No abstract

For doped armchair carbon nanotubes, the free electrons in the conduction bands would cause the intraband single-particle and collective excitations. Both kinds of excitations would be split into two modes because of two different Fermi-momentum states (kF'S). The excited carriers might be deexcited through such Coulomb excitations. Regarding the case where the transferred momentum L = 0, the two single-particle and the lower-frequency collective excitation modes could be the efficient deexcitation channels. In the lowest bands, the decay rates of the electron states exhibit weak Fermi energy (E(F)) dependence, but the decay rates of the hole states become greater with the increase of E(F) except for the right-side k(F). Concerning the states in the higher bands, the L not equal 0 excitations also take part in the deexcitation processes. Both the electron and hole states have the same decay rates except for the case where the carriers decay to the lowest states. The decay rates contrast sharply with those of undoped carbon nanotubes and two-dimensional intercalated graphenes. It is domenated by the Fermi energy, the geometric structure and the dimensionalities. The femtosecond time-resolved photoelectron, transmission and fluorescence spectroscopies could be used to verify the predicted results.