Spectral-line-broadening study of the trivalent lanthanide-ion series.II. The variation of the electron-phonon coupling strength through the series

Abstract

The variation of an electron-phonon coupling strength of lanthanide ions is evaluated by measuring the temperature-dependent line broadening of a large number of 4f transitions of nine lanthanide ions. The results show that the electron-phonon coupling strength derived from these line-broadening experiments is large in the beginning (${\mathrm{Ce}}^{3+}$,${\mathrm{Pr}}^{3+}$,${\mathrm{Nd}}^{3+}$ ) and the end (${\mathrm{Er}}^{3+}$,${\mathrm{Tm}}^{3+}$,${\mathrm{Yb}}^{3+}$ ) of the trivalent lanthanide-ion series, but small at the center (${\mathrm{Eu}}^{3+}$,${\mathrm{Gd}}^{3+}$,${\mathrm{Tb}}^{3+}$ ). This trend can qualitatively be explained by the lanthanide contraction and the shielding of the 4f electrons.