For very short mixing times, the propagator e Kτm reduces to the identity operator, and no exchange cross-peaks are expected. However, when such an experiment was acquired for DMTCA (with a near-zero 20 µs mixing time), cross-peaks were unexpectedly observed at frequencies (ω A , ω B ) and (ω B , ω A ), with intensities ca. 5% that of the diagonal peaks (Fig. ). In contrast to the diagonal peaks, the cross-peaks were not absorption mode, but had a partially dispersive lineshape. When a non-zero mixing time was used, stronger cross-peaks were observed, as expected from the exchange of z magnetization, although a partially dispersive character could again be discerned (3 ms, Fig. ).