One-Dimensional Character of Combination Modes in the Resonance Raman Scattering of Carbon Nanotubes

Resonance Raman spectroscopy with an energy tunable system is used to analyze the $600–1100{\mathrm{c}\mathrm{m}}^{-1}$ spectral region in single-wall carbon nanotubes. Sharp peaks are associated with the combination of zone folded optic and acoustic branches from 2D graphite. These combination modes exhibit a peculiar dependence on the excitation laser energy that is explained on the basis of a highly selective resonance process that considers phonons and electrons in low dimensional materials.