The Experts below are selected from a list of 285 Experts worldwide ranked by ideXlab platform
Jeffrey Moses - One of the best experts on this subject based on the ideXlab platform.
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ultrafast control of material optical properties via the infrared resonant Raman Effect
Physical Review X, 2021Co-Authors: Guru Khalsa, Nicole A Benedek, Jeffrey MosesAbstract:A theoretical and computational analysis shows that it is possible to precisely control the optical properties of a material by optically exciting crystalline lattice vibrations, or phonons.
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ultrafast control of material optical properties via the infrared resonant Raman Effect
Bulletin of the American Physical Society, 2021Co-Authors: Guru Khalsa, Nicole A Benedek, Jeffrey MosesAbstract:The Raman Effect -- inelastic scattering of light by lattice vibrations (phonons) -- produces an optical response closely tied to a material's crystal structure. Here we show that resonant optical excitation of IR and Raman phonons gives rise to a Raman scattering Effect that can induce giant shifts to the refractive index and induce new optical constants that are forbidden in the equilibrium crystal structure. We complete the description of light-matter interactions mediated by coupled IR and Raman phonons in crystalline insulators -- currently the focus of numerous experiments aiming to dynamically control material properties -- by including a forgotten pathway through the nonlinear lattice polarizability. Our work expands the toolset for control and development of new optical technologies by revealing that the absorption of light within the terahertz gap can enable control of optical properties of materials over a broad frequency range.
Yousoo Kim - One of the best experts on this subject based on the ideXlab platform.
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controlling the resonance Raman Effect in tip enhanced Raman spectroscopy using a thin insulating film
Applied Spectroscopy, 2020Co-Authors: Rafael Jaculbia, Hiroshi Imada, Norihiko Hayazawa, Yousoo KimAbstract:Both surface-enhanced Raman spectroscopy (SERS) and tip-enhanced Raman spectroscopy (TERS) are widely used for the investigation of nanoscale materials. One of the most critical aspects of both SERS and TERS is the control of both the plasmon and molecular resonance precisely. Here, we demonstrate single-molecule TERS under molecular resonance conditions using a scanning tunneling microscope. This was achieved by placing the molecule on a sodium chloride (NaCl) film in order to directly compare the absorption with Raman excitation spectra. Varying the NaCl film thickness changes the degree of screening Effect from the metal surface, which leads to a variation of the molecular resonance phenomena. Although it is generally accepted that the target molecule should be directly attached to the metal surface in SERS, our observation using TERS suggests that this is not always optimal, especially under molecular resonance Raman conditions. Our work demonstrates the possibility of controlling molecular resonance by carefully modifying the local environment. This will be useful for future investigation of isolated single molecules or even two-dimensional molecular assemblies.
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single molecule resonance Raman Effect in a plasmonic nanocavity
Nature Nanotechnology, 2020Co-Authors: Rafael Jaculbia, Hiroshi Imada, Kuniyuki Miwa, Takeshi Iwasa, Masato Takenaka, Bo Yang, Emiko Kazuma, Norihiko Hayazawa, Tetsuya Taketsugu, Yousoo KimAbstract:Tip-enhanced Raman spectroscopy (TERS) is a versatile tool for chemical analysis at the nanoscale. In earlier TERS experiments, Raman modes with components parallel to the tip were studied based on the strong electric field enhancement along the tip. Perpendicular modes were usually neglected. Here, we investigate an isolated copper naphthalocyanine molecule adsorbed on a triple-layer NaCl on Ag(111) using scanning tunnelling microscope TERS imaging. For flat-lying molecules on NaCl, the Raman images present different patterns depending on the symmetry of the vibrational mode. Our results reveal that components of the electric field perpendicular to the tip should be considered aside from the parallel components. Moreover, under resonance excitation conditions, the perpendicular components can play a substantial role in the enhancement. This single-molecule study in a well-defined environment provides insights into the Raman process at the plasmonic nanocavity, which may be useful in the nanoscale metrology of various molecular systems. Tip-enhanced Raman spectroscopy can provide chemical sensitivity at a single-molecule level. Measurements on individual molecules adsorbed on a thin salt layer unveil that components of the electric field perpendicular to the tip provide sensitivity to the symmetry of the vibrational modes of the molecule.
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single molecule resonance Raman Effect in a plasmonic nanocavity
Nature Nanotechnology, 2020Co-Authors: Rafael Jaculbia, Hiroshi Imada, Kuniyuki Miwa, Takeshi Iwasa, Masato Takenaka, Bo Yang, Emiko Kazuma, Norihiko Hayazawa, Tetsuya Taketsugu, Yousoo KimAbstract:Tip-enhanced Raman spectroscopy (TERS) is a versatile tool for chemical analysis at the nanoscale. In earlier TERS experiments, Raman modes with components parallel to the tip were studied based on the strong electric field enhancement along the tip. Perpendicular modes were usually neglected. Here, we investigate an isolated copper naphthalocyanine molecule adsorbed on a triple-layer NaCl on Ag(111) using scanning tunnelling microscope TERS imaging. For flat-lying molecules on NaCl, the Raman images present different patterns depending on the symmetry of the vibrational mode. Our results reveal that components of the electric field perpendicular to the tip should be considered aside from the parallel components. Moreover, under resonance excitation conditions, the perpendicular components can play a substantial role in the enhancement. This single-molecule study in a well-defined environment provides insights into the Raman process at the plasmonic nanocavity, which may be useful in the nanoscale metrology of various molecular systems.
G Dresselhaus - One of the best experts on this subject based on the ideXlab platform.
