Raman intensity mapping of single-walled carbon nanotubes

We report on the measurement of the Raman intensity of radial breathing modes of a relatively large diameter range of single-walled carbon nanotubes (SWNTs) by confocal Raman scattering. Statistical data analysis yielded an intensity distribution within the excitation width of the single laser line at 2.33 eV. These measurements were compared to recent nonorthogonal tight-binding calculations on the Raman intensity where a match could be found. The mapping allowed for accurate determination of optical transition energies of the nanotubes and their chirality. Higher E-33(M) and E-55(S) optical transitions of both metallic and semiconducting SWNTs could be recorded for which intensity calculations were extended to tube diameters up to 2.6 nm.