Ultrafast generation of fundamental and multiple-order phonon excitations in highly enriched (6,5) single-wall carbon nanotubes.

Using a macroscopic ensemble of highly enriched (6,5) single-wall carbon nanotubes, combined with high signal-to-noise ratio and time-dependent differential transmission spectroscopy, we have generated vibrational modes in an ultrawide spectral range (10-3000 cm(-1)). A total of 14 modes were clearly resolved and identified, including fundamental modes of A, E and E-2 symmetries and their combinational modes involving two and three phonons. Through comparison with continuous wave Raman spectra as well as calculations based on an extended tight-binding model, we were able to identify all the observed peaks and determine the frequencies of the individual and combined modes. We provide a full summary of phonon frequencies for (6,5) nanotubes that can serve as a basic reference with which to refine our understanding of nanotube phonon spectra as well as a testbed for new theoretical models.