In a time-of-flight study of ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ photoneutrons in which neutron energy spectra were obtained at different bremsstrahlung end-point energies between 15.5 and 29.5 MeV, de-excitation neutrons from excited states of ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ were observed.

• Received 22 May 1970

DOI:https://doi.org/10.1103/PhysRevLett.25.114