Alpha-decay Half-lives Research Articles

Semi-empirical formula for alpha and cluster decay half-lives of superheavy nuclei

We have formulated a semi-empirical formula for alpha decay half-lives and cluster decay half-lives for superheavy nuclei of atomic number range [Formula: see text]. We have compared the logarithmic half-lives produced by the present formula with that of experiments and other formulae, such as universal decay law (UDL) [H. C. Manjunatha and K. N. Sridhar, Eur. Phys. J. A 53, 156 (2017)] and Horoi et al. [Horoi et al., J. Phys. G[Formula: see text] Nucl. Part. Phys. 30, 945 (2004)], Univ [D. Ni and Z. Ren, Phys. Rev. C 74, 014304 (2006)], Royer [G. Royer, J. Phys. G: Nucl. Part. Phys. 26, 1149 (2000)] and VSS [S. A. Gurvitz and G. Kalbermann, Phys. Rev. Lett. 59, 262 (1987)]. The constructed formula produces logarithmic half-lives for alpha and cluster decay (4He,9Be, [Formula: see text]B, [Formula: see text]C, [Formula: see text]N, [Formula: see text]O, [Formula: see text]F, [Formula: see text]Ne, [Formula: see text]Na, [Formula: see text]Mg, [Formula: see text]Al, [Formula: see text]Si, [Formula: see text]P, [Formula: see text]S, [Formula: see text]Cl, [Formula: see text]Ar, [Formula: see text]K and [Formula: see text]Ca) in superheavy nuclei of atomic number range [Formula: see text].

Alpha half-lives calculation of superheavy nuclei with Qα-value predictions based on the Bayesian neural network approach

In this work, we performed a systematic study of the α-decay process by employing the Bayesian neural network approach. The Qα-value prediction of the ten parameter Duflo-Zuker mass model has been improved from a root-mean-square deviation relative to the experimental data σ = 0.43 MeV to σ = 0.122 MeV. This correction brought to light some missing physical aspects in the DZ mass model, so as to identify some magic numbers not present in the original model. By using a phenomenological effective model to deal with alpha decay half-lives, we were able to obtain the half-life values throughout the superheavy elements region. As a main result, we found that the region of greatest stability against the alpha-decay process for superheavy elements is between 106 ≤ Z ≤ 110 and 180 ≤ N ≤ 184.

Uncertainties in the empirical formulae for alpha decay half-lives of heavy and superheavy nuclei

We have evaluated the alpha decay half-lives of heavy and superheavy nuclei where the experimental values are known using almost all semi-empirical formulae available in the literature. The deviation factor, root mean square value and Q -value sensitiveness of the formulae are evaluated for all the formulae available in the literature. From this detailed study it is found that the formula by Dong et al. (Nucl. Phys. A 832, 198 (2010)) and Wang et al. (J. Phys. G 42, 5 (2015)) has comparably smaller average deviation factor, less sensitive to Q -value, and the root mean square value is minimum. In addition to this we have also attempted a new simple formula for alpha decay half-lives.

Systematic study of alpha decay half-lives using new universal decay law

We have performed a systematic calculation on the alpha decay half-lives of heavy mass nuclei with 106 [Formula: see text] 118, within the universal decay law (UDL) and modified universal decay law (MUDL). The calculated half-life values are found to be in agreement with the experimental data. The standard deviations of the logarithm of half-lives are found to be the least for MUDL in all cases of even–even, even–odd, odd–even and odd–odd, so the MUDL formula is better than UDL formula for alpha decay studies. We have predicted half-lives of some superheavy nuclei (SHN) in the region [Formula: see text]–118 that are not yet experimentally detected. The decay energies are computed using three different mass models. We hope this study will help future measurements on alpha decay half-lives of SHN.

Competition between binary fission, ternary fission, cluster radioactivity and alpha decay of 281Ds

The competition between different decay modes such as binary fission, ternary fission, cluster and alpha decay modes finds an important role in the synthesis of superheavy nuclei. The nuclei 281Ds is the most stable among the isotopes of Ds. We have studied the different decay modes in superheavy nuclei 281Ds. It is observed that alpha decay half-lives are smaller compared to other modes. The alpha decay mode of 281Ds is observed with greater probability compared to binary fission.

