Statistical Atom: Ionization Energies
نویسنده
چکیده
A novel expansion of the Thomas-Fermi potential for a weakly ionized atom is presented. It is employed in calculating the ionization energies of neutral atoms as they are predicted by an extended version of the Thomas-Fermi model which includes the exchange energy and the leading quantum correction. The ionization energy, I, can be split into a smooth part, /stat, that is here obtained by the statistical treatment, and an oscillatory part, /0Sf, which represents significant shell effects. The experimental ionization energies of alkaline atoms are well reproduced by /stat, which approaches the constant of 3.15 eV when the atomic number, Z, gets large. It is observed that the amplitude of /^ is proportional to Z _1/3, so that shell effects are small compared to the smooth part of I (Z) if Z is sufficiently large (this situation occurs for Z 103, far beyond the Periodic Table). The study of the systematics of / (Z ) leads to predictions for the ionization energies of astatine (Z = 85, 1 = 9.5 eV) and francium (Z = 87, / = 3.9 eV), for which reliable experimental results are not reported.
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