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Revealing new electronic behaviours in the Raman spectra of chirality‐enriched carbon nanotube ensembles
Author(s) -
Duque Juan G.,
Chen Hang,
Swan Anna K.,
Hároz Erik H.,
Kono Junichiro,
Tu Xiaomin,
Zheng Ming,
Doorn Stephen K.
Publication year - 2010
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201000350
Subject(s) - carbon nanotube , raman spectroscopy , asymmetry , raman scattering , excitation , spectral line , molecular physics , materials science , chirality (physics) , resonance (particle physics) , atomic physics , chemistry , nanotechnology , physics , chiral symmetry , optics , quantum mechanics , astronomy , quark , nambu–jona lasinio model
We present Raman spectroscopy of single‐walled carbon nanotubes (SWNTs) that are enriched in metallic species by density gradient ultracentrifugation (DGU) and enriched in single semiconducting chiralities through DNA‐based separations. Radial breathing mode (RBM) spectra demonstrate that DGU samples are highly enriched in armchair chiralities. The enrichment allows acquisition of pure G‐band spectra of the armchair SWNTs and reveals that the LO mode is absent in these structures. Raman excitation profiles for the G‐band in nearly pure (10,2) samples reveals a strong asymmetry in the intensities of the resonance coupling to incident and scattered photons. The experimental data may be fit using a four‐level molecular model for Raman scattering and the strong asymmetry can be understood as a consequence of the presence of non‐Condon effects. The result requires a reassessment of the assumption that the incident and scattered resonances are equivalent. The consequences of such non‐Condon effects on other SWNT electronic and optical processes will be an important topic for future study.