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Sample records for absorption resonance raman

  1. Rapidly reconfigurable slow-light system based on off-resonant Raman absorption

    NASA Astrophysics Data System (ADS)

    Vudyasetu, Praveen K.; Camacho, Ryan M.; Howell, John C.

    2010-11-01

    We present a slow-light system based on dual Raman absorption resonances in warm rubidium vapor. Each Raman absorption resonance is produced by a control beam in an off-resonant Λ system. This system combines all optical control of the Raman absorption and the low-dispersion broadening properties of the double Lorentzian absorption slow light. The bandwidth, group delay, and central frequency of the slow-light system can all be tuned dynamically by changing the properties of the control beam. We demonstrate multiple pulse delays with low distortion and show that such a system has fast switching dynamics and thus fast reconfiguration rates.

  2. Deep ultraviolet Raman spectroscopy: A resonance-absorption trade-off illustrated by diluted liquid benzene

    NASA Astrophysics Data System (ADS)

    Chadwick, C. T.; Willitsford, A. H.; Philbrick, C. R.; Hallen, H. D.

    2015-12-01

    The magnitude of resonance Raman intensity, in terms of the real signal level measured on-resonance compared to the signal level measured off-resonance for the same sample, is investigated using a tunable laser source. Resonance Raman enhancements, occurring as the excitation energy is tuned through ultraviolet absorption lines, are used to examine the 1332 cm-1 vibrational mode of diamond and the 992 cm-1 ring-breathing mode of benzene. Competition between the wavelength dependent optical absorption and the magnitude of the resonance enhancement is studied using measured signal levels as a function of wavelength. Two system applications are identified where the resonance Raman significantly increases the real signal levels despite the presence of strong absorption: characterization of trace species in laser remote sensing and spectroscopy of the few molecules in the tiny working volumes of near-field optical microscopy.

  3. Ultraviolet resonance Raman and absorption difference spectroscopy of myoglobins: titration behavior of individual tyrosine residues.

    PubMed

    Asher, S A; Larkin, P J; Teraoka, J

    1991-06-18

    The UV resonance Raman spectra of horse and sperm whale myoglobin excited at 240 nm show bands between 600 and 1700 cm-1 which derive from tyrosyl and tryptophyl residues. No significant contribution from phenylalanine and peptide backbone vibrations occurs at this excitation wavelength. We examine the pH dependence of the UV resonance Raman and UV absorption difference spectra of these myoglobins to correlate the local protein environment of the tyrosyl residues as given by the protein crystal structure to their pKa values, molar absorptivities, and Raman cross sections. Some of our pKa values for the tyrosinate residues of horse Mb differ from those of previous studies. We show that the lambda max values, the molar absorptivities, and the Raman cross sections are sensitive to the local environment of the tyrosinate residues in the protein. We relate differences in the tyrosyl absorption spectra to differences in Raman cross sections. In addition, we discuss the importance to the Raman cross sections of the local electromagnetic field enhancement due to the dielectric environment of the tyrosinate residues in the protein. This local field should scale the Raman cross sections in a way useful as a probe of the average aromatic amino acid residue environment.

  4. Atmospheric absorption versus deep ultraviolet (pre-)resonance in Raman lidar measurements

    NASA Astrophysics Data System (ADS)

    Hallen, Hans D.; Willitsford, Adam H.; Neely, Ryan R.; Chadwick, C. Todd; Philbrick, C. Russell

    2016-05-01

    The Raman scattering of several liquids and solid materials has been investigated near the deep ultraviolet absorption features corresponding to the electron energy states of the chemical species present. It is found to provide significant enhancement, but is always accompanied by absorption due to that or other species along the path. We investigate this trade-off for water vapor, although the results for liquid water and ice will be quantitatively very similar. An optical parametric oscillator (OPO) was pumped by the third harmonic of a Nd:YAG laser, and the output frequency doubled to generate a tunable excitation beam in the 215-600 nm range. We use the tunable laser excitation beam to investigate pre-resonance and resonance Raman spectroscopy near an absorption band of ice. A significant enhancement in the Raman signal was observed. The A-term of the Raman scattering tensor, which describes the pre-resonant enhancement of the spectra, is also used to find the primary observed intensities as a function of incident beam energy, although a wide resonance structure near the final-state-effect related absorption in ice is also found. The results suggest that use of pre-resonant or resonant Raman LIDAR could increase the sensitivity to improve spatial and temporal resolution of atmospheric water vapor measurements. However, these shorter wavelengths also exhibit higher ozone absorption. These opposing effects are modeled using MODTRAN for several configurations relevant for studies of boundary layer water and in the vicinity of clouds. Such data could be used in studies of the measurement of energy flow at the water-air and cloud-air interface, and may help with understanding some of the major uncertainties in current global climate models.

  5. Theoretical studies on absorption, emission, and resonance Raman spectra of Coumarin 343 isomers.

    PubMed

    Wu, Wenpeng; Cao, Zexing; Zhao, Yi

    2012-03-21

    The vibrationally resolved spectral method and quantum chemical calculations are employed to reveal the structural and spectral properties of Coumarin 343 (C343), an ideal candidate for organic dye photosensitizers, in vacuum and solution. The results manifest that the ground-state energies are dominantly determined by different placements of hydrogen atom in carboxylic group of C343 conformations. Compared to those in vacuum, the electronic absorption spectra in methanol solvent show a hyperchromic property together with the redshift and blueshift for the neutral C343 isomers and their deprotonated anions, respectively. From the absorption, emission, and resonance Raman spectra, it is found that the maximal absorption and emission come from low-frequency modes whereas the high-frequency modes have high Raman activities. The detailed spectra are further analyzed for the identification of the conformers and understanding the potential charge transfer mechanism in their photovoltaic applications.

  6. Evidence for pyrroloquinolinequinone as the carbonyl cofactor in lysyl oxidase by absorption and resonance Raman spectroscopy.

    PubMed

    Williamson, P R; Moog, R S; Dooley, D M; Kagan, H M

    1986-12-15

    The present study investigated the possibility that pyrroloquinolinequinone (PQQ), an aromatic carbonyl recently indicated to be the carbonyl cofactor in bovine plasma amine oxidase, may also be present at the active site of lysyl oxidase. The absorption and resonance Raman spectra of the phenylhydrazones of bovine plasma amine oxidase, of peptides derived from the active site of bovine aorta lysyl oxidase, and of PQQ were very similar, indicating that the carbonyl cofactor of lysyl oxidase is PQQ or a compound which closely resembles PQQ.

  7. Assignment of bacteriochlorophyll a ligation state from absorption and resonance raman spectra

    SciTech Connect

    Callahan, P.M.; Cotton, T.M.

    1987-11-11

    Absorption and Soret excitation resonance Raman (RR) spectra have been obtained for a series of coordination forms on monomeric bacteriochlorophyll a (BChl a). Strong and moderate intensity bands are observed in the RR spectrum at 1609 and 1530 cm/sup -1/ for five-coordinate species, which shift to 1595 and 1512 cm/sup -1/, respectively, in the six-coordinate form. These coordination-sensitive vibrations are independent of the nature of the axial ligand and are suggested to have significant C/sub a/ C/sub m/ character, while several other less intense coordination-sensitive bands at 1463, 1444, and 1375 cm/sup -1/ are considered to arise from C/sub b/C/sub b/ and C/sub a/N stretching vibrations. These coordination-sensitive RR bands were used to determine BChl a ligation state in the solvents used, and structure correlations based on absorption maxima have been developed. The Q/sub x/ absorption band position is sensitive not only to BChl a Mg/sup 2 +/ coordination number but also to the nature of the axial ligand, i.e., oxygen, sulfur, or nitrogen. Q/sub x/ maxima are observed at 570, 575-580, and 582 nm for five-coordinate oxygen, sulfur, and nitrogen ligands, respectively, and at 590-595 and 605-612 nm, for six-coordinate oxygen and nitrogen species, respectively. The Q/sub y/ absorption maximum is insensitive to coordination number changes but is dependent on the nature of the axial ligand: 770 nm for oxygen ligand(s) and 775 nm for nitrogen ligand(s). A similar series of absorption and Soret excitation RR spectra were obtained for the demetalated form of BChl a, BPheo a.

  8. Resonance Raman and vibronic absorption spectra with Duschinsky rotation from a time-dependent perspective: Application to β-carotene

    NASA Astrophysics Data System (ADS)

    Banerjee, Shiladitya; Kröner, Dominik; Saalfrank, Peter

    2012-12-01

    The time-dependent approach to electronic spectroscopy, as popularized by Heller and co-workers in the 1980s, is applied here in conjunction with linear-response, time-dependent density functional theory to study vibronic absorption and resonance Raman spectra of β-carotene, with and without a solvent. Two-state models, the harmonic and the Condon approximations are used in order to do so. A new code has been developed which includes excited state displacements, vibrational frequency shifts, and Duschinsky rotation, i.e., mode mixing, for both non-adiabatic spectroscopies. It is shown that Duschinsky rotation has a pronounced effect on the resonance Raman spectra of β-carotene. In particular, it can explain a recently found anomalous behaviour of the so-called ν1 peak in resonance Raman spectra [N. Tschirner, M. Schenderlein, K. Brose, E. Schlodder, M. A. Mroginski, C. Thomsen, and P. Hildebrandt, Phys. Chem. Chem. Phys. 11, 11471 (2009)], 10.1039/b917341b, which shifts with the change in excitation wavelength.

  9. Theory of dynamic absorption spectroscopy of nonstationary states. 4. Application to 12-fs resonant impulsive Raman spectroscopy of bacteriorhodopsin

    SciTech Connect

    Pollard, W.T.; Peteanu, L.A.; Mathies, R.A.

    1992-07-23

    A time-dependent theory for femtosecond dynamic absorption spectroscopy is used to describe the creation and observation of molecular ground-state vibrational coherence through the resonance impulsive stimulated Raman mechanism. Model calculations show that the oscillatory absorption signal that arises from this ground-state coherence is maximized for a limited range of pulse lengths and that there is a complex relationship between the probe wavelength and the strength of the spectral oscillations. The generalized time-dependent linear susceptibility of the nonstationary system created by the impulsive pump pulse is defined and used to discuss the strong dependence of the measured signals on the properties of the probe pulse. Finally, calculations are presented to analyze the high-frequency oscillations ({approximately}20-fs period) recently observed in the transient absorption spectra of light-adapted bacteriorhodopsin (BR{sub 568}) following excitation with a 12-fs optical pulse. At the probe wavelengths used in this experiment, the contribution of stimulated emission is negligible at long times because of the extremely rapid excited-state isomerization; as a result, the spectral oscillations observed after this time are due to the impulsive excitation of coherent vibrations in the ground state. The transient response observed for BR{sub 568} is calculated using a 29-mode harmonic potential surface derived from a prior resonance Raman intensity analysis. Both the oscillatory signals and their dependence on the probe wavelength are satisfactorily reproduced. 68 refs., 11 figs.

  10. Zeaxanthin ([3R,3'R]-beta, beta-carotene-3-3'diol) as a resonance Raman and visible absorption probe of membrane structure.

    PubMed Central

    Mendelsohn, R; Van Holten, R W

    1979-01-01

    When zeaxanthin ([3R,3R']-beta, beta-carotene-3,3'diol) is inserted into phospholipid dispersions and the latter heated through their gel-liquid crystal phase transitions, large changes are noted in the resonance Raman and absorption spectra of the carotenoid molecule. By analogy with the data of Carey and co-workers (J. Raman Spectrosc. 6:282) who studied the aggregation of zeaxanthin in acetone-water solutions, it is suggested that the carotenoid aggregates in the phospholipid gel state while forming a monomer in liquid crystal phases. The alterations in both the visible absorption and resonance Raman data have been used to monitor phospholipid phase behavior in dipalmitoylphosphatidylcholine and distearoylphosphatidylcholine, (DSPC) one-component systems and binary mixtures. The phase diagram obtained for the binary system, as constructed from visible absorption and resonance Raman data, is compared with that of Shimshick and McConnell (Biochemistry. 12:2351) obtained from electron spin resonance (ESR) studies. Although the agreement between absorption and ESR data is generally satisfactory, onset temperatures for phase separation at low DSPC mole fractions deduced from resonance Raman measurements are several degrees lower than those from the other methods. Nevertheless, the use of zeaxanthin as a resonance Raman and visible absorption probe behavior will be useful in some situations where ordinary Raman spectroscopic data cannot be obtained easily. The advantage of the resonance Raman approach is illustrated in a study of the phase behavior of a phospholipid extract of a cel- mutant of Neurospora crassa. A phase separation region is observed with onset and completion temperatures of -19 and -6 degrees C, respectively. PMID:162448

  11. Time-resolved absorption and resonance Raman investigations of short-lived intermediates in solution or occluded in zeolites

    NASA Astrophysics Data System (ADS)

    Brémard, C.; Buntinx, G.; De Waele, V.; Didierjean, C.; Gener, I.; Poizat, O.

    1999-05-01

    Two examples of structural investigation of photogenerated short-lived transient species of aromatic compounds, by using time-resolved electronic absorption and resonance Raman spectroscopy are provided. The picosecond Raman spectra of the lowest excited singlet state (S 1) of 4,4'-bipyridine and 2,2'-bipyridine in solution are discussed first. The results provide strong evidence for a surprising asymmetric S 1 structure in which the electronic excitation and the consequent structural distortion are localized in one of the pyridyl rings, the other ring being almost unaffected. The laser photolysis of biphenyl occluded in the pores and cavities of ZSM-5 and faujasitic zeolites have been investigated in the nanosecond time-scale as functions of aluminium content, the extraframework cations, sample loading and intensity of photolysis. At low pump power and low aluminium content the triplet state of biphenyl is observed. At higher pump power and in aluminated zeolites, biphotonic ionization was observed to generate the cation radical. As the loading increased, the anion radical yield increased. This is characteristic of faujasitic zeolites in which scavenger molecules with restricted diffusional motions are confined in the vicinity of photoionized molecules. The lifetimes of cation radical were particularly long in aluminated ZSM-5 zeolites with efficient trapping sites of the photoejected electron.

  12. Resonance Raman and temperature-dependent electronic absorption spectra of cavity and noncavity models of the hydrated electron

    PubMed Central

    Casey, Jennifer R.; Larsen, Ross E.; Schwartz, Benjamin J.

    2013-01-01

    Most of what is known about the structure of the hydrated electron comes from mixed quantum/classical simulations, which depend on the pseudopotential that couples the quantum electron to the classical water molecules. These potentials usually are highly repulsive, producing cavity-bound hydrated electrons that break the local water H-bonding structure. However, we recently developed a more attractive potential, which produces a hydrated electron that encompasses a region of enhanced water density. Both our noncavity and the various cavity models predict similar experimental observables. In this paper, we work to distinguish between these models by studying both the temperature dependence of the optical absorption spectrum, which provides insight into the balance of the attractive and repulsive terms in the potential, and the resonance Raman spectrum, which provides a direct measure of the local H-bonding environment near the electron. We find that only our noncavity model can capture the experimental red shift of the hydrated electron’s absorption spectrum with increasing temperature at constant density. Cavity models of the hydrated electron predict a solvation structure similar to that of the larger aqueous halides, leading to a Raman O–H stretching band that is blue-shifted and narrower than that of bulk water. In contrast, experiments show the hydrated electron has a broader and red-shifted O–H stretching band compared with bulk water, a feature recovered by our noncavity model. We conclude that although our noncavity model does not provide perfect quantitative agreement with experiment, the hydrated electron must have a significant degree of noncavity character. PMID:23382233

  13. Auger resonant Raman spectroscopy

    SciTech Connect

    Azuma, Y.; LeBrun, T.; MacDonald, M.; Southworth, S.H.

    1995-08-01

    As noted above, traditional spectroscopy of the electronic structure of the inner shells of atoms, molecules, and solids is limited by the lifetime broadening of the core-excited states. This limitation can also be avoided with the non-radiative analog of X-ray Raman scattering - resonant Auger Raman spectroscopy. We have used this technique to study the K-shell excitation spectrum of argon as the photon energy is continuously scanned across threshold.

  14. Simulating One-Photon Absorption and Resonance Raman Scattering Spectra Using Analytical Excited State Energy Gradients within Time-Dependent Density Functional Theory

    SciTech Connect

    Silverstein, Daniel W.; Govind, Niranjan; van Dam, Hubertus J. J.; Jensen, Lasse

    2013-12-10

    A parallel implementation of analytical time-dependent density functional theory gradients is presented for the quantum chemistry program NWChem. The implementation is based on the Lagrangian approach developed by Furche and Ahlrichs. To validate our implementation, we first calculate the Stokes shifts for a range of organic dye molecules using a diverse set of exchange-correlation functionals (traditional density functionals, global hybrids, and range-separated hybrids) followed by simulations of the one-photon absorption and resonance Raman scattering spectrum of the phenoxyl radical, the well-studied dye molecule rhodamine 6G, and a molecular host–guest complex (TTFcCBPQT4+). The study of organic dye molecules illustrates that B3LYP and CAM-B3LYP generally give the best agreement with experimentally determined Stokes shifts unless the excited state is a charge transfer state. Absorption, resonance Raman, and fluorescence simulations for the phenoxyl radical indicate that explicit solvation may be required for accurate characterization. For the host–guest complex and rhodamine 6G, it is demonstrated that absorption spectra can be simulated in good agreement with experimental data for most exchange-correlation functionals. Finally, however, because one-photon absorption spectra generally lack well-resolved vibrational features, resonance Raman simulations are necessary to evaluate the accuracy of the exchange-correlation functional for describing a potential energy surface.

  15. X-ray absorption and resonance raman spectroscopy of human myeloperoxidase at neutral and acid pH.

    PubMed

    Yue, K T; Taylor, K L; Kinkade, J M; Sinclair, R B; Powers, L S

    1997-04-01

    Myeloperoxidase (MPO), an important enzyme in the oxygen-dependent host defense system of human polymorphonuclear leukocytes, utilizes hydrogen peroxide to catalyze the production of hypochlorous acid, an oxidizing bactericidal agent. While MPO shows significant sequence homology with other peroxidases and this homology is particularly striking among the active-site residues, MPO exhibits unusual spectral features and the unique ability to catalyze the oxidation of chloride ions. We have investigated the MPO active-site with X-ray absorption (XAS) and resonance Raman (RRS) spectroscopies at neutral pH and also at the physiological acidic pH (pH approximately 3) and have compared these results with those of horseradish peroxidase (HRP). At pH 7.5, XAS results show that the iron heme active site is 6-coordinate where the distal ligand is likely nitrogen or oxygen, but not sulfur. The heme is distorted compared to HRP, other peroxidases, and heme compounds, but at pH approximately 3, the distal ligand is lost and the heme is less distorted. RRS results under identical pH conditions show that the skeletal core-size sensitive modes and v3 are shifted to higher frequency at pH approximately 3 indicating a 6- to 5-coordination change of high spin ferric heme. In addition, a new band at 270 cm(-1) is observed at pH approximately 3 which is consistent with the loss of the sixth ligand. The higher symmetry of the heme at pH approximately 3 is reflected by a single v4 mode in the (RRS) spectrum. HRP also loses its loosely associated distal water at this pH, but little change in heme distortion is observed. This change suggests that loss of the distal ligand in MPO releases stress on the heme which may facilitate binding of chloride ion.

  16. Protein dynamics in an intermediate state of myoglobin: optical absorption, resonance Raman spectroscopy, and x-ray structure analysis.

    PubMed Central

    Engler, N; Ostermann, A; Gassmann, A; Lamb, D C; Prusakov, V E; Schott, J; Schweitzer-Stenner, R; Parak, F G

    2000-01-01

    A metastable state of myoglobin is produced by reduction of metmyoglobin at low temperatures. This is done either by irradiation with x-rays at 80 K or by electron transfer from photoexcited tris(2, 2'-bipyridine)-ruthenium(II) at 20 K. At temperatures above 150 K, the conformational transition toward the equilibrium deoxymyoglobin is observed. X-ray crystallography, Raman spectroscopy, and temperature-dependent optical absorption spectroscopy show that the metastable state has a six-ligated iron low-spin center. The x-ray structure at 115K proves the similarity of the metastable state with metmyoglobin. The Raman spectra yield the high-frequency vibronic modes and give additional information about the distortion of the heme. Analysis of the temperature dependence of the line shape of the Soret band reveals that a relaxation within the metastable state starts at approximately 120 K. Parameters representative of static properties of the intermediate state are close to those of CO-ligated myoglobin, while parameters representative of dynamics are close to deoxymyoglobin. Thus within the metastable state the relaxation to the equilibrium is initiated by changes in the dynamic properties of the active site. PMID:10733986

  17. Resonance-Enhanced Raman Scattering of Ring-Involved Vibrational Modes in the (1)B(2u) Absorption Band of Benzene, Including the Kekule Vibrational Modes ν(9) and ν(10).

    PubMed

    Willitsford, Adam H; Chadwick, C Todd; Kurtz, Stewart; Philbrick, C Russell; Hallen, Hans

    2016-02-01

    Resonance Raman spectroscopy provides much stronger Raman signal levels than its off-resonant counterpart and adds selectivity by excitation tuning. Raman preresonance of benzene has been well studied. On-resonance studies, especially at phonon-allowed absorptions, have received less attention. In this case, we observe resonance of many of the vibration modes associated motion of the carbons in the ring while tuning over the (1)B2u absorption, including the related ν9 (CC stretch Herzberg notation, ν14 Wilson notation) and ν10 (CH-parallel bend Herzberg notation, ν15 Wilson notation) vibrational modes along with the ν2 (CC-stretch or ring-breathing Herzberg notation, ν1 Wilson notation) mode and multiples of the ν18 (CCC-parallel bend Herzberg notation, ν6 Wilson notation) vibrational mode. The ring-breathing mode is found to mix with the b2u modes creating higher frequency composites. Through the use of an optical parametric oscillator (OPO) to tune through the (1)B2u absorption band of liquid benzene, a stiffening (increase in energy) of the vibrational modes is observed as the excitation wavelength nears the (1)B2u absorption peak of the isolated molecule (vapor) phase. The strongest resonance amplitude observed is in the 2 × ν18 (e2g) mode, with nearly twice the intensity of the ring-breathing mode, ν2. Several overtones and combination modes, especially with ν2 (a1g), are also observed to resonate. Raman resonances on phonon-allowed excitations are narrow and permit the measurement of vibrations not Raman-active in the ground state. PMID:26731431

  18. Wavelength dependent resonance Raman band intensity of broadband stimulated Raman spectroscopy of malachite green in ethanol.

    PubMed

    Cen, Qiongyan; He, Yuhan; Xu, Mei; Wang, Jingjing; Wang, Zhaohui

    2015-03-21

    Resonance broadband stimulated Raman spectroscopy of malachite green in ethanol has been performed. With a tuning picosecond visible laser source and a broadband Raman probe, the Raman gain and loss spectra have been measured simultaneously. By scanning the Raman pump across the first absorption band of the molecule, we found that the resonant Raman bands could be only seen when the pump laser tuned in the range of the red edge of the S1←S0 transition. Dispersive lineshapes of resonant Raman bands have been observed in the Raman loss spectra, while the line shape is normal (same as spontaneous Raman) in the Raman gain spectra. Although, the resonant bands in the loss spectrum are usually stronger than that in the gain spectrum, the band intensities of both loss and gain linearly increase with the pump energy. The relative magnitude of each corresponding resonant band in the Raman loss and gain varies with the pump wavelength. Mode specified Raman excitation profiles have been obtained through broadband stimulated Raman measurement.

  19. Wavelength dependent resonance Raman band intensity of broadband stimulated Raman spectroscopy of malachite green in ethanol

    NASA Astrophysics Data System (ADS)

    Cen, Qiongyan; He, Yuhan; Xu, Mei; Wang, Jingjing; Wang, Zhaohui

    2015-03-01

    Resonance broadband stimulated Raman spectroscopy of malachite green in ethanol has been performed. With a tuning picosecond visible laser source and a broadband Raman probe, the Raman gain and loss spectra have been measured simultaneously. By scanning the Raman pump across the first absorption band of the molecule, we found that the resonant Raman bands could be only seen when the pump laser tuned in the range of the red edge of the S1←S0 transition. Dispersive lineshapes of resonant Raman bands have been observed in the Raman loss spectra, while the line shape is normal (same as spontaneous Raman) in the Raman gain spectra. Although, the resonant bands in the loss spectrum are usually stronger than that in the gain spectrum, the band intensities of both loss and gain linearly increase with the pump energy. The relative magnitude of each corresponding resonant band in the Raman loss and gain varies with the pump wavelength. Mode specified Raman excitation profiles have been obtained through broadband stimulated Raman measurement.

  20. High-resolution study of the x-ray resonant Raman scattering process around the 1s absorption edge for aluminium, silicon, and their oxides

    SciTech Connect

    Szlachetko, J.; Dousse, J.-Cl.; Berset, M.; Fennane, K.; Szlachetko, M.; Hoszowska, J.; Barrett, R.; Pajek, M.; Kubala-Kukus, A.

    2007-02-15

    X-ray resonant Raman scattering (RRS) spectra of Al, Al{sub 2}O{sub 3}, Si, and SiO{sub 2} were measured at the European Synchrotron Radiation Facility, using a high-resolution Bragg-type curved crystal spectrometer. The x-ray RRS spectra were collected at several beam energies tuned below the 1s absorption thresholds of Al and Si. Differences in the spectral features between the elemental samples and the oxide ones were clearly observed. The data were interpreted using the second-order perturbation theory within the Kramers-Heisenberg (KH) approach. It is shown that, using the KH formalism, oscillator strengths that are similar to the ones deduced from x-ray absorption measurements can be extracted from emission x-ray RRS spectra. The total cross sections for the x-ray RRS process were derived for the different photon beam energies and compared with theoretical predictions. For elemental silicon, the weak 1s-3p excitation was observed and found to be consistent with results of density of states calculations.

  1. Resonance Raman spectroscopy.

    PubMed

    Li, Jiang; Kitagawa, Teizo

    2014-01-01

    Flavin is a general name given to molecules having the heteroaromatic ring system of 7,8-dimethylisoalloxazine but practically means riboflavin (Rfl), flavin adenine dinucleotide (FAD), and flavin mononucleotide (FMN) in biological systems, whose structures are illustrated in Fig. 1, together with the atomic numbering scheme and ring numbering of the isoalloxazine moiety. As the isoalloxazine skeleton cannot be synthesized in human cells, it is obtained from diet as Rfl (vitamin B2). FAD and FMN can act as cofactors in flavoenzymes but Rfl does not. Most flavoenzymes catalyze redox reactions of substrates (Miura, Chem Rec 1:183-194, 2001). When O2 serves as the oxidant in the oxidation half cycle of an enzymic reaction, the enzyme is called "flavo-oxidase" but when others do, the enzyme is called "flavo-dehydrogenase." The difference between the two types of oxidative catalysis arises from delicate differences in the π-electron distributions in the isoalloxazine ring, which can be revealed by Raman spectroscopy (Miura, Chem Rec 1:183-194, 2001). Since a flavin is an extremely versatile molecule, the scientific field including chemistry, biochemistry, and enzymology is collectively called "flavonology." It was found recently, however, that the flavin also acts as a chromophore to initiate light-induced DNA repair and signal transductions (Sancar, Chem Rev 103:2203-2237, 2003).

  2. Picosecond Resonance Raman Spectroscopy of Visual Pigments.

    NASA Astrophysics Data System (ADS)

    Carlsen, William Frederick

    We have constructed a picosecond Raman spectrometer to obtain information about primary events in visual excitation. The excitation source at 532 nm is a frequency doubled modelocked Nd:YAG laser optimized for short pulses, high repetition rates, and high pulse to pulse stability. The sample illumination geometry is optimized for pulsed Raman measurements using low magnification light collection and optical multi-channel detection. This instrument gives high signal to noise ratios and high data rates. The visual pigment rhodopsin was studied with this picosecond Raman instrument. We found that within 20 picoseconds of absorbing a photon, low wavenumber Raman bands characteristic of the first photo-intermediate bathorhodopsin appear. This scattering at 853, 875, and 920 wavenumbers arises from enhanced hydrogen out of plane vibrations from a strained all-trans configuration of the retinal chromophore in the protein. Furthermore, bands characteristic of isorhodopsin appear within the 10 picosecond pulse. We therefore conclude that the 11-cis retinal chromophore of rhodopsin isomerizes to a strained all-trans configuration and can further isomerize to a 9-cis form on absorbing a second photon, all within 20 picoseconds. Measurements starting with isorhodopsin show that the reverse process, 9-cis to trans to 11-cis, can also occur within 20 picoseconds. The resonance Raman spectra of bathorhodopsin formed from rhodopsin, however, exhibits consistent small differences from that of bathorhodopsin formed from isorhodopsin. Spectra of corresponding pigments deuterated at the retinal 12 carbon position also show slight differences. These data suggest that the bathorhodopsins formed from rhodopsin and isorhodopsin are initially different. They appear, however, to converge to a common intermediate by the end of 20 picoseconds. This resonance Raman study reveals that much of the isomerization of retinal takes place within a few picoseconds of the absorption of a photon by

  3. Time and neighbor interaction in resonance Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Hallen, Hans D.; Niu, Shupeng; Li, Ling

    2014-09-01

    We study systems in which the resonance Raman process is fast due to the requirement for phonon involvement in the absorption. The resonance enhancement is found to track the isolated molecule, or vapor phase, absorption since the molecule does not have time to exchange energy with its neighbors. This corroborates with studies of pre-resonance, where Heisenberg's uncertainty principle enforces a rapid process, but differs from resonance on electronically allowed transitions, where the resonance allows a relatively prolonged interaction. High resolution excitation spectroscopy reveals large gains and narrow features usually associated with the isolated molecule. Vibration energies shift as the resonance is approached and the excited state vibration levels are probed. Several multiplets and overtone modes are enhanced along with the strongly coupled ring-breathing mode in aromatic molecules.

  4. Resonant enhancement of Raman scattering in metamaterials with hybrid electromagnetic and plasmonic resonances

    NASA Astrophysics Data System (ADS)

    Guddala, Sriram; Narayana Rao, D.; Ramakrishna, S. Anantha

    2016-06-01

    A tri-layer metamaterial perfect absorber of light, consisting of (Al/ZnS/Al) films with the top aluminum layer patterned as an array of circular disk nanoantennas, is investigated for resonantly enhancing Raman scattering from C60 fullerene molecules deposited on the metamaterial. The metamaterial is designed to have resonant bands due to plasmonic and electromagnetic resonances at the Raman pump frequency (725 nm) as well as Stokes emission bands. The Raman scattering from C60 on the metamaterial with resonantly matched bands is measured to be enhanced by an order of magnitude more than C60 on metamaterials with off-resonant absorption bands peaking at 1090 nm. The Raman pump is significantly enhanced due to the resonance with a propagating surface plasmon band, while the highly impedance-matched electromagnetic resonance is expected to couple out the Raman emission efficiently. The nature and hybridization of the plasmonic and electromagnetic resonances to form compound resonances are investigated by numerical simulations.

  5. Surface-enhanced resonance Raman scattering from methylviologen at a silver electrode: Evidence for two distinct adsorption interactions

    SciTech Connect

    Feng, Qiao; Yue, W.; Cotton, T.M. )

    1990-03-08

    The electronic absorption and resonance Raman spectra of methylviologen radical cation (MV{sup {sm bullet}+}) and fully reduced methylviologen (MV{sup 0}) have been characterized. The enhancement of Raman and resonance Raman (RR) scattering from the dication and its reduction products at polished and roughened silver electrodes was also investigated.

  6. Resonant Absorption of Bessel Beams

    NASA Astrophysics Data System (ADS)

    Fan, J.; Parra, E.; Milchberg, H. M.

    1999-11-01

    We report the first observation of enhanced laser-plasma optical absorption in a subcritical density plasma resulting from spatial resonances, here in the laser breakdown of a gas with a Bessel beam. The enhancement in absorption is directly correlated to enhancements both in confinement of laser radiation to the plasma and in its heating. Under certain conditions, azimuthal asymmetry in the laser beam is essential for efficient gas breakdown. Simulations of this absorption consistently explain the experimental observations. This work is supported by the National Science Foundation (PHY-9515509) and the US Department of Energy (DEF G0297 ER 41039).

  7. Pre-resonance Raman spectra of some simple gases. [sulfur oxides, hydrogen sulfide, and nitrogen oxides

    NASA Technical Reports Server (NTRS)

    Low, P. W.

    1974-01-01

    The pre-resonance Raman spectra of SO2, N2O, and H2S were investigated using the 4880 A, 4727 A, and 4579 A lines of the argon ion laser. Although these molecules have electronic absorption bands in the near ultraviolet, none exhibit any pre-resonance enhancement within our experimental error of + or - 10%. Possible explanations taking into account the current theories for resonance Raman are discussed.

  8. Resonant impulsive-stimulated Raman scattering on malachite green

    SciTech Connect

    Chesnoy, J.; Mokhtari, A.

    1988-10-01

    We have studied in the femtosecond regime the transient dynamics of dichroism (anisotropic absorption), birefringence, and frequency shift induced by an intense femtosecond pump beam in the dye malachite green in solution. Vibrational quantum beats were observed superimposed on the saturated absorption and dispersion signals and quantitatively explained in terms of impulsive-stimulated Raman scattering close to an electronic resonance. The selectivity for observation of the vibrations in the two electronic states is described for the different experimental schemes. We discuss the access to vibrational and electronic dynamics in both ground and excited electronic states and compare the possibilities to those of previous techniques.

  9. UV-resonance Raman spectroscopy of amino acids

    NASA Astrophysics Data System (ADS)

    Höhl, Martin; Meinhardt-Wollweber, Merve; Schmitt, Heike; Lenarz, Thomas; Morgner, Uwe

    2016-03-01

    Resonant enhancement of Raman signals is a useful method to increase sensitivity in samples with low concentration such as biological tissue. The investigation of resonance profiles shows the optimal excitation wavelength and yields valuable information about the molecules themselves. However careful characterization and calibration of all experimental parameters affecting quantum yield is required in order to achieve comparability of the single spectra recorded. We present an experimental technique for measuring the resonance profiles of different amino acids. The absorption lines of these molecules are located in the ultraviolet (UV) wavelength range. One limitation for broadband measurement of resonance profiles is the limited availability of Raman filters in certain regions of the UV for blocking the Rayleigh scattered light. Here, a wavelength range from 244.8 nm to 266.0 nm was chosen. The profiles reveal the optimal wavelength for recording the Raman spectra of amino acids in aqueous solutions in this range. This study provides the basis for measurements on more complex molecules such as proteins in the human perilymph. The composition of this liquid in the inner ear is essential for hearing and cannot be analyzed non-invasively so far. The long term aim is to implement this technique as a fiber based endoscope for non-invasive measurements during surgeries (e. g. cochlear implants) making it available as a diagnostic tool for physicians. This project is embedded in the interdisciplinary cluster of excellence "Hearing for all" (H4A).

  10. Double resonance Raman modes in monolayer and few-layer MoTe2

    NASA Astrophysics Data System (ADS)

    Guo, Huaihong; Yang, Teng; Yamamoto, Mahito; Zhou, Lin; Ishikawa, Ryo; Ueno, Keiji; Tsukagoshi, Kazuhito; Zhang, Zhidong; Dresselhaus, Mildred S.; Saito, Riichiro

    2015-05-01

    We study the second-order Raman process of mono- and few-layer MoTe2, by combining ab initio density functional perturbation calculations with experimental Raman spectroscopy using 532, 633, and 785 nm excitation lasers. The calculated electronic band structure and the density of states show that the resonance Raman process occurs at the M point in the Brillouin zone, where a strong optical absorption occurs due to a logarithmic Van Hove singularity of the electronic density of states. The double resonance Raman process with intervalley electron-phonon coupling connects two of the three inequivalent M points in the Brillouin zone, giving rise to second-order Raman peaks due to the M -point phonons. The calculated vibrational frequencies of the second-order Raman spectra agree with the observed laser-energy-dependent Raman shifts in the experiment.

  11. Ultraviolet Resonant Raman Enhancements in the Detection of Explosives

    SciTech Connect

    Short Jr., Billy Joe

    2009-06-01

    Raman-based spectroscopy is potentially militarily useful for standoff detection of high explosives. Normal (non-resonance) and resonance Raman spectroscopies are both light scattering techniques that use a laser to measure the vibrational spectrum of a sample. In resonance Raman, the laser is tuned to match the wavelength of a strong electronic absorbance in the molecule of interest, whereas, in normal Raman the laser is not tuned to any strong electronic absorbance bands. The selection of appropriate excitation wavelengths in resonance Raman can result in a dramatic increase in the Raman scattering efficiency of select band(s) associated with the electronic transition. Other than the excitation wavelength, however, resonance Raman is performed experimentally the same as normal Raman. In these studies, normal and resonance Raman spectral signatures of select solid high explosive (HE) samples and explosive precursors were collected at 785 nm, 244 nm and 229 nm. Solutions of PETN, TNT, and explosive precursors (DNT & PNT) in acetonitrile solvent as an internal Raman standard were quantitatively evaluated using ultraviolet resonance Raman (UVRR) microscopy and normal Raman spectroscopy as a function of power and select excitation wavelengths. Use of an internal standard allowed resonance enhancements to be estimated at 229 nm and 244 nm. Investigations demonstrated that UVRR provided ~2000-fold enhancement at 244 nm and ~800-fold improvement at 229 nm while PETN showed a maximum of ~25-fold at 244 nm and ~190-fold enhancement at 229 nm solely from resonance effects when compared to normal Raman measurements. In addition to the observed resonance enhancements, additional Raman signal enhancements are obtained with ultraviolet excitation (i.e., Raman scattering scales as !4 for measurements based on scattered photons). A model, based partly on the resonance Raman enhancement results for HE solutions, is presented for estimating Raman enhancements for solid HE samples.

  12. X-ray resonant Raman spectroscopy

    SciTech Connect

    Cowan, P.L.; LeBrun, T.; Deslattes, R.D.

    1995-08-01

    X-ray resonant Raman scattering presents great promise as a high-resolution spectroscopic probe of the electronic structure of matter. Unlike other methods, the technique avoids the loss of energy resolution resulting from the lifetime broadening of short-lived core-excited states. In addition, measurements of polarization and angular anisotropies yield information on the symmetries of electronic states of atoms and molecules. We studied the L{sub 3} edge of xenon, where the lifetime broadening is a major feature of the spectra recorded previously. X-ray fluorescence spectra were taken of both the L{alpha}{sub l,2} and L{beta}{sub 2,15} peaks over a range of energies from 10 eV below the edge to 40 eV above. These spectra show the evolution of resonant Raman scattering into characteristic fluorescence as the photon energy is scanned across the edge, and confirm several features of these spectra such as asymmetries in resonant peak shapes due to the onset of the ionization continuum. These results constitute the most comprehensive study of X-ray resonant Raman scattering to date, and were submitted for publication. Studies of other cases are under way, and new instruments that would match the unique characteristics of the APS - and thus render a new range of experiments possible - are under consideration.

  13. Resonance IR: a coherent multidimensional analogue of resonance Raman.

    PubMed

    Boyle, Erin S; Neff-Mallon, Nathan A; Handali, Jonathan D; Wright, John C

    2014-05-01

    This work demonstrates the use of triply resonant sum frequency (TRSF) spectroscopy as a "resonance IR" analogue to resonance Raman spectroscopy. TRSF is a four-wave-mixing process where three lasers with independent frequencies interact coherently with a sample to generate an output at their triple summation frequency. The first two lasers are in the infrared and result in two vibrational excitations, while the third laser is visible and induces a two-quantum anti-Stokes resonance Raman transition. The signal intensity grows when the laser frequencies are all in resonance with coupled vibrational and electronic states. The method therefore provides electronic enhancement of IR-active vibrational modes. These modes may be buried beneath solvent in the IR spectrum and also be Raman-inactive and therefore inaccessible by other techniques. The method is presented on the centrosymmetric complex copper phthalocyanine tetrasulfonate. In this study, the two vibrational frequencies were scanned across ring-breathing modes, while the visible frequency was left in resonance with the copper phthalocyanine tetrasulfonate Q band, resulting in a two-dimensional infrared plot that also reveals coupling between vibrational states. TRSF has the potential to be a very useful probe of structurally similar biological motifs such as hemes, as well as synthetic transition-metal complexes. PMID:24707979

  14. Intercalation between antitumor anthracyclines and DNA as probed by resonance and surface-enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Smulevich, G.; Mantini, A. R.; Casu, M.; Marzocchi, M. P.

    1991-05-01

    The antiturnor anthracyclincs, idarubicin (IDA ), adrianiycin (ADM), epirubicin (EPI), carminomycin (CAR) and 1 1-deoxycarminornycin (DCM), whose siructural formula includes a substituted hydroxyanthraquirionc chrornophore and a sugar residue, form intercalation complexes with DNA. The stacking interaction between the chromophore and the base-pairs of DNA gives rise to noticeable ciTects on resonance Raman (RR) and surface-enhanced resonance Raman (SERRS) scattering as well as on the absorption (ABS), its second derivative (D2) and fluorescence emission (FEM) spectra.

  15. Electronic resonances in broadband stimulated Raman spectroscopy

    PubMed Central

    Batignani, G.; Pontecorvo, E.; Giovannetti, G.; Ferrante, C.; Fumero, G.; Scopigno, T.

    2016-01-01

    Spontaneous Raman spectroscopy is a formidable tool to probe molecular vibrations. Under electronic resonance conditions, the cross section can be selectively enhanced enabling structural sensitivity to specific chromophores and reaction centers. The addition of an ultrashort, broadband femtosecond pulse to the excitation field allows for coherent stimulation of diverse molecular vibrations. Within such a scheme, vibrational spectra are engraved onto a highly directional field, and can be heterodyne detected overwhelming fluorescence and other incoherent signals. At variance with spontaneous resonance Raman, however, interpreting the spectral information is not straightforward, due to the manifold of field interactions concurring to the third order nonlinear response. Taking as an example vibrational spectra of heme proteins excited in the Soret band, we introduce a general approach to extract the stimulated Raman excitation profiles from complex spectral lineshapes. Specifically, by a quantum treatment of the matter through density matrix description of the third order nonlinear polarization, we identify the contributions which generate the Raman bands, by taking into account for the cross section of each process. PMID:26728791

  16. Resonant Raman scattering background in XRF spectra of binary samples

    NASA Astrophysics Data System (ADS)

    Sánchez, Héctor Jorge; Leani, Juan José

    2015-02-01

    In x-ray fluorescence analysis, spectra present singular characteristics produced by the different scattering processes. When atoms are irradiated with incident energy lower and close to an absorption edge, scattering peaks appear due to an inelastic process known as resonant Raman scattering. In this work we present theoretical calculations of the resonant Raman scattering contributions to the background of x-ray fluorescence spectra of binary samples of current technological or biological interest. On one hand, a binary alloy of Fe with traces of Mn (Mn: 0.01%, Fe: 99.99%) was studied because of its importance in the stainless steels industries. On the second hand a pure sample of Ti with V traces (Ti: 99%, V: 1%) was analyzed due to the current relevance in medical applications. In order to perform the calculations the Shiraiwa and Fujino's model was used to calculate characteristic intensities and scattering interactions. This model makes certain assumptions and approximations to achieve the calculations, especially in the case of the geometrical conditions and the incident and take-off beams. For the binary sample studied in this work and the considered experimental conditions, the calculations show that the resonant Raman scattering background is significant under the fluorescent peak, affects the symmetry of the peaks and, depending on the concentrations, overcomes the enhancements contributions (secondary fluorescence).

  17. Negative refraction with low absorption using Raman transitions with magnetoelectric coupling

    SciTech Connect

    Sikes, D. E.; Yavuz, D. D.

    2010-07-15

    We suggest a scheme for obtaining negative refraction that does not require the simultaneous presence of an electric-dipole and a magnetic-dipole transition near the same transition frequency. The key idea of the scheme is to obtain a strong electric response by using far-off-resonant Raman transitions. We propose to use a pair of electric-dipole Raman transitions and utilize magneto-electric cross coupling to achieve a negative index of refraction without requiring negative permeability. The interference of the two Raman transitions allows tunable negative refraction with low absorption.

  18. Resonant stimulation of Raman scattering from single-crystal thiophene/phenylene co-oligomers

    SciTech Connect

    Yanagi, Hisao Marutani, Yusuke; Matsuoka, Naoki; Hiramatsu, Toru; Ishizumi, Atsushi; Sasaki, Fumio; Hotta, Shu

    2013-12-09

    Amplified Raman scattering was observed from single crystals of thiophene/phenylene co-oligomers (TPCOs). Under ns-pulsed excitation, the TPCO crystals exhibited amplified spontaneous emission (ASE) at resonant absorption wavelengths. With increasing excitation wavelength to the 0-0 absorption edge, the stimulated resonant Raman peaks appeared both in the 0-1 and 0-2 ASE band regions. When the excitation wavelength coincided with the 0-1 ASE band energy, the Raman peaks selectively appeared in the 0-2 ASE band. Such unusual enhancement of the 0-2 Raman scattering was ascribed to resonant stimulation via vibronic coupling with electronic transitions in the uniaxially oriented TPCO molecules.

  19. Resonance Raman Spectroscopy of Armchair Single-Walled Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Haroz, Erik; Rice, William; Lu, Benjamin; Hauge, Robert; Magana, Donny; Doorn, Stephen; Nikolaev, Pasha; Arepalli, Sivaram; Kono, Junichiro

    2009-03-01

    We performed resonance Raman spectroscopy studies of metallic single-walled carbon nanotubes (SWNTs), including armchair SWNTs from (6,6) through (10,10). The measurements were carried out with excitation of 440-850 nm on aqueous ensemble samples of SWNTs enriched in metallic species. From this, we generated Raman excitation profiles (REPs) of the radial breathing mode and compare the REPs of armchairs and other metallic species. Additionally, we measured REPs of the G-band mode and observed how the Breit-Wigner-Fano line shape of the G^- peak evolves in peak position, width and intensity relative to the G^+ peak as different metallic nanotubes are excited. By combining these studies with absorption and photoluminescence excitation spectroscopy studies, we present a comprehensive examination of the optical signatures of metallic SWNTs.

  20. Time-resolved resonance Raman spectroscopy: exploring reactive intermediates.

    PubMed

    Sahoo, Sangram Keshari; Umapathy, Siva; Parker, Anthony W

    2011-10-01

    The study of reaction mechanisms involves systematic investigations of the correlation between structure, reactivity, and time. The challenge is to be able to observe the chemical changes undergone by reactants as they change into products via one or several intermediates such as electronic excited states (singlet and triplet), radicals, radical ions, carbocations, carbanions, carbenes, nitrenes, nitrinium ions, etc. The vast array of intermediates and timescales means there is no single "do-it-all" technique. The simultaneous advances in contemporary time-resolved Raman spectroscopic techniques and computational methods have done much towards visualizing molecular fingerprint snapshots of the reactive intermediates in the microsecond to femtosecond time domain. Raman spectroscopy and its sensitive counterpart resonance Raman spectroscopy have been well proven as means for determining molecular structure, chemical bonding, reactivity, and dynamics of short-lived intermediates in solution phase and are advantageous in comparison to commonly used time-resolved absorption and emission spectroscopy. Today time-resolved Raman spectroscopy is a mature technique; its development owes much to the advent of pulsed tunable lasers, highly efficient spectrometers, and high speed, highly sensitive multichannel detectors able to collect a complete spectrum. This review article will provide a brief chronological development of the experimental setup and demonstrate how experimentalists have conquered numerous challenges to obtain background-free (removing fluorescence), intense, and highly spectrally resolved Raman spectra in the nanosecond to microsecond (ns-μs) and picosecond (ps) time domains and, perhaps surprisingly, laid the foundations for new techniques such as spatially offset Raman spectroscopy. PMID:21986070

  1. The resonance Raman excitation profile of fucoxanthin

    NASA Astrophysics Data System (ADS)

    Ballard, L. J.; Glasgow, L. A.; Hoskins, L. C.; Krohe, T.

    1989-01-01

    The resonance Raman excitation profiles (RREPs) of the ν 1 and ν 2 vibrations of fucoxanthin in acetone and toluene solvents have been studied. Fucoxanthin, which is a predominant pigment in marine seaweed and phytoplankton, has several structural differences from carotenoids for which excitation profiles have been determined. The RREPs for fucoxanthin are interpreted in terms of a two-mode model and show a B2 value which is approximately 20% lower than for carotenoids like β-carotene and lutein which occur in higher plants. Excellent fits between experimental data and the theoretical model were observed in both solvents.

  2. Super-Resonant Intracavity Coherent Absorption.

    PubMed

    Malara, P; Campanella, C E; Giorgini, A; Avino, S; De Natale, P; Gagliardi, G

    2016-01-01

    The capability of optical resonators to extend the effective radiation-matter interaction length originates from a multipass effect, hence is intrinsically limited by the resonator's quality factor. Here, we show that this constraint can be overcome by combining the concepts of resonant interaction and coherent perfect absorption (CPA). We demonstrate and investigate super-resonant coherent absorption in a coupled Fabry-Perot (FP)/ring cavity structure. At the FP resonant wavelengths, the described phenomenon gives rise to split modes with a nearly-transparent peak and a peak whose transmission is exceptionally sensitive to the intracavity loss. For small losses, the effective interaction pathlength of these modes is proportional respectively to the ratio and the product of the individual finesse coefficients of the two resonators. The results presented extend the conventional definition of resonant absorption and point to a way of circumventing the technological limitations of ultrahigh-quality resonators in spectroscopy and optical sensing schemes. PMID:27364475

  3. Rapid-flow resonance Raman spectroscopy of bacterial photosynthetic reaction centers.

    PubMed Central

    Shreve, A P; Cherepy, N J; Franzen, S; Boxer, S G; Mathies, R A

    1991-01-01

    Rapid-flow resonance Raman vibrational spectra of bacterial photosynthetic reaction centers from the R-26 mutant of Rhodobacter sphaeroides have been obtained by using excitation wavelengths (810-910 nm) resonant with the lowest energy, photochemically active electronic absorption. The technique of shifted excitation Raman difference spectroscopy is used to identify genuine Raman scattering bands in the presence of a large fluorescence background. The comparison of spectra obtained from untreated reaction centers and from reaction centers treated with the oxidant K3Fe(CN)6 demonstrates that resonance enhancement is obtained from the special pair. Relatively strong Raman scattering is observed for special pair vibrations with frequencies of 36, 94, 127, 202, 730, and 898 cm-1; other modes are observed at 71, 337, and 685 cm-1. Qualitative Raman excitation profiles are reported for some of the strong modes, and resonance enhancement is observed to occur throughout the near-IR absorption band of the special pair. These Raman data determine which vibrations are coupled to the optical absorption in the special pair and, thus, probe the nuclear motion that occurs after electronic excitation. Implications for the interpretation of previous hole-burning experiments and for the excited-state dynamics and photochemistry of reaction centers are discussed. PMID:1763034

  4. Rotational vibrational-rotational Raman differential absorption lidar for atmospheric ozone measurements: methodology and experiment.

    PubMed

    Reichardt, J; Bisson, S E; Reichardt, S; Weitkamp, C; Neidhart, B

    2000-11-20

    A single-laser Raman differential absorption lidar (DIAL) for ozone measurements in clouds is proposed. An injection-locked XeCl excimer laser serves as the radiation source. The ozone molecule number density is calculated from the differential absorption of the anti-Stokes rotational Raman return signals from molecular nitrogen and oxygen as the on-resonance wavelength and the vibrational-rotational Raman backscattering from molecular nitrogen or oxygen as the off-resonance wavelength. Model calculations show that the main advantage of the new rotational vibrational-rotational (RVR) Raman DIAL over conventional Raman DIAL is a 70-85% reduction in the wavelength-dependent effects of cloud-particle scattering on the measured ozone concentration; furthermore the complexity of the apparatus is reduced substantially. We describe a RVR Raman DIAL setup that uses a narrow-band interference-filter polychromator as the lidar receiver. Single-laser ozone measurements in the troposphere and lower stratosphere are presented, and it is shown that on further improvement of the receiver performance, ozone measurements in clouds are attainable with the filter-polychromator approach.

  5. Characterization and identification of contraband using UV resonant Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Lacey, Richard J.; Hayward, Ian P.; Sands, H. S.; Batchelder, David N.

    1997-02-01

    A range of explosives and narcotics have been examined using Raman spectroscopy with 244 nm excitation. This wavelength of excitation eliminates the fluorescence problems associated with excitation at visible wavelengths. Comparison with spectra obtained using visible excitation reveals that resonance Raman scattering is occurring. This results in simplified spectra, and enhanced Raman scattering efficiencies.

  6. Super-Resonant Intracavity Coherent Absorption

    PubMed Central

    Malara, P.; Campanella, C. E.; Giorgini, A.; Avino, S.; De Natale, P.; Gagliardi, G.

    2016-01-01

    The capability of optical resonators to extend the effective radiation-matter interaction length originates from a multipass effect, hence is intrinsically limited by the resonator’s quality factor. Here, we show that this constraint can be overcome by combining the concepts of resonant interaction and coherent perfect absorption (CPA). We demonstrate and investigate super-resonant coherent absorption in a coupled Fabry-Perot (FP)/ring cavity structure. At the FP resonant wavelengths, the described phenomenon gives rise to split modes with a nearly-transparent peak and a peak whose transmission is exceptionally sensitive to the intracavity loss. For small losses, the effective interaction pathlength of these modes is proportional respectively to the ratio and the product of the individual finesse coefficients of the two resonators. The results presented extend the conventional definition of resonant absorption and point to a way of circumventing the technological limitations of ultrahigh-quality resonators in spectroscopy and optical sensing schemes. PMID:27364475

  7. Super-Resonant Intracavity Coherent Absorption

    NASA Astrophysics Data System (ADS)

    Malara, P.; Campanella, C. E.; Giorgini, A.; Avino, S.; de Natale, P.; Gagliardi, G.

    2016-07-01

    The capability of optical resonators to extend the effective radiation-matter interaction length originates from a multipass effect, hence is intrinsically limited by the resonator’s quality factor. Here, we show that this constraint can be overcome by combining the concepts of resonant interaction and coherent perfect absorption (CPA). We demonstrate and investigate super-resonant coherent absorption in a coupled Fabry-Perot (FP)/ring cavity structure. At the FP resonant wavelengths, the described phenomenon gives rise to split modes with a nearly-transparent peak and a peak whose transmission is exceptionally sensitive to the intracavity loss. For small losses, the effective interaction pathlength of these modes is proportional respectively to the ratio and the product of the individual finesse coefficients of the two resonators. The results presented extend the conventional definition of resonant absorption and point to a way of circumventing the technological limitations of ultrahigh-quality resonators in spectroscopy and optical sensing schemes.

  8. Preventing Raman Lasing in High-Q WGM Resonators

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy; Matsko, Andrey; Strekalov, Dmitry; Maleki, Lute

    2007-01-01

    A generic design has been conceived to suppress the Raman effect in whispering- gallery-mode (WGM) optical resonators that have high values of the resonance quality factor (Q). Although it is possible to exploit the Raman effect (even striving to maximize the Raman gain to obtain Raman lasing), the present innovation is intended to satisfy a need that arises in applications in which the Raman effect inhibits the realization of the full potential of WGM resonators as frequency-selection components. Heretofore, in such applications, it has been necessary to operate high-Q WGM resonators at unattractively low power levels to prevent Raman lasing. (The Raman-lasing thresholds of WGM optical resonators are very low and are approximately proportional to Q(sup -2)). Heretofore, two ways of preventing Raman lasting at high power levels have been known, but both entail significant disadvantages: A resonator can be designed so that the optical field is spread over a relatively large mode volume to bring the power density below the threshold. For any given combination of Q and power level, there is certain mode volume wherein Raman lasing does not start. Unfortunately, a resonator that has a large mode volume also has a high spectral density, which is undesirable in a typical photonic application. A resonator can be cooled to the temperature of liquid helium, where the Raman spectrum is narrower and, therefore, the Raman gain is lower. However, liquid-helium cooling is inconvenient. The present design overcomes these disadvantages, making it possible to operate a low-spectral-density (even a single-mode) WGM resonator at a relatively high power level at room temperature, without risk of Raman lasing.

  9. Spatial correlation between chemical and topological defects in vitreous silica: UV-resonance Raman study

    SciTech Connect

    Saito, M. D’Amico, F.; Bencivenga, F.; Cucini, R.; Gessini, A.; Principi, E.; Masciovecchio, C.

    2014-06-28

    A spatial correlation between chemical and topological defects in the tetrahedron network in vitreous silica produced by a fusion process of natural quartz crystals was found by synchrotron-based UV resonance Raman experiments. Furthermore, a quantitative correlation between these defects was obtained by comparing visible Raman and UV absorption spectra. These results indicate that in vitreous silica produced by the fusion process the topological defects disturb the surrounding tetrahedral silica network and induce further disorder regions with sub nanometric sizes.

  10. Resonance Raman spectra of. cap alpha. -copper phthalocyanine

    SciTech Connect

    Bovill, A.J.; McConnell, A.A.; Nimmo, J.A.; Smith, W.E.

    1986-02-13

    Raman spectra of ..cap alpha..-copper phthalocyanine (..cap alpha..-CuPc) were recorded at room temperature and at 10 K with excitation wavelengths between 457 and 714 nm. Resonance enhancement was greatest for modes for which the largest displacements were on either the inner five-membered ring of the isoindole groups or the inner macrocycle and consequently assignment of the bands to modes of the entire molecule was possible by comparison with nickel octaethylporphyrin. Four out of five bands resonant in the Q band region and preresonant near the B band absorption region are totally symmetric modes. B band preresonance occurs more strongly with high-frequency modes. At low temperatures, multimode interactions are reduced and profiles were obtained which can be compared with solution profiles of porphyrins. Both Q/sub x/ and Q/sub y/ 0-0 scattering can be identified and a helper mode is evident. A term enhancement predominates, with B/sub 1g/ and B/sub 2g/ modes enhanced because of a Jahn-Teller distortion of the excited state. The resonance studies, together with electronic absorption spectra and published theoretical studies, confirm that the Q band in ..cap alpha..-CuPc is largely due to an allowed ..pi..-..pi..* transition associated mainly with the macrocycle and inner five-membered rings of the isoindole groups. 25 references, 5 figures, 2 tables.

  11. Relaxation mechanism of β-carotene from S2 (1Bu(+)) state to S1 (2Ag(-)) state: femtosecond time-resolved near-IR absorption and stimulated resonance Raman studies in 900-1550 nm region.

    PubMed

    Takaya, Tomohisa; Iwata, Koichi

    2014-06-12

    Carotenoids have two major low-lying excited states, the second lowest (S2 (1Bu(+))) and the lowest (S1 (2Ag(-))) excited singlet states, both of which are suggested to be involved in the energy transfer processes in light-harvesting complexes. Studying vibrational dynamics of S2 carotenoids requires ultrafast time-resolved near-IR Raman spectroscopy, although it has much less sensitivity than visible Raman spectroscopy. In this study, the relaxation mechanism of β-carotene from the S2 state to the S1 state is investigated by femtosecond time-resolved multiplex near-IR absorption and stimulated Raman spectroscopy. The energy gap between the S2 and S1 states is estimated to be 6780 cm(-1) from near-IR transient absorption spectra. The near-IR stimulated Raman spectrum of S2 β-carotene show three bands at 1580, 1240, and 1050 cm(-1). When excess energy of 4000 cm(-1) is added, the S1 C═C stretch band shows a large upshift with a time constant of 0.2 ps. The fast upshift is explained by a model that excess energy generated by internal conversion from the S2 state to the S1 state is selectively accepted by one of the vibronic levels of the S1 state and is redistributed among all the vibrational modes.

  12. Continuous-wave deep ultraviolet sources for resonance Raman explosive sensing

    NASA Astrophysics Data System (ADS)

    Yellampalle, Balakishore; Martin, Robert; Sluch, Mikhail; McCormick, William; Ice, Robert; Lemoff, Brian

    2015-05-01

    A promising approach to stand-off detection of explosive traces is using resonance Raman spectroscopy with Deepultraviolet (DUV) light. The DUV region offers two main advantages: strong explosive signatures due to resonant and λ- 4 enhancement of Raman cross-section, and lack of fluorescence and solar background. For DUV Raman spectroscopy, continuous-wave (CW) or quasi-CW lasers are preferable to high peak powered pulsed lasers because Raman saturation phenomena and sample damage can be avoided. In this work we present a very compact DUV source that produces greater than 1 mw of CW optical power. The source has high optical-to-optical conversion efficiency, greater than 5 %, as it is based on second harmonic generation (SHG) of a blue/green laser source using a nonlinear crystal placed in an external resonant enhancement cavity. The laser system is extremely compact, lightweight, and can be battery powered. Using two such sources, one each at 236.5 nm and 257.5 nm, we are building a second generation explosive detection system called Dual-Excitation-Wavelength Resonance-Raman Detector (DEWRRED-II). The DEWRRED-II system also includes a compact dual-band high throughput DUV spectrometer, and a highly-sensitive detection algorithm. The DEWRRED technique exploits the DUV excitation wavelength dependence of Raman signal strength, arising from complex interplay of resonant enhancement, self-absorption and laser penetration depth. We show sensor measurements from explosives/precursor materials at different standoff distances.

  13. UV resonance Raman sensing of pharmaceutical drugs in hollow fibers

    NASA Astrophysics Data System (ADS)

    Yan, D.; Popp, J.; Frosch, T.

