Two-neutron emission in the absorption of stopped pions on lithium isotopes

The (${\pi }^{-}$,$2n$) reaction on ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ and ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ nuclei has been studied in a kinematically complete experiment. Distributions of excitation energy of residual nuclei, of recoil momentum, and of angle spanned by relative and c.m. momenta of emitted neutrons have been extracted. The reaction mechanism has been investigated through a comparison with theoretical predictions.