Calculation of optical constants from carbon nanotube transmission spectra

We want to clarify a few issues about using optical absorption spectra for characterizing carbon nanotubes. The common method of using optical density for nanotube counting is reasonable in the near-infrared and visible spectral region, but fails for the mid and far infrared, where metallic tubes can be unambigously detected. By performing Kramers-Kronig transformation on wide-range transmittance spectra of free-standing films, the far-infrared spectral region creates a unique possibility for estimating the amount of metallic tubes in different nanotube networks. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.