    2014-05-01

    We report about the experimental combination of UV resonance Raman sensing (UV-RRS) and fiber enhanced Raman sensing (FERS) on pharmaceuticals. The results show that the chemical sensitivity is highly improved and at the same time the sample volume is reduced compared to conventional measurements. A hundreds-fold improvement of the limit of detection (LOD) has been achieved with the combination of resonance Raman enhancement and fiber enhancement. The enhanced Raman signal has a reliable linear relationship with the concentration of the analyte, and therefore shows great potential for quantitative analysis of pharmaceuticals.

  14. Subwavelength total acoustic absorption with degenerate resonators

    NASA Astrophysics Data System (ADS)

    Yang, Min; Meng, Chong; Fu, Caixing; Li, Yong; Yang, Zhiyu; Sheng, Ping

    2015-09-01

    We report the experimental realization of perfect sound absorption by sub-wavelength monopole and dipole resonators that exhibit degenerate resonant frequencies. This is achieved through the destructive interference of two resonators' transmission responses, while the matching of their averaged impedances to that of air implies no backscattering, thereby leading to total absorption. Two examples, both using decorated membrane resonators (DMRs) as the basic units, are presented. The first is a flat panel comprising a DMR and a pair of coupled DMRs, while the second one is a ventilated short tube containing a DMR in conjunction with a sidewall DMR backed by a cavity. In both examples, near perfect absorption, up to 99.7%, has been observed with the airborne wavelength up to 1.2 m, which is at least an order of magnitude larger than the composite absorber. Excellent agreement between theory and experiment is obtained.

  15. UV Resonant Raman Spectrometer with Multi-Line Laser Excitation

    NASA Technical Reports Server (NTRS)

    Lambert, James L.; Kohel, James M.; Kirby, James P.; Morookian, John Michael; Pelletier, Michael J.

    2013-01-01

    A Raman spectrometer employs two or more UV (ultraviolet) laser wavel engths to generate UV resonant Raman (UVRR) spectra in organic sampl es. Resonant Raman scattering results when the laser excitation is n ear an electronic transition of a molecule, and the enhancement of R aman signals can be several orders of magnitude. In addition, the Ra man cross-section is inversely proportional to the fourth power of t he wavelength, so the UV Raman emission is increased by another fact or of 16, or greater, over visible Raman emissions. The Raman-scatter ed light is collected using a high-resolution broadband spectrograph . Further suppression of the Rayleigh-scattered laser light is provi ded by custom UV notch filters.

  16. Resonance Raman enhancement optimization in the visible range by selecting different excitation wavelengths

    NASA Astrophysics Data System (ADS)

    Wang, Zhong; Li, Yuee

    2015-09-01

    Resonance enhancement of Raman spectroscopy (RS) has been used to significantly improve the sensitivity and selectivity of detection for specific components in complicated environments. Resonance RS gives more insight into the biochemical structure and reactivity. In this field, selecting a proper excitation wavelength to achieve optimal resonance enhancement is vital for the study of an individual chemical/biological ingredient with a particular absorption characteristic. Raman spectra of three azo derivatives with absorption spectra in the visible range are studied under the same experimental conditions at 488, 532, and 633 nm excitations. Universal laws in the visible range have been concluded by analyzing resonance Raman (RR) spectra of samples. The long wavelength edge of the absorption spectrum is a better choice for intense enhancement and the integrity of a Raman signal. The obtained results are valuable for applying RR for the selective detection of biochemical constituents whose electronic transitions take place at energies corresponding to the visible spectra, which is much friendlier to biologial samples compared to ultraviolet.

  17. Resonant Raman spectroscopy of PAH-Os self-assembled multilayers

    NASA Astrophysics Data System (ADS)

    Tognalli, N.; Fainstein, A.; Bonazzola, C.; Calvo, E.

    2004-01-01

    We present a resonant Raman scattering study of (PAH-Os/PVS)n and (PAH-Os/GOx)m self-assembled multilayers (n=1-11 and m=1-3). These Os polymer multilayers can be used in electrodes as efficient molecular wires for biomolecular recognition. The Raman intensity dependence on the number of self-assembly cycles provides information on the deposition process. The spectra are identical to that observed for PAH-Os in aqueous solution, indicating that the PAH-Os metal complex structure is conserved in the multilayers. We observe at ˜500 nm incoming and outgoing Raman resonances of osmium and bipyridine vibrational modes. These resonances are associated to the metal-to-ligand charge transfer (MLCT) transition. We study the evolution of these Raman modes as a function of the Os oxidation state during in situ electrochemistry. During the oxidation process, Os(II)→Os(III), the Raman resonance related to the MLCT disappears and the bipyridine related modes harden by ˜10 cm-1. These results are correlated with optical transmission measurements which show the disappearance of the visible region absorption when the Os complex is oxidized. We also find partial quenching of the Raman mode intensity after in situ voltamperometric cycles which demonstrates the existence of photo-electro-chemical processes.

  18. Resonant Raman spectroscopy of PAH--Os self-assembled multilayers.

    PubMed

    Tognalli, N; Fainstein, A; Bonazzola, C; Calvo, E

    2004-01-22

    We present a resonant Raman scattering study of (PAH--Os/PVS)n and (PAH--Os/GOx)m self-assembled multilayers (n=1-11 and m=1-3). These Os polymer multilayers can be used in electrodes as efficient molecular wires for biomolecular recognition. The Raman intensity dependence on the number of self-assembly cycles provides information on the deposition process. The spectra are identical to that observed for PAH--Os in aqueous solution, indicating that the PAH--Os metal complex structure is conserved in the multilayers. We observe at approximately 500 nm incoming and outgoing Raman resonances of osmium and bipyridine vibrational modes. These resonances are associated to the metal-to-ligand charge transfer (MLCT) transition. We study the evolution of these Raman modes as a function of the Os oxidation state during in situ electrochemistry. During the oxidation process, Os(II)-->Os(III), the Raman resonance related to the MLCT disappears and the bipyridine related modes harden by approximately 10 cm(-1). These results are correlated with optical transmission measurements which show the disappearance of the visible region absorption when the Os complex is oxidized. We also find partial quenching of the Raman mode intensity after in situ voltamperometric cycles which demonstrates the existence of photo-electro-chemical processes.

  19. Versatility of heme coordination demonstrated in a fungal peroxidase. Absorption and resonance Raman studies of Coprinus cinereus peroxidase and the Asp245-->Asn mutant at various pH values.

    PubMed

    Smulevich, G; Neri, F; Marzocchi, M P; Welinder, K G

    1996-08-13

    The pH dependence of the electronic absorption and resonance Raman (RR) spectra of FeIII and FeII forms of Coprinus cinereus peroxidase (CIP) and its Asp245-->Asn (D245N) mutant has been examined in detail. The spectral data were obtained in the pH range 3.8-12.0. These spectra were used to assess the spin and ligation states of the heme via the porphyrin marker band frequencies and the wavelengths of the absorption maxima, especially that of the band (CT1) due to the charge transfer from the porphyrin to the heme iron via the a' 2u(pi)-->eg (d pi) electronic transition. The RR spectra were obtained by using different excitation wavelengths and polarized light. The data obtained for ferric CIP show that two pH-induced structural transitions exist. At acid pH the Soret and the CT1 absorption maxima occur at 394 and 652 nm, respectively, compared with the values of 403 and 649 nm observed at neutral pH. The electronic data indicate that at acid pH the proximal Fe-Im bond might be weakened or ruptured, and the RR spectra show a new species (5-c HS) different from the normal neutral 5-coordinate high-spin (5-c HS) heme. At pH 12.0, the protein converts to a 6-coordinate low-spin (6-c LS) heme with a hydroxyl ligand coordinated in the sixth position of the heme iron and strongly hydrogen-bonded with the positively charged guanidinium group of the distal Arg51 residue. Replacement of the aspartate carboxylate group of Asp245, which acts as hydrogen-bond acceptor to the proximal His183 ligand of the heme Fe, with a carboxamide group of an asparagine residue has a profound influence on the heme coordination. The RR spectra of the Fe(II) form of this mutant at both neutral and alkaline pH values show a band at 204 cm-1 assigned to the Fe-His stretch associated with a fairly weak or non-hydrogen-bonded imidazole. The ferric form of the mutant shows a great variability in coordination and spin states upon pH titration. Between pH 8.8 and 3.8 the spectra are mainly

  20. Suppression of the four-wave mixing amplification via Raman absorption

    NASA Astrophysics Data System (ADS)

    Romanov, Gleb; O'Brien, Chris; Novikova, Irina

    2016-11-01

    We propose a method to controllably suppress the effect of the four-wave mixing caused by the coupling of the strong control optical field to both optical transitions in the ? system under the conditions of electromagnetically induced transparency (EIT). At sufficiently high atomic density, this process leads to amplification of a weak optical signal field, that is detrimental for the fidelity of any EIT-based quantum information applications. Here we show that an additional absorption resonance centred around the Stokes field frequency, generated in such a four-wave mixing process, may efficiently suppress the unwanted probe amplification without affecting properties of the EIT interaction. We discuss the possibility of creating such tunable absorption using two-photon Raman absorption resonances in the other Rb isotope, and present some preliminary experimental results.

  1. Remote sensing of the atmosphere by resonance Raman LIDAR

    SciTech Connect

    Sedlacek, A.J.; Harder, D.; Leung, K.P.; Zuhoski, P.B. Jr.; Burr, D.; Chen, C.L.

    1994-12-01

    When in resonance, Raman scattering exhibits strong enhancement ranging from four to six orders of magnitude. This physical phenomenon has been applied to remote sensing of the Earth`s atmosphere. With a 16 inch Cassegrain telescope and spectrometer/ CCD-detector system, 70-150 ppm-m of SO{sub 2} in the atmosphere has been detected at a distance of 0.5 kilometer. This system can be used to detect/monitor chemical effluence in the atmosphere by their unique Raman fingerprints. Experimental result together with detailed resonance Raman and atmospheric laser propagation effects will be discussed.

  2. Application of resonance Raman LIDAR for chemical species identification

    SciTech Connect

    Chen, C.L.; Heglund, D.L.; Ray, M.D.; Harder, D.; Dobert, R.; Leung, K.P.; Wu, M.; Sedlacek, A.

    1997-07-01

    BNL has been developing a remote sensing technique for the detection of atmospheric pollutants based on the phenomenon of resonance Raman LIDAR that has also incorporated a number of new techniques/technologies designed to extend it`s performance envelope. When the excitation frequency approaches an allowed electronic transition of the molecule, an enormous enhancement of the inelastic scattering cross-section can occur, often up to 2 to 4 orders-of-magnitude, and is referred to as resonance Raman (RR), since the excitation frequency is in resonance with an allowed electronic transition. Exploitation of this enhancement along with new techniques such as pattern recognition algorithms to take advantage of the spectral fingerprint and a new laser frequency modulation technique designed to suppress broadband fluorescence, referred to as Frequency modulated Excitation Raman Spectroscopy (FreMERS) and recent developments in liquid edge filter technology, for suppression of the elastic channel, all help increase the overall performance of Raman LIDAR.

  3. Quantitative detection of astaxanthin and cantaxanthin in Atlantic salmon by resonance Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Ermakov, Igor V.; Ermakova, Maia R.; Gellermann, Werner

    2006-02-01

    Two major carotenoids species found in salmonids muscle tissues are astaxanthin and cantaxanthin. They are taken up from fish food and are responsible for the attractive red-orange color of salmon filet. Since carotenoids are powerful antioxidants and biomarkers of nutrient consumption, they are thought to indicate fish health and resistance to diseases in fish farm environments. Therefore, a rapid, accurate, quantitative optical technique for measuring carotenoid content in salmon tissues is of economic interest. We demonstrate the possibility of using fast, selective, quantitative detection of astaxanthin and cantaxanthin in salmon muscle tissues, employing resonance Raman spectroscopy. Analyzing strong Raman signals originating from the carbon-carbon double bond stretch vibrations of the carotenoid molecules under blue laser excitation, we are able to characterize quantitatively the concentrations of carotenoids in salmon muscle tissue. To validate the technique, we compared Raman data with absorption measurements of carotenoid extracts in acetone. A close correspondence was observed in absorption spectra for tissue extract in acetone and a pure astaxanthin solution. Raman results show a linear dependence between Raman and absorption data. The proposed technique holds promise as a method of rapid screening of carotenoid levels in fish muscle tissues and may be attractive for the fish farm industry to assess the dietary status of salmon, risk for infective diseases, and product quality control.

  4. Raman Lasing and Cavity Resonances in Water Micro-Droplets: Possible Effects on Shortwave Cloud Forcing

    NASA Astrophysics Data System (ADS)

    Cappa, C. D.; Wilson, K. R.; Messer, B. M.; Cohen, R. C.; Saykally, R. J.

    2003-12-01

    The influence of narrow optical resonances, which result from trapping of light rays via total internal reflection in water droplets, on the absorption of shortwave (SW) solar radiation has been characterized through high resolution Mie scattering calculations. Our results indicate that these resonances engender an increase in absorption of solar radiation by cloud droplets by several W/m2 above the linear direct absorption process in the range 0.3-1.1 μ m. This work suggests that Mie scattering calculations performed at the 0.1x (x = 2π r/λ ) resolution typically implemented in cloudy sky radiative transfer models may not be sufficient to correctly model SW absorption, consistent with the recent finding of Nussenveig [2003]. Stimulated Raman scattering experiments on pure water microdroplets yield cavity enhancements in general agreement with the Mie theory results.

  5. Periodontitis diagnostics using resonance Raman spectroscopy on saliva

    NASA Astrophysics Data System (ADS)

    Gonchukov, S.; Sukhinina, A.; Bakhmutov, D.; Biryukova, T.; Tsvetkov, M.; Bagratashvily, V.

    2013-07-01

    In view of its wealth of molecular information, Raman spectroscopy has been the subject of active biomedical research. The aim of this work is Raman spectroscopy (RS) application for the determination of molecular biomarkers in saliva with the objective of early periodontitis detection. As was shown in our previous study, carotenoids contained in saliva can be molecular fingerprint information for the periodontitis level. It is shown here that the carotenoid RS lines at wavenumbers of 1156 and 1524 cm-1 can be easily detected and serve as reliable biomarkers of periodontitis using resonance Raman spectroscopy of dry saliva.

  6. Resonance raman spectroscopy of an ultraviolet-sensitive insect rhodopsin

    SciTech Connect

    Pande, C.; Deng, H.; Rath, P.; Callender, R.H.; Schwemer, J.

    1987-11-17

    The authors present the first visual pigment resonance Raman spectra from the UV-sensitive eyes of an insect, Ascalaphus macaronius (owlfly). This pigment contains 11-cis-retinal as the chromophore. Raman data have been obtained for the acid metarhodopsin at 10/sup 0/C in both H/sub 2/O and D/sub 2/O. The C=N stretching mode at 1660 cm/sup -1/ in H/sub 2/O shifts to 1631 cm/sup -1/ upon deuteriation of the sample, clearly showing a protonated Schiff base linkage between the chromophore and the protein. The structure-sensitive fingerprint region shows similarities to the all-trans-protonated Schiff base of model retinal chromophores, as well as to the octopus acid metarhodopsin and bovine metarhodopsin I. Although spectra measured at -100/sup 0/C with 406.7-nm excitation, to enhance scattering from rhodopsin (lambda/sub max/ 345 nm), contain a significant contribution from a small amount of contaminants (cytochrome(s) and/or accessory pigment) in the sample, the C=N stretch at 1664 cm/sup -1/ suggests a protonated Schiff base linkage between the chromophore and the protein in rhodopsin as well. For comparison, this mode also appears at approx. 1660 cm/sup -1/ in both the vertebrate (bovine) and the invertebrate (octopus) rhodopsins. These data are particularly interesting since the absorption maximum of 345 nm for rhodopsin might be expected to originate from an unprotonated Schiff base linkage. That the Schiff base linkage in the owlfly rhodopsin, like in bovine and in octopus, is protonated suggests that a charged chromophore is essential to visual transduction.

  7. Dependence of Raman and absorption spectra of stacked bilayer MoS2 on the stacking orientation.

    PubMed

    Park, Seki; Kim, Hyun; Kim, Min Su; Han, Gang Hee; Kim, Jeongyong

    2016-09-19

    Stacked bilayer molybdenum disulfide (MoS2) exhibits interesting physical properties depending on the stacking orientation and interlayer coupling strength. Although optical properties, such as photoluminescence, Raman, and absorption properties, are largely dependent on the interlayer coupling of stacked bilayer MoS2, the origin of variations in these properties is not clearly understood. We performed comprehensive confocal Raman and absorption mapping measurements to determine the dependence of these spectra on the stacking orientation of bilayer MoS2. The results indicated that with 532-nm laser excitation, the Raman scattering intensity gradually increased upon increasing the stacking angle from 0° to 60°, whereas 458-nm laser excitation resulted in the opposite trend of decreasing Raman intensity with increasing stacking angle. This opposite behavior of the Raman intensity dependence was explained by the varying resonance condition between the Raman excitation wavelength and C exciton absorption energy of bilayer MoS2. Our work sheds light on the intriguing effect of the subtle interlayer interaction in stacked MoS2 bilayers on the resulting optical properties.

  8. Dependence of Raman and absorption spectra of stacked bilayer MoS2 on the stacking orientation.

    PubMed

    Park, Seki; Kim, Hyun; Kim, Min Su; Han, Gang Hee; Kim, Jeongyong

    2016-09-19

    Stacked bilayer molybdenum disulfide (MoS2) exhibits interesting physical properties depending on the stacking orientation and interlayer coupling strength. Although optical properties, such as photoluminescence, Raman, and absorption properties, are largely dependent on the interlayer coupling of stacked bilayer MoS2, the origin of variations in these properties is not clearly understood. We performed comprehensive confocal Raman and absorption mapping measurements to determine the dependence of these spectra on the stacking orientation of bilayer MoS2. The results indicated that with 532-nm laser excitation, the Raman scattering intensity gradually increased upon increasing the stacking angle from 0° to 60°, whereas 458-nm laser excitation resulted in the opposite trend of decreasing Raman intensity with increasing stacking angle. This opposite behavior of the Raman intensity dependence was explained by the varying resonance condition between the Raman excitation wavelength and C exciton absorption energy of bilayer MoS2. Our work sheds light on the intriguing effect of the subtle interlayer interaction in stacked MoS2 bilayers on the resulting optical properties. PMID:27661893

  9. Proliferation detection using a remote resonance Raman chemical sensor

    SciTech Connect

    Sedlacek, A.J.; Chen, C.L.; Dougherty, D.R.

    1993-08-01

    The authors discussed the potential of the resonance Raman chemical sensor as a remote sensor that can be used for gases, liquids or solids. This spectroscopy has the fundamental advantage that it is based on optical fingerprints that are insensitive to environmental perturbations or excitation frequency. By taking advantage of resonance enhancement, the inelastic scattering cross-section can increase anywhere from 4 to 6 orders of magnitude which translates into increased sensing range or lower detection limits. It was also shown that differential cross-sections as small as 10{sup {minus}27} cm{sup 2}/sr do not preclude the use of this technique as being an important component in one`s remote-sensing arsenal. The results obtained in the early 1970s on various pollutants and the more recent work on atmospheric water cast a favorable light on the prospects for the successful development of a resonance Raman remote sensor. Currently, of the 20 CW agent-related {open_quotes}signature{close_quotes} chemicals that the authors have investigated, 18 show enhancements ranging from 3 to 6 orders of magnitude. The absolute magnitudes of the measured resonance enhanced Raman cross-sections for these 18 chemicals suggest that detection and identification of trace quantities of the {open_quotes}signature{close_quotes} chemicals, through a remote resonance Raman chemical sensor, could be achieved.

  10. Proliferation detection using a remote resonance Raman chemical sensor

    SciTech Connect

    Sedlacek, A.J.; Chen, C.L.; Dougherty, D.R.

    1993-12-31

    The authors discuss the potential of the resonance Raman chemical sensor as a remote sensor that can be used for gases, liquids or solids. This spectroscopy has the fundamental advantage that it is based on optical fingerprints that are insensitive to environmental perturbations or excitation frequency. By taking advantage of resonance enhancement, the inelastic scattering cross-section can increase anywhere from 4 to 6 orders of magnitude which translates into increased sensing range or lower detection limits. It was also shown that differential cross-sections as small as 10{sup {minus}27} cm{sup 2}/sr do not preclude the use of this technique as being an important component in one`s remote-sensing arsenal. The results obtained in the early 1970s on various pollutants and the more recent work on atmospheric water cast a favorable light on the prospects for the successful development of a resonance Raman remote sensor. Currently, of the 20 CW agent-related ``signature`` chemicals that the authors have investigated, 18 show enhancements ranging from 3 to 6 orders of magnitude. The absolute magnitudes of the measured resonance enhanced Raman cross-sections for these 18 chemicals suggest that detection and identification of trace quantities of the ``signature`` chemicals, through a remote resonance Raman chemical sensor, could be achieved.

  11. Vibrational analysis of hydroxyflavylium derivatives by IR, Fourier transform Raman and resonance Raman spectroscopies

    NASA Astrophysics Data System (ADS)

    Merlin, J. C.; Cornard, J. P.; Stastoua, A.; Saidi-Idrissi, M.; Lautie, M. F.; Brouillard, R.

    In order to give a better insight into the vibrational properties of anthocyanins, the synthesis and the vibrational studies of some hydroxyflavylium derivatives with a controlled substitution pattern have been performed. The IR, Raman and resonance Raman spectra of the investigated hydroxyflavylium compounds have been recorded in the solid and solution states. A number of lines have been assigned on the basis of deuterium isotopic shifts, resonance enhancement and previous studies on parent compounds. An attempt has been made to analyze the influence of hydroxy substituents on vibrational properties of the investigated flavylium cations.

  12. Exploitation of resonance Raman spectroscopy as a remote chemical sensor

    SciTech Connect

    Sedlacek, A.J.; Chen, C.L.

    1995-08-01

    We have discussed recent experimental results using a resonance-Raman-based LIDAR system as a remote chemical sensor. This spectroscopy has the fundamental advantage that it is based on optical fingerprints that are insensitive to environmental perturbations. By taking advantage of resonance enhancement, which 6 orders-of-magnitude, can be as large as 4 to an increased sensing range for a given chemical concentration or lower detection limit for a given stand-off distance can be realized. The success discussed above can in part be traced back to the use of new state-of-the-art technologies which, only recently, have allowed the phenomenon of resonance-enhanced Raman spectroscopy to be fully exploited as a remote chemical sensor platform. Since many chemicals have electronic transitions in the UV/IS, it is expected that many will have pronounced resonance enhancements.

  13. β-Carotene Revisited by Transient Absorption and Stimulated Raman Spectroscopy.

    PubMed

    Quick, Martin; Kasper, Marc-André; Richter, Celin; Mahrwald, Rainer; Dobryakov, Alexander L; Kovalenko, Sergey A; Ernsting, Nikolaus P

    2015-12-21

    β-Carotene in n-hexane was examined by femtosecond transient absorption and stimulated Raman spectroscopy. Electronic change is separated from vibrational relaxation with the help of band integrals. Overlaid on the decay of S1 excited-state absorption, a picosecond process is found that is absent when the C9 -methyl group is replaced by ethyl or isopropyl. It is attributed to reorganization on the S1 potential energy surface, involving dihedral angles between C6 and C9 . In Raman studies, electronic states S2 or S1 were selected through resonance conditions. We observe a broad vibrational band at 1770 cm(-1) in S2 already. With 200 fs it decays and transforms into the well-known S1 Raman line for an asymmetric C=C stretching mode. Low-frequency activity (<800 cm(-1) ) in S2 and S1 is also seen. A dependence of solvent lines on solute dynamics implies intermolecular coupling between β-carotene and nearby n-hexane molecules. PMID:26433210

  14. UV resonance Raman analysis of trishomocubane and diamondoid dimers

    SciTech Connect

    Meinke, Reinhard Thomsen, Christian; Maultzsch, Janina; Richter, Robert; Merli, Andrea; Fokin, Andrey A.; Koso, Tetyana V.; Schreiner, Peter R.; Rodionov, Vladimir N.

    2014-01-21

    We present resonance Raman measurements of crystalline trishomocubane and diamantane dimers containing a C=C double bond. Raman spectra were recorded with excitation energies between 2.33 eV and 5.42 eV. The strongest enhancement is observed for the C=C stretch vibration and a bending mode involving the two carbon atoms of the C=C bond, corresponding to the B{sub 2g} wagging mode of ethylene. This is associated with the localization of the π-HOMO and LUMO and the elongation of the C=C bond length and a pyramidalization of the two sp{sup 2}-hybridized carbon atoms at the optical excitation. The observed Raman resonance energies of the trishomocubane and diamantane dimers are significantly lower than the HOMO-LUMO gaps of the corresponding unmodified diamondoids.

  15. Deep UV Resonance Raman Spectroscopy for Characterizing Amyloid Aggregation.

    PubMed

    Handen, Joseph D; Lednev, Igor K

    2016-01-01

    Deep UV resonance Raman spectroscopy is a powerful technique for probing the structure and formation mechanism of protein fibrils, which are traditionally difficult to study with other techniques owing to their low solubility and noncrystalline arrangement. Utilizing a tunable deep UV Raman system allows for selective enhancement of different chromophores in protein fibrils, which provides detailed information on different aspects of the fibrils' structure and formation. Additional information can be extracted with the use of advanced data treatment such as chemometrics and 2D correlation spectroscopy. In this chapter we give an overview of several techniques for utilizing deep UV resonance Raman spectroscopy to study the structure and mechanism of formation of protein fibrils. Clever use of hydrogen-deuterium exchange can elucidate the structure of the fibril core. Selective enhancement of aromatic amino acid side chains provides information about the local environment and protein tertiary structure. The mechanism of protein fibril formation can be investigated with kinetic experiments and advanced chemometrics.

  16. Resonant enhancement of absorption in the superlens

    NASA Astrophysics Data System (ADS)

    Alekseyev, Leonid; Jacob, Zubin; Narimanov, Evgenii

    2007-03-01

    The Veselago lens (also known as the super lens) [1], which is a slab made of left handed material with ɛ=-1 and μ=-1 has interesting properties like perfect lensing [2] and cloaking [3]. When a source is placed in front of it there are regions of high field intensity in such a lens , known as anomalously localized resonant regions [3]. For practical applications of the superlens taking advantage of these properties, the effect of finite loss on the device performance is critical [4] . We calculate the absorption loss of dipole radiation by an ɛ<0 and μ<0 slab and find resonant enhancement of absorption in the superlensing regime. [1] V. G. Veselago, ``The electrodynamics of substances with simultaneously negative values of permittivity and permeability,'' Sov. Phys. Usp. 10, 509 (1968). [2] J. B. Pendry, ``Negative refraction makes a perfect lens,'' Phys. Rev. Lett. 85, 3966-3969 (2000). [3] Graeme W. Milton and Nicolae-Alexandry P. Nicorovici ``On the cloaking effects associated with anomalous localized resonance,'' Proc. R. Soc. A (2006) 462, 3027-3059. [4] V. A. Podolskiy and E. E. Narimanov, ``Near-sighted superlens,'' Opt. Lett. 30, 75-77 (2005)

  17. Electron heating due to resonant absorption

    SciTech Connect

    Mizuno, K.; Spielman, R.B.; DeGroot, J.S.; Bollen, W.M.

    1980-01-01

    Intense, p-polarized microwaves (v/sub os//v/sub eo-/<1) are incident on an imhomogeneous plasma (10/sup 2/resonant absorption near the critical surface (where the plasma frequency equals microwave frequency). Suprathermal electrons are heated by resonantly driven electrostatic field to produce a hot Maxwellian distribution. Most of the heated electrons flow towards the overdense region and are absorbed by the anode at the far end of the overdense region. At high power (v/sub os//v/sub eo-/>0.2), strong heating of thermal electrons, large amplitude ion acoustic turbulence, and a self-consistent dc electric field are observed near the critical surface. This dc electric field is enhanced by applying a weak magnetic field (..omega../sub ce//..omega../sub o/ approx. = 10/sup -2/).

  18. Probing non-adiabatic conical intersections using absorption, spontaneous Raman, and femtosecond stimulated Raman spectroscopy

    SciTech Connect

    Patuwo, Michael Y.; Lee, Soo-Y.

    2013-12-21

    We present the time-frame calculated photoabsorption spectrum (ABS), spontaneous Raman excitation profile (REP), femtosecond stimulated Raman spectroscopy (FSRS) spectrum, and femtosecond stimulated Raman excitation profile (FSREP) results of a two-mode and three-mode, three-electronic-states model Hamiltonians containing conical intersections (CIs) along its two upper diabatic electronic states, e{sub 1} (dark) and e{sub 2} (bright), with and without coupling (nonadiabatic dynamics) along an asymmetric mode. For every electronic state in each model, there is one coupling mode and the rest of the modes are symmetric tuning modes. The CI appears in the Hamiltonian as off-diagonal entries to the potential term that couple the two upper states, in the form of a linear function of the coupling mode. We show that: (a) the ABS, REP, and FSREP for Stokes and anti-Stokes lines contain similar information about the e{sub 1} and e{sub 2} vibrational bands, (b) the FSRS spectra feature narrow stationary peaks and broader moving peaks contributed by the different resonant components of the third-order polarization terms from perturbation theory, and (c) a relatively strong and narrow stationary band of the allowed first overtone of the asymmetric coupling mode is observed in the Stokes FSREP in the e{sub 1} energy region with coupling to e{sub 2}.

  19. Resonance electronic Raman scattering in rare earth crystals

    SciTech Connect

    Williams, G.M.

    1988-11-10

    The intensities of Raman scattering transitions between electronic energy levels of trivalent rare earth ions doped into transparent crystals were measured and compared to theory. A particle emphasis was placed on the examination of the effect of intermediate state resonances on the Raman scattering intensities. Two specific systems were studied: Ce/sup 3 +/(4f/sup 1/) in single crystals of LuPO/sub 4/ and Er/sup 3 +/(4f/sup 11/) in single crystals of ErPO/sub 4/. 134 refs., 92 figs., 33 tabs.

  20. Laser engines operating by resonance absorption.

    PubMed

    Garbuny, M; Pechersky, M J

    1976-05-01

    The coherence properties and power levels of lasers available at present lend themselves to the remote operation of mechanical engines by resonance absorption in a working gas. Laser radiation is capable of producing extremely high temperatures in a gas. Limits to the achievable temperatures in the working gas of an engine are imposed by the solid walls and by loss of resonance absorption due to thermal saturation, bleaching, and dissociation. However, it is shown that by proper control of the laser beam in space, time, and frequency, as well as by choice of the absorbing gas, these limits are to a great extent removed so that very high temperatures are indeed attainable. The working gas is largely monatomic, preferably helium with the addition of a few volume percent of an absorber. Such a gas mixture, internally heated, permits an optimization of the expansion ratio, with resulting thermal efficiencies and work ratios, not achievable in conventional engines. A relationship between thermal efficiency and work ratio is derived that is quite general for the optimization condition. The performance of laser piston engines, turbines, and the Stirling cycle based on these principles is discussed and compared with conventional engine operation. Finally, a brief discussion is devoted to the possibility and concepts for the direct conversion of selective vibrational or electronic excitation into mechanical work, bypassing the translational degrees of freedom. PMID:20165143

  1. Laser engines operating by resonance absorption.

    PubMed

    Garbuny, M; Pechersky, M J

    1976-05-01

    The coherence properties and power levels of lasers available at present lend themselves to the remote operation of mechanical engines by resonance absorption in a working gas. Laser radiation is capable of producing extremely high temperatures in a gas. Limits to the achievable temperatures in the working gas of an engine are imposed by the solid walls and by loss of resonance absorption due to thermal saturation, bleaching, and dissociation. However, it is shown that by proper control of the laser beam in space, time, and frequency, as well as by choice of the absorbing gas, these limits are to a great extent removed so that very high temperatures are indeed attainable. The working gas is largely monatomic, preferably helium with the addition of a few volume percent of an absorber. Such a gas mixture, internally heated, permits an optimization of the expansion ratio, with resulting thermal efficiencies and work ratios, not achievable in conventional engines. A relationship between thermal efficiency and work ratio is derived that is quite general for the optimization condition. The performance of laser piston engines, turbines, and the Stirling cycle based on these principles is discussed and compared with conventional engine operation. Finally, a brief discussion is devoted to the possibility and concepts for the direct conversion of selective vibrational or electronic excitation into mechanical work, bypassing the translational degrees of freedom.

  2. Resonance Raman Scattering of Rhodamine 6G as Calculated Using Time-Dependent Density Functional Theory

    SciTech Connect

    Jensen, Lasse; Schatz, George C.

    2006-03-27

    The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. In this work, we present the first calculation of the resonance Raman scattering (RRS) spectrum of rhodamine 6G (R6G) which is a prototype molecule in surface-enhanced Raman scattering (SERS). The calculation is done using a recently developed time-dependent density functional theory (TDDFT) method, which uses a short-time approximation to evaluate the Raman scattering cross section. The normal Raman spectrum calculated with this method is in good agreement with experimental results. The calculated RRS spectrum shows qualitative agreement with SERS results at a wavelength that corresponds to excitation of the S1 state, but there are significant differences with the measured RRS spectrum at wavelengths that correspond to excitation of the vibronic sideband of S1. Although the agreement with the experiments is not perfect, the results provide insight into the RRS spectrum of R6G at wavelengths close to the absorption maximum where experiments are hindered due to strong fluorescence. The calculated resonance enhancements are found to be on the order of 105. This indicates that a surface enhancement factor of about 1010 would be required in SERS in order to achieve single-molecule detection of R6G.

  3. Ultraviolet resonance Raman spectroscopy of explosives in solution and the solid state.

    PubMed

    Emmons, Erik D; Tripathi, Ashish; Guicheteau, Jason A; Fountain, Augustus W; Christesen, Steven D

    2013-05-23

    Resonance Raman cross sections of common explosives have been measured by use of excitation wavelengths in the deep-UV from 229 to 262 nm. These measurements were performed both in solution and in the native solid state for comparison. While measurements of UV Raman cross sections in solution with an internal standard are straightforward and commonly found in the literature, measurements on the solid phase are rare. This is due to the difficulty in preparing a solid sample in which the molecules of the internal standard and absorbing analyte/explosive experience the same laser intensity. This requires producing solid samples that are mixtures of strongly absorbing explosives and an internal standard transparent at the UV wavelengths used. For the solid-state measurements, it is necessary to use nanostructured mixtures of the explosive and the internal standard in order to avoid this bias due to the strong UV absorption of the explosive. In this study we used a facile spray-drying technique where the analyte of interest was codeposited with the nonresonant standard onto an aluminum-coated microscope slide. The generated resonance enhancement profiles and quantitative UV-vis absorption spectra were then used to plot the relative Raman return as a function of excitation wavelength and particle size.

  4. Raman resonance in iron-based superconductors: The magnetic scenario

    NASA Astrophysics Data System (ADS)

    Hinojosa, Alberto; Cai, Jiashen; Chubukov, Andrey V.

    2016-02-01

    We perform theoretical analysis of polarization-sensitive Raman spectroscopy on NaFe1 -xCoxAs , EuFe 2 As2 , SrFe2As2 , and Ba (Fe1 -xCox )2As2 , focusing on two features seen in the B1 g symmetry channel (in one Fe unit cell notation): the strong temperature dependence of the static, uniform Raman response in the normal state and the existence of a collective mode in the superconducting state. We show that both features can be explained by the coupling of fermions to pairs of magnetic fluctuations via the Aslamazov-Larkin process. We first analyze magnetically mediated Raman intensity at the leading two-loop order and then include interactions between pairs of magnetic fluctuations. We show that the full Raman intensity in the B1 g channel can be viewed as the result of the coupling of light to Ising-nematic susceptibility via Aslamazov-Larkin process. We argue that the singular temperature dependence in the normal state is the combination of the temperature dependencies of the Aslamazov-Larkin vertex and of Ising-nematic susceptibility. We discuss two scenario for the resonance below Tc. One is the resonance due to development of a pole in the fully renormalized Ising-nematic susceptibility. Another is orbital excitonic scenario, in which spin fluctuations generate attractive interaction between low-energy fermions.

  5. Resonant electronic Raman scattering: A BCS-like system

    NASA Astrophysics Data System (ADS)

    Rodrigues, Leonarde N.; Arantes, A.; Schüller, C.; Bell, M. J. V.; Anjos, V.

    2016-05-01

    In this paper we investigate the resonant intersubband Raman scattering of two-dimensional electron systems in GaAs-AlGaAs single quantum wells. Self-consistent calculations of the polarized and depolarized Raman cross sections show that the appearance of excitations at the unrenormalized single-particle energy are related to three factors: the extreme resonance regime, the existence of degeneracy in intersubband excitations of the electron gas, and, finally, degeneracy in the interactions between pairs of excitations. It is demonstrated that the physics that governs the problem is similar to the one that gives rise to the formation of the superconducting state in the BCS theory of normal metals. Comparison between experiment and theory shows an excellent agreement.

  6. Disorder-induced double resonant Raman process in graphene

    NASA Astrophysics Data System (ADS)

    Rodriguez-Nieva, J. F.; Barros, E. B.; Saito, R.; Dresselhaus, M. S.

    2014-12-01

    An analytical study is presented of the double resonant Raman scattering process in graphene, responsible for the D and D' features in the Raman spectra. This work yields analytical expressions for the D and D' integrated Raman intensities that explicitly show the dependencies on laser energy, defect concentration, and electronic lifetime. Good agreement is obtained between the analytical results and experimental measurements on samples with increasing defect concentrations and at various laser excitation energies. The use of Raman spectroscopy to identify the nature of defects is discussed. Comparison between the models for the edge-induced and the disorder-induced D-band intensity suggests that edges or grain boundaries can be distinguished from disorder by the different dependence of their Raman intensity on laser excitation energy. Similarly, the type of disorder can potentially be identified not only by the intensity ratio ID/ID' , but also by its laser energy dependence. Also discussed is a quantitative analysis of quantum interference effects of the graphene wave functions, which determine the most important phonon wave vectors and scattering processes responsible for the D and D' bands.

  7. Resonance Raman Optical Activity of Single Walled Chiral Carbon Nanotubes.

    PubMed

    Nagy, Péter R; Koltai, János; Surján, Péter R; Kürti, Jenő; Szabados, Ágnes

    2016-07-21

    Resonance (vibrational) Raman Optical Activity (ROA) spectra of six chiral single-walled carbon nanotubes (SWCNTs) are studied by theoretical means. Calculations are performed imposing line group symmetry. Polarizability tensors, computed at the π-electron level, are differentiated with respect to DFT normal modes to generate spectral intensities. This computational protocol yields a ROA spectrum in good agreement with the only experiment on SWCNT, available at present. In addition to the conventional periodic electric dipole operator we introduce magnetic dipole and electric quadrupole operators, suitable for conventional k-space calculations. Consequences of the complex nature of the wave function on the scattering cross section are discussed in detail. The resonance phenomenon is accounted for by the short time approximation. Involvement of fundamental vibrations in the region of the intermediate frequency modes is found to be more notable in ROA than in Raman spectra. Calculations indicate exceptionally strong resonance enhancement of SWCNT ROA signals. Resonance ROA profile of the (6,5) tube shows an interesting sign change that may be exploited experimentally for SWCNT identification. PMID:27315548

  8. Enhanced Raman sensitivity using an actively stabilized external resonator

    NASA Astrophysics Data System (ADS)

    Taylor, David J.; Glugla, Manfred; Penzhorn, Ralf-Dieter

    2001-04-01

    An enhancement up to 250-fold in laser Raman signals for real-time gas analysis has been achieved within an actively stabilized external resonator (ASER), whose length is actively matched to the single-frequency excitation laser using the Pound-Drever technique. With the Raman cell present, enhancements up to 50-fold are achieved, and the resulting detection limit for hydrogen in ambient-pressure gas mixtures is about ten parts-per-million in a 1 min analysis period at unity signal-to-noise ratio. Based upon the recent development of a fiber-pumped Nd:YVO4 laser with single-frequency output exceeding 5 W at 532 nm, this highly sensitive instrument is applied to detection of tritiated gases, wherein the compactness and low heat of this laser head permit placing the entire optical system, including laser head, charge coupled Raman detector, and ASER, within the glove box necessary for secondary containment of tritium, thereby accomplishing a robust, highly sensitive Raman analytical system for hazardous substances.

  9. Linear Polarized Transmission Resonance Raman Studies in Fruits: Experimental Versus Model Calculations.

    PubMed

    Martin, Daniel; Gonzálvez, Alicia G; Buesing, Franziska; González Ureña, Ángel

    2015-07-01

    A linear polarized transmission resonance Raman spectroscopic technique was developed to measure the depolarization ratio of different β-carotene Raman bands in carrot roots and mangos. Basically, this optical property was measured as a function of the vegetal tissue thickness and fruit postharvest lifetime. In general, the depolarization ratio increases as the sample optical thickness does and decreases as the fruit postharvest lifetime increases. In addition, a previous theoretical model was extended by considering the light state of polarization to obtain the depolarization ratio as a function of the sample absorption and scattering coefficient. It was shown how the reported theoretical model is able to satisfactorily describe the fruit optical parameter dependence on both the sample thickness and its postharvest time. Finally, the advantages and limitations of the present technique and theoretical mode are discussed. PMID:26037146

  10. A cavity type absorption cell for double resonance microwave spectroscopy.

    NASA Technical Reports Server (NTRS)

    Lee, M. C.; White, W. F.

    1972-01-01

    Description of an experimental dual resonant cavity absorption cell for observing microwave spectroscopic double-resonance effects. The device is composed of two Fabry-Perot interferometers excited by independent microwave sources and mounted at right angles in a suitable vacuum enclosure. The pumping transition is modulated by one source and the modulation induced on the rf absorption in the orthogonal cavity is detected.

  11. Resonance Raman Spectroscopy of Separated Single-Wall Carbon Nanotube

    NASA Astrophysics Data System (ADS)

    Simpson, J. R.; Fagan, J. A.; Tu, X.; Zheng, M.; Hight Walker, A. R.; Duque, J. G.; Crochet, J.; Doorn, S. K.

    2012-02-01

    The heterogeneity of single-wall carbon nanotubes (SWCNTs) produced by typical techniques complicates characterization and presents a barrier for technological applications. Improvements in separation and purification techniques enable detailed studies of specific nanotube properties by providing samples of unique chirality, length, metallicity, bundling, and interior filling. We report resonant Raman spectroscopy (RRS) measurements on these samples over a wide range of excitation wavelengths using a series of discrete and continuously tunable laser sources coupled to a triple-grating spectrometer. RRS of these homogeneous samples reveals unique spectral features and affords interpretation of intrinsic nanotube optical properties. Of particular interest are the G-band of chirally-pure armchair metallic SWCNTS and shifts of the radial breathing mode and excitation energy with water filling. Additionally, we will compare Raman results with other optical characterization techniques.

  12. Brain metastasis detection by resonant Raman optical biopsy method

    NASA Astrophysics Data System (ADS)

    Zhou, Yan; Liu, Cheng-hui; Cheng, Gangge; Zhou, Lixin; Zhang, Chunyuan; Pu, Yang; Li, Zhongwu; Liu, Yulong; Li, Qingbo; Wang, Wei; Alfano, Robert R.

    2014-03-01

    Resonant Raman (RR) spectroscopy provides an effective way to enhance Raman signal from particular bonds associated with key molecules due to changes on a molecular level. In this study, RR is used for detection of human brain metastases of five kinds of primary organs of lung, breast, kidney, rectal and orbital in ex-vivo. The RR spectra of brain metastases cancerous tissues were measured and compared with those of normal brain tissues and the corresponding primary cancer tissues. The differences of five types of brain metastases tissues in key bio-components of carotene, tryptophan, lactate, alanine and methyl/methylene group were investigated. The SVM-KNN classifier was used to categorize a set of RR spectra data of brain metastasis of lung cancerous tissues from normal brain tissue, yielding diagnostic sensitivity and specificity at 100% and 75%, respectively. The RR spectroscopy may provide new moleculebased optical probe tools for diagnosis and classification of brain metastatic of cancers.

  13. Electromagnetically induced absorption in a three-resonator metasurface system

    PubMed Central

    Zhang, Xueqian; Xu, Ningning; Qu, Kenan; Tian, Zhen; Singh, Ranjan; Han, Jiaguang; Agarwal, Girish S.; Zhang, Weili

    2015-01-01

    Mimicking the quantum phenomena in metamaterials through coupled classical resonators has attracted enormous interest. Metamaterial analogs of electromagnetically induced transparency (EIT) enable promising applications in telecommunications, light storage, slow light and sensing. Although the EIT effect has been studied extensively in coupled metamaterial systems, excitation of electromagnetically induced absorption (EIA) through near-field coupling in these systems has only been sparsely explored. Here we present the observation of the EIA analog due to constructive interference in a vertically coupled three-resonator metamaterial system that consists of two bright and one dark resonator. The absorption resonance is one of the collective modes of the tripartite unit cell. Theoretical analysis shows that the absorption arises from a magnetic resonance induced by the near-field coupling of the three resonators within the unit cell. A classical analog of EIA opens up opportunities for designing novel photonic devices for narrow-band filtering, absorptive switching, optical modulation, and absorber applications. PMID:26023061

  14. Resonant-Raman Intensities of N-layer Transition Metal Dichalcogenides from First Principles

    NASA Astrophysics Data System (ADS)

    Miranda, Henrique; Froehlicher, Guillaume; Lorchat, Ettienne; Fernique, François; Molina-Sánchez, Alejandro; Berciaud, Stéphane; Wirtz, Ludger

    Transition metal dichalcogenides (TMDs) have interesting optical and electronic properties that make them good candidates for nano-engineering applications. Raman spectroscopy provides information about the vibrational modes and optical spectrum at the same time: when the laser energy is close to an electronic transition, the intensity is increased due to resonance. We investigate these effects combining different ab initio methods: we obtain ground-state and vibrational properties from density functional theory and the optical absorption spectrum using GW corrections and the Bethe-Salpeter equation to account for the excitonic effects which are known to play an important role in TMDs. Using a quasi-static finite differences approach, we calculate the dielectric susceptibility for different light polarizations and different phonon modes in order to determine the Raman tensor of TMDs, in particular of multi-layer and bulk MoTe2. We explain recent experimental results for the splitting of high-frequency modes and deviations from the non-resonant Raman model. We also give a brief outlook on possible improvements of the methodology.

  15. Experimental evaluation of the twofold electromagnetic enhancement theory of surface-enhanced resonance Raman scattering

    SciTech Connect

    Yoshida, Ken-ichi; Itoh, Tamitake; Biju, Vasudevanpillai; Ishikawa, Mitsuru; Ozaki, Yukihiro

    2009-02-15

    We examined an electromagnetic (EM) theory of surface-enhanced resonance Raman scattering (SERRS) using single Ag nanoaggregates. The SERRS-EM theory is characterized by twofold EM enhancement induced by the coupling of plasmon resonance with both excitation and emission of Raman scattering plus fluorescence. The total emission cross-section spectra of enhanced Raman scattering and enhanced fluorescence were calculated using the following parameters: the spectrum of enhancement factor induced by plasmon resonance, resonance Raman scattering overlapped with fluorescence, and excitation wavelengths. The calculations well agreed with experimental total emission cross-section spectra, thus providing strong indications that the SERRS-EM theory is quantitatively correct.

  16. Resonance Raman spectroscopic studies of enzymesubstrate intermediates at 5 K

    NASA Astrophysics Data System (ADS)

    Kim, Munsok; Carey, Paul R.

    1991-01-01

    A simple and versatile system for resonance Raman (RR) spectroscopic analysis of enzymesubstrate complexes at liquid helium temperatures is described. The system allows us to record high-quality RR spectra for dithioacyl papain intermediates (MeO-Phe-Gly- and MeO-Gly-Gly-Phe-Gly-C (dbnd S)S-papain) in ice matrices at 5 K. Based on established structure-spectra correlations, it is concluded that the active-site conformation of the intermediates about the φ', ψ' glycinic linkages and cysteine-25 side chain is B-G+-PH both in ice matrices at 5 K and in solution at room temperature.

  17. Cold atom Raman spectrography using velocity-selective resonances.

    PubMed

    Fatemi, Fredrik K; Terraciano, Matthew L; Bashkansky, Mark; Dutton, Zachary

    2009-07-20

    We have studied velocity-selective resonances in the presence of a uniform magnetic field and shown how they can be used for rapid, single-shot assessment of the ground state magnetic sublevel spectrum in a cold atomic vapor. Cold atoms are released from a magneto-optical trap in the presence of a small bias magnetic field ( approximately 300 mG) and exposed to a laser field comprised of two phase-locked counterpropagating beams connecting the two ground state hyperfine manifolds. An image of the expanded cloud shows the velocity-selected resonances as distinct features, each corresponding to specific magnetic sublevel, in a direct, intuitive manner. We demonstrate the technique with both 87Rb and 85Rb, and show the utility of the technique by optically pumping into particular magnetic sublevels. The results are shown to agree with a theoretical model, and are compared to traditional Raman spectroscopy.

  18. Surface-enhanced resonance Raman spectroscopy of iron-dopamine complexes

    NASA Astrophysics Data System (ADS)

    Kowalchyk, Will K.; Davis, Kevin L.; Morris, Michael D.

    1995-01-01

    Surface-enhanced resonance Raman spectroscopy (SERRS) at silver colloids is used to detect the catecholamines, 3-hydroxytyramine (dopamine) and 3,4-dihydroxyphenylacetic acid (DOPAC), in a modified Ringer's solution. Catecholamines form very strong complexes with iron(III) in solution ( Kf > 10 40) and exhibit a broad ligand-to-metal charge-transfer (LMCT) absorption in the visible (˜ 500 nm). Resonance enhancement is achieved by excitation at 532 nm from a frequency doubled Nd:YAG laser with high quality spectra attainable in 1 s. Maximum SERRS signal is observed when basic buffer is added to a dopamine sample containing 50 × 10 -6 M ferric ion. Dopamine concentrations in the nanomolar (resting level) range are obtained using this technique.

  19. Remote sensing of the atmosphere by resonance Raman LIDAR

    SciTech Connect

    Sedlacek, A.J.; Harder, D.; Leung, K.P.; Zuhoski, P.B. Jr.; Burr, D.; Chen, C.L.

    1995-01-01

    With the increased environmental awareness has come the need for technologies that can detect, identify and monitor pollutants and, where necessary, verify their destruction. This need is evidenced by the recent creation of the Clean Air Act Amendments (CAAA), of which the Title 3-Hazardous Air Pollutants (HAP) amendments mandate the complete revision and expansion of the earlier Clean Air Act (CAA), section 112. As was pointed out by Grant, Kagann and McClenny, optical remote sensing technologies are expected to play a very important role in insuring that various facilities are in compliance with the Maximum Achievable Control Technology (MACT) standards for the reduction of HAP emissions that are called for in section 301 of Title 3. Unfortunately, however, many of these technologies have varying detection and applicability characteristics which often dictate the conditions under which one can use the sensor to detect, identify or monitor a chemical species. Some of the advantages that a Raman-based pollution sensor possess are: (1) very high selectivity (chemical specific fingerprints), (2) independence from the excitation wavelength (ability to monitor in the solar blind region), (3) chemical mixture fingerprints are the sum of its individual components (no spectral cross-talk), (4) near independence of the Raman fingerprint to its physical state (very similar spectra for gas, liquid, solid and solutions), and (5) insensitivity of the Raman signature to environmental conditions (no quenching, or interference from water). Early investigations were not able to take advantage of near-resonance enhancement of the Raman cross-section which occurs when the excitation frequency approaches an electronically excited state of the molecule. The enhancement of the scattering cross-section can be quite large, often approaching 4 to 6 orders of magnitude.

  20. UV resonance Raman study of model complexes of the Cu B site of cytochrome c oxidase

    NASA Astrophysics Data System (ADS)

    Nagano, Yasutomo; Liu, Jin-Gang; Naruta, Yoshinori; Kitagawa, Teizo

    2005-02-01

    A newly designed model complex for the CuB site of cytochrome c oxidase (CcO), that is, Cu coordinated by two free imidazoles and an imidazole covalently linked to p-cresol [CuIIBIAIPBr]Br, (BIAIP =2-[4-[[Bis(1-methyl-1H-imidazol-2-ylmethyl)amino]methyl]-1H-imidazol-1-yl]-4-methylphenol), and related molecules have been investigated with absorption and ultraviolet resonance Raman (UVRR) spectroscopy employing the excitation wavelengths between 220 and 290 nm. Attention was focused on the electron delocalization through the cross-linkage between the phenol and imidazole rings, and the influences by the coordination of CuII to imidazole. In addition to the ν8a and ν8b modes of p-cresol, a number of Raman bands involving vibrations of the imidazole moiety have been intensity-enhanced despite Raman excitation in resonance with the π-π* transition of phenol, indicating appreciable mixing of the π systems of imidazole and phenol rings. Furthermore, two kinds of imidazoles seem to be differential; one is the imidazole linked to p-cresol which yielded Raman bands at 1249, 1191, and 1141 cm-1 for protonated CuII-BIAIP, and the other is one not linked to p-cresol, which yielded an intense band at 1488 cm-1 band. Raman enhancement of the latter mode seems to be caused by preresonance to the lowest π-π* transition of imidazole via the A-term mechanism. The Raman excitation profile (REP) of ν8a mode for the deprotonated phenol of the CuII-complex revealed a weak local maximum corresponding to the La band around 240 nm. Raman enhancement by the La band was relatively weaker for the CuII-complex than for the ZnII-complex and metal-free ligand, suggesting the more extensive mixing of π systems of p-cresol-imidazole through the cross-linkage for the Cu II-complex.

  1. Human brain cancer studied by resonance Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhou, Yan; Liu, Cheng-Hui; Sun, Yi; Pu, Yang; Boydston-White, Susie; Liu, Yulong; Alfano, Robert R.

    2012-11-01

    The resonance Raman (RR) spectra of six types of human brain tissues are examined using a confocal micro-Raman system with 532-nm excitation in vitro. Forty-three RR spectra from seven subjects are investigated. The spectral peaks from malignant meningioma, stage III (cancer), benign meningioma (benign), normal meningeal tissues (normal), glioblastoma multiforme grade IV (cancer), acoustic neuroma (benign), and pituitary adenoma (benign) are analyzed. Using a 532-nm excitation, the resonance-enhanced peak at 1548 cm-1 (amide II) is observed in all of the tissue specimens, but is not observed in the spectra collected using the nonresonance Raman system. An increase in the intensity ratio of 1587 to 1605 cm-1 is observed in the RR spectra collected from meningeal cancer tissue as compared with the spectra collected from the benign and normal meningeal tissue. The peak around 1732 cm-1 attributed to fatty acids (lipids) are diminished in the spectra collected from the meningeal cancer tumors as compared with the spectra from normal and benign tissues. The characteristic band of spectral peaks observed between 2800 and 3100 cm-1 are attributed to the vibrations of methyl (-CH3) and methylene (-CH2-) groups. The ratio of the intensities of the spectral peaks of 2935 to 2880 cm-1 from the meningeal cancer tissues is found to be lower in comparison with that of the spectral peaks from normal, and benign tissues, which may be used as a distinct marker for distinguishing cancerous tissues from normal meningeal tissues. The statistical methods of principal component analysis and the support vector machine are used to analyze the RR spectral data collected from meningeal tissues, yielding a diagnostic sensitivity of 90.9% and specificity of 100% when two principal components are used.

  2. Raman-assisted Rabi resonances in two-mode cavity QED

    SciTech Connect

    Gruenwald, P.; Singh, S. K.; Vogel, W.

    2011-06-15

    The dynamics of a vibronic system in a lossy two-mode cavity is studied, with the first mode being resonant to the electronic transition and the second one being nearly resonant due to Raman transitions. We derive analytical solutions for the dynamics of this system. For a properly chosen detuning of the second mode from the exact Raman resonance, we obtain conditions that are closely related to the phenomenon of Rabi resonance as it is well known in laser physics. Such resonances can be observed in the spontaneous emission spectra, where the spectrum of the second mode in the case of weak Raman coupling is enhanced substantially.

  3. [Effect on Fermi Resonance by Some External Fields: Investigation of Fermi Resonance According to Raman Spectra].

    PubMed

    Jiang, Xiu-lan; Sun, Cheng-lin; Zhou, Mi; Li, Dong-fei; Men, Zhi-wei; Li, Zuo-wei; Gao, Shu-qin

    2015-03-01

    Fermi resonance is a phenomenon of molecular vibrational coupling and energy transfer occurred between different groups of a single molecule or neighboring molecules. Many properties of Fermi resonance under different external fields, the investigation method of Raman spectroscopy as well as the application of Fermi resonance, etc need to be developed and extended further. In this article the research results and development about Fermi resonance obtained by Raman spectral technique were introduced systematically according to our work and the results by other researchers. Especially, the results of the behaviors of intramolecular and intermolecular Fermi resonance of some molecules under some external fields such as molecular field, pressure field and temperature field, etc were investigated and demonstrated in detail according to the Raman spectra obtained by high pressure DAC technique, temperature variation technique as well as the methods we planed originally in our group such as solution concentration variation method and LCOF resonance Raman spectroscopic technique, and some novel properties of Fermi resonance were found firstly. Concretely, (1) Under molecular field. a. The Raman spectra of C5H5 N in CH3 OH and H2O indicates that solvent effect can influence Fermi resonance distinctly; b. The phenomena of the asymmetric movement of the Fermi resonance doublets as well as the fundamental involved is tuned by the Fermi resonance which had not been found by other methods were found firstly by our variation solution concentration method; c. The Fermi resonance properties can be influenced distinctly by the molecular group reorganization induced by the hydrogen bond and anti-hydrogen bond in solution; d. Fermi resonance can occurred between C7 H8 and m-C8H10, and the Fermi resonance properties behave quite differently with the solution concentration; (2) Under pressure field. a. The spectral lines shift towards high wavenumber with increasing pressure, and

  4. A deformable nanoplasmonic membrane reveals universal correlations between plasmon resonance and surface enhanced Raman scattering.

    PubMed

    Kang, Minhee; Kim, Jae-Jun; Oh, Young-Jae; Park, Sang-Gil; Jeong, Ki-Hun

    2014-07-01

    A quantitative correlation between plasmon resonance and surface enhanced Raman scattering (SERS) signals is revealed by using a novel active plasmonic method, that is, a deformable nanoplasmonic membrane. A single SERS peak has the maximum gain at the corresponding plasmon resonance wavelength, which has the maximum extinction product of an excitation and the corresponding Raman scattering wavelengths.

  5. Polarization control of intermediate state absorption in resonance-mediated multi-photon absorption process

    NASA Astrophysics Data System (ADS)

    Xu, Shuwu; Huang, Yunxia; Yao, Yunhua; Jia, Tianqing; Ding, Jingxin; Zhang, Shian; Sun, Zhenrong

    2015-07-01

    We theoretically and experimentally demonstrate the control of the intermediate state absorption in an (n + m) resonance-mediated multi-photon absorption process by the polarization-modulated femtosecond laser pulse. An analytical solution of the intermediate state absorption in a resonance-mediated multi-photon absorption process is obtained based on the time-dependent perturbation theory. Our theoretical results show that the control efficiency of the intermediate state absorption by the polarization modulation is independent of the laser intensity when the transition from the intermediate state to the final state is coupled by the single-photon absorption, but will be affected by the laser intensity when this transition is coupled by the non-resonant multi-photon absorption. These theoretical results are experimentally confirmed via a two-photon fluorescence control in (2 + 1) resonance-mediated three-photon absorption of Coumarin 480 dye and a single-photon fluorescence control in (1 + 2) resonance-mediated three-photon absorption of IR 125 dye.

  6. The confinement induced resonance in spin-orbit coupled cold atoms with Raman coupling

    PubMed Central

    Zhang, Yi-Cai; Song, Shu-Wei; Liu, Wu-Ming

    2014-01-01

    The confinement induced resonance provides an indispensable tool for the realization of the low-dimensional strongly interacting quantum system. Here, we investigate the confinement induced resonance in spin-orbit coupled cold atoms with Raman coupling. We find that the quasi-bound levels induced by the spin-orbit coupling and Raman coupling result in the Feshbach-type resonances. For sufficiently large Raman coupling, the bound states in one dimension exist only for sufficiently strong attractive interaction. Furthermore, the bound states in quasi-one dimension exist only for sufficient large ratio of the length scale of confinement to three dimensional s-wave scattering length. The Raman coupling substantially changes the confinement-induced resonance position. We give a proposal to realize confinement induced resonance through increasing Raman coupling strength in experiments. PMID:24862314

  7. Resonant photo-thermal modification of vertical gallium arsenide nanowires studied using Raman spectroscopy.

    PubMed

    Walia, Jaspreet; Boulanger, Jonathan; Dhindsa, Navneet; LaPierre, Ray; Tang, Xiaowu Shirley; Saini, Simarjeet S

    2016-06-17

    Gallium arsenide nanowires have shown considerable promise for use in applications in which the absorption of light is required. When the nanowires are oriented vertically, a considerable amount of light can be absorbed, leading to significant heating effects. Thus, it is important to understand the threshold power densities that vertical GaAs nanowires can support, and how the nanowire morphology is altered under these conditions. Here, resonant photo-thermal modification of vertical GaAs nanowires was studied using both Raman spectroscopy and electron microscopy techniques. Resonant waveguiding, and subsequent absorption of the excited optical mode reduces the irradiance vertical GaAs nanowires can support relative to horizontal ones, by three orders of magnitude before the onset of structural changes occur. A power density of only 20 W mm(-2) was sufficient to induce local heating in the nanowires, resulting in the formation of arsenic species. Upon further increasing the power, a hollow nanowire morphology was realized. These findings are pertinent to all optical applications and spectroscopic measurements involving vertically oriented GaAs nanowires. Understanding the optical absorption limitations, and the effects of exceeding these limitations will help improve the development of all III-V nanowire devices. PMID:27172276

  8. Resonant photo-thermal modification of vertical gallium arsenide nanowires studied using Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Walia, Jaspreet; Boulanger, Jonathan; Dhindsa, Navneet; LaPierre, Ray; (Shirley Tang, Xiaowu; Saini, Simarjeet S.

