Gamma Radiation from the Interaction of 4.4-Mev Neutrons withFe54andFe56

The gamma radiation from the interaction of 4.4±0.1 Mev neutrons with naturally occurring iron has been compared with that from a sample enriched to 34 percent ${\mathrm{Fe}}^{54}$. The methods used for detection of gamma rays from small samples and the shielding of the NaI detector are described. The results show that the well-known 0.85-Mev gamma ray comes from ${\mathrm{Fe}}^{56}$, and that ${\mathrm{Fe}}^{54}$ emits a gamma ray of energy 1.40±0.02 Mev. The ratio of the cross section for production of this 1.40-Mev radiation to that of the 0.85 Mev is 0.62±0.07 at 4.4 Mev neutron energy, and 0.68±0.10 at 3.9 Mev. The 1.40-Mev gamma ray is tentatively assigned to the reaction ${\mathrm{Fe}}^{54}(n, n^{\prime }){\mathrm{Fe}}^{54*}\left(\gamma \right){\mathrm{Fe}}^{54}$, and is believed to represent the de-excitation of the first excited state.