Spectroscopy of zigzag single-walled carbon nanotubes: Comparing femtosecond transient absorption spectra with ab initio calculations

Femtosecond transient absorption spectroscopy was applied to map out the electronic transition energies of a selected semiconducting zigzag carbon nanotube, the (11,0) tube. The experiment was performed by resonant excitation of the lowest electronic transition with spectrally narrow pump pulses, ensuring predominant selection of the desired tube type from a mixture of various species. We found that the lowest and the second electronic transitions are characterized by induced transmission bands peaking at 1042 and 741 nm, respectively. The association of the resolved spectral bands to the two lowest electronic transitions of the (11,0) tube was further verified by examining the corresponding kinetic profiles. Results of ab initio calculations are also presented for comparing the transition energies and for explaining the transient absorption kinetics detected at different wavelengths.