Theoretical Electron Affinities for Some of the Alkali and Alkaline-Earth Elements

The (ns)² correlation energies for the negative ions Li^-, Na^-, and K^- have been calculated by the method of superposition of configurations. Comparisons with Hartree-Fock calculations of the neutral species yield electron affinities of 0.62, 0.54, and 0.47 eV, respectively. A study of the computed ionization potentials of the neighboring isoelectronic atoms and ions suggests a maximum uncertainty of 0.1 eV. Similar calculations of the ns(np)²⁴P states of Be^- and Mg^- indicate that they are metastable, with electron affinities, relative to the nsnp³P state of the neutral atom, of 0.24 and 0.32 eV, respectively.