Investigation of decay modes of superheavy nuclei

A detailed investigation of different decay modes,namely alpha decay,beta decay,cluster decay including heavy particle emission(Z_(c)>28),and spontaneous fission,was carried out,leading to the identification of new cluster and beta-plus emitters in superheavy nucle with 104≤Z≤126.For the first time,we identified around20 beta-plus emitters in superheavy nuclei.Heavy-particle radioactivity was observed in superheavy elements of atomic number in the range 116≤Z≤126.^(292-293)Og were identified as ^(86)Kr emitters,and ^(298)122 and ^(300)122 were identified as ^(94)Zr emitters,whereas heavy-particle radioactivity from ^(91)Y was also observed in ^(299)123.Furthermore,the nuclei ^(300)124 and ^(306)126 exhibit ^(96)Mo radioactivity.The reported regions of beta-plus and heavyparticle radioactivity for superheavy nuclei are stronger than those for alpha decay.The identified decay modes for superheavy nuclei are presented in a chart.This study is intended to serve as a reference for identifying possible decay modes in the superheavy region.

Optimization Method to Determine Gross Alpha-Beta in Water Samples Using Liquid Scintillation Counter

Liquid scintillation counting (LSC) is an adequate nuclear technique to determine radioactivity levels, as verified by this study for the determination of the gross alpha and beta activities of aqueous samples because of its simplicity and low associated cost comparison with other techniques. This paper discusses a new approach to the monitoring of gross alpha and gross beta activities in water. The method consists of using pulse decay discrimination (PDD) liquid scintillation counting LSC of 2 ml of the sample after conditioning with 12 ml of AB-Ultima Gold LSC cocktail, and PDD 139 condition. Different factors that affected on the counting efficiency were studied such as quench reaction, volume of sample, and type of vial. The gross alpha and gross beta particle activity measurement using 40K and 243Am with different activities concentration for efficiency determination. The calculated detection limits were 0.07 Bq/l and 0.12 Bq/l for gross alpha and gross beta respectively for 500 min measurements of samples produced by concentration of one liter of water.

Comparison of Mathematical Equations Applicable to Tolerance of Total Body Irradiation in Humans and Decay of Isotopes, Uranium and Thorium: Differences and Similarity

A clear and exact quantitative relationship between dose of total body irradiation and mortality in humans is still not known because of lack of human data that would enable us to determine LD50 for humans in total body irradiation. Analysis of human data has been primarily from radiation accidents, radiotherapy and the atomic bomb victims. The author published the general mathematical equations of LD50 constructed on the basis of data presented by Cerveny, MacVittie and Young, employing the probacent formula model. In this study, the author compared the equations of tolerance of total body irradiation and decay of isotopes, uranium and thorium. Differences and similarity in these equations of the two groups are presented. The significance of similarity is specially described.

Effects of a Periodic Decay Rate on the Statistics of Radioactive Decay: New Methods to Search for Violations of the Law of Radioactive Change

It is a long-held tenet of nuclear physics, from the early work of Rutherford and Soddy up to present times that the disintegration of each species of radioactive nuclide occurs randomly at a constant rate unaffected by interactions with the external environment. During the past 15 years or so, reports have been published of some 10 or more unstable nuclides with non-exponential, periodic decay rates claimed to be of geophysical, astrophysical, or cosmological origin. Deviations from standard exponential decay are weak, and the claims are controversial. This paper examines the effects of a periodic decay rate on the statistical distributions of 1) nuclear activity measurements and 2) nuclear lifetime measurements. It is demonstrated that the modifications to these distributions are approximately 100 times more sensitive to non-standard radioactive decay than measurements of the decay curve, power spectrum, or autocorrelation function for corresponding system parameters.

Problem of Nuclear Decay by Proton Emission in Fully Quantum Consideration: Calculations of Penetrability and Role of Boundary Conditions

We develop a new fully quantum method for determination of widths for nuclear decay by proton emission where multiple internal reflections of wave packet describing tunneling process inside proton-nucleus radial barrier are taken into account. Exact solutions for amplitudes of wave function, penetrability T and reflection R (estimated for the first time for decay problem) are found for n -step barrier (at arbitrary n) which approximates the realistic barrier. In contrast to semiclassical approach and two-potential approach, we establish by this method essential dependence of the penetrability on the starting point Rform in the internal well where proton starts to move outside (for example, for Ta the penetrability is changed up to 200 times;accuracy is T+R-1|-15 ). We impose a new condition: in the beginning of the proton decay the proton starts to move outside from minimum of the well. Such a condition provides minimal calculated half-life and gives stable basis for predictions. However, the half-lives calculated by such an approach turn out to be a little closer to experimental data in comparison with the semiclassical half-lives. Estimated influence of the external barrier region is up to 1.5 times for changed penetrability.

