We study excitation energy and charge transfer in small aggregates of chirality enriched carbon nanotubes by transient
absorption spectroscopy. Ground state photobleaching is used to monitor exciton population dynamics with sub-10 fs
time resolution. Upon resonant excitation of the first exciton transition in (6,5) tubes, we find evidence for energy
transfer to (7,5) tubes within our time resolution (< 10 fs). After pumping at high pump energies, free charge carriers are
produced via exciton scattering into the underlying continuum bands. We obtain clearly distinguished photoinduced
features in the visible spectral range, that allow for real-time tracing of charge carrier dynamics in carbon nanotubes on a
sub-picosecond time scale.
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.