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anomalous two peak g band Raman Effect in one isolated single wall carbon nanotube
Physical Review B, 2002Co-Authors: A Souza G Filho, A Jorio, Anna K Swan, M S Unlu, B B Goldberg, Riichiro Saito, Jason H Hafner, Charles M Lieber, M A Pimenta, G DresselhausAbstract:The resonant second-order G'-band Raman spectra of isolated single-wall carbon nanotubes (SWNTs) exhibit an interesting resonance phenomenon, whereby the G' band for some special (n,m) isolated SWNTs exhibits a two-peak structure, while for most SWNTs, the G'-band profile is a single Lorentzian peak. The two-peak phenomenon is explained by combining the double-resonance Raman Effect, originally introduced for graphite, with the singular electronic structure of SWNTs, which is unique for a given (n,m) pair. Therefore, the G'-band profile is strongly dependent on the joint density of electronic states and provides useful information about the electronic structure and on the (n,m) assignment for the specific SWNT that is in resonance with the laser.
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resonant Raman Effect in single wall carbon nanotubes
Journal of Materials Research, 1998Co-Authors: M A Pimenta, G Dresselhaus, A Marucci, S D M Brown, Manyalibo J Matthews, Apparao M Rao, P C Eklund, R E Smalley, Mildred S DresselhausAbstract:A resonant Raman study of single-wall carbon nanotubes (SWNT) using several laser lines between 0.94 and 3.05 eV is presented. A detailed lineshape analysis shows that the bands associated with the nanotube radial breathing mode are composed of a sum of individual peaks whose relative intensities depend strongly on the laser energy, in agreement with prior work. On the other hand, the shape of the Raman bands associated with the tangential C–C stretching motions in the 1500–1600 cm−1 range does not depend significantly on the laser energy for laser excitation energies in the ranges 0.94–1.59 eV and 2.41–3.05 eV. However, new C–C stretching modes are observed in the spectra collected using laser excitations with energies close to 1.9 eV. The new results are discussed in terms of the difference between the 1D electronic density of states for the semiconducting and metallic carbon nanotubes.
A M Steane - One of the best experts on this subject based on the ideXlab platform.
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implementation of a symmetric surface electrode ion trap with field compensation using a modulated Raman Effect
New Journal of Physics, 2010Co-Authors: D T C Allcock, Jeff Sherman, D N Stacey, A H Burrell, Michael Curtis, G Imreh, N M Linke, D J Szwer, S C Webster, A M SteaneAbstract:We describe a new electrode design for a surface-electrode Paul trap, which allows rotation of the normal modes out of the trap plane, and a technique for micromotion compensation in all directions using a two-photon process, which avoids the need for an ultraviolet laser directed to the trap plane. The fabrication and characterization of the trap are described, as well as its implementation for the trapping and cooling of single Ca+ ions. We also propose a repumping scheme that increases ion fluorescence and simplifies heating rate measurements obtained by time-resolved ion fluorescence during Doppler cooling.
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implementation of a symmetric surface electrode ion trap with field compensation using a modulated Raman Effect
arXiv: Quantum Physics, 2009Co-Authors: D T C Allcock, Jeff Sherman, D N Stacey, A H Burrell, Michael Curtis, G Imreh, N M Linke, D J Szwer, S C Webster, A M SteaneAbstract:We describe the fabrication and characterization of a new surface-electrode Paul ion trap designed for experiments in scalable quantum information processing with Ca+. A notable feature is a symmetric electrode pattern which allows rotation of the normal modes of ion motion, yielding efficient Doppler cooling with a single beam parallel to the planar surface. We propose and implement a technique for micromotion compensation in all directions using an infrared repumper laser beam directed into the trap plane. Finally, we employ an alternate repumping scheme that increases ion fluorescence and simplifies heating rate measurements obtained by time-resolved ion fluorescence during Doppler cooling.
M A Pimenta - One of the best experts on this subject based on the ideXlab platform.
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anomalous two peak g band Raman Effect in one isolated single wall carbon nanotube
Physical Review B, 2002Co-Authors: A Souza G Filho, A Jorio, Anna K Swan, M S Unlu, B B Goldberg, Riichiro Saito, Jason H Hafner, Charles M Lieber, M A Pimenta, G DresselhausAbstract:The resonant second-order G'-band Raman spectra of isolated single-wall carbon nanotubes (SWNTs) exhibit an interesting resonance phenomenon, whereby the G' band for some special (n,m) isolated SWNTs exhibits a two-peak structure, while for most SWNTs, the G'-band profile is a single Lorentzian peak. The two-peak phenomenon is explained by combining the double-resonance Raman Effect, originally introduced for graphite, with the singular electronic structure of SWNTs, which is unique for a given (n,m) pair. Therefore, the G'-band profile is strongly dependent on the joint density of electronic states and provides useful information about the electronic structure and on the (n,m) assignment for the specific SWNT that is in resonance with the laser.
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resonant Raman Effect in single wall carbon nanotubes
Journal of Materials Research, 1998Co-Authors: M A Pimenta, G Dresselhaus, A Marucci, S D M Brown, Manyalibo J Matthews, Apparao M Rao, P C Eklund, R E Smalley, Mildred S DresselhausAbstract:A resonant Raman study of single-wall carbon nanotubes (SWNT) using several laser lines between 0.94 and 3.05 eV is presented. A detailed lineshape analysis shows that the bands associated with the nanotube radial breathing mode are composed of a sum of individual peaks whose relative intensities depend strongly on the laser energy, in agreement with prior work. On the other hand, the shape of the Raman bands associated with the tangential C–C stretching motions in the 1500–1600 cm−1 range does not depend significantly on the laser energy for laser excitation energies in the ranges 0.94–1.59 eV and 2.41–3.05 eV. However, new C–C stretching modes are observed in the spectra collected using laser excitations with energies close to 1.9 eV. The new results are discussed in terms of the difference between the 1D electronic density of states for the semiconducting and metallic carbon nanotubes.
