Infrared-ActiveVibrational Modes of Single-Walled Carbon Nanotubes†

We believe we have observed the IR-active vibrational modes of single-walled carbon nanotubes (SWNTs) for the first time. They were observed by optical transmission through thin films of bundled nanotubes. Because IR-active chemical functional groups, e.g., -COOH,-OH, might also be attached to the tube walls and contribute additional spectral features, we have also studied the effects of chemical purification and long-term high-temperature vacuum annealing on the IR spectrum. Through comparison with theory, we are able to assign much of the sharp stucture observed in our SWNT IR spectra. {\dag}This work was supported, in part, by the NSF NIRT program (DMR- 0304178).