Decay Half-lives Research Articles

An improved simple model for α decay half-lives*

Abstract In this paper, using the α particle preformation probabilities from Xu et al. [Xu and Ren, Nucl. Phys. A 760, 303 (2005)], which were extracted by fitting experimental half-lives of α decay, based on a phenomenological harmonic oscillator potential model (HOPM) [Bayrak, J Phys G 47, 025102 (2020)], refitting 178 α decay half-lives of even-even nuclei obtained from the latest nuclear property table NUBASE2020, we obtain the only one adjustable parameter MeV in the HOPM, i.e., the depth of nuclear potential. The corresponding root-mean-square (rms) deviation is . Furthermore, to consider the contribution of centrifugal potential to unfavored α decay half-lives, adding a new term (d and l are the adjustable parameter and orbital angular momentum carried away by emitted α particle) to the logarithmic form of favored α decay half-lives under the HOPM framework, we propose an improved simple model (ISM) for calculating favored and unfavored α decay half-lives. Fitting the experimental half-lives of 205 unfavored α decay, we obtain . The ISM is used to calculate the unfavored α decay half-lives of 128 odd-A and 77 odd-odd nuclei. The results improve by 54.2% and 53.6%, respectively, compared with HOPM. In addition, we extend the ISM to predict the α decay half-lives of 144 nuclei with , and 120. For comparison, the improved model with eight parameters (DUR) proposed by Deng et al. [Deng, Phys. Rev. C 101, 034307 (2020)] and the modified universal decay law (MUDL) proposed by Soylu et al. [Soylu, Nucl. Phys. A 1013, 122221 (2021)] are also used. The predictions of these models and/or formulas are generally consistent with each other.

Theoretical investigation of heavy cluster decay from Z=118 and 120 isotopes: A search for an empirical formula in superheavy region

Various decay modes in superheavy nuclei have been of significant interest among which cluster radioactivity has recently gained sizable attention. The α-decay being a predominant decay mode in the superheavy region, the accurate determination of cluster decay half-lives is also crucial in this region as it has tremendous potential to be explored as one of the major decay channels. The usability of the Royer analytical formula [Nuclear Physics A 683 (2001) 182], which is based on the asymmetric fission model, has been investigated for the cluster and α-decay in superheavy region, by comparing it with several other (semi)empirical/analytical formulas. After fitting the formula on around 100 cluster-decay data and around 423 α-decay data, the refitted Royer formula (RRF) is found to be very robust which is able to estimate the cluster decay and α-decay half-lives with good accuracy. In fact, a comparison of the half-lives of both the decay modes using the same formula points towards a substantial chance of heavy cluster (Kr and Sr) decay from various isotopes of Z=118 and 120. Hence, the formula proposed in this study works fairly well for the estimation of cluster decay half-lives in superheavy regions where most empirical formulas fail to match with the half-lives from the various established theories.

Decay Characteristics of Neutron Excess Potassium Nuclei

In neutron star mergers, neutron excess nuclei and the r-process are important factors governing the production of heavy nuclear systems. A single-particle model evaluation of potassium nuclei suggests that the heaviest Z = 19 nucleus will have mass 69 with filling of the 1g9/2 neutron shell. A = 55 – 69 potassium isotopes have limited experimental half-life data, but the model predicts beta decay half-lives in the range of 0.315 – 9.23 ms. Based on previous calculations for Z = 9 - 18, 20, 26, and 30 systems and comparisons to the 55K – 59K, 61K, and 63K calculations, summarized in the Japanese Nuclear Data Compilation, the single-particle model results likely overestimate the half-lives of A = 55 – 69 neutron excess potassium nuclei.

Prediction on the alpha decay half-lives of 223−243Am isotopes

Prediction on the alpha decay half-lives of 223−243Am isotopes

Correlation between the shape coexistence and stability in Mo and Ru isotopes

In a rapidly changing shape phase region, the presence of shape coexistence and its possible impact on the decay modes and half-lives, has been explored in astrophysically interesting Mo and Ru isotopes, in an extensive study within the microscopic theoretical framework using Nilsson Strutinsky Method and Relativistic Mean Field Model. The isotopic chains of Mo and Ru exhibit rapid shape phase transitions, triaxial γ softness, shape instability along with many coexisting states mostly with oblate and triaxial shapes. Proton and neutron separation energies have been calculated and compared with the available data. Results obtained from both the formalisms are in good agreement with each other as well as the available experimental data. Our computed β-decay half-lives and separation energy for nuclei exhibiting shape coexistence were examined for the decay mode from second minima state of the parent nuclei to the ground or excited state of the daughter nuclei. The second minima state of the coexisting shapes in Mo and Ru isotopes, were seen to impact the structural properties, β-decay half-lives, separation energy and hence the stability of the nuclei.

