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R. Saito - One of the best experts on this subject based on the ideXlab platform.
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Excitonic Effects on Raman Intensity of Single Wall Carbon Nanotubes
e-Journal of Surface Science and Nanotechnology, 2010Co-Authors: K. Sato, Ahmad R. T. Nugraha, R. SaitoAbstract:The exciton-photon matrix elements, exciton-phonon matrix elements, and resonance Raman Intensity for radial breathing mode are calculated as a function of a dielectric constant κ which represents surrounding materials of single wall carbon nanotubes using the extended tight binding method. Since the exciton wave function in the real space becomes more delocalized with increasing κ, the exciton-photon matrix elements and resonance Raman Intensity for radial breathing mode decrease with increasing κ, while the exciton-phonon matrix elements are not so sensitive to the change of the exciton wave function. [DOI: 10.1380/ejssnt.2010.358]
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dependence of Raman spectra g band Intensity on metallicity of single wall carbon nanotubes
Physical Review B, 2007Co-Authors: Jin Sung Park, K. Sato, Hongzhang Geng, Kay Hyeok An, Cheolmin Yang, R. SaitoAbstract:We report the peculiar behavior of the ${G}^{\ensuremath{'}}$ band Raman Intensity, which is dependent on the metallicity of single-wall carbon nanotubes (SWCNTs). In the metallic SWCNTs, the ${G}^{\ensuremath{'}}$ band Intensity was enhanced relative to the $G$ band Intensity, while the ${G}^{\ensuremath{'}}$ band Intensity was suppressed in the semiconducting SWCNTs. Resonance Raman spectroscopy (using laser energies of ${E}_{\mathit{\text{laser}}}=2.41$, 1.96, 1.58, and $1.165\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$) showed these features on the metal-enriched and semiconducting-enriched SWCNT samples that had been selectively separated by the nitronium ions. The metallicity dependence was explained theoretically by calculating the resonance Raman Intensity within the extended tight-binding calculations. The calculated results confirm that the ${G}^{\ensuremath{'}}$ band Intensity of the metallic SWCNTs is stronger than that for the semiconducting SWCNTs because the electron-phonon matrix elements for the TO phonon at the $K$ point is larger for metallic SWCNTs and the resonance window for ${E}_{33}^{S}$ is larger than that for ${E}_{11}^{M}$.
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d band Raman Intensity of graphitic materials as a function of laser energy and crystallite size
Chemical Physics Letters, 2006Co-Authors: Kentaro Sato, R. Saito, A Jorio, Yutaka Oyama, J Jiang, Luiz Gustavo Cancado, M A Pimenta, Ge G Samsonidze, G Dresselhaus, M S DresselhausAbstract:Abstract The Raman Intensity of the disorder-induced D-band in graphitic materials is calculated as a function of the in-plane size of the graphite nanoparticles (La) and as a function of the excitation laser energy. Matrix elements associated with the double resonance Raman processes, i.e., electron–photon, electron–phonon and electron–defect processes are calculated based on the tight binding method. The electron–defect interaction is calculated by considering the elastic scattering at the armchair edge of graphite, adopting a nanographite flake whose width is La. We compare the calculated results with the experimental results obtained from the spectra for different laser lines and La.
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chirality dependent g band Raman Intensity of carbon nanotubes
Physical Review B, 2001Co-Authors: R. Saito, Gene Dresselhaus, A Jorio, Jason H Hafner, Charles M Lieber, M Hunter, T Mcclure, Mildred S. DresselhausAbstract:The chirality-dependent G-band Raman Intensity of single wall carbon nanotubes is calculated using a nonresonant theory for the Raman tensor. We obtain six or three intense Raman modes, respectively, for chiral or achiral nanotubes, whose relative intensities depend on the chiral angle of the nanotube. The longitudinal and transverse optical phonon modes in two-dimensional graphite become, respectively, transverse and longitudinal optical phonon modes in a one-dimensional nanotube. Confocal micro-Raman measurements of individual single wall carbon nanotubes show chirality-dependent spectra of the G-band Intensity, as predicted by this theory.
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Raman Intensity of single-wall carbon nanotubes
Physical Review B - Condensed Matter and Materials Physics, 1998Co-Authors: R. Saito, Tsutomu Takeya, Gene Dresselhaus, Mildred S. DresselhausAbstract:Using nonresonant bond-polarization theory, the Raman Intensity of a single-wall carbon nanotube is cal- culated as a function of the polarization of light and the chirality of the carbon nanotube. The force-constant tensor for calculating phonon dispersion relations in the nanotubes is scaled from those for two-dimensional graphite. The calculated Raman spectra do not depend much on the chirality, while their frequencies clearly depend on the nanotube diameter. The polarization and sample orientation dependence of the Raman Intensity shows that the symmetry of the Raman modes can be obtained by varying the direction of the nanotube axis, keeping the polarization vectors of the light fixed
Mildred S. Dresselhaus - One of the best experts on this subject based on the ideXlab platform.
