Comprehensive shell model study of β+/EC-decay properties for f5/2pg9/2 space nuclei

Abstract

In this study, we investigate the half-lives of the allowed combined β+ and electron-capture (β+/EC) decays of nuclei with Z=31-40 and A=60-89 employing shell-model calculations within the f5/2pg9/2 valence space using the JUN45 interaction. Using the quenching factor q=0.71±0.01 for the weak axial coupling gA, obtained from the analysis of pure Gamow–Teller β- and β+ decay processes in nuclei with Z=31-40 and A=61-87, the transition strengths and branching ratios for the β+/EC decays are evaluated. The experimental β-decay half-lives are found to be rather well explained by the shell-model calculations. We investigate also the isospin mixing in the ground states of 64Ge, 70Se, and 78Rb nuclei for non-analog 0+→0+(ΔT≠0)β transitions from 64Ge, 70Se, and 78Rb. A comprehensive study of the β+/EC-decay processes in nuclei in this region is done for the first time in the present work. Though the model space has a limitation due to the lack of its f7/2 and g7/2 spin-orbit partners, the results obtained can be considered reasonable. © The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2025.