The formation and disappearance of 0(center dot-) in oxygen-free aqueous solution at pH 13 has been studied and its spectrum has been redetermined utilizing pulse radiolysis optical measurements in the UV region. The rate constant for the reaction H-center dot + OH- is determined to be 2.5 x 10(7) dm(3) Mol(-1) s(-1). A determination of the rate constants for the equilibrium (OH)-O-center dot + OH- double left right arrow 0(center dot-) was not possible; the pK value for this equilibrium was determined to be 11.9. The rate constant for the demerisation 0(center dot-) + 0(center dot-) was measured at 325 nm to be 2k = 2 x 10(9) dm(3) Mol(-1) s(-1). The absorption spectrum of Ocenter dot- differs significantly from that in the literature below 250 nm. (c) 2005 Elsevier B.V. All rights reserved.