High pressure spectroscopy of rare earth ions doped crystals—new results

High pressure spectroscopy is considered as an effective tool for investigation of energetic structure of rare earth and transition metal ions in solids and interactions of localized electrons with lattice. In this contribution, the results of the investigations of the pressure dependence of the energy of 4fn−15d1–4fn interconfigurational transitions in Ce3+ and Pr3+ and intraconfigurational transitions in the Ti3+ and Cr3+ in selected crystals are summarized. The quantitative analysis of pressure-induced emission and absorption shifts has allowed to calculate the local compressibility and local Grüneisen parameter describing the impurity ion–ligands system. In all considered cases it has been found that local compressibility is about two times smaller than compressibility of the bulk crystal. The local Grüneisen parameter obtained from the spectroscopic data is also smaller than the bulk Grüneisen parameter. This fact has been related to pressure-induced confinement and increase the energy of electrons localized at the impurity at levels in the forbidden energy gap.