case, the CE is attenuated because it requires pairs of electron spins, such that their EPR Larmor frequencies, ω0S/2π differ by the NMR frequency. Furthermore, TM is present when the EPR spectrum is strongly homogeneously broadened, for example, when the PA is small, so the interaction between pairs is large, and the nuclear Larmor frequency low. Finally, when the zero quantum (ZQ) and double quantum (DQ) cross relaxation rates are different, the Overhauser effect yields a symmetric Zeeman profile centered about the electron Larmor frequency .