    2016-06-01

    Gallium arsenide nanowires have shown considerable promise for use in applications in which the absorption of light is required. When the nanowires are oriented vertically, a considerable amount of light can be absorbed, leading to significant heating effects. Thus, it is important to understand the threshold power densities that vertical GaAs nanowires can support, and how the nanowire morphology is altered under these conditions. Here, resonant photo-thermal modification of vertical GaAs nanowires was studied using both Raman spectroscopy and electron microscopy techniques. Resonant waveguiding, and subsequent absorption of the excited optical mode reduces the irradiance vertical GaAs nanowires can support relative to horizontal ones, by three orders of magnitude before the onset of structural changes occur. A power density of only 20 W mm-2 was sufficient to induce local heating in the nanowires, resulting in the formation of arsenic species. Upon further increasing the power, a hollow nanowire morphology was realized. These findings are pertinent to all optical applications and spectroscopic measurements involving vertically oriented GaAs nanowires. Understanding the optical absorption limitations, and the effects of exceeding these limitations will help improve the development of all III-V nanowire devices.

  9. Resonant photo-thermal modification of vertical gallium arsenide nanowires studied using Raman spectroscopy.

    PubMed

    Walia, Jaspreet; Boulanger, Jonathan; Dhindsa, Navneet; LaPierre, Ray; Tang, Xiaowu Shirley; Saini, Simarjeet S

    2016-06-17

    Gallium arsenide nanowires have shown considerable promise for use in applications in which the absorption of light is required. When the nanowires are oriented vertically, a considerable amount of light can be absorbed, leading to significant heating effects. Thus, it is important to understand the threshold power densities that vertical GaAs nanowires can support, and how the nanowire morphology is altered under these conditions. Here, resonant photo-thermal modification of vertical GaAs nanowires was studied using both Raman spectroscopy and electron microscopy techniques. Resonant waveguiding, and subsequent absorption of the excited optical mode reduces the irradiance vertical GaAs nanowires can support relative to horizontal ones, by three orders of magnitude before the onset of structural changes occur. A power density of only 20 W mm(-2) was sufficient to induce local heating in the nanowires, resulting in the formation of arsenic species. Upon further increasing the power, a hollow nanowire morphology was realized. These findings are pertinent to all optical applications and spectroscopic measurements involving vertically oriented GaAs nanowires. Understanding the optical absorption limitations, and the effects of exceeding these limitations will help improve the development of all III-V nanowire devices.

  10. Origin invariance in vibrational resonance Raman optical activity

    SciTech Connect

    Vidal, Luciano N. Cappelli, Chiara; Egidi, Franco; Barone, Vincenzo

    2015-05-07

    A theoretical investigation on the origin dependence of the vibronic polarizabilities, isotropic and anisotropic rotational invariants, and scattering cross sections in Resonance Raman Optical Activity (RROA) spectroscopy is presented. Expressions showing the origin dependence of these polarizabilities were written in the resonance regime using the Franck-Condon (FC) and Herzberg-Teller (HT) approximations for the electronic transition moments. Differently from the far-from-resonance scattering regime, where the origin dependent terms cancel out when the rotational invariants are calculated, RROA spectrum can exhibit some origin dependence even for eigenfunctions of the electronic Hamiltonian. At the FC level, the RROA spectrum is completely origin invariant if the polarizabilities are calculated using a single excited state or for a set of degenerate states. Otherwise, some origin effects can be observed in the spectrum. At the HT level, RROA spectrum is origin dependent even when the polarizabilities are evaluated from a single excited state but the origin effect is expected to be small in this case. Numerical calculations performed for (S)-methyloxirane, (2R,3R)-dimethyloxirane, and (R)-4-F-2-azetidinone at both FC and HT levels using the velocity representation of the electric dipole and quadrupole transition moments confirm the predictions of the theory and show the extent of origin effects and the effectiveness of suggested ways to remove them.

  11. Resonant absorption of p-modes by sunspots

    NASA Technical Reports Server (NTRS)

    Chitre, S. M.; Davila, Joseph M.

    1990-01-01

    Explanations for the observed p-mode absorption in sunspots are examined. It is demonstrated that any dissipative process like radiative, viscous, or resistive dissipation leads to the resonant absorption of acoustic waves incident on the sunspot tube, and that the resultant heating rate can be shown to be consistent with the observed absorption of the p-mode power impinging on an isolated inhomogeneously structured sunspot.

  12. Phase-sensitive detection of optical resonances by using an acousto-optic modulator in the Raman - Nath diffraction mode

    SciTech Connect

    Baryshev, V N; Domnin, Yu S; Kopylov, L N

    2007-11-30

    A new method for frequency control of an external cavity diode laser without direct modulation of the injection current is proposed. The Pound - Drever optical heterodyne technique or the method of frequency control by frequency-modulated sidebands, in which an acousto-optic modulator operating in the Raman - Nath diffraction mode is used as an external phase modulator, can be employed to obtain error signals upon automatic frequency locking of the diode laser to the saturated absorption resonances within the D{sub 2} line of cesium atoms or to the optical cavity resonances. (control of laser radiation parameters)

  13. Resonance Raman spectroscopy of octopus rhodopsin and its photoproducts

    SciTech Connect

    Pande, C.; Pande, A.; Yue, K.T.; Callender, R.; Ebrey, T.G.; Tsuda, M.

    1987-08-11

    The authors report here the resonance Raman spectra of octopus rhodopsin and its photoproducts, bathorhodopsin and acid metarhodopsin. These studies were undertaken in order to make comparisons with the well-studied bovine pigments, so as to understand the similarities and the differences in pigment structure and photochemical processes between vertebrates and invertebrates. The flow method was used to obtain the Raman spectrum of rhodopsin at 13 /sup 0/C. The bathorhodopsin spectrum was obtained by computer subtraction of the spectra containing different photostationary mixtures of rhodopsin, isorhodopsin, hypsorhodopsin, and bathorhodopsin, obtained at 12 K using the pump-probe technique and from measurements at 80 K. Like their bovine counterparts, the Schiff base vibrational mode appears at approx. 1660 cm/sup -1/ in octopus rhodopsin and the photoproducts, bathorhodopsin and acid metarhodopsin, suggesting a proteonated Schiff base linkage between the chromophore and the protein. Differences between the Raman spectra of octopus rhodopsin and bathorhodopsin indicate that the formation of bathorhodopsin is associated with chromophore isomerization. This inference is substantiated by the chromophore chemical extraction data which show that, like the bovine system, octopus rhodopsin is an 11-cis pigment, while the photoproducts contain an all-trans pigment, in agreement with the previous work. The octopus rhodopsin and bathorhodopsin spectra show marked differences from their bovine counterparts in other respects, however. The differences are most dramatic in the structure-sensitive fingerprint and the HOOP regions. Thus, it appears that although the two species differ in the specific nature of the chromophore-protein interactions, the general process of visual transduction is the same.

  14. Broadband absorption through extended resonance modes in random metamaterials

    NASA Astrophysics Data System (ADS)

    Hao, J.; Niemiec, R.; Burgnies, L.; Lheurette, É.; Lippens, D.

    2016-05-01

    The properties of disordered metamaterial absorbers are analyzed on the basis of numerical simulations and experimental characterizations. A broadening of the absorption spectrum is clearly evidenced. This effect is the consequence of both the coupling between nearby resonators leading to the occurrence of extended magnetic resonance modes and the interconnection of elementary particles yielding the definition of resonating clusters. The angular robustness of the absorbing structure under oblique incidence is also demonstrated for a wide domain of angles.

  15. Christiansen effect in disperse systems with resonant absorption

    SciTech Connect

    Zimnyakov, D A; Isaeva, Elmira A; Isaeva, A A

    2012-01-31

    We discuss the results of experimental studies of competition of absorption and scattering of laser radiation propagating in dispersive media with resonant absorption. As media under study, use is made of a suspension of polystyrene particles in solutions of rhodamine 6G in ethylene glycol probed by laser light with a wavelength of 532 nm. It is found that an increase in the dye concentration leads to an increase in optical transmittance of suspensions and an increase in speckle modulation of the forward-scattered radiation. We interpret these features as a manifestation of Christiansen effect in disperse systems with resonance absorption.

  16. Resonance Raman mapping as a tool to monitor and manipulate Si nanocrystals in Si-SiO{sub 2} nanocomposite

    SciTech Connect

    Rani, Ekta; Ingale, Alka A.; Chaturvedi, A.; Joshi, M. P.; Kukreja, L. M.

    2015-10-19

    Specially designed laser heating experiment along with Raman mapping on Si-SiO{sub 2} nanocomposites elucidates the contribution of core and surface/interface in the intermediate frequency range (511–514 cm{sup −1}) Si phonons. The contribution of core to surface/interface increases with the size of Si nanocrystal, which itself increases on laser irradiation. Further, it is found that resonance Raman is crucial to the observance of surface/interface phonons and wavelength dependent Raman mapping can be corroborated with band edges observed in absorption spectra. This understanding can be gainfully used to manipulate and characterize Si-SiO{sub 2} nanocomposite, simultaneously for photovoltaic device applications.

  17. Resonant X-Ray Scattering and Absorption

    NASA Astrophysics Data System (ADS)

    Collins, S. P.; Bombardi, A.

    This chapter outlines some of the basic ideas behind nonresonant and resonant X-ray scattering, using classical or semiclassical pictures wherever possible; specifically, we highlight symmetry arguments governing the observation of X-ray optical effects, such as X-ray magnetic circular dichroism and resonant "forbidden" diffraction. Without dwelling on the microscopic physics that underlies resonant scattering, we outline some key steps required for calculating its rotation and polarization dependence, based on Cartesian and spherical tensor frameworks. Several examples of resonant scattering, involving electronic anisotropy and magnetism, are given as illustrations. Our goal is not to develop or defend theoretical concepts in X-ray scattering, but to bring together existing ideas in a pragmatic and utilitarian manner.

  18. Stand-off detection of explosives vapors by resonance-enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Johansson, Ida; Ceco, Ema; Ehlerding, Anneli; Östmark, Henric

    2013-06-01

    This paper describes a system for stand-off vapor detection based on Resonant Raman spectroscopy, RRS. The system is a step towards a RRS LIDAR (Light Detection And Ranging) system, capable of detecting vapors from explosives and explosives precursors at long distances. The current system was used to detect the vapor of nitromethane and mononitrotoluene outdoors in the open air, at a stand-off distance of 11-13 meters. Also, the signal dependence upon irradiation wavelength and sample concentration was studied in controlled laboratory conditions. A tunable Optical Parametric Oscillator pumped by an Nd:YAG laser, with a pulse length of 6 ns, was operated in the UV range of interest, 210-400 nm, illuminating the sample vapor. The backscattered Raman signal was collected by a telescope and a roundto- slit optical fiber was used to transmit collected light to the spectrometer with minimum losses. A gated intensified charge-coupled device (ICCD) registered the spectra. The nitromethane cross section was resonance enhanced more than a factor 30 700, when measured at 220 nm, compared to the 532 nm value. The results show that a decrease in concentration can have a positive effect on the sensitivity of the system, due to a decrease in absorption and selfabsorption in the sample.

  19. New Feature Observed in the Raman Resonance Excitation Profiles of (6 , 5) -Enriched, Selectively Bundled SWCNTs

    NASA Astrophysics Data System (ADS)

    Hight Walker, A. R.; Simpson, J. R.; Roslyak, O.; Haroz, E.; Telg, H.; Duque, J. G.; Crochet, J. J.; Piryatinski, A.; Doorn, S. K.

    Understanding the photophysics of exciton behavior in single wall carbon nanotube (SWCNT) bundles remains important for opto-electronic device applications. We report resonance Raman spectroscopy (RRS) measurements on (6 , 5) -enriched SWCNTs, dispersed in aqueous solutions and separated using density gradient ultracentrifugation into fractions of increasing bundling. Near-IR to UV absorption spectroscopy shows a redshift and broadening of the main excitonic transitions with increasing bundling. A continuously tunable dye laser coupled to a triple-grating spectrometer affords measurement of Raman resonance excitation profiles (REPs) over a range of wavelengths covering the (6 , 5) -E22 range (505 to 585) nm. REPs of both the radial breathing mode (RBM) and G-band reveal a redshifting and broadening of the (6 , 5) E22 transition energy with increasing bundling. Additionally, we observe an unexpected peak in the REP of bundled SWCNTs, which is shifted lower in energy than the main E22 and is anomalously narrow. We compare these observations to a theoretical model that examines the origin of this peak in relation to bundle polarization-enhanced exciton response.

  20. Coherent anti-Stokes Raman scattering (CARS) spectra, with resonance enhancement, of cytochrome c and vitamin B12 in dilute aqueous solution.

    PubMed

    Nestor, J; Spiro, T G; Klauminzer, G

    1976-10-01

    Coherent anti-Stokes Raman scattering (CARS) spectra have been obtained for ferrocytochrome c and cyano cobalamin in aqueous solution at millimolar concentrations, using a pair of tunable dye lasers pumped by a pulsed nitrogen laser. Resonance enhancement was obtained by tuning the omega1 laser to the visible absorption bands of the samples. The spectral features correspond to those observed in the conventional resonance Raman spectra. It appears that CARS spectroscopy, with its advantageous fluorescence rejection, can be usefully applied to biological samples by exploiting resonance enhancement. While the background scattering from water is 10 times higher than that of benzene and other aromatic solvents, it is actually at the low end of the scale for most liquids. The anomalously low background of aromatic liquids is thought to result from competition by the unusually efficient stimulated Raman scattering which they display. Off-resonance spectra for both cobalamin and cytochrome c contain negative peaks, i.e., absorption bands in the background. These are interpreted as inverse Raman processes induced by the omega1 photons in the presence of the continuum provided by the background scattering. While both CARS and the inverse Raman effect are subject to resonance enhancement, the wavelength dependence of CARS is evidently steeper.

  1. Raman, photoluminescence and absorption studies on high quality AlN single crystals

    NASA Astrophysics Data System (ADS)

    Senawiratne, J.; Strassburg, M.; Dietz, N.; Haboeck, U.; Hoffmann, A.; Noveski, V.; Dalmau, R.; Schlesser, R.; Sitar, Z.

    2005-05-01

    High quality AlN single crystals grown by physical vapour transport and by sublimation of AlN powder were investigated by Raman, photoluminescence (PL) and absorption spectroscopy. Absorption edges of the AlN single crystals varying from 4.1 eV to 5.9 eV as determined by transmission measurements. Near band edge absorption, PL and glow discharge mass spectroscopy identified impurities such as oxygen, silicon, carbon, and boron that contribute to the absorption and emission bands below the bandgap. The absorption coefficients were derived from UV (6 eV) to FIR (60 meV) spectral range. The exact crystal orientation of the samples, and their low carrier density were confirmed by Raman spectroscopy.

  2. Resonance Raman characterization of different forms of ground-state 8-bromo-7-hydroxyquinoline caged acetate in aqueous solutions.

    PubMed

    An, Hui-Ying; Ma, Chensheng; Nganga, Jameil L; Zhu, Yue; Dore, Timothy M; Phillips, David Lee

    2009-03-26

    The 8-bromo-7-hydroxyquinolinyl group (BHQ) is a derivative of 7-hydroxyquinoline (7-HQ) and BHQ molecules coexisting as different forms in aqueous solution. Absorption and resonance Raman spectroscopic methods were used to examine 8-bromo-7-hydroxyquinoline protected acetate (BHQ-OAc) in acetonitrile (MeCN), H(2)O/MeCN (60:40, v/v, pH 6 approximately 7), and NaOH-H(2)O/MeCN (60:40, v/v, pH 11 approximately 12) to obtain a better characterization of the forms of the ground-state species of BHQ-OAc in aqueous solutions and to examine their properties. The absorption spectra of BHQ-OAc in water show no absorption bands of the tautomeric species unlike the strong band at about 400 nm observed for the tautomeric form in 7-HQ aqueous solution. The resonance Raman spectra in conjunction with Raman spectra predicted from density functional theory (DFT) calculations reveal the observation of a double Raman band system characteristic of the neutral form (the nominal C=C ring stretching, C-N stretching, and O-H bending modes at 1564 and 1607 cm(-1)) and a single Raman band diagnostic of the enol-deprotonated anionic form (the nominal C=C ring, C-N, and C-O(-) stretching modes in the 1593 cm(-1) region). These results suggest that the neutral form of BHQ-OAc is the major species in neutral aqueous solution. There is a modest increase in the amount of the anionic form and a big decrease in the amount of the tautomeric form of the molecules for BHQ-OAc compared to 7-HQ in neutral aqueous solution. The presence of the 8-bromo group and/or competitive hydrogen bonding that hinder the formation and transfer process of a BHQ-OAc-water cyclic complex may be responsible for this large substituent effect. PMID:19296708

  3. Exploring the potential of Raman and resonance Raman spectroscopy for quantitative analysis of duplex DNA

    NASA Astrophysics Data System (ADS)

    Schulze, H. G.; Bass, A.; Addison, C.; Hughesman, C.; So, A. P.; Haynes, C. A.; Blades, M. W.; Turner, R. F. B.

    2005-09-01

    Advances in DNA microarray fabrication technologies, expanding probe libraries, and new bioinformatics methods and resources have firmly established array-based techniques as mainstream bioanalytical tools and the application space is proliferating rapidly. However, the capability of these tools to yield truly quantitative information remains limited, primarily due to problems inherent to the use of fluorescence imaging for reading the hybridized arrays. The obvious advantages of fluorescence are the unrivaled sensitivity and simplicity of the instrumentation. There are disadvantages of this approach, however, such as difficulties in achieving optimal labeling of targets and reproducible signals (due to quenching, resonance energy transfer, photobleaching effects, etc.) that undermine precision. We are exploring alternative approaches, based mainly on Raman and resonance Raman spectroscopy, that in principle permit direct analysis of structural differences between hybridized and unhybridized probes, thereby eliminating the need for labeling the target analytes. We report here on the status of efforts to evaluate the potential of these methods based on a combination of measured data and simulated experiments involving short (12-mer) ssDNA oligomer probes with varying degrees of hybridized target DNA. Preliminary results suggest that it may be possible to determine the fraction of duplex probes within a single register on a DNA microarray from 100% down to 10% (or possibly less) with a precision of +/-2 5%. Details of the methods used, their implementation, and their potential advantages and limitations are presented, along with discussion of the utility of using 2DCOS methods to emphasize small spectral changes sensitive to interstrand H bonding, backbone flexibility, hypochromicity due to base-stacking in duplex structures and solvation effects.

  4. Plasmonic Resonant Absorption in Mid-Infrared in Graphene Nanoresonators

    NASA Astrophysics Data System (ADS)

    Abeysinghe, Don C.; Myers, Joshua; Esfahani, Nima N.; Walker, Dennis E., Jr.; Hendrickson, Joshua R.; Cleary, Justin; Mou, Shin; Air Force Research Laboratory, Materials; Manufacturing Directorate, Wright-Patterson AFB, OH, USA Team; Air Force Research Laboratory, Sensors Directorate, Wright-Patterson AFB, OH, USA Team

    2014-03-01

    We experimentally demonstrated polarization-sensitive, tunable plasmonic resonant absorption in the mid-infrared range of 5-14 um by utilizing an array of graphene nanoribbon resonators. By tuning resonator width and charge density, we probed graphene plasmons with λp <= λ /100 and plasmon resonance energy as high as 0.26 meV (2100 cm-1) for 40 nm wide nanoresonators. Resonant absorption spectra enabled us to map the wavevector-frequency dispersion for graphene plasmons at mid-IR energies and revealed a modified plasmon dispersion as well as plasmon damping due to intrinsic optical phonons of graphene and graphene plasmon interaction with the surface polar phonons in SiO2 substrates. Additionally, we studied spectra further by introducing intrinsic defect phonons and doping by direct electron beam irradiation of graphene nanoresonators

  5. Simulations of Two-dimensional Infrared and Stimulated Resonance Raman Spectra of Photoactive Yellow Protein

    PubMed Central

    Preketes, Nicholas K; Biggs, Jason D; Ren, Hao; Andricioaei, Ioan; Mukamel, Shaul

    2012-01-01

    We present simulations of one and two-dimensional infrared (2DIR) and stimulated resonance Raman (SRR) spectra of the dark state (pG) and early red-shifted intermediate (pR) of photoactive yellow protein (PYP). Shifts in the amide I and Glu46 COOH stretching bands distinguish between pG and pR in the IR absorption and 2DIR spectra. The one-dimensional SRR spectra are similar to the spontaneous RR spectra. The two-dimensional SRR spectra show large changes in cross peaks involving the C=O stretch of the two species and are more sensitive to the chromophore structure than 2DIR spectra. PMID:24244064

  6. High-sensitivity pesticide detection using particle-enhanced resonant Raman scattering

    NASA Astrophysics Data System (ADS)

    Ranjan, Bikas; Saito, Yuika; Verma, Prabhat

    2016-03-01

    The use of pesticides in agriculture has raised concerns, as even a small residual of pesticide on food can be harmful. It is therefore of great importance to develop a robust technique to detect tiny amounts of pesticides. Although Raman spectroscopy is frequently used for chemical identification, it is not suitable for extremely low molecular concentrations. We propose a technique called particle-enhanced resonant Raman spectroscopy to detect extremely low concentrations of pesticides, where gold nanoparticles of desired plasmonic resonance are synthesized to match the resonance in Raman scattering. We successfully demonstrated the detection of extremely low amounts of pesticides on oranges.

  7. Near-Field Enhanced UV Resonance Raman Spectroscopy Using Aluminum Bow-tie Nano-antenna

    SciTech Connect

    Li, Ling; Lim, Shuang Fang; Puretzky, Alexander A; Riehn, Robert; Hallen, Hans

    2012-01-01

    An aluminum bow-tie nano-antenna is combined with the resonance Raman eect in the deep ultraviolet to dramatically increase the sensitivity of Raman spectra to a small volume of material, such as benzene used here. We further demonstrate gradient-eld Raman peaks for several strong IR modes. We achieve a gain of 105 in signal intensity from the near eld enhancement due to the surface plasmon resonance in the aluminum nanostructure. The on-line resonance enhancement contributes another factor of several thousands, limited by the laser line width. Thus, an overall gain of hundreds of million is achieved.

  8. Enhancement of resonant absorption through excitation of SPR

    NASA Astrophysics Data System (ADS)

    Giulietti, Danilo; Calcagno, L.; Curcio, Alessandro; Cutroneo, M.; Galletti, Mario; Skala, J.; Torrisi, L.; Zimbone, M.

    2016-09-01

    In this experiment the absorption of the laser radiation impinging on polymeric films with Au nanoparticles implanted in surface was studied. By varying the polarization and the incidence angle of the laser radiation on target, the role in the laser absorption of both excitation of surface plasmons and excitation of electronic plasma waves at critical density through resonant absorption was highlighted. In conditions of p-polarized laser irradiations at 1015 W /cm2 intensity, resonant absorption can be induced in films enhancing proton and ion acceleration. Plasma on-line diagnostics is based on SiC detectors. Measurements of kinetic energy of accelerated ions indicate a significant increment using p-polarized laser light with respect to no-polarized light irradiation.

  9. Theory and method for calculating resonance Raman scattering from resonance polarizability derivatives

    NASA Astrophysics Data System (ADS)

    Jensen, L.; Zhao, L. L.; Autschbach, J.; Schatz, G. C.

    2005-11-01

    We present a method to calculate both normal Raman-scattering (NRS) and resonance Raman-scattering (RRS) spectra from the geometrical derivatives of the frequency-dependent polarizability. In the RRS case, the polarizability derivatives are calculated from resonance polarizabilities by including a finite lifetime of the electronic excited states using time-dependent density-functional theory. The method is a short-time approximation to the Kramers, Heisenberg, and Dirac formalism. It is similar to the simple excited-state gradient approximation method if only one electronic excited state is important, however, it is not restricted to only one electronic excited state. Since the method can be applied to both NRS and RRS, it can be used to obtain complete Raman excitation profiles. To test the method we present the results for the S2 state of uracil and the S4,S3, and S2 states of pyrene. As expected, the results are almost identical to the results obtained from the excited-state gradient approximation method. Comparing with the experimental results, we find in general quite good agreement which enables an assignment of the experimental bands to bands in the calculated spectrum. For uracil the inclusion of explicit waters in the calculations was found to be necessary to match the solution spectra. The calculated resonance enhancements are on the order of 104-106, which is in agreement with experimental findings. For pyrene the method is also able to distinguish between the three different electronic states for which experimental data are available. The neglect of anharmonicity and solvent effects in the calculations leads to some discrepancy between theory and experiment.

  10. Resonance Raman enhancement of phenyl ring vibrational modes in phenyl iron complex of myoglobin.

    PubMed

    Liu, H H; Lin, S H; Yu, N T

    1990-04-01

    Resonance Raman spectra are reported for the organometallic phenyl-FeIII complexes of horse heart myoglobin. We observed the resonance enhancement of the ring vibrational modes of the bound phenyl group. They were identified at 642, 996, 1,009, and 1,048 cm-1, which shift to 619, 961, 972, and 1,030 cm-1, respectively, upon phenyl 13C substitution. The lines at 642 and 996 cm-1 are assigned, respectively, as in-plane phenyl ring deformation mode (derived from benzene vibration No. 6a at 606 cm-1) and out-of-plane CH deformation (derived from benzene vibration No. 5 at 995 cm-1). The frequencies of the ring "breathing" modes at 1,009 and 1,048 cm-1 are higher than the corresponding ones in phenylalanine (at 1,004 and 1,033 cm-1) and benzene (at 992 and 1,010 cm-1), indicating that the ring C--C bonds are strengthened (or shortened) when coordinated to the heme iron. The excitation profiles of these phenyl ring modes and a porphyrin ring vibrational mode at 674 cm-1 exhibit peaks near its Soret absorption maximum at 431 nm. This appears to indicate that these phenyl ring modes may be enhanced via resonance with the Soret pi-pi transition. The FeIII--C bond stretching vibration has not been detected with excitation wavelengths in the 406.7-457.9-nm region.

  11. Russian roulette efficiency in Monte Carlo resonant absorption calculations

    PubMed

    Ghassoun; Jehouani

    2000-10-01

    The resonant absorption calculation in media containing heavy resonant nuclei is one of the most difficult problems treated in reactor physics. Deterministic techniques need many approximations to solve this kind of problem. On the other hand, the Monte Carlo method is a reliable mathematical tool for evaluating the neutron resonance escape probability. But it suffers from large statistical deviations of results and long computation times. In order to overcome this problem, we have used the Splitting and Russian Roulette technique coupled separately to the survival biasing and to the importance sampling for the energy parameter. These techniques have been used to calculate the neutron resonance absorption in infinite homogenous media containing hydrogen and uranium characterized by the dilution (ratio of the concentrations of hydrogen to uranium). The punctual neutron source energy is taken at Es = 2 MeV and Es = 676.45 eV, whereas the energy cut-off is fixed at Ec = 2.768 eV. The results show a large reduction of computation time and statistical deviation, without altering the mean resonance escape probability compared to the usual analog simulation. The Splitting and Russian Roulette coupled to the survival biasing method is found to be the best methods for studying the neutron resonant absorption, particularly for high energies. A comparison is done between the Monte Carlo and deterministic methods based on the numerical solution of the neutron slowing down equations by the iterative method results for several dilutions.

  12. Measurements of the mass absorption cross section of atmospheric soot particles using Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Nordmann, S.; Birmili, W.; Weinhold, K.; Müller, K.; Spindler, G.; Wiedensohler, A.

    2013-11-01

    Soot particles are a major absorber of shortwave radiation in the atmosphere. The mass absorption cross section is an essential quantity to describe this light absorption process. This work presents new experimental data on the mass absorption cross section of soot particles in the troposphere over Central Europe. Mass absorption cross sections were derived as the ratio between the light absorption coefficient determined by multiangle absorption photometry (MAAP) and the soot mass concentration determined by Raman spectroscopy. The Raman method is sensitive to graphitic structures present in the particle samples and was calibrated in the laboratory using Printex®90 model particles. Mass absorption cross sections were determined for a number of seven observation sites, ranging between 3.9 and 7.4 m2 g-1depending on measurement site and observational period. The highest values were found in a continentally aged air mass in winter, where soot particles were assumed to be mainly internally mixed. Our values are in the lower range of previously reported values, possibly due to instrumental differences to the former photometer and mass measurements. Overall, a value of 5.3m2 g-1from orthogonal regression over all samples is considered to be representative for the soot mass absorption cross section in the troposphere over Central Europe.

  13. Why are blue visual pigments blue? A resonance Raman microprobe study.

    PubMed Central

    Loppnow, G R; Barry, B A; Mathies, R A

    1989-01-01

    A resonance Raman microscope has been developed to study the structure of the retinal prosthetic group in the visual pigments of individual photoreceptor cells. Raman vibrational spectra are obtained by focusing the probe laser on intact photoreceptors frozen on a 77 K cold stage. To elucidate the mechanism of wavelength regulation in blue visual pigments, we have used this apparatus to study the structure of the chromophore in the 440-nm absorbing pigment found in "green rods" of the toad (Bufo marinus). The 9-cis isorhodopsin form of the green rod pigment exhibits a 1662-cm-1 C = NH+ Schiff base stretching mode that shifts to 1636 cm-1 in deuterium-substituted H2O. This demonstrates that the Schiff base linkage to the protein is protonated. Protonation of the Schiff base is sufficient to explain the 440-nm absorption maximum of this pigment without invoking any additional protein-chromophore interactions. The absence of additional perturbations is supported by the observation that the ethylenic band and the perturbation-sensitive C-10-C-11 and C-14-C-15 stretching modes have the same frequency as those of the 9-cis protonated retinal Schiff base in solution. Our demonstration that a blue visual pigment contains an unperturbed protonated Schiff base provides experimental evidence that the protein charge perturbation responsible for the opsin shift in the 500-nm absorbing pigments is removed in the opsins of blue pigments, as suggested by the sequence data. PMID:2493645

  14. Coherent Raman scattering with incoherent light for a multiply resonant mixture: Theory

    NASA Astrophysics Data System (ADS)

    Kirkwood, Jason C.; Ulness, Darin J.; Stimson, Michael J.; Albrecht, A. C.

    1998-02-01

    The theory for coherent Raman scattering (CRS) with broadband incoherent light is presented for a multiply resonant, multicomponent mixture of molecules that exhibits simultaneous multiple resonances with the frequencies of the driving fields. All possible pairwise hyperpolarizability contributions to the signal intensity are included in the theoretical treatment-(resonant-resonant, resonant-nonresonant, and nonresonant-nonresonant correlations between chromophores) and it is shown how the different types of correlations manifest themselves as differently behaved components of the signal intensity. The Raman resonances are modeled as Lorentzians in the frequency domain, as is the spectral density of the incoherent light. The analytic results for this multiply resonant mixture are presented and applied to a specific binary mixture. These analytic results will be used to recover frequencies and dephasing times in a series of experiments on multiply resonant mixtures.

  15. High-performance dispersive Raman and absorption spectroscopy as tools for drug identification

    NASA Astrophysics Data System (ADS)

    Pawluczyk, Olga; Andrey, Sam; Nogas, Paul; Roy, Andrew; Pawluczyk, Romuald

    2009-02-01

    Due to increasing availability of pharmaceuticals from many sources, a need is growing to quickly and efficiently analyze substances in terms of the consistency and accuracy of their chemical composition. Differences in chemical composition occur at very low concentrations, so that highly sensitive analytical methods become crucial. Recent progress in dispersive spectroscopy with the use of 2-dimensional detector arrays, permits for signal integration along a long (up to 12 mm long) entrance slit of a spectrometer, thereby increasing signal to noise ratio and improving the ability to detect small concentration changes. This is achieved with a non-scanning, non-destructive system. Two different methods using P&P Optica high performance spectrometers were used. High performance optical dispersion Raman and high performance optical absorption spectroscopy were employed to differentiate various acetaminophen-containing drugs, such as Tylenol and other generic brands, which differ in their ingredients. A 785 nm excitation wavelength was used in Raman measurements and strong Raman signals were observed in the spectral range 300-1800 cm-1. Measurements with the absorption spectrometer were performed in the wavelength range 620-1020 nm. Both Raman and absorption techniques used transmission light spectrometers with volume phase holographic gratings and provided sufficient spectral differences, often structural, allowing for drug differentiation.

  16. Ultrasensitive protein detection in terms of multiphonon resonance Raman scattering in ZnS nanocrystals

    NASA Astrophysics Data System (ADS)

    Chu, Xueying; Hong, Xia; Zou, Peng; Men, Jing; Liu, Yichun

    2011-06-01

    Ultrasensitive protein detection was realized using multiphonon Resonance Raman scattering in ZnS nanocrystals. The longitudinal optical phonon line of ZnS and its overtones, which are called multiphonon Raman lines (MRLs), were used as the Raman probe signals. MRLs have a narrow bandwidth, high stability in aqueous solution, and strong resistance to interference from surface variations. Our results show that these features allow for reliable biodetection with good selectivity and high specificity. The detection limit is about 5 fM. This Raman scattering-based methodology will greatly extend the potential applications for ZnS in the biomedical sciences.

  17. IR absorption and surface-enhanced Raman spectra of the isoquinoline alkaloid berberine

    NASA Astrophysics Data System (ADS)

    Strekal', N. D.; Motevich, I. G.; Nowicky, J. W.; Maskevich, S. A.

    2007-01-01

    We present the IR absorption and surface-enhanced Raman scattering (SERS) spectra of the isoquinoline alkaloid berberine adsorbed on a silver hydrosol and on the surface of a silver electrode for different potentials. Based on quantum chemical calculations, for the first time we have assigned the vibrations in the berberine molecule according to vibrational mode. The effect of the potential of the silver electrode on the geometry of sorption of the molecule on the surface is considered, assuming a short-range mechanism for enhancement of Raman scattering.

  18. High-Resolution Study of X-Ray Resonant Raman Scattering at the K Edge of Silicon

    SciTech Connect

    Szlachetko, J.; Dousse, J.-Cl.; Berset, M.; Fennane, K.; Szlachetko, M.; Hoszowska, J.; Barrett, R.; Pajek, M.; Kubala-Kukus, A.

    2006-08-18

    We report on the first high-resolution measurements of the K x-ray resonant Raman scattering (RRS) in Si. The measured x-ray RRS spectra, interpreted using the Kramers-Heisenberg approach, revealed spectral features corresponding to electronic excitations to the conduction and valence bands in silicon. The total cross sections for the x-ray RRS at the 1s absorption edge and the 1s-3p excitation were derived. The Kramers-Heisenberg formalism was found to reproduce quite well the x-ray RRS spectra, which is of prime importance for applications of the total-reflection x-ray fluorescence technique.

  19. Intensity Ratio of Resonant Raman Modes for (n , m) Enriched Semiconducting Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Piao, Yanmei; Simpson, Jeffrey; Streit, Jason; Ao, Geyou; Fagan, Jeffrey; Hight Walker, Angela

    Relative intensities of resonant Raman spectral features, specifically the radial breathing mode (RBM) and G modes, of eleven, chirality-enriched, single-wall carbon nanotube (SWCNT) species were established under second-order optical transition excitation. The results demonstrate a significantly under-recognized complexity in the evaluation of Raman spectra for the assignment of (n , m) population distributions. Strong chiral angle and mod dependencies affect the intensity ratio of the RBM to G modes and can result in misleading interpretations. Furthermore, we report five additional values for chirality dependent G+ and G- Raman peak positions and intensities, supporting accuracy in literature values, and extending the available data to cover more of the small diameter regime by including the first (5,4) second-order, resonance Raman spectra. Together, the Raman spectral library is demonstrated to be sufficient for decoupling multiple species via a spectral fitting process, and enable fundamental characterization even in mixed chiral population samples.

  20. Surface-enhanced Raman scattering (SERS) and surface-enhanced resonance Raman scattering (SERRS): a review of applications.

    PubMed

    McNay, Graeme; Eustace, David; Smith, W Ewen; Faulds, Karen; Graham, Duncan

    2011-08-01

    Surface-enhanced Raman scattering (SERS) and surface-enhanced resonance Raman scattering (SERRS) can provide positive identification of an analyte or an analyte mixture with high sensitivity and selectivity. Better understanding of the theory and advances in the understanding of the practice have led to the development of practical applications in which the unique advantages of SERS/SERRS have been used to provide effective solutions to difficult analytical problems. This review presents a basic theory and illustrates the way in which SERS/SERRS has been developed for practical use.

  1. Resonance Raman Probes for Organelle-Specific Labeling in Live Cells

    NASA Astrophysics Data System (ADS)

    Kuzmin, Andrey N.; Pliss, Artem; Lim, Chang-Keun; Heo, Jeongyun; Kim, Sehoon; Rzhevskii, Alexander; Gu, Bobo; Yong, Ken-Tye; Wen, Shangchun; Prasad, Paras N.

    2016-06-01

    Raman microspectroscopy provides for high-resolution non-invasive molecular analysis of biological samples and has a breakthrough potential for dissection of cellular molecular composition at a single organelle level. However, the potential of Raman microspectroscopy can be fully realized only when novel types of molecular probes distinguishable in the Raman spectroscopy modality are developed for labeling of specific cellular domains to guide spectrochemical spatial imaging. Here we report on the design of a next generation Raman probe, based on BlackBerry Quencher 650 compound, which provides unprecedentedly high signal intensity through the Resonance Raman (RR) enhancement mechanism. Remarkably, RR enhancement occurs with low-toxic red light, which is close to maximum transparency in the biological optical window. The utility of proposed RR probes was validated for targeting lysosomes in live cultured cells, which enabled identification and subsequent monitoring of dynamic changes in this organelle by Raman imaging.

  2. Resonance Raman Probes for Organelle-Specific Labeling in Live Cells

    PubMed Central

    Kuzmin, Andrey N.; Pliss, Artem; Lim, Chang-Keun; Heo, Jeongyun; Kim, Sehoon; Rzhevskii, Alexander; Gu, Bobo; Yong, Ken-Tye; Wen, Shangchun; Prasad, Paras N.

    2016-01-01

    Raman microspectroscopy provides for high-resolution non-invasive molecular analysis of biological samples and has a breakthrough potential for dissection of cellular molecular composition at a single organelle level. However, the potential of Raman microspectroscopy can be fully realized only when novel types of molecular probes distinguishable in the Raman spectroscopy modality are developed for labeling of specific cellular domains to guide spectrochemical spatial imaging. Here we report on the design of a next generation Raman probe, based on BlackBerry Quencher 650 compound, which provides unprecedentedly high signal intensity through the Resonance Raman (RR) enhancement mechanism. Remarkably, RR enhancement occurs with low-toxic red light, which is close to maximum transparency in the biological optical window. The utility of proposed RR probes was validated for targeting lysosomes in live cultured cells, which enabled identification and subsequent monitoring of dynamic changes in this organelle by Raman imaging. PMID:27339882

  3. Pressure dependence of Hexanitrostilbene Raman/ electronic absorption spectra to validate DFT EOS

    NASA Astrophysics Data System (ADS)

    Farrow, Darcie; Alam, Kathleen; Martin, Laura; Fan, Hongyou; Kay, Jeffrey; Wixom, Ryan

    2015-06-01

    Due to its thermal stability and low vapor pressure, Hexanitrostilbene (HNS) is often used in high-temperature or vacuum applications as a detonator explosive or in mild detonating fuse. Toward improving the accuracy of the equation of state used in hydrodynamic simulations of the performance of HNS, we have measured the Raman and electronic absorption spectra of this material under static pressure in a diamond anvil cell. Density functional theory calculations were used to simulate the pressure dependence of the Raman/Electronic spectra along the Hugoniot and 300K isotherm for comparison and to aid in interpreting the data. We will discuss changes in the electronic structure of HNS under pressure, validation of a DFT predicted equation of state (EOS), and using this data as a basis for understanding future pulsed Raman measurements on dynamically compressed HNS samples.

  4. A sound absorptive element comprising an acoustic resonance nanofibrous membrane.

    PubMed

    Kalinova, Klara

    2015-01-01

    As absorption of sound of lower frequencies is quite problematic with fibrous material made up of coarser fibers, development of highly efficient sound absorption material is called for. This is why this work deals with the development of new high sound absorption material. To absorb the low frequencies, especially the structures based on resonance principle of nanofibrous layers are used, when through resonance of some elements the acoustic energy is transferred into thermal energy. The goal of the invention is achieved by a sound absorbing means which contains resonance membrane formed by a layer of polymeric nanofibers, which is attached to a frame. For production of nanofibrous membranes, the cord electrospinning was used. The resonance membrane was then, upon impact of sound waves of low frequency, brought into forced vibrations, whereby the kinetic energy of the membrane was converted into thermal energy by friction of individual nanofibers, by the friction of the membrane with ambient air and possibly with other layers of material arranged in its proximity, and some of the energy was also transmitted to the frame, through which the vibrations of the resonance membrane were damped. The density and shape of the mesh of frame formations determine the resonance frequency of the acoustic means. The goal of the invention is therefore to eliminate or at least reduce the disadvantages of the present state of the art and to propose sound absorbing means that would be capable of absorbing, with good results sounds in as broadest frequency range as possible. Here, we also discussed some patents relevant to the topic. PMID:25986230

  5. A sound absorptive element comprising an acoustic resonance nanofibrous membrane.

    PubMed

    Kalinova, Klara

    2015-01-01

    As absorption of sound of lower frequencies is quite problematic with fibrous material made up of coarser fibers, development of highly efficient sound absorption material is called for. This is why this work deals with the development of new high sound absorption material. To absorb the low frequencies, especially the structures based on resonance principle of nanofibrous layers are used, when through resonance of some elements the acoustic energy is transferred into thermal energy. The goal of the invention is achieved by a sound absorbing means which contains resonance membrane formed by a layer of polymeric nanofibers, which is attached to a frame. For production of nanofibrous membranes, the cord electrospinning was used. The resonance membrane was then, upon impact of sound waves of low frequency, brought into forced vibrations, whereby the kinetic energy of the membrane was converted into thermal energy by friction of individual nanofibers, by the friction of the membrane with ambient air and possibly with other layers of material arranged in its proximity, and some of the energy was also transmitted to the frame, through which the vibrations of the resonance membrane were damped. The density and shape of the mesh of frame formations determine the resonance frequency of the acoustic means. The goal of the invention is therefore to eliminate or at least reduce the disadvantages of the present state of the art and to propose sound absorbing means that would be capable of absorbing, with good results sounds in as broadest frequency range as possible. Here, we also discussed some patents relevant to the topic.

  6. High-resolution inverse Raman and resonant-wave-mixing spectroscopy

    SciTech Connect

    Rahn, L.A.

    1993-12-01

    These research activities consist of high-resolution inverse Raman spectroscopy (IRS) and resonant wave-mixing spectroscopy to support the development of nonlinear-optical techniques for temperature and concentration measurements in combustion research. Objectives of this work include development of spectral models of important molecular species needed to perform coherent anti-Stokes Raman spectroscopy (CARS) measurements and the investigation of new nonlinear-optical processes as potential diagnostic techniques. Some of the techniques being investigated include frequency-degenerate and nearly frequency-degenerate resonant four-wave-mixing (DFWM and NDFWM), and resonant multi-wave mixing (RMWM).

  7. Thin resonant structures for angle and polarization independent microwave absorption

    NASA Astrophysics Data System (ADS)

    Lockyear, Matthew J.; Hibbins, Alastair P.; Sambles, J. Roy; Hobson, Peter A.; Lawrence, Christopher R.

    2009-01-01

    We present a microwave absorbing structure comprised of an array of subwavelength radius copper disks, closely spaced from a ground plane by a low loss dielectric. Experiments and accompanying modeling demonstrate that this structure supports electromagnetic standing wave resonances associated with a cylindrical cavity formed by the volume immediately beneath each metal disk. Microwave absorption on resonance of these modes, at wavelengths much greater than the thickness of the structure, is dictated almost entirely by the radius of the disk and permittivity of the dielectric, being largely independent of the incident angle and polarization.

  8. Theoretical studies of resonance enhanced stimulated raman scattering (RESRS) of frequency doubled Alexandrite laser wavelengths in cesium vapor. Progress report

    SciTech Connect

    Lawandy, N.M.

    1986-10-01

    This work focused on understanding the effects of arbitrary transverse and longitudinal relaxation rates on the susceptibilities of coherently driven three-level systems. The approximation of a single relaxation rate often made in previous work is strongly invalidated by the variation in the spontaneous emission lifetime between various atomic level pairs in systems such as cesium. It is of great importance to the problem of nonlinear infrared generation to determine the dependence of both real and imaginary susceptibility on relaxation rates. The imaginary susceptibility on the pump transition determines the absorption of pump photons and the imaginary susceptibility on the laser transition determines the spectral dependence of the gain. This is of particular importance for pure Raman emission (i.e., absorption at linecenter of the gain transition) as it determines the tunability characteristics we are aiming to predict. The real susceptibility is important when cavities are used at the signal field as this will determine the loaded resonance of the Raman oscillator. Researchers show that in some cases which result from having different relaxation rates mode splitting may result, allowing more than one frequency to have the same Raman wavelength, possibly resulting in a temporal instability.

  9. Theoretical studies of Resonance Enhanced Stimulated Raman Scattering (RESRS) of frequency doubled Alexandrite laser wavelengths in cesium vapor

    NASA Technical Reports Server (NTRS)

    Lawandy, N. M.

    1986-01-01

    This work focused on understanding the effects of arbitrary transverse and longitudinal relaxation rates on the susceptibilities of coherently driven three-level systems. The approximation of a single relaxation rate often made in previous work is strongly invalidated by the variation in the spontaneous emission lifetime between various atomic level pairs in systems such as cesium. It is of great importance to the problem of nonlinear infrared generation to determine the dependence of both real and imaginary susceptibility on relaxation rates. The imaginary susceptibility on the pump transition determines the absorption of pump photons and the imaginary susceptibility on the laser transition determines the spectral dependence of the gain. This is of particular importance for pure Raman emission (i.e., absorption at linecenter of the gain transition) as it determines the tunability characteristics we are aiming to predict. The real susceptibility is important when cavities are used at the signal field as this will determine the loaded resonance of the Raman oscillator. Researchers show that in some cases which result from having different relaxation rates mode splitting may result, allowing more than one frequency to have the same Raman wavelength, possibly resulting in a temporal instability.

  10. Concentration-dependent surface-enhanced resonance Raman scattering of a porphyrin derivative adsorbed on colloidal silver particles.

    PubMed

    Chowdhury, Joydeep; Ghosh, Manash; Pal, Prabir; Misra, T N

    2003-07-01

    Surface-enhanced Raman spectra (SERS) of 5,10,15,20-tetrakis(1-decylpyridium-4-yl)-21H,23H-porphintetrabromide or Por 10 (H(2)Tdpyp) adsorbed on silver hydrosols are compared with the FTIR and resonance Raman spectrum (RRS) in the bulk and in solution. Comparative analysis of the RR and the FTIR spectra indicate that the molecule, in its free state, has D(2h) symmetry rather than C(2v). The SERS spectra, obtained on adsorption of this molecule on borohydride-reduced silver sol, indicate the formation of silver porphyrin. With the change in the adsorbate concentration, the SERS shows that the molecule changes its orientation on the colloidal silver surface. The appearance of longer wavelength band in the electronic absorption spectra of the sol has been attributed to the coagulation of colloidal silver particles in the sol. The long wavelength band is found to be red-shifted with the decrease in adsorbate concentration. The excitation profile study indicates that the resonance of the Raman excitation radiation with the original sol band is more important than that with the new aggregation band for the SERS activity. This indicates a large contribution of electromagnetic effect to surface enhancement.

  11. Electron paramagnetic resonance and optical absorption spectral studies on chalcocite

    NASA Astrophysics Data System (ADS)

    Reddy, S. Lakshmi; Fayazuddin, Md.; Frost, Ray L.; Endo, Tamio

    2007-11-01

    A chalcocite mineral sample of Shaha, Congo is used in the present study. An electron paramagnetic resonance (EPR) study on powdered sample confirms the presence of Mn(II), Fe(III) and Cu(II). Optical absorption spectrum indicates that Fe(III) impurity is present in octahedral structure whereas Cu(II) is present in rhombically distorted octahedral environment. Mid-infrared results are due to water and sulphate fundamentals.

  12. Electron paramagnetic resonance and optical absorption spectral studies on chalcocite.

    PubMed

    Reddy, S Lakshmi; Fayazuddin, Md; Frost, Ray L; Endo, Tamio

    2007-11-01

    A chalcocite mineral sample of Shaha, Congo is used in the present study. An electron paramagnetic resonance (EPR) study on powdered sample confirms the presence of Mn(II), Fe(III) and Cu(II). Optical absorption spectrum indicates that Fe(III) impurity is present in octahedral structure whereas Cu(II) is present in rhombically distorted octahedral environment. Mid-infrared results are due to water and sulphate fundamentals. PMID:17324611

  13. Double resonance surface enhanced Raman scattering substrates: an intuitive coupled oscillator model.

    PubMed

    Chu, Yizhuo; Wang, Dongxing; Zhu, Wenqi; Crozier, Kenneth B

    2011-08-01

    The strong coupling between localized surface plasmons and surface plasmon polaritons in a double resonance surface enhanced Raman scattering (SERS) substrate is described by a classical coupled oscillator model. The effects of the particle density, the particle size and the SiO2 spacer thickness on the coupling strength are experimentally investigated. We demonstrate that by tuning the geometrical parameters of the double resonance substrate, we can readily control the resonance frequencies and tailor the SERS enhancement spectrum. PMID:21934853

  14. Cyclotron resonant scattering and absorption. [in gamma ray bursts

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.; Daugherty, Joseph K.

    1991-01-01

    The relativistic cross-sections for first-order absorption and second-order scattering are compared to determine the conditions under which the absorption cross-section is a good approximation to the much more complex scattering cross-section for purposes of modeling cyclotron lines in gamma-ray bursts. Differences in both the cross-sections and the line profiles are presented for a range of field strengths, angles, and electron temperatures. The relative difference of the cross-sections at one line width from resonance was found to increase with field strength and harmonic number. The difference is also strongly dependent on the photon angle to the magnetic field. For the field strength, 1.7 x 10 to the 12th G, and the angle inferred from the Ginga burst features, absorption is an excellent approximation for the profiles at the first and second harmonics.

  15. Remote detection of trace effluents using Resonance Raman spectroscopy: Field results and evaluation

    SciTech Connect

    Sedlacek, A.J.; Chen, C.L.

    1995-10-01

    Resonance Raman spectroscopy (RRS) possesses many characteristics that are important for detecting, identifying and monitoring chemical effluents. Raman scattering is a coherent, inelastic, two-photon scattering process where an exciting photon of energy h{nu} promotes a molecule to a virtual level and the subsequently emitted photon is shifted in frequency in accordance with the rotational-vibrational structure of the irradiated species, thereby providing a unique fingerprint of the molecule. Under resonance enhancement, the Raman scattering cross-sections have been observed to increase up to 6 orders of magnitude above the normal scattering cross-sections, thereby providing the practical basis for a remote chemical sensor. Some of the other advantages that a Raman sensor possesses are: (1) very high selectivity (chemical specific fingerprints), (2) independence of the spectral fingerprint on the excitation wavelength (ability to monitor in the solar blind region), (3) chemical mixture fingerprints are the sum of its individual components (no spectral cross-talk), (4) near independence of the Raman fingerprint to its physical state (very similar spectra for gas, liquid, solid or solutions), (5) no absolute calibration is necessary because all Raman signals observed from a given species can be compared with the Raman signal for N{sub 2}, whose concentration is known very accurately, and (6) insensitivity of the Raman signature to environmental conditions (no quenching, or interference from water vapor). In this presentation, the technology of resonance Raman spectroscopy as applied to the detection of narcotics production activities will be presented along with some recent experimental results.

  16. Characterization of semiconductor core shell nanoparticles by resonant Raman scattering and photoluminescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Dzhagan, V. M.; Valakh, M. Ya.; Raevskaya, A. E.; Stroyuk, A. L.; Kuchmiy, S. Ya.; Zahn, D. R. T.

    2008-11-01

    Colloidal CdSe nanoparticles (NPs), passivated with CdS and ZnS, were characterized by resonant Raman scattering and photoluminescence (PL). The effect of the passivating shell, its volume and formation procedure on optical and vibrational spectra is discussed. Analyzing the Raman peaks due to optical phonons inside the core and those related to the core-shell interface allows some understanding of the relation between the core-shell structure and its PL properties to be achieved. In particular, a compositional intermixing at the core/shell interface of the NPs was deduced from the Raman spectra, which can noticeably affect their PL intensity.

  17. Investigation of the impact of fiber Bragg grating bandwidth on the efficiency of a Raman resonator

    NASA Astrophysics Data System (ADS)

    Henry, Leanne J.; Klopfer, Michael; Jain, Ravinder K.

    2015-03-01

    Significant spectral power leakage was found to occur around the high reflectivity fiber Bragg gratings (FBGs) defining a 1121 nm Raman resonator cavity comprised of PM 10/125 germanosilicate fiber. This cavity was part of a Raman system pumped with broad linewidth 1069 nm and seeded with narrow linewidth 1178 nm. The 1069 nm upon entering the resonator cavity was Raman converted to 1121 nm which then amplified the 1178 nm as it passed through the cavity. Spectral leakage of 1121 nm light from the resonator cavity resulted in sub-optimal amplification of 1178 nm which forced usage of longer resonator cavities having a decreased threshold for Stimulated Brillouin Scattering. Upon study of 1121 nm linewidth broadening as a function of resonator length for cavities employing 3 nm FBGs, differences in the percentage of 1121 nm power spectrally leaking past the output FBG as a function of the 1121 nm intracavity power propagating in the forward direction are not experimentally discernible for resonator cavities longer than 40 m. But, for cavity's shorter than 40 m, the percentage of 1121 nm power spectrally leaking past the output FBG decreased significantly for similar 1121 nm intracavity power levels. For all cavity lengths, a nearly linear relationship exists between percent 1121 nm power leakage and intracavity power levels. Also, cavities employing broader bandwidth FBGs experience less 1121 nm power leakage for similar 1121 nm intracavity power levels. Finally, modeling predictions of Raman system performance are greatly improved upon usage of experimentally derived effective FBG reflectivities.

  18. Identifying or measuring selected substances or toxins in a subject using resonant raman signals

    NASA Technical Reports Server (NTRS)

    Lambert, James L. (Inventor); Borchert, Mark S. (Inventor)

    2005-01-01

    Methods and systems of the present invention identify the presence of and/or the concentration of a selected analyte in a subject by: (a) illuminating a selected region of the eye of a subject with an optical excitation beam, wherein the excitation beam wavelength is selected to generate a resonant Raman spectrum of the selected analyte with a signal strength that is at least 100 times greater than Raman spectrums generated by non-resonant wavelengths and/or relative to signals of normal constituents present in the selected region of the eye; (b) detecting a resonant Raman spectrum corresponding to the selected illuminated region of the eye; and (c) identifying the presence, absence and/or the concentration of the selected analyte in the subject based on said detecting step. The apparatus may also be configured to be able to obtain biometric data of the eye to identify (confirm the identity of) the subject.

  19. Deep-UV surface-enhanced resonance Raman scattering of adenine on aluminum nanoparticle arrays.

    PubMed

    Jha, Shankar K; Ahmed, Zeeshan; Agio, Mario; Ekinci, Yasin; Löffler, Jörg F

    2012-02-01

    We report the ultrasensitive detection of adenine using deep-UV surface-enhanced resonance Raman scattering on aluminum nanostructures. Well-defined Al nanoparticle arrays fabricated over large areas using extreme-UV interference lithography exhibited sharp and tunable plasmon resonances in the UV and deep-UV wavelength ranges. Theoretical modeling based on the finite-difference time-domain method was used to understand the near-field and far-field optical properties of the nanoparticle arrays. Raman measurements were performed on adenine molecules coated uniformly on the Al nanoparticle arrays at a laser excitation wavelength of 257.2 nm. With this technique, less than 10 amol of label-free adenine molecules could be detected reproducibly in real time. Zeptomole (~30,000 molecules) detection sensitivity was readily achieved proving that deep-UV surface-enhanced resonance Raman scattering is an extremely sensitive tool for the detection of biomolecules.

  20. Multi-wavelength resonance Raman spectroscopy of bacteria to study the effects of growth condition

    NASA Astrophysics Data System (ADS)

    Kunapareddy, Nagapratima; Grun, Jacob; Lunsford, Robert; Gillis, David; Nikitin, Sergei; Wang, Zheng

    2012-06-01

    We will examine the use of multi-wavelength UV resonance-Raman signatures to identify the effects of growth phase on different types of bacteria. Gram positive and gram-negative species, Escherichia coli, Bacillus cereus, Citrobacter koseri and Citrobacter braakii were grown to logarithmic and stationary phases in different culture media. Raman spectra of bacteria were obtained by sequential illumination of samples between 220 and 260 nm; a range which encompasses the resonance frequencies of cellular components. In addition to the information contained in the single spectrum, this two-dimensional signature contains information reflecting variations in resonance cross sections with illumination wavelength. Results of our algorithms in identifying the differences between these germs are discussed. Preliminary results indicate that growth affects the Raman signature, but not to an extent that would negate identification of the species.

  1. Resonance Raman study of the A-band short-time photodissociation dynamics of 2,5-di-iodothiophene

    SciTech Connect

    Ruan Caibin; Zhu Hailin; Wang Huigang; Zheng Xuming; Phillips, David Lee

    2008-12-07

    Resonance Raman spectra were obtained for 2,5-di-iodothiophene in cyclohexane solution with excitation wavelengths in resonance with its A-band absorption. These spectra indicate that the Franck-Condon region photodissociation dynamics have multidimensional character with motion mostly along the nominal symmetric C{sub 2}C{sub 3}/C{sub 4}C{sub 5} stretch {nu}{sub 2} (1388 cm{sup -1}) of the thienyl ring and this is accompanied by motions along the nominal symmetric CSC stretch {nu}{sub 6} (640 cm{sup -1}), the nominal symmetric C-I stretch {nu}{sub 7} (187 cm{sup -1}), the nominal antisymmetric CSC stretch {nu}{sub 19} (728 cm{sup -1}), the nominal antisymmetric C{sub 2}C{sub 3}/C{sub 4}C{sub 5} stretch {nu}{sub 16} (1497 cm{sup -1}), the nominal C{sub 3}C{sub 4} stretch {nu}{sub 3} (1286 cm{sup -1}) and four other vibrational modes. A preliminary resonance Raman intensity analysis was done and the results for 2,5-di-iodothiophene were compared to previous results for 2-iodothiophene and di-iodomethane to discuss the mechanism of the symmetric breaking in the initial A-band photodissociation dynamics of 2,5-di-iodothiophene and 2-iodothiophene.

  2. Study on the resonance Raman scattering properties of β-carotene incorporated into SBA-15

    NASA Astrophysics Data System (ADS)

    Tan, Shishi; Zhang, Guannan; Shen, Aiguo; Hu, Juncheng; Hu, Jiming

    2010-10-01

    In this study, β-carotene, a resonance Raman active substance, was introduced into the large pore channel of rod-like SBA-15 for the first time. This novel resonance Raman active material has been characterized by small angle X-ray scattering (SAXS) and Brunauer-Emmett-Teller (BET) surface area analysis. The adsorption process did not show any influence on the microstructure of SBA-15 as well as its physicochemical characters. Excited by 514.5 nm laser, the resonance Raman signals of the products were demonstrated as well-defined Raman peaks at 1009, 1158 and 1514 cm -1, which should be assigned to the methyl rock (C-CH 3), carbon single-bond stretch (C-C) and carbon double-bond stretch (C dbnd C) normal modes, respectively. In addition, the internal standard method was utilized by resonance Raman spectroscopy to determine the adsorption capacity of mesoporous silicas for β-carotene using the results of UV-vis spectroscopy as a reference.

  3. Theory of resonant multiphonon Raman scattering in graphene monolayers

    NASA Astrophysics Data System (ADS)

    Basko, Denis; Aleiner, Igor

    2007-03-01

    The Raman spectrum of graphene consists of distinct narrow peaks corresponding to different optical phonon branches as well as their overtones [1]. We show how the relative intensities of the overtone peaks encode information about relative strengths of different inelastic scattering processes electrons are subject to. In particular, assuming that the most important processes are electron-phonon and electron-electron scattering, it is shown that one can deduce their relative interaction strengths from the Raman spectra. [1] A. C. Ferrari et al., Phys. Rev. Lett. 97, 187401 (2006); A. Gupta et al., cond-mat/0606593; D. Graf et al., cond-mat/0607562.

