Third-order analysis of rotatory strengths of f ↔ f transitions in chiral lanthanide systems

Abstract

The general expression for the rotatory strength of f ↔ f transitions in chiral lanthanide systems is presented. The approach is based on double perturbation theory, and the transition amplitude is defined within the static and dynamic models of central ion-ligand interactions. In order to include the perturbing influence of all single excitations from the 4f shell to one-electron states of given symmetry, the effective operators which contribute to the rotatory strength are expressed in terms of perturbed functions. In addition to the third-order electron correlation effective operators which have been already introduced into the theory of one- and two-photon processes in rare earth ions, new terms arising from the perturbing influence of the inter-space part of the even-rank crystal field potential are presented. The results of test ab initio calculations performed for Na₃[Eu-(oxydiacetate)₃].2NaClO₄.6H₂O are analysed in order to establish the relative importance of new effective operators in the theoretical description of chiroptical properties of lanthanide systems.