One-Electron Energies of Atoms, Molecules, and Solids

Abstract

In the method of the self-consistent field, the one-electron energies of the occupied orbitals agree closely with ionization energies of the corresponding atom or molecular system. To compare such calculations with experiment, we need a table of ionization energies of the atoms. Such a table is set up in the present paper. For the outer electrons, we use optical data, finding the energy of each configuration as the weighted mean of all the states in that configuration. For the inner electrons, we use x-ray data, and for this purpose present a revised table of x-ray term values. The two sets of values should not agree, for the zero of energy in optical spectra is that for an electron removed an infinite distance from the isolated atom, while in x-ray terms all energies are referred to the Fermi energy in the crystal. For the alkali metals, measurements of both types can be intercompared, and it is shown that for Li the Fermi level lies about 0.8 rydberg, below the zero of energy for the atom, for Na and K about 0.5, and for Rb about 0.4 rydberg. Using this information, appropriate corrections are applied for the other atoms, and a table of ionization energies of the atoms is constructed. The values in this table are compared with experimental information from soft x-ray spectra, and theoretical calculations of energy levels in atoms, molecules, and solids.