There exist literature controversy concerning Raman scattering mechanism from carbon nanotubes. Namely, in the same nanotube the E2g peak in the Y(XX)Y configuration can be stronger than the A1 peak in the Y(ZZ)Y configuration, what is in disagreement with the depolarization effect.1 In order to study this issue a detailed polarization dependent resonant Raman spectra from spatially isolated semiconducting single-, double- and multiwalled carbon nanotubes were measured and analysed. Angular variation of intensities for RBM, oTO, IFM, D, G, M and G' bands - in the case of SWNT and for RBM, G and G' band - in the case of DWNT and MWNT was analyzed. All intensities follow the function which is square product of cos(φ)cos(θ), where φ and θ are the angles between incident and scattered light polarizations, and the nanotube axis, respectively. Such polarization dependence of Raman spectra implies a diagonal Raman tensor. Weak quantitative changes in the G bands were observed, what suggests different subbands transitions Eμv→Eμ'c. On the above basis we suggest a presence of a Raman scattering mechanism, that could lead to the diagonal Raman scattering matrix. Possible explanation of these effects is discussed.
1"Advances in single nanotube spectroscopy: Raman spectra from cross-polarized light and chirality dependence of Raman frequencies", A. Jorio et al. Carbon 42 (2004) 1067-1069