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Register a new userRecent $alpha$ decay half-lives and analytic expression predictions including superheavy nuclei
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New recent experimental $alpha$ decay half-lives have been compared with the results obtained from previously proposed formulas depending only on the mass and charge numbers of the $alpha$ emitter and the Q$alpha$ value. For the heaviest nuclei they are also compared with calculations using the Density-Dependent M3Y (DDM3Y) effective interaction and the Viola-Seaborg-Sobiczewski (VSS) formulas. The correct agreement allows us to make predictions for the $alpha$ decay half-lives of other still unknown superheavy nuclei from these analytic formulas using the extrapolated Q$alpha$ of G. Audi, A. H. Wapstra, and C. Thibault [Nucl. Phys. A729, 337 (2003)].
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Theoretical decay half-lives of the heaviest odd-Z nuclei are calculated using the experimental Q value. The barriers in the quasimolecular shape path are determined within a Generalized Liquid Drop Model (GLDM) and the WKB approximation is used. The results are compared with calculations using the Density-Dependent M3Y (DDM3Y) effective interaction and the Viola-Seaborg-Sobiczewski (VSS) formulas. The calculations provide consistent estimates for the half-lives of the decay chains of these superheavy elements. The experimental data stand between the GLDM calculations and VSS ones in the most time. Predictions are provided for the decay half-lives of other superheavy nuclei within the GLDM and VSS approaches using the recent extrapolated Q of Audi, Wapstra, and Thibault [Nucl. Phys. A729, 337 (2003)], which may be used for future experimental assignment and identification.
In present work, we systematically study the $alpha$ decay half-lives of 170 even-even nuclei with $60 leqslant Z leqslant 118$ within the two-potential approach while the $alpha$ decay preformation factor $P_alpha$ is obtained by the cluster-formation model. The calculated results can well reproduce the experimental data. In addition, we extend this model to predict the $alpha$ decay half-lives of 64 even-even nuclei with $104 leqslant Z leqslant 128$ whose $alpha$ decay is energetically allowed or observed but not yet quantified. For comparing, the two famous models i.e. SemFIS proposed by D. Poenaru ${et al.}$ [href {https://doi.org/10.1209/0295-5075/77/62001}{Europhys. Lett. textbf{77} (2007) 62001}] and UDL proposed by C. Qi ${et al.}$ [href {https://doi.org/10.1103/PhysRevLett.103.072501}{Phys. Rev. Lett. textbf{103} (2009) 072501}] are used. The predicted results of these models are basically consistent. At the same time, through analyzing the changing trend of $alpha$ decay energy $Q_{alpha}$ of emph{Z} = 118, 120, 122, 124, 126 and 128 isotopes nuclei with the increasing of neutron number emph{N} and that of $alpha$ decay preformation factor $P_alpha$ of those isotopes even-even nuclei with the increasing of neutron number emph{N}, emph{N} = 178 may be a new neutron magic number.
Artificial neural networks are trained by a standard backpropagation learning algorithm with regularization to model and predict the systematics of -decay of heavy and superheavy nuclei. This approach to regression is implemented in two alternative modes: (i) construction of a statistical global model based solely on available experimental data for alpha-decay half-lives, and (ii) modeling of the {it residuals} between the predictions of state-of-the-art phenomenological model (specifically, the effective liquid-drop model (ELDM)) and experiment. Analysis of the results provide insights on the strengths and limitations of this application of machine learning (ML) to exploration of the nuclear landscape in regions beyond the valley of stability.
In the present work we calculate the allowed $beta^-$-decay half-lives of nuclei with $Z = 20 -30$ and N $leq$ 50 systematically under the framework of the nuclear shell model. A recent study shows that some nuclei in this region belong to the island of inversion. We perform calculation for $fp$ shell nuclei using KB3G effective interaction. In the case of Ni, Cu, and Zn, we used JUN45 effective interaction. Theoretical results of $Q$ values, half-lives, excitation energies, log$ft$ values, and branching fractions are discussed and compared with the experimental data. In the Ni region, we also compared our calculated results with recent experimental data [Z. Y. Xu {it et al.}, emph{Phys. Rev. Lett.} textbf{113}, 032505, 2014]. Present results agree with the experimental data of half-lives in comparison to QRPA.
Spontaneous fission and alpha decay are the main decay modes for superheavy nuclei. The superheavy nuclei which have small alpha decay half-life compared to spontaneous fission half-life will survive fission and can be detected in the laboratory through alpha decay. We have studied the alpha decay half-life and spontaneous half-life of some superheavy elements in the atomic range Z = 100-130. Spontaneous fission half-lives of superheavy nuclei have been calculated using the phenomenological formula and the alpha decay half-lives using Viola-Seaborg-Sobiczewski formula (Sobiczewski et al. 1989), semi empirical relation of Brown (1992) and formula based on generalized liquid drop model proposed by Dasgupta-Schubert and Reyes (2007). The results are reported here.
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