Optical Spectrum of SO₃⁻; Radicals produced from the Photolysis of Dithionate Ions in Solution

Abstract

DURING a recent study¹ of the photochemistry of sulphite ions in aqueous solutions, an absorption spectrum with a maximum λ-275 mµ was observed in the flash photolysis of 10⁻² M Na₂SO₃ solutions in the presence or the absence of oxygen. This transient species, with an apparently low extinction coefficient, decays relatively slowly with a half-life of a few milliseconds. It was considered to be produced from the primary photoionization of sulphite ions and was tentatively assigned to the SO₃⁻ radical. A radical with a similar absorption spectrum, but longer lived, was also observed¹ in the flash photolysis of thiosulphate ions and, on the basis of kinetic evidence, was assigned to the S₂O₂⁻ radical. In order to provide further support for the species produced in the photolysis of SO₃²⁻ ions, we examined the flash photolysis of dithionate ions, S₂O₆²⁻.