Influence of geminate recombination kinetics on the shape of low field MARY line

The influence of diffusional kinetics of geminate recombination of radical ion pairs on the shape of MAgnetic field dependence of Reaction Yield (MARY) spectra in weak magnetic fields is analysed in some detail. It is shown that the low-field line is not Lorentzian and has broader wings and a sharper peak. The deviation from the Lorentzian shape is most clear when the times of spin relaxation and chemical transformation of radical ions are much longer than the characteristic time scale of the geminate recombination. Under this condition, the full width at half magnitude is related primarily to the recombination time, whereas the width between the points of maximum slopes is determined by spin relaxation and chemical decay. The low-field MARY line was analysed for the pairs (n-alkane)(+)/C6F6-. It was found that the line shape is indeed not Lorentzian, and is well described by the suggested theory. (C) 2000 Elsevier Science B.V. All rights reserved.