Femtosecond luminescence decay due to exciton energy transfer in single-walled carbon nanotube bundles

We investigated luminescence decay kinetics in single-walled carbon nanotubes in large bundles excited by femtosecond pulses. The time constant of luminescence decay becomes longer with decrease in photon energy: 40 fs at 1.2 eV and 380 fs at 0.6 eV. This behavior is explained by exciton energy transfer from an excited to neighboring tubes.