheavy element

The optimal projectile-target combination and bombarding energy for the production of the new superheavy element (SHE) $Z=119$ are predicted within the framework of a dinuclear system (DNS) model, in which the evaporation residue cross section (ERCS) is the product of capture cross section, fusion probability, and survival probability. To this end, the effects of mass asymmetry and isospin effect of target nucleus on the ERCS are analyzed. It is found that the ERCS for the production of SHE $Z=119$ is relatively large with the $^{45}\mathrm{Sc}$ projectile, while the ERCS in most cases decreases slowly with increasing neutron number of the target nucleus. We hope these predictions will shed new light timely for the recent experiments on the synthesis of the $Z=119$ superheavy element.

Electronic structures, bonding aspects and spectroscopic parameters of homo/hetero valent bridged dinuclear transition metal complexes

Bridged dinuclear metal complexes have fascinated scientists worldwide, and remarkable success has been achieved to unravel the electronic structures, structure–function relationship, coordination environments, and fine mechanistic details of the enzymes owing to the repercussion of biomimetic studies carried out on dinuclear model systems. Molecular level study of these systems integrated with spectroscopic study helps in gaining deep insights about structural and electronic aspects of natural enzymatic systems. Considering the same, here first time we report DFT study on bridged non-heme metal complexes based on N-Et-HPTB ligand system containing homovalent (MIIMII); {[(MnII)2(O2CCH3)(N-Et-HPTB)]2+; Species I), [(FeII)2(O2CCH3)(N-Et-HPTB)]2+; Species II), [(CoII)2(O2CCH3)(N-Et-HPTB)]2+; Species III)} and heterovalent (MIIIMII): {[(MnIII)(MnII)(O2)(N-Et-HPTB)]2+; Species Ia) [(FeIII)(FeII)(O2)(N-Et-HPTB)]2+; Species IIa) and [(CoIII)(CoII)(O2)(N-Et-HPTB)]2+; Species IIIa)} dinuclear metal centres. Bridging oxygen bears a significant spin density which may prompt important chemical reactions involving activation of bonds like C-H/O-H/N-H etc. TD-DFT calculations for UV–Visible absorption have been carried out to further shed light on structural–functional and electronic structures of these dinuclear species. Studying these dinuclear species may be a good starting point for the study of active sites of the bimetallic centre of dinuclear enzymes and thus may serve as fascinating spectroscopic models. Further, FMO analysis, MEP mapping, and NBO calculations were employed to analyze bonding aspects predict theoretical reactivity behaviour and any kind of stabilizing interactions present in the reported species.

Radioactivity of Dysprosium

The effective liquid drop model (ELDM) is used to explore the one proton radioactivity of all possible Dysprosium isotopes, and the molecular phase of the di-nuclear system is used to investigate the possible barriers limiting one proton emission. The mass excess values are obtained from [Chin. Phys. C 45 (2021) 030003]. The WKB integral is used to evaluate the penetration probability. The half-lives of proton decay are compared to those of other decay modes. The decay chains of [Formula: see text]Dy are predicted. The detailed investigations of [Formula: see text]Dy show proton radioactivity when [Formula: see text]Tb is converted to [Formula: see text]Gd with the half-life of order of nanoseconds. Further, these identified proton emitters may find to be useful in the field of diagnosis and radiotherapy.

Potential energy surface and formation of superheavy nuclei with the Skyrme energy-density functional

With the Skyrme energy-density functional theory, the nucleus–nucleus potential is calculated and the potential energy surface is obtained with different effective forces for accurately estimating the formation cross sections of superheavy nuclei in massive fusion reactions. The width and height of the potential pocket are influenced by the Skyrme effective forces SkM, SkM*, SkP, SIII, Ska, and SLy4, which correspond to the different equations of state for the isospin symmetry nuclear matter. It is found that the nucleus–nucleus potential is associated with the collision orientation and Skyrme forces. A more repulsive nuclear potential is pronounced with increasing the incompressible modulus of nuclear matter, which hinders the formation of superheavy nuclei. The available data in the fusion-evaporation reaction of 48Ca+238U are nicely reproduced with the SkM* parameter by implementing the potential into the dinuclear system model.

How to approach the island of stability: Reactions using multinucleon transfer or radioactive neutron-rich beams?

