Portrait of diatomic FeN. A theoretical study

The ground and low-lying excited states of the diatomic molecule FeN were systematically studied. For this purpose a density functional/Hartree-Fock hybrid method and the internally contracted averaged quadratic coupled cluster approach with large basis sets were used. In agreement with previous reports the calculations revealed the 2Δ state to be the lowest in energy and only 3 kcal/mol higher lies the 4∏ state. In addition, we found another very low-lying 4ф state and an even less energy demanding state of 6∑+ symmetry. The computations showed excitation energies of 5 and 0.5 kcal/mol, respectively. If the uncertainties of the methods are considered, all four states are good candidates for the real ground state.