The effects of weak magnetic fields on radical recombination reactions in micelles

Purpose: To demonstrate the effects of weak magnetic fields ( > similar to 1 mT) on chemical reactions involving free radicals, in the context of poss ible effects of environmental electromagnetic radiation on biological syste ms. Materials and methods: Transient absorption, flash photolysis experiments h ave been performed to study the kinetics and yields of radical reactions. T he triplet state of benzophenone has been used as a convenient source of ra dical pairs, whose identity is largely immaterial to the investigation of t he so-called Low Field Effect. Hydrogen abstraction from surfactant molecul es in micelles yields a pair of neutral radicals, one large and one small, in a region of restricted translational and rotational motion. Results: In alkyl sulphate and sulphonate micelles a weak field increases t he concentration of free radicals that escape from the micelle to an extent that depends on the structure, dynamics and volume of the space in which t he radical pairs are confined. The effect (up to 10%) is typically largest at 1-2 mT. Smaller effects are found for Brij and TX100 micelles. Conclusions: Low Field Effects depend strongly on the local environment of the radical pair. Larger effects than observed here might be expected for r adicals formed from singlet (rather than triplet) precursors, as would be t he case in biological reactions.