An angle-dependent potential and alpha-decay half-lives of deformed nuclei for 67≤Z≤91

The half-lives of deformed nuclei are reported for 67≤Z≤91. We consider an angle-dependent potential which yields multiple approximations. The results are in better agreement with the experimental data when the multiple approximation is solely considered for the daughter nuclei.

Alpha decay energies and half-lives for possibly synthesized superheavy elements

We investigate the ground state properties of some superheavy nuclei, which may be synthesized in future experiments. Special emphases are placed on the alpha decay energies and half-lives. The alpha decay energies and half-lives from different theoretical models are compared and discussed comprehensively. Through these calculations and comparisons, the optimal superheavy elements to be synthesized in future experiments are proposed theoretically.

Alpha decay of heavy and super heavy nuclei with a generalized electrostatic potential

Half-lives ofαdecay for Z≥84 nuclei are calculated based on the WKB theory applied for a phenomenological potential barrier composed of a centrifugal contribution and a screened electrostatic interaction represented by a Hulthen potential.For favored decays,the model has a single adjustable parameter associated with the screening of the electrostatic potential.The description of half lives for unfavored decays requires an additional hindrance term.A good agreement with experimental data is obtained in all considered cases.The evolution of the screening parameter for each nucleus revealed its dependence on shell filling.The model is also used for theoretical predictions on a few nuclei with uncertain or incomplete decay information.

Half-life of bismuth isotopes predicted by the Coulomb and proximity potential model; a proposition for the spherical nuclei

We know that the ground state energy, half-life, spin and parity of the heavy nuclei can be determined via the study of alpha decay. Bearing this in mind, we have calculated the penetration probability in the barrier, the decay constant and thereby the half-lives of 21 isotopes of Bi by using the proximity potential model. The comparison with the existing data is motivating.

Theoretical approaches to alpha decay half-lives of super-heavy nuclei

We consider the systematics of α-decay half-lives of super-heavy nuclei versus the decay energy and the total α-kinetic energy. We calculate the half-lives using the experimental Qα values. The computed half-lives are compared with the experimental data and with existing empirical estimates and are found to be in good agreement. Also, we obtain α-preformation factors from the ratio between theoretical and experimental results for some super- heavy nuclei and evaluate the standard deviation. The results indicate the acceptability of the approach.

Alpha decay half-lives of heavy nuclei within a generalized liquid drop model

Theoretical α-decay half-lives of the heaviest nuclei are calculated using the experimental Qα value. The barriers in the quasi-molecular shape path is determined within a Generalized Liquid Drop Model (GLDM) and the WKB approximation is used. The results are compared with calculations using the DensityDependent M3Y (DDM3Y) effective interaction and the Viola-Seaborg-Sobiczewski (VSS) formulae. The calculations provide consistent estimates for the half-lives of the α decay chains of these superheavy elements. The experimental data stand between the GLDM calculations and VSS ones in the most time.

Alpha-particle decays from excited states in ^(24)Mg

Using a cluster model based on the Woods-Saxon potential, alpha-particle decays from excited states in 24Mg have been system atically investigated. Calculations can in general reproduce experimental data, noticing the fact that the preformation factor P of alpha particle in alpha-decaying nuclei is of order from 100 to 10?2. This can be the evidence for the α+20Ne structure in 24Mg. Meanwhile, the results also show the existence of other configurations, such as 16O+2α. Since the calculated decay widths are very sensitive to the angular momentum carried by the outgoing cluster (α particle), our results could serve as a guide to experimental spin assignments.

