Abstract

Unperturbed optical transition energies for isolated and individual SWNTs are measured using tunable resonant Raman scattering. The results suggest Coulomb interactions from exciton binding are comparable to bandgap renormalization, and are 1ev ≈ band gap. Previously measured $E_{22}^s$ optical transitions from nanotubes in surfactants are blue shifted 70-90 meV with respect to our measurements of nanotubes in air. The difference is attributed to different scaling exponents with ε for the exciton binding energy E^XB and the bandgap renormalization E^BGR, with E^BGR>|E^XB|, consistent with current theoretical understanding.

© 2005 Optical Society of America