  4. Resonance absorption of propagating fast waves in a cold plasma

    NASA Technical Reports Server (NTRS)

    Hollweg, Joseph V.

    1990-01-01

    Absorption of propagating waves impinging on a surface in which the plasma and magnetic field may change is investigated by examining in depth the problem of a combination of cold plasma, uniform magnetic field and a surface density which varies linearly from zero at the left end to some finite value at the right end, beyond which the density is constant. Two cases are considered: one in which the plasma is a vacuum everywhere to the left of the surface (which may correspond to coronal conditions) and one in which the plasma density jumps to a very large value to the left of the surface (which may mimic the magnetosphere with the dense region at the left corresponding to the plasmasphere). A complete discussion of the resonance absorption of propagating fast waves for the case considered by Kiveloson and Southwood (1986) is presented, emphasizing approximate analytical results whenever possible; these results are then compared with exact numerical solutions.

  5. Towards higher stability of resonant absorption measurements in pulsed plasmas.

    PubMed

    Britun, Nikolay; Michiels, Matthieu; Snyders, Rony

    2015-12-01

    Possible ways to increase the reliability of time-resolved particle density measurements in pulsed gaseous discharges using resonant absorption spectroscopy are proposed. A special synchronization, called "dynamic source triggering," between a gated detector and two pulsed discharges, one representing the discharge of interest and another being used as a reference source, is developed. An internal digital delay generator in the intensified charge coupled device camera, used at the same time as a detector, is utilized for this purpose. According to the proposed scheme, the light pulses from the reference source follow the gates of detector, passing through the discharge of interest only when necessary. This allows for the utilization of short-pulse plasmas as reference sources, which is critical for time-resolved absorption analysis of strongly emitting pulsed discharges. In addition to dynamic source triggering, the reliability of absorption measurements can be further increased using simultaneous detection of spectra relevant for absorption method, which is also demonstrated in this work. The proposed methods are illustrated by the time-resolved measurements of the metal atom density in a high-power impulse magnetron sputtering (HiPIMS) discharge, using either a hollow cathode lamp or another HiPIMS discharge as a pulsed reference source. PMID:26724013

  6. Towards higher stability of resonant absorption measurements in pulsed plasmas

    SciTech Connect

    Britun, Nikolay; Michiels, Matthieu; Snyders, Rony

    2015-12-15

    Possible ways to increase the reliability of time-resolved particle density measurements in pulsed gaseous discharges using resonant absorption spectroscopy are proposed. A special synchronization, called “dynamic source triggering,” between a gated detector and two pulsed discharges, one representing the discharge of interest and another being used as a reference source, is developed. An internal digital delay generator in the intensified charge coupled device camera, used at the same time as a detector, is utilized for this purpose. According to the proposed scheme, the light pulses from the reference source follow the gates of detector, passing through the discharge of interest only when necessary. This allows for the utilization of short-pulse plasmas as reference sources, which is critical for time-resolved absorption analysis of strongly emitting pulsed discharges. In addition to dynamic source triggering, the reliability of absorption measurements can be further increased using simultaneous detection of spectra relevant for absorption method, which is also demonstrated in this work. The proposed methods are illustrated by the time-resolved measurements of the metal atom density in a high-power impulse magnetron sputtering (HiPIMS) discharge, using either a hollow cathode lamp or another HiPIMS discharge as a pulsed reference source.

  7. Towards higher stability of resonant absorption measurements in pulsed plasmas

    NASA Astrophysics Data System (ADS)

    Britun, Nikolay; Michiels, Matthieu; Snyders, Rony

    2015-12-01

    Possible ways to increase the reliability of time-resolved particle density measurements in pulsed gaseous discharges using resonant absorption spectroscopy are proposed. A special synchronization, called "dynamic source triggering," between a gated detector and two pulsed discharges, one representing the discharge of interest and another being used as a reference source, is developed. An internal digital delay generator in the intensified charge coupled device camera, used at the same time as a detector, is utilized for this purpose. According to the proposed scheme, the light pulses from the reference source follow the gates of detector, passing through the discharge of interest only when necessary. This allows for the utilization of short-pulse plasmas as reference sources, which is critical for time-resolved absorption analysis of strongly emitting pulsed discharges. In addition to dynamic source triggering, the reliability of absorption measurements can be further increased using simultaneous detection of spectra relevant for absorption method, which is also demonstrated in this work. The proposed methods are illustrated by the time-resolved measurements of the metal atom density in a high-power impulse magnetron sputtering (HiPIMS) discharge, using either a hollow cathode lamp or another HiPIMS discharge as a pulsed reference source.

  8. Resonance Raman Spectroscopy of Extreme Nanowires and Other 1D Systems.

    PubMed

    Smith, David C; Spencer, Joseph H; Sloan, Jeremy; McDonnell, Liam P; Trewhitt, Harrison; Kashtiban, Reza J; Faulques, Eric

    2016-01-01

    This paper briefly describes how nanowires with diameters corresponding to 1 to 5 atoms can be produced by melting a range of inorganic solids in the presence of carbon nanotubes. These nanowires are extreme in the sense that they are the limit of miniaturization of nanowires and their behavior is not always a simple extrapolation of the behavior of larger nanowires as their diameter decreases. The paper then describes the methods required to obtain Raman spectra from extreme nanowires and the fact that due to the van Hove singularities that 1D systems exhibit in their optical density of states, that determining the correct choice of photon excitation energy is critical. It describes the techniques required to determine the photon energy dependence of the resonances observed in Raman spectroscopy of 1D systems and in particular how to obtain measurements of Raman cross-sections with better than 8% noise and measure the variation in the resonance as a function of sample temperature. The paper describes the importance of ensuring that the Raman scattering is linearly proportional to the intensity of the laser excitation intensity. It also describes how to use the polarization dependence of the Raman scattering to separate Raman scattering of the encapsulated 1D systems from those of other extraneous components in any sample. PMID:27168195

  9. Monitoring and trace detection of hazardous waste and toxic chemicals using resonance Raman spectroscopy

    SciTech Connect

    Sedlacek, A.J. III; Dougherty, D.R.; Chen, C.L.

    1993-04-01

    Raman scattering is a coherent, inelastic, two-photon process, which shifts the frequency of an outgoing photon according to the vibrational structure of the irradiated species, thereby providing a unique fingerprint of the molecule. When involving an allowed electronic transition (resonance Raman), this scattering cross section can be enhanced by 10{sup 4} to 10{sup 6} and provides the basis for a viable technique that can monitor and detect trace quantities of hazardous wastes and toxic chemicals. Resonance Raman spectroscopy (RRS) possesses many of the ideal characteristics for monitoring and detecting of hazardous waste and toxic chemicals. Some of these traits are: (1) very high selectivity (chemical specific fingerprints); (2) independence from the excitation wavelength (ability to monitor in the solar blind region); (3) chemical mixture fingerprints are the sum of its individual components (no spectral cross-talk); (4) near independence of the Raman fingerprint to its physical state (very similar spectra for gas, liquid, solid and solutions -- either bulk or aerosols); and (5) insensitivity of the Raman signature to environmental conditions (no quenching). Data from a few chemicals will be presented which illustrate these features. In cases where background fluorescence accompanies the Raman signals, an effective frequency modulation technique has been developed, which can completely eliminate this interference.

  10. Monitoring and trace detection of hazardous waste and toxic chemicals using resonance Raman spectroscopy

    SciTech Connect

    Sedlacek, A.J. III; Dougherty, D.R.; Chen, C.L.

    1993-01-01

    Raman scattering is a coherent, inelastic, two-photon process, which shifts the frequency of an outgoing photon according to the vibrational structure of the irradiated species, thereby providing a unique fingerprint of the molecule. When involving an allowed electronic transition (resonance Raman), this scattering cross section can be enhanced by 10[sup 4] to 10[sup 6] and provides the basis for a viable technique that can monitor and detect trace quantities of hazardous wastes and toxic chemicals. Resonance Raman spectroscopy (RRS) possesses many of the ideal characteristics for monitoring and detecting of hazardous waste and toxic chemicals. Some of these traits are: (1) very high selectivity (chemical specific fingerprints); (2) independence from the excitation wavelength (ability to monitor in the solar blind region); (3) chemical mixture fingerprints are the sum of its individual components (no spectral cross-talk); (4) near independence of the Raman fingerprint to its physical state (very similar spectra for gas, liquid, solid and solutions -- either bulk or aerosols); and (5) insensitivity of the Raman signature to environmental conditions (no quenching). Data from a few chemicals will be presented which illustrate these features. In cases where background fluorescence accompanies the Raman signals, an effective frequency modulation technique has been developed, which can completely eliminate this interference.

  11. Resonance Raman Spectroscopy of Extreme Nanowires and Other 1D Systems

    PubMed Central

    Smith, David C.; Spencer, Joseph H.; Sloan, Jeremy; McDonnell, Liam P.; Trewhitt, Harrison; Kashtiban, Reza J.; Faulques, Eric

    2016-01-01

    This paper briefly describes how nanowires with diameters corresponding to 1 to 5 atoms can be produced by melting a range of inorganic solids in the presence of carbon nanotubes. These nanowires are extreme in the sense that they are the limit of miniaturization of nanowires and their behavior is not always a simple extrapolation of the behavior of larger nanowires as their diameter decreases. The paper then describes the methods required to obtain Raman spectra from extreme nanowires and the fact that due to the van Hove singularities that 1D systems exhibit in their optical density of states, that determining the correct choice of photon excitation energy is critical. It describes the techniques required to determine the photon energy dependence of the resonances observed in Raman spectroscopy of 1D systems and in particular how to obtain measurements of Raman cross-sections with better than 8% noise and measure the variation in the resonance as a function of sample temperature. The paper describes the importance of ensuring that the Raman scattering is linearly proportional to the intensity of the laser excitation intensity. It also describes how to use the polarization dependence of the Raman scattering to separate Raman scattering of the encapsulated 1D systems from those of other extraneous components in any sample. PMID:27168195

  12. Characterization of the pigment xanthomonadin in the bacterial genus Xanthomonas using micro- and resonance Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Paret, Mathews L.; Sharma, Shiv K.; Misra, Anupam K.; Acosta, Tayro; deSilva, Asoka S.; Vowell, Tomie; Alvarez, Anne M.

    2012-06-01

    We used micro- and resonance Raman spectroscopy with 785 nm and 514.5 nm laser excitation, respectively, to characterize a plant pathogenic bacteria, Xanthomonas axonopodis pv. dieffenbachiae D150. The bacterial genus Xathomonas is closely related to bacterial genus Stenotrophomonas that causes an infection in humans. This study has identified for the first time the unique Raman spectra of the carotenoid-like pigment xanthomonadin of the Xanthomonas strain. Xanthomonadin is a brominated aryl-polyene pigment molecule similar to carotenoids. Further studies were conducted using resonance Raman spectroscopy with 514.5 nm laser excitation on several strains of the bacterial genus Xanthomonas isolated from numerous plants from various geographical locations. The current study revealed that the Raman bands representing the vibrations (v1, v2, v3) of the polyene chain of xanthomonadin are 1003-1005 (v3), 1135-1138 (v2), and 1530 (v1). Overtone bands representing xanthomonadin were identified as 2264-2275 (2v2), and combinational bands at 2653-2662 (v1+ v2). The findings from this study validate our previous finding that the Raman fingerprints of xanthomonadin are unique for the genus Xanthomonas. This facilitates rapid identification (~5 minutes) of Xanthomonas spp. from bacterial culture plates. The xanthomonadin marker is different from Raman markers of many other bacterial genus including Agrobacterium, Bacillus, Clavibacter, Enterobacter, Erwinia, Microbacterium, Paenibacillus, and Ralstonia. This study also identified Xanthomonas spp. from bacterial strains isolated from a diseased wheat sample on a culture plate.

  13. Resonance Raman Studies Of Lactoperoxidase And Sulflactoperoxidase: Drug-Induced Chlorin Formation

    NASA Astrophysics Data System (ADS)

    Andersson, Laura A.

    1989-07-01

    Thyroid peroxidase (TPO) is a membrane-bound heme enzyme that catalyzes iodination and coupling of thyroglobulin tyrosine residues in the biosynthesis of thyroid hormones. The soluble heme enzyme lactoperoxidase (LPO) also iodinates tyrosine efficiently and serves as a functional model for TPO. Whereas horseradish peroxidase oxidizes sulfur-containing compounds, e.g., cysteine and glutathione, these compounds interact with LPO and TPO without oxidation. Indeed, clinical treatment of thyroid disease involves the use of sulfur-containing drugs (goitrogens) to inactivate TPO. Reactions of TPO and LPO with goitrogens result in enzyme inhibition, in a process similar to the conversion of myoglobin to sulf-myoglobin (sulf-Mb). We have examined the electronic absorption and resonance Raman (RR) spectral properties of LPO treated with the potent antithyroid drug methylmercaptoimidazole (MMi). Interaction of LPO with MMi yields a stable, emerald green complex (SLPO (MNi]). The electronic absorption spectra of SLPO [MMi] are similar to those of sulf-Mb (which has a sulfur-modified iron chlorin macrocycle), and to those of the naturally occurring Escherichia coli and Neurospora crassa chlorin catalases. The Soret excitation RR spectrum of the SLPO [DIM] complex is distinct from that of native LPO, but is consistent with the spectral pattern for metallochlorins established by our laboratory. The SLPO [NW RR pattern is also analogous to that of chlorin-containing proteins such as the isomeric sulf-Mb's, myeloperoxidase, and the E. coli and N. crassa catalases. These data strongly suggest that MMi treatment of LPO results in conversion of the porphyrin prosthetic moiety to an iron chlorin. We infer that clinical treatment of thyroid disorders with the goitrogen drug MMi similarly converts the porphyrin prosthetic moiety of thyroid peroxidase to an iron chlorin. Spectral differences between sulf-Mb and SLPO [MMI] are particularly intriguing and suggest structural differences

  14. Photodetector with absorbing region having resonant periodic absorption between reflectors

    DOEpatents

    Bryan, Robert P.; Olbright, Gregory R.; Brennan, Thomas M.; Tsao, Jeffrey Y.

    1995-02-14

    A photodetector that is responsive to a wavelength or wavelengths of interest which have heretofore been unrealized. The photodetector includes a resonant cavity structure bounded by first and second reflectors, the resonant cavity structure being resonant at the wavelength or wavelengths of interest for containing a plurality of standing waves therein. The photodetector further includes a radiation absorbing region disposed within the resonant cavity structure, the radiation absorbing region including a plurality of radiation absorbing layers spaced apart from one another by a distance substantially equal to a distance between antinodes of adjacent ones of the standing waves. Each of radiation absorbing layers is spatially positioned at a location of one of the antinodes of one of the standing waves such that radiation absorption is enhanced. The radiation absorbing layers may be either bulk layers or quantum wells includes a plurality of layers, each of which is comprised of a strained layer of InGaAs. Individual ones of the InGaAs layers are spaced apart from one another by a GaAs barrier layer.

  15. Photodetector with absorbing region having resonant periodic absorption between reflectors

    DOEpatents

    Bryan, R.P.; Olbright, G.R.; Brennan, T.M.; Tsao, J.Y.

    1995-02-14

    A photodetector is disclosed that is responsive to a wavelength or wavelengths of interest which have heretofore been unrealized. The photodetector includes a resonant cavity structure bounded by first and second reflectors, the resonant cavity structure being resonant at the wavelength or wavelengths of interest for containing a plurality of standing waves therein. The photodetector further includes a radiation absorbing region disposed within the resonant cavity structure, the radiation absorbing region including a plurality of radiation absorbing layers spaced apart from one another by a distance substantially equal to a distance between antinodes of adjacent ones of the standing waves. Each of radiation absorbing layers is spatially positioned at a location of one of the antinodes of one of the standing waves such that radiation absorption is enhanced. The radiation absorbing layers may be either bulk layers or quantum wells includes a plurality of layers, each of which is comprised of a strained layer of InGaAs. Individual ones of the InGaAs layers are spaced apart from one another by a GaAs barrier layer. 11 figs.

  16. Resonance Raman characterization of the radical anion and triplet states of zinc tetraphenylporphine

    SciTech Connect

    Reed, R.A.; Purrello, R.; Prendergast, K.; Spiro, T.G. )

    1991-11-28

    The photophysical properties of metalloporphyrins are important to a range of current research areas, ranging from solar energy conversion to photodynamic therapy. Resonance Raman (RR) spectra are reported for the anion radical and for the photoexcited triplet state of ZnTPP. RR spectra were obtained by excitation at 457.9 nm, at the anion absorption band maximum. Bands were assigned with the aid of pyrrole-d[sub 8] and phenyl-d[sub 20] isotopomers. The pattern of isotope shifts and polarizations was found to be quite similar to that of the neutral parent, ZnTPP. The frequency shift pattern is discussed in terms of the expectations for placing an electron in the e[sub g]* orbital, including the anticipated Jahn-Teller (J-T) effect. Although band overlaps make depolarization ratios difficult to quantitate, the [nu][sub 10] band is found to be essentially depolarized, indicating that the J-T effect is dynamic, rather than static in character, at least with respect to stretching of the C[sub a]C[sub m] bonds. The [nu][sub 2] and [nu][sub 10] downshifts are attributable to porphyrin core expansion upon reduction, but the [nu][sub 27] and [nu][sub 29] reductions are probably manifestations of the J-T effect. Triplet-state RR spectra were produced with 416-nm photolysis and 459-nm probe pulses (7 ns). The RR peaks were assigned via their polarizations and the d[sub 8] and d[sub 20] isotopomer shifts. The spectrum contains three strong bands of predominantly phenyl character. Their frequencies are unshifted relative to the ground state, implying negligible electronic involvement of the phenyl groups in the T[sub 1] state, but their enhancements indicate substantial involvement in the resonant T[sub n] state. This state is suggested to be produced by charge transfer from the porphyrin e[sub g]* to the phenyl [pi]* orbitals.

  17. FTIR difference and resonance Raman spectroscopy of rhodopsins with applications to optogenetics

    NASA Astrophysics Data System (ADS)

    Saint Clair, Erica C.

    The major aim of this thesis is to investigate the molecular basis for the function of several types of rhodopsins with special emphasis on their application to the new field of optogenetics. Rhodopsins are transmembrane biophotonic proteins with 7 alpha-helices and a retinal chromophore. Studies included Archaerhodopsin 3 (AR3), a light driven proton pump similar to the extensively studied bacteriorhodopsin (BR); channelrhodopsins 1 and 2, light-activated ion channels; sensory rhodopsin II (SRII), a light-sensing protein that modulates phototaxis used in archaebacteria; and squid rhodopsins (sRho), the major photopigment in squid vision and a model for human melanopsin, which controls circadian rhythms. The primary techniques used in these studies were FTIR difference spectroscopy and resonance Raman spectroscopy. These techniques, in combination with site directed mutagenesis and other biochemical methodologies produced new knowledge regarding the structural changes of the retinal chromophore, the location and function of internal water molecules as well as specific amino acids and peptide backbone. Specialized techniques were developed that allowed rhodopsins to be studied in intact membrane environments and in some cases in vivo measurements were made on rhodopsin heterologously expressed in E. coli thus allowing the effects of interacting proteins and membrane potential to be investigated. Evidence was found that the local environment of one or more internal water molecules in SRII is altered by interaction with its cognate transducer, HtrII, and is also affected by the local lipid environment. In the case of AR3, many of the broad IR continuum absorption changes below 3000 cm -1, assigned to networks of water molecules involved in proton transport through cytoplasmic and extracellular portions in BR, were found to be very similar to BR. Bands assigned to water molecules near the Schiff base postulated to be involved in proton transport were, however, shifted

  18. Stimulated Raman scattering from individual water and ethanol droplets at morphology-dependent resonances.

    PubMed

    Snow, J B; Qian, S X; Chang, R K

    1985-01-01

    Stimulated Raman scattering (SRS) from an individual liquid droplet (~30-microm radius) has been observed for H(2)O, D(2)O, and ethanol. The occurrence of a series of spectrally narrow peaks that are regularly spaced in wavelength is consistent with morphology-dependent resonances of the droplet, which acts as an optical resonator. The input intensity required to achieve the SRS threshold for the droplet is considerably less than that for the liquid in an optical cell.

  19. Raman and absorption spectrophotometric studies of selected lanthanide, californium-doped lanthanide, and actinide trihalides in the solid state

    SciTech Connect

    Wilmarth, W.R.

    1988-03-01

    The solid-state absorption spectra of Cf(III) ions as a dopant in lanthanide trihalide hosts (LnCl/sub 3/: Ln = Ce, Sm, and Y; LnBr/sub 3/: Ln = Ce, Sm, Tb, and Y; LnI/sub 3/: Ln = Ce and Y) have been recorded. The spectra of Cf(III) have been correlated with the various crystal structures. The phonon Raman spectra and solid-state absorption spectra of PmF/sub 3/, PmCl/sub 3/, PmBr/sub 3/, and two crystal modifications of PmI/sub 3/ have been recorded. Symmetry assignments have been made for the Raman-active bands for these trihalides and also the sesquioxide. The room-temperature absorption spectra have been correlated to crystal field effects. The symmetry assignments of the Raman-active phonon modes have been made based on polarized Raman spectra from single crystals of YF/sub 3/-type orthorhombic TbF/sub 3/ and PuBr/sub 3/-type orthorhombic NdBr/sub 3/. Raman spectra of other isostructural lanthanide compounds have been recorded and compared. Symmetry assignments for these compounds have been made by analogy to the single-crystal assignments. Raman spectra have been obtained and catalogued for a number of actinide compounds. Symmetry assignments have been made for the observed Raman-active phonon bands in this work based on the assignments made for isostructural lanthanide compounds. 29 figs., 22 tabs.

  20. Phase-locking transition in Raman combs generated with whispering gallery mode resonators.

    PubMed

    Lin, Guoping; Chembo, Yanne K

    2016-08-15

    We investigate the mechanisms leading to phase locking in Raman optical frequency combs generated with ultrahigh Q crystalline whispering gallery mode disk resonators. We show that several regimes can be triggered depending on the pumping conditions, such as single-frequency Raman lasing, multimode operation involving more than one family of cavity eigenmodes, and Kerr-assisted Raman frequency comb generation. The phase locking and coherence of the combs are experimentally monitored through the measurement of beat signal spectra. These phase-locked combs, which feature high coherence and wide spectral spans, are obtained with pump powers in the range of a few tens of mW. In particular, Raman frequency combs with multiple free-spectral range spacings are reported, and the measured beat signal in the microwave domain features a 3 dB linewidth smaller than 50 Hz, thereby indicating phase locking. PMID:27519071

  1. Phase-locking transition in Raman combs generated with whispering gallery mode resonators.

    PubMed

    Lin, Guoping; Chembo, Yanne K

    2016-08-15

    We investigate the mechanisms leading to phase locking in Raman optical frequency combs generated with ultrahigh Q crystalline whispering gallery mode disk resonators. We show that several regimes can be triggered depending on the pumping conditions, such as single-frequency Raman lasing, multimode operation involving more than one family of cavity eigenmodes, and Kerr-assisted Raman frequency comb generation. The phase locking and coherence of the combs are experimentally monitored through the measurement of beat signal spectra. These phase-locked combs, which feature high coherence and wide spectral spans, are obtained with pump powers in the range of a few tens of mW. In particular, Raman frequency combs with multiple free-spectral range spacings are reported, and the measured beat signal in the microwave domain features a 3 dB linewidth smaller than 50 Hz, thereby indicating phase locking.

  2. Surface-Enhanced Raman Scattering Using Silica Whispering-Gallery Mode Resonators

    NASA Technical Reports Server (NTRS)

    Anderson, Mark S.

    2013-01-01

    The motivation of this work was to have robust spectroscopic sensors for sensitive detection and chemical analysis of organic and molecular compounds. The solution is to use silica sphere optical resonators to provide surface-enhanced spectroscopic signal. Whispering-gallery mode (WGM) resonators made from silica microspheres were used for surface-enhanced Raman scattering (SERS) without coupling to a plasmonic mechanism. Large Raman signal enhancement is observed by exclusively using 5.08-micron silica spheres with 785-nm laser excitation. The advantage of this non-plasmonic approach is that the active substrate is chemically inert silica, thermally stable, and relatively simple to fabricate. The Raman signal enhancement is broadly applicable to a wide range of molecular functional groups including aliphatic hydrocarbons, siloxanes, and esters. Applications include trace organic analysis, particularly for in situ planetary instruments that require robust sensors with consistent response.

  3. Pressure-induced depolarization and resonance in Raman scattering of single-crystalline boron carbide

    SciTech Connect

    Guo Junjie; Zhang Ling; Fujita, Takeshi; Chen Mingwei; Goto, Takashi

    2010-02-01

    We report polarized and resonant Raman scattering of single-crystal boron carbide (B{sub 4}C) at high pressures. Significant intensity enhancements of 270 and 1086 cm{sup -1} Raman bands of B{sub 4}C have been observed at quasihydrostatic pressures higher than approx20 GPa. The pressure-induced intensity change of the 1086 cm{sup -1} band is mainly due to the resonance between excitation energy and electronic transition, whereas the intensity change of 270 cm{sup -1} band is caused by the depolarization effect. Importantly, the first-order phase transition has not been found at high quasihydrostatic pressures and all the Raman intensity changes along with the corresponding high-pressure lattice distortion can be recovered during unloading.

  4. Stimulated resonance Raman scattering from single crystals of a thiophene/phenylene co-oligomer

    NASA Astrophysics Data System (ADS)

    Yanagi, Hisao; Yoshiki, Atsutoshi; Hotta, Shu; Kobayashi, Shunsuke

    2003-09-01

    We have investigated the stimulated resonance Raman scattering from single crystals of a thiophene/phenylene co-oligomer. The very narrow lines [full width at half maximum (FWHM)=11-20 cm-1] are observed in the same spectral regions where the spectrally narrowed emissions (FWHM≈300 cm-1) occur upon excitation with intense laser pulse. We related these modes to the stimulated resonance Raman scattering. Two lines of Raman shifts of 1466 and 1605 cm-1 are of molecular origin. Another line with an energy shift of ˜1260 cm-1 from excitation energy, on the other hand, implies the presence of the coherence of crystal origin. The associated split lines accompanying this mode are thought to constitute the longitudinal modes in the Fabry-Pérot cavity naturally formed in the crystals.

  5. Off-resonance energy absorption in a linear Paul trap due to mass selective resonant quenching.

    PubMed

    Sivarajah, I; Goodman, D S; Wells, J E; Narducci, F A; Smith, W W

    2013-11-01

    Linear Paul traps (LPT) are used in many experimental studies such as mass spectrometry, atom-ion collisions, and ion-molecule reactions. Mass selective resonant quenching (MSRQ) is implemented in LPT either to identify a charged particle's mass or to remove unwanted ions from a controlled experimental environment. In the latter case, MSRQ can introduce undesired heating to co-trapped ions of different mass, whose secular motion is off resonance with the quenching ac field, which we call off-resonance energy absorption (OREA). We present simulations and experimental evidence that show that the OREA increases exponentially with the number of ions loaded into the trap and with the amplitude of the off-resonance external ac field. PMID:24289382

  6. Resonance Raman Spectroscopy of Beta-Carotene and Lycopene: A Physical Chemistry Experiment.

    ERIC Educational Resources Information Center

    Hoskins, L. C.

    1984-01-01

    Discusses the theory of resonance Raman (RR) spectroscopy as it applies to beta-carotene and lycopene pigments (found in tomatoes and carrots, respectively). Also discusses an experiment which demonstrates the theoretical principles involved. The experiment has been tested over a three-year period and has received excellent acceptance by physical…

  7. On the Increasing Fragility of Human Teeth with Age: ADeep-Ultraviolet Resonance Raman Study

    SciTech Connect

    Ager III, J.W.; Nalla, R.K.; Balooch, G.; Kim, G.; Pugach, M.; Habelitz, S.; Marshall, G.W.; Kinney, J.H.; Ritchie, R.O.

    2006-07-14

    Ultraviolet resonance Raman spectroscopy (UVRRS) using 244nm excitation was used to investigate the impact of aging on humandentin. The intensity of a spectroscopic feature from the peptide bondsin the collagen increases with tissue age, similar to a finding reportedpreviously for human cortical bone.

  8. Proton Transfer of Guanine Radical Cations Studied by Time-Resolved Resonance Raman Spectroscopy Combined with Pulse Radiolysis.

    PubMed

    Choi, Jungkweon; Yang, Cheolhee; Fujitsuka, Mamoru; Tojo, Sachiko; Ihee, Hyocherl; Majima, Tetsuro

    2015-12-17

    The oxidation of guanine (G) is studied by using transient absorption and time-resolved resonance Raman spectroscopies combined with pulse radiolysis. The transient absorption spectral change demonstrates that the neutral radical of G (G(•)(-H(+))), generated by the deprotonation of G radical cation (G(•+)), is rapidly converted to other G radical species. The formation of this species shows the pH dependence, suggesting that it is the G radical cation (G(•+))' formed from the protonation at the N7 of G(•)(-H(+)). On one hand, most Raman bands of (G(•+))' are up-shifted relative to those of G, indicating the increase in the bonding order of pyrimidine (Pyr) and imidazole rings. The (G(•+))' exhibits the characteristic CO stretching mode at ∼1266 cm(-1) corresponding to a C-O single bond, indicating that the unpaired electron in (G(•+))' is localized on the oxygen of the Pyr ring. PMID:26632994

  9. Surface-enhanced resonance Raman scattering of cytochrome P450-2D6 on coated silver hydrosols.

    PubMed

    Bonifacio, Alois; Keizers, Peter H J; Vermeulen, Nico P E; Commandeur, Jan N M; Gooijer, Cees; van der Zwan, Gert

    2007-02-13

    Surface-enhanced resonance Raman scattering (SERRS) from dilute solutions (down to nanomolar concentrations) of human mono-oxygenase CYP2D6 is observed using aqueous dispersions of Ag nanoparticles (hydrosol) coated with self-assembled monolayers (SAMs) of mercaptoalkanoic acids of two different lengths. From a direct comparison with its resonance Raman spectrum in solution, CYP2D6 appears to fully retain its native structure upon adsorption on coated hydrosol through electrostatic interaction, while a structural change in the active site is observed when uncoated citrate-reduced hydrosol is used. Using SERRS on these biocompatible coated hydrosols, the effects of dextromethorphan on the enzyme's active site can be observed, demonstrating that CYP2D6 ability of binding substrates is preserved. Moreover, by tuning the wavelength of the exciting laser away from the main absorption band of the heme, the vibrational bands of the SAM coating are observed and analyzed to see how the presence of the protein affects the SAM structure.

  10. Multidimensional resonance raman spectroscopy by six-wave mixing in the deep UV

    SciTech Connect

    Molesky, Brian P.; Giokas, Paul G.; Guo, Zhenkun; Moran, Andrew M.

    2014-09-21

    Two-dimensional (2D) resonance Raman spectroscopies hold great potential for uncovering photoinduced relaxation processes in molecules but are not yet widely applied because of technical challenges. Here, we describe a newly developed 2D resonance Raman experiment operational at the third-harmonic of a Titanium-Sapphire laser. High-sensitivity and rapid data acquisition are achieved by combining spectral interferometry with a background-free (six-pulse) laser beam geometry. The third-harmonic laser pulses are generated in a filament produced by the fundamental and second-harmonic pulses in neon gas at pressures up to 35 atm. The capabilities of the setup are demonstrated by probing ground-state wavepacket motions in triiodide. The information provided by the experiment is explored with two different representations of the signal. In one representation, Fourier transforms are carried out with respect to the two experimentally controlled delay times to obtain a 2D Raman spectrum. Further insights are derived in a second representation by dispersing the signal pulse in a spectrometer. It is shown that, as in traditional pump-probe experiments, the six-wave mixing signal spectrum encodes the wavepacket's position by way of the (time-evolving) emission frequency. Anharmonicity additionally induces dynamics in the vibrational resonance frequency. In all cases, the experimental signals are compared to model calculations based on a cumulant expansion approach. This study suggests that multi-dimensional resonance Raman spectroscopies conducted on systems with Franck-Condon active modes are fairly immune to many of the technical issues that challenge off-resonant 2D Raman spectroscopies (e.g., third-order cascades) and photon-echo experiments in the deep UV (e.g., coherence spikes). The development of higher-order nonlinear spectroscopies operational in the deep UV is motivated by studies of biological systems and elementary organic photochemistries.

  11. Multidimensional resonance Raman spectroscopy by six-wave mixing in the deep UV.

    PubMed

    Molesky, Brian P; Giokas, Paul G; Guo, Zhenkun; Moran, Andrew M

    2014-09-21

    Two-dimensional (2D) resonance Raman spectroscopies hold great potential for uncovering photoinduced relaxation processes in molecules but are not yet widely applied because of technical challenges. Here, we describe a newly developed 2D resonance Raman experiment operational at the third-harmonic of a Titanium-Sapphire laser. High-sensitivity and rapid data acquisition are achieved by combining spectral interferometry with a background-free (six-pulse) laser beam geometry. The third-harmonic laser pulses are generated in a filament produced by the fundamental and second-harmonic pulses in neon gas at pressures up to 35 atm. The capabilities of the setup are demonstrated by probing ground-state wavepacket motions in triiodide. The information provided by the experiment is explored with two different representations of the signal. In one representation, Fourier transforms are carried out with respect to the two experimentally controlled delay times to obtain a 2D Raman spectrum. Further insights are derived in a second representation by dispersing the signal pulse in a spectrometer. It is shown that, as in traditional pump-probe experiments, the six-wave mixing signal spectrum encodes the wavepacket's position by way of the (time-evolving) emission frequency. Anharmonicity additionally induces dynamics in the vibrational resonance frequency. In all cases, the experimental signals are compared to model calculations based on a cumulant expansion approach. This study suggests that multi-dimensional resonance Raman spectroscopies conducted on systems with Franck-Condon active modes are fairly immune to many of the technical issues that challenge off-resonant 2D Raman spectroscopies (e.g., third-order cascades) and photon-echo experiments in the deep UV (e.g., coherence spikes). The development of higher-order nonlinear spectroscopies operational in the deep UV is motivated by studies of biological systems and elementary organic photochemistries. PMID:25240351

  12. Electronic properties of Sb monolayers on III-V(110) surfaces determined by resonance Raman scattering

    SciTech Connect

    Esser, N.; Koepp, M.; Haier, P.

    1993-07-01

    Resonance Raman scattering (RRS) experiments have been performed to explore the electronic states via the vibrational modes of highly ordered (1 X 1) monolayers of Sb on InP(110) and GaAs(110) prepared by thermal annealing. In accordance to the C{sub s} symmetry of the two-atom unit cell of the monolayers three modes of A{prime} and one of A{double_prime} symmetry are observed by Raman scattering. The scattering intensities show pronounced resonances which are related to electronic transitions between the two-dimensional electronic surface bands. The resonances are found to be characteristic for each vibrational mode. This can be understood in terms of different electronic bands being involved in the scattering process. For Sb on GaAs(110), the resonance of the A{double_prime} mode yields a maximum between 2.2 and 2.3 eV. On InP(110), resonances at 2.55 eV for the 1A{prime}, 2.3-2.6 eV for the 2A{prime}, 1.9 eV for the 1A{double_prime} and{>=}3.0 eV for the 3A{prime} modes occur. For both Sb on GaAs and InP the transition energies observed by RRS coincide with features reported by several other techniques. The resonance behavior of the ideal monolayers can be understood as a fingerprint of the joint density of states at the interface. In contrast, resonance Raman spectra taken after deposition of 1.5 ML Sb without annealing reveal a different resonance behavior. In this case, where the monolayer is not ideally ordered, the resonances are smeared out over an energy range between 2.3 and 2.7 eV revealing the influence of imperfections on the electronic band structure. 41 refs., 3 figs., 1 tab.

  13. Resonance Raman spectra of organic molecules absorbed on inorganic semiconducting surfaces: Contribution from both localized intramolecular excitation and intermolecular charge transfer excitation

    SciTech Connect

    Ye, ChuanXiang; Zhao, Yi E-mail: liangwz@xmu.edu.cn; Liang, WanZhen E-mail: liangwz@xmu.edu.cn

    2015-10-21

    The time-dependent correlation function approach for the calculations of absorption and resonance Raman spectra (RRS) of organic molecules absorbed on semiconductor surfaces [Y. Zhao and W. Z. Liang, J. Chem. Phys. 135, 044108 (2011)] is extended to include the contribution of the intermolecular charge transfer (CT) excitation from the absorbers to the semiconducting nanoparticles. The results demonstrate that the bidirectionally interfacial CT significantly modifies the spectral line shapes. Although the intermolecular CT excitation makes the absorption spectra red shift slightly, it essentially changes the relative intensities of mode-specific RRS and causes the oscillation behavior of surface enhanced Raman spectra with respect to interfacial electronic couplings. Furthermore, the constructive and destructive interferences of RRS from the localized molecular excitation and CT excitation are observed with respect to the electronic coupling and the bottom position of conductor band. The interferences are determined by both excitation pathways and bidirectionally interfacial CT.

  14. Raman scattering enhancement in photon-plasmon resonance mediated metal-dielectric microcavity

    NASA Astrophysics Data System (ADS)

    Guddala, Sriram; Dwivedi, Vindesh K.; Vijaya Prakash, G.; Narayana Rao, D.

    2013-12-01

    Here, we report the photon-plasmon interaction scheme and enhanced field strengths resulted into the amplification of phonon in a novel microcavity. A metal-dielectric microcavity, with unified cavity photonic mode and localized surface plasmon resonances, is visualized by impregnating the gold nanoparticles into the deep see-through nano-sized pores of porous silicon microcavity. The intense optical field strengths resulting from the photon-plasmon interactions are probed by both resonant and non-resonant Raman scattering experiments. Due to photon-plasmon-phonon interaction mechanism, several orders of enhancement in the intensity of scattered Raman Stokes photon (at 500 cm-1) are observed. Our metal nanoparticle-microcavity hybrid system shows the potential to improve the sensing figure of merit as well as the applications of plasmonics for optoelectronics, photovoltaics, and related technologies.

  15. Raman scattering enhancement in photon-plasmon resonance mediated metal-dielectric microcavity

    SciTech Connect

    Guddala, Sriram; Narayana Rao, D. E-mail: dnrsp@uohyd.ernet.in; Dwivedi, Vindesh K.; Vijaya Prakash, G.

    2013-12-14

    Here, we report the photon-plasmon interaction scheme and enhanced field strengths resulted into the amplification of phonon in a novel microcavity. A metal-dielectric microcavity, with unified cavity photonic mode and localized surface plasmon resonances, is visualized by impregnating the gold nanoparticles into the deep see-through nano-sized pores of porous silicon microcavity. The intense optical field strengths resulting from the photon-plasmon interactions are probed by both resonant and non-resonant Raman scattering experiments. Due to photon-plasmon-phonon interaction mechanism, several orders of enhancement in the intensity of scattered Raman Stokes photon (at 500 cm{sup −1}) are observed. Our metal nanoparticle-microcavity hybrid system shows the potential to improve the sensing figure of merit as well as the applications of plasmonics for optoelectronics, photovoltaics, and related technologies.

  16. Vibrational modes and resonant Raman spectra of new B2C nanoribbons

    NASA Astrophysics Data System (ADS)

    Li, Xiaowei; Xu, Yuehua; Dong, Jinming

    2011-07-01

    The vibrational properties and first-order resonant Raman spectra of new B2C nanoribbons (B2C-NRs) have been studied by the density functional theory. It is found that there is a characteristic radial-breathing-like mode (RBLM) for all the calculated B2C-NRs with their frequency varying in a linear proportion to the inverse square root of the B2C-NR's width, whose slope depends closely on the types of B2C-NRs. The RBLM resonant peak's intensities and positions in the first-order resonant Raman spectra of the B2C-NRs are found to depend greatly on the polarizations of the incident and scattered light, and also the types of B2C-NRs.

  17. [High performance liquid chromatographic determination of reducing sugars in fruit juices with laser resonance Raman detection].

    PubMed

    Ding, M; Koizumi, H; Suzuki, Y

    1997-07-01

    A liquid chromatographic method using semi-microcolumn separation combined with laser resonance Raman detection was developed for the determination of monosaccharides in fruit juices. Reducing sugars (galactose, glucose, mannose, arabinose, xylose and ribose) were derivatized with 4-dimethylaminoazobenzene-4'-sulfonyl (DABSYL) hydrazine. The derivatives of the monosaccharides exhibited strong resonance Raman scattering at 1136 cm(-1) when Ar+ laser emission line 488.0 nm was used. A semi-microcolumn Inertsil ODS-2 (250 mm x 1.5 mm i.d.) was used to the separation of the monosaccharide derivatives. The saccharides eluted within 25 min. However the excess DABSYL hydrazine was retained strongly with a retention time of about 60 min. In order to reduce the longer analysis time, the excess DABSYL hydrazine was removed by adding glyoxylic acid and then Na2CO3 aqueous solution when the derivation reaction was finished. As a result, the analysis time was reduced to about a half of its initial run time. The sensitivity of resonance Raman detection greater two orders of magnitude than refractive index (RI) detection. The detection limit of glucose is 10 ng (5.5 pmol). The high selectivity of Raman detection came from the facts that only the interested compounds in a given sample was derived with the Raman labeling reagent and that only the characteristic Raman bands of the derivatives were selectively detected. In this work, in spite of the coexisting large quantities of organic acids in fruit juice, the determined values of glucose agreed well with those obtained by RI detection without any derivatization procedure.

  18. Resonant Absorption of Axisymmetric Modes in Twisted Magnetic Flux Tubes

    NASA Astrophysics Data System (ADS)

    Giagkiozis, I.; Goossens, M.; Verth, G.; Fedun, V.; Van Doorsselaere, T.

    2016-06-01

    It has been shown recently that magnetic twist and axisymmetric MHD modes are ubiquitous in the solar atmosphere, and therefore the study of resonant absorption for these modes has become a pressing issue because it can have important consequences for heating magnetic flux tubes in the solar atmosphere and the observed damping. In this investigation, for the first time, we calculate the damping rate for axisymmetric MHD waves in weakly twisted magnetic flux tubes. Our aim is to investigate the impact of resonant damping of these modes for solar atmospheric conditions. This analytical study is based on an idealized configuration of a straight magnetic flux tube with a weak magnetic twist inside as well as outside the tube. By implementing the conservation laws derived by Sakurai et al. and the analytic solutions for weakly twisted flux tubes obtained recently by Giagkiozis et al. we derive a dispersion relation for resonantly damped axisymmetric modes in the spectrum of the Alfvén continuum. We also obtain an insightful analytical expression for the damping rate in the long wavelength limit. Furthermore, it is shown that both the longitudinal magnetic field and the density, which are allowed to vary continuously in the inhomogeneous layer, have a significant impact on the damping time. Given the conditions in the solar atmosphere, resonantly damped axisymmetric modes are highly likely to be ubiquitous and play an important role in energy dissipation. We also suggest that, given the character of these waves, it is likely that they have already been observed in the guise of Alfvén waves.

  19. Multiband electron resonant Raman scattering in quantum wells in a magnetic field

    NASA Astrophysics Data System (ADS)

    López-Richard, V.; Hai, G.-Q.; Trallero-Giner, C.; Marques, G. E.

    2003-04-01

    A theoretical model has been developed for the electronic resonant Raman scattering processes in direct band zinc blende type semiconductor quantum wells in a magnetic field. In order to take into account the spin-flip transitions, anomalous behavior of the Landau levels and the Landè g factor, an 8×8 Kane-Weiler Hamiltonian model has been considered for the evaluation of the Raman scattering amplitude. Elements concerning the selection rules of resonant inelastic light scattering in quantum well systems are reported. The multiband model predicts conditions for resonant spin-flip Raman processes in several light scattering configurations for crossed and parallel polarization. Special emphasis is given to the effects of the interlevel coupling and mixing within the conduction subband and their relation to spin-flip and inter-Landau level transitions. Symmetry and electronic properties of the level structure in the first conduction subband as well as anomalous Landè factors are discussed in terms of complementary Raman scattering configurations, Fermi energy, and multiband parameters.

  20. Resonance Raman effect in mu-oxo-bis[iron(III) tetraphenylporphyrin].

    PubMed Central

    Adar, F; Srivastava, T S

    1975-01-01

    Resonance Raman spectra of mu-oxo-bis[iron(III) tetraphenylporphyrin] have been observed and compared to Raman spectra of the monomers iron(III) tetraphenylporphyrin chloride and bis(piperidine)iron(II) tetraphenylporphyrin. Selection rules for the Raman effect under conditions of resonance of the incident photons with electronic states are presented for the exact symmetry group (C2) and the pseudo-symmetry group (D4d): emphasis is placed on the physical processes involved in scattering via vibronic states of the dimer. These two models are experimentally distinguishable in the behavior of the depolarization ratios of the dimer vibrational doublets. Experimental data favor the assignment of D4d as the symmetry group relevant to a description of the various states of the dimer. The usefulness of resonance Raman spectra of the mu-oco-dimer of Fe(III) tetraphenylporphyrin has been discussed with respect to several biochemical systems where there is strong evidence of two or more closely interacting chromophores. PMID:1060121

  1. Development of a fiber based Raman probe compatible with interventional magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Ashok, Praveen C.; Praveen, Bavishna B.; Rube, Martin; Cox, Benjamin; Melzer, Andreas; Dholakia, Kishan

    2014-02-01

    Raman spectroscopy has proven to be a powerful tool for discriminating between normal and abnormal tissue types. Fiber based Raman probes have demonstrated its potential for in vivo disease diagnostics. Combining Raman spectroscopy with Magnetic Resonance Imaging (MRI) opens up new avenues for MR guided minimally invasive optical biopsy. Although Raman probes are commercially available, they are not compatible with a MRI environment due to the metallic components which are used to align the micro-optic components such as filters and lenses at the probe head. Additionally they are not mechanically compatible with a typical surgical environment as factors such as sterility and length of the probe are not addressed in those designs. We have developed an MRI compatible fiber Raman probe with a disposable probe head hence maintaining sterility. The probe head was specially designed to avoid any material that would cause MR imaging artefacts. The probe head that goes into patient's body had a diameter <1.5 mm so that it is compatible with biopsy needles and catheters. The probe has been tested in MR environment and has been proven to be capable of obtaining Raman signal while the probe is under real-time MR guidance.

  2. Mie Resonant Absorption and Infrared Emission in InN Related to Metallic Indium Clusters

    NASA Astrophysics Data System (ADS)

    Shubina, T. V.; Ivanov, S. V.; Jmerik, V. N.; Solnyshkov, D. D.; Kop'ev, P. S.; Vasson, A.; Leymarie, J.; Kavokin, A.; Amano, H.; Kamiyama, S.; Iwaya, M.; Akasaki, I.; Lu, H.; Schaff, W. J.; Kasic, A.; Monemar, B.

    2005-06-01

    We demonstrate that resonant optical losses related to metallic In clusters can significantly modify absorption spectra of InN with any optical gap. Thermally detected absorption spectra with a pronounced Mie resonance are successfully simulated using a dielectric function of InN corresponding to the 1.2-1.4 eV optical gap. The resonance is observed in spectra of conventional absorption at low temperatures being smoothed out at room temperature.

  3. Interpretation of the resonance Raman spectra of linear tetrapyrroles based on DFT calculations

    NASA Astrophysics Data System (ADS)

    Kneip, Christa; Hildebrandt, Peter; Németh, Károly; Mark, Franz; Schaffner, Kurt

    1999-10-01

    Raman spectra of linear methine-bridged tetrapyrroles in different conformational and protonation states were calculated on the basis of scaled force fields obtained by density functional theory. Results are reported for protonated phycocyanobilin in the extended ZZZasa configuration, as it is found in C-phycocyanin of cyanobacteria. The calculated spectra are in good agreement with experimental spectra of the protein-bound chromophore in the α-subunit of C-phycocyanin and allow a plausible and consistent assignment of most of the observed resonance Raman bands in the region between 1000 and 1700 cm -1.

  4. Photobleaching of the resonance Raman lines of cytochromes in living yeast cells.

    PubMed

    Okotrub, Konstantin A; Surovtsev, Nikolay V

    2014-12-01

    The photobleaching of the resonance cytochrome Raman lines in living Saccharomyces cerevisiae cells was studied. The photobleaching rate versus the irradiation power was described by square function plus a constant in contrast to the linear dependence of the photoinjury rate. This difference distinguishes the cytochrome photooxidation from other processes of the cell photodamage. The square dependence is associated with the reaction involving two photogenerated intermediates while the constant with the dark redox balance rates. This work demonstrates a potential of Raman spectroscopy to characterize the native cytochrome reaction rates and to study the cell photodamage precursors.

  5. Demonstration of resonant backward Raman amplification in high-density gas-jet plasma

    NASA Astrophysics Data System (ADS)

    Wu, Z. H.; Zhou, K. N.; Zheng, X. M.; Wei, X. F.; Zhu, Q. H.; Su, J. Q.; Xie, N.; Jiao, Z. H.; Peng, H.; Wang, X. D.; Sun, L.; Li, Q.; Huang, Z.; Zuo, Y. L.

    2016-10-01

    Backward Raman amplification was observed in a 0.7 mm-long high-density gas jet plasma. The 800 nm 30 fs seed pulse was amplified by a factor  ∼28, with an output energy of 2.8 mJ. The output spectra showed that the waveband around 800 nm was significantly amplified. The experimental result demonstrated that the resonant Raman amplification can be realized in high-density plasma against strong plasma instability.

  6. Gamma resonance absorption. New approach in human body composition studies.

    PubMed

    Wielopolski, L; Vartsky, D; Pierson, R; Goldberg, M; Heymsfield, S; Yasumura, S; Melnychuk, S T; Sredniawski, J

    2000-05-01

    The main stream of body elemental analysis is based on the delayed, prompt, and inelastic neutron interactions with the main elements found in the human body, and subsequent analysis of the measured delayed or prompt gamma ray spectra. This methodology traditionally was, and still is, applied for whole body analysis and requires relatively high radiation doses. A new method, based on gamma nuclear resonance absorption (GNRA), is being established at Brookhaven National Laboratory as part of its body composition program. The method is element specific with a high tomographic spatial-resolution capability, at a small fraction of the radiation dose used in the current system. The new system, with its components and capabilities, is described below. PMID:10865747

  7. Simultaneous surface plasmon resonance and x-ray absorption spectroscopy

    SciTech Connect

    Serrano, A.; Rodriguez de la Fuente, O.; Collado, V.; Rubio-Zuazo, J.; Castro, G. R.; Monton, C.; Garcia, M. A.

    2012-08-15

    We present an experimental setup for the simultaneous measurement of surface plasmon resonance (SPR) and x-ray absorption spectroscopy (XAS) on metallic thin films at a synchrotron beamline. The system allows measuring in situ and in real time the effect of x-ray irradiation on the SPR curves to explore the interaction of x-rays with matter. It is also possible to record XAS spectra while exciting SPR in order to study changes in the films induced by the excitation of surface plasmons. Combined experiments recording simultaneously SPR and XAS curves while scanning different parameters can be also carried out. The relative variations in the SPR and XAS spectra that can be detected with this setup range from 10{sup -3} to 10{sup -5}, depending on the particular experiment.

  8. Simultaneous surface plasmon resonance and x-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Serrano, A.; Rodríguez de la Fuente, O.; Collado, V.; Rubio-Zuazo, J.; Monton, C.; Castro, G. R.; García, M. A.

    2012-08-01

    We present an experimental setup for the simultaneous measurement of surface plasmon resonance (SPR) and x-ray absorption spectroscopy (XAS) on metallic thin films at a synchrotron beamline. The system allows measuring in situ and in real time the effect of x-ray irradiation on the SPR curves to explore the interaction of x-rays with matter. It is also possible to record XAS spectra while exciting SPR in order to study changes in the films induced by the excitation of surface plasmons. Combined experiments recording simultaneously SPR and XAS curves while scanning different parameters can be also carried out. The relative variations in the SPR and XAS spectra that can be detected with this setup range from 10-3 to 10-5, depending on the particular experiment.

  9. Effects of locally resonant modes on underwater sound absorption in viscoelastic materials.

    PubMed

    Wen, Jihong; Zhao, Honggang; Lv, Linmei; Yuan, Bo; Wang, Gang; Wen, Xisen

    2011-09-01

    Recently, by introducing locally resonant scatterers with spherical shape proposed in phononic crystals into design of underwater sound absorption materials, the low-frequency underwater sound absorption phenomenon induced by the localized resonances is observed. To reveal this absorption mechanism, the effect of the locally resonant mode on underwater sound absorption should be studied. In this paper, the finite element method, which is testified efficiently by comparing the calculation results with those of the layer multiple scattering method, is introduced to investigate the dynamic modes and the corresponding sound absorption of localized resonance. The relationship between the resonance modes described with the displacement contours of one unit cell and the corresponding absorption spectra is discussed in detail, which shows that the localized resonance leads to the absorption peak, and the mode conversion from longitudinal to transverse waves at the second absorption peak is more efficient than that at the first one. Finally, to show the modeling capability of FEM and investigate shape effects of locally resonant scatterers on underwater sound absorption, the absorption properties of viscoelastic materials containing locally resonant scatterers with ellipsoidal shape are discussed.

  10. Nitration of internal tyrosine of cytochrome c probed by resonance Raman scattering.

    PubMed

    Quaroni, L; Smith, W E

    1999-01-01

    Tyrosines can be selectively nitrated in a protein and the resultant chromophore can be used as an in situ probe of the tyrosine environment. Resonance Raman scattering could have specific advantages as a detection method because of the inherent selectivity of the technique and because shifts in the intensity and frequency of the nitro stretch can be detected and related to the form and environment of the nitrotyrosine. To evaluate this possibility the internal residue Tyr67 of cytochrome c was nitrated and resonance Raman scattering was recorded. With 413.1-nm excitation the resonance scattering from the heme protein dominates, but with 457.9-nm excitation intense bands due to nitrostretching vibrations are readily observed. The frequency of the internal Tyr67 indicates an aqueous environment that suggests that on nitration this residue becomes exposed on the protein surface or that water enters the active pocket. pH dependent measurements can be used to follow the protonation of the residue. A pK(a) of approximately 7 also indicates an aqueous environment. This initial study indicates that resonance Raman scattering does have unique advantages as an in situ probe of the local structure of nitrated tyrosine residues.

  11. Magnetic resonance microwave absorption imaging: Feasibility of signal detection

    PubMed Central

    Xie, Bin; Weaver, John B.; Meaney, Paul M.; Paulsen, Keith D.

    2009-01-01

    Purpose: Magnetic resonance (MR) technique was used to detect small displacements induced by localized absorption of pulsed 434 MHz microwave power as a potential method for tumor detection. Methods: Phase contrast subtraction was used to separate the phase change due to motion from thermoelastic expansion from other contributions to phase variation such as the bulk temperature rise of the medium and phase offsets from the MR scanner itself. A simple set of experiments was performed where the motion was constrained to be one dimensional which provided controls on the data acquisition and motion extraction procedures. Specifically, the MR-detected motion signal was isolated by altering the direction of the microwave-induced motion and sampling the response with motion encoding gradients in all three directions when the microwave power was turned on and turned off. Results: Successful signal detection, as evidenced by the recording of a systematic alternating (zigzag) phase pattern, occurred only when the motion encoding was in parallel with either the vertical or horizontal direction of the microwave-induced motion on both 10 and 4 mm spatial scales. Conclusions: These results demonstrate, for the first time, that motion associated with thermoelastic expansion from the absorption of pulsed microwave power can be detected with MR. PMID:19994529

  12. Anomalous absorption, plasmonic resonances, and invisibility of radially anisotropic spheres

    NASA Astrophysics Data System (ADS)

    Wallén, Henrik; Kettunen, Henrik; Sihvola, Ari

    2015-01-01

    This article analyzes the response of a sphere with radially anisotropic permittivity dyadic (RA sphere), in both the electrostatic and full electrodynamic settings. Depending on the values and signs of the permittivity components, the quasistatic polarizability of the RA sphere exhibits several very different interesting properties, including invisibility, field concentration, resonant singularities, and emergent losses. Special attention is given to the anomalous losses that appear in the case of certain hyperbolic anisotropy values. We show that their validity can be justified in a limiting sense by puncturing the sphere at the origin and adding a small imaginary part into the permittivity components. A hyperbolic RA sphere with very small intrinsic losses can thus have significant effective losses making it an effective absorber. With different choices of permittivities, the RA sphere could also perform as a cloak or a sensor. The Mie scattering results by an RA sphere are used to justify the quasistatic calculations. It is shown that in the small parameter limit the absorption efficiency of an RA sphere is nonzero for certain lossless hyperbolic anisotropies. The absorption and scattering efficiencies agree with the quasistatic calculations fairly well for spheres with size parameters up to 1/3.

  13. Feshbach-resonant Raman photoassociation in a Bose-Einstein condensate

    SciTech Connect

    Mackie, Matt; Phou, Pierre; Shinn, Mannix; Boyce, Heather; Katz, Lev

    2011-10-15

    We model the formation of stable heteronuclear molecules via pulsed Raman photoassociation of a two-component Bose-Einstein condensate near a strong Feshbach resonance, for both counterintuitive and intuitive pulse sequencing. Compared to lasers alone, weak Raman photoassociation is enhanced by as much as a factor of ten (five) for a counterintuitive (intuitive) pulse sequence, whereas strong Raman photoassociation is barely enhanced at all--regardless of pulse sequence. Stronger intra-atom, molecule, or atom-molecule collisions lead to an expected decrease in conversion efficiency, but stronger ambient inter-atom collisions lead to an unexpected increase in the efficiency of stable molecule production. Numerical results agree reasonably with an analytical approximation.

  14. Surface-Enhanced Resonance Raman Spectra of Langmuir-Blodgett Films of Tetra-Lauryl Chloroaluminum Phthalocyanine

    NASA Astrophysics Data System (ADS)

    Luo, Tao; Zhang, Weiqing; Gan, Fuxi

    1992-07-01

    The Langmuir-Blodgett (LB) films of tetra-lauryl chloroaluminum phthalocyanine (TLAlClPc) and a 1:1 mixture of TLAlClPc and stearyl alcohol (SA) were prepared. The Raman spectrum of solid TLAlClPc in KBr pellet was investigated. All the Raman lines were assigned. The surface-enhanced resonance Raman spectra of the LB films deposited on the silver island film that were vacuum-deposited on glass slides have been observed.

  15. Polarization rotation under two-photon Raman resonance for magnetometry

    SciTech Connect

    Pradhan, S.; Behera, R.; Das, A. K.

    2012-04-23

    The polarization rotation and coherent population trapping signal arising due to two photon process using linearly polarized light are found to be significantly enhanced for a Zeeman degenerate system. The zero crossing of the dispersive profile is found to be shifting proportional to the applied magnetic field, albeit the absorptive profile position remains invariant for a slightly imbalanced orthogonal circular polarization component. It provides an alternative method for precise measurement of vector magnetic field without requirement of a bias field. The use of polarization rotation signal for magnetic field measurement offers added advantage due to improved signal to noise ratio.

  16. Ultrafast transient absorption of eumelanin suspensions: the role of inverse Raman scattering.

    PubMed

    Aloi, Antonio; Brunetti, Adalberto; Perna, Giuseppe; Lasalvia, Maria; Capozzi, Vito; Tommasi, Raffaele

    2015-10-01

    An ultrafast investigation is carried out on synthetic eumelanin suspended either in water or in DMSO-methanol. Upon photoexcitation by visible femtosecond pulses, the transient absorption (TA) dynamics of the suspensions are probed in a broad visible spectral range, showing clear nonlinearities. The latter arise from pump-probe interactions that induce the inverse Raman scattering (IRS) effect. We show how eumelanin TA dynamics are modified in proximity of the solvent Stokes and anti-Stokes scattering peaks, demonstrating that IRS affects the sign of TA but not the relaxation times. We compare the results obtained in both suspensions, unveiling the role of the surrounding environment. Eventually, the intrinsic response of synthetic eumelanin to ultrafast photoexcitation is evaluated.

  17. Excitons in one-phonon resonant Raman scattering: Fröhlich and interference effects

    NASA Astrophysics Data System (ADS)

    Cantarero, A.; Trallero-Giner, C.; Cardona, M.

    1989-12-01

    A theoretical model of resonant Raman scattering including excitons as intermediate states in the process is compared with recent experimental results in some III-V compound semiconductors where the Raman polarizability was obtained in absolute value for several scattering configurations. In particular, Fröhlich (F) interaction and its interference with the deformation potential (DP) one is analyzed in the E0+Δ0 critical point (CP) of GaAs at three different temperatures. Also the E0 and E0+Δ0 CP of GaP and E0+Δ0 of GaSb are analyzed. We show that the inclusion of impurity-induced forbidden LO-phonon Raman scattering is not necessary when excitonic effects are considered. The experimental data of GaAs corresponding to F interaction can be fitted by assuming a Fröhlich constant cF=0.14 eV Aṥ/2. Lifetime broadenings of 12 meV (10 K), 14 meV (100 K), and 28 meV (300 K) are deduced. The lifetime broadening of GaAs and GaSb at 100 K are taken from two-phonon Raman scattering spectra where the incoming and outgoing resonances are well defined. The general features in the comparison with the experiment is that the measured spectra corresponding to F interaction are well fitted; however, the theoretical interference is stronger than the measured one.