Predicting the Binding Energies of the 1s Nuclides with High Precision, Based on Baryons which Are Yang-Mills Magnetic Monopoles

In an earlier paper, the author employed the thesis that baryons are Yang-Mills magnetic monopoles and that proton and neutron binding energies are determined based on their up and down current quark masses to predict a relationship among the electron and up and down quark masses within experimental errors and to obtain a very accurate relationship for nuclear binding energies generally and for the binding of 56Fe in particular. The free proton and neutron were understood to each contain intrinsic binding energies which confine their quarks, wherein some or most (never all) of this energy is released for binding when they are fused into composite nuclides. The purpose of this paper is to further advance this thesis by seeing whether it can explain the specific empirical binding energies of the light 1s nuclides, namely, 2H, 3H, 3He and 4He, with high precision. As the method to achieve this, we show how these 1s binding energies are in fact the components of inner and outer tensor products of Yang-Mills matrices which are implicit in the expressions for these intrinsic binding energies. The result is that the binding energies for the 4He, 3He and 3H nucleons are respectively, independently, explained to less than four parts in one million, four parts in 100,000, and seven parts in one million, all in AMU. Further, we are able to exactly relate the neutron minus proton mass difference to a function of the up and down current quark masses, which in turn enables us to explain the 2H binding energy most precisely of all, to just over 8 parts in ten million. These energies have never before been theoretically explained with such accuracy, which leads to the conclusion that the underlying thesis provides the strongest theoretical explanation to date of what baryons are, and of how protons and neutrons confine their quarks and bind together into composite nuclides. As is also reviewed in Section 9, these results may lay the foundation for more easily catalyzing nuclear fusion energy release.

Deviations from Beta Radioactivity Exponential Drop

At long-term count rate measurements of beta sources 3H, 56Mn, 32Si, 36Cl, 60Co, 137Cs, 90Sr-90Y and decay products of 226Ra the rhythmic changes with amplitude 0.1% 0.3% from average magnitude and period 1 year, and up to 0.01 % with period about one month are detected. Magnitude of diurnal oscillations did not exceed 0.003%. Analysis of measurements data for alpha radioactive sources 238Pu and 239Pu did not reveal any statistically reliable periodic patterns. Sporadic drops in the count rate were detected while registering the activity of 54Mn, 60Co and 90Sr-90Y sources. Bursts in the count rate were registered when scanning the celestial sphere by a reflecting telescope with 60Co or 40K radioactive sources at the focus point. Possible factors underlying these deviations in beta-radioactivity are discussed.

Study of various ground state decay mechanisms of Actinide nuclei

The special property of the actinide mass region is that nuclei belonging to this group are radioactive and undergo different ground state processes,such as alpha decay,cluster radioactivity(CR),heavy particle radioactivity(HPR),and spontaneous fission(SF).In this study,the probable radioactive decay modes of the heavy mass region(Z=89−102)are studied within the framework of the preformed cluster model(PCM).In the PCM,the radioactive decay modes are explored in terms of the preformation probability(P0)and penetration probability(P)at the turning point Ra,where the penetration of fragments is initiated[Ra=RT(touching state)+ΔR(neck length parameter)].First,the alpha decay half-lives are calculated for light and heavy nuclei,and Ra points are obtained by optimizing the neck length parameter.These Ra points are further employed to fix the Q-value dependent turning point(Ra(Q)).Then,using the(Ra(Q))relation,the decay half-lives are computed,and the calculated results are compared with the available theoretical and experimental data.The isotopical trend of P0 and P is studied with respect to the mass number of the parent and daughter nucleus,respectively.The CR and HPR channels are also explored,and a comparison of calculated data is conducted with the available literature.Comparative analysis of the fragmentation potential and preformation probability is carried out for alpha decay and SF.The mass distribution of the nuclei is studied as a function of fragment mass(A2)by considering the spherical and hot-compact deformation of the decaying fragments.Finally,the most probable fission fragments are identified using the fragmentation structure,and the corresponding fission fragment total kinetic energy of the identified fragments is calculated and compared with available data,wherever applicable.

Theoretical predictions on α-decay properties of some unknown neutrondeficient actinide nuclei using machine learning

Neutron-deficient actinide nuclei provide a valuable window to probe heavy nuclear systems with large proton-neutron ratios. In recent years, several new neutron-deficient Uranium and Neptunium isotopes have been observed using α-decay spectroscopy [Z. Y. Zhang et al., Phys. Rev. Lett. 122, 192503(2019);L. Ma et al., Phys. Rev.Lett. 125, 032502(2020);Z. Y. Zhang et al., Phys. Rev. Lett. 126, 152502(2021)]. In spite of these achievements,some neutron-deficient key nuclei in this mass region are still unknown in experiments. Machine learning algorithms have been applied successfully in different branches of modern physics. It is interesting to explore their applicability in α-decay studies. In this work, we propose a new model to predict the α-decay energies and half-lives within the framework based on a machine learning algorithm called the Gaussian process. We first calculate the α-decay properties of the new actinide nucleus 214 U. The theoretical results show good agreement with the latest experimental data, which demonstrates the reliability of our model. We further use the model to predict the α-decay properties of some unknown neutron-deficient actinide isotopes and compare the results with traditional models. The results may be useful for future synthesis and identification of these unknown isotopes.

