A systematic analysis of the relationship between spontaneous fission and alpha-decay half-lives is performed for actinides and superheavy nuclei in the ground state. The ratio of logarithmic half-lives exhibits regular trends with nuclear mass and charge numbers, showing almost constant behavior at fixed neutron excess. Based on these systematics, a new semiempirical formula is proposed that relates spontaneous fission half-lives to alpha-decay half-lives and neutron excess. The formula contains only three fitted parameters and provides a unified description for nuclei of different parities without introducing separate hindrance factors. It reproduces experimental spontaneous fission half-lives with a mean absolute deviation of 0.94 orders of magnitude for the dataset of 78 nuclei. A detailed comparison of the predicted half-lives calculated using microscopic-macroscopic and self-consistent microscopic models, more complex empirical parametrizations, and the new formula is presented. The formula can be used to predict spontaneous fission half-lives and validate experimental data, and it provides a criterion to determine the dominant decay mode (alpha decay or spontaneous fission). The existence of a fundamental relationship between spontaneous fission and alpha-decay processes is discussed.
Potential energy surfaces of superheavy nuclei are investigated within the multidimensionally constrained relativistic mean-field model. The results are analyzed using the Strutinsky shell-correction method, with particular emphasis on 296Lv and isotopic chains of Z = 114 and Z = 120. The analysis reveals that triaxial degrees of freedom substantially reduce the barrier height along the triaxial fission pathway compared to the axial fission path in 296Lv. A steplike behavior emerges in proton shell corrections for Z = 114 isotopes, contrasting with the smoother patterns observed in Z = 120 isotopes, is attributed to the differences in the ground-state deformations. The observed correlation between fission-barrier maxima and shell-correction minima points to the shell closures at neutron numbers N = 172 and N = 184 at Z = 114 and 120.
We develop a self-consistent relativistic second random-phase approximation (RSRPA) based on a covariant energy density functional with density-dependent point-coupling interaction. The formalism extends the conventional simple configuration space composed of particle-hole transitions by including two-particle-two-hole (2p-2h) configurations through a generalized Thouless ansatz and a time-dependent variational principle. To ensure consistency with the underlying mean-field ground state and avoid the double counting of correlations, we implement the subtraction method, in which the static contribution is removed from the residual interaction. The first applications of the RSRPA include studies of isoscalar and isovector giant monopole (ISGMR and IVGMR) and quadrupole resonances (ISGQR and IVGQR) in 16O, which demonstrate the importance of 2p-2h couplings to describe the fragmentation of the transition strength and the stabilizing role of the subtraction method.
Background: With the recent progress in lifetime measurements, there has been strong experimental and theoretical interest in studying the evolution of the collectivity in the long Te isotopic chain. Purpose: The purpose of the present work is to investigate the structure of low-lying excited states in even-even Te nuclei as well as the nu h11/2 band in the odd-mass systems within the interacting boson model framework. Methods: A new open-source Python package is developed to evaluate the eigenvalues and eigenfunctions of a Hamiltonian which contains both the standard nd and essential for triaxial deformation and mixed symmetry effects. Results: Systematic calculations of low-spin yrast and nonyrast states in even-even 108-124Te and odd-even 109-125Te nuclei have been carried out using the newly developed Python package and compared with the neighboring Cd isotopes. From the resulting eigenfunctions, the reduced transition probabilities B(E2) are calculated and compared to adopted values. Due to the vibrational-like structure of the spectra of the Te nuclei, the Hamiltonian is dominated by the vibrational term, which is reflected in the B(E2) values. This alone does not explain the low B4/2 ratios observed in some Te nuclei. However, it is demonstrated via the contour plot that the B4/2 ratios can be highly sensitive to the higher-order terms of the Hamiltonian within specific parameter domains. Conclusions: We demonstrate that inclusion of higher-order interactions can provide a possible explanation of the anomaly observed in certain Te isotopes. The results highlight both the importance of extended IBM Hamiltonians and the utility of pyIBM as a modern computational tool for collective nuclear structure studies. Q & centerdot; Q terms as well as higher-order terms which could be studies
