We have analyzed the pion-induced double-charge-exchange data for the direct population of the ground state of ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$ by the ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$(${\mathrm{\pi }}^{\mathrm{-}}$,${\mathrm{\pi }}^{+}$${)}^{11}$Li reaction. We find that the measured cross section determines the rms radius of the last two neutrons in ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$ to be 5.$1_{\mathrm{-}0.9}^{+0.6\mathrm{}}$ fm, which corresponds to a total neutron rms radius for the nucleus of 3.${28}_{\mathrm{-}0.33}^{0.24}$ fm. We show that for large assumed neutron-halo radii the cross section decreases as the radius of the halo to the inverse sixth power and that a radius of 12 fm leads to a cross section which is 3 orders of magnitude smaller than that measured.

• Received 6 May 1991

DOI:https://doi.org/10.1103/PhysRevLett.67.1395