Radiation mechanisms—XI

Abstract

Exposure of aqueous glasses containing carbonate enriched in ¹³CO₃²⁻ gave ^.OH and e_t⁻ as major primary products at 77 K, but ^.CO₂⁻ and CȮ₃⁻ features together with ¹³C satellite lines grew strongly on annealing above 77 K. Alkaline solutions gave mainly ^.O⁻ and e_t⁻, but on annealing a new radical, tentatively identified as CȮ₄³⁻, was detected. This had E.S.R. parameters comparable with those for ¹³CȮ₃⁻, but with a smaller anisotropy in both A(¹³C) and g. This species is thought to result from addition of ^.O⁻ to CO₃²⁻

Solutions is methanol (CD₃OD) gave mainly D₂ĊOD, e_t⁻, and ^.CO₂³⁻ radicals, but CȮ₃⁻ grew in strongly on annealing.

Neutral aqueous glasses containing formate ions gave HĊO and ĊO₂⁻ in addition to ^.OH radicals, together with a broad feature tentatively assigned to HĊO₂²⁻ or HĊO(OH)⁻ radical. These features were better defined in alkali glasses (HĊO₂²⁻) and in 6 mol dm⁻³ sulphuric acid glasses [HĊO(OH)⁻]. Features for ¹³CO₂⁻ were clearly resolved in the former, but in the acidic glasses a larger ¹³C hyperfine coupling suggested ¹³ĊO(OH). The formly radical was also detected in the scidic glasses but not in the alkaline media. The mechanisms of the reactions leading to these intermediates are discussed and compared with those for aqueous nitrite solutions.