PHONON SELF-ENERGIES AND 4F-ELECTRON-PHONON INTERACTION IN CECLA1-CF3

In CecLa1-cF3 we have observed frequency shifts of optical phonons depending on the concentration c of the 4f ions and on temperature. It is shown that these effects are due to a resonant 4f-electron-phonon interaction via photon-induced virtual quadrupole transitions to excited crystal-field states of Ce3+. These shifts are related to the magnetic phonon splitting of doubly degenerate phonons. Both effects can be quantitatively interpreted with the same coupling constant. © 1979 The American Physical Society.