Effects of shell correction on α decay properties

The shell correction effects on the α decay properties of heavy and superheavy nuclei have been studied in a macroscopic-microscopic manner. The macroscopic part is constructed from the generalized liquid drop model(GLDM), whereas the microscopic part, namely, the shell correction energy, brings about certain effects on the potential barriers and half-lives under a WKB approximation, which is emphasized in this work. The results show that the shell effects play a significant role in the estimation of the α decay half-lives within the actinide region.Predictions of the α decay half-lives are then generated for superheavy nuclei, which will provide useful information for future experiments.     

Interior electron shells in superheavy nuclei

The interior electron shells for superheavy nuclei (90≦Z≦250) have been investigated. Their binding energies are tabulated together with the vacuum polarization corrections for the various levels.     

The synthesis and properties of superheavy nuclei produced in the 48Ca+244Pu, 248Cm reactions

We present the results of the experiments aimed at producing hypothetical long-lived superheavy elements located near the spherical shell closures with Z>-114 and N>-172. For the synthesis of superheavy nuclei a combination of neutron-rich reaction partners, such as ²⁴⁴Pu and ²⁴⁸Cm targets and a ⁴⁸Ca projectile have been used. The sensitivity of the present experiment exceeded by more than two orders of magnitude previous attempts to synthesize superheavy nuclides in reactions of ⁴⁸Ca projectiles with actinide targets. We observed new decay sequences of genetically linked α-decays terminated by spontaneous fission. The decay properties of the synthesized nuclei are consistent with the consecutive α-decays originating from the parent nuclides ^288,289114, produced in the 3n and 4n-evaporation channels, and ²⁹²116 — in the 4n-evaporation channel with cross sections of about a picobarn. The present observations can be considered an experimental evidence of the existence of the “island of stability” of superheavy elements and are discussed in terms of modern theoretical approaches.     

A systematic study of superheavy nuclei for Z = 114 and beyond using the relativistic mean field approach

We have studied the structural properties of even-even, neutron deficient, Z = 114–126, superheavy nuclei in the mass region A ∼ 270–320, using an axially deformed relativistic mean field model. The calculations are performed with three parameter sets (NL1, TM1 and NL-SH), in order to see the dependence of the structural properties on the force used. The calculated ground state shapes are found to be parameter dependent. For some parameter sets, many of the nuclei are degenerate in their ground state configuration. Special attention is given to the investigation of the magic structures (spherical shell closures) in the superheavy region. We find that some known magic numbers are absent and new closed shells are predicted. Large shell gaps appear at Z = 80, 92, (114), 120 and 138, N = 138, (164), (172), 184, (198), (228) and 258, irrespective of the parameter sets used. The numbers in parenthesis are those which correspond to relatively smaller gaps. The existence of new magic numbers in the valley of superheavy elements is discussed. It is suggested that nuclei around Z = 114 and N = 164 ∼ 172 could be considered as candidates for the next search of superheavy nuclei. The existence of superheavy islands around Z = 120 and N = 172 or N = 184 double shell closure is also discussed.     

Binding energies of even-even superheavy nuclei

The structure of the even-even superheavy nuclei with the proton number Z=98–110 is studied using the self-consistent relativistic mean-field theory. The calculated binding energies are in good agreement with the available experimental ones. An upper limit and a lower limit on the binding energies are set by the calculations. This is useful for future calculations of properties of superheavy nuclei and for the experimental synthesis of superheavy nuclei. The energy surface of some relevant superheavy nuclei is also given and it confirms the correctness of the calculations.     

Shell structure and stability of nuclei with 270<A<500 and the possible existence of primordial superheavy nuclei

The self-consistent energy density method is applied to the study of the properties of superheavy nuclei with 270<A<500. The shell structure,α-decay energy andα-decay half-life are predicted for the heaviestβ-stable isotope of each even element. The characteristics of nuclear densities and single-particle potentials in the superheavy region are also examined, with a particular attention on the surface diffuseness. After an approximate calculation of their fission barrier heights, only a few heavy isotopes of elements 106 and 108 are predicted to have a small chance to be found in nature. Their possible formation by ther-process is discussed.     

The relative stability of superheavy elements

The relative stability of superheavy elements against beta-decay and spontaneous fission has been investigated. A simple criterion of beta-stability using the Fermi gas model has been developed, tested in the range of stable nuclei and extended to the superheavy region. Spontaneous fission half-lives have been calculated using the statistical model in the expected region of relative beta-stability for superheavy nuclei. Our results have been compared with previous calculations.     

