Intensities of the Raman-active modes in single and multiwall nanotubes - art. no. 041401

We investigated the phonon symmetries in the Raman spectra of single and mu ltiwall nanotubes. By using linearly and circularly polarized light we meas ured the Raman tensor invariants on unoriented carbon nanotubes, The ratio between the antisymmetric and the isotropic invariant shows that Raman scat tering in semiconducting single wall tubes is mainly due to fully symmetric A(1(g)) phonons with a strongly uniaxial Raman tensor. With the help of re cent experiments on aligned nanotubes we calculate the relative intensities for the high-energy modes of different symmetry. Compared to single wall t ubes the intensity of the E-1(g) and E-2(g) symmetry phonons in multiwall t ubes is 1.5 times stronger. The antisymmetric component of the resonant Ram an process was found to be zero in all measurements.