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the influence of strong electron and hole doping on the Raman Intensity of chemical vapor deposition graphene
ACS Nano, 2010Co-Authors: Martin Kalbac, Alfonso Reinacecco, Hootan Farhat, Jing Kong, Ladislav Kavan, Mildred S. DresselhausAbstract:Electrochemical charging has been applied to study the influence of doping on the Intensity of the various Raman features observed in chemical vapor-deposition-grown graphene. Three different laser excitation energies have been used to probe the influence of the excitation energy on the behavior of both the G and G′ modes regarding their dependence on doping. The intensities of both the G and G′ modes exhibit a significant but different dependence on doping. While the Intensity of the G′ band monotonically decreases with increasing magnitude of the electrode potential (positive or negative), for the G band a more complex behavior has been found. The striking feature is an increase of the Raman Intensity of the G mode at a high value of the positive electrode potential. Furthermore, the observed increase of the Raman Intensity of the G mode is found to be a function of laser excitation energy.
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chirality dependent g band Raman Intensity of carbon nanotubes
Physical Review B, 2001Co-Authors: R. Saito, Gene Dresselhaus, A Jorio, Jason H Hafner, Charles M Lieber, M Hunter, T Mcclure, Mildred S. DresselhausAbstract:The chirality-dependent G-band Raman Intensity of single wall carbon nanotubes is calculated using a nonresonant theory for the Raman tensor. We obtain six or three intense Raman modes, respectively, for chiral or achiral nanotubes, whose relative intensities depend on the chiral angle of the nanotube. The longitudinal and transverse optical phonon modes in two-dimensional graphite become, respectively, transverse and longitudinal optical phonon modes in a one-dimensional nanotube. Confocal micro-Raman measurements of individual single wall carbon nanotubes show chirality-dependent spectra of the G-band Intensity, as predicted by this theory.
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Raman Intensity of single-wall carbon nanotubes
Physical Review B - Condensed Matter and Materials Physics, 1998Co-Authors: R. Saito, Tsutomu Takeya, Gene Dresselhaus, Mildred S. DresselhausAbstract:Using nonresonant bond-polarization theory, the Raman Intensity of a single-wall carbon nanotube is cal- culated as a function of the polarization of light and the chirality of the carbon nanotube. The force-constant tensor for calculating phonon dispersion relations in the nanotubes is scaled from those for two-dimensional graphite. The calculated Raman spectra do not depend much on the chirality, while their frequencies clearly depend on the nanotube diameter. The polarization and sample orientation dependence of the Raman Intensity shows that the symmetry of the Raman modes can be obtained by varying the direction of the nanotube axis, keeping the polarization vectors of the light fixed
Philippe Lambin - One of the best experts on this subject based on the ideXlab platform.
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theoretical Raman Intensity of the g and 2d bands of strained graphene
Carbon, 2013Co-Authors: V N Popov, Philippe LambinAbstract:Abstract The Raman G and 2D bands of uniaxially strained graphene are studied within a non-orthogonal tight-binding model for parallel scattering geometry and laser photon energy of 2.5 eV. The derived strain rate of the G band, as well as its Intensity as a function of the strain direction and light polarization angle, are found in very good agreement with previous reports. The simulated 2D band shows a complex peak structure with two or three resolved subbands. The dependence of the strain rate and the Raman Intensity of the latter on the strain direction and light polarization angle follows simple trigonometric expressions. Noticeable deviations from these expressions are observed for the polarization angle dependence. It is also shown quantitatively that the contribution to the 2D band of the “inner” processes is about 10 times larger than that of the “outer” processes. Our predictions for the 2D band behavior of strained graphene can be used for monitoring the strain in graphene-based applications by Raman spectroscopy.
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Theoretical Raman Intensity of the radial breathing mode of single-walled carbon nanotubes
physica status solidi (b), 2007Co-Authors: Valentin N. Popov, Philippe LambinAbstract:The atomistic calculations of the physical properties of perfect single-walled carbon nanotubes can be performed successfully by use of the helical symmetry of the nanotubes. The efficiency of this approach is illustrated by calculations of the electronic band structure, lattice dynamics, and the resonant Raman Intensity of the radial-breathing mode for all nanotubes in the diameter range from 0.6 nm to 2.4 nm within a symmetry-adapted nonorthogonal tight-binding model. It is shown that the derived electron-phonon coupling and the Raman Intensity are in fair agreement with recent Raman data on individual nanotubes.
