A simple model for crystal field splittings of the 7F1 and 5D1 energy levels of Eu3+

The crystal field splitting of the 7F1 energy level of Eu3+ ranges from 0 to 650 cm−1. The splitting can be described in good approximation by only the Bq2 parameters. The 5D1 energy level has a similar behavior, although the magnitude of the splitting is smaller due to a smaller reduced matrix element of rank 2. It is shown that small splittings of the 7F1 and 5D1 levels are not only found for systems which are close to cubic or icosahedral symmetry, but also for crystalline host matrices in which the coordination polyhedron around the Eu3+ ion is an ideal or distorted tricapped trigonal prism.