Ce3+ and Pr3+5d-energy levels in the (pseudo) perovskites KMgF3 and NaMgF3

The location of the 5d-energy levels of Ce3+ and Pr3+ in the cubic perovskite KMgF3 and in the distorted perovskite NaMgF3 was determined from spectroscopic studies in the vacuum ultraviolet. It is established that Ce3+ and Pr3+ ions both occupy the same site in each host: K+ sites for KMgF3 and Na+ sites for NaMgF3. The small crystal field splitting and the small value of the centroid shift of the 4fn−15d-configuration yield a relatively high energy for the lowest 5d state of both Ce3+ and Pr3+. The lowest 5d state of Pr3+ in both hosts is found at energy higher than the 4f2 1S0 state, enabling the photon cascade emission to occur.