Intrinsic Optical Transition Energies in Carbon Nanotubes

Intrinsic optical transition energies for isolated and individual single wall carbon nanotubes grown over trenches are measured using tunable resonant Raman scattering. Previously measured E22_S optical transitions from nanotubes in surfactants are blue shifted 70-90 meV with respect to our measurements of nanotubes in air. This large shift in the exciton energy is attributed to a larger change of the exciton binding energy than the band-gap renormalization as the surrounding dielectric constant increases.