  18. Shifted excitation resonance Raman difference spectroscopy using a microsystem light source at 488 nm

    NASA Astrophysics Data System (ADS)

    Maiwald, M.; Sowoidnich, K.; Schmidt, H.; Sumpf, B.; Erbert, G.; Kronfeldt, H.-D.

    2010-04-01

    Experimental results in shifted excitation resonance Raman difference spectroscopy (SERRDS) at 488 nm will be presented. A novel compact diode laser system was used as excitation light source. The device is based on a distributed feedback (DFB) diode laser as a pump light source and a nonlinear frequency doubling using a periodically poled lithium niobate (PPLN) waveguide crystal. All elements including micro-optics are fixed on a micro-optical bench with a footprint of 25 mm × 5 mm. An easy temperature management of the DFB laser and the crystal was used for wavelength tuning. The second harmonic generation (SHG) provides an additional suppression of the spontaneous emission. Raman spectra of polystyrene demonstrate that no laser bandpass filter is needed for the Raman experiments. Resonance-Raman spectra of the restricted food colorant Tartrazine (FD&C Yellow 5, E 102) in distilled water excited at 488 nm demonstrate the suitability of this light source for SERRDS. A limit of detection (LOD) of 0.4 μmol.l-1 of E102 enables SERRDS at 488 nm for trace detection in e.g. food safety control as an appropriate contactless spectroscopic technique.

  19. Resonant Raman scattering theory for Kitaev models and their Majorana fermion boundary modes

    NASA Astrophysics Data System (ADS)

    Perreault, Brent; Knolle, Johannes; Perkins, Natalia B.; Burnell, F. J.

    2016-09-01

    We study the inelastic light scattering response in two- (2D) and three-dimensional (3D) Kitaev spin-liquid models with Majorana spinon band structures in the symmetry classes BDI and D leading to protected gapless surface modes. We present a detailed calculation of the resonant Raman/Brillouin scattering vertex relevant to iridate and ruthenate compounds whose low-energy physics is believed to be proximate to these spin-liquid phases. In the symmetry class BDI, we find that while the resonant scattering on thin films can detect the gapless boundary modes of spin liquids, the nonresonant processes do not couple to them. For the symmetry class D, however, we find that the coupling between both types of light-scattering processes and the low-energy surface states is strongly suppressed. Additionally, we describe the effect of weak time-reversal symmetry breaking perturbations on the bulk Raman response of these systems.

  20. Fully reflective deep ultraviolet to near infrared spectrometer and entrance optics for resonance Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Schulz, B.; Bäckström, J.; Budelmann, D.; Maeser, R.; Rübhausen, M.; Klein, M. V.; Schoeffel, E.; Mihill, A.; Yoon, S.

    2005-07-01

    We present the design and performance of a new triple-grating deep ultraviolet to near-infrared spectrometer. The system is fully achromatic due to the use of reflective optics. The minimization of image aberrations by using on- and off- axis parabolic mirrors as well as elliptical mirrors yields a strong stray light rejection with high resolution over a wavelength range between 165 and 1000nm. The Raman signal is collected with a reflective entrance objective with a numerical aperture of 0.5, featuring a Cassegrain-type design. Resonance Raman studies on semiconductors and on correlated compounds, such as LaMnO3, highlight the performance of this instrument, and show diverse resonance effects between 1.96 and 5.4eV.

  1. Photogenerated radical intermediates of vitamin K 1: a time-resolved resonance Raman study

    NASA Astrophysics Data System (ADS)

    Balakrishnan, G.; Umapathy, S.

    1999-01-01

    Quinones play a vital role in the process of electron transfer in bacterial photosynthetic reaction centers. It is of interest to investigate the photochemical reactions involving quinones with a view to elucidating the structure-function relationships in the biological processes. Resonance Raman spectra of radical anions and the time-resolved resonance Raman spectra of vitamin K 1 (model compound for Q A in Rhodopseudomonas viridis, a bacterial photosynthetic reception center) are presented. The photochemical intermediates of vitamin K 1, viz. radical anion, ketyl radical and o-quinone methide have been identified. The vibrational assignments of all these intermediates are made on the basis of comparison with our earlier TR3 studies on radical anions of naphthoquinone and menaquinone.

  2. Resonance Raman spectrum and excitation profile of mass-selected zirconium trimers

    NASA Astrophysics Data System (ADS)

    Haouari, Hanae; Wang, Huaiming; Craig, Robert; Lombardi, John R.; Lindsay, D. M.

    1995-12-01

    We present the resonance Raman and Raman excitation profile of mass-selected zirconium trimers in argon matrices. In the Raman spectra, two fundamentals and one overtone are observed. Average Raman shifts, along with standard deviations (in parentheses) are 176.7 (13) cm-1 (ν2), 258.0 (12) cm-1 (ν1), and 516.1 (8) cm-1 (2ν1). The ratio of the frequencies of the two lowest lines (ν1/ν2) is 1.46, which is very close to √2. This is indicative of a symmetrical equilateral geometry (D3h). In such a case we expect two normal frequencies, one for a totally symmetric stretch of symmetry a'1 (ν1) and a doubly degenerate bend of symmetry e'(ν2). The Raman excitation profiles of the ν1(a'1) line shows two broad maxima: one near 491 nm and the other near 614 nm. The ν2 (e') profile shows a broad region of intensity only near 614 nm. With the aid of theory we assign the 614 nm band to be 1A'1-1E' (x,y polarized) while the 491 nm band must be 1A'1-1A″2 (z polarized).

  3. Resonance Raman Spectroscopy of Single-Wall Carbon Nanotubes Separated via Aqueous Two-Phase Extraction

    NASA Astrophysics Data System (ADS)

    Simpson, J. R.; Fagan, J. A.; Hight Walker, A. R.

    2014-03-01

    We report Resonance Raman Spectroscopy (RRS) measurements of single-wall carbon nanotube (SWCNT) samples dispersed in aqueous solutions via surfactant wrapping and separated using aqueous two-phase extraction (ATPE) into chirality-enriched semiconducting and metallic SWCNT species. ATPE provides a rapid, robust, and remarkably tunable separation technique that allows isolation of high-purity, individual SWCNT chiralities via modification of the surfactant environment. We report RRS measurements of individual SWCNT species of various chiral index including, armchair and zigzag metals. Raman provides a powerful technique to quantify the metallic SWCNTs in ATPE fractions separated for metallicity. We measure Raman spectra over a wide range of excitation wavelengths from 457 nm to 850 nm using a series of discrete and continuously tunable laser sources coupled to a triple-grating spectrometer with a liquid-nitrogen-cooled detector. The spectra reveal Raman-active vibrational modes, including the low-frequency radial breathing mode (RBM) and higher-order modes. SWCNT chiral vectors are determined from the Raman spectra, specifically the RBM frequencies and corresponding energy excitation profiles, together with input from theoretical models.

  4. Resonance Raman Spectroscopy of Single-Wall Carbon Nanotubes Separated via Aqueous Two-Phase Extraction

    NASA Astrophysics Data System (ADS)

    Simpson, J. R.; Fagan, J. A.; Hight Walker, A. R.

    2015-03-01

    We report resonance Raman Spectroscopy measurements of single-wall carbon nanotube (SWCNT) samples dispersed in aqueous solutions via surfactant wrapping and separated using aqueous two-phase extraction (ATPE) into chirality-enriched semiconducting and metallic SWCNT species. ATPE provides a rapid, robust, and remarkably tunable separation technique that allows isolation of high-purity, individual SWCNT chiralities via modification of the surfactant environment. We report RRS measurements of individual SWCNT species of various chiral index including, semiconductors, armchair and zigzag metals. Raman provides a powerful technique to quantify the metallic SWCNTs in ATPE fractions separated for metallicity. We measure Raman spectra over a wide range of excitation wavelengths from (457 to 850) nm using a series of discrete and continuously tunable laser sources coupled to a triple-grating spectrometer. The spectra reveal Raman-active vibrational modes, including the low-frequency radial breathing mode (RBM) and higher-order modes. SWCNT chiral vectors are determined from Raman spectra, specifically the RBM frequencies and corresponding energy excitation profiles, together with input from theoretical models.

  5. Absorption, fluorescence, and Raman spectra of mass-selected rhenium dimers in argon matrices

    NASA Astrophysics Data System (ADS)

    Hu, Zhendong; Dong, Jian-Guo; Lombardi, John R.; Lindsay, D. M.; Harbich, W.

    1994-07-01

    We report absorption, laser fluorescence, and Raman spectra for Re2 in an argon matrix prepared by the mass-selected ion deposition technique. The dirhenium absorption spectrum consists of seven band systems (A-G) extending from the near infrared into the ultraviolet region. For the A system (a simple vibrational progression), we find T0=10 817(1) cm-1, ωe=317.1(5) cm-1 and ωexe=1.0(1) cm-1. A Franck-Condon analysis of the A system intensities predicts that this state has a smaller equilibrium internuclear distance than the ground state (Δre=-0.073 Å), in violation of Badger's rule. The B system starts at 13 250 cm-1 and consists of four overlapping (and possibly perturbed) subsystems, whose average vibrational spacing is 270(11) cm-1. The C, D, E, and F systems (vibrational spacings in parentheses) are centered at 22 300 cm-1 (210 cm-1), 24 500 cm-1 (195 cm-1), 29 150 cm-1 (175 cm-1), and 32 900 cm-1 (160 cm-1), respectively. Weak fluorescence spectra, obtained upon laser excitation into the A system, were characterized by vibrational progressions to the dimer ground (X) state and to a low lying (X') state for which T0=357.6(5) cm-1 and ωe=332.3(2) cm-1. Raman and fluorescence progressions to the ground state were observed when the B system was excited. These data give ωe=337.9(49) cm-1 for the dimer ground state in good agreement with measurements from photodetachment spectra [J. Am. Chem. Soc. 108, 178 (1986)]. We propose likely assignments for the low lying electronic states of Re2 and discuss our results in terms of the bonding in the other group VIIB dimers, Mn2 and Tc2.

  6. Molecular spectroscopy of uranium(IV) bis(ketimido) complexes. rare observation of resonance-enhanced raman scattering from organoactinide complexes and evidence for broken-symmetry excited states.

    PubMed

    Da Re, Ryan E; Jantunen, Kimberly C; Golden, Jeffrey T; Kiplinger, Jaqueline L; Morris, David E

    2005-01-19

    Electronic absorption and resonance-enhanced Raman spectra for ketimido (azavinylidene) complexes of tetravalent uranium, (C(5)Me(5))(2)U[-N=C(Ph)(R)](2) (R = Ph, Me, and CH(2)Ph), have been recorded. The absorption spectra exhibit four broad bands between 13 000 and 24 000 cm(-1). The highest-energy band is assigned to the ketimido-localized p( perpendicular)(N)-->pi(N=C) transition based on comparison to the spectra of (C(5)H(5))(2)Zr[-N=CPh(2)](2) and (C(5)Me(5))(2)Th[-N=CPh(2)](2). Upon excitation into any of these four absorption bands, the (C(5)Me(5))(2)U[-N=C(Ph)(R)](2) complexes exhibit resonance enhancement for several Raman bands attributable to vibrations of the ketimido ligands. Raman bands for both the symmetric and nominally asymmetric N=C stretching bands are resonantly enhanced upon excitation into the p( perpendicular)(N)-->pi(N=C) absorption bands, indicating that the excited state is localized on a single ketimido ligand. Raman excitation profiles for (C(5)Me(5))(2)U[-N=CPh(2)](2) confirm that at least one of the lower-energy electronic absorption bands (E(max) approximately 16300 cm(-1)) is a charge-transfer transition between the U(IV) center and the ketimido ligand(s). The observations of both charge-transfer transitions and resonance enhancement of Raman vibrational bands are exceedingly rare for tetravalent actinide complexes and reflect the strong bonding interactions between the uranium 5f/6d orbitals and those on the ketimido ligands. PMID:15643893

  7. Evidence for methoxatin (pyrroloquinolinequinone) as the cofactor in bovine plasma amine oxidase from resonance Raman spectroscopy.

    PubMed Central

    Moog, R S; McGuirl, M A; Cote, C E; Dooley, D M

    1986-01-01

    Resonance Raman spectra of the 2,4-dinitrophenylhydrazine derivatives of bovine plasma amine oxidase [amine:oxygen oxidoreductase (deaminating) (copper-containing), EC 1.4.3.6] have been measured. Detailed comparisons to the spectra of the corresponding derivatives of methoxatin (pyrroloquinolinequinone), pyridoxal, and other aldehydes and diones provide further evidence that covalently bound methoxatin or a closely similar derivative is the organic cofactor in copper-containing amine oxidases. PMID:3464962

  8. A Turn-On Resonance Raman Scattering (BCS/Cu+) Sensor for Quantitative Determination of Proteins.

    PubMed

    Chen, Lei; Xue, Xiangxin; Jiang, Dayu; Yang, Jin; Zhao, Bing; Han, Xiao Xia; Mee Jung, Young

    2016-02-01

    In this study, a new method for the quantitative evaluation of proteins is developed using competitive resonance Raman spectroscopy. A chelation reaction between bathocuproine disulfonate (BCS) and Cu(+) which is reduced by proteins in an alkaline environment, is utilized to create a BCS-Cu(+) complex that has strong resonance Raman activity. As a result, the method presented here enables protein detection over a much wider concentration range than conventional methods. Furthermore, the resonance Raman-based method can provide an improved lower limit of detection (500 pg/mL) compared to that obtained by colorimetric and ultraviolet- (UV-) based methods. Additionally, protein-to-protein variation can be determined using a standard curve created from known concentrations of bovine serum albumin (BSA), and excellent protein recovery is observed. More importantly, the proposed method was employing to the real sample (fetal bovine serum [FBS]). Based on the calibration curve from this method, it is extremely accurate for the determination of total protein concentrations in FBS. Results of this study demonstrate that the proposed method provides a novel and highly sensitive protocol for reagent-based protein assays.

  9. Maximizing the electromagnetic and chemical resonances of surface-enhanced Raman scattering for nucleic acids.

    PubMed

    Freeman, Lindsay M; Pang, Lin; Fainman, Yeshaiahu

    2014-08-26

    Although surface-enhanced Raman spectroscopy (SERS) has previously been performed with nucleic acids, the measured intensities for each nucleic acid have varied significantly depending on the SERS substrate and excitation wavelength. We have demonstrated that the charge-transfer (CT) mechanism, also known as the chemical enhancement of SERS, is responsible for the discrepancies previously reported in literature. The electronic states of cytosine and guanine attached to silver atoms are computationally calculated and experimentally measured to be in the visible range, which leads to a resonance Raman effect at the corresponding maximum wavelengths. The resulting SERS measurements are in good agreement with the simulated values, in which cytosine-silver shows stronger enhancement at 532 nm and guanine-silver shows stronger enhancement at 785 nm. An atomic layer of aluminum oxide is deposited on substrates to prevent charge-transfer, and corresponding measurements show weaker Raman signals caused by the suppression of the chemical resonance. These findings suggest the optimal SERS signal can be achieved by tuning the excitation wavelength to match both the electromagnetic and chemical resonances, paving the way for future single molecule detection of nucleic acids other than adenine.

  10. Observation of structural relaxation during exciton self-trapping via excited-state resonant impulsive stimulated Raman spectroscopy

    SciTech Connect

    Mance, J. G.; Felver, J. J.; Dexheimer, S. L.

    2015-02-28

    We detect the change in vibrational frequency associated with the transition from a delocalized to a localized electronic state using femtosecond vibrational wavepacket techniques. The experiments are carried out in the mixed-valence linear chain material [Pt(en){sub 2}][Pt(en){sub 2}Cl{sub 2}]⋅(ClO{sub 4}){sub 4} (en = ethylenediamine, C{sub 2}H{sub 8}N{sub 2}), a quasi-one-dimensional system with strong electron-phonon coupling. Vibrational spectroscopy of the equilibrated self-trapped exciton is carried out using a multiple pulse excitation technique: an initial pump pulse creates a population of delocalized excitons that self-trap and equilibrate, and a time-delayed second pump pulse tuned to the red-shifted absorption band of the self-trapped exciton impulsively excites vibrational wavepacket oscillations at the characteristic vibrational frequencies of the equilibrated self-trapped exciton state by the resonant impulsive stimulated Raman mechanism, acting on the excited state. The measurements yield oscillations at a frequency of 160 cm{sup −1} corresponding to a Raman-active mode of the equilibrated self-trapped exciton with Pt-Cl stretching character. The 160 cm{sup −1} frequency is shifted from the previously observed wavepacket frequency of 185 cm{sup −1} associated with the initially generated exciton and from the 312 cm{sup −1} Raman-active symmetric stretching mode of the ground electronic state. We relate the frequency shifts to the changes in charge distribution and local structure that create the potential that stabilizes the self-trapped state.

  11. Surface plasmon enhanced interfacial electron transfer and resonance Raman, surface-enhanced resonance Raman studies of cytochrome C mutants

    SciTech Connect

    Zheng, Junwei

    1999-11-08

    Surface plasmon resonance was utilized to enhance the electron transfer at silver/solution interfaces. Photoelectrochemical reductions of nitrite, nitrate, and CO{sub 2} were studied on electrochemically roughened silver electrode surfaces. The dependence of the photocurrent on photon energy, applied potential and concentration of nitrite demonstrates that the photoelectrochemical reduction proceeds via photoemission process followed by the capture of hydrated electrons. The excitation of plasmon resonances in nanosized metal structures resulted in the enhancement of the photoemission process. In the case of photoelectrocatalytic reduction of CO{sub 2}, large photoelectrocatalytic effect for the reduction of CO{sub 2} was observed in the presence of surface adsorbed methylviologen, which functions as a mediator for the photoexcited electron transfer from silver metal to CO{sub 2} in solution. Photoinduced reduction of microperoxidase-11 adsorbed on roughened silver electrode was also observed and attributed to the direct photoejection of free electrons of silver metal. Surface plasmon assisted electron transfer at nanostructured silver particle surfaces was further determined by EPR method.

  12. Active resonance wavelength stabilization for silicon microring resonators with an in-resonator defect-state-absorption-based photodetector.

    PubMed

    Li, Yu; Poon, Andrew W

    2015-01-12

    We propose and demonstrate active resonance wavelength stabilization for silicon microring resonators with an in-resonator defect-state-absorption (DSA)-based photodetector (PD) for optical interconnects. We integrate an electro-optic (EO) tuner and a thermo-optic (TO) tuner on the microring, which are both feedback-controlled following a photocurrent threshold-detection method. Our BF(2)-ion-implanted DSA-based PIN PD exhibits a cavity-enhanced sub-bandgap responsivity at 1550 nm of 3.3 mA/W upon -2 V, which is 550-fold higher than that exhibited by an unimplanted PIN diode integrated on the same microring. Our experiment reveals active stabilization of the resonance wavelength within a tolerance of 0.07 nm upon a step increment of the stage temperature by 7 °C. Upon temperature modulations between 23 °C and 32 °C and between 18 °C and 23 °C, the actively stabilized resonance exhibits a transmission power fluctuation within 2 dB. We observe open eye diagrams at a data transmission rate of up to 30 Gb/s under the temperature modulations. PMID:25835682

  13. Signal generation and Raman-resonant imaging by non-degenerate four-wave mixing under tight focusing conditions.

    PubMed

    Weeks, Tyler; Schie, Iwan W; Wachsmann-Hogiu, Sebastian; Huser, Thomas

    2010-03-01

    The authors demonstrate Raman-resonant imaging based on the simultaneous generation of several nonlinear frequency mixing processes resulting from a 3-color coherent anti-Stokes Raman scattering (CARS) experiment. The interaction of three coincident short-pulsed laser beams simultaneously generates both 2-color (degenerate) CARS and 3-color (non-degenerate) CARS signals, which are collected and characterized spectroscopically - allowing for resonant, doubly-resonant, and non-resonant contrast mechanisms. Images obtained from both 2-color and 3-color CARS signals are compared and found to provide complementary information. The 3-color CARS microscopy scheme provides a versatile multiplexed modality for biological imaging, which may extend the capabilities of label-free non-linear microscopy, e.g. by probing multiple Raman resonances.

  14. Signal generation and Raman-resonant imaging by non-degenerate four-wave mixing under tight focusing conditions.

    PubMed

    Weeks, Tyler; Schie, Iwan W; Wachsmann-Hogiu, Sebastian; Huser, Thomas

    2010-03-01

    The authors demonstrate Raman-resonant imaging based on the simultaneous generation of several nonlinear frequency mixing processes resulting from a 3-color coherent anti-Stokes Raman scattering (CARS) experiment. The interaction of three coincident short-pulsed laser beams simultaneously generates both 2-color (degenerate) CARS and 3-color (non-degenerate) CARS signals, which are collected and characterized spectroscopically - allowing for resonant, doubly-resonant, and non-resonant contrast mechanisms. Images obtained from both 2-color and 3-color CARS signals are compared and found to provide complementary information. The 3-color CARS microscopy scheme provides a versatile multiplexed modality for biological imaging, which may extend the capabilities of label-free non-linear microscopy, e.g. by probing multiple Raman resonances. PMID:19953535

  15. Application of resonance Raman spectroscopy as a nuclear proliferation detection technology

    SciTech Connect

    Sedlacek, A.J. III; Chen, C.L.; Dougherty, D.R.

    1993-03-01

    Resonance Raman spectroscopy (RRS) potentially possesses many of the characteristics of an ideal verification technology. Some of these ideal traits are: very high selectivity and specificity to allow the deconvolution of a mixture of the chemicals of interest, high sensitivity in order to measure a species at trace levels, high reliability and long-term durability, applicability to a wide range of chemicals capability for sensing in a variety of environmental conditions, independence of the physical state of the chemical capability for quantitative analysis, and finally, but no less important capability for full signal development within seconds. In this presentation, the potential of RRS as a detection/identification technology for chemicals pertinent to nuclear materials production and processing will be assessed. A review of the basic principles behind this technique, both theoretical and experimental, will be discussed along with some recent results obtained in this laboratory. Raman scattering is a coherent, inelastic, two-photon scattering process where an exciting photon of energy hv promotes a molecule to a virtual level and the subsequently emitted photon is shifted in frequency in accordance with the rotational-vibrational structure of the irradiated species, therefore providing a unique fingerprint of the molecule. The enhancement of a Raman signal occurs when the excitation frequency is isoenergetic with an allowed electronic transition. Under resonance conditions, scattering cross-sections have been enhanced up to 6 orders of magnitude, thereby allowing the measurement of resonance Raman spectra from concentrations as dilute as 20 ppb for PAHs (with the potential of pptr). In detection/verification programs, this condition translates to increased sensitivity (ppm/ppb) and increased probing distance (m/km).

  16. Application of resonance Raman spectroscopy as a nuclear proliferation detection technology

    SciTech Connect

    Sedlacek, A.J. III; Chen, C.L.; Dougherty, D.R.

    1993-01-01

    Resonance Raman spectroscopy (RRS) potentially possesses many of the characteristics of an ideal verification technology. Some of these ideal traits are: very high selectivity and specificity to allow the deconvolution of a mixture of the chemicals of interest, high sensitivity in order to measure a species at trace levels, high reliability and long-term durability, applicability to a wide range of chemicals capability for sensing in a variety of environmental conditions, independence of the physical state of the chemical capability for quantitative analysis, and finally, but no less important capability for full signal development within seconds. In this presentation, the potential of RRS as a detection/identification technology for chemicals pertinent to nuclear materials production and processing will be assessed. A review of the basic principles behind this technique, both theoretical and experimental, will be discussed along with some recent results obtained in this laboratory. Raman scattering is a coherent, inelastic, two-photon scattering process where an exciting photon of energy hv promotes a molecule to a virtual level and the subsequently emitted photon is shifted in frequency in accordance with the rotational-vibrational structure of the irradiated species, therefore providing a unique fingerprint of the molecule. The enhancement of a Raman signal occurs when the excitation frequency is isoenergetic with an allowed electronic transition. Under resonance conditions, scattering cross-sections have been enhanced up to 6 orders of magnitude, thereby allowing the measurement of resonance Raman spectra from concentrations as dilute as 20 ppb for PAHs (with the potential of pptr). In detection/verification programs, this condition translates to increased sensitivity (ppm/ppb) and increased probing distance (m/km).

  17. Dyes at Ag colloids: The role of energy transfer processes for surface fluorescence and surface enhanced resonance raman scattering

    NASA Astrophysics Data System (ADS)

    Pettinger, B.; Gerolymatou, A.

    1985-06-01

    The comparison of Raman spectra of a pure water solution with those of an aqueous AG colloid reveals only very weak differences. This indicates, not unexpectedly, a low electromagnetic (EM) enhancement factor ( F ≈ 100) for the Raman scattering of water. Just in opposite to these weak effects, the addition of Ag sol to a {10 -10 M }/{l} rhodamine 6G solution causes the replacement of the former solution fluorescence by a similar intense surface enhanced resonance Raman scattering (SERRS). At higher dye concentrations (up to {10 -8 M }/{l}) it is replaced by both, by SERRS and surface fluorescence. The SERRS cross section is generally higher than 10 -20 cm 2 sr -1 molecule -1 photon -1. This indicates that a model based on a combination of weak EM resonances with molecular resonance Raman effects cannot explain a total enhancement by more than 10 orders of magnitude. An energy-transfer model seems to be more suitable.

  18. Analysis of normal and diseased colon mucosa using ultraviolet resonance Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Boustany, Nada N.; Manoharan, Ramasamy; Dasari, Ramachandra R.; Feld, Michael S.

    1996-04-01

    Ultraviolet resonance Raman (UVRR) spectroscopy was used to characterize normal and diseased colon mucosa in vitro. A tunable mode-locked Titanium:Sapphire laser operating at 76 MHz was used to irradiate normal and diseased colon tissue samples with 251 nm light generated from the third harmonic of the fundamental radiation. The Raman scattered light was collected and analyzed using a 1 meter spectrometer fitted with a UV coated, liquid nitrogen cooled CCD detector. The measured spectra show prominent bands that correspond to those of known tissue constituents including nucleic acids, aromatic amino acids and lipids. Using the Raman lineshapes measured from pure solutions of nucleotides, tryptophan, tyrosine, FAD, and from lipid-rich serosal fat, the colon spectra were modeled by a least square fitting algorithm whereby the colon spectra were assumed to be a linear combination of the pure biochemical lineshapes. The relative Raman scattering cross section of each biochemical was determined so that the relative concentration of each compound with respect to the others, could be extracted from a given tissue spectrum.

  19. Resonant Raman detectors for noninvasive assessment of carotenoid antioxidants in human tissue

    NASA Astrophysics Data System (ADS)

    Gellermann, Werner; Sharifzadeh, Mohsen; Ermakova, Maia R.; Ermakov, Igor V.; Bernstein, P. S.

    2003-07-01

    Carotenoid antioxidants form an important part of the human body's anti-oxidant system and are thought to play an important role in disease prevention. Studies have shown an inverse correlation between high dietary intake of carotenoids and risk of certain cancers, heart disease and degenerative diseases. For example, the carotenoids lutein and zeaxanthin, which are present in high concentrations in the human retina, are thought to prevent age-related macular degeneration, the leading cause of blindness in the elderly in the Western world. We have developed various clinical prototype instruments, based on resonance Raman spectroscopy, that are able to measure carotenoid levels directly in the tissue of interest. At present we use the Raman technology to quantify carotenoid levels in the human retina, in skin, and in the oral cavity. We use resonant excitation of the π-conjugated molecules in the visible wavelength range and detect the molecules' carbon-carbon stretch frequencies. The spectral properties of the various carotenoids can be explored to selectively measure in some cases individual carotenoid species linked ot the prevention of cancer, in human skin. The instrumentation involves home-built, compact, high-throughput Raman systems capable of measuring physiological carotenoid concentrations in human subjects rapidly and quantitatively. The instruments have been demonstrated for field use and screening of tissue carotenoid status in large populations. In Epidemiology, the technology holds promise as a novel, noninvasive and objective biomarker of fruit and vegetable uptake.

  20. Stimulated Stokes and Antistokes Raman Scattering in Microspherical Whispering Gallery Mode Resonators.

    PubMed

    Farnesi, Daniele; Berneschi, Simone; Cosi, Franco; Righini, Giancarlo C; Soria, Silvia; Nunzi Conti, Gualtiero

    2016-01-01

    Dielectric microspheres can confine light and sound for a length of time through high quality factor whispering gallery modes (WGM). Glass microspheres can be thought as a store of energy with a huge variety of applications: compact laser sources, highly sensitive biochemical sensors and nonlinear phenomena. A protocol for the fabrication of both the microspheres and coupling system is given. The couplers described here are tapered fibers. Efficient generation of nonlinear phenomena related to third order optical non-linear susceptibility Χ((3)) interactions in triply resonant silica microspheres is presented in this paper. The interactions here reported are: Stimulated Raman Scattering (SRS), and four wave mixing processes comprising Stimulated Anti-stokes Raman Scattering (SARS). A proof of the cavity-enhanced phenomenon is given by the lack of correlation among the pump, signal and idler: a resonant mode has to exist in order to obtain the pair of signal and idler. In the case of hyperparametric oscillations (four wave mixing and stimulated anti-stokes Raman scattering), the modes must fulfill the energy and momentum conservation and, last but not least, have a good spatial overlap. PMID:27078752

  1. Stimulated Stokes and Antistokes Raman Scattering in Microspherical Whispering Gallery Mode Resonators.

    PubMed

    Farnesi, Daniele; Berneschi, Simone; Cosi, Franco; Righini, Giancarlo C; Soria, Silvia; Nunzi Conti, Gualtiero

    2016-04-04

    Dielectric microspheres can confine light and sound for a length of time through high quality factor whispering gallery modes (WGM). Glass microspheres can be thought as a store of energy with a huge variety of applications: compact laser sources, highly sensitive biochemical sensors and nonlinear phenomena. A protocol for the fabrication of both the microspheres and coupling system is given. The couplers described here are tapered fibers. Efficient generation of nonlinear phenomena related to third order optical non-linear susceptibility Χ((3)) interactions in triply resonant silica microspheres is presented in this paper. The interactions here reported are: Stimulated Raman Scattering (SRS), and four wave mixing processes comprising Stimulated Anti-stokes Raman Scattering (SARS). A proof of the cavity-enhanced phenomenon is given by the lack of correlation among the pump, signal and idler: a resonant mode has to exist in order to obtain the pair of signal and idler. In the case of hyperparametric oscillations (four wave mixing and stimulated anti-stokes Raman scattering), the modes must fulfill the energy and momentum conservation and, last but not least, have a good spatial overlap.

  2. Cross-polarized optical absorption of single-walled carbon nanotubes probed by photoluminescence excitation spectroscopy, UV-Vis-IR and polarized Raman Scatterings

    NASA Astrophysics Data System (ADS)

    Maruyama, Shigeo

    2008-03-01

    Because of the depolarization effect, or so-called antenna effect, optical absorption of single-walled carbon nanotubes (SWNTs) is weak when excited by light polarized perpendicular to the nanotube axis. However, in photoluminescence (PL) excitation spectra of isolated SWNTs, PL peaks due to cross-polarized excitation can be clearly identified. By decomposing the cross-polarized component, the optical transition energy of E12 or E21 can be? measured, and the smaller exciton binding energy for perpendicular excitations is concluded [1]. Cross-polarized absorption is dominant in the absorption of a vertically aligned film of SWNTs [2] when excited from the top of the film. In our previous study, a pi-plasmon absorption at 5.25 eV was revealed in contrast to 4.5 eV for parallel excitation [3]. Resonant Raman scattering from such a film is also influenced by the cross-polarized excitation [4]. Even though a Kataura plot for the E33 and E44 range has been proposed by using such a vertically aligned film [5], polarized Raman scattering spectra reveal more complicated features in the system because of the small bundle size, typically 5-8 nanotubes [6]. References: [1] Y. Miyauchi, M. Oba, S. Maruyama, Phys. Rev. B 74 (2006) 205440. [2] Y. Murakami, S. Chiashi, Y. Miyauchi, M. Hu, M. Ogura, T. Okubo, S. Maruyama, Chem. Phys. Lett. 385 (2004) 298. [3] Y. Murakami, E. Einarsson, T. Edamura, S. Maruyama, Phys. Rev. Lett. 94 (2005) 087402. [4] Y. Murakami, S. Chiashi, E. Einarsson, S. Maruyama, Phys. Rev. B 71 (2005) 085403. [5] P. T. Araujo, S. K. Doorn, S. Kilina, S. Tretiak, E. Einarsson, S. Maruyama, H. Chacham, M. A. Pimenta, A. Jorio, Phys. Rev. Lett. 88 (2007) 067401. [6] E. Einarsson, H. Shiozawa, C. Kramberger, M. H. Ruemmeli, A. Gruneis, T. Pichler, S. Maruyama, J. Phys. Chem. C (2007) published on Web.

  3. Raman resonance due to magnetic fluctuations in iron-based superconductors

    NASA Astrophysics Data System (ADS)

    Cai, Jiashen; Hinojosa, Alberto; Chubukov, Andrey

    We perform theoretical analysis of polarization-sensitive Raman spectroscopy on NaFe1-xCoxAs and Ba(Fe1-xCox)2As2, focusing on two features seen in the B1 g symmetry channel (in one Fe unit cell notation): the strong temperature dependence of the static, uniform Raman response in the normal state and the existence of a collective mode in the superconducting state. We show that both features can be explained by the coupling of fermions to pairs of magnetic fluctuations via the Aslamazov-Larkin process. We argue that the singular temperature dependence in the normal state comes from the Aslamazov-Larkin vertex, while the resonance is due to the interaction between two propagating spin fluctuations in an s+- superconductor.

  4. Broadening of absorption band by coupled gap plasmon resonances in a near-infrared metamaterial absorber

    NASA Astrophysics Data System (ADS)

    Cong, Jiawei; Yao, Hongbing; Gong, Daolei; Chen, Mingyang; Tong, Yanqun; Fu, Yonghong; Ren, Naifei

    2016-07-01

    We propose a strategy to broaden the absorption band of the conventional metamaterial absorber by incorporating alternating metal/dielectric films. Up to 7-fold increase in bandwidth and ∼95% average absorption are achieved arising from the coupling of induced multiple gap plasmon resonances. The resonance coupling is analytically demonstrated using the coupled oscillator model, which reveals that both the optimal coupling strength and the resonance wavelength matching are required for the enhancement of absorption bandwidth. The presented multilayer design is easily fabricated and readily implanted to other absorber configurations, offering a practical avenue for applications in photovoltaic cells and thermal emitters.

  5. Double Resonant Raman Scattering and Valley Coherence Generation in Monolayer WSe2

    NASA Astrophysics Data System (ADS)

    Wang, G.; Glazov, M. M.; Robert, C.; Amand, T.; Marie, X.; Urbaszek, B.

    2015-09-01

    The electronic states at the direct band gap of monolayer transition metal dichalcogenides such as WSe2 at the K+ and K- valleys are related by time reversal and may be viewed as pseudospins. The corresponding optical interband transitions are governed by robust excitons. Excitation with linearly polarized light yields the coherent superposition of exciton pseudospin states, referred to as coherent valley states. Here, we uncover how and why valley coherence can be generated efficiently. In double resonant Raman spectroscopy, we show that the optically generated 2 s exciton state differs from the 1 s state by exactly the energy of the combination of several prominent phonons. Superimposed on the exciton photoluminescence (PL), we observe the double resonant Raman signal. This spectrally narrow peak shifts with the excitation laser energy as incoming photons match the 2 s and outgoing photons the 1 s exciton transition. The multiphonon resonance has important consequences: following linearly polarized excitation of the 2 s exciton, a superposition of valley states is efficiently transferred from the 2 s to 1 s state. This explains the high degree of valley coherence measured for the 1 s exciton PL.

  6. Resonance raman spectroscopy and quantum chemical modeling studies of protein-astaxanthin interactions in alpha-crustacyanin (major blue carotenoprotein complex in carapace of lobster, Homarus gammarus).

    PubMed

    Weesie, R J; Merlin, J C; de Groot, H J; Britton, G; Lugtenburg, J; Jansen, F J; Cornard, J P

    1999-01-01

    Resonance Raman spectroscopy and quantum chemical calculations were used to investigate the molecular origin of the large redshift assumed by the electronic absorption spectrum of astaxanthin in alpha-crustacyanin, the major blue carotenoprotein from the carapace of the lobster, Homarus gammarus. Resonance Raman spectra of alpha-crustacyanin reconstituted with specifically 13C-labeled astaxanthins at the positions 15, 15,15', 14,14', 13,13', 12,12', or 20,20' were recorded. This approach enabled us to obtain information about the effect of the ligand-protein interactions on the geometry of the astaxanthin chromophore in the ground electronic state. The magnitude of the downshifts of the C==C stretching modes for each labeled compound indicate that the main perturbation on the central part of the polyene chain is not homogeneous. In addition, changes in the 1250-1400 cm(-1) spectral range indicate that the geometry of the astaxanthin polyene chain is moderately changed upon binding to the protein. Semiempirical quantum chemical modeling studies (Austin method 1) show that the geometry change cannot be solely responsible for the bathochromic shift from 480 to 632 nm of protein-bound astaxanthin. The calculations are consistent with a polarization mechanism that involves the protonation or another interaction with a positive ionic species of comparable magnitude with both ketofunctionalities of the astaxanthin-chromophore and support the changes observed in the resonance Raman and visible absorption spectra. The results are in good agreement with the conclusions that were drawn on the basis of a study of the charge densities in the chromophore in alpha-crustacyanin by solid-state NMR spectroscopy. From the results the dramatic bathochromic shift can be explained not only from a change in the ground electronic state conformation but also from an interaction in the excited electronic state that significantly decreases the energy of the pi-antibonding C==O orbitals and

  7. Error analysis of Raman differential absorption lidar ozone measurements in ice clouds.

    PubMed

    Reichardt, J

    2000-11-20

    A formalism for the error treatment of lidar ozone measurements with the Raman differential absorption lidar technique is presented. In the presence of clouds wavelength-dependent multiple scattering and cloud-particle extinction are the main sources of systematic errors in ozone measurements and necessitate a correction of the measured ozone profiles. Model calculations are performed to describe the influence of cirrus and polar stratospheric clouds on the ozone. It is found that it is sufficient to account for cloud-particle scattering and Rayleigh scattering in and above the cloud; boundary-layer aerosols and the atmospheric column below the cloud can be neglected for the ozone correction. Furthermore, if the extinction coefficient of the cloud is ?0.1 km(-1), the effect in the cloud is proportional to the effective particle extinction and to a particle correction function determined in the limit of negligible molecular scattering. The particle correction function depends on the scattering behavior of the cloud particles, the cloud geometric structure, and the lidar system parameters. Because of the differential extinction of light that has undergone one or more small-angle scattering processes within the cloud, the cloud effect on ozone extends to altitudes above the cloud. The various influencing parameters imply that the particle-related ozone correction has to be calculated for each individual measurement. Examples of ozone measurements in cirrus clouds are discussed.

  8. Resonance absorption of microwaves in He II: Evidence for roton emission

    SciTech Connect

    Rybalko, A.; Rubets, S.; Rudavskii, E.; Tikhiy, V.; Tarapov, S.; Golovashchenko, R.; Derkach, V.

    2007-10-01

    Microwave (MW) absorption in liquid {sup 4}He is investigated in the frequency range of 40-200 GHz at T=1.4-2.5 K. A 'whispering gallery' of waves was generated by a dielectric disk resonator immersed into the liquid. Resonance absorption of MWs was detected at the frequency, which corresponds to the roton minimum of the liquid helium excitation spectrum. The creation of a single roton is possible because of the presence of the resonator wall which absorbs an extra momentum. The resonance frequency is shown to decrease with temperature in an excellent agreement with the temperature dependence of the roton gap obtained previously in the neutron scattering experiment.

  9. Nanoshock wave resonance enhancement on stimulated Raman scattering of H(2)O(2) in liquid water.

    PubMed

    Li, Zhanlong; Li, Hongdong; Fang, Wenhui; Wang, Shenghan; Sun, Chenglin; Men, Zhiwei

    2015-11-01

    This study investigates the stimulated Raman scattering (SRS) of H(2)O(2)-H(2)O mixtures. The laser-induced plasma nanoshock wave is formed by focusing an intense pulsed 532 nm laser beam on the mixtures. An enhancement at the low-frequency 1715  cm(-1) SRS line of the bending mode of H(2)O(2) is observed. The mechanism of enhancement was attributed to nanoshock wave resonance with the bending mode, which would preferentially excite phonon and lower energy molecular vibrations. PMID:26512509

  10. Deep UV resonance Raman spectroscopy of β-sheet amyloid fibrils: a QM/MM simulation.

    PubMed

    Ren, Hao; Jiang, Jun; Mukamel, Shaul

    2011-12-01

    We present a combined quantum mechanics and molecular mechanics study of the deep ultraviolet ππ* resonance Raman spectra of β-sheet amyloid fibrils Aβ(34-42) and Aβ(1-40). Effects of conformational fluctuations are described using a Ramachandran angle map, thus avoiding repeated ab initio calculations. Experimentally observed effects of hydrogen-deuterium exchange are reproduced. We propose that the AmIII band redshift upon deuteration is caused by the loss of coupling between C(α)-H bending and N-D bending modes, rather than by peptide bond hydration.

  11. Nanoshock wave resonance enhancement on stimulated Raman scattering of H(2)O(2) in liquid water.

    PubMed

    Li, Zhanlong; Li, Hongdong; Fang, Wenhui; Wang, Shenghan; Sun, Chenglin; Men, Zhiwei

    2015-11-01

    This study investigates the stimulated Raman scattering (SRS) of H(2)O(2)-H(2)O mixtures. The laser-induced plasma nanoshock wave is formed by focusing an intense pulsed 532 nm laser beam on the mixtures. An enhancement at the low-frequency 1715  cm(-1) SRS line of the bending mode of H(2)O(2) is observed. The mechanism of enhancement was attributed to nanoshock wave resonance with the bending mode, which would preferentially excite phonon and lower energy molecular vibrations.

  12. Al-doped MgB2 materials studied using electron paramagnetic resonance and Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Bateni, Ali; Erdem, Emre; Repp, Sergej; Weber, Stefan; Somer, Mehmet

    2016-05-01

    Undoped and aluminum (Al) doped magnesium diboride (MgB2) samples were synthesized using a high-temperature solid-state synthesis method. The microscopic defect structures of Al-doped MgB2 samples were systematically investigated using X-ray powder diffraction, Raman spectroscopy, and electron paramagnetic resonance. It was found that Mg-vacancies are responsible for defect-induced peculiarities in MgB2. Above a certain level of Al doping, enhanced conductive properties of MgB2 disappear due to filling of vacancies or trapping of Al in Mg-related vacancy sites.

  13. Limiting effects on laser compression by resonant backward Raman scattering in modern experiments

    SciTech Connect

    Yampolsky, Nikolai A.; Fisch, Nathaniel J.

    2011-05-15

    Through resonant backward Raman scattering, the plasma wave mediates the energy transfer between long pump and short seed laser pulses. These mediations can result in pulse compression at extraordinarily high powers. However, both the overall efficiency of the energy transfer and the duration of the amplified pulse depend upon the persistence of the plasma wave excitation. At least with respect to the recent state-of-the-art experiments, it is possible to deduce that at present the experimentally realized efficiency of the amplifier is likely constrained mainly by two effects, namely, the pump chirp and the plasma wave wavebreaking.

  14. Monitoring LED-induced carotenoid increase in grapes by Transmission Resonance Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Gonzálvez, Alicia G.; Martínez, Nerea L.; Telle, Helmut H.; Ureña, Ángel González

    2013-02-01

    Transmission Resonance Raman (TRR) spectroscopy combines increased signal-to-noise ratio with enhanced analytical sensibility. TRR was applied to directly monitor, without any sample preparation, the enhancement of β-carotene content in table grapes when they are irradiated by low power UV-LEDs. It was shown that, with respect to control samples, the carotenoid content in the grapes increased about five-fold, using UV-LED irradiation doses being two orders of magnitude lower than the maximum limit allowed by United States Food and Drug Administration. These promising results may pave the way for the development of easy, non-invasive techniques to improve food quality.

  15. A multiple-resonator approach for broadband light absorption in a single layer of nanostructured graphene.

    PubMed

    Yi, Soongyu; Zhou, Ming; Shi, Xi; Gan, Qiaoqiang; Zi, Jian; Yu, Zongfu

    2015-04-20

    The interaction between two-dimensional (2D) materials and light is rather weak due to their ultrathin thickness. In order for these emerging 2D materials to achieve performances that are comparable to those of conventional optoelectronic devices, the light-material interaction must be significantly enhanced. An effective way to enhance the interaction is to use optical resonances. Efficient light absorption has been demonstrated in a single layer of graphene based on a variety of resonators. However, the bandwidth of the absorption enhancement is always narrow, which limits its application for optoelectronic devices. In order to broaden the enhancement of light-material interaction, here we propose a multiple-resonator approach based on nanostructured graphene. These nanostructures having different geometry support resonances at different frequencies. Owing to their deep subwavelength sizes, graphene resonators can be closely packed in space, resulting in a high optical density of states, which enables the broadband light absorption.

  16. Resonance Raman spectroscopy for human cancer detection of key molecules with clinical diagnosis

    NASA Astrophysics Data System (ADS)

    Zhou, Yan; Liu, Cheng-hui; Li, Jiyou; Zhou, Lixin; He, Jingsheng; Sun, Yi; Pu, Yang; Zhu, Ke; Liu, Yulong; Li, Qingbo; Cheng, Gangge; Alfano, Robert R.

    2013-03-01

    Resonance Raman (RR) has the potential to reveal the differences between cancerous and normal breast and brain tissues in vitro. This differences caused by the changes of specific biomolecules in the tissues were displayed in resonance enhanced of vibrational fingerprints. It observed that the changes of reduced collagen contents and the number of methyl may show the sub-methylation of DNA in cancer cells. Statistical theoretical models of Bayesian, principal component analysis (PCA) and support vector machine (SVM) were used for distinguishing cancer from normal based on the RR spectral data of breast and meninges tissues yielding the diagnostic sensitivity of 80% and 90.9%, and specificity of 100% and 100%, respectively. The results demonstrated that the RR spectroscopic technique could be applied as clinical optical pathology tool with a high accuracy and reliability.

  17. Visualizing resonances in the complex plane with vibrational phase contrast coherent anti-Stokes Raman scattering.

    PubMed

    Jurna, Martin; Garbacik, Erik T; Korterik, Jeroen P; Herek, Jennifer L; Otto, Cees; Offerhaus, Herman L

    2010-09-15

    In coherent anti-Stokes Raman scattering (CARS), the emitted signal carries both amplitude and phase information of the molecules in the focal volume. Most CARS experiments ignore the phase component, but its detection allows for two advantages over intensity-only CARS. First, the pure resonant response can be determined, and the nonresonant background rejected, by extracting the imaginary component of the complex response, enhancing the sensitivity of CARS measurements. Second, selectivity is increased via determination of the phase and amplitude, allowing separation of individual molecular components of a sample even when their vibrational bands overlap. Here, using vibrational phase contrast CARS (VPC-CARS), we demonstrate enhanced sensitivity in quantitative measurements of ethanol/methanol mixtures and increased selectivity in a heterogeneous mixture of plastics and water. This powerful technique opens a wide range of possibilities for studies of complicated systems where overlapping resonances limit standard methodologies. PMID:20731373

  18. Atypical Exciton-Phonon Interactions in WS2 and WSe2 Monolayers Revealed by Resonance Raman Spectroscopy.

    PubMed

    Del Corro, E; Botello-Méndez, A; Gillet, Y; Elias, A L; Terrones, H; Feng, S; Fantini, C; Rhodes, Daniel; Pradhan, N; Balicas, L; Gonze, X; Charlier, J-C; Terrones, M; Pimenta, M A

    2016-04-13

    Resonant Raman spectroscopy is a powerful tool for providing information about excitons and exciton-phonon coupling in two-dimensional materials. We present here resonant Raman experiments of single-layered WS2 and WSe2 using more than 25 laser lines. The Raman excitation profiles of both materials show unexpected differences. All Raman features of WS2 monolayers are enhanced by the first-optical excitations (with an asymmetric response for the spin-orbit related XA and XB excitons), whereas Raman bands of WSe2 are not enhanced at XA/B energies. Such an intriguing phenomenon is addressed by DFT calculations and by solving the Bethe-Salpeter equation. These two materials are very similar. They prefer the same crystal arrangement, and their electronic structure is akin, with comparable spin-orbit coupling. However, we reveal that WS2 and WSe2 exhibit quite different exciton-phonon interactions. In this sense, we demonstrate that the interaction between XC and XA excitons with phonons explains the different Raman responses of WS2 and WSe2, and the absence of Raman enhancement for the WSe2 modes at XA/B energies. These results reveal unusual exciton-phonon interactions and open new avenues for understanding the two-dimensional materials physics, where weak interactions play a key role coupling different degrees of freedom (spin, optic, and electronic). PMID:26998817

  19. The study of near-resonance Raman scattering of AlInN/AlN/GaN heterostructure

    NASA Astrophysics Data System (ADS)

    Liu, Yanli; Yang, Lianhong; Chen, Dunjun; Zhang, Li; Lu, Hai; Zhang, Rong; Zheng, Youdou

    2015-07-01

    The visible and ultraviolet (UV) Raman scattering of an AlInN/AlN/GaN heterostructure were measured under z (x, _) z bar configuration at room temperature. Compared with the visible Raman spectrum, three new peaks at 609, 700, and 840 cm-1 occurred in the UV Raman spectrum and were verified to result from the resonance enhanced Raman effect. The near-resonance Raman scattering is stimulated by the electron transition process between the valence band and subband of triangular quantum well located at the interface of AlN/GaN because this transition process has a near equal energy with the 325 nm excitation light. According to the calculated dispersion relations of interface phonon modes in the AlInN/AlN/GaN heterostructure and the 2DEG-related resonance enhanced effect, these new Raman peaks were mainly attributed to the interface phonon modes and disorder-activated mode. The contributions from the bulk phonon modes of AlN and AlInN layers play a very minor role.

  20. Studies on adsorption of mono- and multi-chromophoric hemicyanine dyes on silver nanoparticles by surface-enhanced resonance raman and theoretical calculations

    NASA Astrophysics Data System (ADS)

    Biswas, Nandita; Thomas, Susy; Kapoor, Sudhir; Mishra, Amaresh; Wategaonkar, Sanjay; Mukherjee, Tulsi

    2008-11-01

    Structural and vibrational properties of mono- and multichromophoric hemicyanine (HC) dyes in solution and adsorbed on silver-coated films have been investigated using optical absorption and resonance Raman scattering techniques, with interpretations aided by theoretical calculations. This is the first report on the Raman spectroscopic studies of multichromophoric HC derivatives. The structure of the monomer, N-propyl-4-(p-N,N-dimethylamino styryl)pyridinium bromide (HC3), and its charged and neutral silver complexes (HC3-Ag) in the ground electronic (S0) state were optimized using density functional calculations with the B3LYP method using the 6-31G* and LANL2DZ basis sets. The ground state structure of N-hexyl-4-(p-N,N-dimethylamino styryl)pyridinium bromide (HC6) and multichromophoric HC dyes were computed using the HF /6-31G* method. The negligible shift or broadening observed in the electronic absorption and resonance Raman spectra in solution with increasing size of the HC chromophore suggests that the excitations are localized within individual monomer units in bis and tetra chromophores. However, in the tris chromophore, considerable redshift and broadening were observed, indicating a significant electronic interaction between the nonbonded electrons of the N atom and the aromatic π-system that is supported by the calculated excitation energies using the time-dependent density functional theory method. The effect of HC dye concentration on the electronic absorption spectra of the silver-coated film showed significant broadening, which was attributed to the formation of H- and J-aggregates in addition to the formation of a metal-molecule complex. A considerable redshift along various vibrations observed in the surface-enhanced resonance Raman scattering (SERRS) spectra of the HC derivatives indicates that adsorption on the silver surface leads to a considerable interaction of the electron rich moiety of HC derivatives with the silver surface. The

  1. Magnetic field enriched surface enhanced resonance Raman spectroscopy for early malaria diagnosis.

    PubMed

    Yuen, Clement; Liu, Quan

    2012-01-01

    Hemozoin is a by-product of malaria infection in erythrocytes, which has been explored as a biomarker for early malaria diagnosis. We report magnetic field-enriched surface-enhanced resonance Raman spectroscopy (SERRS) of β-hematin crystals, which are the equivalent of hemozoin biocrystals in spectroscopic features, by using magnetic nanoparticles with iron oxide core and silver shell (Fe(3)O(4)@Ag). The external magnetic field enriches β-hematin crystals and enhances the binding between β-hematin crystals and magnetic nanoparticles, which provides further improvement in SERRS signals. The magnetic field-enriched SERRS signal of β-hematin crystals shows approximately five orders of magnitude enhancement in the resonance Raman signal, in comparison to about three orders of magnitude improvement in the SERRS signal without the influence of magnetic field. The improvement has led to a β-hematin detection limit at a concentration of 5 nM (roughly equivalent to 30 parasites/μl at the early stages of malaria infection), which demonstrates the potential of magnetic field-enriched SERRS technique in early malaria diagnosis.

  2. Magnetic field enriched surface enhanced resonance Raman spectroscopy for early malaria diagnosis

    NASA Astrophysics Data System (ADS)

    Yuen, Clement; Liu, Quan

    2012-01-01

    Hemozoin is a by-product of malaria infection in erythrocytes, which has been explored as a biomarker for early malaria diagnosis. We report magnetic field-enriched surface-enhanced resonance Raman spectroscopy (SERRS) of β--hematin crystals, which are the equivalent of hemozoin biocrystals in spectroscopic features, by using magnetic nanoparticles with iron oxide core and silver shell (Fe3O4@Ag). The external magnetic field enriches β--hematin crystals and enhances the binding between β--hematin crystals and magnetic nanoparticles, which provides further improvement in SERRS signals. The magnetic field-enriched SERRS signal of β--hematin crystals shows approximately five orders of magnitude enhancement in the resonance Raman signal, in comparison to about three orders of magnitude improvement in the SERRS signal without the influence of magnetic field. The improvement has led to a β--hematin detection limit at a concentration of 5 nM (roughly equivalent to 30 parasites/μl at the early stages of malaria infection), which demonstrates the potential of magnetic field-enriched SERRS technique in early malaria diagnosis.

  3. Resonant behaviour of MHD waves on magnetic flux tubes. I - Connection formulae at the resonant surfaces. II - Absorption of sound waves by sunspots

    NASA Technical Reports Server (NTRS)

    Sakurai, Takashi; Goossens, Marcel; Hollweg, Joseph V.

    1991-01-01

    The present method of addressing the resonance problems that emerge in such MHD phenomena as the resonant absorption of waves at the Alfven resonance point avoids solving the fourth-order differential equation of dissipative MHD by recourse to connection formulae across the dissipation layer. In the second part of this investigation, the absorption of solar 5-min oscillations by sunspots is interpreted as the resonant absorption of sounds by a magnetic cylinder. The absorption coefficient is interpreted (1) analytically, under certain simplifying assumptions, and numerically, under more general conditions. The observed absorption coefficient magnitude is explained over suitable parameter ranges.

  4. Three-photon-absorption resonance for all-optical atomic clocks

    SciTech Connect

    Zibrov, Sergei; Novikova, Irina; Phillips, David F.; Taichenachev, Aleksei V.; Yudin, Valeriy I.; Walsworth, Ronald L.; Zibrov, Alexander S.

    2005-07-15

    We report an experimental study of an all-optical three-photon-absorption resonance (known as an 'N resonance') and discuss its potential application as an alternative to atomic clocks based on coherent population trapping. We present measurements of the N-resonance contrast, width and light shift for the D{sub 1} line of {sup 87}Rb with varying buffer gases, and find good agreement with an analytical model of this resonance. The results suggest that N resonances are promising for atomic clock applications.

  5. Radiolytic oxidation of 1,2,4-benzenetriol. An application of time-resolved resonance Raman spectroscopy to kinetic studies of reaction intermediates

    SciTech Connect

    Qin, L.; Tripathi, G.N.R.; Schuler, R.H.

    1987-03-26

    In acidic solution, 1,2,4-benzenetriol is rapidly oxidized by OH or N/sub 3/ to form a mixture of neutral 2,4- and 3,4-dihydroxyphenoxyl radicals. At higher pH these radicals deprotonate (pK/sub a/(1) = 4.75) to form the 2-hydroxy-p-benzosemiquinone radical anion which exhibits a prominent resonance Raman band at 1625 cm/sup -1/ attributable to the Wilson 8a ring stretching mode. In basic solutions this radical subsequently reacts with OH/sup -/ to form the radical dianion (pK/sub a/(2) = 8.85) in which the 8a band is shifted to an appreciably lower frequency (1587 cm/sup -1/). While the absorption spectra of these latter radicals are very similar and do not allow ready examination of their interconversion by absorption spectrophotometry, the difference between these 8a frequencies is sufficiently great that the Raman method can be used to examine the acid-base equilibrium between the two forms of the radical and to follow the deprotonation kinetics. It is shown that even at high pH the radical monoanion is initially formed on oxidation by N/sub 3/ and that deprotonation subsequently occurs by its reaction with base with a rate constant of (9.6 +/- 1.5) x 10/sup 9/ M/sup -1/ d/sup -1/. These studies illustrate very well the application of time-resolved resonance Raman spectroscopy as a complement to kinetic spectrophotometry in sorting out the details of secondary processes in pulse radiolysis studies.

  6. Coherent perfect absorption induced by the nonlinearity of a Helmholtz resonator.

    PubMed

    Achilleos, V; Richoux, O; Theocharis, G

    2016-07-01

    In this work, coherent perfect absorption of sound waves induced by the nonlinear response of a Helmholtz Resonator side loaded to a waveguide, is reported. It is shown that this two-port system can perfectly absorb two high amplitude symmetric incident waves under a certain condition. For the one-sided incidence configuration, this condition leads to an absorption equal to 0.5. Experiments verify these results and are in agreement with an analytical nonlinear impedance model for the resonator. The nonlinear control of perfect absorption opens new possibilities in the design of high amplitude sound attenuators for aero-engine applications. PMID:27475220

  7. Perfect and broadband acoustic absorption by critically coupled sub-wavelength resonators

    PubMed Central

    Romero-García, V.; Theocharis, G.; Richoux, O.; Merkel, A.; Tournat, V.; Pagneux, V.

    2016-01-01

    Perfect absorption is an interdisciplinary topic with a large number of applications, the challenge of which consists of broadening its inherently narrow frequency-band performance. We experimentally and analytically report perfect and broadband absorption for audible sound, by the mechanism of critical coupling, with a sub-wavelength multi-resonant scatterer (SMRS) made of a plate-resonator/closed waveguide structure. In order to introduce the role of the key parameters, we first present the case of a single resonant scatterer (SRS) made of a Helmholtz resonator/closed waveguide structure. In both cases the controlled balance between the energy leakage of the several resonances and the inherent losses of the system leads to perfect absorption peaks. In the case of the SMRS we show that systems with large inherent losses can be critically coupled using resonances with large leakage. In particular, we show that in the SMRS system, with a thickness of λ/12 and diameter of λ/7, several perfect absorption peaks overlap to produce absorption bigger than 93% for frequencies that extend over a factor of 2 in audible frequencies. The reported concepts and methodology provide guidelines for the design of broadband perfect absorbers which could contribute to solve the major issue of noise reduction. PMID:26781863

  8. Perfect and broadband acoustic absorption by critically coupled sub-wavelength resonators.

    PubMed

    Romero-García, V; Theocharis, G; Richoux, O; Merkel, A; Tournat, V; Pagneux, V

    2016-01-01

    Perfect absorption is an interdisciplinary topic with a large number of applications, the challenge of which consists of broadening its inherently narrow frequency-band performance. We experimentally and analytically report perfect and broadband absorption for audible sound, by the mechanism of critical coupling, with a sub-wavelength multi-resonant scatterer (SMRS) made of a plate-resonator/closed waveguide structure. In order to introduce the role of the key parameters, we first present the case of a single resonant scatterer (SRS) made of a Helmholtz resonator/closed waveguide structure. In both cases the controlled balance between the energy leakage of the several resonances and the inherent losses of the system leads to perfect absorption peaks. In the case of the SMRS we show that systems with large inherent losses can be critically coupled using resonances with large leakage. In particular, we show that in the SMRS system, with a thickness of λ/12 and diameter of λ/7, several perfect absorption peaks overlap to produce absorption bigger than 93% for frequencies that extend over a factor of 2 in audible frequencies. The reported concepts and methodology provide guidelines for the design of broadband perfect absorbers which could contribute to solve the major issue of noise reduction. PMID:26781863

  9. Perfect and broadband acoustic absorption by critically coupled sub-wavelength resonators

    NASA Astrophysics Data System (ADS)

    Romero-García, V.; Theocharis, G.; Richoux, O.; Merkel, A.; Tournat, V.; Pagneux, V.

