Spectral-line-broadening study of the trivalent lanthanide-ion series .1. Line broadening as a probe of the electron-phonon coupling strength

Line broadening is evaluated as a method to probe an electron-phonon coupling strength of lanthanide ions. Various problems which complicate the analysis of line broadening, like a contribution of different relaxation processes and the difference in behavior for different transitions in the same system are discussed, using LiYF4:Eu3+ and LiYF4:Pr3+ as examples. The results show that the electron-phonon coupling parameter <(alpha)over bar>, derived from a fit to the Raman two-phonon process for different transitions, provides a good estimate of an electron-phonon coupling strength. In a second paper this line broadening method is used to probe the variation of the electron-phonon coupling strength through the trivalent lanthanide ion series.