Resonant Raman intensity of the totally symmetric phonons of single-walled carbon nanotubes

The resonant Raman intensity of the totally symmetric phonons of all single-walled carbon nanotubes in the radius range from 2.5Åto11.5Å was calculated within a symmetry-adapted nonorthogonal tight-binding model. The obtained intensity of these modes exhibits radius and chirality dependence. The simulated Raman spectra of samples of moderate-diameter tubes with a Gaussian diameter distribution show characteristic peaks at about 1540, 1570, and 1593cm−1 originating from LO phonons of metallic tubes, TO phonons of metallic and semiconducting tubes, and LO phonons of semiconducting tubes, respectively. This general behavior of the Raman spectra corresponds to that of the normally measured spectra.