First Study of the PIKACHU Project: Development and Evaluation of High-Purity Gd3Ga3Al2O12:Ce Crystals for 160Gd Double Beta Decay Search

Abstract Uncovering neutrinoless double beta decay (0ν2β) is crucial for confirming neutrinos’ Majorana characteristics. The decay rate of 0νββ is theoretically uncertain, influenced by nuclear matrix elements that vary across nuclides. To reduce this uncertainty, precise measurement of the half-life of neutrino-emitting double beta decay (2ν2β) in different nuclides is essential. We have launched the PIKACHU (Pure Inorganic scintillator experiment in KAmioka for CHallenging Underground sciences) project to fabricate high-purity Ce-doped Gd3Ga3Al2O12 (GAGG) single crystals and use them to study the double beta decay of 160Gd. Predictions from two theoretical models on nuclear matrix element calculations for 2ν2β in 160Gd show a significant discrepancy in estimated half-lives, differing by approximately an order of magnitude. If the lower half-life estimation holds true, detecting 2ν2β in 160Gd could be achievable with a sensitivity enhancement slightly more than an order of magnitude compared to prior investigations using Ce-doped Gd2SiO5 (GSO) crystal. We have successfully developed GAGG crystals with purity levels surpassing previous standards through refined purification and selection of raw materials. Our experiments with these crystals indicate the feasibility of reaching sensitivities exceeding those of earlier studies. This paper discusses the ongoing development and scintillator performance evaluation of High-purity GAGG crystals, along with the anticipated future prospects of the PIKACHU experiment.

Alpha Decay Half-lives of Heavy and Superheavy Nuclei within a Deformed Double Folding Model

Alpha Decay Half-lives of Heavy and Superheavy Nuclei within a Deformed Double Folding Model

A Systematic study on the alpha decay of superheavy nuclei using empirical diffuseness parameter in the coulomb and proximity potential model

Recent studies of Dehghani et al [Mod. Phys. Lett. A 33 14 1850080 (2018)] and Abdul-latif et al [Phys. Rev. C 100, 024601 (2019)] revealed the importance of the diffuseness parameter in the calculation of alpha decay half-lives from superheavy elements using proximity potentials. In the present paper, predictions of the empirical formula for the diffuseness parameter proposed by Abdul-latif et al is analyzed in view of the diffuseness parameter calculated by Dehghani et al using WKB method and considering deformed Woods–Saxon nuclear potential, deformed Coulomb potential, and centrifugal potential; and related theoretical aspects. From the conclusions, we propose three new empirical formulae for the diffuseness parameter. Using the diffuseness parameter calculated from the proposed empirical formula in the Coulomb and Proximity Potential Model (CPPM), the alpha decay half-life of 68 superheavy nuclei is calculated and compared with the experimental values. The inclusion of the diffuseness parameter in proximity potential improved the predictive power of the CPPM considerably.

An empirical formula for the half-lives of one- and two-proton radioactivity

We have proposed an empirical formula for one- and two-proton decays, including the angular momentum term. While investigating the first term in the Viola–Seaborg formula, we found a linear relationship between the logarithmic half-life and the expression [Formula: see text] for each angular momentum state. Furthermore, we obtained a linear relationship between the slope and intercept as functions of the angular momentum (l). Using these relations, we proposed a generalized empirical formula for the half-lives of one- and two-proton radioactivity for all angular momentum states. We analyzed the accuracy of the formula predictions by computing the standard deviation between the predicted and experimental decay half-lives. For the decay of one proton, the standard deviation of the proposed formula is 0.389, while that of the generalized formula is 0.400. These values represent the lowest standard deviations compared to previous models and the empirical formula. In the case of two-proton decay, the standard deviation for the current formula is 1.31, and the generalized formula also exhibits a lower standard deviation of 1.32. This lowest standard deviation value indicates that the proposed formula is suitable for reproducing the experimental half-life. We extended the half-life predictions to another 207 nuclei for one-proton decay and 42 nuclei for two-proton decay cases, which are energetically possible. The estimated half-lives for both one- and two-proton decays agree well with other theoretical predictions.

