Superheavy Elements Research Articles

From past to future in the science of super heavy elements

From past to future in the science of super heavy elements

The process for manufacturing superheavy elements gets an upgrade

The process for manufacturing superheavy elements gets an upgrade

Smooth trends in fermium charge radii and the impact of shell effects

The quantum-mechanical nuclear-shell structure determines the stability and limits of the existence of the heaviest nuclides with large proton numbers Z ≳ 100 (refs. 1–3). Shell effects also affect the sizes and shapes of atomic nuclei, as shown by laser spectroscopy studies in lighter nuclides4. However, experimental information on the charge radii and the nuclear moments of the heavy actinide elements, which link the heaviest naturally abundant nuclides with artificially produced superheavy elements, is sparse5. Here we present laser spectroscopy measurements along the fermium (Z = 100) isotopic chain and an extension of data in the nobelium isotopic chain (Z = 102) across a key region. Multiple production schemes and different advanced techniques were applied to determine the isotope shifts in atomic transitions, from which changes in the nuclear mean-square charge radii were extracted. A range of nuclear models based on energy density functionals reproduce well the observed smooth evolution of the nuclear size. Both the remarkable consistency of model prediction and the similarity of predictions for different isotopes suggest a transition to a regime in which shell effects have a diminished effect on the size compared with lighter nuclei.

Survival probability of Selenium-induced fusion reactions

In this paper, we investigated every potential scenario for selenium-induced heavy ion fusion reactions using astatine isotopes as the target. In this context, we examined [Formula: see text]Se projectiles and [Formula: see text]At targets having longer half-lives of comprising 21 fusion reactions for the synthesis of superheavy element [Formula: see text]. We assessed fusion cross-sections ([Formula: see text]), compound nucleus formation probability ([Formula: see text]), and survival probability ([Formula: see text]) for [Formula: see text]Se projectiles on [Formula: see text]At targets. The evaporation residue cross-sections ([Formula: see text]) is found to be larger for the fusion reaction of [Formula: see text]At of about 14.1[Formula: see text]fb. Hence, these striking results are useful in the synthesis of superheavy element [Formula: see text].

Toward the Discovery of New Elements: Production of Livermorium (Z=116) with ^{50}Ti.

The ^{244}Pu(^{50}Ti,xn)^{294-x}Lv reaction was investigated at Lawrence Berkeley National Laboratory's 88-Inch Cyclotron. The experiment was aimed at the production of a superheavy element with Z≥114 by irradiating an actinide target with a beam heavier than ^{48}Ca. Produced Lv ions were separated from the unwanted beam and nuclear reaction products using the Berkeley Gas-filled Separator and implanted into a newly commissioned focal-plane detector system. Two decay chains were observed and assigned to the decay of ^{290}Lv. The production cross section was measured to be σ_{prod}=0.44(_{-0.28}^{+0.58}) pb at a center-of-target center-of-mass energy of 220(3)MeV. This represents the first published measurement of the production of a superheavy element near the "island of stability," with a beam of ^{50}Ti and is an essential precursor in the pursuit of searching for new elements beyond Z=118.

Bayesian uncertainty quantification for synthesizing superheavy elements

To improve the theoretical prediction power for synthesizing superheavy elements beyond Og, a Bayesian uncertainty quantification method is employed to evaluate the uncertainty of the calculated evaporation residue cross sections (ERCS) for the first time. The key parameters of the dinuclear system model (DNS-sysu), such as the diffusion parameter a, the damping factor Ed, and the level-density parameter ratio af/an are systematically constrained by the Bayesian analysis of recent ERCS data. One intriguing behaviour is shown that the optimal incident energies (OIE) corresponding to the largest ERCS weakly depend on the fission process. We also find that these parameters are strongly correlated and the uncertainty propagation considering the parameters independently is not reasonable. The 2σ confidence level of posterior distributions for a=0.586−0.002+0.002 fm, Ed=25.65−3.41+3.43 MeV, and af/an=1.081−0.021+0.021 are obtained. Furthermore, the confidence levels of the ERCS and OIE for synthesizing Z = 119 via the reactions Cr54+243Am, Ti50+249Bk, and V51+248Cm are predicted. This work sets the stage for future analyses to explore the OIE and reaction systems for the synthesis of superheavy elements.

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.

Manifestation of relativistic effects in the chemical properties of nihonium and moscovium revealed by gas chromatography studies.

