Temperature-Dependent Raman Study of Gd@C₈₂

We present a Raman spectroscopy investigation of the vibrational properties of a rare-earth endohedral metallofullerene, Gd@C₈₂, at low temperatures. While lowering the temperature, the Raman spectra show a blueshift in the Gd-C and C-C vibrational modes which are attributed to both anharmonic and thermal expansion contributions in the fullerene cage. The experimental data are compared with the theories of the shift and broadening of the phonon lines, and respective anharmonic and temperature coefficients are evaluated. In addition, the force constant of the Gd-C₈₂ vibration is derived at various temperatures using a linear harmonic oscillator model. No change in the oxidation state of the ion is noted in the examined temperature range. (Graph Presented).