Figure 4.

Mössbauer spectra (red) and simulations (black) of ⁵⁷Fe-1–OAc crystals recorded in a magnetic field of 7 T parallel to the γ-ray direction at the temperatures listed on the figure. The simulations, which were performed in slow relaxation, are for two equivalent exchange-coupled S=5/2 Fe^III sites with δ = 0.52 mm/sec, ΔE_Q = −0.83 mm/s, η = 0.5, Γ = 0.35 mm/s, A(isotropic) = −20 T, ⊺ = 27 cm⁻¹.