Resonantly enhanced Raman scattering and high-order Raman spectra of single-walled carbon nanotubes

The Raman spectra of single-walled carbon nanotubes (SWNTs) produced by the catalytic decomposition of hydrocarbons have been measured in the range of $\text{100–7500\hspace{0.05em}}{\mathrm{cm}}^{\mathrm{-1}}.$ The tangential C–C stretching modes show an unusual resonant enhancement process that results from the one-dimensional quantum confinement of the electrons in the SWNT, and its intensity of the tangential C–C stretching mode is about 100 times as strong as that of highly oriented pyrolytic graphite. Because of the resonant enhancement, high-order Raman bands up to fifth order have been revealed and assigned to the corresponding fundamentals.