In Situ High-Resolution FT-IR Study of the Orientational Phase Transition in C60 Film

Abstract

We have studied the orientational phase transition of a water-free C{sub 60} film by examining the temperature dependence of line shift, half-width, and integrated absorbance of the four fundamental IR-active modes in the C{sub 60} film with high-resolution (0.25 cm{sup -1}) Fourier transform infrared (FT-IR) spectroscopy. A discontinuous line shift of the IR-active mode at 576 cm{sup -1} is observed at about 257 K for the first time. This temperature is consistent with the previous results that the orientational phase transition of C{sub 60} bulk structure occurs at 250-262 K. In addition the temperature dependence of the line shift for the IR-active mode at 526 cm{sup -1} is the opposite of those for the other modes. The reason for this difference can be explained qualitatively on the basis of the relation between the intermolecular interaction and the motion of atoms for each IR mode. 27 refs., 7 figs.