Pion scattering to 6−stretched states in32S

Abstract

Inelastic ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$ differential cross-section measurements at a pion incident energy of 162 MeV were made for 12 ${(f}_{7/2}^{}{d}_{5/2}^{}\ensuremath{-}1)$ 6${}^{\ensuremath{-}}$ states in ${}^{32}$S, including four tentative new isoscalar states. Isoscalar and isovector magnetic structure coefficients were determined for each state by combining the pion data with previous electron scattering data. The trend of small isoscalar/isovector strength ratios continues in ${}^{32}$S, with the isovector strength being comparable to theoretical calculations, but the isoscalar strength exhausting only about 17% of an extreme-single-particle-hole model. However, this isoscalar strength is larger than that observed in other $\mathrm{sd}$-shell nuclei and exhausts 75% of large-basis shell-model predictions. The substantial fragmentation of the 6${}^{\ensuremath{-}}$ isovector strength observed in ${}^{32}$S electron scattering, but not previously observed in other self-conjugate nuclei, appears to extend to the isoscalar strength and to include substantial isospin mixing. The general systematics of isoscalar and isovector stretched state transition strengths are reviewed.