Nuclear DeexcitationγRays inN14,C14, andN15Followingπ−Capture onO16

Negative pions produced by the National Aeronautics and Space Administration Space Radiation Effects Laboratory cyclotron were stopped in water and the nuclear deexcitation $\gamma$ rays observed. $\gamma$ rays from ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$, ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$, and ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ were identified, and yields to particular states in these nuclei obtained. A prominent $\gamma$-ray peak in our spectra was from the 3.945-MeV $1^{+}$ state in ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ which was formed with a rate of 1.8% per stopped pion. The Doppler-broadened line shape of the decay $\gamma$ ray for this state was analyzed to obtain the momentum distribution of the recoiling ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ nucleus. This momentum distribution is compared with momentum distributions obtained by related experiments, and to theoretical predictions. Yields to various states are presented and discussed.