Be9(p→,π−)C10reaction in the 200-250 MeV proton energy range

Measurements of the dependence on incident proton energy of the analyzing power $A_y\left(\theta \right)$ for $\overrightarrow{p}{\pi }^{-}$ production on nuclei are reported for the ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$($\overrightarrow{p}$,${\pi }^{-}$)${}_{}{}^{10}{}_{}{}^{}\mathrm{C}$ reaction leading to the ground state (g.s.) and the first three excited states of ${}_{}{}^{10}{}_{}{}^{}\mathrm{C}$. For the transition to the g.s. the analyzing power shows little dependence on proton energy while for transitions leading to the ${}_{}{}^{10}{}_{}{}^{}\mathrm{C}_{3.35}^{}{}_{}{}^{}$* and ${}_{}{}^{10}{}_{}{}^{}\mathrm{C}_{6.60}^{}{}_{}{}^{}$* states it varies considerably with incident proton energy. Nuclear structure dependence of the $A_y\left(\theta \right)$ is also observed for the first time in $\overrightarrow{p}{\pi }^{-}$ reactions.