Energy Deposition by Fast Neutrons: NO₂ Production in Liquid Air

Fast neutrons deposit energy in chemical systems by means of elastic scattering, inelastic scattering, and various charged particle reactions. For the particular case of 14.6 Mev neutrons and 1:1 solutions of liquid N₂ and O_2, the proportions by which the three classes of reactions contribute are, respectively, about 1:1:4. The initial linear energy transfer (ILET) in the same system is of the order of 20 ev/Å. Dosimetry in fast neutron radiation chemistry experiments may combine a quantitative consideration of each nuclear reaction with a measurement of the neutron flux. This method of dosimetry has been applied to experiments on the production of NO₂ in 1:1 liquid N₂ and O₂ with the result that G_NO2, the number of NO₂ molecules formed per 100 ev deposited in the sample, was found equal to 0.5 ±0.1. This result is surprisingly close to that observed for irradiations by Co⁵⁰ gamma rays and by electrons whose ILET is three orders of magnitude less than that for 14.6 Mev neutrons.