A simple model for $f\to d$ transition of heavy lanthanide and actinide ions in crystals

TL;DR

This paper extends an existing $f\to d$ transition model to accurately interpret spectra of heavy lanthanide and actinide ions in crystals, where spin-orbit interactions are significant.

Contribution

The model is modified to account for strong spin-orbit coupling in heavy lanthanides and actinides, broadening its applicability.

Findings

Extended model successfully describes $f\to d$ transitions in heavy ions.

Improved interpretation of absorption and emission spectra.

Enhanced understanding of nonradiative relaxation processes.

Abstract

The $f\to d$ transition model by Duan and co-workers [Phys. Rev. B {\bf 66}, 155108 (2002); J. Solid State Chem. {\bf 171}, 299 (2003)] has been very useful in interpreting the $f\to d$ absorption, emission and nonradiative relaxation of light lanthanide ions in crystals. However, based on the assumption that the $f^{N-1}$ core spin-orbit interaction is weak compared to $f\to d$ exchange interaction, this model, in the original form, is not applicable to interpretation of the $f\to d$ transitions of heavy lanthanide ions or actinide ions in crystals. In this work the model is extended to cover the cases of heavy lanthanides and actinides, where the spin-orbit interaction of $f$ orbitals may be stronger than the $f-d$ exchange nteraction. Keywords: lanthanide; f-d transition; model; spectrum; actinide; VUV;