Third order a b i n i t i o calculations of the ff transition amplitudes for ions across the lanthanide series

Abstract
The behavior of various contributions to the ff transition amplitude defined up to the third order in perturbation theory is analyzed. Main attention is paid to the third‐order contributions which are due to electron correlation inside the rare earth ion and arise from the static and dynamic models. The discussion is based on the numerical results of exact ab initio calculations performed for Pr+3, Nd+3, Eu+3, Gd+3, Tb+3, and Tm+3 ions.