The multinucleon transfer (MNT) process and radioactive beam induced fusion-evaporation (FE) reactions are the considered routines to explore the island of stability. We make the first direct comparison of the two approaches for producing neutron-rich superheavy nuclei, especially the predicted double magic isotope 298Fl. The radioactive beams 49−59Ca induced hot FE reactions with actinide targets and the MNT reaction 238U + 252Cf are investigated within the framework of the dinuclear system model. Based on the beam intensities proposed by Argonne Tandem Linac Accelerator System, we find that the MNT and FE processes are comparable for producing 298Fl. The influence of the shell structures uncertainties on the production cross section of 298Fl is evaluated. It is found that the shell structures weakly influence the production cross sections of 298Fl around the optimal incident energy, although, the double shell closures could strongly enhance the stability of 298Fl. We also quantitatively estimated the relative proportion of shell effects on cross sections in the transfer stage of the MNT reaction 238U + 252Cf. It is demonstrated that the shell effects on production cross section of 298Fl are mainly from de-excitation process. The general conclusion of this work is that the radioactive beam induced FE reactions show advantages for the excursion toward N=184 from current status.

Spontaneous fission hindrance in even-odd nuclei within a cluster approach

For even-odd isotopes of actinides and superheavy nuclei, spontaneous fission and $\ensuremath{\alpha}$-decay half-lives are calculated within the dinuclear system model and compared with the existing experimental data. All these processes are considered as the evolution of a nucleus in the charge (mass) asymmetry coordinate and in the relative distance between the centers of clusters formed. The important role of the spin dependence of total potential energy in the charge asymmetry coordinate is shown and the origin of the fission hindrance in even-odd nuclei is explained.

Rare isotope formation in complete fusion and multinucleon transfer reactions in collisions of Ca48+Cm248 near Coulomb barrier energies

Within the framework of the dinuclear system model, the reaction mechanisms for synthesizing target-like isotopes from Bk to compound nuclei Lv are thoroughly investigated in complete and incomplete fusion reaction of $^{48}$Ca +$^{248}$Cm around Coulomb barrier energies. Production cross-section of $^{292,293}$Lv as a function of excitation energy in fusion-evaporation reactions and target-like isotopic yields in multinucleon transfer reactions are evaluated, in which a statistical approach is used to describe the decay process of excited nuclei. The available experimental data can be reproduced well with the model reasonably. The products of all possible formed isotopes in the dynamical pre-equilibrium process for collision partners at incident energy $E_{\rm lab}$ = 5.5 MeV/nucleon are exported, systematically. It is found that the quasi-fission fragments are dominant in the yields. The optimal pathway from the target to compound nuclei shows up along the valley of potential surface energy. The effective impact parameter of two colliding partners leading to compound nuclei is selected from head-on collision to semi-central collision with $L$ = 52 $\rm \hbar$. The timescale boundary between complete fusion and multinucleon transfer reactions is about 5.7$\times 10^{-21}$ s with effective impact parameters. Synthesis cross-section of unknown neutron-rich actinides from Bk to Rf have been predicted around several nanobarns.

Production of new neutron-rich isotopes with 92≤Z≤100 in multinucleon transfer reactions

To explore the optimum conditions for producing new neutron-rich isotopes in the range $92\ensuremath{\le}Z\ensuremath{\le}100$ by multinucleon transfer reactions, $^{86}\mathrm{Kr}+^{248}\mathrm{Cm}, ^{129}\mathrm{Xe}+^{248}\mathrm{Cm}, ^{132}\mathrm{Xe}+^{248}\mathrm{Cm}, ^{136}\mathrm{Xe}+^{248}\mathrm{Cm}$ and $^{238}\mathrm{U}+^{248}\mathrm{Cm}$ systems with bombarding energies around their respective Coulomb barriers are investigated within an improved dinuclear system (DNS) model, combined with the statistical gemini$++$ model. The calculated production cross sections are in a good agreement with experimental data. It is found that, compared with projectiles $^{86}\mathrm{Kr}$ and $^{136}\mathrm{Xe}$, the projectile $^{238}\mathrm{U}$ can produce larger cross sections of neutron-rich nuclei of interest by bombarding the actinide target $^{248}\mathrm{Cm}$. Actinide projectile-target combination seems to be encouraging for the production of neutron-rich isotopes with $92\ensuremath{\le}Z\ensuremath{\le}100$.