α-particle preformation factors in heavy and superheavy nuclei* *Supported in part by the National Natural Science Foundation of China (12175100, 11975132), the Construct Program of the Key Discipline in Hunan Province, the Research Foundation of Education Bureau of Hunan Province, China (21B0402, 18A237, 22A0305), the Natural Science Foundation of Hunan Province, China (2018JJ2321), the Innovation Group of Nuclear and Particle

In this study, α-particle preformation factors in heavy and superheavy nuclei from 220Th to 294Og are investigated. By combing experimental α decay energies and half-lives, the α-particle preformation factors are extracted from the ratios between theoretical α decay half-lives calculated using the Two-Potential Approach (TPA) and experimental data. We find that the α-particle preformation factors exhibit a noticeable odd-even staggering behavior, and unpaired nucleons inhibit α-particle preformation. Moreover, we find that both the α decay energy and mass number of parent nucleus exhibit considerable regularity with the extracted experimental α-particle preformation factors. After considering the major physical factors, we propose a local phenomenological formula with only five valid parameters for α-particle preformation factors . This analytic expression has a clear physical meaning as well as good precision. As an application, this analytic formula is extended to estimate the α-particle preformation factors and further predict the α decay half-lives for unknown even-even nuclei with Z = 118 and 120.

Activated corrosion product contamination assessments of DEMO WCLL breeding blanket primary heat transport system

In water-cooled fusion reactors, the assessment of the primary system contamination is essential for waste management, machine availability, occupational radiation exposure, and radiological hazard determination. The primary cooling water is not only directly activated by the intense neutron field but is a contamination vector for a significant variety of gamma emitters with short to long decay half-lives. Corrosion products can be activated in those regions under neutron flux of the primary circuit and then released in the cooling water.In the EU-DEMO fusion power plant equipped with the Water-Cooled Lithium Lead Breeding Blanket (WCLL-BB) concept, the primary coolant undergoes intense neutron fields in the first wall and the breeding zone regions of the blanket. Activated Corrosion Products (ACPs) are then formed, released into the water, transported in the cooling loop and finally deposited onto the ex -vessel surfaces of the Primary Heat Transport System (PHTS), where working personnel are susceptible to being radiologically exposed.This work addresses the complete assessment of ACPs in the WCLL-BB PHTS of EU-DEMO. The simultaneous and multi-physical processes behind the ACP formation are tackled using the OSCAR-Fusion code, a comprehensive tool developed by the CEA (France) to assess contamination in fusion nuclear reactors. The whole system is modelled with zero-dimensional nodes with assigned geometrical, thermal-hydraulics, material and chemical parameters. Activation reaction rates integrated over the whole spectrum and calculated with MCNP are given to those regions exposed to the neutron flux. Results are provided in terms of mass and activity inventories of ACPs as deposit and inner oxide layers of components (pipes, heat exchangers, pumps...), ions in solution, particles in suspension, and filters and resins trapping.Mobilizable inventories such as ions, particles and deposits are important source terms in accidental scenario evolutions, while the whole activity inventory constitutes the main long-term gamma emitting source for dose rate maps determination in the tokamak building rooms housing the main PHTS equipment.

Identification of a Durability Descriptor for Molecular Oxygen Reduction Reaction Catalysts.

The development of durable platinum-group-metal-free oxygen reduction reaction (ORR) catalysts is a key research direction for enabling the wide use of fuel cells. Here, we use a combination of experimental measurements and density functional theory calculations to study the activity and durability of seven iron-based metallophthalocyanine (MPc) ORR catalysts that differ only in the identity of the substituent groups on the MPcs. While the MPcs show similar ORR activity, their durabilities as measured by the current decay half-life differ greatly. We find that the energy difference between the hydrogenated intermediate structure and the final demetalated structure (ΔEdemetalation) of the MPcs is linearly related to the degradation reaction barrier energy. Comparison to the degradation data for the previously studied metallocorrole systems suggested that ΔEdemetalation also serves as a descriptor for the corrole systems and that the high availability of protons at the active site due to the COOH group of the o-corrole decreases the durability.

