Whilst compelling, the arguments of the previous section rely on two leaps-of-faith. Firstly, one has to accept that the spectrum of FAAF is a superposition of a doublet and triplet component and secondly, one has to trust that the 30 parameter cwESR fitting results are unique. The first independent piece of evidence in support of the doublet-triplet admixture comes from the free induction decay (FID) spectra in figure and the associated simulation parameters in table . Whilst for cwESR, the difference between AAF and FAAF was clearest when examining the C-labelled spectra, the unlabelled species offer the best comparison of the FID spectra of frozen solutions. In frozen solutions, the significant anisotropy of the C hyperfine tensor masks the fine-structure of the triplet component of FAAF. The FID spectra of the C labelled species are shown in the SI, together with the results of hyperfine sub-level correlation spectroscopy which validates our claim about the significant anisotropy of the C coupling. Therefore, the remaining analysis will focus only on the unlabelled species. The simulation was achieved with a doublet/triplet weighting of 85%/15%. A summary of the simulation parameters is shown in table 2; full simulation scripts are in the SI. For the triplet component of FAAF the anisotropy of the dipolar interaction, i.e. the 𝐃-tensor, is responsible for the Pake pattern appearance of the dashed green spectrum in panel (b). The turning points on the left of the spectrum are labelled as 𝑍 -and 𝑋 𝑌 + (the corresponding labels on the right of the spectrum would be 𝑍 + and 𝑋 𝑌 -). The 𝑍 label represents resonance fields corresponding to molecules for which the 𝐷 𝑧 -axis of the 𝐃-tensor is parallel to the external magnetic field, whereas the 𝑋 𝑌 label refers to molecules with 𝐷 𝑧 perpendicular to the magnetic field. The superscripts, ±, correspond to the 𝑇 -→ 𝑇 0 and 𝑇 0 → 𝑇 + electron spin transitions, respectively.