The energy spectra of neutrons between 2 and 28 MeV emitted following radiative pion capture in carbon, oxygen, and calcium fall off exponentially. An enhancement, however, is observed for neutron energies below 5 MeV in carbon and oxygen. Neutron yield peaks at $n-\gamma$ angles of 180°, indicating a quasifree absorption mechanism in this process.

NUCLEAR REACTIONS ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({\pi }^{-},n\gamma )$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}({\pi }^{-},n\gamma )$, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}({\pi }^{-},n\gamma )$, $E=0\mathrm{}$ MeV; measured reaction rate, neutron energy spectrum, and $n-\gamma$ angular correlations; deduced giant resonance states and direct emission contributions.

• Received 28 January 1974

DOI:https://doi.org/10.1103/PhysRevC.10.72