Electron-, x-ray-, and ion-stimulated decomposition of nitrate salts

Abstract

Decomposition of lithium, sodium, and ammonium nitrate stimulated by 500-eV electrons, 1254-eV X-rays, and 4-keV Ar/sup +/ ions is investigated by X-ray photoelectron spectroscopy (XPS). The core level XPS spectra show that a steady-state composition is attained at a total irradiation dose of 10/sup 17/ particles/cm/sup 2/ in which the damaged layer contains predominantly M/sub 2/O and M/sub 2/O/sub 2/ with smaller amounts of MNO/sub 3/ and MNO/sub 2/, where M = Li and Na. Irradiation of NH/sub 4/NO/sub 3/ produces no changes detectable by XPS, suggesting that the decomposition products are all volatile. While the relative atomic concentrations of the constituent elements within the damaged layer change in a similar manner for the three modes of radiation, i.e. there is an increase in alkali metal, decrease in nitrogen, and only minor changes in oxygen concentration, the specific products and relative abundances of these products differ. Consideration of these results in terms of the mechanisms of energy deposition into the atomic lattice indicates that the energy density deposited by all three sources exceeds that required for decomposition and that the excess energy determines the extent of reaction. 31 references, 5 figures, 1 table.