    2016-01-01

    Perfect absorption is an interdisciplinary topic with a large number of applications, the challenge of which consists of broadening its inherently narrow frequency-band performance. We experimentally and analytically report perfect and broadband absorption for audible sound, by the mechanism of critical coupling, with a sub-wavelength multi-resonant scatterer (SMRS) made of a plate-resonator/closed waveguide structure. In order to introduce the role of the key parameters, we first present the case of a single resonant scatterer (SRS) made of a Helmholtz resonator/closed waveguide structure. In both cases the controlled balance between the energy leakage of the several resonances and the inherent losses of the system leads to perfect absorption peaks. In the case of the SMRS we show that systems with large inherent losses can be critically coupled using resonances with large leakage. In particular, we show that in the SMRS system, with a thickness of λ/12 and diameter of λ/7, several perfect absorption peaks overlap to produce absorption bigger than 93% for frequencies that extend over a factor of 2 in audible frequencies. The reported concepts and methodology provide guidelines for the design of broadband perfect absorbers which could contribute to solve the major issue of noise reduction.

  10. Quantum-mechanical calculation of the intensity distribution in resonance Raman scattering spectra of isolated skatole and skatole-water complex

    NASA Astrophysics Data System (ADS)

    Burova, T. G.; Nurlygayanova, M. H.; Ten, G. N.; Yakovleva, A. A.

    2013-03-01

    The relative intensities of lines in resonance Raman scattering spectra of isolated skatole and skatole-water complex have been calculated quantum mechanically. The influence of the intermolecular interaction on these spectra has been considered. Particular features of the intensity distribution in the resonance Raman scattering spectra of indole and skatole have been compared.

  11. [Study of biological molecules in water by using the resonance raman spectra in liquid-core optical fiber].

    PubMed

    Jia, Li-Hua; Wang, Yi-Ding; Sun, Cheng-Lin; Li, Zhan-Long; Li, Zuo-Wei; Wang, Li-Jun

    2009-10-01

    Raman spectrum is an important and effective method for the study of biological molecules in water. Measuring the Raman spectra for biological molecules in water, however, is very difficult because of the small Raman scattering cross section and the high electronic excitation energy of water molecules. In the present paper, the authors applied both technologies of liquid-core optical fiber and the resonance Raman spectra, then the intensity of Raman spectra was enhanced to a great extent. In this experiment, we chose the laser wavelength 514.5 of Ar+ ion laser as excitation laser, because we could obtain the maximal intensity of resonance Raman spectra at this wavelength. The experiment results show that, for the trace inspecting study of beta-carotene biological molecules in water, the concentration in the range of 10(-7)-10(-9) mol x L(-1) can be detected by quartz liquid-core optical fiber and the concentration in the range of 10(-9)-10(-10) mol x L(-1) by Teflon liquid-core optical fiber. The detecting utmost will be further reduced if improving the quality of optical fiber. PMID:20038038

  12. Control of acoustic absorption in one-dimensional scattering by resonant scatterers

    NASA Astrophysics Data System (ADS)

    Merkel, A.; Theocharis, G.; Richoux, O.; Romero-García, V.; Pagneux, V.

    2015-12-01

    We experimentally report perfect acoustic absorption through the interplay of the inherent losses and transparent modes with high Q factor. These modes are generated in a two-port, one-dimensional waveguide, which is side-loaded by isolated resonators of moderate Q factor. In symmetric structures, we show that in the presence of small inherent losses, these modes lead to coherent perfect absorption associated with one-sided absorption slightly larger than 0.5. In asymmetric structures, near perfect one-sided absorption is possible (96%) with a deep sub-wavelength sample ( λ / 28 , where λ is the wavelength of the sound wave in the air). The control of strong absorption by the proper tuning of the radiation leakage of few resonators with weak losses will open possibilities in various wave-control devices.

  13. Probing the pigment binding sites in LHCII with resonance Raman spectroscopy: The effect of mutations at S123.

    PubMed

    Kish, Elizabeth; Wang, Ke; Llansola-Portoles, Manuel J; Ilioaia, Cristian; Pascal, Andrew A; Robert, Bruno; Yang, Chunhong

    2016-09-01

    Resonance Raman spectroscopy was used to evaluate the structure of light-harvesting chlorophyll (Chl) a/b complexes of photosystem II (LHCII), reconstituted from wild-type (WT) and mutant apoproteins over-expressed in Escherichia coli. The point mutations involved residue S123, exchanged for either P (S123P) or G (S123G). In all reconstituted proteins, lutein 2 displayed a distorted conformation, as it does in purified LHCII trimers. Reconstituted WT and S123G also exhibited a conformation of bound neoxanthin (Nx) molecules identical to the native protein, while the S123P mutation was found to induce a change in Nx conformation. This structural change of neoxanthin is accompanied by a blue shift of the absorption of this carotenoid molecule. The interactions assumed by (and thus the structure of the binding sites of) the bound Chls b were found identical in all the reconstituted proteins, and only marginally perturbed as compared to purified LHCII. The interactions assumed by bound Chls a were also identical in purified LHCII and the reconstituted WT. However, the keto carbonyl group of one Chl a, originally free-from-interactions in WT LHCII, becomes involved in a strong H-bond with its environment in LHCII reconstituted from the S123P apoprotein. As the absorption in the Qy region of this protein is identical to that of the LHCII reconstituted from the WT apoprotein, we conclude that the interaction state of the keto carbonyl of Chl a does not play a significant role in tuning the binding site energy of these molecules.

  14. Exploring the Potential of Stable Isotope (Resonance) Raman Microspectroscopy and Surface-Enhanced Raman Scattering for the Analysis of Microorganisms at Single Cell Level.

    PubMed

    Kubryk, Patrick; Kölschbach, Janina S; Marozava, Sviatlana; Lueders, Tillmann; Meckenstock, Rainer U; Niessner, Reinhard; Ivleva, Natalia P

    2015-07-01

    Raman microspectroscopy is a prime tool to characterize the molecular and isotopic composition of microbial cells. However, low sensitivity and long acquisition times limit a broad applicability of the method in environmental analysis. In this study, we explore the potential, the applicability, and the limitations of stable isotope Raman microspectroscopy (SIRM), resonance SIRM, and SIRM in combination with surface-enhanced Raman scattering (SERS) for the characterization of single bacterial cells. The latter two techniques have the potential to significantly increase sensitivity and decrease measurement times in SIRM, but to date, there are no (SERS-SIRM) or only a limited number (resonance SIRM) of studies in environmental microbiology. The analyzed microorganisms were grown with substrates fully labeled with the stable isotopes (13)C or (2)H and compounds with natural abundance of atomic isotopes ((12)C 98.89% or (1)H 99.9844%, designated as (12)C or (1)H, respectively). Raman bands of bacterial cell compounds in stable isotope-labeled microorganisms exhibited a characteristic red-shift in the spectra. In particular, the sharp phenylalanine band was found to be an applicable marker band for SIRM analysis of the Deltaproteobacterium strain N47 growing anaerobically on (13)C-naphthalene. The study of G. metallireducens grown with (13)C- and (2)H-acetate showed that the information on the chromophore cytochrome c obtained by resonance SIRM at 532 nm excitation wavelength can be successfully complemented by whole-organism fingerprints of bacteria cells achieved by regular SIRM after photobleaching. Furthermore, we present here for the first time the reproducible SERS analysis of microbial cells labeled with stable isotopes. Escherichia coli strain DSM 1116 cultivated with (12)C- or (13)C-glucose was used as a model organism. Silver nanoparticles synthesized in situ were applied as SERS media. We observed a reproducible red-shift of an adenine-related marker band

  15. Interaction between indium tin oxide nanoparticles and cytochrome c: A surface-enhanced Raman scattering and absorption spectroscopic study

    SciTech Connect

    Yang, Yimin E-mail: tqiu@seu.edu.cn; Du, Deyang; Fan, Jiyang; Qiu, Teng E-mail: tqiu@seu.edu.cn; Kong, Fan

    2015-06-28

    Indium-tin-oxide (ITO) nanoparticles were annealed in vacuum or reducing atmosphere to obtain different surface structures and investigate their influence on the adsorptive character and conformation of cytochrome c (Cyt c) molecule. Annealing-induced morphometric or structural changes of ITO nanoparticles were characterized by instruments of transmission electron microscopy, x-ray diffraction, and Raman scattering. Semiconductor ITO nanoparticle-enhanced Raman scattering of Cyt c was observed and the enhanced efficiency was found to closely depend on the surface structures which control the adsorbance of buffer anions needed for Cyt c loading. Direct electron transfer between Cyt c and ITO surface at the moment of molecular elastic collision was found and a reverse electron transfer process for O-terminated surface and metal-terminated surface was observed, according to absorption spectroscopic measurement on the residual solution.

  16. Interaction between indium tin oxide nanoparticles and cytochrome c: A surface-enhanced Raman scattering and absorption spectroscopic study

    NASA Astrophysics Data System (ADS)

    Yang, Yimin; Du, Deyang; Kong, Fan; Fan, Jiyang; Qiu, Teng

    2015-06-01

    Indium-tin-oxide (ITO) nanoparticles were annealed in vacuum or reducing atmosphere to obtain different surface structures and investigate their influence on the adsorptive character and conformation of cytochrome c (Cyt c) molecule. Annealing-induced morphometric or structural changes of ITO nanoparticles were characterized by instruments of transmission electron microscopy, x-ray diffraction, and Raman scattering. Semiconductor ITO nanoparticle-enhanced Raman scattering of Cyt c was observed and the enhanced efficiency was found to closely depend on the surface structures which control the adsorbance of buffer anions needed for Cyt c loading. Direct electron transfer between Cyt c and ITO surface at the moment of molecular elastic collision was found and a reverse electron transfer process for O-terminated surface and metal-terminated surface was observed, according to absorption spectroscopic measurement on the residual solution.

  17. Stimulated Raman spectroscopy and nanoscopy of molecules using near field photon induced forces without resonant electronic enhancement gain

    NASA Astrophysics Data System (ADS)

    Tamma, Venkata Ananth; Huang, Fei; Nowak, Derek; Kumar Wickramasinghe, H.

    2016-06-01

    We report on stimulated Raman spectroscopy and nanoscopy of molecules, excited without resonant electronic enhancement gain, and recorded using near field photon induced forces. Photon-induced interaction forces between the sharp metal coated silicon tip of an Atomic Force Microscope (AFM) and a sample resulting from stimulated Raman excitation were detected. We controlled the tip to sample spacing using the higher order flexural eigenmodes of the AFM cantilever, enabling the tip to come very close to the sample. As a result, the detection sensitivity was increased compared with previous work on Raman force microscopy. Raman vibrational spectra of azobenzene thiol and l-phenylalanine were measured and found to agree well with published results. Near-field force detection eliminates the need for far-field optical spectrometer detection. Recorded images show spatial resolution far below the optical diffraction limit. Further optimization and use of ultrafast pulsed lasers could push the detection sensitivity towards the single molecule limit.

  18. Amplification of ultra-short laser pulses via resonant backward Raman amplification in plasma

    NASA Astrophysics Data System (ADS)

    Mishra, S. K.; Andreev, A.

    2016-08-01

    In this paper, we have examined the possibility of using resonant backward Raman amplification (BRA) as an efficient mechanism in amplifying the low intensity ultra-short ( ≤ fs ) pulses using plasma as intermediate amplifying medium; such pulses are anticipated to get produced in the form of the secondary sources at ALPS (Attosecond Light Pulse Source) center of ELI (Extreme Light Infrastructure). In preliminary assessment of the scheme, the analytical expressions for the pump/seed laser pulses and plasma characteristic features are obtained which concisely describe the parameter regime of resonant BRA applicability in achieving significant amplification. The consistency of the scheme in the context of ELI-ALPS sources has been validated through particle in cell (PIC) simulations. The peak intensity of the amplified seed pulse predicted via simulation results is found in reasonable agreement with the analytical estimates. Utilizing these analytical expressions as a basis in perspective of ELI-ALPS parameter access, a specific example displaying the key plasma and laser parameters for amplifying weak seed pulse has been configured; the limitations and conceivable remedies in resonant BRA implementation have also been highlighted.

  19. Elucidation of reactive wavepackets by two-dimensional resonance Raman spectroscopy

    SciTech Connect

    Guo, Zhenkun; Molesky, Brian P.; Cheshire, Thomas P.; Moran, Andrew M.

    2015-09-28

    Traditional second-order kinetic theories fail to describe sub-picosecond photochemical reactions when solvation and vibrational dephasing undermine the assumption of equilibrium initial conditions. Four-wave mixing spectroscopies may reveal insights into such non-equilibrium processes but are limited by the single “population time” available in these types of experiments. Here, we use two-dimensional resonance Raman (2DRR) spectroscopy to expose correlations between coherent nuclear motions of the reactant and product in the photodissociation reaction of triiodide. It is shown that the transition of a nuclear wavepacket from the reactant (triiodide) to product (diiodide) states gives rise to a unique pattern of 2DRR resonances. Peaks associated with this coherent reaction mechanism are readily assigned, because they are isolated in particular quadrants of the 2DRR spectrum. A theoretical model in which the chemical reaction is treated as a vibronic coherence transfer transition from triiodide to diiodide reproduces the patterns of 2DRR resonances detected in experiments. These signal components reveal correlation between the nonequilibrium geometry of triiodide and the vibrational coherence frequency of diiodide. The 2DRR signatures of coherent reaction mechanisms established in this work may generalize to studies of ultrafast energy and charge transfer processes.

  20. Plasmon-resonant Raman spectroscopy in metallic nanoparticles: Surface-enhanced scattering by electronic excitations

    NASA Astrophysics Data System (ADS)

    Carles, R.; Bayle, M.; Benzo, P.; Benassayag, G.; Bonafos, C.; Cacciato, G.; Privitera, V.

    2015-11-01

    Since the discovery of surface-enhanced Raman scattering (SERS) 40 years ago, the origin of the "background" that is systematically observed in SERS spectra has remained questionable. To deeply analyze this phenomenon, plasmon-resonant Raman scattering was recorded under specific experimental conditions on a panel of composite multilayer samples containing noble metal (Ag and Au) nanoparticles. Stokes, anti-Stokes, and wide, including very low, frequency ranges have been explored. The effects of temperature, size (in the nm range), embedding medium (SiO2, Si3N4, or TiO2) or ligands have been successively analyzed. Both lattice (Lamb modes and bulk phonons) and electron (plasmon mode and electron-hole excitations) dynamics have been investigated. This work confirms that in Ag-based nanoplasmonics composite layers, only Raman scattering by single-particle electronic excitations accounts for the background. This latter appears as an intrinsic phenomenon independently of the presence of molecules on the metallic surface. Its spectral shape is well described by revisiting a model developed in the 1990s for analyzing electron scattering in dirty metals, and used later in superconductors. The gs factor, that determines the effective mean-free path of free carriers, is evaluated, gsexpt=0.33 ±0.04 , in good agreement with a recent evaluation based on time-dependent local density approximation gstheor=0.32 . Confinement and interface roughness effects at the nanometer range thus appear crucial to understand and control SERS enhancement and more generally plasmon-enhanced processes on metallic surfaces.

  1. A Study on the Excitation and Resonant Absorption of Coronal Loop Kink Oscillations

    NASA Astrophysics Data System (ADS)

    Yu, Dae Jung; Van Doorsselaere, Tom

    2016-11-01

    We study theoretically the issue of externally driven excitations of standing kink waves and their resonant absorption into torsionally polarized m = 1 waves in the coronal loops in pressureless plasmas. We use the ideal MHD equations, for which we develop an invariant imbedding method available in cylindrical geometry. We assume a sinusoidal density profile at the loop boundary where the density inside the loop is lower than the outside and vice versa. We present field distributions for these two cases and find that they have similar behaviors. We compare the results for the overdense loops, which describe the usual coronal loops, with the analytical solutions of Soler et al. obtained using the Frobenius method. Our results show some similarity for thin nonuniform layers but deviate a lot for thick nonuniform layers. For the first case, which describes the wave train propagation in funnels, we find that resonant absorption depends crucially on the thickness of the nonuniform boundary, loop length, and density contrast. The resonant absorption of the kink mode is dominant when the loop length is sufficiently larger compared with its radius (thin loop). The behavior of the far-field pattern of the scattered wave by the coronal loop is closely related to that of the resonant absorption. For the mode conversion phenomena in inhomogeneous plasmas, a certain universal behavior of the resonant absorption is found for the first time. We expect that the main feature may also apply to the overdense loops and discuss its relation to the damping rate.

  2. Multi-resonant absorption in ultra-thin silicon solar cells with metallic nanowires.

    PubMed

    Massiot, Inès; Colin, Clément; Sauvan, Christophe; Lalanne, Philippe; Cabarrocas, Pere Roca I; Pelouard, Jean-Luc; Collin, Stéphane

    2013-05-01

    We propose a design to confine light absorption in flat and ultra-thin amorphous silicon solar cells with a one-dimensional silver grating embedded in the front window of the cell. We show numerically that multi-resonant light trapping is achieved in both TE and TM polarizations. Each resonance is analyzed in detail and modeled by Fabry-Perot resonances or guided modes via grating coupling. This approach is generalized to a complete amorphous silicon solar cell, with the additional degrees of freedom provided by the buffer layers. These results could guide the design of resonant structures for optimized ultra-thin solar cells. PMID:24104424

  3. Impact of MIE-Resonances on the Atmospheric Absorption of Water Clouds

    NASA Technical Reports Server (NTRS)

    Wiscombe, W.; Kinne, S.; Nussenzveig, H.; Lau, William K. M. (Technical Monitor)

    2002-01-01

    Clouds strongly modulate radiative transfer processes in the Earth's atmosphere. Studies, which simulate bulk properties of clouds, such as absorption, require methods that accurately account for multiple scattering among individual cloud particles. Multiple scattering processes are well described by MIE-theory, if interacting particles have a spherical shape. This is a good assumption for water droplets. Thus, simulations for water clouds (especially for interactions with solar radiation) usually apply readily available MIE-codes. The presence of different drop-sizes, however, necessitates repetitive calculations for many sizes. The usual representation by a few sizes is likely to miss contributions from densely distributed, sharp resonances. Despite their usually narrow width, integrated over the entire size-spectrum of a cloud droplet distribution, the impact of missed resonances could add up. The consideration of these resonances tends to increase cloud extinction and cloud absorption. This mechanism for a larger (than by MIE-methods predicted) solar absorption has the potential to explain observational evidence of larger than predicted cloud absorption at solar wavelengths. The presentation will address the absorption impact of added resonances for typical properties of water clouds (e.g. drop size distributions, drop concentrations and cloud geometry). Special attention will be given to scenarios with observational evidence of law than simulated solar absorption; particularly if simultaneous measurements of cloud micro- and macrophysical properties are available.

  4. Surface-Enhanced Resonance Raman Scattering and Visible Extinction Spectroscopy of Copper Chlorophyllin: An Upper Level Chemistry Experiment

    ERIC Educational Resources Information Center

    Schnitzer, Cheryl S.; Reim, Candace Lawson; Sirois, John J.; House, Paul G.

    2010-01-01

    Advanced chemistry students are introduced to surface-enhanced resonance Raman scattering (SERRS) by studying how sodium copper chlorophyllin (CuChl) adsorbs onto silver colloids (CuChl/Ag) as a function of pH. Using both SERRS and visible extinction spectroscopy, the extent of CuChl adsorption and colloidal aggregation are monitored. Initially at…

  5. In situ electron spin resonance and Raman spectroscopic studies of the electrochemical process of conducting polypyrrole films

    SciTech Connect

    Zhong, C.J.; Tian, Z.Q.; Tian, Z.W. )

    1990-03-08

    The electrochemical redox properties of conducting polypyrrole (PPy) films coated on electrodes are investigated in aqueous solutions by use of the in situ techniques of electron spin resonance (ESR) and Raman spectroscopy. Comparisons between the experimental in situ ESR data and a theoretical kinetic prediction on the basis of the polaron-bipolaron model are presented.

  6. Characterization of carotenoids in soil bacteria and investigation of their photodegradation by UVA radiation via resonance Raman spectroscopy.

    PubMed

    Kumar B N, Vinay; Kampe, Bernd; Rösch, Petra; Popp, Jürgen

    2015-07-01

    A soil habitat consists of an enormous number of pigmented bacteria with the pigments mainly composed of diverse carotenoids. Most of the pigmented bacteria in the top layer of the soil are photoprotected from exposure to huge amounts of UVA radiation on a daily basis by these carotenoids. The photostability of these carotenoids depends heavily on the presence of specific features like a carbonyl group or an ionone ring system on its overall structure. Resonance Raman spectroscopy is one of the most sensitive and powerful techniques to detect and characterize these carotenoids and also monitor processes associated with them in their native system at a single cell resolution. However, most of the resonance Raman profiles of carotenoids have very minute differences, thereby making it extremely difficult to confirm if these differences are attributed to the presence of different carotenoids or if it is a consequence of their interaction with other cellular components. In this study, we devised a method to overcome this problem by monitoring also the photodegradation of the carotenoids in question by UVA radiation wherein a differential photodegradation response will confirm the presence of different carotenoids irrespective of the proximities in their resonance Raman profiles. Using this method, the detection and characterization of carotenoids in pure cultures of five species of pigmented coccoid soil bacteria is achieved. We also shed light on the influence of the structure of the carotenoid on its photodegradation which can be exploited for use in the characterization of carotenoids via resonance Raman spectroscopy.

  7. Lignin Radicals in the Plant Cell Wall Probed by Kerr-Gated Resonance Raman Spectroscopy

    PubMed Central

    Barsberg, Søren; Matousek, Pavel; Towrie, Mike; Jørgensen, Henning; Felby, Claus

    2006-01-01

    Lignin radicals are crucial intermediates for lignin biosynthesis in the cell wall of vascular plants. In this work they were for the first time, to our knowledge, selectively observed in wood cell walls by laser-based Kerr-gated resonance Raman spectroscopy, and the observations were supported by density functional theory prediction of their vibrational properties. For dry wood cells a lignin radical Raman band is observed at 1570 cm−1 irrespective of species. For wet beech cells they were generated in situ and observed at 1606 cm−1. DFT/B3LYP/6-31+G(d) modeling results support that in beech they are formed from syringyl (S) phenolic moieties and in spruce from guaiacyl (G) phenolic moieties. The observed lignin radical band is predicted as G is ∼1597 cm−1 and S is ∼1599 cm−1, respectively, and is assigned the (Wilson notation) ν8a phenyl ring mode. The RR band probes lignin radical properties, e.g., spin density distribution, and these respond to charge polarization or hydrogen bonding to proximate water molecules. These observations can be crucial for an understanding of the factors that control cell wall structure during biosynthesis of vascular plants and demonstrate the unique potential of RR spectroscopy of lignin radicals. PMID:16443659

  8. Interface Coupling in Twisted Multilayer Graphene by Resonant Raman Spectroscopy of Layer Breathing Modes.

    PubMed

    Wu, Jiang-Bin; Hu, Zhi-Xin; Zhang, Xin; Han, Wen-Peng; Lu, Yan; Shi, Wei; Qiao, Xiao-Fen; Ijiäs, Mari; Milana, Silvia; Ji, Wei; Ferrari, Andrea C; Tan, Ping-Heng

    2015-07-28

    Raman spectroscopy is the prime nondestructive characterization tool for graphene and related layered materials. The shear (C) and layer breathing modes (LBMs) are due to relative motions of the planes, either perpendicular or parallel to their normal. This allows one to directly probe the interlayer interactions in multilayer samples. Graphene and other two-dimensional (2d) crystals can be combined to form various hybrids and heterostructures, creating materials on demand with properties determined by the interlayer interaction. This is the case even for a single material, where multilayer stacks with different relative orientations have different optical and electronic properties. In twisted multilayer graphene there is a significant enhancement of the C modes due to resonance with new optically allowed electronic transitions, determined by the relative orientation of the layers. Here we show that this applies also to the LBMs, which can be now directly measured at room temperature. We find that twisting has a small effect on LBMs, quite different from the case of the C modes. This implies that the periodicity mismatch between two twisted layers mostly affects shear interactions. Our work shows that ultralow-frequency Raman spectroscopy is an ideal tool to uncover the interface coupling of 2d hybrids and heterostructures.

  9. Distinguishing Unfolding and Functional Conformational Transitions of Calmodulin Using Ultraviolet Resonance Raman Spectroscopy

    SciTech Connect

    Jones, Eric M.; Balakrishnan, G.; Squier, Thomas C.; Spiro, Thomas

    2014-06-14

    Calmodulin (CaM) is a ubiquitous moderator protein for calcium signaling in all eukaryotic cells. This small calcium-binding protein exhibits a broad range of structural transitions, including domain opening and folding-unfolding, that allow it to recognize a wide variety of binding partners in vivo. While the static structures of CaM associated with its various binding activities are fairly well known, it has been challenging to examine the dynamics of transition between these structures in real-time, due to a lack of suitable spectroscopic probes of CaM structure. In this paper, we examine the potential of ultraviolet resonance Raman (UVRR) spectroscopy for clarifying the nature of structural transitions in CaM. We find that the UVRR spectral change (with 229 nm excitation) due to thermal unfolding of CaM is qualitatively different from that associated with opening of the C-terminal domain in response to Ca2+ binding. This spectral difference is entirely due to differences in teritary contacts at the inter-domain tyrosine residue Tyr138, toward which other spectroscopic methods are not sensitive. We conclude that UVRR is ideally suited to identifying the different types of structural transitions in CaM and other proteins with conformation-sensitive tyrosine residues, opening a path to time-resolved studies of CaM dynamics using Raman spectroscopy.

  10. Rapid resonance Raman microspectroscopy to probe carbon dioxide fixation by single cells in microbial communities

    PubMed Central

    Li, Mengqiu; Canniffe, Daniel P; Jackson, Philip J; Davison, Paul A; FitzGerald, Simon; Dickman, Mark J; Burgess, J Grant; Hunter, C Neil; Huang, Wei E

    2012-01-01

    Photosynthetic microorganisms play crucial roles in aquatic ecosystems and are the major primary producers in global marine ecosystems. The discovery of new bacteria and microalgae that play key roles in CO2 fixation is hampered by the lack of methods to identify hitherto-unculturable microorganisms. To overcome this problem we studied single microbial cells using stable-isotope probing (SIP) together with resonance Raman (RR) microspectroscopy of carotenoids, the light-absorbing pigments present in most photosynthetic microorganisms. We show that fixation of 13CO2 into carotenoids produces a red shift in single-cell RR (SCRR) spectra and that this SCRR–SIP technique is sufficiently sensitive to detect as little as 10% of 13C incorporation. Mass spectrometry (MS) analysis of labelled cellular proteins verifies that the red shift in carotenoid SCRR spectra acts as a reporter of the 13C content of single cells. Millisecond Raman imaging of cells in mixed cultures and natural seawater samples was used to identify cells actively fixing CO2, demonstrating that the SCRR–SIP is a noninvasive method for the rapid and quantitative detection of CO2 fixation at the single cell level in a microbial community. The SCRR–SIP technique may provide a direct method for screening environmental samples, and could help to reveal the ecophysiology of hitherto-unculturable microorganisms, linking microbial species to their ecological function in the natural environment. PMID:22113377

  11. Optical pathology study of human abdominal aorta tissues using confocal micro resonance Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Liu, Cheng-hui; Boydston-White, Susie; Wang, Wubao; Sordillo, Laura A.; Shi, Lingyan; Weisberg, Arel; Tomaselli, Vincent P.; Sordillo, Peter P.; Alfano, Robert R.

    2016-03-01

    Resonance Raman (RR) spectroscopic technique has a high potential for label-free and in-situ detection of biomedical lesions in vivo. This study evaluates the ability of RR spectroscopy method as an optical histopathology tool to detect the atherosclerotic plaque states of abdominal aorta in vitro. This part demonstrates the RR spectral molecular fingerprint features from different sites of the atherosclerotic abdominal aortic wall tissues. Total 57 sites of five pieces aortic samples in intimal and adventitial wall from an autopsy specimen were examined using confocal micro Raman system of WITec 300R with excitation wavelength of 532nm. The preliminary RR spectral biomarkers of molecular fingerprints indicated that typical calcified atherosclerotic plaque (RR peak at 964cm-1) tissue; fibrolipid plaque (RR peaks at 1007, 1161, 1517 and 2888cm-1) tissue, lipid pool with the fatty precipitation cholesterol) with collagen type I (RR peaks at 864, 1452, 1658, 2888 and 2948cm-1) in the soft tissue were observed and investigated.

  12. Low skin carotenoid concentration measured by resonance Raman spectroscopy is associated with metabolic syndrome in adults.

    PubMed

    Holt, Edward W; Wei, Esther K; Bennett, Nancy; Zhang, Laura M

    2014-10-01

    Oxidative stress is increased in patients with metabolic syndrome (MS). Antioxidants, including carotenoids, are decreased in MS. We hypothesized that a low skin carotenoid score (SCS), calculated using resonance Raman spectroscopy, would correlate with the presence of MS. We retrospectively reviewed consecutive patients referred for dietary assessment between 2010 and 2012. For each patient, a nutrition history, medical history, and SCS were recorded. χ(2) and Student t test were used to determine factors associated with MS. Multivariate logistic regression was used to identify factors associated with MS. One hundred fifty-five patients were included. The mean age was 54.1 ± 13.1 years, and the mean body mass index was 28.3 ± 6.1 kg/m(2). Metabolic syndrome was present in 43.9% of patients. The mean SCS was 28 084 ± 14 006 Raman counts (RC), including 23 058 ± 9812 RC for patients with MS and 32 011 ± 15 514 RC for patients without MS (P = .0001). In a multivariate analysis, SCS less than 25 000 RC (odds ratio, 3.71; 95% confidence interval, 1.36-10.7; P = .01) was independently associated with MS. A higher number of MS components was associated with a progressively lower SCS (P = .004). In a consecutive sample of patients referred for dietary assessment, a noninvasively measured SCS was lower among patients with MS.

  13. Raman and fluorescence characteristics of resonant inelastic X-ray scattering from doped superconducting cuprates

    DOE PAGES

    Huang, H. Y.; Jia, C. J.; Chen, Z. Y.; Wohlfeld, K.; Moritz, B.; Devereaux, T. P.; Wu, W. B.; Okamoto, J.; Lee, W. S.; Hashimoto, M.; et al

    2016-01-22

    Measurements of spin excitations are essential for an understanding of spin-mediated pairing for superconductivity; and resonant inelastic X-ray scattering (RIXS) provides a considerable opportunity to probe high-energy spin excitations. However, whether RIXS correctly measures the collective spin excitations of doped superconducting cuprates remains under debate. Here we demonstrate distinct Raman- and fluorescence-like RIXS excitations of Bi1.5Pb0.6Sr1.54CaCu2O8+δ. Combining photon-energy and momentum dependent RIXS measurements with theoretical calculations using exact diagonalization provides conclusive evidence that the Raman-like RIXS excitations correspond to collective spin excitations, which are magnons in the undoped Mott insulators and evolve into paramagnons in doped superconducting compounds. In contrast,more » the fluorescence-like shifts are due primarily to the continuum of particle-hole excitations in the charge channel. Our results show that under the proper experimental conditions RIXS indeed can be used to probe paramagnons in doped high-Tc cuprate superconductors.« less

  14. Silver-particle-based surface-enhanced resonance Raman scattering spectroscopy for biomolecular sensing and recognition.

    PubMed

    Kim, Kwan; Lee, Hyun Sook; Kim, Nam Hoon

    2007-05-01

    We demonstrate in this work that 2-microm-sized Ag (microAg) powders can be used as a core material for constructing biomolecular sensing/recognition units operating via surface-enhanced resonance Raman scattering (SERRS). This is possible because microAg powders are very efficient substrates for both the diffuse reflectance IR and the surface-enhanced Raman scattering-SERRS spectroscopic characterization of molecular adsorbates prepared in a similar manner on silver surfaces. Besides, the agglomeration of microAg particles in a buffer solution can be prevented by the layer-by-layer deposition of cationic and anionic polyelectrolytes such as poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA). In this particular study, we used rhodamine B isothiocyanate (RhBITC) as a SERRS marker molecule, and microAg powders adsorbed consecutively with RhBITC and PAH-PAA bilayers were finally derivatized with biotinylated poly(L-lysine). On the basis of the nature of the SERRS peaks of RhBITC, those microAg powders were confirmed to selectively recognize streptavidin molecules down to concentrations of 10(-10) g mL-1. Since a number of different molecules can be used as SERS-SERRS marker molecules, the present method proves to be an invaluable tool for multiplex biomolecular sensing/recognition via SERS and SERRS.

  15. A Swept Wavelength Optical Resonant Raman Detector (SWOrRD) for Bio-detection.

    NASA Astrophysics Data System (ADS)

    Manka, Charles; Grun, Jacob; Zabetakis, Dan; Nikitin, Sergei; Comanescu, Gelu; Bowles, Jeff; Gillis, David

    2007-10-01

    A new device that sequentially illuminates bacteria with different ultraviolet wavelengths and obtains a spectrum at each wavelength has been developed and tested. The available wavelengths are spaced at ˜ 0.3 nm intervals from 210 to 280 nm. Tuning from one wavelength to another requires 20 to 60 seconds, depending on the wavelength region. Liquid samples are contained in a quartz cuvette, illuminated side-on and the scattered light is collected at 90 degrees. A double spectrograph and CCD camera record the resulting Raman Spectra. Spectra from the sequential illumination are assembled into a data ``cube'' for processing and analysis. Measurements of two-dimensional resonant-Raman spectra of bacteria are presented and the applicability of the method for the identification of bacteria, including differentiation of genetically similar species, is demonstrated. We anticipate that information within such two-dimensional spectra will allow identification of bacteria, as well as chemicals, in complex environments containing multiple organisms and chemicals. This device may lead to instruments that rapidly identify bacteria in hospital and food process settings, for screening large populations, and for biochemical-threat warning systems.

  16. Characterizing millisecond intermediates in hemoproteins using rapid-freeze-quenched resonance Raman spectroscopy

    PubMed Central

    Matsumura, Hirotoshi; Moënne-Loccoz, Pierre

    2014-01-01

    Summary The combination of rapid-freeze-quenching (RFQ) technique and resonance Raman (RR) spectroscopy represents a unique tool to investigate the nature of short-lived intermediates formed during the enzymatic reaction of metalloproteins. Commercially available equipment allows trapping of intermediates within the millisecond to second timescale for low-temperature RR analysis and direct detection of metal-ligand vibrations and porphyrin skeletal vibrations in hemoproteins. This chapter briefly discusses previous RFQ-RR studies carried-out in our laboratory, and presents as a practical example protocols for the preparation of RFQ samples of the reaction of metmyoglobin with nitric oxide (NO) which requires anaerobic conditions. We also describe important controls and practical procedure for the analysis of these samples by low-temperature RR spectroscopy. PMID:24639256

  17. Operational electrochemical stability of thiophene-thiazole copolymers probed by resonant Raman spectroscopy

    SciTech Connect

    Wade, Jessica; Wood, Sebastian; Kim, Ji-Seon; Beatrup, Daniel; Hurhangee, Michael; McCulloch, Iain; Durrant, James R.; Bronstein, Hugo

    2015-06-28

    We report on the electrochemical stability of hole polarons in three conjugated polymers probed by resonant Raman spectroscopy. The materials considered are all isostructural to poly(3-hexyl)thiophene, where thiazole units have been included to systematically deepen the energy level of the highest occupied molecular orbital (HOMO). We demonstrate that increasing the thiazole content planarizes the main conjugated backbone of the polymer and improves the electrochemical stability in the ground state. However, these more planar thiazole containing polymers are increasingly susceptible to electrochemical degradation in the polaronic excited state. We identify the degradation mechanism, which targets the C=N bond in the thiazole units and results in disruption of the main polymer backbone conjugation. The introduction of thiazole units to deepen the HOMO energy level and increase the conjugated backbone planarity can be beneficial for the performance of certain optoelectronic devices, but the reduced electrochemical stability of the hole polaron may compromise their operational stability.

  18. Peak separation and sorting by coherent 2D resonance Raman spectroscopy.

    PubMed

    Chen, Peter C; Joyner, Candace C

    2005-09-01

    The ability to separate and sort peaks is explored using a new coherent two-dimensional form of resonance Raman spectroscopy. This experimental technique distributes normally congested rotational-vibrational peaks along a series of curved lines according to vibrational sequence, rotational quantum number, and selection rule. Each line consists of rotational-vibrational peaks that have the same vibrational sequence and the same value for DeltaJ, distributed in order by rotational quantum number. For diatomic molecules, these lines originate from points where they initially travel in opposite or orthogonal directions in two-dimensional space, which helps facilitate the separation between lines. Simulations and experimental results on C2 in a flame confirm the ability to separate and sort these normally congested rotational-vibrational peaks. This method appears to provide a solution to the long-standing problems of spectral congestion and disorder in gas-phase electronic spectra.

  19. 13C Solid State Nuclear Magnetic Resonance and µ-Raman Spectroscopic Characterization of Sicilian Amber.

    PubMed

    Barone, Germana; Capitani, Donatella; Mazzoleni, Paolo; Proietti, Noemi; Raneri, Simona; Longobardo, Ugo; Di Tullio, Valeria

    2016-08-01

    (13)C cross-polarization magic angle spinning (CPMAS) nuclear magnetic resonance (NMR) and µ-Raman spectroscopy were applied to characterize Sicilian amber samples. The main goal of this work was to supply a complete study of simetite, highlighting discriminating criteria useful to distinguish Sicilian amber from fossil resins from other regions and laying the foundations for building a spectroscopic database of Sicilian amber. With this aim, a private collection of unrefined simetite samples and fossil resins from the Baltic region and Dominican Republic was analyzed. Overall, the obtained spectra permitted simetite to be distinguished from the other resins. In addition, principal component analysis (PCA) was applied to the spectroscopic data, allowing the clustering of simetite samples with respect to the Baltic and Dominican samples and to group the simetite samples in two sets, depending on their maturity. Finally, the analysis of loadings allowed for a better understanding of the spectral features that mainly influenced the discriminating characteristics of the investigated ambers.

  20. Freely designable optical frequency conversion in Raman-resonant four-wave-mixing process

    PubMed Central

    Zheng, Jian; Katsuragawa, Masayuki

    2015-01-01

    Nonlinear optical processes are governed by the relative-phase relationships among the relevant electromagnetic fields in these processes. In this Report, we describe the physics of arbitrary manipulation of Raman-resonant four-wave-mixing process by artificial control of relative phases. As a typical example, we show freely designable optical-frequency conversions to extreme spectral regions, mid-infrared and vacuum-ultraviolet, with near-unity quantum efficiencies. Furthermore, we show that such optical-frequency conversions can be realized by using a surprisingly simple technology where transparent plates are placed in a nonlinear optical medium and their positions and thicknesses are adjusted precisely. In a numerical simulation assuming practically applicable parameters in detail, we demonstrate a single-frequency tunable laser that covers the whole vacuum-ultraviolet spectral range of 120 to 200 nm. PMID:25748023

  1. Raman spectroscopy of magneto-phonon resonances in graphene and graphite

    NASA Astrophysics Data System (ADS)

    Goler, Sarah; Yan, Jun; Pellegrini, Vittorio; Pinczuk, Aron

    2012-08-01

    The magneto-phonon resonance or MPR occurs in semiconductor materials when the energy spacing between Landau levels is continuously tuned to cross the energy of an optical phonon mode. MPRs have been largely explored in bulk semiconductors, in two-dimensional systems and in quantum dots. Recently there has been significant interest in the MPR interactions of the Dirac fermion magneto-excitons in graphene, and a rich splitting and anti-crossing phenomena of the even parity E2g long wavelength optical phonon mode have been theoretically proposed and experimentally observed. The MPR has been found to crucially depend on disorder in the graphene layer. This is a feature that creates new venues for the study of interplays between disorder and interactions in the atomic layers. We review here the fundamentals of MRP in graphene and the experimental Raman scattering works that have led to the observation of these phenomena in graphene and graphite.

  2. Freely designable optical frequency conversion in Raman-resonant four-wave-mixing process

    NASA Astrophysics Data System (ADS)

    Zheng, Jian; Katsuragawa, Masayuki

    2015-03-01

    Nonlinear optical processes are governed by the relative-phase relationships among the relevant electromagnetic fields in these processes. In this Report, we describe the physics of arbitrary manipulation of Raman-resonant four-wave-mixing process by artificial control of relative phases. As a typical example, we show freely designable optical-frequency conversions to extreme spectral regions, mid-infrared and vacuum-ultraviolet, with near-unity quantum efficiencies. Furthermore, we show that such optical-frequency conversions can be realized by using a surprisingly simple technology where transparent plates are placed in a nonlinear optical medium and their positions and thicknesses are adjusted precisely. In a numerical simulation assuming practically applicable parameters in detail, we demonstrate a single-frequency tunable laser that covers the whole vacuum-ultraviolet spectral range of 120 to 200 nm.

  3. Solvent effects on the resonance Raman spectra of bacteriochlorophyll a cation radical

    NASA Astrophysics Data System (ADS)

    Misono, Yasuhito; Nishizawa, Ei-ichi; Limantara, Leenawaty; Koyama, Yasushi; Itoh, Koichi

    1995-04-01

    Resonance Raman (RR) spectra were measured for the cation radical of bacteriochlorophyll a in acetone, methanol, dichloromethane and mixed solvents of acetone and methanol. The ring-breathing (C a-C m stretching) frequency of the radical (abbreviated as vr+) was observed at 1601 cm -1 in acetone (forming a penta-coordinated monomer), at 1587 cm -1 in a methanol (forming a hexa-coordinated monomer) and at 1600 cm -1 in dichloromethane (forming a penta-coordinated aggregate). The RR spectrum of the radical in dichloromethane is almost identical to the transient RR spectrum ascribed to 'the aggregated T 1 species of Bchl a' formed in the particular solvent by Nishizawa, Limantara, Nanjou, Nagae, Kakuno and Koyama, indicating that their interpretation needs to be revised.

  4. Secondary and tertiary structure of the A-state of cytochrome c from resonance Raman spectroscopy.

    PubMed Central

    Jordan, T.; Eads, J. C.; Spiro, T. G.

    1995-01-01

    Ferricytochrome c can be converted to the partially folded A-state at pH 2.2 in the presence of 1.5 M NaCl. The structure of the A-state has been studied in comparison with the native and unfolded states, using resonance Raman spectroscopy with visible and ultraviolet excitation wavelengths. Spectra obtained with 200 nm excitation show a decrease in amide II intensity consistent with loss of structure for the 50s and 70s helices. The 230-nm spectra contain information on vibrational modes of the single Trp 59 side chain and the four tyrosine side chains (Tyr 48, 67, 74, and 97). The Trp 59 modes indicate that the side chain remains in a hydrophobic environment but loses its tertiary hydrogen bond and is rotationally disordered. The tyrosine modes Y8b and Y9a show disruption of tertiary hydrogen bonding for the Tyr 48, 67, and 74 side chains. The high-wavenumber region of the 406.7-nm resonance Raman spectrum reveals a mixed spin heme iron atom, which arises from axial coordination to His 18 and a water molecule. The low-frequency spectral region reports on heme distortions and indicates a reduced degree of interaction between the heme and the polypeptide chain. A structural model for the A-state is proposed in which a folded protein subdomain, consisting of the heme and the N-terminal, C-terminal, and 60s helices, is stabilized through nonbonding interactions between helices and with the heme. PMID:7613469

  5. Secondary and tertiary structure of the A-state of cytochrome c from resonance Raman spectroscopy.

    PubMed

    Jordan, T; Eads, J C; Spiro, T G

    1995-04-01

    Ferricytochrome c can be converted to the partially folded A-state at pH 2.2 in the presence of 1.5 M NaCl. The structure of the A-state has been studied in comparison with the native and unfolded states, using resonance Raman spectroscopy with visible and ultraviolet excitation wavelengths. Spectra obtained with 200 nm excitation show a decrease in amide II intensity consistent with loss of structure for the 50s and 70s helices. The 230-nm spectra contain information on vibrational modes of the single Trp 59 side chain and the four tyrosine side chains (Tyr 48, 67, 74, and 97). The Trp 59 modes indicate that the side chain remains in a hydrophobic environment but loses its tertiary hydrogen bond and is rotationally disordered. The tyrosine modes Y8b and Y9a show disruption of tertiary hydrogen bonding for the Tyr 48, 67, and 74 side chains. The high-wavenumber region of the 406.7-nm resonance Raman spectrum reveals a mixed spin heme iron atom, which arises from axial coordination to His 18 and a water molecule. The low-frequency spectral region reports on heme distortions and indicates a reduced degree of interaction between the heme and the polypeptide chain. A structural model for the A-state is proposed in which a folded protein subdomain, consisting of the heme and the N-terminal, C-terminal, and 60s helices, is stabilized through nonbonding interactions between helices and with the heme.

  6. Resonance Raman Intensities Demonstrate that C5 Substituents Affect the Initial Excited-State Structural Dynamics of Uracil More than C6 Substituents.

    PubMed

    Teimoory, Faranak; Loppnow, Glen R

    2016-05-01

    Resonance Raman derived initial excited-state structural dynamics provide insight into the photochemical mechanisms of pyrimidine nucleobases, in which the photochemistry appears to be dictated by the C5 and C6 substituents. The absorption and resonance Raman spectra and excitation profiles of 5,6-dideuterouracil were measured to further test this photochemical dependence on the C5 and C6 substituents. The resulting set of excited-state reorganization energies of the observed internal coordinates were calculated and compared to those of other 5- and 6-substituted uracils. The results show that the initial excited-state dynamics along the C5C6 stretch responds to changes in mass at C5 and C6 in the same manner but that the in-plane bends at C5 and C6 are more sensitive to substituents at the C5 position than at the C6 position. In addition, the presence of two deuterium substituents at C5 and C6 decreases the initial excited-state structural dynamics along these in-plane bends, in contrast to what is observed in the presence of two CH3 groups on C5 and C6. The results are discussed in the context of DNA nucleobase photochemistry.

  7. Hollow Au/Ag nanostars displaying broad plasmonic resonance and high surface-enhanced Raman sensitivity

    NASA Astrophysics Data System (ADS)

    Garcia-Leis, Adianez; Torreggiani, Armida; Garcia-Ramos, Jose Vicente; Sanchez-Cortes, Santiago

    2015-08-01

    Bimetallic Au/Ag hollow nanostar (HNS) nanoparticles with different morphologies were prepared in this work. These nanoplatforms were obtained by changing the experimental conditions (concentration of silver and chemical reductors, hydroxylamine and citrate) and by using Ag nanostars as template nanoparticles (NPs) through galvanic replacement. The goal of this research was to create bimetallic Au/Ag star-shaped nanoparticles with advanced properties displaying a broader plasmonic resonance, a cleaner exposed surface, and a high concentration of electromagnetic hot spots on the surface provided by the special morphology of nanostars. The size, shape, and composition of Ag as well as their optical properties were studied by extinction spectroscopy, hyperspectral dark field microscopy, transmission and scanning electron microscopy (TEM and SEM), and energy dispersive X-ray spectroscopy (EDX). Finally, the surface-enhanced Raman scattering (SERS) activity of these HNS was investigated by using thioflavin T, a biomarker of the β-amyloid fibril formation, responsible for Alzheimer's disease. Lucigenin, a molecule displaying different SERS activities on Au and Ag, was also used to explore the presence of these metals on the NP surface. Thus, a relationship between the morphology, plasmon resonance and SERS activity of these new NPs was made.Bimetallic Au/Ag hollow nanostar (HNS) nanoparticles with different morphologies were prepared in this work. These nanoplatforms were obtained by changing the experimental conditions (concentration of silver and chemical reductors, hydroxylamine and citrate) and by using Ag nanostars as template nanoparticles (NPs) through galvanic replacement. The goal of this research was to create bimetallic Au/Ag star-shaped nanoparticles with advanced properties displaying a broader plasmonic resonance, a cleaner exposed surface, and a high concentration of electromagnetic hot spots on the surface provided by the special morphology of nanostars

  8. Microwave Resonator Measurements of Atmospheric Absorption Coefficients: A Preliminary Design Study

    NASA Technical Reports Server (NTRS)

    Walter, Steven J.; Spilker, Thomas R.

    1995-01-01

    A preliminary design study examined the feasibility of using microwave resonator measurements to improve the accuracy of atmospheric absorption coefficients and refractivity between 18 and 35 GHz. Increased accuracies would improve the capability of water vapor radiometers to correct for radio signal delays caused by Earth's atmosphere. Calibration of delays incurred by radio signals traversing the atmosphere has applications to both deep space tracking and planetary radio science experiments. Currently, the Cassini gravity wave search requires 0.8-1.0% absorption coefficient accuracy. This study examined current atmospheric absorption models and estimated that current model accuracy ranges from 5% to 7%. The refractivity of water vapor is known to 1% accuracy, while the refractivity of many dry gases (oxygen, nitrogen, etc.) are known to better than 0.1%. Improvements to the current generation of models will require that both the functional form and absolute absorption of the water vapor spectrum be calibrated and validated. Several laboratory techniques for measuring atmospheric absorption and refractivity were investigated, including absorption cells, single and multimode rectangular cavity resonators, and Fabry-Perot resonators. Semi-confocal Fabry-Perot resonators were shown to provide the most cost-effective and accurate method of measuring atmospheric gas refractivity. The need for accurate environmental measurement and control was also addressed. A preliminary design for the environmental control and measurement system was developed to aid in identifying significant design issues. The analysis indicated that overall measurement accuracy will be limited by measurement errors and imprecise control of the gas sample's thermodynamic state, thermal expansion and vibration- induced deformation of the resonator structure, and electronic measurement error. The central problem is to identify systematic errors because random errors can be reduced by averaging

  9. Deformations of the Heme Group of Different Ferrocytochrome c Proteins Probed by Resonance Raman Spectroscopy

    SciTech Connect

    Hagarman, Andrew; Schweitzer-Stenner, Reinhard; Wallace, Carmichael; Laberge, Monique

    2008-11-14

    We measured the low-frequency polarized resonance Raman spectra of horse heart, chicken, and yeast(C102T) ferrocytochromes c with Soret excitation. We examined the out-of-plane deformations of the heme groups by determining the relative intensities and depolarization ratios of a variety of out-of-plane and in-plane Raman active bands. Analysis of relative Raman intensities shows differences in non-planarity of the heme groups of yeast(C102T), horse heart and chicken cytochrome c. Cytochrome c has been shown to have a dominant ruffling (B{sub 1u}) deformation by means of normal coordinate structural decomposition (NSD) analysis of the heme group in crystal structures. The presence and intensity of B{sub 1u} modes, {gamma}{sub 10}-{gamma}{sub 12}, support the indication of ruffling being the major contribution to the non-planar deformations in cytochrome c. Other types of non-planar deformations like doming (A{sub 2U}) and waving (E{sub g}) can be deduced from the Raman activity of {gamma}{sub 5} (A{sub 2u}), {gamma}{sub 21} and {gamma}{sub 22} (E{sub g}). The depolarization ratios of {gamma}{sub 5}, {gamma}{sub 10}, {gamma}{sub 11} and {gamma}{sub 12} are larger than 0.125, indicating the presence of other deformations such as saddling (B{sub 2u}) and propellering (A{sub 1u}), which is again in agreement with the crystal structures of horse heart and yeast ferrocytochrome c. An analysis of the intensities and depolarization ratios of out-of-plane modes revealed that ruffling is comparable in yeast and horse heart cytochrome c, saddling is larger and doming as well as propellering are lower in yeast cytochrome c. With respect to doming and ruffling our results contradict values obtained from the NSD analysis of the corresponding crystal structures. With respect to saddling, our data are in agreement with the crystal structure. The NSD analysis of heme structures resulting from MD simulations did not correlate very well with the spectroscopically obtained results

  10. Confined optical-phonon-assisted cyclotron resonance in quantum wells via two-photon absorption process

    NASA Astrophysics Data System (ADS)

    Phuc, Huynh Vinh; Hien, Nguyen Dinh; Dinh, Le; Phong, Tran Cong

    2016-06-01

    The effect of confined phonons on the phonon-assisted cyclotron resonance (PACR) via both one and two photon absorption processes in a quantum well is theoretically studied. We consider cases when electrons are scattered by confined optical phonons described by the Fuchs-Kliewer slab, Ridley's guided, and Huang-Zhu models. The analytical expression of the magneto-optical absorption coefficient (MOAC) is obtained by relating it to the transition probability for the absorption of photons. It predicts resonant peaks caused by transitions between Landau levels and electric subband accompanied by confined phonons emission in the absorption spectrum. The MOAC and the full-width at half-maximum (FWHM) for the intra- and inter-subband transitions are given as functions of the magnetic field, temperature, and quantum well width. In narrow quantum wells, the phonon confinement becomes more important and should be taken into account in studying FWHM.

  11. Near-resonance enhanced O2 detection for dual-broadband pure rotational coherent anti-Stokes Raman scattering with an ultraviolet-visible setup at 266 nm

    SciTech Connect

    Schenk, Martin; Seeger, Thomas; Leipertz, Alfred

    2005-07-01

    Broadband and dual-broadband coherent anti-Stokes Raman scattering (CARS) are widely established tools for nonintrusive gas diagnostics. Up to now the investigations have been mainly performed for electronic nonresonant conditions of the gas species of interest. We report on the enhancement of the O2-N2 detection limit of dual-broadband pure rotational CARS by shifting the wavelength of the narrowband pump laser from the commonly used 532-266 nm. This enhancement is caused when the Schumann-Runge absorption band is approached near 176 nm. The principal concept of this experiment, i.e., covering the Raman resonance with a single- or dual-broadband combination of lasers in the visible range and moving only the narrowband probe laser near or directly into electronic resonant conditions in the UV range, should also be applicable to broadband CARS experiments to directly exploit electronic resonance effects for the purpose of single-shot concentration measurements of minority species. To quantify the enhancement in O2 sensitivity, comparative measurements at both a 266 and a 532 nm narrowband pump laser wavelength are presented, employing a 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyram (DCM) dye laser as a broadband laser source at 635 nm. An increase of approximately 13% in the ratio of the rotational CARS cross sections of O2 and N2 was obtained. The broad spectral width of the CARS excitation profile was approximately equal for both setups. Further enhancement should be achievable by shifting the narrowband pump laser closer toward 176 nm, for example, with a frequency-doubled optical parametric oscillator or an excimer laser. The principal concept of this experiment should also be applicable to broadband CARS experiments to directly exploit electronic resonance effects of the narrowband pump laser with electronic transitions of minority species for the purpose of single-shot concentration measurements of those species.

  12. Resonance raman spectroscopic study of alumina-supported vanadium oxide catalysts with 220 and 287 nm excitation.

    SciTech Connect

    Kim, H. S.; Stair, P. C.; Chemical Sciences and Engineering Division; Northwestern Univ.

    2009-01-01

    We present detailed resonance Raman spectroscopic results excited at 220 and 287 nm for alumina-supported VO{sub x} catalysts. The anharmonic constant, harmonic wavenumber, anharmonic force constant, bond dissociation energy, and bond length change in the excited state for double bonded V{double_bond}O and single bonded V-O were obtained from fundamental and overtone frequencies. Totally symmetric and nontotally symmetric modes could be discerned and assigned on the basis of the overtone and combination progressions found in the resonance Raman spectra. Selective resonance enhancement of two different vibrational modes with two different excitation wavelengths was observed. This allowed us to establish a linear relationship between charge transfer energy and VO bond length and, consequently, to assign the higher-energy charge transfer band centered around 210?250 nm in the UV?vis spectra to the V{double_bond}O transition.

  13. Decoupling and tuning the light absorption and scattering resonances in metallic composite nanostructures.

    PubMed

    Danan, Yossef; Ramon, Yehonatan; Azougi, Jonathan; Douplik, Alexandre; Zalevsky, Zeev

    2015-11-01

    Utilizing the localized surface plasmon resonance (LSPR) effect of metallic nanoparticles enables their usage as contrast agents in a variety of applications for medical diagnostics and treatment. Those applications can use both the very strong absorption and scattering properties of the metallic nanoparticle due to their LSPR effects. There are certain applications where domination of the scattering over absorption or vice versa would be an advantage. However, the scattering and absorption resonance peaks have practically the same spectral location for solid noble metal nanoparticles at a certain domination of one over the other. In this paper we present gold nanoparticles coated with silicon that switches the order between the scattering and the absorption magnitude at the resonance peak by up to 34% in scattering-absorption ratio and tune the plasmon resonance over the spectrum by up to 56nm. This is obtained by modifying the refractive index of the silicon coating of the nanoparticle by illuminating it with a pumping light due to the plasma dispersion effect in silicon.

  14. Omnidirectional and broadband absorption enhancement from trapezoidal Mie resonators in semiconductor metasurfaces

    NASA Astrophysics Data System (ADS)

    Pala, Ragip A.; Butun, Serkan; Aydin, Koray; Atwater, Harry A.

    2016-09-01

    Light trapping in planar ultrathin-film solar cells is limited due to a small number of optical modes available in the thin-film slab. A nanostructured thin-film design could surpass this limit by providing broadband increase in the local density of states in a subwavelength volume and maintaining efficient coupling of light. Here we report a broadband metasurface design, enabling efficient and broadband absorption enhancement by direct coupling of incoming light to resonant modes of subwavelengthscale Mie nanoresonators defined in the thin-film active layer. Absorption was investigated both theoretically and experimentally in prototypes consisting of lithographically patterned, two-dimensional periodic arrays of silicon nanoresonators on silica substrates. A crossed trapezoid resonator shape of rectangular cross section is used to excite broadband Mie resonances across visible and near-IR spectra. Our numerical simulations, optical absorption measurements and photocurrent spectral response measurements demonstrate that crossed trapezoidal Mie resonant structures enable angle-insensitive, broadband absorption. A short circuit current density of 12.0 mA/cm2 is achieved in 210 nm thick patterned Si films, yielding a 4-fold increase compared to planar films of the same thickness. It is suggested that silicon metasurfaces with Mie resonator arrays can provide useful insights to guide future ultrathin-film solar cell designs incorporating nanostructured thin active layers.

  15. Omnidirectional and broadband absorption enhancement from trapezoidal Mie resonators in semiconductor metasurfaces.

    PubMed

    Pala, Ragip A; Butun, Serkan; Aydin, Koray; Atwater, Harry A

    2016-01-01

    Light trapping in planar ultrathin-film solar cells is limited due to a small number of optical modes available in the thin-film slab. A nanostructured thin-film design could surpass this limit by providing broadband increase in the local density of states in a subwavelength volume and maintaining efficient coupling of light. Here we report a broadband metasurface design, enabling efficient and broadband absorption enhancement by direct coupling of incoming light to resonant modes of subwavelengthscale Mie nanoresonators defined in the thin-film active layer. Absorption was investigated both theoretically and experimentally in prototypes consisting of lithographically patterned, two-dimensional periodic arrays of silicon nanoresonators on silica substrates. A crossed trapezoid resonator shape of rectangular cross section is used to excite broadband Mie resonances across visible and near-IR spectra. Our numerical simulations, optical absorption measurements and photocurrent spectral response measurements demonstrate that crossed trapezoidal Mie resonant structures enable angle-insensitive, broadband absorption. A short circuit current density of 12.0 mA/cm(2) is achieved in 210 nm thick patterned Si films, yielding a 4-fold increase compared to planar films of the same thickness. It is suggested that silicon metasurfaces with Mie resonator arrays can provide useful insights to guide future ultrathin-film solar cell designs incorporating nanostructured thin active layers. PMID:27641965

  16. Omnidirectional and broadband absorption enhancement from trapezoidal Mie resonators in semiconductor metasurfaces.

    PubMed

    Pala, Ragip A; Butun, Serkan; Aydin, Koray; Atwater, Harry A

    2016-09-19

    Light trapping in planar ultrathin-film solar cells is limited due to a small number of optical modes available in the thin-film slab. A nanostructured thin-film design could surpass this limit by providing broadband increase in the local density of states in a subwavelength volume and maintaining efficient coupling of light. Here we report a broadband metasurface design, enabling efficient and broadband absorption enhancement by direct coupling of incoming light to resonant modes of subwavelengthscale Mie nanoresonators defined in the thin-film active layer. Absorption was investigated both theoretically and experimentally in prototypes consisting of lithographically patterned, two-dimensional periodic arrays of silicon nanoresonators on silica substrates. A crossed trapezoid resonator shape of rectangular cross section is used to excite broadband Mie resonances across visible and near-IR spectra. Our numerical simulations, optical absorption measurements and photocurrent spectral response measurements demonstrate that crossed trapezoidal Mie resonant structures enable angle-insensitive, broadband absorption. A short circuit current density of 12.0 mA/cm(2) is achieved in 210 nm thick patterned Si films, yielding a 4-fold increase compared to planar films of the same thickness. It is suggested that silicon metasurfaces with Mie resonator arrays can provide useful insights to guide future ultrathin-film solar cell designs incorporating nanostructured thin active layers.

  17. Omnidirectional and broadband absorption enhancement from trapezoidal Mie resonators in semiconductor metasurfaces

    PubMed Central

    Pala, Ragip A.; Butun, Serkan; Aydin, Koray; Atwater, Harry A.

