  Resonant Raman spectroscopy of single carbon nanotubes suspended across
trenches displays red shifts of up to 30 meV of the electronic transition
energies as a function of the surrounding dielectric environment. We develop a
simple scaling relationship between the exciton binding energy and the external
dielectric function and thus quantify the effect of screening. Our results
imply that the underlying particle interaction energies change by hundreds of
meV.
