Proton-neutron Random Phase Approximation Research Articles

Neutron skin thickness of 90Zr and symmetry energy constrained by charge exchange spin-dipole excitations* *Supported by the National Natural Science Foundation of China (12275025, 11975096, 12135004, 11961141004, 11635003), and the Fundamental Research Funds for the Central Universities (2020NTST06)

The charge exchange spin-dipole (SD) excitations of Zr are studied using the Skyrme Hartee-Fock plus proton-neutron random phase approximation with SAMi-J interactions. The experimental value of the model-independent sum rule obtained from the SD strength distributions of Zr(p, n)Nb and Zr(n, p)Y is used to deduce the neutron skin thickness. The neutron skin thickness of Zr is extracted as fm, which is similar to the results of other studies. Based on the correlation analysis of the neutron skin thickness and the nuclear symmetry energy J as well as its slope parameter L, a constraint from the extracted leads to the limitation of J to MeV and L to MeV.

Gamow–Teller strength in 56 Fe nucleus at finite temperatures

In this work, the effect of temperature on Gamow-Teller strength is investigated using fully self-consistent finite temperature proton-neutron random phase approximation in the 56 Fe nucleus. The calculations are performed with Skyrme-type SkM* interaction at T = 0, 1, and 2 MeV. It is shown that temperature effects of the occupation probabilities of states and new excitation channels become possible due to the smearing of the Fermi surface. The Gamow-Teller excitation energies shift downward and new excited states are also obtained in the low-energy region due to the unblocked transitions at high temperatures.

γ-decay of in proton–neutron Tamm–Dancoff and random phase approximations with optimized surface δ interaction

γ-ray transitions from excited states of and isomers that appear in the γ spectrum of the beta decay chain are investigated. The theoretical approach used in this research starts with a mean-field potential consisting of a phenomenological Woods–Saxon potential including spin-orbit and Coulomb terms (for protons) in order to obtain single-particle energies and wave functions for nucleons in a nucleus. A schematic residual surface delta interaction is then employed on the top of the mean field and is treated within the proton–neutron Tamm–Dancoff approximation (pnTDA) and the proton–neutron random phase approximation. The goal is to use an optimized surface delta interaction interaction, as a residual interaction, to improve the results. We have used artificial intelligence algorithms to establish a good agreement between theoretical and experimental energy spectra. The final results of the ‘optimized’ calculations are reasonable via this approach.

Impact of tensor force on β decay of magic and semimagic nuclei.

The effect of the tensor force on β decay is studied in the framework of the proton-neutron random phase approximation with the Skyrme force. The investigation is performed for even-even semimagic and magic nuclei, (34)Si, (68,78)Ni, and (132)Sn. The tensor correlation induces strong impact on the low-lying Gamow-Teller state. In particular, it improves the β-decay half-lives. Q and ft values are also investigated and compared with experimental data.

Gamow-Teller transitions and deformation in the proton-neutron random phase approximation

We investigate reliability of Gamow-Teller transition strengths computed in the proton-neutron random phase approximation, comparing with exact results from diagonalization in full $0\ensuremath{\hbar}\ensuremath{\omega}$ shell-model spaces. By allowing the Hartree-Fock state to be deformed, we obtain good results for a wide variety of nuclides, even though we do not project onto good angular momentum. We suggest that deformation is as important or more so than pairing for Gamow-Teller transitions.

Compressional and toroidal dipole modes in nuclei

We studied the nuclear electric isoscalar dipole response in proton–neutron random-phase approximation using different separable Hamiltonians and carried out a detailed comparison with the available experimental data. The analysis of the response to the different pieces of the Hamiltonian has disclosed properties of the compressional dipole mode not directly accessible to previous realistic approaches and, thereby, has identified some of the reasons of the discrepancies between these calculations and the experiments. In this perspective we have also studied the structure of the toroidal operator, its relation to the pure and compressional dipole fields, and computed its contribution to the dipole response.

Description of the ground-state pionic double charge exchange reaction on 128,130Te

The pionic double change exchange reactions 128,130Te( π +, π −) 128,130Xe are investigated within the proton-neutron random-phase approximation. The approach is fpund to give a satisfactory agreement of the calculated differential cross sections and angular distributions with recent data. A strong dependence of the calculated quantities on the strength g pp of the particle-particle force is observed. This behaviour is similar to that reported for the β + decay in neutron-dificient nuclei and the double beta decay. The role of the DCX for the interpretation of the ratio of the double beta decay half-lives of the tellurium isotopes is discussed.