%0 Journal Article
%A Blackburn, Jeffrey L.
%A Holt, Josh M.
%A Irurzun, Veronica
M.
%A Resasco, Daniel E.
%A Rumbles, Garry
%D 2016
%T Confirmation of K-Momentum
Dark Exciton Vibronic Sidebands
Using 13C-labeled, Highly Enriched (6,5) Single-walled
Carbon Nanotubes
%U https://acs.figshare.com/articles/journal_contribution/Confirmation_of_K_Momentum_Dark_Exciton_Vibronic_Sidebands_Using_sup_13_sup_C_labeled_Highly_Enriched_6_5_Single_walled_Carbon_Nanotubes/2540818
%R 10.1021/nl204072x.s001
%2 https://acs.figshare.com/ndownloader/files/4183831
%K vibronic sidebands
%K nonradiative recombination processes
%K 1 E 11 singlet exciton
%K singlet exciton
%K SWCNT
%K meV
%K emissive vibronic transitions
%X A detailed knowledge of the manifold of both bright and
dark excitons
in single-walled carbon nanotubes (SWCNTs) is critical to understanding
radiative and nonradiative recombination processes. Exciton–phonon
coupling opens up additional absorption and emission channels, some
of which may “brighten” the sidebands of optically forbidden
(dark) excitonic transitions in optical spectra. In this report, we
compare 12C and 13C-labeled SWCNTs that are
highly enriched in the (6,5) species to identify both absorptive and
emissive vibronic transitions. We find two vibronic sidebands near
the bright 1E11 singlet exciton, one absorptive
sideband ∼200 meV above, and one emissive sideband ∼140
meV below, the bright singlet exciton. Both sidebands demonstrate
a ∼50 cm–1 isotope-induced shift, which is
commensurate with exciton–phonon coupling involving phonons
of A1′ symmetry (D band, ω ∼
1330 cm–1). Independent analysis of each sideband
indicates that both sidebands arise from the same dark exciton level,
which lies at an energy approximately 25 meV above the bright singlet
exciton. Our observations support the recent prediction of, and mounting
experimental evidence for, the dark K-momentum singlet exciton lying
∼25 meV (for the (6,5) SWCNT) above the bright Γ-momentum
singlet. This study represents the first use of 13C-labeled
SWCNTs highly enriched in a single nanotube species to unequivocally
confirm these sidebands as vibronic sidebands of the dark K-momentum
singlet exciton.
%I ACS Publications