Radiation-induced phenomena in air: Ionization and fluorescence

Gamma rays induce ionization and fluorescence in the surrounding air. On the premise that the radiation may therefore be detected using these radiation-induced phenomena, we perform a Monte Carlo simulation to find out how the electron-emitting and photon-emitting molecular sites are distributed around the source. Focusing on the second positive and the first negative UV photons from the nitrogen molecules, the fluorescing sites are distributed following the pattern of r−β with β=1.4 for 0<r<1 m, but with β=2.04 for 1 m<r<120 m. For r>120 m, the distribution falls more rapidly than can be described with a power law. Nearly the same pattern of distribution prevails for the ionizing molecular sites.