Second-harmonic signal through the orientational phase transition in fullerene films

Optical second-harmonic generation from a ${\mathrm{C}}_{60}$ thin film was used to monitor the orientational phase transition. A jump in second-harmonic intensity was observed around 245 K. This observation is in good agreement with the results obtained from infrared and Raman spectroscopy from ${\mathrm{C}}_{60}$ films. The different response of ${\mathrm{C}}_{60}$ films in the two phases is analyzed and tentatively explained.