Raman studies of electron-phonon coupling in single walled carbon nanotubes

We present the results of Raman studies of the chirality dependence of electron-phonon coupling in carbon nanotubes. We demonstrate that a new parameter resulting from a tight binding derivation of the electron-phonon coupling is useful for analysing experimentally-determined radial breathing mode (RBM) intensities. We also provide a direct comparison of RBM intensities for 6 chiralities obtained with excitation of both the E₁₁ and E ₂₂ transitions. Analysis of the observed intensity trends in terms of this new parameter demonstrates that the trend to weaker intensities as one excites at resonance with higher lying transitions results from differences in excited-state decay rates. Finally, we quantitate the magnitude of the matrix elements through modelling of RBM fundamental and overtone Raman excitation profiles using a time-dependent Raman formalism. Results for 5 chiralities show coupling in general to be weak.