超重核294118和291116及其α衰变链上各核素半衰期的研究

运用推广的液滴模型（GLDM）确定了超重核294118和291116及其α衰变链上各核素的衰变势垒, 采用量子力学中的WKB方法计算α衰变中的势垒穿透几率, 对该链上各原子核的α衰变半衰期进行了研究。 此外, 还利用Royer公式对该链上各原子核的α衰变半衰期进行了计算。 结果表明, GLDM 考虑亲和能与Royer公式给出的α衰变半衰期与超重核区的实验值符合很好, 验证了GLDM和Royer公式在超重核区的适用性,可以用来预测超重核的半衰期。 最后, 预言了Z=118 和116 同位素链上各核素的半衰期, 结果表明, 在Z=118和116中存在α衰变长寿命同位素, 这需要实验上的检验。The α decay potential barrier of the newly synthesized superheavy nuclei starting from 294118 and 291116 have been determined and their half lives have been studied with the Generalized Liquid Drop Model(GLDM) connected with WKB approximation and Royer’s formulae．The α decay half lives of the nuclei belonging to the superheavy nuclei starting from 294118 and 291116 have been calculated．The calculated results are in agreement with the experimental data, which show that the α decay half lives of superheavy nuclei with the GLDM and Royer’s formulae can be applied in the studying on superheavy nuclei successfully．Finally, the half lives of Z=118 and 116 isotopes have been predicted, and the results suggest there may be some long lived superheavy nuclei for α decay in those isotopes.     

Fission process of superheavy nuclei

The process of fusion-fission of superheavy nuclei with Z=102?122 formed in the reactions with ²²Ne, ²⁶Mg, ⁴⁸Ca, ⁵⁸Fe and ⁸⁶Kr ions at energies near and below the Coulomb barrier has been studied. The experiments were carried out at the U-400 accelerator of the Flerov Laboratory of Nuclear Reactions (JINR) using a time-of-flight spectrometer of fission fragments CORSET and a neutron multi-detector DEMON. As a result of the experiments, mass and energy distributions of fission fragments, fission and quasi-fission cross sections, multiplicities of neutrons and gamma rays and their dependence on the mechanism of formation and decay of compound superheavy systems have been studied.     

Synthesis of superheavy nuclei in 48Ca+244Pu interactions

This article reports the results of experiments aimed at producing hypothetical long-lived superheavy elements located near the spherical-shell closures with Z≥114 and N≥72. For the synthesis of superheavy nuclei, we used a combination of neutron-rich reaction partners, with a ²⁴⁴Pu target and a ⁴⁸Ca projectile. The sensitivity of the present experiment exceeded by more than two orders of magnitude previous attempts at synthesizing superheavy nuclides in reactions of ⁴⁸Ca projectiles with actinide targets. We observed new decay sequences of genetically linked alpha decays terminated by spontaneous fission. The high measured alpha-particle energies, together with the long decay times and spontaneous fission terminating the chains, offer evidence for the decay of nuclei with high atomic numbers. The decay properties of the synthesized nuclei are consistent with the consecutive alpha decays originating from the parent nuclides ^288,289114, produced in the 3n-and 4n-evaporation channels with cross sections of about a picobarn. The present observations can be considered experimental evidence for the existence of the “island of stability” of superheavy elements and are discussed in terms of modern theoretical approaches.     

Effect of properties of superheavy nuclei on their production and decay

Properties and stability of superheavy nuclei resulting from hot fusion are discussed. It is shown that the microscopic–macroscopic approach allows obtaining the closed proton shell at Z ≥ 120. Isotopic trends of K-isomeric states in superheavy nuclei are predicted. Evaporation residue cross sections in hot fusion reactions are calculated using the predicted properties of superheavy nuclei. Interruption of α decay chains by spontaneous fission is analyzed. Alpha decay chains through isomeric states are considered. Internal level densities in superheavy nuclei are microscopically calculated.     

Grand unification of effective gauge theories

An effective non-renormalizable SU(3)×SU(2)×U(1) invariant gauge theory results at ordinary energies when superheavy fields are integrated out from a grand unified theory based on a simple gauge group G. The solutions of the second-order renormalization-group equations for the gauge coupling constants of the effective theory are examined. General formulae for the superheavy vector boson mass and for sin²θ near M_W are given in this approach to grand unification. The superheavy vector boson mass is plotted against the QCD scale parameter Λ for a certain set of grand unified models. Corrections to the prediction when the set of models is enlarged are discussed, and illustrated with examples from G≡SU(5) and O(10).     

Search for superheavy elements in galactic cosmic rays

The charge distribution of approximately 6000 nuclei with charge numbers above 55 in galactic cosmic rays has been obtained in the OLIMPIYA project. Three superheavy nuclei with the charge numbers in the range 105 < Z < 130 have been detected. The regression analysis has provided a more accurate estimate of the charge number of one of these nuclei (119 _?6 ⁺¹⁰ with a probability of 95%). Such nuclei should form stability islands. Their detection in nature confirms theoretical predictions and justifies efforts for their synthesis under terrestrial conditions. The model calculations performed in this work possibly can explain the results of some experiments on the investigation of the charge composition of cosmic rays in which particles with charge numbers in the range 94 < Z < 100 were detected (they cannot enter into the composition of primary cosmic radiation because their lifetime is very short). The calculations indicate that events with Z > 92 are due to the fragmentation of heavier nuclei from the stability island, rather than to methodical inaccuracies or fault of instruments. Several such events have been revealed. Thus, the track method makes it possible to obtain the results very important for understanding of the physical picture of the world. The results obtained within the OLIMPIYA project show that the study of tracks of galactic cosmic rays in olivine crystals from meteorites opens new capabilities for the investigation of fluxes and spectra in cosmic rays in the region of heavy and superheavy nuclei.     

