No abstract

No abstract

The β-delayed γ-ray spectroscopy of neutron-rich 123;125 Ag isotopes is investigated at the Radioactive Isotope Beam Factory of RIKEN, and the long-predicted 1=2 − β-emitting isomers in 123;125 Ag are identified for the first time. With the new experimental results, the systematic trend of energy spacing between the lowest 9=2 þ and 1=2 − levels is extended in Ag isotopes up to N ¼ 78, providing a clear signal for the reduction of the Z ¼ 40 subshell gap in Ag towards N ¼ 82. Shell-model calculations with the state-of-theart V MU plus M3Y spin-orbit interaction give a satisfactory description of the low-lying states in 123;125 Ag.

No abstract

Background: β-decay spectroscopy provides valuable information on exotic nuclei and a stringent test for nuclear theories beyond the stability line. Purpose: To search for new β-delayed protons and γ rays of 25 Si to investigate the properties of 25 Al excited states. Method: 25 Si β decays were measured by using the Gaseous Detector with Germanium Tagging system at the National Superconducting Cyclotron Laboratory. The protons and γ rays emitted in the decay were detected simultaneously. A Monte Carlo method was used to model the Doppler broadening of 24 Mg γ-ray lines caused by nuclear recoil from proton emission. Shell-model calculations using two newly-developed sd-shell Hamiltonians, USDC and USDI, were performed. Results: The most precise 25 Si half-life to date has been determined. A new proton branch at 724(4) keV and new proton-γ-ray coincidences have been identified. Three 24 Mg γ-ray lines and eight 25 Al γ-ray lines are observed for the first time in 25 Si decay. The first measurement of the 25 Si β-delayed γ ray intensities through the 25 Al unbound states is reported. All the bound states of 25 Al are observed to be populated in the β decay of 25 Si. Several inconsistencies between the previous measurements have been resolved, and new information on the 25 Al level scheme is provided. An enhanced decay scheme has been constructed and compared to the mirror decay of 25 Na and the shell-model calculations. Conclusions: The measured excitation energies, γ-ray and proton branchings, log f t values, and Gamow-Teller transition strengths for the states of 25 Al populated in the β decay of 25 Si are in good agreement with the shell model calculations, offering gratifyingly consistent insights into the fine nuclear structure of 25 Al.