Inter-multiplet transitions in the Fe4 magnetic cluster

We present the results of neutron spectroscopy for the tetranuclear iron(III) cluster of formula Fe4(OCH3)6(dpm)6, having an S=5 spin ground-state. At T=16.3 K two peaks appear at 7.3 and 8.3 meV . They have been attributed to the inter-multiplet transitions between the ground state and the first two excited S=4 multiplets. The experimental data, which have been interpreted in the framework of a microscopic model Hamiltonian, show that an exact C3 magnetic symmetry is not adequate to describe this system. The Q-dependence of the cross section is well reproduced by this model.