Radiation mechanisms. Part 12.—E.s.r. studies of electron capture by silver (I) ions, nitrate ions and their ion pairs and clusters in methyl cyanide

Abstract

Pure silver nitrate on exposure to ⁶⁰Co γ-rays at 77 K gave no Ag^° centre, the electron excess centre being NO^2–₃ ions complexed to one strongly coupled Ag⁺ ion. In very dilute solutions in methyl cyanide the individual cations and anions gave Ag^° and NO^2–₃, but as soon as ion pairs become significant components, NO₂ radicals were formed, together, we suggest, with AgO^–. Infrared and Raman studies confirm that the ion pairs have the structure Ag⁺ ONO^–₂. On increasing the concentration of silver nitrate, the vibrational spectra indicated cluster formation, and the major electron capture process resulted in the formation of Ag⁺₂ and, later, Ag³⁺₄. It is concluded that a very subtle balance exists for the preferred electron capture path and possible controlling factors are discussed.

The main electron loss centres were identified as Ag²⁺, possibly NO₃, and products from the solvent. Changes which occur on annealing above 77 K are described and discussed.