Elastic pion scattering from Li6,7 and C12,13

Elastic scattering of 50 MeV ${\pi }^{+}$ projectiles from targets of ${}_{}{}^{6,7}{}_{}{}^{}\mathrm{Li}$ and ${}_{}{}^{12,13}{}_{}{}^{}\mathrm{C}$ has been studied. Effects due to isotopic differences between targets are clearly visible in the data. The results are compared to three model descriptions for the cross section ratios for isotope pairs; in the case of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$-${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ a simple core-plus-valence-neutron model works well for ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ if the core (${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$) potential describes observed ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ elastic scattering. Such a model does not work for the ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$-${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ ratio due to improper treatment of the scattering process and the quadrupole moments of the Li ground states.