EPR, ENDOR and optical spectroscopy of Yb3+ ion in KZnF3 single crystals

• The KZnF3:Yb3+ center was studied by EPR, ENDOR and optical spectroscopy.
• The distortions of the crystal lattice in the vicinity of Yb3+ were determined.
• The Yb3+–F− bond parameters were determined using new theoretical contributions.

The paramagnetic center of tetragonal symmetry formed by the Yb3+ ion in the KZnF3 crystal has been studied using methods of EPR, ENDOR and optical spectroscopy. The location of the impurity ion and the structural model of the complex differing from the model of the Yb3+ center in KMgF3 have been established. The empirical scheme of the energy levels of the Yb3+ ion has been found. The parameters of its interaction with the crystal electrostatic field and the hyperfine interaction with ligands of the nearest environment have been determined. The parameters of the crystal field were used for the analysis of the distortions of the crystal lattice in the vicinity of Yb3+. The parameters of the transferred hyperfine interaction have been calculated for the distances between Yb3+ and F− ions of the nearest environment obtained taking into account the found distortions. They are in good agreement with the experimental values.