Beta Decay ofS38

Abstract

The ${\beta }^{-}$ decay of ${\mathrm{S}}^{38}$ to states of ${\mathrm{Cl}}^{38}$ has been studied with Si, Ge(Li), and NaI(Tl) detectors. ${\mathrm{S}}^{38}$ was produced in the reaction ${\mathrm{S}}^{36}\mathrm{}(t,p)\mathrm{}{\mathrm{S}}^{38}$ at $E_t=3.26\mathrm{}$ MeV by bombarding ${\mathrm{Ag}}_2$S targets, enriched to 1.93% in ${\mathrm{S}}^{36}$. The half-life was measured to be 169.6 ± 0.7 min. The main $\beta$ branch (83 ± 2)% with end-point energy 1005 ± 20 keV proceeds to a previously unidentified level of ${\mathrm{Cl}}^{38}$ at 1942 keV. A 1941.7 ± 0.2-keV $\gamma$ ray has been observed in coincidence with this branch. The $\Delta T=1\mathrm{} \beta$ transition is allowed ($logft=4.98\mathrm{}\pm 0.03$) giving $J^{\pi }=1^{+}$ for ${\mathrm{Cl}}^{38}$ (1942 keV). The $\gamma$ decay of the 1942-keV level proceeds 100% to the ${\mathrm{Cl}}^{38}$ ground state, and an upper limit of 0.4% can be set for any other possible decay mode. No $\gamma$ rays in coincidence with the 1942-keV $\gamma$ ray were observed. The $\beta$- and $\gamma$-ray measurements determine the $Q$ value for the ${\mathrm{S}}^{38}\left({\beta }^{-}\right){\mathrm{Cl}}^{38}$ reaction as 2947 ± 20 keV. In addition to the main branch a (2.8 ± 0.3)% branch proceeds to the 1746.2 ± 0.4-keV level, which decays predominantly to the ${\mathrm{Cl}}^{38}$ ground state. The $log\mathrm{ft} \mathrm{of} 6.76\pm 0.05$ restricts the 1746-keV level to have $J^{\pi }=0^{-},1^{-}, or 1^{+}$; the ${\mathrm{Cl}}^{37}\mathrm{}(d,p)\mathrm{}$ reaction establishes the parity as odd. No other $\gamma$ rays from ${\mathrm{Cl}}^{38}$ were observed, which leads to a value of (14.2 ± 2)% for the...