Pairing with a delta interaction in the energy density nuclear mass formula

The variations of the average pairing strength in the (N, Z) plane are studied with a δ-interaction in the frame of the self-consistent energy density formalism. It is found that the same δ-interaction with constant strength can be used for protons and neutrons in spherical nuclei near the stability line. This interaction is used to study the extrapolation of the average pairing strength to deformed nuclei, to the superheavy region and to the regions of the drip lines. The consequences of the results for the stability of superheavy nuclei and for magic numbers far from the stability region are examined.     

Nuclei in the terminal parts of the r-process path

Half-life calculations for various decay processes have been made for neutron-rich elements with $\text{Z ≧ 90}$ and with neutron numbers between the β-stability line and the neutron-drip line. The calculations are based on the modified oscillator model. The results, which are highly dependent on the size of the N = 184 neutron gap predicted by the model, appear not to permit the population of the superheavy region through the r-process, in contradiction to the results of a recent investigation by Schramm and Fowler.     

Detecting galactic cosmic ray transuranium nuclei in olivine crystals from meteorites

Results from the experimental search for and identification of tracks from the superheavy and transuranium nuclei of galactic cosmic rays in pallacite olivine crystals, conducted as part of project OLIMPIA [1], are presented. To date, 170 crystals from Marjalahti and Eagle Station pallacites have been processed and 6800 tracks corresponding to nuclei with charges Z > 55 have been found; 45 of these are from nuclei with charges of 88 < Z < 92 and three super-long ones were produced by nuclei with Z > 105. The charge of one of these nuclei is estimated in the first approximation as Z = 119(+10,?6). Our data confirm the hypothesis of islands of stability for natural trans-Fermi nuclei.     

A periodic table of free diatomic molecules—II predicted internuclear separations from curve-fitted data

Recent theory substantiates the stacking order of the areas in the recently proposed periodic table of the free diatomic molecules. The periodic table suggests curve-fitting algorithms for r_e which, after semi-empirical perturbations yield ground-state values for r_e which agree with literature values and with those from an alternate algorithm to from 5 to 8%. 800 predicted r_e extend to superheavy quasimolecules and to molecules with superheavy atoms, and many pertain to molecules of laser interest.     

A self-consistent mean-field study of Z = 120 nuclei and α-decay chains of 292,298,299,300,304120 isotopes

A self-consistent mean-field investigation is done to test the model accuracy, model dependence, and the dependence on different model parameters in the study of superheavy nuclei. This is done within the self-consistent mean-field models-the Skyrme-Hartree-Fock-Bogoliubov (HFB), and the Relativistic-Hartree-Bogoliubov (RHB) with density-dependent couplings. A systematic comparison is made with experimental data, as well as with the macro-microscopic Finite Range Droplet Model(FRDM). The bulk ground state properties and the microscopic structure of Z=120 superheavy nuclei are investigated. Further investigation is made of α-decay series for the five isotopes ^{292,298,299,300,304}120 of Z=120 nuclei. A spontaneous fission investigation is done to account the number of α-decay before spontaneous fission starts. The experimental data available for α-decay energies and half-lives are produced reasonably. The RHB model with NL3* parameter set, and with ImSahu and UNIV2 formula to calculate the α-decay half-lives is found to be the best suited for accurately predicting the ground state properties and the α-decay half-lives of the superheavy nuclei.     

Systematic study of decay properties of heaviest elements

Decay properties and stability of heaviest nuclei with Z ?? 132 are studied within the macro-microscopical approach for nuclear ground-state masses. We use phenomenological relations for the half-lives with respect to ??-decay, ??-decay and spontaneous fission. Our calculations demonstrate that the ??-stable isotopes ²⁹¹Cn and ²⁹³Cn with a half-life of about 100 years are the longest-living superheavy nuclei located on the first island of stability. We found the second island of stability of superheavy nuclei in the region of Z ?? 124 and N ?? 198. It is separated from the ??continent?? by the ??gulf?? of short-living nuclei with half-lives shorted than 1 ??s.     

Conversion processes in superheavy and giant atoms

Conversion of bound state electrons and internale ⁺,e ^?-pair creation in superheavy and giant atoms are investigated. We consider various nuclear transitions of multipolaritiesE0, EL andML (L≧1) in superheavy atoms with Z>109. We are concerned in particular with the pecularities of conversion processes in supercritical systems. Our theoretical studies are confronted with the prominent peak structures observed in positron spectra of very heavy collision systems.