α decay energies and half-lives from a macroscopic-microscopic model

α decay energies of 323 heavy nuclei with Z ≥82 are evaluated with a macroscopic-microscopic model. In this model, the macroscopic part is treated by the continuous medium model and the microscopic part consists of shell and pairing corrections based on the Nilsson potential. α decay half-lives are calculated bY Viola-Seaborg formula. The results of α decay energies and half-lives are compared with experimental values and satisfactory agreement is found. The recoiling effect of the daughter nucleus on α decay half-life is also discussed.

Woods-Saxon-Gaussian potential and alpha-cluster structures of alpha + closed shell nuclei

The Woods-Saxon-Gaussian （WSG） potential is proposed as a new phenomenological potential to sys- tematically describe the level scheme, electromagnetic transitions, and alpha-decay half-lives of tile alpha-cluster structures in various alpha ＋ closed shell nuclei. It modifies the original Woods Saxon （WS） potential with a shifted Gaussian factor centered at the nuclear surface. The free parameters in the WSG potential are determined by reproducing the correct level scheme of ^212Po=^208Pb＋α. It is found that the resulting WSG potential matches the NI3Y double-folding potential at tile surface region and makes corrections to the inner part of the cluster-core l）otential. It was also determined that the WSG potential, with nearly identical parameters to that of ^212Po （except for a rescale（l radius）, could also be used to describe alpha-cluster structures in ^20Ne=^16O＋α and ^44Ti = ^40Ca＋α. In all lhrec cases, the calculated values of the level schemes, electromagnetic transitions, and alpha-decay half-lives agree with the experimental data. which indicates that the WSG potential could indeed capture many important features of the alpha-cluster structures in alpha ＋ closed shell nuclei. This study is a useful complement to the existing cluster-core potentials ill literature. The Gaussian form factor centered at the nuclear surface might also help to improve our understailding of the alpha-cluster formation, which occurs in the same general region.

Search for decay modes of heavy and superheavy nuclei

Spontaneous fission(SF) with a new formula based on a liquid drop model is proposed and used in the calculation of the SF half-lives of heavy and superheavy nuclei(Z = 90–120). The predicted half-lives are in agreement with the experimental SF half-lives. The half-lives of decay(AD) for the same nuclei are obtained by using the Wentzel-Kramers-Brillouin(WKB) method together with Bohr-Sommerfeld(BS) quantization condition considering the isospin-dependent effects for the cosh potential. The decay modes and branching ratios of superheavy nuclei(Z =104-118) with experimental decay modes are obtained, and the modes are compared with the experimental ones and with the predictions found in the literature. Although some nuclei have predicted decay modes that are different from their experimental decay modes, decay modes same as the experimental ones are predicted for many nuclei. The SF and AD half-lives, branching ratios, and decay modes are obtained for superheavy nuclei(Z = 119–120) with unknown decay modes and compared with the predictions obtained in a previous study. The present results provide useful information for future experimental studies performed on both the AD and SF of superheavy nuclei.

β-delayed proton decays of ^(81)Zr and ^(85)Mo

β-delayed proton decays of Tz = 1/2 series nuclei 81Zr and 85Mo have been studied in detail by using p-γ coincidence measurement. The (3-delayed proton spectra populating the first excited states of the daughter nuclei have been obtained. Half-life of 81Zr has been measured to be 5.3 s ± 0.5 s and that of 85Mo 3.2 s ± 0.2 s. By using statistical model calculations and systematic analyses, spins and parities for the ground states of 81 Zr and 85 Mo have been tentatively assigned to be 3/2- and 1/2-, respectively. Mass excess of 81Zr is -58.3 MeV±0.2 MeV and that of 85Mo -59.1 MeV±0.4 MeV. Combining the measured half-lives with the calculated partial ones yields the branches of (3-delayed proton decay for 81Zr and 85Mo of (1.2 ± 0.2) × 10-3 and (1.4 ± 0.2) × 10-3, respectively.