The ¹⁴N(n,n′γ) Cross Section of the 2.313-MeV First Excited State

The neutron-induced gamma-ray production cross section for the first excited state of ^l4N was measured for neutron energies from 2.65 to 3.55 MeV at intervals of 100 keV. An angular distribution from 45 to 135 deg in 10-deg steps was measured at an incident neutron energy of 3.45 MeV. Neutrons were produced by the ⁷Li(p,n)⁷Be reaction using a pulsed proton beam from the University of Massachusetts Lowell 5.5-MV Van de Graaff accelerator. The interaction of neutrons from the ⁷Li(p,n)⁷Be* reaction in the sample was taken into account. A calibrated ²³⁵U fission chamber was used to measure the absolute incident neutron fluence. Gamma rays were detected by a Ge(Li) crystal surrounded by a NaI(Tl) anti-Compton annulus. This spectrometer was used in conjunction with the pulsed-beam time-of-flight technique to attenuate background. The measured cross section compares favorably with other experimental data and with the ENDF/B-VI evaluation.