Isotropic Proton Hyperfine Interaction in the Methyl Radical

Abstract

The isotropic hyperfine interactions of radicals or ions have been discussed from the viewpoint of the self‐consistent field (SCF) molecular orbital theory. In these phenomena, the most important electron configurations concerned are those arising due to the one electron excitations from the double occupied orbital to the vacant orbital together with the lowest energy configuration. The proton hyperfine splitting of the methyl radical was calculated nonempirically by using the SCF‐LCAO‐MOs in adopting the first order perturbation. The agreement with the observed value is quite good when one uses MOs that include the 3s AO of carbon atom, while it is not so satisfactory in the case of the MOs without the 3s AO, because of the improvement of the form of the totally symmetric antibonding vacant orbital which gives the main contribution to the phenomena.