Dynamic light scattering from acoustic modes in single-walled carbon nanotubes

We report here the computation and measurement of inelastic light scattering from acoustic vibrational modes in single-walled carbon nanotubes (SWNT's). The measurement was made possible by the preparation of a sample of oriented SWNT's, partially aligned by means of a magnetic field. Long-wavelength confined longitudinal acoustic modes are described by a shell model. Their interaction with light is described by a surface elasto-optic effect. From the dispersion relations of acoustic modes we obtain an estimate of the two-dimensional Young's modulus of the single curved graphenic plane forming the SWNT. The result is consistent with the reported SWNT elastic properties.