β -decay spectroscopy of S27

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.

Relativistic Hydrodynamics of Particles with Spin 1/2

“…[17] and developed in Refs. [18,19,20] (see the recent review [21] and related works [22,23,24]). Within this approach, the space-time evolution of polarization is determined by the conservation law for total angular momentum -for particles with spin, the latter turns out to have a non-trivial form.…”

β-Delayed γ Emissions of 26P and Its Mirror Asymmetry

“…Large asymmetries in mirror Gamow-Teller transitions have been associated with transitions involving halo states [6]. So as to systematically study the isospin symmetry breaking, β decays of the sd shell mirror nuclei near the proton drip line have been investigated [7][8][9][10][11][12][13][14][15]. The largest value of mirror asymmetry (δ = 209(96)%) in low-lying states in 22 Si/ 22 O was found in a recent paper [8], supporting the proton halo in 22 Al.…”

Hydrodynamics with Spin --- Recent Developments

“…[21] and for related works see Refs. [22,23,24]). In the approach proposed in [17], which forms the basis for relativistic perfectfluid hydrodynamics of particles with spin 1 /2, the space-time evolution of the polarized fluid is determined by the conservation laws including the conservation of total angular momentum (we note that for particles with spin, the latter has a non-trivial form).…”