Absorption Spectrum of NaNO3Exposed to Ionizing Radiation

Abstract

The changes produced by ionizing radiation in the absorptionspectrum of NaNO3 crystals are in the main caused by two effects: the conversion of NO3 — ions into NO2 — ions with an absorption band, which has its peak at 345 mμ and shows a characteristicstructure when observed at low temperature; and the production of color centers with a continuous absorption band with peak at 335 mμ. The formation of the color centers is assumed to be connected with the presence in the lattice of NO2 — ions, although no precise model can be proposed for these centers. The color center band can be bleached by ultraviolet light even at — 190°C; at room temperature it is partially destroyed by the ionizing radiation which is able to produce the centers, while this is not the case with respect to the NO2 — ions. Therefore the NO2 — band is relatively much stronger in crystals exposed to the ionizing radiation at higher temperatures, for instance in the pile, while in crystals x‐rayed at — 190°C the color center band prevails.