ReactionS36(p,γ)Cl37and Properties ofCl37

Abstract

The ${\mathrm{S}}^{36}(p,\ensuremath{\gamma}){\mathrm{Cl}}^{37}$ reaction has been studied in the range ${E}_{p}=800\ensuremath{-}1940$ keV in order to determine properties of excited states of ${\mathrm{Cl}}^{37}$. Over 80 narrow resonances due to this reaction were identified and located in proton energy with an accuracy of \ifmmode\pm\else\textpm\fi{}3 keV. The observed resonance strengths $\frac{(2{J}_{r}+1){\ensuremath{\Gamma}}_{\ensuremath{\gamma}}{\ensuremath{\Gamma}}_{p}}{\ensuremath{\Gamma}}$ vary between 0.1 and 6.3 eV, with the exception of the outstanding resonance at 1887\ifmmode\pm\else\textpm\fi{}2 keV, which has a strength of 130\ifmmode\pm\else\textpm\fi{}20 eV. The general behavior of the average resonance strength as a function of proton energy is in agreement with predictions based upon well-known approximate relationships between the level density and the radiative and proton widths ${\ensuremath{\Gamma}}_{\ensuremath{\gamma}}$ and ${\ensuremath{\Gamma}}_{p}$. Detailed studies of the $\ensuremath{\gamma}$-ray decay schemes of resonances at ${E}_{p}=940,969 (\mathrm{doublet}),983,1079, \mathrm{and} 1120$ keV with large NaI (Tl) and Ge(Li) detectors provide evidence for previously unreported levels in ${\mathrm{Cl}}^{37}$ at ${E}_{x}=3.62,3.74, \mathrm{and} (4.4)$ MeV. All of the new bound levels decay to the ground state. No evidence was found for a possible level in ${\mathrm{Cl}}^{37}$ near 0.8 MeV. Spin assignments for each of the resonances listed above were derived from $\ensuremath{\gamma}$-ray angular-correlation measurements. The 1887-keV resonance (${E}_{x}=10.22$ MeV) decays predominantly to the 3.105-MeV level. The resonance and 3.105-MeV levels are each shown to have ${J}^{\ensuremath{\pi}}={\frac{7}{2}}^{\ensuremath{-}}$ and to exhibit other expected properties of the $T=\frac{5}{2}$ and $T=\frac{3}{2}$ members of the $1{f}_{\frac{7}{2}}$ single-nucleon configuration. The resonance is identified as the analog of the ${\mathrm{S}}^{37}$ ground state. The $3.105({\frac{7}{2}}^{\ensuremath{-}})\ensuremath{\rightarrow}({\frac{3}{2}}^{+})$ transition is mixed $E3\ensuremath{-}M2$ with $\ensuremath{\delta}=\ensuremath{-}0.18\ifmmode\pm\else\textpm\fi{}0.01$. The resonance\ensuremath{\rightarrow} 3.105 transition is pure $M1$ with an observed strength of 1.7\ifmmode\pm\else\textpm\fi{}0.3 Weisskopf units, in excellent agreement with a calculated value of 1.6 Weisskopf units for a $(1{f}_{\frac{7}{2}},T=\frac{5}{2})\ensuremath{\rightarrow}(1{f}_{\frac{7}{2}},T=\frac{3}{2})$ transition. A ${\mathrm{S}}^{36}(p,\ensuremath{\gamma}){\mathrm{Cl}}^{37}$ reaction $Q$ value of 8.382\ifmmode\pm\else\textpm\fi{}0.008 MeV was determined from Ge(Li) spectra.