    2016-01-01

    Light trapping in planar ultrathin-film solar cells is limited due to a small number of optical modes available in the thin-film slab. A nanostructured thin-film design could surpass this limit by providing broadband increase in the local density of states in a subwavelength volume and maintaining efficient coupling of light. Here we report a broadband metasurface design, enabling efficient and broadband absorption enhancement by direct coupling of incoming light to resonant modes of subwavelengthscale Mie nanoresonators defined in the thin-film active layer. Absorption was investigated both theoretically and experimentally in prototypes consisting of lithographically patterned, two-dimensional periodic arrays of silicon nanoresonators on silica substrates. A crossed trapezoid resonator shape of rectangular cross section is used to excite broadband Mie resonances across visible and near-IR spectra. Our numerical simulations, optical absorption measurements and photocurrent spectral response measurements demonstrate that crossed trapezoidal Mie resonant structures enable angle-insensitive, broadband absorption. A short circuit current density of 12.0 mA/cm2 is achieved in 210 nm thick patterned Si films, yielding a 4-fold increase compared to planar films of the same thickness. It is suggested that silicon metasurfaces with Mie resonator arrays can provide useful insights to guide future ultrathin-film solar cell designs incorporating nanostructured thin active layers. PMID:27641965

  18. Hanle electromagnetically induced transparency and absorption resonances with a Laguerre Gaussian beam

    SciTech Connect

    Anupriya, J.; Ram, Nibedita; Pattabiraman, M.

    2010-04-15

    We describe a computational and experimental study on Hanle electromagnetically induced transparency and absorption resonance line shapes with a Laguerre Gaussian (LG) beam. It is seen that the LG beam profile brings about a significant narrowing in the line shape of the Hanle resonance and ground-state Zeeman coherence in comparison to a Gaussian beam. This narrowing is attributed to the azimuthal mode index of the LG field.

  19. Hollow Au/Ag nanostars displaying broad plasmonic resonance and high surface-enhanced Raman sensitivity.

    PubMed

    Garcia-Leis, Adianez; Torreggiani, Armida; Garcia-Ramos, Jose Vicente; Sanchez-Cortes, Santiago

    2015-08-28

    Bimetallic Au/Ag hollow nanostar (HNS) nanoparticles with different morphologies were prepared in this work. These nanoplatforms were obtained by changing the experimental conditions (concentration of silver and chemical reductors, hydroxylamine and citrate) and by using Ag nanostars as template nanoparticles (NPs) through galvanic replacement. The goal of this research was to create bimetallic Au/Ag star-shaped nanoparticles with advanced properties displaying a broader plasmonic resonance, a cleaner exposed surface, and a high concentration of electromagnetic hot spots on the surface provided by the special morphology of nanostars. The size, shape, and composition of Ag as well as their optical properties were studied by extinction spectroscopy, hyperspectral dark field microscopy, transmission and scanning electron microscopy (TEM and SEM), and energy dispersive X-ray spectroscopy (EDX). Finally, the surface-enhanced Raman scattering (SERS) activity of these HNS was investigated by using thioflavin T, a biomarker of the β-amyloid fibril formation, responsible for Alzheimer's disease. Lucigenin, a molecule displaying different SERS activities on Au and Ag, was also used to explore the presence of these metals on the NP surface. Thus, a relationship between the morphology, plasmon resonance and SERS activity of these new NPs was made.

  20. Structural dynamics of phenylisothiocyanate in the light-absorbing excited states: Resonance Raman and complete active space self-consistent field calculation study

    NASA Astrophysics Data System (ADS)

    Ouyang, Bing; Xue, Jia-Dan; Zheng, Xuming; Fang, Wei-Hai

    2014-05-01

    The excited state structural dynamics of phenyl isothiocyanate (PITC) after excitation to the light absorbing S2(A'), S6(A'), and S7(A') excited states were studied by using the resonance Raman spectroscopy and complete active space self-consistent field method calculations. The UV absorption bands of PITC were assigned. The vibrational assignments were done on the basis of the Fourier transform (FT)-Raman and FT-infrared measurements, the density-functional theory computations, and the normal mode analysis. The A-, B-, and C-bands resonance Raman spectra in cyclohexane, acetonitrile, and methanol solvents were, respectively, obtained at 299.1, 282.4, 266.0, 252.7, 228.7, 217.8, and 208.8 nm excitation wavelengths to probe the corresponding structural dynamics of PITC. The results indicated that the structural dynamics in the S2(A'), S6(A'), and S7(A') excited states were very different. The conical intersection point CI(S2/S1) were predicted to play important role in the low-lying excited state decay dynamics. Two major decay channels were predicted for PITC upon excitation to the S2(A') state: the radiative S2,min → S0 transition and the nonradiative S2 → S1 internal conversion via CI(S2/S1). The differences in the decay dynamics between methyl isothiocyanate and PITC in the first light absorbing excited state were discussed. The role of the intersystem crossing point ISC(S1/T1) in the excited state decay dynamics of PITC is evaluated.

  1. Structural dynamics of phenylisothiocyanate in the light-absorbing excited states: Resonance Raman and complete active space self-consistent field calculation study

    SciTech Connect

    Ouyang, Bing Xue, Jia-Dan Zheng, Xuming E-mail: zxm@zstu.edu.cn; Fang, Wei-Hai E-mail: fangwh@dnu.edu.cn

    2014-05-21

    The excited state structural dynamics of phenyl isothiocyanate (PITC) after excitation to the light absorbing S{sub 2}(A′), S{sub 6}(A′), and S{sub 7}(A′) excited states were studied by using the resonance Raman spectroscopy and complete active space self-consistent field method calculations. The UV absorption bands of PITC were assigned. The vibrational assignments were done on the basis of the Fourier transform (FT)-Raman and FT-infrared measurements, the density-functional theory computations, and the normal mode analysis. The A-, B-, and C-bands resonance Raman spectra in cyclohexane, acetonitrile, and methanol solvents were, respectively, obtained at 299.1, 282.4, 266.0, 252.7, 228.7, 217.8, and 208.8 nm excitation wavelengths to probe the corresponding structural dynamics of PITC. The results indicated that the structural dynamics in the S{sub 2}(A′), S{sub 6}(A′), and S{sub 7}(A′) excited states were very different. The conical intersection point CI(S{sub 2}/S{sub 1}) were predicted to play important role in the low-lying excited state decay dynamics. Two major decay channels were predicted for PITC upon excitation to the S{sub 2}(A′) state: the radiative S{sub 2,min} → S{sub 0} transition and the nonradiative S{sub 2} → S{sub 1} internal conversion via CI(S{sub 2}/S{sub 1}). The differences in the decay dynamics between methyl isothiocyanate and PITC in the first light absorbing excited state were discussed. The role of the intersystem crossing point ISC(S{sub 1}/T{sub 1}) in the excited state decay dynamics of PITC is evaluated.

  2. Coal thickness gauge using RRAS techniques, part 1. [radiofrequency resonance absorption

    NASA Technical Reports Server (NTRS)

    Rollwitz, W. L.; King, J. D.

    1978-01-01

    A noncontacting sensor having a measurement range of 0 to 6 in or more, and with an accuracy of 0.5 in or better is needed to control the machinery used in modern coal mining so that the thickness of the coal layer remaining over the rock is maintained within selected bounds. The feasibility of using the radiofrequency resonance absorption (RRAS) techniques of electron magnetic resonance (EMR) and nuclear magnetic resonance (NMR) as the basis of a coal thickness gauge is discussed. The EMR technique was found, by analysis and experiments, to be well suited for this application.

  3. Negative refraction using Raman transitions and chirality

    SciTech Connect

    Sikes, D. E.; Yavuz, D. D.

    2011-11-15

    We present a scheme that achieves negative refraction with low absorption in far-off resonant atomic systems. The scheme utilizes Raman resonances and does not require the simultaneous presence of an electric-dipole transition and a magnetic-dipole transition near the same wavelength. We show that two interfering Raman tran-sitions coupled to a magnetic-dipole transition can achieve a negative index of refraction with low absorption through magnetoelectric cross-coupling. We confirm the validity of the analytical results with exact numerical simulations of the density matrix. We also discuss possible experimental implementations of the scheme in rare-earth metal atomic systems.

  4. Conformational states of N-acylalanine dithio esters: correlation of resonance Raman spectra with structures

    SciTech Connect

    Lee, H.; Angus, R.H.; Storer, A.C.; Varughese, K.I.; Carey, P.R.

    1988-01-12

    The conformational states of N-acylalanine dithio esters, involving rotational isomers about the RC(=O)NH-CH(CH/sub 3/) and NHCH(CH/sub 3/)-C(=S) bonds, are defined and compared to those of N-acylglycine dithio esters. The structure of N-(p-nitrobenzoyl)-DL-alanine ethyl dithio ester has been determined by X-ray crystallographic analysis; it is a B-type conformer with the amide N atom cis to the thiol sulfur. Raman and resonance Raman (RR) measurements on this compound and for the B conformers of solid N-benzoyl-DL-alanine ethyl dithio ester and N-(..beta..-phenylpropionyl)-DL-alanine ethyl dithio ester and its NHCH(CD/sub 3/)C(=S) and NHCH(CH/sub 3/)/sup 13/C(=S) analogues are used to set up a library of RR data for alanine-based dithio esters in a B-conformer state. RR data for this solid material in its isotopically unsubstituted and CH(C-D/sub 3/)C(=S) and CH(CH/sub 3/)/sup 13/C(=S) forms provide information on the RR signatures of alanine dithio esters in A-like conformations. RR spectra are compared for the solid compounds, for N-(p-nitrobenzoyl)-DL-alanine, N-(..beta..-phenylpropionyl)-DL-alanine, and (methyloxycarbonyl)-L-phenylalanyl-DL-alanine ethyl dithio ester, and for several /sup 13/C=S- and CD/sub 3/-substituted analogues in CCl/sub 4/ or aqueous solutions. The RR data demonstrate that the alanine-based dithio esters take up A, B, and C/sub 5/ conformations in solution. The RR spectra of these conformers are clearly distinguishable from those for the same conformers of N-acylglycine dithio esters. However, the crystallographic and spectroscopic results show that the results show that the conformational properties of N-acylglycine and N-acylalanine dithio esters are very similar.

  5. Soluble guanylate cyclase is activated differently by excess NO and by YC-1: Resonance Raman spectroscopic evidence†

    PubMed Central

    Ibrahim, Mohammed; Derbyshire, Emily R.; Soldatova, Alexandra V.; Marletta, Michael A.; Spiro, Thomas G.

    2010-01-01

    Modulation of soluble guanylate cyclase (sGC) activity by nitric oxide (NO) involves two distinct steps. Low level activation of sGC is achieved by the stoichiometric binding of NO (1-NO) to the heme cofactor, while much higher activation is achieved by the binding of additional NO (xsNO) at a non-heme site. Addition of the allosteric activator YC-1 to the 1-NO form leads to activity comparable to xsNO state. In this study the mechanisms of sGC activation were investigated using electronic absorption and resonance Raman (RR) spectroscopic methods. RR spectroscopy confirmed that the 1-NO form contains 5-coordinate NO-heme and showed that the addition of NO to the 1-NO form has no significant effect on the spectrum. In contrast, addition of YC-1 to either the 1-NO or xsNO forms alters the RR spectrum significantly, indicating a protein-induced change in the heme geometry. This change in the heme geometry was also observed when BAY 41-2272 was added to the xsNO form. Bands assigned to bending and stretching motions of the vinyl and propionate substituents change intensity in a pattern suggesting altered tilting of the pyrrole rings to which they are attached. In addition, the N-O stretching frequency increases, with no change in the Fe-NO frequency, an effect modeled via DFT calculations as resulting from a small opening of the Fe-N-O angle. These spectral differences demonstrate different mechanisms of activation by synthetic activators, such as YC-1 and BAY 41-2272, and excess NO. PMID:20459051

  6. Soluble guanylate cyclase is activated differently by excess NO and by YC-1: resonance Raman spectroscopic evidence.

    PubMed

    Ibrahim, Mohammed; Derbyshire, Emily R; Soldatova, Alexandra V; Marletta, Michael A; Spiro, Thomas G

    2010-06-15

    Modulation of soluble guanylate cyclase (sGC) activity by nitric oxide (NO) involves two distinct steps. Low-level activation of sGC is achieved by the stoichiometric binding of NO (1-NO) to the heme cofactor, while much higher activation is achieved by the binding of additional NO (xsNO) at a non-heme site. Addition of the allosteric activator YC-1 to the 1-NO form leads to activity comparable to that of the xsNO state. In this study, the mechanisms of sGC activation were investigated using electronic absorption and resonance Raman (RR) spectroscopic methods. RR spectroscopy confirmed that the 1-NO form contains five-coordinate NO-heme and showed that the addition of NO to the 1-NO form has no significant effect on the spectrum. In contrast, addition of YC-1 to either the 1-NO or xsNO forms alters the RR spectrum significantly, indicating a protein-induced change in the heme geometry. This change in the heme geometry was also observed when BAY 41-2272 was added to the xsNO form. Bands assigned to bending and stretching motions of the vinyl and propionate substituents undergo changes in intensity in a pattern suggesting altered tilting of the pyrrole rings to which they are attached. In addition, the N-O stretching frequency increases, with no change in the Fe-NO stretching frequency, an effect modeled via DFT calculations as resulting from a small opening of the Fe-N-O angle. These spectral differences demonstrate different mechanisms of activation by synthetic activators, such as YC-1 and BAY 41-2272, and excess NO. PMID:20459051

  7. Transient resonance Raman spectra of benzophenone and its four isotopic analogues in the lowest excited triplet state

    SciTech Connect

    Tahara, T.; Hamaguchi, H.; Tasumi, M.

    1987-11-05

    Transient resonance Raman spectra of T/sub 1/ benzophenone (T/sub 1/BP) and its four isotopic analogues in carbon tetrachloride solutions were measured. Vibrational assignments of eight T/sub 1/ bands have been made on the basis of the observed isotopic frequency shifts. The assignments clarified the following three points concerning the structure of T/sub 1/ BP in solution. (1) The CO bond order in T/sub 1/ BP is much lower than that in the ground-state benzophenone (S/sub 0/ BP). The CO stretching frequency in T/sub 1/ is found to be 1222 cm/sup -1/, whereas the corresponding value in S/sub 0/ is 1665 cm/sup -1/. The former frequency indicates a single-bond-like character of the CO bonding in the T/sub 1/ state. (2) Vibrational frequencies of several ring modes show marked downshifts in going from S/sub 0/ to T/sub 1/. This suggests the delocalization of the ..pi..* electron into the ring part. (3) The assignment (1302 cm/sup -1/) of the symmetric C-phenyl stretch mode in the T/sub 1/ withdraws S/sub 0/ absorption spectrum is questioned. According to the present assignment, the frequency of this mode (approx. 1100 cm/sup -1/) is slightly lower than that in the ground state (1150 cm/sup -1/). The simple quantum chemical picture of T/sub 1/ BP, which predicted the increase of the C-phenyl bond order with the ..pi..* withdraws n excitation, should therefore be reconsidered.

  8. Prototype explosives detection system based on nuclear resonance absorption in nitrogen

    SciTech Connect

    Morgado, R.E.; Arnone, G.; Cappiello, C.C.; Gardner, S.D.; Hollas, C.L.; Ussery, L.E.; White, J.M.; Zahrt, J.D.; Krauss, R.A.

    1993-12-01

    A-prototype explosives detection system that was developed for experimental evaluation of a nuclear resonance absorption techniques is described. The major subsystems are a proton accelerator and beam transport, high-temperature proton target, an airline-luggage tomographic inspection station, and an image-processing/detection- alarm subsystem. The detection system performance, based on a limited experimental test, is reported.

  9. Prototype explosives-detection system based on nuclear-resonance absorption in nitrogen

    SciTech Connect

    Morgado, R.E.; Arnone, G.; Cappiello, C.C.; Gardner, S.D.; Hollas, C.L.; Ussery, L.E.; White, J.M.; Zahrt, J.D.; Krauss, R.A.

    1994-06-01

    A prototype explosives-detection system (EDS) that was developed for experimental evaluation of a nuclear-resonance absorption technique is described. The major subsystems are a proton accelerator and beam transport, high-temperature proton target, an airline-luggage tomographic inspection station, and an image-processing/detection-alarm subsystem. The detection system performance, based on a limited experimental test, is reported.

  10. A magnetic-field enriched surface-enhanced resonance Raman spectroscopy strategy towards the early diagnosis of malaria

    NASA Astrophysics Data System (ADS)

    Yuen, Clement; Liu, Quan

    2012-03-01

    Early malaria diagnosis is important because malaria disease can develop into fatal illness within hours upon the appearance of the first symptom. The low concentration of the diagnosis biomarker, hemozoin, at the early stage of malaria disease makes early diagnosis difficult. In this paper, we present a magnetic field-enriched surface-enhanced resonance Raman spectroscopy (SERRS) strategy for the sensitive detection of β - hematin crystals, which is equivalent to hemozoin in the characteristics of Raman spectrum, by using magnetic nanoparticles. We observe several orders of magnitude enhancement in the SERRS signal of enriched β - hematin in comparison to the Raman signal of β - hematin in the cases of SERRS alone or magnetic enrichment alone, showing the great potential of this method towards early malaria diagnosis.

  11. A magnetic-field enriched surface-enhanced resonance Raman spectroscopy strategy towards the early diagnosis of malaria

    NASA Astrophysics Data System (ADS)

    Clement, Yuen; Liu, Quan

    2012-02-01

    Early malaria diagnosis is important because malaria disease can develop into fatal illness within hours upon the appearance of the first symptom. The low concentration of the diagnosis biomarker, hemozoin, at the early stage of malaria disease makes early diagnosis difficult. In this paper, we present a magnetic field-enriched surface-enhanced resonance Raman spectroscopy (SERRS) strategy for the sensitive detection of β - hematin crystals, which is equivalent to hemozoin in the characteristics of Raman spectrum, by using magnetic nanoparticles. We observe several orders of magnitude enhancement in the SERRS signal of enriched β - hematin in comparison to the Raman signal of β - hematin in the cases of SERRS alone or magnetic enrichment alone, showing the great potential of this method towards early malaria diagnosis.

  12. Silica-coated gold nanostars for surface-enhanced resonance Raman spectroscopy mapping of integrins in breast cancer cells

    NASA Astrophysics Data System (ADS)

    Fenn, Michael B.; Roki, Nikša.; Bashur, Chris

    2015-03-01

    Surface-Enhanced Resonance Raman Spectroscopy (SERRS) has great potential for improving cancer research and diagnosis. Capable of sub-femtomolar detection, and a high degree of multiplexing, SERRS is an attractive new technique for studying cancer biology. We have developed PEGylated silica-coated gold nanostars that can be tuned to match the Raman laser-light source wavelength, providing high-level SERRS/SERS enhancement when combined with various reporter molecules. Furthermore, the particles were conjugated with cyclo-RGDf/k peptide to investigate integrin expression of breast cancer cells using high-speed Raman mapping. We propose that this may provide a better understanding of the role of integrins in breast cancer invasiveness.

  13. Magnetic-dipolar-mode Fano resonances for microwave spectroscopy of high absorption matter

    NASA Astrophysics Data System (ADS)

    Vaisman, G.; Kamenetskii, E. O.; Shavit, R.

    2015-03-01

    The interaction between high absorption matter and microwave radiated energy is a subject of great importance. In particular, this concerns the microwave spectroscopic characterization of biological liquids. The use of effective testing methods to obtain information about physical properties of different liquids on the molecular level is one of the most important problems in biophysics. However, the standard methods based on microwave resonant techniques are not sufficiently suitable for biological liquids because the resonance peak in a resonator with high-loss liquids is so broad that the material parameters cannot be measured correctly. Although molecular vibrations of biomolecules may have microwave frequencies, it is not thought that such resonant coupling is significant due to their low energy compared with thermal energy and the strongly dampening aqueous environment. This paper presents an innovative microwave sensing technique for different types of lossy materials, including biological liquids. The technique is based on the combination of the microwave perturbation method and the Fano resonance effects observed recently in microwave structures with embedded magnetic-dipolar quantum dots. When the frequency of the magnetic dipolar mode (MDM) resonance is not equal to the cavity resonance frequency, one gets Fano transmission intensity. When the MDM resonance frequency is tuned to the cavity resonance frequency, by a bias magnetic field, one observes a Lorentzian line shape. Use of an extremely narrow Lorentzian peak allows exact probing of the resonant frequency of a cavity loaded by a highly lossy material sample. For different kinds of samples, one has different frequencies of Lorentzian peaks. This presents a picture of precise spectroscopic characterization of high absorption matter in microwaves.

  14. Temporal buildup of electromagnetically induced transparency and absorption resonances in degenerate two-level transitions

    NASA Astrophysics Data System (ADS)

    Valente, P.; Failache, H.; Lezama, A.

    2003-01-01

    The temporal evolution of electromagnetically induced transparency (EIT) and absorption (EIA) coherence resonances in pump-probe spectroscopy of degenerate two-level atomic transition is studied for light intensities below saturation. Analytical expressions for the transient absorption spectra are given for simple model systems and a model for the calculation of the time-dependent response of realistic atomic transitions, where the Zeeman degeneracy is fully accounted for, is presented. EIT and EIA resonances have a similar (opposite sign) time-dependent line shape, however, the EIA evolution is slower and thus narrower lines are observed for long interaction time. Qualitative agreement with the theoretical predictions is obtained for the transient probe absorption on the 85Rb D2 line in an atomic beam experiment.

  15. Separation of scattering and absorption contributions in UV/visible spectra of resonant systems.

    PubMed

    Micali, N; Mallamace, F; Castriciano, M; Romeo, A; Scolaro, L M

    2001-10-15

    Resonance light scattering (RLS) is a phenomenon due to an enhancement of the scattered light in close proximity to an absorption band. The effect is easily detectable in the case of strongly absorbing chromophores, which are able to interact, thus leading to large aggregates (Pasternack, R. F.; Collings, P. J. Science 1995, 269, 935). The measurement of absorption spectra from solutions containing such resonant systems can lead to misleading results. In this paper, a simple method is described to obtain absorption spectra of aggregated species with a fairly good correction of the scattering component. The RLS spectrum, obtained using a common spectrofluorimeter, is correlated to the extinction spectrum of the same sample, allowing for an estimation of the scattering contribution to the total extinction spectrum. The method has been successfully applied both on real samples containing aggregated chromophores, such as porphyrins, chlorophyll a and gold colloids, and by simulating extinction spectra.

  16. Resonance Raman imaging as a tool to assess the atmospheric pollution level: carotenoids in Lecanoraceae lichens as bioindicators.

    PubMed

    Ibarrondo, I; Prieto-Taboada, N; Martínez-Arkarazo, I; Madariaga, J M

    2016-04-01

    Raman spectroscopy differentiation of carotenoids has traditionally been based on the ν 1 position (C = C stretching vibrations in the polyene chain) in the 1500-1600 cm(-1) range, using a 785 nm excitation laser. However, when the number of conjugated double bonds is similar, as in the cases of zeaxanthin and β-carotene, this distinction is still ambiguous due to the closeness of the Raman bands. This work shows the Raman results, obtained in resonance conditions using a 514 mm laser, on Lecanora campestris and Lecanora atra species, which can be used to differentiate and consequently characterize carotenoids. The presence of the carotenoid found in Lecanoraceae lichens has been demonstrated to depend on the atmospheric pollution level of the environment they inhabit. Astaxanthin, a superb antioxidant, appears as the principal xanthophyll in highly polluted sites, usually together with the UV screening pigment scytonemin; zeaxanthin is the major carotenoid in medium polluted environments, while β-carotene is the major carotenoid in cleaner environments. Based on these observations, an indirect classification of the stress suffered in a given environment can be assessed by simply analysing the carotenoid content in the Lecanoraceae lichens by using resonance Raman imaging. PMID:26620863

  17. Plasmonic resonance absorption spectra in mid-infrared in an array of graphene nanoresonators

    NASA Astrophysics Data System (ADS)

    Abeysinghe, Don C.; Myers, Joshua; Nader Esfahani, Nima; Hendrickson, Joshua R.; Cleary, Justin W.; Walker, Dennis E.; Chen, Kuei-Hsien; Chen, Li-Chyong; Mou, Shin

    2013-12-01

    We experimentally demonstrated graphene plasmon resonant absorption in mid-IR by utilizing an array of graphene nanoribbon resonators on SiO2 substrate. By tuning resonator width we probed the graphene plasmons with λp <= λ0/100 and plasmon resonances as high as 0.240 eV (2100 cm-1) for 40 nm wide nanoresonators. Resonant absorption spectra revealed plasmon dispersion as well as plasmon damping due to the interaction of graphene plasmons with the surface polar phonons in SiO2 substrate and intrinsic graphene optical phonons. Graphene nanoribbons with varying widths enabled us to identify the damping mechanisms of graphene plasmons and much reduced damping was observed when the plasmon resonance frequencies were close to the substrate polar phonon frequencies. Then, by direct ebeam exposure of graphene nanoresonators, we effectively changed the carrier density and caused red-shift of the plasmon spectra. This work will provide insight into light-sensitive, frequency-tunable photodetectors based on graphene's plasmonic excitations.

  18. Quantum lattice fluctuations in a 1-dimensional charge-density-wave material: Luminescence and resonance Raman studies of an MX solid

    SciTech Connect

    Long, F.H.; Love, S.P.; Swanson, B.I.

    1993-01-01

    Luminescence spectra, both emission and excitation, and the excitation dependence of the resonance Raman (RR) spectra were measured for a 1-dimensional charge-density-wave solid, [Pt(L)[sub 2]Cl[sub 2

  19. Directly probing redox-linked quinones in photosystem II membrane fragments via UV resonance Raman scattering.

    PubMed

    Chen, Jun; Yao, Mingdong; Pagba, Cynthia V; Zheng, Yang; Fei, Liping; Feng, Zhaochi; Barry, Bridgette A

    2015-01-01

    In photosynthesis, photosystem II (PSII) harvests sunlight with bound pigments to oxidize water and reduce quinone to quinol, which serves as electron and proton mediators for solar-to-chemical energy conversion. At least two types of quinone cofactors in PSII are redox-linked: QA, and QB. Here, we for the first time apply 257-nm ultraviolet resonance Raman (UVRR) spectroscopy to acquire the molecular vibrations of plastoquinone (PQ) in PSII membranes. Owing to the resonance enhancement effect, the vibrational signal of PQ in PSII membranes is prominent. A strong band at 1661 cm(-1) is assigned to ring CC/CO symmetric stretch mode (ν8a mode) of PQ, and a weak band at 469 cm(-1) to ring stretch mode. By using a pump-probe difference UVRR method and a sample jet technique, the signals of QA and QB can be distinguished. A frequency difference of 1.4 cm(-1) in ν8a vibrational mode between QA and QB is observed, corresponding to ~86 mV redox potential difference imposed by their protein environment. In addition, there are other PQs in the PSII membranes. A negligible anharmonicity effect on their combination band at 2130 cm(-1) suggests that the 'other PQs' are situated in a hydrophobic environment. The detection of the 'other PQs' might be consistent with the view that another functional PQ cofactor (not QA or QB) exists in PSII. This UVRR approach will be useful to the study of quinone molecules in photosynthesis or other biological systems. PMID:25791219

  20. Directly probing redox-linked quinones in photosystem II membrane fragments via UV resonance Raman scattering.

    PubMed

    Chen, Jun; Yao, Mingdong; Pagba, Cynthia V; Zheng, Yang; Fei, Liping; Feng, Zhaochi; Barry, Bridgette A

    2015-01-01

    In photosynthesis, photosystem II (PSII) harvests sunlight with bound pigments to oxidize water and reduce quinone to quinol, which serves as electron and proton mediators for solar-to-chemical energy conversion. At least two types of quinone cofactors in PSII are redox-linked: QA, and QB. Here, we for the first time apply 257-nm ultraviolet resonance Raman (UVRR) spectroscopy to acquire the molecular vibrations of plastoquinone (PQ) in PSII membranes. Owing to the resonance enhancement effect, the vibrational signal of PQ in PSII membranes is prominent. A strong band at 1661 cm(-1) is assigned to ring CC/CO symmetric stretch mode (ν8a mode) of PQ, and a weak band at 469 cm(-1) to ring stretch mode. By using a pump-probe difference UVRR method and a sample jet technique, the signals of QA and QB can be distinguished. A frequency difference of 1.4 cm(-1) in ν8a vibrational mode between QA and QB is observed, corresponding to ~86 mV redox potential difference imposed by their protein environment. In addition, there are other PQs in the PSII membranes. A negligible anharmonicity effect on their combination band at 2130 cm(-1) suggests that the 'other PQs' are situated in a hydrophobic environment. The detection of the 'other PQs' might be consistent with the view that another functional PQ cofactor (not QA or QB) exists in PSII. This UVRR approach will be useful to the study of quinone molecules in photosynthesis or other biological systems.

  1. E{sub 1} Gap of Wurtzite InAs Single Nanowires Measured by Means of Resonant Raman Spectroscopy

    SciTech Connect

    Moeller, M.; Lima, M. M. Jr. de; Cantarero, A.; Dacal, L. C. O.; Iikawa, F.; Chiaramonte, T.; Cotta, M. A.

    2011-12-23

    Indium arsenide nanowires were synthesized with an intermixing of wurtzite and zincblende structure by chemical beam epitaxy with the vapor-liquid-solid mechanism. Resonant Raman spectroscopy of the transverse optical phonon mode at 215 cm{sup -1} reveals an E{sub 1} gap of 2.47 eV which is assigned to the electronic band gap at the A point in the indium arsenide wurtzite phase.

  2. Determination of chromophore structure and environment in bovine visual pigments with resonance Raman spectroscopy

    SciTech Connect

    Palings, H.A.

    1987-01-01

    Resonance Raman spectra of /sup 2/H- and /sup 13/C-labeled visual pigments have been obtained and analyzed. The C-C stretching vibrations of rhodopsin, isorhodopsin, and bathorhodopsin have been assigned, as well as those of the 11-cis and 9-cis retinal protonated Schiff base model compounds. The insensitivity of the C/sub 14/-C/sub 15/ stretch frequency to N-deuteration in all three pigments demonstrates that each contains a trans C=N bond. Comparison of the fingerprint modes of the visual pigments and their model compounds shows that the C/sub 10/-C/sub 11/ and C/sub 14/-C/sub 15/ single bonds are s-trans in all three pigments. This provides evidence against the model of bathorhodopsin proposed by Lui and Asato, which suggests a C/sub 10/-C/sub 11/ s-cis structure. The extreme similarity of the C-C stretch modes of rhodopsin and the 11-cis retinal protonated Schiff base argues against the presence of a negatively charged protein residue near C/sub 13/, proposed to be responsible for the opsin shift of rhodopsin. However, the unusually large shift of the C=N stretch frequency upon N-deuteration in rhodopsin relative to the model compound suggests that the opsin shift mechanism may involve altered Schiff base - counter ion interactions.

  3. Accurate Simulation of Resonance-Raman Spectra of Flexible Molecules: An Internal Coordinates Approach.

    PubMed

    Baiardi, Alberto; Bloino, Julien; Barone, Vincenzo

    2015-07-14

    The interpretation and analysis of experimental resonance-Raman (RR) spectra can be significantly facilitated by vibronic computations based on reliable quantum-mechanical (QM) methods. With the aim of improving the description of large and flexible molecules, our recent time-dependent formulation to compute vibrationally resolved electronic spectra, based on Cartesian coordinates, has been extended to support internal coordinates. A set of nonredundant delocalized coordinates is automatically generated from the molecular connectivity thanks to a new general and robust procedure. In order to validate our implementation, a series of molecules has been used as test cases. Among them, rigid systems show that normal modes based on Cartesian and delocalized internal coordinates provide equivalent results, but the latter set is much more convenient and reliable for systems characterized by strong geometric deformations associated with the electronic transition. The so-called Z-matrix internal coordinates, which perform well for chain molecules, are also shown to be poorly suited in the presence of cycles or nonstandard structures.

  4. An ultraviolet resonance Raman study of dehydrogenase enzymes and their interactions with coenzymes and substrates.

    PubMed

    Austin, J C; Wharton, C W; Hester, R E

    1989-02-21

    Ultraviolet resonance Raman (UVRR) spectra, with 260-nm excitation, are reported for oxidized and reduced nicotinamide adenine dinucleotides (NAD+ and NADH, respectively). Corresponding spectra are reported for these coenzymes when bound to the enzymes glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and liver and yeast alcohol dehydrogenases (LADH and YADH). The observed differences between the coenzyme spectra are interpreted in terms of conformation, hydrogen bonding, and general environment polarity differences between bound and free coenzymes and between coenzymes bound to different enzymes. The possibility of adenine protonation is discussed. UVRR spectra with 220-nm excitation also are reported for holo- and apo-GAPDH (GAPDH-NAD+ and GAPDH alone, respectively). In contrast with the 260-nm spectra, these show only bands due to vibrations of aromatic amino acid residues of the protein. The binding of coenzyme to GAPDH has no significant effect on the aromatic amino acid bands observed. This result is discussed in the light of the known structural change of GAPDH on binding coenzyme. Finally, UVRR spectra with 240-nm excitation are reported for GAPDH and an enzyme-substrate intermediate of GAPDH. Perturbations are reported for tyrosine and tryptophan bands on forming the acyl enzyme.

  5. Molecular effects of high-pressure processing on food studied by resonance Raman.

    PubMed

    Tintchev, Filip; Wackerbarth, Hainer; Kuhlmann, Uwe; Toepfl, Stefan; Knorr, Dietrich; Hildebrandt, Peter; Heinz, Volker

    2010-02-01

    Pressurization may cause unwanted side effects including color or texture changes of fish and meat. The color changes of poultry, pork, and smoked salmon were studied by CIE L*, a*, b* system, and resonance Raman (RR). High-pressure processing (HPP) of pork and chicken meat resulted in significant color modification at pressures higher than 270 and 280 MPa, respectively. RR spectra were taken after a high-pressure treatment of pork meat. According to the RR-data, deoxymyoglobin is the dominating myoglobin species in pork meat. High-pressure treatment causes conformational changes resulting in a stabile nonnative ferrous myoglobin species while the ferrous myoglobin state is maintained. High-pressure treatment causes a decrease of the relative RR intensities of astaxanthin by salmon as probed with 514 nm. RR spectra excited at 413 nm revealed a heterogeneous broadening of astaxanthin bands accompanied by the formation of deoxymyoglobin or deoxyhemoglobin. The broadening is interpreted as the degradation products of astaxanthin. Obviously, the high-pressure treatment of smoked salmon triggers redox processes of astaxanthin and the heme protein.

  6. Resonant raman scattering and dispersion of polar optical and acoustic phonons in hexagonal inn

    SciTech Connect

    Davydov, V. Yu. Klochikhin, A. A.; Smirnov, A. N.; Strashkova, I. Yu.; Krylov, A. S.; Lu Hai; Schaff, William J.; Lee, H.-M.; Hong, Y.-L.; Gwo, S.

    2010-02-15

    It is shown that a study of the dependence of impurity-related resonant first-order Raman scattering on the frequency of excitation light makes it possible to observe the dispersion of polar optical and acoustic branches of vibrational spectrum in hexagonal InN within a wide range of wave vectors. It is established that the wave vectors of excited phonons are uniquely related to the energy of excitation photon. Frequencies of longitudinal optical phonons E{sub 1}(LO) and A{sub 1}(LO) in hexagonal InN were measured in the range of excitation-photon energies from 2.81 to 1.17 eV and the frequencies of longitudinal acoustic phonons were measured in the range 2.81-1.83 eV of excitation-photon energies. The obtained dependences made it possible to extrapolate the dispersion of phonons A{sub 1}(LO) and E{sub 1}(LO) to as far as the point {Gamma} in the Brillouin zone and estimate the center-band energies of these phonons (these energies have not been uniquely determined so far).

  7. Redox State of Cytochromes in Frozen Yeast Cells Probed by Resonance Raman Spectroscopy.

    PubMed

    Okotrub, Konstantin A; Surovtsev, Nikolay V

    2015-12-01

    Cryopreservation is a well-established technique used for the long-term storage of biological materials whose biological activity is effectively stopped under low temperatures (suspended animation). Since most biological methods do not work in a low-temperature frozen environment, the mechanism and details of the depression of cellular activity in the frozen state remain largely uncharacterized. In this work, we propose, to our knowledge, a new approach to study the downregulation of the redox activity of cytochromes b and c in freezing yeast cells in a contactless, label-free manner. Our approach is based on cytochrome photobleaching effects observed in the resonance Raman spectra of live cells. Photoinduced and native redox reactions that contributed to the photobleaching rate were studied over a wide temperature range (from -173 to +25 °C). We found that ice formation influences both the rate of cytochrome redox reactions and the balance between the reduced and oxidized cytochromes. We demonstrate that the temperature dependence of native redox reaction rates can be well described by the thermal activation law with an apparent energy of 32.5 kJ/mol, showing that the redox reaction rate is ∼10(15) times slower at liquid nitrogen temperature than at room temperature.

  8. Redox State of Cytochromes in Frozen Yeast Cells Probed by Resonance Raman Spectroscopy.

    PubMed

    Okotrub, Konstantin A; Surovtsev, Nikolay V

    2015-12-01

    Cryopreservation is a well-established technique used for the long-term storage of biological materials whose biological activity is effectively stopped under low temperatures (suspended animation). Since most biological methods do not work in a low-temperature frozen environment, the mechanism and details of the depression of cellular activity in the frozen state remain largely uncharacterized. In this work, we propose, to our knowledge, a new approach to study the downregulation of the redox activity of cytochromes b and c in freezing yeast cells in a contactless, label-free manner. Our approach is based on cytochrome photobleaching effects observed in the resonance Raman spectra of live cells. Photoinduced and native redox reactions that contributed to the photobleaching rate were studied over a wide temperature range (from -173 to +25 °C). We found that ice formation influences both the rate of cytochrome redox reactions and the balance between the reduced and oxidized cytochromes. We demonstrate that the temperature dependence of native redox reaction rates can be well described by the thermal activation law with an apparent energy of 32.5 kJ/mol, showing that the redox reaction rate is ∼10(15) times slower at liquid nitrogen temperature than at room temperature. PMID:26636934

  9. Two-dimensional resonance Raman spectroscopy of oxygen- and water-ligated myoglobins

    NASA Astrophysics Data System (ADS)

    Molesky, Brian P.; Guo, Zhenkun; Cheshire, Thomas P.; Moran, Andrew M.

    2016-07-01

    Two-dimensional resonance Raman (2DRR) spectroscopy has recently been developed as a tool for studies of structural heterogeneity and photochemical dynamics in condensed phases. In this paper, 2DRR spectroscopy is used to investigate line broadening mechanisms of both oxygen- and water-ligated myoglobins. General signatures of anharmonicity and inhomogeneous line broadening are first established with model calculations to facilitate signal interpretation. It is shown that the present quasi-degenerate version of 2DRR spectroscopy is insensitive to anharmonicity, because signal generation is allowed for harmonic modes. Rather, the key information to be gained from 2DRR spectroscopy pertains to the line broadening mechanisms, which are fairly obvious by inspection of the data. 2DRR signals acquired for both heme protein systems reveal significant heterogeneity in the vibrational modes local to the heme's propionic acid side chains. These side chains are known to interact with solvent, because they protrude from the hydrophobic pocket that encloses the heme. Molecular dynamics simulations suggest that the heterogeneity detected in our 2DRR experiments reflects fluctuations in the geometries of the side chains. Knowledge of such thermal motions will be useful for understanding protein function (e.g., ligand binding) because the side chains are an effective "gateway" for the exchange of thermal energy between the heme and solvent.

  10. Tryptophan as a probe of photosystem I electron transfer reactions: a UV resonance Raman study.

    PubMed

    Chen, Jun; Bender, Shana L; Keough, James M; Barry, Bridgette A

    2009-08-20

    Photosystem I (PSI) is one of the two membrane-associated reaction centers involved in oxygenic photosynthesis. In photosynthesis, solar energy is converted to chemical energy in the form of a transmembrane charge separation. PSI oxidizes cytochrome c(6) or plastocyanin and reduces ferredoxin. In cyanobacterial PSI, there are 10 tryptophan residues with indole side chains located less than 10 A from the electron transfer cofactors. In this study, we apply pump-probe difference UV resonance Raman (UVRR) spectroscopy to acquire the spectrum of aromatic amino acids in cyanobacterial PSI. This UVRR technique allows the use of the tryptophan vibrational spectrum as a reporter for structural changes, which are linked to PSI electron transfer reactions. Our results show that photo-oxidation of the chlorophyll a/a' heterodimer, P(700), causes shifts in the vibrational frequencies of two or more tryptophan residues. Similar perturbations of tryptophan are observed when P(700) is chemically oxidized. The observed spectral frequencies suggest that the perturbed tryptophan side chains are only weakly or not hydrogen bonded and are located in an environment in which there is steric repulsion. The direction of the spectral shifts is consistent with an oxidation-induced increase in dielectric constant or a change in hydrogen bonding. To explain our results, the perturbation of tryptophan residues must be linked to a PSI conformational change, which is, in turn, driven by P(700) oxidation.

  11. 13C Solid State Nuclear Magnetic Resonance and µ-Raman Spectroscopic Characterization of Sicilian Amber.

    PubMed

    Barone, Germana; Capitani, Donatella; Mazzoleni, Paolo; Proietti, Noemi; Raneri, Simona; Longobardo, Ugo; Di Tullio, Valeria

    2016-08-01

    (13)C cross-polarization magic angle spinning (CPMAS) nuclear magnetic resonance (NMR) and µ-Raman spectroscopy were applied to characterize Sicilian amber samples. The main goal of this work was to supply a complete study of simetite, highlighting discriminating criteria useful to distinguish Sicilian amber from fossil resins from other regions and laying the foundations for building a spectroscopic database of Sicilian amber. With this aim, a private collection of unrefined simetite samples and fossil resins from the Baltic region and Dominican Republic was analyzed. Overall, the obtained spectra permitted simetite to be distinguished from the other resins. In addition, principal component analysis (PCA) was applied to the spectroscopic data, allowing the clustering of simetite samples with respect to the Baltic and Dominican samples and to group the simetite samples in two sets, depending on their maturity. Finally, the analysis of loadings allowed for a better understanding of the spectral features that mainly influenced the discriminating characteristics of the investigated ambers. PMID:27340217

  12. Resonance Raman studies of the HOOP modes in octopus bathorhodopsin with deuterium-labeled retinal chromophores

    SciTech Connect

    Deng, H.; Manor, D.; Weng, G.; Rath, P.; Callender, R.H. ); Koutalos, Y.; Ebrey, T. ); Gebhard, R.; Lugtenburg, J. ); Tsuda, M. )

    1991-05-07

    Resonance Raman spectra of the hydrogen out-of-plane (HOOP) vibrational modes in the retinal chromophore of octopus bathorhodopsin with deuterium label(s) along the polyene chain have been obtained. In clear contrast with bovine bathorhodopsin's HOOP modes, there are only two major HOOP bands at 887 and 940 cm{sup {minus}1} for octopus bathorhodopsin. On the basis of their isotopic shifts upon deuterium labeling, the authors have assigned the band at 887 cm{sup {minus}1} to C{sub 10}H and C{sub 14}H HOOP modes, and the band at 940 cm{sup {minus}1} to C{sub 11}H{double bond}C{sub 12}H A{sub u}-like HOOP mode. They found also that the C{sub 10}H and C{sub 14}H HOOP wags are also similar to those in the model-compound studies. However, they have found that the interaction between the C{sub 7}H and C{sub 8}H HOOP internal coordinates of the chromophore in octopus bathorhodopsin is different from that of the chromophore in solution. The twisted nature of the chromophore, semiquantitatively discussed here, likely affects the {lambda}{sub max} of the chromophore and its enthalpy. The nature of the HOOP modes of octopus bathorhodopsin differs substantially from those found in bovine bathorhodopsin.

  13. Far-red resonance Raman study of copper A in subunit II of cytochrome c oxidase

    SciTech Connect

    Wallace-Williams, S.E.; James, C.A.; Woodruff, W.H.; Vries, S. de; Saraste, M.; Lappalainen, P.; Oost, J. van der; Fabian, M.; Palmer, G.

    1996-04-24

    The present work employs far-red resonance Raman spectroscopy (RR) to investigate whether a Cu-Cu bonding interaction exists in Cu{sub A}. The electronic transition of Cu{sub A} near 830 nm provides the opportunity for specific RR observation of the vibrations of this chromophore. We have employed RR with Cu isotopic substitution on genetically modified, solubilized forms of CcO subunit II from Bacillus subtilis and Paracoccus denitrificans. We have also probed the Cu{sub A} site of native beef heart CcO for comparison. The similarity of the CcO and Cu{sub A} fragment (subunit II) spectra suggests that Cu{sub A} in the isolated subunit II has essentially the same structure as that of Cu{sub A} in intact CcO. Thus, the suggested Cu-Cu bonding in Cu{sub A}, if correct, applies both to the isolated subunit II and native CcO. The functional reasons why nature may choose such a structure, or in fact why a two-copper center of any sort is constructed to perform a function which is commonly believed to be simple one-electron transfer, are unclear. 34 refs., 1 fig., 1 tab.

  14. Fano resonance of Li-doped KTa1−xNbxO3 single crystals studied by Raman scattering

    PubMed Central

    Rahaman, M. M.; Imai, T.; Sakamoto, T.; Tsukada, S.; Kojima, S.

    2016-01-01

    The enhancement of functionality of perovskite ferroelectrics by local structure is one of current interests. By the Li-doping to KTa1−xNbxO3 (KTN), the large piezoelectric and electro-optic effects were reported. In order to give new insights into the mechanism of doping, the microscopic origin of the Fano resonance induced by the local structure was investigated in 5%Li-doped KTN single crystals by Raman scattering. The coupling between the continuum states and the transverse optical phonon near 196 cm−1 (Slater mode) caused a Fano resonance. In the vicinity of the cubic-tetragonal phase transition temperature, TC-T = 31 °C, the almost disappearance of the Fano resonance and the remarkable change of the central peak (CP) intensity were observed upon heating. The local symmetry of the polar nanoregions (PNRs), which was responsible for the symmetry breaking in the cubic phase, was determined to E(x, y) symmetry by the angular dependence of Raman scattering. The electric field induced the significant change in the intensity of both CP and Fano resonance. From these experimental results, it is concluded that the origin of the Fano resonance in Li-doped KTN crystals is the coupling between polarization fluctuations of PNRs and the Slater mode, both belong to the E(x, y) symmetry. PMID:27049847

  15. Fano resonance of Li-doped KTa(1-x)NbxO3 single crystals studied by Raman scattering.

    PubMed

    Rahaman, M M; Imai, T; Sakamoto, T; Tsukada, S; Kojima, S

    2016-01-01

    The enhancement of functionality of perovskite ferroelectrics by local structure is one of current interests. By the Li-doping to KTa(1-x)NbxO3 (KTN), the large piezoelectric and electro-optic effects were reported. In order to give new insights into the mechanism of doping, the microscopic origin of the Fano resonance induced by the local structure was investigated in 5%Li-doped KTN single crystals by Raman scattering. The coupling between the continuum states and the transverse optical phonon near 196 cm(-1) (Slater mode) caused a Fano resonance. In the vicinity of the cubic-tetragonal phase transition temperature, TC-T = 31 °C, the almost disappearance of the Fano resonance and the remarkable change of the central peak (CP) intensity were observed upon heating. The local symmetry of the polar nanoregions (PNRs), which was responsible for the symmetry breaking in the cubic phase, was determined to E(x, y) symmetry by the angular dependence of Raman scattering. The electric field induced the significant change in the intensity of both CP and Fano resonance. From these experimental results, it is concluded that the origin of the Fano resonance in Li-doped KTN crystals is the coupling between polarization fluctuations of PNRs and the Slater mode, both belong to the E(x, y) symmetry. PMID:27049847

  16. Transmission Loss and Absorption of Corrugated Core Sandwich Panels With Embedded Resonators

    NASA Technical Reports Server (NTRS)

    Allen, Albert R.; Schiller, Noah H.; Zalewski, Bart F.; Rosenthal, Bruce N.

    2014-01-01

    The effect of embedded resonators on the diffuse field sound transmission loss and absorption of composite corrugated core sandwich panels has been evaluated experimentally. Two 1.219 m × 2.438 m panels with embedded resonator arrangements targeting frequencies near 100 Hz were evaluated using non-standard processing of ASTM E90-09 acoustic transmission loss and ASTM C423-09a room absorption test measurements. Each panel is comprised of two composite face sheets sandwiching a corrugated core with a trapezoidal cross section. When inlet openings are introduced in one face sheet, the chambers within the core can be used as embedded acoustic resonators. Changes to the inlet and chamber partition locations allow this type of structure to be tuned for targeted spectrum passive noise control. Because the core chambers are aligned with the plane of the panel, the resonators can be tuned for low frequencies without compromising the sandwich panel construction, which is typically sized to meet static load requirements. Absorption and transmission loss performance improvements attributed to opening the inlets were apparent for some configurations and inconclusive for others.

  17. Theoretical study of Raman chirped adiabatic passage by X-ray absorption spectroscopy: Highly excited electronic states and rotational effects

    SciTech Connect

    Engin, Selma; Sisourat, Nicolas Selles, Patricia; Taïeb, Richard; Carniato, Stéphane

    2014-06-21

    Raman Chirped Adiabatic Passage (RCAP) is an efficient method to climb the vibrational ladder of molecules. It was shown on the example of fixed-in-space HCl molecule that selective vibrational excitation can thus be achieved by RCAP and that population transfer can be followed by X-ray Photoelectron spectroscopy [S. Engin, N. Sisourat, P. Selles, R. Taïeb, and S. Carniato, Chem. Phys. Lett. 535, 192–195 (2012)]. Here, in a more detailed analysis of the process, we investigate the effects of highly excited electronic states and of molecular rotation on the efficiency of RCAP. Furthermore, we propose an alternative spectroscopic way to monitor the transfer by means of X-ray absorption spectra.

  18. Auger resonant Raman spectroscopy used to study the angular distributions of the Xe 4d{sub 5/2} {yields} 6p decay spectrum

    SciTech Connect

    Langer, B.; Berrah, N.; Farhat, A.

    1997-04-01

    Auger resonant Raman spectroscopy is a powerful tool for studying the resonant Auger decay processes with a resolution narrower than the natural lifetime width of the initial inner-shell hole state. This effect has been used to analyze branching ratios of resonantly excited atoms and molecules. In this paper, the authors present results of a study of angular distributions of the spectator decay lines of Xe following 4d{sub 5/2}{r_arrow}6p excitation using the Auger resonant Raman effect and highly resolved photons from the Advanced Light Source (ALS).

  19. Electron paramagnetic resonance and low-field microwave absorption in the manganese-gallium oxide

    NASA Astrophysics Data System (ADS)

    Montiel, H.; Alvarez, G.; Conde-Gallardo, A.; Zamorano, R.

    2015-07-01

    Microwave absorption measurements in MnGa2O4 powders are carried out at X-band (8.8-9.8 GHz) in 92-296 K temperature range. For all temperatures, the electron paramagnetic resonance (EPR) spectra show a single broad line due to Mn2+ ions. Temperature dependence of the EPR parameters: the peak-to-peak linewidth (ΔHpp), the integrated intensity (IEPR) and the g-factor, suggests the presence of magnetic fluctuations that precede to antiferromagnetic ordering at low temperature. Additionally, the low-field microwave absorption (LFMA) is used to give further information on this material, giving also evidence of these magnetic fluctuations.

  20. Absorption cross sections of some atmospheric molecules for resonantly scattered O I 1304-A radiation

    NASA Technical Reports Server (NTRS)

    Starr, W. L.

    1976-01-01

    Absorption cross sections for O2, N2, CO2, CH4, N2O, and CO have been measured at each of the lines of the atomic oxygen triplet at 1302, 1305, and 1306 A. Radiation resonantly scattered from oxygen atoms at a temperature of about 300 K was used for the line source. Absorber temperatures were also near 300 K. Direct application of the Lambert-Beer absorption equation yielded pressure-dependent cross sections for carbon monoxide at each line of the O I triplet. Reasons for this apparent dependence are presented and discussed.

  1. Effect of TiO2 particles on normal and resonance Raman spectra of coumarin 343: a theoretical investigation.

    PubMed

    Yang, Linzhi; Wu, Wenpeng; Zhao, Yi

    2015-04-28

    It is well known that interfacial structures and charge transfer in dye-sensitized solar cells are extremely important for the enhancement of cell efficiency. Here, the normal Raman spectra (NRS) and resonance Raman spectra (RRS) of a C343-sensitized TiO2 cluster (Ti9O18) are theoretically predicted from combined electronic structure calculations and a vibrationally-resolved spectral method to reveal the relationship between interfacial geometries and excited-state dynamics. The results show that although the NRS of free C343 and the C343-TiO2 cluster correspond to the vibrational motions of C343 in a high frequency domain, their mode frequencies show obvious differences due to the interaction of the TiO2 cluster on C343, and several new Raman active fingerprint modes, such as bidentate chelating bonding modes, can be used to determine interfacial geometries. However, the resonance Raman activities of low-frequency modes are significantly enhanced and several modes from the TiO2 cluster can be observed, consistent with experimental measurements. Furthermore, the RRS from a locally excited state and a charge transfer state of C343-TiO2 are dramatically different, for instance, new Raman active modes with 1212 cm(-1), 1560 cm(-1) and 1602 cm(-1), corresponding to the motions of CH2 rocking, C=C/C-N/C=O stretching and C=O/C=C stretching, appear from the charge transfer state. The obtained information on mode-specific reorganization energies from these excited states is greatly helpful to understand and control interfacial electron transfer.

  2. Ultrafast photo-induced nuclear relaxation of a conformationally disordered conjugated polymer probed with transient absorption and femtosecond stimulated Raman spectroscopies

    SciTech Connect

    Yu, Wenjian; Donohoo-Vallett, Paul J.; Zhou, Jiawang; Bragg, Arthur E.

    2014-07-28

    A combination of transient absorption (TAS) and femtosecond stimulated Raman (FSRS) spectroscopies were used to interrogate the photo-induced nuclear relaxation dynamics of poly(3-cyclohexyl,4-methylthiophene) (PCMT). The large difference in inter-ring dihedral angles of ground and excited-state PCMT make it an ideal candidate for studying large-amplitude vibrational relaxation associated with exciton trapping. Spectral shifting in the S{sub 1} TA spectra on sub-ps timescales (110 ± 20 and 800 ± 100 fs) is similar to spectroscopic signatures of excited-state relaxation observed with related photoexcited conjugated polymers and which have been attributed to exciton localization and a combination of resonant energy transfer and torsional relaxation, respectively. Measurements made with both techniques reveal fast PCMT S{sub 1} decay and triplet formation (τ{sub S1} = 25–32 ps), which is similar to the excited-state dynamics of short oligothiophenes and highly twisted polyconjugated molecules. On ultrafast timescales FSRS of S{sub 1} PCMT offers a new perspective on the nuclear dynamics that underlie localization of excitons in photoexcited conjugated polymers: Spectral dynamics in the C=C stretching region (1400–1600 cm{sup −1}) include a red-shift of the in-phase C=C stretching frequency, as well as a change in the relative intensity of in-phase and out-of-phase stretch intensities on a timescale of ∼100 fs. Both changes indicate an ultrafast vibrational distortion that increases the conjugation length in the region of the localized excitation and are consistent with exciton self-localization or trapping. Wavelength-dependent excited-state FSRS measurements further demonstrate that the C=C stretching frequency provides a useful spectroscopic handle for interrogating the degree of delocalization in excited conjugated polymers given the selectivity achieved via resonance enhancement.

  3. Signs of the Biological Effect of ~2 μm Low-Intensity Laser Radiation in Raman and Absorption Spectra of Blood

    NASA Astrophysics Data System (ADS)

    Batay, L. E.; Khodasevich, I. A.; Khodasevich, M. A.; Gorbunova, N. B.; Manina, E. Yu.

    2016-09-01

    Local exposure of experimental animals to low-intensity emission from a thulium laser (λ = 1.96 μm) leads to changes in the Raman and IR absorption spectra of blood. This indicates development of systemic effects caused by direct excitation of water molecules by radiation with wavelength ~2 μm, in particular modifi cation of the hemoglobin molecule.

  4. Infrared, Raman, resonance Raman spectra and lattice dynamics calculations of the solid potassium(I) nickel(II) thiophosphate compound, KNiPS 4

    NASA Astrophysics Data System (ADS)

    Sourisseau, C.; Cavagnat, R.; Fouassier, M.; Brec, R.; Elder, S. H.

    1995-06-01

    The UV-visible (350-850 nm), infrared and Raman (20-700 cm -1) spectra of a new KNiPS 4 solid compound have been analyzed using powder samples and crystalline platelets. From polarization measurements, the main electronic transition of 1F 2← 1A 1 type due to the PS 43- thiophosphate groups are localized in the 360-570 nm range and vibrational assignments for most of the fundamental modes are proposed. These assignments were checked by complete valence force field lattice dynamics calculations in the various symmetry blocks of the tetragonal crystal structure (D 4h14). Potential energy distributions as well as mean squared vibrational amplitude calculations have shown strong ν(NiS) and σ(SPS) couplings in the (NiPS 4) - structural chains and remarkably high ν(NiS) infrared frequencies. Furthermore, the resonance Raman spectra of single crystals and powder samples were recorded over a wide range (647.1-476.5 nm) of excitatiob wavelengths. This allowed to probe the nature of the broad electronic transition of the complex centered around 510 nm and responsible for KNiPS 4 brown color. The Raman excitation profiles of several fundamentals and combination bands were thus established. Under resonance conditions, various crystalline components of A 1g, B 1g and B 2g symmetry for the ν 4(F 2) or ν 2(E) deformation modes of the PS 43- groups are enhanced. No overtone progressions involving totally symmetric modes were observed but anomalously intense high-order combination bands were detected. It is thus concluded that adiabatic as well as non-adiabatic interactions must play a great role in the vibronically induced Raman scattering processes. Reasons for this peculiar behavior are discussed in relation to the X-ray crystal structure of the KNiPS 4 compound. All the experimental results imply the presence of substantial site and factor group effects on the optical and vibronic properties of the thiophosphate anions.

  5. Multiple-overtone resonance Raman scattering and fluorescence from I{sub 2} species adsorbed on silver surfaces

    SciTech Connect

    Sibbald, M.S.; Chumanov, G.; Small, G.; Cotton, T.M.

    1998-07-01

    A detailed excitation profile of a Raman progression consisting of up to six overtones and a fundamental band at 123 cm{sup {minus}1} observed from iodide adsorbed on an electrochemically roughened silver surface at 20 K is analyzed. The excitation profile was constructed from 77 spectra obtained by tuning the laser wavelength in {approximately}0.25 nm steps through the spectral range 409 nm{endash}433 nm. The shift between resonances in the excitation profile, corresponding to the spacing between vibronic levels in the excited state, is also equal to 123 cm{sup {minus}1} indicating that the ground state and excited state potential energy surfaces have the same shape. Only two distinct resonances spaced three vibrational quanta apart were evident in the profile for each band in the progression. Curve fitting of the Raman band shapes indicates that each overtone is composed of one sharp and one broad band, whereas the fundamental contains only one sharp component. The measured width of the fundamental was less than 2.5 cm{sup {minus}1} FWHM, limited by the instrument function. It is proposed that the sharp Raman bands represent a normal vibrational mode of a surface-adsorbed I{sub 2}-like species with the width determined by the intrinsic vibrational dephasing in the ground state. On the other hand, the broad Raman bands reflect vibronic coupling between different I{sub 2}-like species adsorbed on the same Ag cluster. The broad bandwidths result from both dephasing associated with the vibronic coupling and the intrinsic vibrational dephasing. Other weak emission bands are attributed to resonance fluorescence corresponding to direct transitions from higher vibronic levels of the excited state to the ground state. An emission at 429.9 nm is assigned to exciton recombination in small silver iodide clusters which are formed after spontaneous oxidation of the iodide-modified silver surface. {copyright} {ital 1998 American Institute of Physics.}

  6. Raman Spectroscopy.

    ERIC Educational Resources Information Center

    Gerrard, Donald L.

    1984-01-01

    Reviews literature on Raman spectroscopy from late 1981 to late 1983. Topic areas include: instrumentation and sampling; liquids and solutions; gases and matrix isolation; biological molecules; polymers; high-temperature and high-pressure studies; Raman microscopy; thin films and surfaces; resonance-enhanced and surface-enhanced spectroscopy; and…

  7. Prototype explosives detection system based on nuclear resonance absorption in nitrogen

    SciTech Connect

    Morgado, R.E.; Arnone, G.J.; Cappiello, C.C.

    1996-05-01

    A laboratory prototype system has been developed for the experimental evaluation of an explosives detection technique based on nuclear resonance absorption of gamma rays in nitrogen. Major subsystems include a radiofrequency quadrupole proton accelerator and associated beam transport system, a high-power gamma-ray production target, an airline-luggage tomographic inspection system, and an image- processing/detection-alarm subsystem. The detection system performance, based on a limited experimental test, is reported.

  8. Resonance lamp absorption measurement of OH number density and temperature in expansion tube scramjet engine tests

    NASA Technical Reports Server (NTRS)

    Lempert, Walter R.; Trucco, Richard E.; Bittner, Robert D.

    1992-01-01

    In this paper, we report results of hydroxyl radical and static temperature measurements performed in the General Applied Science Laboratories-NASA HYPULSE expansion tube facility using the microwave resonance lamp absorption technique. Data were obtained as part of a series of hydrogen/air and hydrogen/oxygen combustion tests at stagnation enthalpies corresponding to Mach 17 flight speeds. Data from a representative injector configuration is compared to a full Navier-Stokes CFD solution.

