Neutron Radii Determinations from the Ratio ofπ−Elastic Scattering fromC12,13andO16,18

Differential elastic cross-section ratios and absolute cross sections have been measured for ${}_{}{}^{12,13}{}_{}{}^{}\mathrm{C}$ at 29.2-and 49.5-MeV average ${\pi }^{-}$ energy and for ${}_{}{}^{16,18}{}_{}{}^{}\mathrm{O}$ at 29.2 MeV. Range telescopes detected the scattered pions. The ratio data were compared with different optical-potential calculations to extract neutron radii of 2.35 ± 0.03 fm for ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ and 2.81 ± 0.03 fm for ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$, relative to the neutron radii of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ (2.31) and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ (2.60), respectively. Our studies indicate little sensitivity to the optical model used.