Excited states dynamics under high pressure in lanthanide-doped solids

Emission related to rare earth ions in solids takes place usually due to 4f n →4f n and 4f n−1 5d 1→4f n internal transitions. In the case of band to band excitation the effective energy transfer from the host to optically active impurity is required. Among other processes one of the possibilities is capturing of the electron at the excited state and the hole at the ground state of impurity. The latest results on high pressure investigations of luminescence related to Pr 3+ and Eu 2+ in different lattices are briefly reviewed. The influence of pressure on anomalous luminescence and 4f n−1 5d 1→4f n luminescence in BaSrF 2:Eu 2+ and LiBaF 3:Eu 2+ systems and Pr 3+ 4f n →4f n emission quenching is presented and discussed. A theoretical model describing the impurity-trapped exciton as a system where a hole is localized at the impurity and an electron is captured by Coulomb potential at Rydberg-like states is developed. The results show the importance of local lattice relaxation for the creation of stable impurity-trapped exciton states. The ligands shifts create a potential barrier that controls the effect of mixing between the Rydberg-like electron and localized electron wave functions.