Abstract
The electronic spectra of rare-earth ions in crystalline fields are generally analyzed in terms of a static crystalline field, , which acts on the open shell of electrons. In this paper, the contributions of the closed atomic shells to this electrostatic interaction are examined and are found to be significant in several respects: First, the magnitude of the crystal-field splittings are reduced from the values obtained by considering just the shell alone; this result supports the familiar assertion that the electrons are shielded from the external crystalline field. Secondly, and quite striking, is the result that the ordering and relative spacing of the crystal-field levels are not necessarily those implied by the crystal-field matrix elements alone. It is shown that in some cases the distortion of the ion's charge distribution produces severe deviations from the crystal-field level scheme predicted by directly. When such "nonlinear" deviations occur, they make questionable the standard crystal field parametrization schemes used for fitting observed rare-earth spectra. In addition, we also investigate the role played by the crystal field in producing by means of the distortion of the closed and shells, and the interaction of these distortions with the open shell, contributions to the magnetic (and electric) hyperfine interactions.
- Received 26 August 1963
DOI:https://doi.org/10.1103/PhysRev.133.A1571
©1964 American Physical Society