Electron-Phonon Coupling in Rare Earth Compounds

The variation in electron-phonon coupling strength for rare earth ions has been studied by measuring vibronic transition probabilities and temperature dependent line broadening for a large number of rare earth ions in different host lattices. The results show a large variation in the electron-phonon coupling strength (almost three orders of magnitude) and a remarkable trend: the coupling is strong for ions in the beginning and at the end of the lanthanide series and weak in the middle. In covalent host lattices the coupling is much stronger than in ionic host lattices. An explanation of the results is given and the consequences of the variation of the electron-phonon coupling strength on phenomena like multiphonon relaxation, energy transfer and cooperative luminescence are discussed.