Microscopic calculations of weak decays in superheavy nuclei

Half-lives of beta+ decay and electron capture are studied in some selected superheavy nuclei produced in hot fusion reactions, namely, 290Fl, 293Mc, 294Lv, and 295Ts. The nuclear structure is described microscopically from deformed self-consistent Skyrme Hartree-Fock mean-field calculations that include pairing correlations. The sensitivity of the half-lives to deformation and to the QEC energies, which are still not determined experimentally, are studied. The results are compared with phenomenological alpha-decay half-lives, showing that the latter decay mode is dominant in this mass region.

Study of the surface energy coefficient used in nuclear proximity potential of the $ \alpha$-nuclei systems from density-dependent nucleon-nucleon interactions

An attempt has been made to study systematically the nuclear surface tension coefficient, $ \gamma$ , of the proximity formalism by using the microscopic double-folding (DF) model with the realistic density-dependent (DD) nucleon-nucleon interaction for the ground-state-to-ground-state $ \alpha$ -decays of 235 parent nuclei with $ Z=61\mbox{--}99$ . In the calculations of DF model, the nucleon-nucleon (NN) interactions are formulated using the effective M3Y force of the CDM3Y6 based on the G -matrix elements of the Paris interaction. We present a new dependence of the surface energy coefficient $ \gamma$ on the asymmetry parameter $ A_s$ of the $ \alpha$ -nuclei systems by fitting all of the calculated values. Using the presently obtained formula of the coefficient $ \gamma$ in the proximity potential we calculate the theoretical values of the alpha-decay half-lives for different nuclei in the framework of the Wentzel-Kramers-Brillouin (WKB) approximation. Results of our calculations are compared to the values of the experimental data and proximity potential 1977. Good agreements are found. The quality of the proximity potential accompanied by the analytical formula of the surface energy coefficient is tested for fusion reactions between $ \alpha$ -particles and heavy nuclei 40 Ca, 48 Ti, 51V , 59Co , 63Cu , 93Nb , 154Sm and 162Dy The evaluated $ \alpha$ -capture cross sections agreed well with the corresponding experimental data. In the present study, the role of the proton and neutron magic numbers of daughter nuclei and also the Geiger-Nuttall plots of $ \log_{10} (T_{1/2})$versus$ Q_{\alpha}^{-1/2}$ for various isotopes of heavy parent nuclei have been studied.

Alpha decay half-lives calculation of even-even nuclei in the range 62 ≤ Z ≤ 118 using Gamow's theory

The Gamow's theory of alpha decay is used to systematically compute the alpha decay half-lives of even-even isotopes between the atomic numbers Z=62 and Z=118. The computation of the alpha decay half-lives of the parent nuclei are done by considering the experimental decay energies (Q) and the penetration frequency (n). These values are compared with experimentally available data and it is found to be in good agreement with the same. The explanation for the obtained patterns of variation of alpha decay half-lives as a function of neutron numbers for the whole region 62≤Z≤118 is given by the nuclear shell effect. This computational work proves that the Gamow's theory still holds good for the explanation of the half-lives of alpha emitters.

Alpha-decay half-lives of polonium isotopes in the mass range of 186–218

The [Formula: see text]-decay (AD) half-life (HL) of [Formula: see text]Po [Formula: see text] isotopes is studied systematically within the modified Coulomb and proximity potential model (MCPPM). The computed HLs are compared with the existing theoretical formulae including Royer, AKRE, Ren B and MRen B. This study considers the role of neutron shell closure [Formula: see text] on the AD HLs. The comparison with the experimental data indicates the acceptability of the results.

Prediction of Alpha Decay Half-Lives of Z = 118–121 Superheavy Nuclei with A ≤ 300 by Using the Double-Folding Potential

Abstract The alpha decay half-lives of Z = 118–121 superheavy nuclei with A ≤ 300 are calculated by using the density-dependent nuclear potential in the framework of the WKB method. The Paris and Ried M3Y nucleon-nucleon potentials are used in the calculation of the double-folding potential, which the Paris potential predicts to be the larger value of the half-lives. The obtained half-lives with Paris parameterisation are compared with those using three semi-empirical formulas, namely the improved Sahu formula, the universal decay law for alpha decay, and the formula for both alpha decay and cluster decay. The predicted half-lives with double-folding lie in between the improved Sahu and universal decay law formulas for both alpha and cluster decay. However, it is closer to the universal decay law formula and obeys its trend in all the studied superheavy nuclei.

