Davydov splitting of crystal-field excitations and magnetic phonon splitting inPrF3

The lowest multiplet component ${}_{}{}^3{}_{}{}^{}\mathrm{H}_4^{}{}_{}{}^{}$ of 4${\mathrm{f}}^2$ in ${\mathrm{PrF}}_3$ has been investigated spectroscopically. An interaction between the ${\mathrm{Pr}}^{3+}$ ions exists, which results in a Davydov splitting of electronic excitations. The system of optical phonons also displays anomalous behavior: Magnetic phonon splitting of an ${\mathrm{E}}_{\mathrm{g}}$ mode and a temperature-dependent frequency renormalization of another mode have been observed. The electronic and the lattice effects can be interpreted simultaneously on the assumption of a 4f-electron–phonon interaction of the Jahn-Teller type as the prevailing interaction mechanism.