Analysis of the fusion mechanism in the synthesis of superheavy element 119 via the Cr54+Am243 reaction

The combined dinuclear system (DNS) and statistical model implanted in KEWPIE2 have been used to study the prospects for the synthesis of a superheavy element (SHE) with $Z=119$ in the $^{54}$Cr+$^{243}$Am fusion reaction. The method of calculation has been verified by description of the evaporation residue cross sections measured for the $^{48}$Ca+$^{243}$Am reaction. The calculated results of the partial and total cross sections for the complete fusion, quasifission, fast fission and evaporation residues formation for both reactions are discussed.

Production of unknown neutron-rich transuranium isotopes 245–249Np, 248–251Pu, 248–254Am, and 252–254Cm in multinucleon transfer reactions

The production cross sections of unknown neutron-rich transuranium isotopes of elements Np, Pu, Am and Cm are investigated in multinucleon transfer (MNT) reactions based on the dinuclear system model with GEMINI code. The influence of the incident energy on the production of neutron-rich transuranium nuclei in actinide–actinide collisions is studied. The calculation results show that the final isotopic production cross sections are larger at 1.06–1.10 V cont than at other energies. Considering the high fissility of transuranium nuclides, 1.06 V cont is chosen as the optimal incident energy. The N/Z ratio equilibration mechanism in the nucleon transfer process is also studied in this work. The larger difference of N/Z ratio between projectile and target corresponds to larger neutron diffusion during the nucleon exchange process. The 238U beam with high N/Z ratio and neutron-rich actinide targets are good selections to produce neutron-rich transuranium nuclides. The production cross sections of unknown neutron-rich transuranium isotopes 245–249Np, 248–251Pu, 248–254Am, and 252–254Cm are predicted in 238U-induced actinide-based (249Bk, 249Cf, and 252Cf) MNT reactions. It is found that a large number of these unknown neutron-rich transuranium nuclei could be generated at the level of nb to μb in the reactions 238U + 249Bk and 238U + 252Cf. Our research indicates that the reaction 238U + 249Bk is a suitable projectile-target combination in the current experimental conditions and the reaction 238U + 252Cf could be a promising candidate to produce unknown neutron-rich transuranium nuclides in case that the 252Cf target were to be achieved in the future.

Chiral Dinuclear EuIII, TbIII, and YIII Complexes Supported by P‐Stereogenic Linear Tetraphosphine Tetraoxide

AbstractA P‐stereogenic linear tetraphosphine tetraoxide, (R,R)‐ or (S,S)‐dpmppm(=O)4, was synthesized to prepare C2 dinuclear M(hfa)3 complexes (M=Eu, Tb, Y) as the first example of lanthanide(III) complexes with P‐chiral multidentate phosphine oxides. The mononuclear M(hfa)3 complexes (M=Eu, Y) with a P‐chiral diphosphine dioxide, tpdpb(=O)2, were also prepared, and comparison of their photophysical properties for the EuIII complexes revealed that significant chiral induction from the P‐chiral centers arises on the achiral M(hfa)3 units through intramolecular π‐π stacking constraint in the dinuclear system.

Decay of dinuclear systems formed from dubnium

Decay of dinuclear systems formed from dubnium

Unified description of fusion and multinucleon transfer processes within the dinuclear system model

To compare fusion-evaporation (FE) and multinucleon transfer (MNT) approaches and make more reliable predictions for producing superheavy nuclei, the unified description of FE and MNT processes is performed in the reaction $^{48}\mathrm{Ca}+^{238}\mathrm{U}$ within the (DNS) model. We extend the fusion concept in the DNS model based on the deformation degree of freedom. Our calculations support the experimental result [Nishio et al., Phys. Rev. C 77, 064607 (2008)] that compact configuration enhances the fusion probability. The experimental production cross sections of isotopes in FE and MNT processes can be simultaneously reproduced. By comparing the production cross sections in the MNT reaction $^{238}\mathrm{U}+^{248}\mathrm{Cm}$ with the FE reactions $^{48}\mathrm{Ca}+^{238}\mathrm{U}$ and $^{54}\mathrm{Cr}+^{248}\mathrm{Cm}$, we find that the FE process shows great advantages of cross sections for producing Cn isotopes and is the only approach that could produce superheavy elements beyond oganesson.