In an attempt to understand this dispersive shape of the DNP field profile, we initially performed simulations using SpinEvolution . The results are presented in Figure for a system consisting of a single S = 1/2 electron spin interacting with a single I = 1/2 nuclear spin. In the absence of relaxation, we observe a weak dispersive DNP enhancement at the EPR resonance. As the simulation involves a single electron spin and hence no electron-electron interactions, this enhancement cannot be ascribed to the CE or TM. In addition, there is no cross relaxation, thus it cannot be due to the OE. Finally, this cannot be the SE, which is observed at ω0S ± ω0I.