Infrared active phonons in single-walled carbon nanotubes

We present IR reflectance spectra of samples containing single-walled carbon nanotubes and compare them with measurements made on graphite. Weak structures near the graphite modes but shifted towards higher frequencies were found. We assign these structures to IR-active phonons of single-walled nanotubes. Our experimental results suggest that while roughly in agreement with the experiment, further and more accurate calculations of the phonon frequencies of single-walled carbon nanotubes are necessary.