Excitation of High-Spin Particle-Hole States inSi28by Pion Inelastic Scattering

The inelastic scattering of 162-MeV ${\pi }^{+}$ and ${\pi }^{-}$ by ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ was studied at larger momentum transfer. Several high-spin particle-hole states are observed to be preferentially excited in this reaction. These include the 9.70-MeV ($5^{-}$,$T=0\mathrm{}$), 11.58-MeV ($6^{-}$,$T=0\mathrm{}$) and 14.36-MeV ($6^{-}$,$T=1\mathrm{}$) states. The ratios of the cross sections of the $6^{-}$, $T=0\mathrm{}$ state to the $6^{-}$, $T=1\mathrm{}$ state are ${1.5}_{-0.2\mathrm{}}^{+0.4\mathrm{}}$ for ${\pi }^{+}$ and 1.7±0.4 for ${\pi }^{-}$, in contrast to ratios of about 4 predicted by simple distorted-wave impulse-approximation calculations.