Using femtosecond pump probe spectroscopy with sub-20 fs resolution, we probe fundamental properties of the E11 exciton in (6,5) single walled carbon nanotubes, prepared by density gradient ultracentrifugation. From the initial photobleaching signal, measured faster than any relaxation process, we obtain the one-dimensional size of the excitonic wavefunction along the nanotube. Exciton decay is found pump-intensity dependent only at elevated pump intensities. Numerical modelling of decay kinetics yields an exciton diffusion coefficient of about 0.1 cm^2/s. Anisotropy measurements in highly purified samples show that there is virtually no depolarisation of the E11 bleach over 40 ps. A photoinduced absorption (PA) band, blueshifted against the E11 bleach, shows only weak anisotropy.

Date Published: 15 May 2008
PDF: 10 pages
Proc. SPIE 6999, Organic Optoelectronics and Photonics III, 699935 (15 May 2008);

Published in SPIE Proceedings Vol. 6999:
Organic Optoelectronics and Photonics III
Paul L. Heremans; Michele Muccini; Eric A. Meulenkamp, Editor(s)