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Sum-frequency Generation (sum-frequency + generation)

Distribution by Scientific Domains
Chemistry57%

Terms modified by Sum-frequency Generation

  • sum-frequency generation spectroscopy
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    Selected Abstracts

    Identification of chemical species of fluorescein isothiocyanate isomer,I (FITC) monolayers on platinum by doubly resonant sum-frequency generation spectroscopy

    JOURNAL OF RAMAN SPECTROSCOPY, Issue 11 2008
    Toshiki Maeda
    Abstract Doubly resonant sum-frequency generation (DR-SFG) spectroscopy of fluorescein-4-isothiocyanate isomer-I (FITC) monolayers on platinum was performed. Vibrational spectra of the monolayers for the IR wavenumber of 1750,1450 cm,1 were measured with visible probes ranging from 431 to 582 nm. Two vibrational bands at 1643 and 1610 cm,1 were observed, and their DR-SFG excitation profiles displayed different shapes. By rinsing the monolayers with an alkaline solution, the smaller wavenumber band disappeared and the larger wavenumber band gained intensity. On the basis of the spectral response to the rinsing, we concluded that the FITC molecules existed on platinum as deprotonated and protonated forms; the former corresponds to the 1643 cm,1 band and the latter to the 1610 cm,1 band. The deprotonated form was assigned to an anionic surface species, and the protonated form to a neutral surface species by comparing the DR-SFG excitation profiles with electronic absorption spectra of the protolytic forms of fluorescein in an aqueous solution (Sjöback R et al., Spectrochimica Acta A 1995; 51: L7,L21). The results demonstrate that the measurement of DR-SFG excitation profiles is a useful technique to identify chemical species of monolayers on metal surfaces. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Time-resolved coherent Raman and sum-frequency generation spectroscopy with wavelength-tunable, short-pulse, photonic-crystal fiber light sources

    JOURNAL OF RAMAN SPECTROSCOPY, Issue 8 2007
    A. M. Zheltikov
    Abstract Photonic-crystal fibers deliver frequency-tunable radiation within the wavelength range stretching from the ultraviolet to the near-infrared with output pulse widths from tens of femtoseconds to a few picoseconds and peak powers from a few watts to several megawatts, suggesting a convenient, efficient, and compact fiber format of short-pulse sources for time-resolved nonlinear spectroscopy and microscopy. Here, we examine the potential of photonic-crystal fiber light sources for time-resolved studies of ultrafast population and coherence relaxation dynamics in molecular systems using coherent anti-Stokes Raman scattering and two-photon-resonant sum-frequency generation. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    All-optical single-to-dual channel wavelength conversion based on sum-frequency generation and difference-frequency generation

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2006
    Jian Wang
    Abstract Single-to-dual channel wavelength conversion at 40 Gbit/s is experimentally observed based on sum-frequency generation and difference-frequency generation in periodically poled LiNbO3 waveguides. Wavelength relationships between dual-channel idler waves and three incident waves are investigated in detail. The results imply that dual-channel idler wavelengths and channel spacing can be controlled by appropriately tuning two pump wavelengths. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2057,2060, 2006; Published online in Wiley Inter-Science (www.interscience.wiley.com). DOI 10.1002/mop.21840 [source]

    Excitonic effects in the nonlinear optical response of a Si(111) surface

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 8 2010
    Maria Stamova
    Abstract We discuss methods to calculate the linear and nonlinear optical spectra for cyclic cluster models of an ideal Si(111) surface. The cluster approach offers the possibility to implement the excitonic effects due to the Coulomb interaction between electron and hole in a relatively straight-forward way. In order to appproximate a situation resembling a surface we use clusters with several hundreds of Si atoms. The electronic structure is obtained from a tight-binding parametrization of the hamiltonian. A time-dependent density operator formalism is used to calculate the response functions and for the optical polarization, which also directly describe the response to ultrashort pulses. Their Fourier transforms are the frequency-dependent optical susceptibilities and for second-harmonic () or sum-frequency generation from surfaces. The excitonic Coulomb interaction is treated in the time-dependent Hartree,Fock approximation, leading to large sets of differential equations that are integrated explicitly. The results on the linear susceptibility are in accord with earlier findings on the excitonic origin of the relative intensities of the E1 and E2 peaks near 3.4 and 4.3,eV. We present new results on excitonic effects in the nonlinear spectra and investigate in particular the surface-related peaks near 2,=,1.3,1.5 and 2.4,eV that govern the strong enhancement observed in SHG of clean silicon surfaces. [source]

    In Situ Characterization of Thermo-Responsive Poly(N -Isopropylacrylamide) Films with Sum-Frequency Generation Spectroscopy

    CHEMPHYSCHEM, Issue 7 2010
    Volker Kurz
    Abstract The thermo-responsive behaviour of thiol modified poly(N -isopropylacrylamide) (pNIPAM) films immobilized on gold are probed by in situ broadband sum-frequency generation (SFG) spectroscopy. The pNIPAM films were prepared by atom transfer radical polymerization (ATRP) using a nitro-biphenyl-thiol (NBT)-SAM on a polycrystalline gold surface as a substrate. Additionally, Raman and infrared reflection absorption spectroscopy (IRRAS) are applied to spin-coated pNIPAM films. Molecular groups involved in the reorientation and disordering of the polymer chains during the LCST (lower critical solution temperature) transition of pNIPAM are identified. The characteristic vibrations of the CH3 groups show a gradual reorientation of the isopropyl groups within the pNIPAM film and instantaneous reorientation of the outermost CH3 groups around 32,°C. [source]

    Theoretical Simulation of Vibrational Sum-Frequency Generation Spectra from Density Functional Theory: Application to p -Nitrothiophenol and 2,4-Dinitroaniline

    CHEMPHYSCHEM, Issue 12 2009
    Julien Guthmuller Dr.
    Abstract The molecular orientation of adsorbed molecules forming self-assembled monolayers can be determined by combining vibrational sum-frequency generation (SFG) measurements with quantum chemical calculations. Herein, we present a theoretical methodology used to simulate the SFG spectra for different combinations of polarizations. These simulations are based on calculations of the IR vectors and Raman tensors, which are obtained from density functional theory computations. The dependency of the SFG vibrational signature with respect to the molecular orientation is presented for the molecules p -nitrothiophenol and 2,4-dinitroaniline. It is found that a suitable choice of basis set as well as of exchange-correlation (XC) functional is mandatory to correctly simulate the SFG intensities and consequently provide an accurate estimation of the adsorbed molecule orientation. Comparison with experimental data shows that calculations performed at the B3LYP/6-311++G(d,p) level of approximation provide good agreement with experimental frequencies, and with IR and Raman intensities. In particular, it is demonstrated that polarization and diffuse functions are compulsory for reproducing the IR and Raman spectra, and consequently vibrational SFG spectra, of systems such as p -nitrothiophenol. Moreover, the investigated XC functionals reveal their influence on the relative intensities, which show rather systematic variations with the amount of Hartree,Fock exchange. Finally, further aspects of the modeling are revealed by considering the frequency dependence of the Raman tensors. [source]