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Register a new userSystematic study of $alpha$ decay for odd-$A$ nuclei within a two-potential approach
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$alpha$ decay is usually associated with both ground and low-lying isomeric states of heavy and superheavy nuclei, and the unpaired nucleon plays a key role on $alpha$ decay. In this work, we systematically studied the $alpha$ decay half-lives of odd-$A$ nuclei, including both favored and unfavored $alpha$ decay within the two-potential approach based on the isospin dependent nuclear potential. The $alpha$ preformation probabilities are estimated by using an analytic formula taking into account the shell structure and proton-neutron correlation, and the parameters are obtained through the $alpha$ decay half-lives data. The results indicate that in general the $alpha$ preformation probabilities of even-$Z$, odd-$N$ nuclei are slightly smaller than the odd-$Z$, even-$N$ ones. We found that the odd-even staggering effect may play a more important role on spontaneous fission than $alpha$ decay. The calculated half-lives can well reproduce the experimental data.
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In this work, we systematically study the two-proton($2p$) radioactivity half-lives using the two-potential approach while the nuclear potential is obtained by using Skyrme-Hartree-Fock approach with the Skyrme effective interaction of {SLy8}. For true $2p$ radioactivity($Q_{2p}$ $>$ 0 and $Q_p$ $< $0, where the $Q_p$ and $Q_{2p}$ are the released energy of the one-proton and two-proton radioactivity), the standard deviation between the experimental half-lives and our theoretical calculations is {0.701}. In addition, we extend this model to predict the half-lives of 15 possible $2p$ radioactivity candidates with $Q_{2p}$ $>$ 0 taken from the evaluated atomic mass table AME2016. The calculated results indicate that a clear linear relationship between the logarithmic $2p$ radioactivity half-lives $rm{log}_{10}T_{1/2}$ and coulomb parameters [ ($Z_{d}^{0.8}$+$l^{0.25}$)$Q_{2p}^{-1/2}$] considered the effect of orbital angular momentum proposed by Liu $et$ $al$ [Chin. Phys. C textbf{45}, 024108 (2021)] is also existed. For comparison, the generalized liquid drop model(GLDM), the effective liquid drop model(ELDM) and Gamow-like model are also used. Our predicted results are consistent with the ones obtained by the other models.
The quartet condensation model (QCM) is extended for the treatment of isovector and isoscalar pairing in odd-odd N=Z nuclei. In the extended QCM approach the lowest states of isospin T=1 and T=0 in odd-odd nuclei are described variationally by trial functions composed by a proton-neutron pair appended to a condensate of 4-body operators. The latter are taken as a linear superposition of an isovector quartet, built by two isovector pairs coupled to the total isospin T=0, and two collective isoscalar pairs. In all pairs the nucleons are distributed in time-reversed single-particle states of axial symmetry. The accuracy of the trial functions is tested for realistic pairing Hamiltonians and odd-odd N=Z nuclei with the valence nucleons moving above the cores $^{16}$O, $^{40}$Ca and $^{100}$Sn. It is shown that the extended QCM approach is able to predict with high accuracy the energies of the lowest T=0 and T=1 states. The present calculations indicate that in these states the isovector and the isoscalar pairing correlations coexist together, with the former playing a dominant role.
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.
In this work, we systematically study the $alpha$ decay preformation factors $P_{alpha}$ and $alpha$ decay half-lives of 152 nuclei around $Z$ = 82, $N$ = 126 closed shells based on a generalized liquid drop model while $P_{alpha}$ is extracted from the ratio of the calculated $alpha$ decay half-life to the experimental one. The results show that there is an obvious linear relationship between $P_{alpha}$ and the product of valance protons (holes) $N_p$ and valance neutrons (holes) $N_n$. At the same time, we extract the $$P_{alpha}$ values of even-even nuclei around $emph{Z}$ = 82, $emph{N}$ = 126 closed shells from the work of Sun textit{et al.} [href {https://doi.org/10.1088/1361-6471/aac981} {J. Phys. G: Nucl. Part. Phys. $bm{45}$, 075106 (2018)}], in which the $P_{alpha}$ can be calculated by two different microscopic formulas. We find that the $P_{alpha}$ are also related to $N_pN_n$. Combining with our previous works [Sun textit{et al.}, href {https://doi.org/10.1103/PhysRevC.94.024338} {Phys. Rev. C $bm{94}$, 024338 (2016)}; Deng textit{et al.}, href {https://doi.org/10.1103/ PhysRevC 96.024318} {ibid. $bm{96}$, 024318 (2017)}; Deng textit{et al.}, href {https://doi.org/10.1103/PhysRevC.97.044322} {ibid. $bm{97}$, 044322 (2018)}] and the work of Seif textit{et al.} [href {http://dx.doi.org/10.1103/PhysRevC.84.064608}{Phys. Rev. C $bm{84}$, 064608 (2011)}], we suspect that this phenomenon of linear relationship for the nuclei around those closed shells is model independent. It may be caused by the effect of the valence protons (holes) and valence neutrons (holes) around the shell closures. Finally, using the formula obtained by fitting the $P_{alpha}$ calculated by the generalized liquid drop model (GLDM), we calculate the $alpha$ decay half-lives of these nuclei. The calculated results are agree with the experimental data well.
A systematic study of the doublet bands observed in odd-odd mass $sim$ 100 is performed using the microscopic triaxial projected shell model approach. This mass region has depicted some novel features which are not observed in other mass regions, for instance, it has been observed that two chiral bands cross diabatically in $^{106}$Ag. It is demonstrated that this unique feature is due to crossing of the two 2-quasiparticle configurations having different intrinsic structures. Further, we provide a complete set of transition probabilities for all the six-isotopes studied in this work and it is shown that the predicted transitions are in good agreement with the available experimental data.
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