Spectral-line-broadening study of the trivalent lanthanide-ion series.I. 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 ${\mathrm{LiYF}}_{4}$ :${\mathrm{Eu}}^{3+}$ and ${\mathrm{LiYF}}_{4}$ :${\mathrm{Pr}}^{3+}$ as examples.mThe results show that the electron-phonon coupling parameter \ensuremath{\alpha}-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.