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resonant Raman Intensity of the totally symmetric phonons of single walled carbon nanotubes
Physical Review B, 2006Co-Authors: V N Popov, Philippe LambinAbstract:The resonant Raman Intensity of the totally symmetric phonons of all single-walled carbon nanotubes in the radius range from $2.5\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}11.5\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$ was calculated within a symmetry-adapted nonorthogonal tight-binding model. The obtained Intensity of these modes exhibits radius and chirality dependence. The simulated Raman spectra of samples of moderate-diameter tubes with a Gaussian diameter distribution show characteristic peaks at about 1540, 1570, and $1593\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ originating from $LO$ phonons of metallic tubes, $TO$ phonons of metallic and semiconducting tubes, and $LO$ phonons of semiconducting tubes, respectively. This general behavior of the Raman spectra corresponds to that of the normally measured spectra.
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electron phonon and electron photon interactions and resonant Raman scattering from the radial breathing mode of single walled carbon nanotubes
Physical Review B, 2005Co-Authors: V N Popov, Luc Henrard, Philippe LambinAbstract:The resonance Raman profile of the radial-breathing mode is calculated for all 300 single-walled carbon nanotubes in the radius range from 2 A to 12 A and for all optical transitions up to 3.5 eV using a symmetryadapted nonorthogonal tight-binding model V. N. Popov, New J. Phys. 6 ,1 72004. The influence of the electron-phonon and electron-photon interactions on the Raman Intensity is studied using an approximate expression for the Intensity in the vicinity of each optical transition as the product of the electron-phonon coupling matrix element, the momentum matrix element, and the effective mass raised to different powers. The dependence of the latter three quantities and the maximum Raman Intensity on the nanotube radius, the chiral angle, and the optical transition energy is discussed in detail. In particular, the points of the corresponding plots exhibit family behavior of three different types. It is shown that the widespread practice to neglect the electron-photon and electron-phonon interactions in the estimation of the Intensity can lead to incorrect prediction of the Raman spectra.
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resonant Raman Intensity of the radial breathing mode of single walled carbon nanotubes within a nonorthogonal tight binding model
Nano Letters, 2004Co-Authors: V N Popov, Luc Henrard, Philippe LambinAbstract:The resonant Raman Intensity of the radial breathing mode is calculated for 50 narrow semiconducting single-walled carbon nanotubes within a symmetry-adapted nonorthogonal tight-binding model. The matrix elements of the momentum and the deformation potential in the quantum-mechanical formula for the Intensity are calculated explicitly. The results for the resonance Raman profiles can be used directly in the determination of the diameter distribution of the nanotubes in a sample. Three Raman spectra are simulated and compared to existing experimental data.
Richard A Mathies - One of the best experts on this subject based on the ideXlab platform.
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homogeneity of phytochrome cph1 vibronic absorption revealed by resonance Raman Intensity analysis
Journal of the American Chemical Society, 2009Co-Authors: Katelyn M Spillane, Jyotishman Dasgupta, Clark J Lagarias, Richard A MathiesAbstract:Phytochromes are an important class of red/far-red responsive photoreceptors that act as light-activated biological switches, ultimately driving growth and development in plants, bacteria, and fungi. The composition of the red-absorbing ground-state has been widely debated due to the presence of a shoulder feature on the blue edge of electronic absorption spectra, which many have attributed to the presence of multiple ground-state conformers. Here we use resonance Raman Intensity analysis to calculate the vibronic absorption profile of cyanobacterial phytochrome Cph1 and show that this shoulder feature is due simply to vibronic transitions from a single species, thus reflecting a homogeneous ground-state population.
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excited state structure and dynamics of cis and trans azobenzene from resonance Raman Intensity analysis
Journal of Physical Chemistry A, 2007Co-Authors: Christina M Stuart, Renee R Frontiera, Richard A MathiesAbstract:Resonance Raman Intensity analysis was used to investigate the initial excited-state nuclear dynamics of cis- and trans-azobenzene following S1 (nπ*) excitation, and fluorescence quantum yield measurements were used to estimate the excited-state lifetimes. trans-Azobenzene exhibits the strongest Raman intensities in its skeletal stretching and bending modes, while torsional motions dominate the nuclear relaxation of cis-azobenzene as indicated by intense Raman lines at 275, 542, 594, and 778 cm-1. The very weak fluorescence quantum yield for cis-azobenzene is consistent with its ∼100 fs electronic lifetime while trans-azobenzene, with a fluorescence quantum yield of 1.1 × 10-5, has an estimated S1 lifetime of ∼3 ps. The absorption and Raman cross-sections of both isomers were modeled to produce a harmonic displaced excited-state potential energy surface model revealing the initial nuclear motions on the reactive surface, as well as values for the homogeneous and inhomogeneous linewidths. For cis-azobenzen...
