Lanthanide Ionization Energies and the Sub-Shell Break. Part 1. The Second Ionization Energies

摘要

By interpolating a 4f(q)6s -> 4f(q)7s transition within the sequence f(1) -> f(14) rather than between f(0) and f(14), revised second ionization energies of the lanthanides have been obtained. In the early part of the series, between cerium and samarium, the revisions are significantly higher than currently accepted values. The revised values have been used to calculate the energy variation for the conversion of Ln(g, 4f(q)6s(2)) to Ln(2+) (g, 4f(q)) across the series Ba -> Yb. The variation is smooth between lanthanum and ytterbium but the barium point at q 5 0 is displaced downwards by more than 0.3 eV, thereby representing a significant sub-shell break. A case is also made for a substantial change to the second ionization energy of lutetium, the revised value being 14.13 +/- 0.10 eV. (C) 2017 AIP Publishing LLC for the National Institute of Standards and Technology.