Gamow-Teller transitions of neutron-rich N = 82, 81 nuclei by shell-model calculations

β-decay half-lives of neutron-rich nuclei around N = 82 are key data to understand the r-process nucleosynthesis. We performed large-scale shell-model calculations in this region using a newly constructed shell-model Hamiltonian, and successfully described the low-lying spectra and half-lives of neutron-rich N = 82 and N = 81 isotones with Z = 42 − 49 in a unified way. We found that their Gamow-Teller strength distributions have a peak in the low-excitation energies, which significantly contributes to the half-lives. This peak, dominated by ν0g7/2 → π0g9/2 transitions, is enhanced on the proton deficient side because the Pauli-blocking effect caused by occupying the valence proton 0g9/2 orbit is weakened.

Nilsson orbitals in quantum superintegrable systems

Recent studies [1] of the valence proton-neutron interaction through certain double differences of binding energies suggest that Nilsson orbitals with ΔK[ΔNΔn_zΔΛ] = 0[110] are responsible for large overlaps of wave functions in heavy deformed nuclei. We show that pairs of orbitals of this kind belong to neighboring irreducible representations of appropriate deformed U(3) algebras [2], being interconnected by deformed creation and annihilation operators. These deformed U(3) algebras correspond to oscillators with rational ratios of frequencies, which are examples of quantum superintegrable systems [3].

Proton drip line nuclei in the Relativistic Hartree-Bogoliubov model

The Relativistic Hartree Bogoliubov (RHB) theory is applied to the description of ground-state properties of proton-rich odd-Z nuclei. The model predicts the location of the proton drip-line, the ground-state quadrupole deformations and one-proton separation energies at and beyond the drip-line, the deformed single-particle Orbitals occupied by the odd valence proton, and the corresponding spectroscopic factors. The results of fully self-consistent RHB calculations are compared with experimental data on deformed and transitional proton emitters and the predictions of various mass models.

Density distributions and form factors of the exotic 8B nucleus

Results of charge, neutron and matter densities and related form factors for one- proton halo nucleus 8B are presented using a two- frequency shell model approach. We choose a model space for the core of 7Be different from that of the extra one valence proton. One configuration is assumed for the outer proton to be in 1p1/2 - shell. The results of the matter density distributions are compared with those fitted to the experimental data. The calculated proton and matter density distributions of this exotic nucleus exhibit a long tail behavior, which is considered as a distinctive feature of halo nuclei. Elastic electron scattering form factors of this exotic nucleus are also studied. The effects of the proton halo on the electron scattering form factors are analyzed. The form factors of the exotic unstable 8B nucleus are compared with those of the stable 10B nucleus. The differences between the results of unstable 8B and stable 10B nuclei come from the long tail in the density distribution of the last proton.

Systematic dependence of Grodzins product rule on NpNn

The systematics of the Grodzins product rule (GPR) is studied from the perspective of the valence-proton and neutron product NpNn in the major shell space Z = 50–82, N = 82–126. The variation of nuclear structure from vibrator to deformed rotor is discussed. The Grodzins product shows more dependence on NpNn in the N ≤ 104 region, as it is a region of deformed nuclei. We present here for the first time the dependence of GPR on the NpNn product.

SYSTEMATIC STUDY OF NUCLEAR SOFTNESS OF SUPERDEFORMED BANDS IN A = 190 MASS REGION

A four parameter formula has been applied to obtain the nuclear softness parameter (σ) for all the superdeformed (SD) bands observed in A = 190 mass region. The nuclear softness parameter values of most of the SD bands are found to be smaller than those of the normal deformed bands, implying more rigidity. The results of this work includes the variation of nuclear softness parameter against the gamma ray energy ratio R(I) = Eγ(I→(I-2))/Eγ((I-2)→(I-4)) of SD bands in A = 190 mass region. The variation of R(I) and the nuclear softness parameter of these SD bands are studied with the product of valence proton and neutron numbers (NpNn). The systematics also includes the variation of σ with the neutron number N. It is also found that the value of softness parameter of signature partner SD bands observed in A = 190 mass region is also the same. We present for the first time the study of softness parameter of SD bands with NpNn scheme.