SCF CI calculations of the K-shell ionization potential of carbon in methane and in the fluoromethanes

The vertical ionization potentials of the K-shell of carbon have been calculated in CH₄, CH₃F, CH₂F₂, CHF₃ and CF₄. The ab initio SCF CI approach has been used for the first three compounds with an attempt to rationalize the choice of the atomic orbital basis sets. The ionization potentials of CHF₃ and CF₄ have been extrapolated from the proceeding results. The effect of the CI cannot be neglected in either of these compounds, but it can in CH₄.