An empirical formula of nuclear <i>β</i>-decay half-lives

Nuclear <i>β</i>-decay half-lives play an important role not only in nuclear physics, but also in astrophysics. The <i>β</i>-decay half-lives of many nuclei involved in the astrophysical rapid neutron-capture (r -process) still cannot be measured experimentally, so the theoretical predictions of nuclear <i>β</i>-decay half-lives are inevitable for r-process studies. Theoretical models for studying the nuclear <i>β</i>-decay half-lives include the empirical formula, the gross theory, the quasiparticle random phase approximation (QRPA), and the shell model. Compared with other theoretical models of <i>β</i>-decay half-lives, the empirical formula has high computational efficiency, and its prediction accuracy can be improved by introducing more and more physical information. In this work, an empirical formula without free parameters is proposed to calculate the nuclear <i>β</i>-decay half-lives based on the Fermi theory of <i>β</i> decay. By including the pairing effect, the shell effect, and the isospin dependence, the newly proposed empirical formula significantly improves the accuracy of predicting the nuclear <i>β</i>-decay half-life. For the nuclei with half-lives less than 1 second, the root-mean-square deviation of the common logarithms of the nuclear <i>β</i>-decay half-life predicted by the new empirical formula from the experimental data decreases to 0.220, which is improved by about 54% compared with that by the empirical formula without free parameters, even better than those by other existing empirical formulas and microscopic QRPA approaches. In the unknown region, the nuclear <i>β</i>-decay half-lives predicted by the new empirical formula are generally shorter than those predicted by the microscopic models in the light nuclear region, while those predicted by the new empirical formula in the heavy nuclear region are generally in agreement with those predicted by the microscopic models. The half-lives of neutron-rich nuclei on the nuclear chart are then predicted by the new empirical formula, providing nuclear <i>β</i>-decay half-life inputs for the r-process simulations.

Experimental and theoretical multichannel study of direct nuclear reactions: A tool to provide data driven information on neutrino-less double-beta decay

The search for neutrino-less double beta decay has attracted much interest in the last years due to the extraordinary consequences that could derive from its observation. In the view to provide experimental information on the nuclear matrix elements involved in the expression of neutrino-less double beta decay half-life, the NUMEN project is measuring cross-sections of double charge exchange and other quasi-elastic nuclear reactions using the MAGNEX magnetic spectrometer. In particular, the newly proposed multichannel approach, applied both to the experimental and theoretical analysis, will be discussed.

The competition between α-decay and spontaneous fission for even–even isotopes of superheavy nuclei in the range 106≤Z≤124

The [Formula: see text]-decay and spontaneous fission (SF) half-lives for even–even isotopes of superheavy nuclei in the range [Formula: see text] are predicted using nuclear double-folding and Coulomb potentials. The [Formula: see text]-decay half-lives are computed based on WKB approximation for tunneling probability through potential barrier. The half-lives of SF have also been calculated using a semi-empirical relation constructed by Santhosh et al. [Nucl. Phys. A 832, 220 (2009)]. Our calculated half-lives of cold SF and [Formula: see text]-decay are compared with the available experimental data. This comparison indicates that our obtained half-lives are in good agreement with the available experimental data. The competition between [Formula: see text]-decay and SF is also analyzed in detail and the decay modes are predicted for the unknown cases. Variation of [Formula: see text]-decay and SF half-lives with mass number of the parent isotopes for each nucleus revealed the major role played with shell effect.

Study on the decay of Z = 127 – 132 superheavy nuclei via emission of 1-n and 2-n halo nuclei

The barrier penetrability, decay constant and decay half-life of 1-n halo nuclei 11Be, 15,17,19C, 22N, 23O, 24,26F, 29,31Ne, 34,37Na, 35,37Mg, and 55Ca; and 2-n halo nuclei 22C, 27,29F, 34Ne, 36Na, and 46P from Z = 127 – 132 parents were calculated within the framework of the Coulomb and proximity potential model by calculating the Q-values using the finite-range droplet model. A comparison between the decay half-lives is made by considering the halo candidates as a normal cluster and as a deformed structure with a rms radius. Neutron shell closure at 190, 196, 198, 200, 204, and 208 are identified from the plot of decay half-lives versus the neutron number of daughter nuclei (NP). The calculation of alpha decay half-life and spontaneous decay half-life showed that the majority of the parent nuclei survive spontaneous fission and decay through alpha emission. The Geiger-Nuttall plots of log10T1/2 versus Q-1/2 and universal plots of log10T1/2 versus -lnP for the emission of all 1-n and 2-n halo nuclei from the parents considered here are linear and show the validity of Geiger - Nuttall law in the case of decay of halo nuclei from superheavy elements.

