Crystal field splitting of highly excited electronic states of the 4fn–1 5d electronic configuration of trivalent rare earth ions in wide band gap crystals

The energy position and the spacing of the levels of the 4f^n–15d electronic configuration of the trivalent rare earth ion dopands in wide band gap fluoride crystal, depend on the symmetry and the type of the host matrix. Crystal field splitting of the 4f²5d electronic configuration of the Nd³⁺ ions in SrF₂ crystals have been observed in the VUV region of the spectrum. The absorption bands were due to the interconfigurational 4f³→4f²5d dipole allowed transitions between the ground state with 4f³ electronic configuration of the Nd³⁺ ions and the Stark components of the 4f²5d electronic configuration. The VUV spectra can be interpreted by applying the crystal field model, and taking into consideration both that lanthanide contraction of the 4f^n–15d electronic configuration of the rare earth ions is taking place, and that the contribution of the positively charged ions in the total electric field, is effectively decreased with increasing numbers of the electrons in the 4fⁿ electronic configuration due to effective charge shielding.