New effective interaction forpf-shell nuclei and its implications for the stability of theN=Z=28closed core

Abstract

The effective interaction GXPF1 for shell-model calculations in the full pf shell is tested in detail from various viewpoints such as binding energies, electro-magnetic moments and transitions, and excitation spectra. The semi-magic structure is successfully described for N or Z = 28 nuclei, 53 Mn, 54 Fe, 55 Co and 56,57,58,59 Ni, suggesting the existence of significant core-excitations in low-lying nonyrast states as well as in high-spin yrast states. The results of N = Z odd-odd nuclei, 54 Co and 58 Cu, also confirm the reliability of GXPF1 interaction in the isospin dependent properties. Studies of shape coexistence suggest an advantage of Monte Carlo Shell Model over conventional calculations in cases where full-space calculations still remain too large to be practical.

Beta-Decay Studies in N ≈ Z Nuclei Using No-Core Configuration-Interaction Model

“…First two columns show old and new experimental data, see [6] for details. Next three columns collect the results of shell-model calculations using MSDI3 [13], GXPF1 [14], and GXPF1A [15] interactions, respectively. Last column shows the results obtained in this work using six reference Slater determinants described in the text.…”

Nuclear structure of the odd–odd nucleus58Co

“…However, it has been shown that this core is rather soft and only a very limited description is provided by the closed-shell model for the magic number 28 [4]. These structures were successfully described for N or Z = 28 nuclei only after considering the existence of significant core-excitations in low-lying non-yrast states as well as in high-spin yrast states [3].…”

“…We have used the model space and the residual interaction named GXPF1, developed for the description of fp-nuclei [3,18]. The calculation with the GXPF1 interaction was performed in the full fp shell with up to eight particle excitations from the 1f 7/2 orbital to the 1p 3/2 , 1f 5/2 and 1p 1/2 orbitals.…”

“…Nuclei close to doubly magic shell closures have been the object of extensive experimental and theoretical investigations [1][2][3]. Spectroscopic data from these nuclei provide essential information for the parameter sets of spherical shell model calculations and apply severe constraints on the outcome of such calculations and, consequently, define the effective nuclear forces.…”

In-beam gamma ray spectroscopy of 58Co

“…The results are compared to Shell Model calculations using the GXPF1 effective interaction, developed for use in the fp shell. The πf −1 7/2 ⊗ν(p 2 3/2 f 1 5/2 ) configuration was assigned to the yrast levels.Nuclei close to doubly magic shell closures are the object of extensive experimental and theoretical investigations [1][2][3]. Spectroscopic data from these nuclei provide essential information for the parameter sets of spherical shell-model calculations.…”