Electronic states of the FeF molecule. II. Ab initio calculations

Abstract

For pt.I see ibid., vol.11, no.13, p.2281 (1978). Ab initio SCF-CI calculations of the electronic states of iron monofluoride have been performed with the aim of elucidating the ultraviolet spectrum of this radical. The bonding is ionic and the valence orbitals preserve their atomic character in the molecule. The ground state is found to be an inverted ⁶ Delta state associated with the (3d_Fe⁶( sigma pi ² sigma ³) 4s sigma _Fe2p_F⁶( sigma ² pi ⁴)) configuration. An energy-level diagram is built up which includes all the valence sextet states up to 60000 cm^-1. It demonstrates the close resemblance of the electron structure of FeF to that of the Fe⁺ ion. The observed systems of FeF are shown to originate from 4s-4p transitions corresponding to raies ultimes of Fe⁺: the observed ⁶ Pi and ⁶ Phi states both belong to a single configuration, (3d_Fe⁶( sigma pi ² delta ³)4p pi _Fe 2p_F⁶( sigma ² pi ⁴)).