SURFACE DYNAMICS OF THE CYCLOHEXADIENYL RADICAL ADSORBED ON SILICA-GEL INVESTIGATED USING AVOIDED LEVEL-CROSSING MUON SPIN-RESONANCE

The dynamic behaviour of the cyclohexadienyl radical on a silica surfa ce has been investigated using the avoided level-crossing muon spin re sonance technique. Translational motion of the radical on a curved sur face leads to partial averaging of the muon-electron hyperfine anisotr opy and thus to motional narrowing of the experimental signal. A theor etical model based on a stochastic Liouville formalism allows interpre tation of the data in terms of radical diffusion. Arrhenius behaviour with an activation energy of (10.8 +/- 0.9) kJ/mol is observed. Specif ic deviations between theoretical predictions and experimental results indicate that the potential of this technique is not yet fully exploi ted and that the model can be further refined.