Heavy particle radioactivity of superheavy nuclei.

We investigated different decay modes such as heavy particle radioactivity (HPR), spontaneous fission (SF), alpha decay and beta-decay in superheavy (SH) region 104≤Z≤126. In HPR, different emissions from Zmin=28 to maximum heavy particle (HP) emission up to Zmax=Z-82 were considered. In the evaluation of Q-values, mass excess Weizsäcker-Skyrme 4+radial basis function (WS4+RBF) values were taken into account. The half-lives of cluster decay determined using modified generalised liquid drop model (MGLDM) and Coulomb and proximity potential model (CPPM) were in close agreement with the experimental results. The MGLDM produce less deviation compared with CPPM. The role of asymmetry effect, relative neutron excess, pairing effect and Coulomb effect on half-lives were studied. A band of neutron numbers from 193 to 200 shows extra stability against HPR. The HPR of 86Kr, 94Zr, 91Y and 96Mo is observed in the superheavy elements Z=118, 122-124 and 126. The dominant decay mode identified is compared with SF, alpha and beta± decay, the majority of decay chains end with the lead nuclei, which is also evident in supernova and galaxy spectrum. This study could be useful in nuclear astrophysics.

Cluster properties of heavy nuclei predicted with the Barcelona-Catania-Paris-Madrid energy density functional

We study the cluster emission properties of 224\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{224}$$\\end{document}Ra and 238\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{238}$$\\end{document}Pu employing the Barcelona-Catania-Paris-Madrid (BCPM) energy density functional (EDF). Starting from two-dimensional potential energy surfaces, coexisting fission paths are identified. A fission valley located at large octupole deformations, corresponding to a highly-asymmetric mass distribution, is found in both nuclei. As the corresponding fragments are dominated by the presence of 208\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{208}$$\\end{document}Pb, we can relate this fission path to the emergence of cluster emission. Using the octupole moment as collective degree of freedom, we compute the cluster decay half-lives and study the impact of collective inertias, pairing strength and collective zero-point energy. The agreement with experimental data resembles the results obtained for spontaneous fission half-lives, indicating the capability of BCPM to consistently describe a large variety of fission phenomena, including cluster emission.

Random forest-based prediction of decay modes and half-lives of superheavy nuclei

Random forest-based prediction of decay modes and half-lives of superheavy nuclei

Impact of nuclear rotation corrections on alpha decay half-lives of superheavy nuclei within 98 ≤ Z ≤ 120

The influence of nuclear rotation on the decay half-lives of superheavy nuclei within the range 98≤Z≤120 is investigated using the axially deformed relativistic Hartree-Bogoliubov theory in the continuum (DRHBc) with the PC-PK1 parameter set. The deduced DRHBc decay energies (with and without the rotation effect) are compared with those calculated from the macroscopic-microscopic WS4 and the available experimental binding energies. Six semi-empirical formulae, such as the Viola-Seaborg formula (VSS), the modified Brown formula (mB1), the semi-empirical relationship based on fission theory (SemFIS2), the Royer formula (R), the Wang formula (Wang) and the modified YQZR formula (MYQZR) are employed to estimate the half-lives of α decay. Among these formulae, the half-live predictions of SemFIS2 are found to gradually deviate from the systematic trend beyond Nd=184, showing that the probability of undergoing spontaneous fission is less feasible beyond this point. A minimum is observed at Nd=184, reflecting its neutron shell closure for the mass region considered on the nuclear chart. The results further indicate that, for 98≤Z≤104, the predictions of all semi-empirical formulae are more closely matched to the available experimental data when the rotation effect is taken into account. However, we have demonstrated that the effect of nuclear rotation gradually reduces as the atomic nucleus becomes heavier.