Alpha particle preformation factor of spherical nuclei for 67 ≤Z ≤91

In this paper, alpha decay half-lives of spherical nuclei in the range [Formula: see text] are studied by considering the Coulomb and proximity potential model (CPPM) and calculating the alpha particle preformation factor. Comparisons are made to existing data in the literature. The half-lives are compared to the experimental values and also with the existing theoretical models, the analytical formula of Royer (R) and also within the modified analytical formula of Royer (MR) and New Akrawy–Poenaru Formula (AKRE) by Akrawy and Poenaru and the semi-empirical model based on fission theory (SemFIS) of Poenaru et al., the Universal Decay Law (UDL) of Qi et al., the Scaling Law of Brown (SLB), the Scaling Law of Horoi et al. (SLH). Compared with the experimental alpha half-lives, it can be found that the half-lives obtained using our formalism is in good agreement with the experimental data.

Alpha and cluster decay of some deformed heavy and superheavy nuclei

The alpha decay half-lives of some deformed superheavy nuclei and cluster decay half-lives of some deformed heavy nuclei were calculated in framework of WKB semiclassical method and by including Bohr–Sommerfeld quantization condition. Deformed double-folding nuclear and Coulomb potentials, and centrifugal potential have been considered for effective potential. Two forms of deformed surface diffuseness were used for calculations of alpha decay half-lives. In most of cases the calculated alpha decay half-lives with proposed deformed surface diffuseness were in better agreement with experiment in comparison with constant one. By using available experimental data, the cluster preformation probabilities were determined. Predicted cluster decay half-lives with inclusion of two different cluster preformation probability formulas were compared with those values of two empirical formulas. It was revealed the significant role of preformation probability in the cluster decay half-life calculations.

Studies on the synthesis superheavy element Z = 120

We have identified the probable isotopes for superheavy element Z=120 by comparing the alpha decay half-lives with that of spontaneous fission. The nuclei 290–304120 were found to have long half-lives and hence could be sufficient to detect them if synthesized in a laboratory. We have also studied the most possible projectile–target combination to synthesis those nuclei. The selected projectile–target system that can yield maximum production cross section is Ti+Cf.

Woods-Saxon-Gaussian potential and alpha-cluster structures of alpha + closed shell nuclei**Supported by the National Natural Science Foundation of China (11535004, 11761161001, 11375086, 11120101005, 11175085, 11235001), the National Key R&D Program of China (2018YFA0404403, 2016YFE0129300) and the Science and Technology Development Fund of Macau (008/2017/AFJ)

The Woods-Saxon-Gaussian (WSG) potential is proposed as a new phenomenological potential to systematically describe the level scheme, electromagnetic transitions, and alpha-decay half-lives of the 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 M3Y double-folding potential at the surface region and makes corrections to the inner part of the cluster-core potential. It was also determined that the WSG potential, with nearly identical parameters to that of 212Po (except for a rescaled radius), could also be used to describe alpha-cluster structures in 20Ne=16O+α and 44Ti=40Ca+α. In all three 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 in literature. The Gaussian form factor centered at the nuclear surface might also help to improve our understanding of the alpha-cluster formation, which occurs in the same general region.

Nuclear surface energy coefficients in cluster decay

The influence of different nuclear surface energy coefficients of the proximity potential in cluster decay of heavy, unstable radioactive nuclei is studied using a fission model by incorporating the preformation probability as the penetration probability of the overlapping region. An expression for preformation probability is fitted for preformation values, for which best matching is noted between calculated and experimental half-lives and is used in further calculations of cluster decay of superheavy elements. Half-lives for heavy cluster emission such as Ar, Ca, Ti, Cr, Fe, Co, Ni, Zn, Ga, Ge and Se, from superheavy nuclei with mass number in the range $ 252 \leq A \leq 294$ are predicted using the fitted expression for preformation probability. Predicted half-lives of heavy particle decay of superheavy nuclei compare well with the other prediction for a few clusters. Alpha decay being the predominant decay mode of heavy and superheavy nuclei, half-lives of heavy and superheavy nuclei are also calculated. Calculated half-lives of alpha decay for superheavy nuclei better reproduce the experimental values.