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Resonance Raman Intensity analysis of the excited-state proton transfer in 2-hydroxyacetophenone
The Journal of Physical Chemistry, 1992Co-Authors: Linda A. Peteanu, Richard A MathiesAbstract:Resonance Raman spectra have been obtained of 2-hydroxyacetophenone (OHAP) using an excitation wavelength (337 nm) which is resonant with the proton-transfer electronic absorption band. Fourteen modes are found to be significantly enhanced, the most intense of which is the 1324-cm -1 symmetric stretch of the substituted benzene ring. No displacement is observed along the hydroxy stretching coordinate in the Franck-condon region of the excited state. Furthermore, the modes which exhibited significant excited-state displacements were found to be insensitive to the replacement of the exchangeable proton for a deuteron
V N Popov - One of the best experts on this subject based on the ideXlab platform.
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theoretical Raman Intensity of the g and 2d bands of strained graphene
Carbon, 2013Co-Authors: V N Popov, Philippe LambinAbstract:Abstract The Raman G and 2D bands of uniaxially strained graphene are studied within a non-orthogonal tight-binding model for parallel scattering geometry and laser photon energy of 2.5 eV. The derived strain rate of the G band, as well as its Intensity as a function of the strain direction and light polarization angle, are found in very good agreement with previous reports. The simulated 2D band shows a complex peak structure with two or three resolved subbands. The dependence of the strain rate and the Raman Intensity of the latter on the strain direction and light polarization angle follows simple trigonometric expressions. Noticeable deviations from these expressions are observed for the polarization angle dependence. It is also shown quantitatively that the contribution to the 2D band of the “inner” processes is about 10 times larger than that of the “outer” processes. Our predictions for the 2D band behavior of strained graphene can be used for monitoring the strain in graphene-based applications by Raman spectroscopy.
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resonant Raman Intensity of the totally symmetric phonons of single walled carbon nanotubes
Physical Review B, 2006Co-Authors: V N Popov, Philippe LambinAbstract:The resonant Raman Intensity of the totally symmetric phonons of all single-walled carbon nanotubes in the radius range from $2.5\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}11.5\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$ was calculated within a symmetry-adapted nonorthogonal tight-binding model. The obtained Intensity of these modes exhibits radius and chirality dependence. The simulated Raman spectra of samples of moderate-diameter tubes with a Gaussian diameter distribution show characteristic peaks at about 1540, 1570, and $1593\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ originating from $LO$ phonons of metallic tubes, $TO$ phonons of metallic and semiconducting tubes, and $LO$ phonons of semiconducting tubes, respectively. This general behavior of the Raman spectra corresponds to that of the normally measured spectra.
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electron phonon and electron photon interactions and resonant Raman scattering from the radial breathing mode of single walled carbon nanotubes
Physical Review B, 2005Co-Authors: V N Popov, Luc Henrard, Philippe LambinAbstract:The resonance Raman profile of the radial-breathing mode is calculated for all 300 single-walled carbon nanotubes in the radius range from 2 A to 12 A and for all optical transitions up to 3.5 eV using a symmetryadapted nonorthogonal tight-binding model V. N. Popov, New J. Phys. 6 ,1 72004. The influence of the electron-phonon and electron-photon interactions on the Raman Intensity is studied using an approximate expression for the Intensity in the vicinity of each optical transition as the product of the electron-phonon coupling matrix element, the momentum matrix element, and the effective mass raised to different powers. The dependence of the latter three quantities and the maximum Raman Intensity on the nanotube radius, the chiral angle, and the optical transition energy is discussed in detail. In particular, the points of the corresponding plots exhibit family behavior of three different types. It is shown that the widespread practice to neglect the electron-photon and electron-phonon interactions in the estimation of the Intensity can lead to incorrect prediction of the Raman spectra.
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resonant Raman Intensity of the radial breathing mode of single walled carbon nanotubes within a nonorthogonal tight binding model
Nano Letters, 2004Co-Authors: V N Popov, Luc Henrard, Philippe LambinAbstract:The resonant Raman Intensity of the radial breathing mode is calculated for 50 narrow semiconducting single-walled carbon nanotubes within a symmetry-adapted nonorthogonal tight-binding model. The matrix elements of the momentum and the deformation potential in the quantum-mechanical formula for the Intensity are calculated explicitly. The results for the resonance Raman profiles can be used directly in the determination of the diameter distribution of the nanotubes in a sample. Three Raman spectra are simulated and compared to existing experimental data.
