Hyperfine decoupling in electron paramagnetic resonance as a powerful tool for unraveling complicated ESEEM spectra of S=1/2, I> or =1/2 systems.

Hyperfine decoupling in electron paramagnetic resonance after strong microwave radiation is studied for S=1/2, I=1/2 and S=1/2, I=1 spin systems. A new 2D pulse sequence based on the hyperfine-decoupled DEFENCE (deadtime-free ESEEM by nuclear coherence-transfer echoes) experiment is introduced, which is distinguished by a remarkable reduction of the residual hyperfine coupling. The efficiency of this new decoupling experiment in comparison to the old pulse sequence is studied by means of numerical simulations. The advantages of the new decoupling experiment and its ability to simplify ESEEM spectra are experimentally demonstrated on two disordered systems.