Infrared and Raman Evidence for Dimers and Polymers in Rb1C60

TL;DR

This study uses infrared and Raman spectroscopy to investigate the structural states of Rb1C60, revealing evidence of dimers and polymers, and identifying a lower symmetry dimerized phase in quenched samples.

Contribution

It provides spectroscopic evidence for the existence of dimers and polymers in Rb1C60, and characterizes the structural differences between various cooling states.

Findings

Spectra indicate C60 molecules form bonds to two neighbors in the polymer state.

Quenched Rb1C60 shows symmetry breaking and possible dimerization.

Spectroscopic data support the presence of Rb2(C60)2 in the quenched phase.

Abstract

The infrared- and Raman-active vibrational modes of C60 were measured in the various structural states of Rb1C60. According to earlier studies, Rb1C60 has an $fcc$ structure at temperatures above ~100C, 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.