Comparative study of the alpha decay of Hg isotopes using different forms of nuclear potentials

The alpha decay half-lives of Hg isotopes within the range A = 171 – 212 have been studied using 25 different versions of nuclear potentials to select the suitable form of nuclear potential for alpha decay studies. The computed standard deviations suggested that the apt potential is BW 91 with a deviation 0.133. The next low deviation is shown by Proximity 1966, Proximity 1984, and Proximity 2003-I, II with deviations less than 0.2. Concerning other potentials, the fact we observed is that almost all the potentials possess a standard deviation less than one. The universal curve studied for alpha decay is observed to show straight line behavior irrespective of the nuclear potential used. Since the predicted alpha half-lives match well the experimental values, the half-lives of certain new Hg alpha emitters have been predicted by the present method. La période radioactive alpha des isotopes du mercure de nombre de masse A compris entre 171 et 212 a été évaluée à partir de 25 modèles différents de potentiel nucléaire adapté à la radioactivité alpha. Le calcul des écarts types suggère que le potentiel pertinent est BW 91, avec un écart de 0,133. La deuxième place revient à Proximity 1966, suivi de Proximity 1984 et de Proximity 2003-I, II, avec des écarts types inférieurs à 0,2. Les autres potentiels ont presque tous un écart type inférieur à 1. La courbe universelle caractéristique du rayonnement alpha est une droite, quel que soit le potentiel utilisé. Comme les périodes calculées sont en bon accord avec les valeurs expérimentales, on a calculé aussi, par la même méthode, les périodes de quelques émetteurs alpha nouveaux.

Alpha and cluster decay half-lives in Tungsten isotopes: A microscopic analysis

Alpha and cluster decay half-lives of Tungsten (W) isotopes in the range between 2p drip line and beta stability line are studied. The sensitivity of different Skyrme parametrizations in predicting the alpha decay and probable cluster decay modes from W isotopes have been analysed. The half-lives are calculated using Universal Decay Law (UDL). Predicted half-lives are compared with Effective Liquid Drop Model (ELDM) and also with available experimental values. The use of harmonic oscillator (HO) and transformed harmonic oscillator (THO) basis do not produce much differences in the results. The study also revealed the role of neutron shell closure in cluster decay process.

Unearthing radial independence for prediction of alpha-decay half-lives

Nuclear radial distance is a prerequisite for generating any alpha-decay half-life formula by taking a suitable effective potential. We study the emission process of alpha particles from an isolated quasi-bound state generated by an effective potential to a scattering state. The effective potential is expressed in terms of Frahn form of potential which is exactly solvable and an analytical expression for half-life is obtained in terms of Coulomb function, wave function and the potential. We then derive a closed-form expression for the decay half-life in terms of the parameters of the potential, Q-value of the system, mass and proton numbers of the nuclei valid for alpha-decay as well as proton-decay. From the nature of variations of half-life as a function of radial distance, we trace the radial independence region where decay time is almost constant. Finally, by overviewing our results and picking that particular radial distance, we predict the half-lives of a series of nuclei by using the closed-form expression. We also predict the half-lives of isotopes of nuclei with [Formula: see text] and 120.

Half-lives of α -decaying nuclei in the medium-mass region within the transfer matrix method

The alpha-decay half-lives of even-even nuclei from Sm to Th are systematically studied based on the transfer matrix method. For the nuclear potential, a type of cosh-parametrized form is applied t ...

Role of constant value of surface diffuseness in alpha decay half-lives of superheavy nuclei

By using WKB method and considering deformed Woods–Saxon nuclear potential, deformed Coulomb potential, and centrifugal potential, the alpha decay half-lives of 68 superheavy alpha emitters have been calculated. The effect of the constant value of surface diffuseness parameter in the range of 0.1 [Formula: see text]a [Formula: see text] 0.9 (fm) on the potential barrier, tunneling probability, assault frequency, and alpha decay half-lives has been investigated. Significant differences were observed for alpha decay half-lives and decay quantities in this range of surface diffuseness. Good agreement between calculated half-lives with fitted surface diffuseness parameter a = 0.54 (fm) and experiment was observed.