Cluster Interpretation of Properties of Alternating Parity Bands in Heavy Nuclei

The properties of the states of the alternating parity bands in actinides, Ba, Ce and Nd isotopes are analyzed within a cluster model. The model is based on the assumption that cluster type shapes are produced by the collective motion of the nuclear system in the mass asymmetry coordinate. The calculated spin dependences of the parity splitting and of the electric multipole transition moments are in agreement with the experimental data.Comment: 29 pages, 10 figure

Alpha-decay fine structures of U isotopes and systematics for isotopic chains of Po and Rn

A model of the cluster radioactivity of even-even nuclei is presented. In this model, the zero-point vibrations in the charge-asymmetry coordinate determine the cluster formation (spectroscopic factor), while the tunneling in the coordinate of the relative separation of the centers of mass of the cluster and the daughter nucleus determines the penetrability of the barrier of the nucleus-nucleus potential. The quality of the model is demonstrated for describing cluster decay half-lives and the fine structure in alpha decays of even-even U isotopes. The model is applied to describe the alpha decays in the isotopic chains of Po, Rn, and U. The correspondence of the calculated half-lives to the Geiger-Nuttall law is discussed

Level Densities of Nuclei with Z = 112–120

© 2020, Allerton Press, Inc. Abstract: Level densities of superheavy nuclei with Z = 112–120 in the ground state and at the saddle point are calculated using single-particle spectra obtained in a macroscopic and microscopic model based on the Woods–Saxon single-particle potential. Level density parameters are calculated by fitting the results with the expression of a Fermi gas. The role of shell correction and pairing effects in the behavior of the level density parameter in the ground state and at the saddle point is studied. The results from calculations are compared to phenomenological expressions. The ratio of the level density parameter at the saddle point to its values ​​in the ground state is presented

Effect of the Nucleon-Density Distribution on the Description of Nuclear Decay

© 2020, Pleiades Publishing, Ltd. Abstract: It is proposed to test the parameters used in a self-consistent analysis of the nucleon distribution in nuclei via the calculation of the nucleus–nucleus potential, which is necessary for describing nuclear decays. The nucleon distribution is shown to correlate with the parameters of the nucleon–nucleon interaction. A unified approach to calculating characteristic alpha-decay and spontaneous-fission times is developed on the basis of the dinuclear-system model

Description of Stabilization of Octupole Deformation in Alternating-Parity Bands of Heavy Nuclei

© 2020, Pleiades Publishing, Ltd. Abstract: The angular-momentum dependences are analyzed for parity splitting and electric dipole transitions in alternating-parity bands of heavy nuclei. It is shown that these dependences can be treated universally by employing a single parameter taken to be a critical angular momentum that characterizes the phase transition from octupole vibrations to a stable octupole deformation. Analytic expressions for parity splitting and the electric dipole transitional moment are obtained on the basis of a simple model. The results are compared with experimental data for various barium, cerium, and neodymium isotopes

Impact of nuclear structure on the production and identification of superheavy nuclei

The shell structure of heavy nuclei with Z > 104, which can be produced in actinide-based complete fusion reactions, is studied with a modified two-center shell model. Using the macroscopic-microscopic approach, mass excesses and Qα-values are calculated and compared with available experimental data. The production cross sections of new superheavy nuclei decisively depend on the position of the proton shell closure

Description of the low-lying collective states of Zr 96 based on the collective Bohr Hamiltonian including the triaxiality degree of freedom

© 2020 American Physical Society. Background: Several collective low-lying states are observed in Zr96 whose properties, which include excitation energies and E2, E0, and M1 transition probabilities, indicate that some of them belong to the spherical state and the other to deformed states. A consideration of these data in the full framework of the geometrical collective Model with both intrinsic shape variables, β and γ, and rotational degrees of freedom is necessary for Zr96. Purpose: We investigate the properties of the low-lying collective states of Zr96 based on the five-dimensional geometrical collective model including triaxiality as an active degree of freedom. Method: The quadrupole-collective Bohr Hamiltonian, depending on both β and γ shape variables with a potential having spherical and deformed minima, is applied. The relative depth of two minima, height and width of the barrier, and rigidity of the potential near both minima are determined so as to achieve a satisfactory description of the observed properties of the low-lying collective quadrupole states of Zr96. Results: It is shown that the low-energy structure of Zr96 can be described in a satisfactory way within the geometrical collective model with a potential function supporting shape coexistence without other restrictions on its shape. It is shown that a correct determination of the β dependence of the collective potential from the experimental data requires a consideration in the framework of the full Bohr collective Hamiltonian. It is shown also that the excitation energy of the 22+ state can be reproduced only if the rotation inertia coefficient is taken to be four times smaller than the vibrational one in the region of the deformed well. It is shown also that shell effects are important for the description of the B(M1;22+→21+) and B(M1;31+→21+) transition probabilities. An indication of the influence of the pairing vibrational mode on the 02+→01+ transition is confirmed, in agreement with the previous result. Conclusion: Qualitative agreement with the experimental data on the excitation energies and B(E2) and B(M1;22+→21+) reduced transition probabilities is obtained