Rb₁C₆₀: linear polymer chains and dimers

The infrared- and Raman-active vibrational modes of C₆₀ were measured in the various structural states of Rb₁C₆₀. According to earlier studies, Rb₁C₆₀ has been an fcc structure at temperatures above approx. 100°C, a linear chain polymer orthorhombic structure when slowly cooled, and an as yet undetermined structure when very rapidly cooled ('quenched'). We show that the spectra obtained in the polymer state are consistent with each C₆₀ molecule having bonds to two diametrically opposite neighbors. In the quenched state, we find evidence for further symmetry breaking, implying a lower symmetry structure than the polymer state. The spectroscopic data of the quenched phase are shown to be consistent with Rb₂(C₆₀)₂, a dimerization of C₆₀.