Some Methods of Estimating the Successive Ionisation Potentials of any Element

On certain assumptions as to the quantum numbers of the normal orbits of the successive electrons captured by an atom, the successive ionisation potentials can be estimated by making use of the relations between terms of the same quantum number for different atoms of the same electronic structure. Formulae for several of the successive ionisation potentials are given, the form of the formulae being suggested by theoretical reasoning and numerical values of the constants determined from known spectra; the successive ionisation potentials of O, Fe and Ag, calculated from these formulae, are tabulated. It is pointed out how far different these ionisation potentials are from the X-ray excitation potential of the same orbit of a neutral atom.