Hyperfine interactions at 57Fe in octaethylhaemin

Mössbauer measurements on octaethylhaemin have been made between 4.2 and 300 K, and (at the lower temperature) in applied magnetic fields of up to 50 kG. From a spin hamiltonian treatment the saturation value of the hyperfine field at the ⁵⁷Fe nucleus is found to be 495 kG, and the splitting parameter for the ferric ion levels by the axial ligand field is D = 8.0 cm^?1. The electric field gradient 1/2e²qQ = +0.93 mm s^?1.