Possibility of formation of rare-earth negative ions by attachment of f electrons to the atomic ground state

Some recent experiments indicate that certain rare-earth negative ions exist. Some local-density calculations indicate that attachment of f electrons is most favorable for Tm and Md. Here we investigate by means of relativistic configuration-interaction methods whether Tm- 4f14 and Md- 5f14 are bound. Our results strongly suggest that they are not, and that a different attachment process (perhaps that of a p electron, as recently proposed by Vosko and Chevary [Bull. Am. Phys. Soc. 37, 1089 (1992)]) must be contemplated. © 1993 The American Physical Society