UV absorption spectrum, formation and disappearance of the oxide radical ion O− in aqueous solution: A pulse radiolysis study

The formation and disappearance of O− in oxygen-free aqueous solution at pH 13 has been studied and its spectrum has been re-determined utilizing pulse radiolysis optical measurements in the UV region. The rate constant for the reaction H + OH− is determined to be 2.5 × 107 dm3 mol−1 s−1. A determination of the rate constants for the equilibrium OH + OH - ⇔ O - was not possible; the pK value for this equilibrium was determined to be 11.9. The rate constant for the demerisation O− + O− was measured at 325 nm to be 2k = 2 × 109 dm3 mol−1 s−1. The absorption spectrum of O− differs significantly from that in the literature below 250 nm.