Probing the molecular orbitals of FePc near the chemical potential using electron energy-loss spectroscopy

We have studied the electronic structure of iron phthalocyanine (FePc) films at low temperature using electron energy-loss spectroscopy. The electronic excitation spectrum of FePc is rather complex and comprises both pi-pi(*) transitions of the phthalocyanine ligand and transitions that involve the Fe 3d orbitals. The C 1s core excitations provide so far unidentified information on the molecular orbitals. They demonstrate that the Fe 3d orbital with e(g) symmetry is energetically located in between the highest occupied and the lowest unoccupied ligand state and that it is not fully occupied.