• iron mononitride;
  • spectroscopic constants;
  • multireference;
  • complete active space self-consistent field


Low-lying states of iron mononitride are studied using ab initio multireference singles and doubles configuration interaction (MR-SDCI) calculations. For each one of the 2Δ, 4Π, 6Σ+, 2Π, 4Δ, 6Π, and 6Δ states the reference wavefunction has been obtained at the complete active space self consistent field (CASSCF) level and relativistic corrections were included. Potential energy curves are presented for all states. Spectroscopic constants have been determined for the 2Δ, 4Π, and 6Σ+ states assuming a Morse-type potential function using a code written by one of us. For the 2Δ state, the calculated spectroscopic constants are Re = 1.567 Å, ωe = 827 cm−1, and μ = 1.68 D. Rotovibrational analysis suggests that the third vibrational level of the 2Δ state already surpasses the first vibrational levels of the 4Π and 6Σ+ states, what reassures the difficulty in correctly attributing the lines of the experimental spectrum. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010