Spectroscopic analysis of different types of single-wall carbon nanotubes

The Raman response of the radial breathing mode in single-wall carbon nanotubes was analyzed for excitation with 10 different laser lines. The line shape was fitted with 14 Voigtian oscillators which could be correlated to tubes of different helicity. The strongest lines were observed between 172 and $\rm 199\; cm^{-1}$. For an assignment frequencies evaluated from a density functional calculation and scattering intensities for the resonance transitions were used. The 5 strongest lines observed are consistent with scattering from tubes with 11 different helicities. From the evaluation of the scattering intensities the nearest-neighbor integral between two carbon atoms on the curved sheet was found to be $2.6 \pm 0.5\;{\rm eV}$