Separation of G+ and G- phonon population dynamics in semiconducting single- walled carbon nanotubes as a function of diameter and temperature

The paper presents time-resolved incoherent anti-Stokes Raman spectroscopy (TRIARS) measurements of the population dynamics of G-mode phonons in semiconducting single-walled carbon nanotubes (SWCNTs), in which the G(+) and G(-) dynamics are separated. The measurements were performed as a function of temperature over the full range 4-600 K, and at two laser excitation energies, 1.51 and 1.63 eV, which give TRIARS signals from SWCNTs in two different diameter distributions, 0.99 < d < 1.05 nm and 0.88 < d < 0.97 nm, respectively. The population lifetimes determined from the experiments were, to within experimental error, independent of mode type and diameter. In all cases the temperature dependence of the population lifetimes was well fitted by a model that assumes that two-phonon anharmonic decay is the dominant process and that the lower-energy daughter phonon has an energy of approximately 400 +/- 100 cm(-1).