Nano-optics of carbon nanotubes: measurement of unperturbed optical transition energies

In this work we present resonant inelastic light scattering (Raman) studies of individual tubes suspended in air. Using high resolution micro-Raman spectroscopy with tunable filters for high throughput we have mapped the resonance Raman profiles for a series of individual SWNTs in the 2n+m = 22 and 29 families and found clear evidence of excitonic interactions from the Raman measurements. Individual suspended SWNTs are grown across etched trenches on a quartz substrate with the chemical vapor deposition technique. For a single suspended tube, the laser excitation energy is tuned to find the electronic resonance, indicated by an intensity maximum of the Raman radial breathing mode (RBM). The Stokes and anti-Stokes double-peaks are offset in energy as expected from incoming and outgoing light resonance with the electronic level. It is demonstrated that the double peaks in the resonance window are separated by the RBM phonon energy, determining the width of the resonance profile