Chemical reactivity of the superheavy elements nihonium (Nh, element 113) and moscovium (Mc, element 115) has been studied by the gas-solid chromatography method using a new combined chromatography and detection setup. The Mc isotope, 288Mc, was produced in the nuclear fusion reaction of 48Ca ions with 243Am targets at the GSI Helmholtzzentrum Darmstadt, Germany. After isolating 288Mc ions in the gas-filled separator TASCA, adsorption of 288Mc and its decay product 284Nh on silicon oxide and gold surfaces was investigated. As a result of this work, the values of the adsorption enthalpy of Nh and Mc on the silicon oxide surface were determined for the first time, kJ/mol and kJ/mol (68% c.i.). The obtained -ΔH ads values are in good agreement with results of advanced relativistic calculations. Both elements, Nh and Mc, were shown to interact more weakly with the silicon oxide surface than their lighter homologues Tl and Bi, respectively. However, Nh and Mc turned out to be more reactive than the neighbouring closed-shell and quasi-closed-shell elements copernicium (Cn, element 112) and flerovium (Fl, element 114), respectively. The established trend is explained by the influence of strong relativistic effects on the valence atomic orbitals of these elements.

Coulomb interaction dependence of optimal energy to synthesize superheavy elements

The production of superheavy elements beyond Z = 118 remains unattained through both cold and hot fusion techniques, primarily due to inadequate fusion reaction optimization involving projectile–target combinations and energy. Past efforts employed various theories to optimize these combinations. In our current study, we have successfully identified optimal fusion energies for synthesizing superheavy elements, employing an advance statistical model and dinuclear system models. The establishment of optimal energy governing rule is achieved through a comprehensive examination of the Coulomb interaction parameter, enabling precise determination of the optimal energy for successful fusion reactions in synthesizing superheavy elements. The confidence level of predicting optimal energies using the present formula varies between 97% to 99%. The predicted optimal energy using the present formula for five fusion reactions such as 208Pb(50Ti,1n)257Rf, 208Pb(50Ti,2n)256Rf, 209Bi(50Ti,1n)258Db, 208Pb(58Fe,1n)265Hs, and 244Pu(48Ca,4n)288Fl were studied and are in good agreement with each other. Furthermore, we predicted the Optimal energies for fusion reactions leading to synthesize the superheavy element Z = 119 and 120. The presented empirical rule will certainly bring a revolution in the synthesis of superheavy elements.

A study on the synthesis of superheavy element Mc (Z = 115) using lead, bismuth and actinide targets

The evaporation residue cross sections in synthesizing isotopes of superheavy element Mc (Z = 115) by the hot fusion reactions 48Ca+241,243Am→289,291Mc, 45Sc+240,242,244Pu→285,287,289Mc, 50Ti+236,237Np→286,287Mc, 51V+238U→289Mc, 36S+253Es→289Mc, 46K+248Cm→294Mc, and by the cold fusion reactions 78As+208Pb→286Mc, 76Ge+209Bi→285Mc have been systematically investigated using the phenomenological model for production cross section. We have predicted the most effective projectile-target combinations for synthesizing Mc isotopes among these reactions. Our result shows that the 3n- channel cross section is larger for the reaction 48Ca+243Am→291Mc, and the 4n- channel cross section is larger for the reaction 46K+248Cm→294Mc. This study also examines the effect of the use of mass values and shell corrections by the Möller and Warsaw groups. Using our predicted combinations and the cross section values at a range of excitation energies, we hope these isotopes of Mc can be synthesized in near-future experiments.

Virtual cavity probe for the real-time identification of cavity burst-noise type in superconducting radio-frequency systems

Burst-noise events are primary trip sources at the China Accelerator Facility for superheavy Elements (CAFE2), characterized by a rapid burst noise in the cavity pick-up signal categorizable into three distinct types: flashover, electronic quench (E-quench), and partial E-quench. Herein, we design an algorithm identifying the burst-noise event types in real time to realize a real-time discrimination of the three types of burst-noise events. This algorithm is based on a virtual cavity probe constructed with the forward and reflected signals of the cavity and integrated into a field-programmable gate array (FPGA). Moreover, we introduce an innovative method for calibrating the transmission delay in channels. This FPGA-based low-level radio-frequency algorithm identifies the burst-noise event type in real time. Its effectiveness has been validated in the CAFE2 facility, offering valuable data support for future advancements in machine learning-based fault classification and dark-current characterization.

The Chemical Bond at the Bottom of the Periodic Table: The Case of the Heavy Astatine and the Super-Heavy Tennessine.

