Figure 5.

4.2-K Mössbauer spectra of the product of reaction of free Mn^IV/Fe^III–β₂ and HU recorded in external magnetic fields of 4T (top) and 8T (bottom) applied parallel to the γ-beam. 3.0 mM β (0.75 equiv Mn^IV/Fe^III) was incubated with 60 mM HU at ambient temperature for 25 min before freezing. The contribution of Mn^IV/Fe^III-β₂ (57% intensity), the diamagnetic Fe^III-containing cluster (33% intensity), and the mononuclear high-spin Fe^III impurity (10% intensity) are shown as blue, red, and green lines, respectively. Simulation parameters are: S = 5/2, D = −0.38 cm⁻¹, E/D = 0.31, g = (2.0, 2.0, 2.0), ΔE_Q = 0.56 mm/s, δ = 0.46 mm/s, a_Fe/g_Nβ_N = (−22, −22, −22) T, η = −0.19 (green lines); S = 0, ΔE_Q = −0.88 mm/s, δ = 0.49 mm/s, η = −0.43 (red lines); S = 1, D = −1.9 cm⁻¹, E/D = 0.33, g = (2.0, 2.0, 2.0), ΔE_Q = −1.38 mm/s, δ = 0.52 mm/s, A_Fe/g_Nβ_N = (−39.0, −39.2, −37.6) T, η = −0.23 (blue lines). The black lines overlaid with the experimental spectra are the summations of the three components.