Isovector stretched-state excitations in theNe20,Mg24,Si28, andS32(p,n) reactions at 136 MeV

Isovector stretched-state excitations were studied in the (p,n) reaction at 136 MeV on the self-conjugate s-d shell nuclei ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$, ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$, and ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$. The measurements were performed in three separate experiments using the beam-swinger neutron time-of-flight facility at the Indiana University Cyclotron Facility. Neutrons were detected in large-volume plastic scintillation detectors located in three detector stations at 0°, 24°, and 45° with respect to the undeflected beam line; the flight paths varied from 75 to 134 m. Overall time resolutions of about 825 ps provided energy resolutions of about 320 keV in the first two stations and about 425 keV in the third station. Both (${\mathit{d}}_{5/2}$,${\mathit{d}}_{5/2}^{\mathrm{-}1}$)$5^{+}$ 0ħω and (${\mathit{f}}_{7/2}$,${\mathit{d}}_{5/2}^{\mathrm{-}1}$)$6^{\mathrm{-}}$ 1ħω stretched-state excitations are observed in the (p,n) reaction on ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$, ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, and ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$.