The low-lying electronic states and harmonic vibrational frequencies of FeC 2 and FeC 2−

Abstract

The multiplet states of FeC 2 and FeC 2 − are examined using ab initio molecular orbital theory at the HF/MIDI ∗ and CISD + Q levels. For FeC 2, the 7A 2 state in C 2 v triangle symmetry is found to have the lowest energy. For FeC 2 − the 6B 2 state in C 2 v triangle symmetry is the ground state, and the Koopman ionization potential is about 2.133 eV, and FeC symmetry stretching frequency is 498.2 cm −1. The most stable linear isomer takes the 4Δ( 4A 1) state, the Koopman ionization potential and FeC stretching frequency being 3.422 eV and 530.3 cm −1, respectively. Theoretical investigations on other low-lying states in C 2 v and C ∞ v symmetries have been carried out.