In this work, we study the chemical bond in molecules containing heavy and super-heavy elements according to the current state-of-the-art bonding models. An Energy Decomposition Analysis in combination with Natural Orbital for Chemical Valence (EDA-NOCV) within the relativistic four-component Dirac-Kohn-Sham (DKS) framework is employed, which allows to successfully include the spin-orbit coupling (SOC) effects on the chemical bond description. Simple halogen-bonded adducts ClX⋯L (X=At, Ts; L=NH3, Br-, H2O, CO) of astatine and tennessine have been selected to assess a trend on descending along a group, while modulating the ClX⋯L bond features through the different electronic nature of the ligand L. Interesting effects caused by SOC have been revealed: i) a huge increase of the ClTs dipole moment (which is almost twice as that of ClAt), ii) a lowering of the ClX⋯L bonding energy arising from different contributions to the ClX…L interaction energy strongly depending on the nature of L, iii) a quenching of one of the π back-donation components to the bond. In the ClTs(CO) adduct, the back-donation from ClTs to CO becomes the most important component. The analysis of the electronic structure of the ClX dimers allows for a clear interpretation of the SOC effects in these systems.

Extraction Time Simulations of a Cryogenic Gas Stopping Cell Designed to Study the Properties of Superheavy Elements

Extraction Time Simulations of a Cryogenic Gas Stopping Cell Designed to Study the Properties of Superheavy Elements

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

Investigation on Xenon-Induced Fusion Reaction to Synthesize Superheavy Element (SHE) Z=119

Investigation on Xenon-Induced Fusion Reaction to Synthesize Superheavy Element (SHE) Z=119

Theoretical predictions of properties and adsorption behaviour of a superheavy element Ts and its lighter homolog At, and of their various gas-phase compounds, on hydroxylated quartz surfaces from periodic DFT calculations

Adsorption energies, E ads, of a superheavy element Ts and its lighter homolog At, as well as of their various oxides, hydrides, and (oxy)hydroxides on hydroxylated quartz surfaces are calculated using a periodic density functional theory implemented in the AMS BAND software. It was shown that elemental At and Ts should be the most volatile over the quartz surfaces out of all the considered species, with E ads of the order of van der Waals bond energies, ∼25 kJ/mol. Hydride and hydroxide of At and Ts should be slightly less volatile than the elements with ∼20 kJ/mol larger E ads values. Oxides and oxyhydroxides of these elements should be the least volatile. All the compounds of Ts should be less volatile than the respective At ones. The differences in the E ads values between the Ts species should also be larger than those between the related At compounds, so that one should be able to differentiate between them more easily.

An extended Monte Carlo simulation code for modeling gas chromatography experiments with superheavy elements and their homologs

Monte Carlo simulations are commonly used to model the behavior of chemical species of the heaviest elements and their homologs in gas chromatography experiments. In this paper, we present an extension of the fundamental Monte Carlo simulation proposed by Zvara in 1985. While preserving the core functionality, our code features two enhancements: first, it allows simulating experiments in which a primary radioisotope decays into a daughter isotope belonging to a different element, hence exhibiting different chemical properties. Second, it allows modeling scenarios where conversion of an initial chemical species to a different one can occur at temperatures high enough to overcome an activation barrier, facilitating simulations of related physisorption and chemisorption processes. This Monte Carlo code is applicable to open tubular and rectangular chromatography columns.

70Zn-induced fusion reactions for synthesis of superheavy element Z=120

In this work, we delved into the intriguing realm of nuclear physics by investigating fusion reactions initiated by [Formula: see text]Zn projectiles colliding with various stable isotopes of thorium nuclei, including [Formula: see text]Th. Our primary objective was the synthesis of the superheavy element [Formula: see text]. To achieve this, we employed an advanced statistical model to evaluate the evaporation residue cross-sections. Remarkably, we observed that the fusion reaction between [Formula: see text]Zn and [Formula: see text]Th exhibited the highest evaporation residue cross-sections, reaching a peak value. Furthermore, the 3n channel within this fusion reaction yielded substantially larger evaporation cross-sections, with a notable value of 0.89 picobarns. The predicted cross-sections fall within the measurable range, making them highly valuable for experimental endeavors aimed at synthesizing the superheavy element [Formula: see text]. This research not only contributes to our understanding of nuclear reactions but also holds promise for expanding our knowledge of the heaviest elements in the periodic table, potentially opening new frontiers in nuclear science.

Assessing the impact of nuclear mass models on the prediction of synthesis cross sections for superheavy elements

Assessing the impact of nuclear mass models on the prediction of synthesis cross sections for superheavy elements

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.