The interpretation of the AAF FID data is simple: the spectrum is modelled excellently by four almost equivalent proton hyperfines of ca. 10 MHz. The slight asymmetry of the spectrum relative to its barycentre is most easily quantified by a slightly anisotropic 𝐠-tensor (table ). However, the FID spectrum of FAAF is now clearly distinct from AAF. The triplet component appears as the broad shoulders to either side of the central doublet component which is otherwise akin to AAF. Similarly to cwESR, the weighting of the doublet is dominant (85% in this particular case). Yet, as for the cwESR data, the doublet weighting is not consistently the same between different samples. Nonetheless, all other simulation parameters remain reproducible. Particularly comforting is the fact that the halving of the triplet hyperfine couplings observed in the cwESR data is also reproduced in the FID data.