Abstract

Transitions within the f^N configurations of rare-earth ions are parity forbidden and only became allowed by virtue of external perturbations. A general parametrization of the intensities of transitions between crystal-field levels requires a set of parameters $\left\{{\text{A}}_{\text{tp}}^{\lambda }\right\}(\lambda =2,4,6;\text{t}=\lambda -1,\lambda ,\lambda +1;\text{p}$ determined by symmetry).¹ However, if the 'superposition' approximation, that the rare-earth-ligand interactions are cylindrically symmetric and independent, is valid, the t=λ parameters are unnecessary and the parametrization reduces to the usual Judd-Ofelt parameter set {A_tp Ξ (t,λ)}.

© 1984 Optical Society of America