  9. Electronic-resonance-enhanced coherent anti-Stokes Raman scattering of nitric oxide: Saturation and Stark effects

    NASA Astrophysics Data System (ADS)

    Chai, Ning; Lucht, Robert P.; Kulatilaka, Waruna D.; Roy, Sukesh; Gord, James R.

    2010-08-01

    A theoretical analysis of electronic-resonance-enhanced (ERE) coherent anti-Stokes Raman scattering (CARS) of NO is described. The time-dependent density-matrix equations for the nonlinear ERE-CARS process are derived and manipulated into a form suitable for direct numerical integration. In the ERE-CARS configuration considered in this paper, the pump and Stokes beams are far from electronic-resonance. The visible 532 and 591 nm laser beams are used to excite Q-branch Raman resonances in the vibrational bands of the X Π2 electronic state of NO. An ultraviolet probe beam at 236 nm is used to excite P-, Q-, or R-branch transitions in the (v '=0, v″=1) band of the A Σ2+-X Π2 electronic system of NO molecule. Experimental spectra are obtained either by scanning the ultraviolet probe beam while keeping the Stokes frequency fixed (probe scans) or by scanning the Stokes frequency while keeping the probe frequency fixed (Stokes scans). The calculated NO ERE-CARS spectra are compared with experimental spectra, and good agreement is observed between theory and experiment in terms of spectral peak locations and relative intensities. The effects of saturation of the two-photon Raman-resonant Q-branch transitions, the saturation of a one-photon electronic-resonant P-, Q-, or R-branch transitions in the A Σ2+-X Π2 electronic system, and the coupling of these saturation processes are investigated. The coupling of the saturation processes for the probe and Raman transitions is complex and exhibits behavior similar to that observed in the electromagnetic induced transparency process. The probe scan spectra are significantly affected by Stark broadening due to the interaction of the pump and Stokes radiation with single-photon resonances between the upper vibration-rotation probe level in the A Σ2+ electronic levels and vibration-rotation levels in higher lying electronic levels. The ERE-CARS signal intensity is found to be much less sensitive to variations in the

  10. Effects of dispersion and absorption in resonant Bragg diffraction of x-rays.

    PubMed

    Lovesey, S W; Scagnoli, V; Dobrynin, A N; Joly, Y; Collins, S P

    2014-03-26

    Resonant diffraction of x-rays by crystals with anisotropic optical properties is investigated theoretically, to assess how the intensity of a Bragg spot is influenced by effects related to dispersion (birefringence) and absorption (dichroism). Starting from an exact but opaque expression, simple analytic results are found to expose how intensity depends on dispersion and absorption in the primary and secondary beams and, also, the azimuthal angle (rotation of the crystal about the Bragg wavevector). If not the full story for a given application, our results are more than adequate to explore consequences of dispersion and absorption in the intensity of a Bragg spot. Results are evaluated for antiferromagnetic copper oxide, and low quartz. For CuO, one of our results reproduces all salient features of a previously published simulation of the azimuthal-angle dependence of a magnetic Bragg peak. It is transparent in our analytic result that dispersion and absorption effects alone cannot reproduce published experimental data. Available data for the azimuthal-angle dependence of space-group forbidden reflections (0,0, l), with l ≠ 3n, of low quartz depart from symmetry imposed by the triad axis of rotation symmetry. The observed asymmetry can be induced by dispersion and absorption even though absorption coefficients are constant, independent of the azimuthal angle, in this class of reflections.

  11. Effects of dispersion and absorption in resonant Bragg diffraction of x-rays.

    PubMed

    Lovesey, S W; Scagnoli, V; Dobrynin, A N; Joly, Y; Collins, S P

    2014-03-26

    Resonant diffraction of x-rays by crystals with anisotropic optical properties is investigated theoretically, to assess how the intensity of a Bragg spot is influenced by effects related to dispersion (birefringence) and absorption (dichroism). Starting from an exact but opaque expression, simple analytic results are found to expose how intensity depends on dispersion and absorption in the primary and secondary beams and, also, the azimuthal angle (rotation of the crystal about the Bragg wavevector). If not the full story for a given application, our results are more than adequate to explore consequences of dispersion and absorption in the intensity of a Bragg spot. Results are evaluated for antiferromagnetic copper oxide, and low quartz. For CuO, one of our results reproduces all salient features of a previously published simulation of the azimuthal-angle dependence of a magnetic Bragg peak. It is transparent in our analytic result that dispersion and absorption effects alone cannot reproduce published experimental data. Available data for the azimuthal-angle dependence of space-group forbidden reflections (0,0, l), with l ≠ 3n, of low quartz depart from symmetry imposed by the triad axis of rotation symmetry. The observed asymmetry can be induced by dispersion and absorption even though absorption coefficients are constant, independent of the azimuthal angle, in this class of reflections. PMID:24599265

  12. Chirality Distribution Measurements of the NIST Single-Wall Carbon Nanotube Reference Material Using Resonance Raman Spectroscopy

    NASA Astrophysics Data System (ADS)

    Mead, Kevin; Simpson, Jeff; Scheel, Logan; Fagan, Jeff; Hightwalker, Angela

    2013-03-01

    The ability to rapidly and easily determine the chiral vector distribution within a nanotube population remains a key measurement need for carbon nanotube processing and applications. We report Resonance Raman Spectroscopy (RRS) measurements of a SWCNT reference material from NIST. The SWCNT samples were synthesized using the CoMoCat method, dispersed in aqueous solutions by wrapping in deoxycholate surfactant, and separated by length using ultracentrifugation. We measure Raman spectra over a wide range of excitation wavelengths from 457 nm to 850 nm using a series of discrete and continuously tunable laser sources coupled to a triple-grating spectrometer with a liquid-nitrogen-cooled detector. The spectra reveal Raman-active vibrational modes including the low-frequency radial breathing mode and higher-order modes. Chirality distributions are determined from the Raman spectra, specifically the RBM frequency and energy excitation profiles, together with input from theoretical models. RRS is sensitive to both major and minor chiral species in the sample. We will compare the resulting chirality distribution obtained from RRS with those obtained from other orthogonal measurement techniques.

  13. Chirality Distribution Measurements of the NIST Single-Wall Carbon Nanotube Reference Material Using Resonance Raman Spectroscopy

    NASA Astrophysics Data System (ADS)

    Scheel, L. F.; Simpson, J. R.; Fagan, J. A.; Hight Walker, A. R.

    2012-02-01

    The ability to rapidly and easily determine the chiral vector distribution within a nanotube population remains a key measurement need for carbon nanotube processing and applications. We report Resonance Raman Spectroscopy (RRS) measurements of a SWCNT reference material from NIST. The SWCNT samples were synthesized using the CoMoCat method, dispersed in aqueous solutions by wrapping in deoxycholate surfactant, and separated by length using ultracentrifugation. We measure Raman spectra over a wide range of excitation wavelengths from 457 nm to 850 nm using a series of discrete and continuously tunable laser sources coupled to a triple-grating spectrometer with a liquid-nitrogen-cooled detector. The spectra reveal Raman-active vibrational modes including the low-frequency radial breathing mode and higher-order modes. Chirality distributions are determined from the Raman spectra, specifically the RBM frequency and energy excitation profiles, together with input from theoretical models. RRS is sensitive to both major and minor chiral species in the sample. We will compare the resulting chirality distribution obtained from RRS with those obtained from other orthogonal measurement techniques.

  14. Resonance Raman study of the oxygenation cycle of optically trapped single red blood cells in a microfluidic system

    NASA Astrophysics Data System (ADS)

    Ramser, Kerstin; Logg, Katarina; Enger, Jonas; Goksor, Mattias; Kall, Mikael; Hanstorp, Dag

    2004-10-01

    The average environmental response of red blood cells (RBCs) is routinely measured in ensemble studies, but in such investigations valuable information on the single cell level is obscured. In order to elucidate this hidden information is is important to enable the selection of single cells with certain properties while subsequent dynamics triggered by environmental stimulation are recorded in real time. It is also desirable to manipulate and control the cells under phsyiological conditions. As shown here, this can be achieved by combining optical tweezers with a confocal Raman set-up equipped with a microfluidic system. A micro-Raman set-up is combined with an optical trap with separate optical paths, lasers and objectives, which enables the acquisition of resonance Raman profils of single RBCs. The microfluidic system, giving full control over the media surrounding the cell, consists of a pattern of channels and reservoirs produced by electron beam lithography and moulded in PDMS. Fresh Hepes buffer or buffer containing sodium dithionite are transported through the channels using electro-osmotic flow, while the direct Raman response of the single optically trapped RBC is registered in another reservoir in the middle of the channel. Thus, it is possible to monitor the oxygenation cycle in a single cell and to study photo-induced chemistry. This experimental set-up has high potential for monitoring the drug response or conformational changes caused by other environmental stimuli for many types of single functional cells since "in vivo" conditions can be created.

  15. Resonance Raman fingerprinting of multiheme cytochromes from the cytochrome c3 family.

    PubMed

    Di Paolo, Roberto E; Pereira, Patrícia M; Gomes, Inês; Valente, Filipa M A; Pereira, Inês A C; Franco, Ricardo

    2006-03-01

    Resonance Raman (RR) spectroscopy was used to investigate conformational characteristics of the hemes of several ferricytochromes of the cytochrome c3 family, electron transfer proteins isolated from the periplasm and membranes of sulfate-reducing bacteria. Our analysis concentrated on the low-frequency region of the RR spectra, a fingerprint region that includes vibrations for heme-protein C-S bonds [nu(C(a)S)]. It has been proposed that these bonds are directly involved in the electron transfer process. The three groups of tetraheme cytochrome c3 analyzed, namely Type I cytochrome c (3) (TpIc (3)s), Type II cytochrome c (3) (TpIIc (3)s) and Desulfomicrobium cytochromes c3, display different frequency separations for the two nu(C(a)S) lines that are similar among members of each group. These spectral differences correlate with differences in protein structure observed among the three groups of cytochromes c3. Two larger cytochromes of the cytochrome c3 family display RR spectral characteristics for the nu(C(a)S) lines that are closer to TpIIc3 than to TpIc3. Two other multiheme cytochromes from Desulfovibrio that do not belong to the cytochrome c3 family display nu(C(a)S) lines with reverse relative areas in comparison with the latter family. This RR study shows that the small differences in protein structure observed among these cytochrome c3 correlate to differences on the heme-protein bonds, which are likely to have an impact upon the protein function, making RR spectroscopy a sensitive and useful tool for characterizing these cytochromes.

  16. Real time monitoring of sickle cell hemoglobin fiber formation by UV resonance Raman spectroscopy.

    PubMed

    Knee, Kelly M; Mukerji, Ishita

    2009-10-20

    In sickle cell hemoglobin, individual tetramers associate into long fibers as a consequence of the mutation at the beta6 position. In this study UV resonance Raman spectroscopy is used to monitor the formation of Hb S fibers in real time through aromatic amino acid vibrational modes. The intermolecular contact formed by the mutation site ((1)beta(1)6 Glu-->Val) of one tetramer and the (2)beta(2)85 Phe-(2)beta(2)88 Leu hydrophobic pocket on a different tetramer is observed by monitoring the increase in signal intensity of Phe vibrational modes as a function of time, yielding kinetic progress curves similar to those obtained by turbidity measurements. Comparison of individual spectra collected at early time points (<1000 s) show small Phe intensity changes, which are attributed to weak transient associations of Hb S tetramers during the initial stages of the polymerization process. At later times (1000-2000 s) Phe signal intensity steadily increases because of increasing hydrophobicity of local Phe environment, a consequence of forming more stable (1)beta(1)-(2)beta(2) contacts. Tyr and Trp vibrational modes monitor H-bond strength between critical residues at the alpha(1)beta(2) interface of individual tetramers. Kinetic progress curves generated from these signals exhibit two distinct transitions at 2040 and 7340 s. These transitions, which occur later in time than those detected either by turbidity (1560 s) or by Phe signal intensity (1680 s), are attributed to initial fiber formation and subsequent formation of larger assemblies, such as macrofibers or gels. These results provide molecular insight into the interactions governing Hb S fiber formation. PMID:19778007

  17. Resonance Raman study of the active site of Coprinus cinereus peroxidase.

    PubMed

    Smulevich, G; Feis, A; Focardi, C; Tams, J; Welinder, K G

    1994-12-27

    Resonance Raman (RR) spectra for the resting state ferric and the reduced ferrous forms of recombinant Coprinus cinereus peroxidase (CIP), obtained with different excitation wavelengths and in polarized light, are reported. The spectra are compared with those obtained previously for cytochrome c peroxidase expressed in Escherichia coli [(CCP(MI)] and horseradish peroxidase (HRP-C). Although the enzymic properties of CIP and HRP-C are similar, the RR data show that, in terms of the heme cavity structures, CIP and CCP(MI) are much more closely related to each other than to HRP-C. The ferric state of CIP at neutral pH is characteristic mainly of a five-coordinate high spin heme. However, the lower frequency of the v2 mode and a higher frequency of the v(C = C) vinyl stretching modes for CIP as compared to CCP, indicate a higher degree of vibrational coupling between the two modes in CIP. In addition, CIP is rather unstable under low laser power irradiation as an irreversible transition to a six-coordinate high spin heme followed by a second transition to a six-coordinate low spin heme is observed. This instability of CIP as compared to CCP(MI) is proposed to be a consequence of the presence of a distal Phe54 in CIP rather than the homologous Trp51 in CCP, as Trp51 is hydrogen-bonded to a distal water molecule located above the heme Fe thereby preventing its coordination in CCP. In CIP the FeII-His RR band has two components with frequencies at 230 and 211 cm-1.(ABSTRACT TRUNCATED AT 250 WORDS)

  18. Resonant Raman spectroscopy study of swift heavy ion irradiated MoS2

    NASA Astrophysics Data System (ADS)

    Guo, Hang; Sun, Youmei; Zhai, Pengfei; Zeng, Jian; Zhang, Shengxia; Hu, Peipei; Yao, Huijun; Duan, Jinglai; Hou, Mingdong; Liu, Jie

    2016-08-01

    Molybdenum disulphide (MoS2) crystal samples were irradiated by swift heavy ions (209Bi and 56Fe). Hillock-like latent tracks were observed on the surface of irradiated MoS2 by atomic force microscopy. The modifications of properties of irradiated MoS2 were investigated by resonant Raman spectroscopy and ultraviolet-visible spectroscopy (UV-Vis). A new peak (E1u2, ∼385.7 cm-1) occurs near the in-plane E2g1 peak (∼383.7 cm-1) after irradiation. The two peaks shift towards lower frequency and broaden due to structural defects and stress with increasing fluence. When irradiated with high fluence, two other new peaks appear at ∼ 190 and ∼ 230 cm-1. The peak at ∼230 cm-1 is disorder-induced LA(M) mode. The presence of this mode indicates defects induced by irradiation. The feature at ∼460 cm-1 is composed of 2LA(M) (∼458 cm-1) and A2u (∼466 cm-1) mode. With increasing fluence, the integrated intensity ratio between 2LA(M) and A2u increases. The relative enhancement of 2LA(M) mode is in agreement with the appearance of LA(M) mode, which both demonstrate structural disorder in irradiated MoS2. The ∼423-cm-1 peak shifts toward lower frequency due to the decrease in exciton energy of MoS2, and this was demonstrated by the results of UV-Vis spectra. The decrease in exciton energy could be due to introduction of defect levels into band gap.

  19. Spatially resolved confocal resonant Raman microscopic analysis of anode-grown Geobacter sulfurreducens biofilms.

    PubMed

    Lebedev, Nikolai; Strycharz-Glaven, Sarah M; Tender, Leonard M

    2014-02-01

    When grown on the surface of an anode electrode, Geobacter sulfurreducens forms a multi-cell thick biofilm in which all cells appear to couple the oxidation of acetate with electron transport to the anode, which serves as the terminal metabolic electron acceptor. Just how electrons are transported through such a biofilm from cells to the underlying anode surface over distances that can exceed 20 microns remains unresolved. Current evidence suggests it may occur by electron hopping through a proposed network of redox cofactors composed of immobile outer membrane and/or extracellular multi-heme c-type cytochromes. In the present work, we perform a spatially resolved confocal resonant Raman (CRR) microscopic analysis to investigate anode-grown Geobacter biofilms. The results confirm the presence of an intra-biofilm redox gradient whereby the probability that a heme is in the reduced state increases with increasing distance from the anode surface. Such a gradient is required to drive electron transport toward the anode surface by electron hopping via cytochromes. The results also indicate that at open circuit, when electrons are expected to accumulate in redox cofactors involved in electron transport due to the inability of the anode to accept electrons, nearly all c-type cytochrome hemes detected in the biofilm are oxidized. The same outcome occurs when a comparable potential to that measured at open circuit (-0.30 V vs. SHE) is applied to the anode, whereas nearly all hemes are reduced when an exceedingly negative potential (-0.50 V vs. SHE) is applied to the anode. These results suggest that nearly all c-type cytochrome hemes detected in the biofilm can be electrochemically accessed by the electrode, but most have oxidation potentials too negative to transport electrons originating from acetate metabolism. The results also reveal a lateral heterogeneity (x-y dimensions) in the type of c-type cytochromes within the biofilm that may affect electron transport to the

  20. Localized surface plasmon resonance immunoassay and verification using surface-enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Yonzon, Chanda R.; Zhang, Xiaoyu; Van Duyne, Richard P.

    2003-11-01

    This work exploits the localized surface plasmon resonance (LSPR) spectroscopy of noble metal nanoparticles to achieve sensitive and selective detection of biological analytes. Noble metal nanoparticles exhibit an LSPR that is strongly dependent on their size, shape, material, and the local dielectric environment. The LSPR is also responsible for the intense signals observed in surface-enhanced Raman scattering (SERS). Ag nanoparticles fabricated using the nanosphere lithography (NSL) technique exploits this LSPR sensitivity as a signal transduction method in biosensing applications. The current work implements LSPR biosensing for the anti dinitrophenyl (antiDNP) immunoassay system. Upon forming the 2,4 dinitrobenzoic acid/antiDNP complex, this system shows a large LSPR shift of 44 nm when exposed to antiDNP concentration of 1.5 x 10-6 M. In addition, due to the unique molecular characteristics of the functional groups on the biosensor, it can also be characterized using SERS. First, the nanoparticles are functionalized with a mixed self-assembled monolayer (SAM) comprised of 2:1 octanethiol and 11-amino undecanethiol. The SAM is exposed to 2,4-dinitrobenzoic acid with the 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride (EDC) coupling reagent. Finally, the 2,4-dinitrophenyl terminated SAM is exposed to various concentration of antiDNP. LSPR shifts indicate the occurrence of a binding event. SER spectra confirm binding of 2,4 dinitrobenzoic acid with amine-terminated SAM. This LSPR/SERS biosensing method can be generalized to a myriad of biologically relevant systems.

  1. Raman and x-ray absorption spectroscopy characterization of Zr-doped MOCVD YBa2Cu3O6+δ

    NASA Astrophysics Data System (ADS)

    Maroni, V. A.; Kropf, A. J.; Aytug, T.; Paranthaman, M.

    2010-01-01

    Metal-organic chemical vapor deposited YBa2Cu3O6+δ (YBCO) films (about 0.9 µm thick) containing varying amounts of added zirconium were examined by Raman microscopy and synchrotron x-ray absorption spectroscopy. The self-field and in-field (1 T, B\\parallel c ) Jc performance of the YBCO films at 77 K (reported by the group at Oak Ridge National Laboratory that fabricated the samples) exhibited an increase on going from 0 mol% (m/o) Zr-added to 2.5 m/o Zr-added but then decreased sharply with increasing Zr content. Raman measurements on these films showed that the added Zr had little effect on YBCO cation disorder up to about 7.5 m/o Zr-added. Cation disorder increased while Ba-Cu-O content remained relatively constant for Zr additions >=7.5 m/o. In the region of sharpest descent of Jc with increasing Zr content (2.5-7.5 m/o Zr-added) neither the cation disorder nor the Ba-Cu-O content showed a systematic variation with Jc. Zirconium K edge x-ray absorption near-edge spectroscopy revealed that virtually all of the added Zr in each sample was present as a BaZrO3-like phase (BZO). The Jc performance of the Zr-added films showed a high correlation with the variations in the next-nearest-neighbor Zr-M (M = Zr, Y) scattering path amplitude from the extended x-ray absorption fine structure (EXAFS) and the critical temperature over the full range of Zr additions and with cation disorder at the higher Zr-added levels (>7.5 m/o). There was no obvious correlation with the amount of residual barium cuprate or CuO. Approximate ranges for the BZO particle dimensions estimated from the EXAFS data indicated that the mean particle size gets larger with increasing Zr addition.

  2. Microplasmas as vacuum ultraviolet source for Cl-atom density measurements by resonance absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Martin, Virginie; Bauville, Gérard; Sadeghi, Nader; Puech, Vincent

    2011-11-01

    A micro-hollow cathode discharge was used to generate radiation on the chlorine atom resonance lines. Such radiation could be used to measure, by resonance absorption spectroscopy, the density of chlorine atoms in either ground state (3p5 2P3/2) or in the fine structure metastable state (3p5 2P1/2), which is located at 882.35 cm-1. Among the nine analysed lines in the 132-142 nm spectral region, only those at 137.953 and 139.653 nm, which are strong enough and are not affected by the self-absorption, can be used for the resonance absorption diagnostic of the ground state and the metastable state, respectively. The best operating conditions of the lamp source are 0.5% of Cl2 in argon at 150 mbar and 4 mA discharge current. The measured 800 ± 30 K gas temperature of the microplasma, indicates that under these specific conditions, these two lines are dominantly Doppler broadened. So their profile is Gaussian shaped with full widths at half maximum of (4.7 ± 0.1) × 10-4 nm.

  3. Raman spectroscopy of white wines.

    PubMed

    Martin, Coralie; Bruneel, Jean-Luc; Guyon, François; Médina, Bernard; Jourdes, Michael; Teissedre, Pierre-Louis; Guillaume, François

    2015-08-15

    The feasibility of exploiting Raman scattering to analyze white wines has been investigated using 3 different wavelengths of the incoming laser radiation in the near-UV (325 nm), visible (532 nm) and near infrared (785 nm). To help in the interpretation of the Raman spectra, the absorption properties in the UV-visible range of two wine samples as well as their laser induced fluorescence have also been investigated. Thanks to the strong intensity enhancement of the Raman scattered light due to electronic resonance with 325 nm laser excitation, hydroxycinnamic acids may be detected and analyzed selectively. Fructose and glucose may also be easily detected below ca. 1000 cm(-1). This feasibility study demonstrates the potential of the Raman spectroscopic technique for the analysis of white wines.

  4. Detection of Structural Changes upon One-Electron Oxidation and Reduction of Stilbene Derivatives by Time-Resolved Resonance Raman Spectroscopy during Pulse Radiolysis and Theoretical Calculations.

    PubMed

    Fujitsuka, Mamoru; Cho, Dae Won; Choi, Jungkweon; Tojo, Sachiko; Majima, Tetsuro

    2015-07-01

    Stilbene (St) derivatives have been investigated for many years because of their interesting photochemical reactions such as cis-trans isomerization in the excited states and charged states and their relation to poly(p-phenylenevinylene)s. To clarify their charged state properties, structural information is indispensable. In the present study, radical cations and radical anions of St derivatives were investigated by radiation chemical methods. Absorption spectra of radical ion states were obtained by transient absorption measurements during pulse radiolysis; theoretical calculations that included the solvent effect afforded reasonable assignments. The variation in the peak position was explained by using HOMO and LUMO energy levels. Structural changes upon one-electron oxidation and reduction were detected by time-resolved resonance Raman measurements during pulse radiolysis. Significant downshifts were observed with the CC stretching mode of the ethylenic groups, indicative of the decrease in the bonding order. It was confirmed that the downshifts observed with reduction were larger than those with oxidation. On the other hand, the downshift caused by oxidation depends significantly on the electron-donating or electron-withdrawing nature of the substituents.

  5. Comparison of simplified sum-over-state expressions to calculate resonance Raman intensities including Franck-Condon and Herzberg-Teller effects.

    PubMed

    Guthmuller, Julien

    2016-02-14

    Sum-over-state (SOS) expressions to simulate absorption spectroscopy and resonance Raman (RR) scattering including Franck-Condon (FC) and Herzberg-Teller (HT) effects are described. Starting from the general SOS method, several simplified SOS formulae are derived. In particular, within the so-called independent mode displaced harmonic oscillator model, it is shown that including the vibronic structure in the absorption and RR spectra only requires the calculation of FC overlap integrals of the type θg0|θev, where g, e, and v stand for the electronic ground state, excited state, and vibrational quantum number, respectively. Additionally, an approximation of the latter approach is introduced, referred as the simplified Φe method, in which the FC factors are neglected. This method is advantageous from the computational point of view and it is demonstrated that it reproduces the main characteristics of the more involved approaches. The merits and drawbacks of the different methods are discussed by applying them to the prototypical compound of Rhodamine 6G. Overall, this work intends to unravel and clarify some differences in the SOS theories of RR scattering. PMID:26874481

  6. Detection of Structural Changes upon One-Electron Oxidation and Reduction of Stilbene Derivatives by Time-Resolved Resonance Raman Spectroscopy during Pulse Radiolysis and Theoretical Calculations.

    PubMed

    Fujitsuka, Mamoru; Cho, Dae Won; Choi, Jungkweon; Tojo, Sachiko; Majima, Tetsuro

    2015-07-01

    Stilbene (St) derivatives have been investigated for many years because of their interesting photochemical reactions such as cis-trans isomerization in the excited states and charged states and their relation to poly(p-phenylenevinylene)s. To clarify their charged state properties, structural information is indispensable. In the present study, radical cations and radical anions of St derivatives were investigated by radiation chemical methods. Absorption spectra of radical ion states were obtained by transient absorption measurements during pulse radiolysis; theoretical calculations that included the solvent effect afforded reasonable assignments. The variation in the peak position was explained by using HOMO and LUMO energy levels. Structural changes upon one-electron oxidation and reduction were detected by time-resolved resonance Raman measurements during pulse radiolysis. Significant downshifts were observed with the CC stretching mode of the ethylenic groups, indicative of the decrease in the bonding order. It was confirmed that the downshifts observed with reduction were larger than those with oxidation. On the other hand, the downshift caused by oxidation depends significantly on the electron-donating or electron-withdrawing nature of the substituents. PMID:26052901

  7. Quaternary Ammonium Oxidative Demethylation: X-ray Crystallographic, Resonance Raman and UV-visible Spectroscopic Analysis of a Rieske-type Demethylase

    SciTech Connect

    Daughtry K. D.; Orville A.; Xiao, Y.; Stoner-Ma, D.; Cho, E.; Liu, P.; Allen, K. N.

    2012-02-01

    Herein, the structure resulting from in situ turnover in a chemically challenging quaternary ammonium oxidative demethylation reaction was captured via crystallographic analysis and analyzed via single-crystal spectroscopy. Crystal structures were determined for the Rieske-type monooxygenase, stachydrine demethylase, in the unliganded state (at 1.6 {angstrom} resolution) and in the product complex (at 2.2 {angstrom} resolution). The ligand complex was obtained from enzyme aerobically cocrystallized with the substrate stachydrine (N,N-dimethylproline). The ligand electron density in the complex was interpreted as proline, generated within the active site at 100 K by the absorption of X-ray photon energy and two consecutive demethylation cycles. The oxidation state of the Rieske iron-sulfur cluster was characterized by UV-visible spectroscopy throughout X-ray data collection in conjunction with resonance Raman spectra collected before and after diffraction data. Shifts in the absorption band wavelength and intensity as a function of absorbed X-ray dose demonstrated that the Rieske center was reduced by solvated electrons generated by X-ray photons; the kinetics of the reduction process differed dramatically for the liganded complex compared to unliganded demethylase, which may correspond to the observed turnover in the crystal.

  8. Comparison of simplified sum-over-state expressions to calculate resonance Raman intensities including Franck-Condon and Herzberg-Teller effects

    NASA Astrophysics Data System (ADS)

    Guthmuller, Julien

    2016-02-01

    Sum-over-state (SOS) expressions to simulate absorption spectroscopy and resonance Raman (RR) scattering including Franck-Condon (FC) and Herzberg-Teller (HT) effects are described. Starting from the general SOS method, several simplified SOS formulae are derived. In particular, within the so-called independent mode displaced harmonic oscillator model, it is shown that including the vibronic structure in the absorption and RR spectra only requires the calculation of FC overlap integrals of the type <" separators=" θ g 0 | θ e v > , where g, e, and v stand for the electronic ground state, excited state, and vibrational quantum number, respectively. Additionally, an approximation of the latter approach is introduced, referred as the simplified Φe method, in which the FC factors are neglected. This method is advantageous from the computational point of view and it is demonstrated that it reproduces the main characteristics of the more involved approaches. The merits and drawbacks of the different methods are discussed by applying them to the prototypical compound of Rhodamine 6G. Overall, this work intends to unravel and clarify some differences in the SOS theories of RR scattering.

  9. Enhanced Absorption in 2D Materials Via Fano- Resonant Photonic Crystals

    DOE PAGES

    Wang, Wenyi; Klotz, Andrey; Yang, Yuanmu; Li, Wei; Kravchenko, Ivan I.; Briggs, Dayrl P.; Bolotin, Kirill; Valentine, Jason

    2015-05-01

    The use of two-dimensional (2D) materials in optoelectronics has attracted much attention due to their fascinating optical and electrical properties. For instance, graphenebased devices have been employed for applications such as ultrafast and broadband photodetectors and modulators while transition metal dichalcogenide (TMDC) based photodetectors can be used for ultrasensitive photodetection. However, the low optical absorption of 2D materials arising from their atomic thickness limits the maximum attainable external quantum efficiency. For example, in the visible and NIR regimes monolayer MoS2 and graphene absorb only ~10% and 2.3% of incoming light, respectively. Here, we experimentally demonstrate the use of Fano-resonant photonicmore » crystals to significantly boost absorption in atomically thin materials. Using graphene as a test bed, we demonstrate that absorption in the monolayer thick material can be enhanced to 77% within the telecommunications band, the highest value reported to date. We also show that the absorption in the Fano-resonant structure is non-local, with light propagating up to 16 μm within the structure. This property is particularly beneficial in harvesting light from large areas in field-effect-transistor based graphene photodetectors in which separation of photo-generated carriers only occurs ~0.2 μm adjacent to the graphene/electrode interface.« less

  10. Theory of Half-Space Light Absorption Enhancement for Leaky Mode Resonant Nanowires.

    PubMed

    Jia, Yiming; Qiu, Min; Wu, Hui; Cui, Yi; Fan, Shanhui; Ruan, Zhichao

    2015-08-12

    Semiconductor nanowires supporting leaky mode resonances have been used to increase light absorption in optoelectronic applications from solar cell to photodetector and sensor. The light conventionally illuminates these devices with a wide range of different incident angles from half space. Currently, most of the investigated nanowires have centrosymmetric geometry cross section, such as circle, hexagon, and rectangle. Here we show that the absorption capability of these symmetrical nanowires has an upper limit under the half-space illumination. Based on the temporal coupled-mode equation, we develop a reciprocity theory for leaky mode resonances in order to connect the angle-dependent absorption cross section and the radiation pattern. We show that in order to exceed such a half-space limit the radiation pattern should be noncentrosymmetric and dominate in the direction reciprocal to the illumination. As an example, we design a metal trough structure to achieve the desired radiation pattern for an embedded nanowire. In comparison to a single nanowire case the trough structure indeed overcomes the half-space limit and leads to 39% and 64% absorption enhancement in TM and TE polarizations, respectively. Also the trough structure enables the enhancement over a broad wavelength range.

  11. Enhanced absorption in two-dimensional materials via Fano-resonant photonic crystals

    NASA Astrophysics Data System (ADS)

    Wang, Wenyi; Klots, Andrey; Yang, Yuanmu; Li, Wei; Kravchenko, Ivan I.; Briggs, Dayrl P.; Bolotin, Kirill I.; Valentine, Jason

    2015-05-01

    The use of two-dimensional (2D) materials in optoelectronics has attracted much attention due to their fascinating optical and electrical properties. However, the low optical absorption of 2D materials arising from their atomic thickness limits the maximum attainable external quantum efficiency. For example, in the visible and near-infrared regimes monolayer MoS2 and graphene absorb only ˜10% and 2.3% of incoming light, respectively. Here, we experimentally demonstrate the use of Fano-resonant photonic crystals to significantly boost absorption in atomically thin materials. Using graphene as a test bed, we demonstrate that absorption in the monolayer thick material can be enhanced to 77% within the telecommunications band, the highest value reported to date. We also show that the absorption in the Fano-resonant structure is non-local, with light propagating up to 16 μm within the structure. This property is particularly beneficial in harvesting light from large areas in field-effect-transistor based graphene photodetectors in which separation of photo-generated carriers only occurs ˜0.2 μm adjacent to the graphene/electrode interface.

  12. Enhanced Absorption in 2D Materials Via Fano- Resonant Photonic Crystals

    SciTech Connect

    Wang, Wenyi; Klotz, Andrey; Yang, Yuanmu; Li, Wei; Kravchenko, Ivan I.; Briggs, Dayrl P.; Bolotin, Kirill; Valentine, Jason

    2015-05-01

    The use of two-dimensional (2D) materials in optoelectronics has attracted much attention due to their fascinating optical and electrical properties. For instance, graphenebased devices have been employed for applications such as ultrafast and broadband photodetectors and modulators while transition metal dichalcogenide (TMDC) based photodetectors can be used for ultrasensitive photodetection. However, the low optical absorption of 2D materials arising from their atomic thickness limits the maximum attainable external quantum efficiency. For example, in the visible and NIR regimes monolayer MoS2 and graphene absorb only ~10% and 2.3% of incoming light, respectively. Here, we experimentally demonstrate the use of Fano-resonant photonic crystals to significantly boost absorption in atomically thin materials. Using graphene as a test bed, we demonstrate that absorption in the monolayer thick material can be enhanced to 77% within the telecommunications band, the highest value reported to date. We also show that the absorption in the Fano-resonant structure is non-local, with light propagating up to 16 μm within the structure. This property is particularly beneficial in harvesting light from large areas in field-effect-transistor based graphene photodetectors in which separation of photo-generated carriers only occurs ~0.2 μm adjacent to the graphene/electrode interface.

  13. Enhanced absorption in two-dimensional materials via Fano-resonant photonic crystals

    SciTech Connect

    Wang, Wenyi; Klots, Andrey; Bolotin, Kirill I.; Yang, Yuanmu; Li, Wei; Valentine, Jason; Kravchenko, Ivan I.; Briggs, Dayrl P.

    2015-05-04

    The use of two-dimensional (2D) materials in optoelectronics has attracted much attention due to their fascinating optical and electrical properties. However, the low optical absorption of 2D materials arising from their atomic thickness limits the maximum attainable external quantum efficiency. For example, in the visible and near-infrared regimes monolayer MoS{sub 2} and graphene absorb only ∼10% and 2.3% of incoming light, respectively. Here, we experimentally demonstrate the use of Fano-resonant photonic crystals to significantly boost absorption in atomically thin materials. Using graphene as a test bed, we demonstrate that absorption in the monolayer thick material can be enhanced to 77% within the telecommunications band, the highest value reported to date. We also show that the absorption in the Fano-resonant structure is non-local, with light propagating up to 16 μm within the structure. This property is particularly beneficial in harvesting light from large areas in field-effect-transistor based graphene photodetectors in which separation of photo-generated carriers only occurs ∼0.2 μm adjacent to the graphene/electrode interface.

  14. Spin pumping from a ferromagnet into a hopping insulator: Role of resonant absorption of magnons

    NASA Astrophysics Data System (ADS)

    Raikh, Mikhail; Zhang, Yue; Pesin, Dmytro

    Motivated by recent experiments on spin pumping from a ferromagnet into organic materials in which the charge transport is due to hopping, we study theoretically the generation and propagation of spin current in a hopping insulator. Unlike metals, the spin polarization at the boundary with ferromagnet is created as a result of magnon absorption within pairs of localized states and it spreads following the current-currying resistor network (although the charge current is absent). We consider a classic resonant mechanism of the ac absorption in insulators and adapt it to the absorption of magnons. A strong enhancement of pumping efficiency is predicted when the Zeeman splitting of the localized states in external magnetic field is equal to the frequency of ferromagnetic resonance. Under this condition the absorption of a magnon takes place within individual sites. This work was supported by the NSF MRSEC program at the University of Utah under Grant No. DMR 1121252 (Z.Y. and M.E.R.) and by the NSF Grant No. DMR 1409089 (D.A.P).

  15. Quantitative Raman spectroscopy in turbid media

    NASA Astrophysics Data System (ADS)

    Reble, Carina; Gersonde, Ingo; Andree, Stefan; Eichler, Hans Joachim; Helfmann, Jürgen

    2010-05-01

    Intrinsic Raman spectra of biological tissue are distorted by the influences of tissue absorption and scattering, which significantly challenge signal quantification. A combined Raman and spatially resolved reflectance setup is introduced to measure the absorption coefficient μa and the reduced scattering coefficient μs' of the tissue, together with the Raman signals. The influence of μa and μs' on the resonance Raman signal of β-carotene is measured at 1524 cm-1 by tissue phantom measurements and Monte Carlo simulations for μa=0.01 to 10 mm-1 and μs'=0.1 to 10 mm-1. Both methods show that the Raman signal drops roughly proportional to 1/μa for μa>0.2 mm-1 in the measurement geometry and that the influence of μs' is weaker, but not negligible. Possible correction functions dependent on the elastic diffuse reflectance are investigated to correct the Raman signal for the influence of μa and μs', provided that μa and μs' are measured as well. A correction function based on the Monte Carlo simulation of Raman signals is suggested as an alternative. Both approaches strongly reduce the turbidity-induced variation of the Raman signals and allow absolute Raman scattering coefficients to be determined.

  16. Structure, spectra and antioxidant action of ascorbic acid studied by density functional theory, Raman spectroscopic and nuclear magnetic resonance techniques.

    PubMed

    Singh, Gurpreet; Mohanty, B P; Saini, G S S

    2016-02-15

    Structure, vibrational and nuclear magnetic resonance spectra, and antioxidant action of ascorbic acid towards hydroxyl radicals have been studied computationally and in vitro by ultraviolet-visible, nuclear magnetic resonance and vibrational spectroscopic techniques. Time dependant density functional theory calculations have been employed to specify various electronic transitions in ultraviolet-visible spectra. Observed chemical shifts and vibrational bands in nuclear magnetic resonance and vibrational spectra, respectively have been assigned with the help of calculations. Changes in the structure of ascorbic acid in aqueous phase have been examined computationally and experimentally by recording Raman spectra in aqueous medium. Theoretical calculations of the interaction between ascorbic acid molecule and hydroxyl radical predicted the formation of dehydroascorbic acid as first product, which has been confirmed by comparing its simulated spectra with the corresponding spectra of ascorbic acid in presence of hydrogen peroxide.

  17. Structure, spectra and antioxidant action of ascorbic acid studied by density functional theory, Raman spectroscopic and nuclear magnetic resonance techniques

    NASA Astrophysics Data System (ADS)

    Singh, Gurpreet; Mohanty, B. P.; Saini, G. S. S.

    2016-02-01

    Structure, vibrational and nuclear magnetic resonance spectra, and antioxidant action of ascorbic acid towards hydroxyl radicals have been studied computationally and in vitro by ultraviolet-visible, nuclear magnetic resonance and vibrational spectroscopic techniques. Time dependant density functional theory calculations have been employed to specify various electronic transitions in ultraviolet-visible spectra. Observed chemical shifts and vibrational bands in nuclear magnetic resonance and vibrational spectra, respectively have been assigned with the help of calculations. Changes in the structure of ascorbic acid in aqueous phase have been examined computationally and experimentally by recording Raman spectra in aqueous medium. Theoretical calculations of the interaction between ascorbic acid molecule and hydroxyl radical predicted the formation of dehydroascorbic acid as first product, which has been confirmed by comparing its simulated spectra with the corresponding spectra of ascorbic acid in presence of hydrogen peroxide.

  18. Broadband optical absorption by tunable Mie resonances in silicon nanocone arrays

    DOE PAGES

    Wang, Z. Y.; Zhang, R. J.; Wang, S. Y.; Lu, M.; Chen, X.; Zheng, Y. X.; Chen, L. Y.; Ye, Z.; Wang, C. Z.; Ho, K. M.

    2015-01-15

    Nanostructure arrays such as nanowire, nanopillar, and nanocone arrays have been proposed to be promising antireflection structures for photovoltaic applications due to their great light trapping ability. In this paper, the optical properties of Si nanopillar and nanocone arrays in visible and infrared region were studied by both theoretical calculations and experiments. The results show that the Mie resonance can be continuously tuned across a wide range of wavelength by varying the diameter of the nanopillars. However, Si nanopillar array with uniform diameter exhibits only discrete resonance mode, thus can't achieve a high broadband absorption. On the other hand, themore » Mie resonance wavelength in a Si nanocone array can vary continuously as the diameters of the cross sections increase from the apex to the base. Therefore Si nanocone arrays can strongly interact with the incident light in the broadband spectrum and the absorbance by Si nanocone arrays is higher than 95% over the wavelength from 300 to 2000 nm. In addition to the Mie resonance, the broadband optical absorption of Si nanocone arrays is also affected by Wood-Rayleigh anomaly effect and metal impurities introduced in the fabrication process.« less

  19. Broadband optical absorption by tunable Mie resonances in silicon nanocone arrays

    SciTech Connect

    Wang, Z. Y.; Zhang, R. J.; Wang, S. Y.; Lu, M.; Chen, X.; Zheng, Y. X.; Chen, L. Y.; Ye, Z.; Wang, C. Z.; Ho, K. M.

    2015-01-15

    Nanostructure arrays such as nanowire, nanopillar, and nanocone arrays have been proposed to be promising antireflection structures for photovoltaic applications due to their great light trapping ability. In this paper, the optical properties of Si nanopillar and nanocone arrays in visible and infrared region were studied by both theoretical calculations and experiments. The results show that the Mie resonance can be continuously tuned across a wide range of wavelength by varying the diameter of the nanopillars. However, Si nanopillar array with uniform diameter exhibits only discrete resonance mode, thus can't achieve a high broadband absorption. On the other hand, the Mie resonance wavelength in a Si nanocone array can vary continuously as the diameters of the cross sections increase from the apex to the base. Therefore Si nanocone arrays can strongly interact with the incident light in the broadband spectrum and the absorbance by Si nanocone arrays is higher than 95% over the wavelength from 300 to 2000 nm. In addition to the Mie resonance, the broadband optical absorption of Si nanocone arrays is also affected by Wood-Rayleigh anomaly effect and metal impurities introduced in the fabrication process.

  20. Enhancing ferromagnetic resonance absorption for very thin insulating magnetic films with spin plasmonics

    NASA Astrophysics Data System (ADS)

    Chui, S. T.

    2015-05-01

    We consider enhancing the ferromagnetic resonance (FMR) absorption of very thin insulating magnetic films by placing it on top of a dielectric. We find that the signal is enhanced by at least an order of magnitude due to a new nonreciprocal interface resonance that is a mixture of the magnetic surface plasmon mode and a wave guide mode. This resonance occurs over a wide range of thicknesses of the dielectric that is still much less than the wavelength and is made possible by the negative magnetic susceptibility of the magnetic layer. The line width of absorption is reduced by an order of magnitude less than the Gilbert damping parameter. At some frequency, the group velocity of this resonance is negative. Experimentally, very thin yttrium iron garnet (YIG) films are grown on a Gadolinium Gallium Garnet (GGG) substrate which can be considered the dielectric. Our model applies to experiments performed in the YIG/GGG system. Indeed, our picture resolves the disagreement on the magnitude of the spin diffusion lengths obtained with the FMR and the Brillouin scattering techniques. It also provides for a way to make new adaptive thin film miniaturized photonic nonreciprocal devices with low loss.

  1. Enhancing ferromagnetic resonance absorption for very thin insulating magnetic films with spin plasmonics

    SciTech Connect

    Chui, S. T.

    2015-05-14

    We consider enhancing the ferromagnetic resonance (FMR) absorption of very thin insulating magnetic films by placing it on top of a dielectric. We find that the signal is enhanced by at least an order of magnitude due to a new nonreciprocal interface resonance that is a mixture of the magnetic surface plasmon mode and a wave guide mode. This resonance occurs over a wide range of thicknesses of the dielectric that is still much less than the wavelength and is made possible by the negative magnetic susceptibility of the magnetic layer. The line width of absorption is reduced by an order of magnitude less than the Gilbert damping parameter. At some frequency, the group velocity of this resonance is negative. Experimentally, very thin yttrium iron garnet (YIG) films are grown on a Gadolinium Gallium Garnet (GGG) substrate which can be considered the dielectric. Our model applies to experiments performed in the YIG/GGG system. Indeed, our picture resolves the disagreement on the magnitude of the spin diffusion lengths obtained with the FMR and the Brillouin scattering techniques. It also provides for a way to make new adaptive thin film miniaturized photonic nonreciprocal devices with low loss.

  2. Nickel(II)-substituted azurin I from Alcaligenes xylosoxidans as characterized by resonance Raman spectroscopy at cryogenic temperature.

    PubMed

    Fitzpatrick, Marzena B; Czernuszewicz, Roman S

    2009-05-01

    Metal-substituted blue copper proteins (cupredoxins) have been successfully used to study the effect of metal-ion identity on their active-site properties, specifically the coordination geometry and metal-ligand bond strengths. In this work, low-temperature (77 K) resonance Raman (RR) spectra of the blue copper protein Alcaligenes xylosoxidans azurin I and its Ni(II) derivative are reported. A detailed analysis of all observed bands is presented and responsiveness to metal substitution is discussed in terms of structural and bonding changes. The native cupric site exhibits a RR spectrum characteristic of a primarily trigonal planar (type 1) coordination geometry, identified by the nu(Cu-S)(Cys) markers at 373, 399, 409, and 430 cm(-1). Replacement of Cu(II) with Ni(II) results in optical and RR spectra that reveal (1) a large hypsochromic shift in the main (Cys)S --> M(II) charge-transfer absorption from 622 to 440 nm, (2) greatly reduced metal-thiolate bonding interaction, indicated by substantially lower nu(Ni-S)(Cys) stretching frequencies, (3) elevation of the cysteine nu(C( beta )-S) stretching, amide III, and rho (s)(C( beta )H(2)) scissors vibrational modes, and (4) primarily four-coordinated, trigonally distorted tetrahedral geometry of the Ni(II) site that is marked by characteristic nu(Ni-S)(Cys) stretching RR bands at 347, 364, and 391 cm(-1). Comparisons of the electronic and vibrational properties between A. xylosoxidans azurin I and its closely structurally related azurin from Pseudomonas aeruginosa are made and discussed. For cupric azurins, the intensity-weighted average M(II)-S(Cys) stretching frequencies are calculated to be nu(Cu-S)(iwa) = 406.3 and 407.6 cm(-1), respectively. These values decreased to nu(Ni-S)(iwa) = 359.3 and 365.5 cm(-1), respectively, after Ni(II) --> Cu(II) exchange, suggesting that the metal-thiolate interactions are similar in the two native proteins but are much less alike in their Ni(II)-substituted forms.

  3. Pre-resonance-stimulated Raman scattering for water bilayer structure on laser-induced plasma bubble surface.

    PubMed

    Li, Zhanlong; Li, Hongdong; Fang, Wenhui; Wang, Shenghan; Sun, Chenglin; Li, Zuowei; Men, Zhiwei

    2015-07-15

    Pre-resonance-stimulated Raman scattering (PSRS) from water molecules in the air/water interfacial regions was studied when the laser-induced plasma bubble was generated at the interfaces. A characteristically lower Raman shift of OH-stretching vibrational modes of water molecules at around 3000  cm(-1) (370 meV) was observed, in which the mechanisms were possibly attributed to the strong hydrogen bond in a well-ordered water bilayer structure that was formed on a laser-induced plasma bubble surface. Simultaneously, the PSRS of ice Ih at about 3100  cm(-1) was obtained, which also belonged to the strong hydrogen bond effect in ice Ih structure.

  4. Quantum-mechanical analysis of the intensity distribution in spectra of resonant Raman scattering spectra of aqueous solutions of tyrosine

    NASA Astrophysics Data System (ADS)

    Burova, T. G.; Shcherbakov, R. S.

    2016-05-01

    Quantum-mechanical calculations of the intensity distribution in the resonant Raman scattering spectra of aqueous solutions of tyrosine excited by laser radiation with wavelengths of 244, 229, 218, 200, and 193 nm, as well as in the nonresonant Raman scattering spectrum excited at a wavelength of 488 nm, are performed. Satisfactory agreement is achieved between the calculation results and the experimental data. It is shown that the changes in the intensity distribution observed in the spectra with a change in the excitation wavelength from 244 to 193 nm correlate with the determined changes in the contribution made by excited electronic states into the scattering tensor components. It is noted that it is necessary to take into account the Herzberg-Teller effect and that the number of excited electronic states taken into account considerably affects the calculated relative intensities of lines. The possibility of existence of several tyrosine conformers in aqueous solution at room temperature is shown.

  5. Quantum theory of the far-off-resonance continuous-wave Raman laser: Heisenberg-Langevin approach

    SciTech Connect

    Roos, P. A.; Murphy, S. K.; Meng, L. S.; Carlsten, J. L.; Ralph, T. C.; White, A. G.; Brasseur, J. K.

    2003-07-01

    We present the quantum theory of the far-off-resonance continuous-wave Raman laser using the Heisenberg-Langevin approach. We show that the simplified quantum Langevin equations for this system are mathematically identical to those of the nondegenerate optical parametric oscillator in the time domain with the following associations: pump {r_reversible} pump, Stokes {r_reversible} signal, and Raman coherence {r_reversible} idler. We derive analytical results for both the steady-state behavior and the time-dependent noise spectra, using standard linearization procedures. In the semiclassical limit, these results match with previous purely semiclassical treatments, which yield excellent agreement with experimental observations. The analytical time-dependent results predict perfect photon statistics conversion from the pump to the Stokes and nonclassical behavior under certain operational conditions.

  6. Electron paramagnetic resonance and Raman spectroscopy studies on carbon-doped MgB{sub 2} superconductor nanomaterials

    SciTech Connect

    Bateni, Ali; Somer, Mehmet E-mail: msomer@ku.edu.tr; Erdem, Emre E-mail: msomer@ku.edu.tr; Repp, Sergej; Weber, Stefan; Acar, Selcuk; Kokal, Ilkin; Häßler, Wolfgang

    2015-04-21

    Undoped and carbon-doped magnesium diboride (MgB{sub 2}) samples were synthesized using two sets of mixtures prepared from the precursors, amorphous nanoboron, and as-received amorphous carbon-doped nanoboron. The microscopic defect structures of carbon-doped MgB{sub 2} samples were systematically investigated using X-ray powder diffraction, Raman and electron paramagnetic resonance spectroscopy. Mg vacancies and C-related dangling-bond active centers could be distinguished, and sp{sup 3}-hybridized carbon radicals were detected. A strong reduction in the critical temperature T{sub c} was observed due to defects and crystal distortion. The symmetry effect of the latter is also reflected on the vibrational modes in the Raman spectra.

  7. Davydov Splitting and Excitonic Resonance Effects in Raman Spectra of Few-Layer MoSe2.

    PubMed

    Kim, Kangwon; Lee, Jae-Ung; Nam, Dahyun; Cheong, Hyeonsik

    2016-08-23

    Raman spectra of few-layer MoSe2 were measured with eight excitation energies. New peaks that appear only near resonance with various exciton states are analyzed, and the modes are assigned. The resonance profiles of the Raman peaks reflect the joint density of states for optical transitions, but the symmetry of the exciton wave functions leads to selective enhancement of the A1g mode at the A exciton energy and the shear mode at the C exciton energy. We also find Davydov splitting of intralayer A1g, E1g, and A2u modes due to interlayer interaction for some excitation energies near resonances. Furthermore, by fitting the spectral positions of interlayer shear and breathing modes and Davydov splitting of intralayer modes to a linear chain model, we extract the strength of the interlayer interaction. We find that the second-nearest-neighbor interlayer interaction amounts to about 30% of the nearest-neighbor interaction for both in-plane and out-of-plane vibrations. PMID:27479147

  8. Magnetic immunoassay for cancer biomarker detection based on surface-enhanced resonance Raman scattering from coupled plasmonic nanostructures.

    PubMed

    Rong, Zhen; Wang, Chongwen; Wang, Junfeng; Wang, Donggen; Xiao, Rui; Wang, Shengqi

    2016-10-15

    A surface-enhanced resonance Raman scattering (SERRS) sensor was developed for the ultrasensitive detection of cancer biomarkers. Capture antibody-coated silver shell magnetic nanoparticles (Fe3O4@Ag MNPs) were utilized as the CEA enrichment platform and the SERRS signal amplification substrate. Gold nanorods (AuNRs) were coated with a thin silver shell to be in resonance with the resonant Raman dye diethylthiatricarbocyanine iodide (DTTC) and the excitation wavelength at 785nm. The silver-coated AuNRs (Au@Ag NRs) were then modified with detection antibody as the SERRS tags. Sandwich immune complexes formed in the presence of the target biomarker carcinoembryonic antigen (CEA), and this formation induced the plasmonic coupling between the Au@Ag NRs and Fe3O4@Ag MNPs. The SERRS signal of DTTC molecules located in the coupled plasmonic nanostructures was significantly enhanced. As a result, the proposed SERRS sensor was able to detect CEA with a low limit of detection of 4.75fg/mL and a wide dynamic linear range from 10fg/mL to 100ng/mL. The sensor provides a novel SERRS strategy for trace analyte detection and has a potential for clinical applications. PMID:27149164

  9. Magnetic immunoassay for cancer biomarker detection based on surface-enhanced resonance Raman scattering from coupled plasmonic nanostructures.

    PubMed

    Rong, Zhen; Wang, Chongwen; Wang, Junfeng; Wang, Donggen; Xiao, Rui; Wang, Shengqi

    2016-10-15

    A surface-enhanced resonance Raman scattering (SERRS) sensor was developed for the ultrasensitive detection of cancer biomarkers. Capture antibody-coated silver shell magnetic nanoparticles (Fe3O4@Ag MNPs) were utilized as the CEA enrichment platform and the SERRS signal amplification substrate. Gold nanorods (AuNRs) were coated with a thin silver shell to be in resonance with the resonant Raman dye diethylthiatricarbocyanine iodide (DTTC) and the excitation wavelength at 785nm. The silver-coated AuNRs (Au@Ag NRs) were then modified with detection antibody as the SERRS tags. Sandwich immune complexes formed in the presence of the target biomarker carcinoembryonic antigen (CEA), and this formation induced the plasmonic coupling between the Au@Ag NRs and Fe3O4@Ag MNPs. The SERRS signal of DTTC molecules located in the coupled plasmonic nanostructures was significantly enhanced. As a result, the proposed SERRS sensor was able to detect CEA with a low limit of detection of 4.75fg/mL and a wide dynamic linear range from 10fg/mL to 100ng/mL. The sensor provides a novel SERRS strategy for trace analyte detection and has a potential for clinical applications.

  10. [Resonance Raman Spectral Properties Studies of Beta-carotene in Solution].

    PubMed

    Sun, Mei-jiao; Liu, Shuo; Liu, Tian-yuan; Xu, Sheng-nan; Sun, Cheng-lin; Zhou, Mi; Li, Zuo-wei

    2015-07-01

    Beta-carotene is an important kind of polyene biomolecules, which has significant applications on researching optoelectronic and functional materials. In-situ high pressure Raman spectra of beta-carotene are measured in CS2 solution and water respectively at pressure range from 0-0.60 GPa. Then we compared both of them the Raman shift and CC bond of the full width at half maximum (FWHM) of the Raman spectra. It is therefore concluded that both of the samples' Raman shift moved to the high wave number and the full width at half maximum increased depending of the pressure. The experiment phenomena were interpreted by the theory of "coherent weakly damped electronic-lattice vibration model" and "effective conjugation length model". The mechanism is that the beta-carotene is compressed and has the lower structure order, shorte the effective conjugation length, decreased Raman active, weaker the coherent weakly damping CC bond vibration in high pressure. Because of the CC bond length become short, so the Raman spectra are found to blueshift. The CC bond of the full width at half maximum (FWHM) of the Raman spectra increased is attributed to the increase of difference in C--C and C==C bond lengths. Moreover, due to dissolving in non-polar CS2 solvent, the beta-carotene encounters the interaction of the surrounding solvent molecules. So the dispersion force interaction between solute and solvent is more sensitive to pressure. Then it makes that the slop of Raman shift and the full width at half maximum in the CS2 solution are faster than dissolved in water with increasing pressure. This paper provides an application value for research on molecular structure change under the external field and the presence form of polyenes biomolecules in the solvent. PMID:26717749

  11. Local disorder investigation in NiS(2-x)Se(x) using Raman and Ni K-edge x-ray absorption spectroscopies.

    PubMed

    Marini, C; Joseph, B; Caramazza, S; Capitani, F; Bendele, M; Mitrano, M; Chermisi, D; Mangialardo, S; Pal, B; Goyal, M; Iadecola, A; Mathon, O; Pascarelli, S; Sarma, D D; Postorino, P

    2014-11-12

    We report on Raman and Ni K-edge x-ray absorption investigations of a NiS(2-x)Se(x) (with x = 0.00, 0.50/0.55, 0.60, and 1.20) pyrite family. The Ni K-edge absorption edge shows a systematic shift going from an insulating phase (x = 0.00 and 0.50) to a metallic phase (x = 0.60 and 1.20). The near-edge absorption features show a clear evolution with Se doping. The extended x-ray absorption fine structure data reveal the evolution of the local structure with Se doping which mainly governs the local disorder. We also describe the decomposition of the NiS(2-x)Se(x) Raman spectra and investigate the weights of various phonon modes using Gaussian and Lorentzian profiles. The effectiveness of the fitting models in describing the data is evaluated by means of Bayes factor estimation. The Raman analysis clearly demonstrates the disorder effects due to Se alloying in describing the phonon spectra of NiS(2-x)Se(x) pyrites. PMID:25320052

  12. Local disorder investigation in NiS(2-x)Se(x) using Raman and Ni K-edge x-ray absorption spectroscopies.

    PubMed

    Marini, C; Joseph, B; Caramazza, S; Capitani, F; Bendele, M; Mitrano, M; Chermisi, D; Mangialardo, S; Pal, B; Goyal, M; Iadecola, A; Mathon, O; Pascarelli, S; Sarma, D D; Postorino, P

    2014-11-12

    We report on Raman and Ni K-edge x-ray absorption investigations of a NiS(2-x)Se(x) (with x = 0.00, 0.50/0.55, 0.60, and 1.20) pyrite family. The Ni K-edge absorption edge shows a systematic shift going from an insulating phase (x = 0.00 and 0.50) to a metallic phase (x = 0.60 and 1.20). The near-edge absorption features show a clear evolution with Se doping. The extended x-ray absorption fine structure data reveal the evolution of the local structure with Se doping which mainly governs the local disorder. We also describe the decomposition of the NiS(2-x)Se(x) Raman spectra and investigate the weights of various phonon modes using Gaussian and Lorentzian profiles. The effectiveness of the fitting models in describing the data is evaluated by means of Bayes factor estimation. The Raman analysis clearly demonstrates the disorder effects due to Se alloying in describing the phonon spectra of NiS(2-x)Se(x) pyrites.

  13. Plasma dispersion effect assisted nanoscopy based on tuning of absorption and scattering resonances of nanoparticles

    NASA Astrophysics Data System (ADS)

    Danan, Yossef; Ilovitsh, Tali; Liu, Danping; Pinhas, Hadar; Sinvani, Moshe; Ramon, Yehonatan; Azougi, Jonathan; Douplik, Alexandre; Zalevsky, Zeev

    2016-03-01

    In this paper we present gold nanoparticles coated with silicon that switch the order between the scattering and the absorption magnitude at the resonance peak and tune the plasmon resonance over the spectrum. This is obtained by modifying the refractive index of the silicon coating of the nanoparticle by illuminating it with a pumping light due to the plasma dispersion effect in silicon. We also report how changing the diffraction limited point spread function through the utilization of plasma dispersion effect of the above mentioned silicon coated nanoparticles allows doing imaging with sub wavelength resolution. The plasma dispersion effect can increase the absorption coefficient of the silicon, when illuminated with a focused laser beam and as explained above it can also tune the absorption versus scattering properties of the nanoparticle. Due to the Gaussian nature of the laser illumination which has higher intensity at its peak, the plasma dispersion effect is more significant at the center of the illumination. As a consequence, the reflected light from probe beam at the near infra-red region has a sub wavelength dip that overlaps with the location of the pump illumination peak. This dip has a higher spatial frequency than an ordinary Gaussian, which enables to achieve super resolution.

  14. Near-IR resonance Raman spectroscopy of archaerhodopsin 3: effects of transmembrane potential.

    PubMed

    Saint Clair, Erica C; Ogren, John I; Mamaev, Sergey; Russano, Daniel; Kralj, Joel M; Rothschild, Kenneth J

    2012-12-20

    Archaerhodopsin 3 (AR3) is a light driven proton pump from Halorubrum sodomense that has been used as a genetically targetable neuronal silencer and an effective fluorescent sensor of transmembrane potential. Unlike the more extensively studied bacteriorhodopsin (BR) from Halobacterium salinarum, AR3 readily incorporates into the plasma membrane of both E. coli and mammalian cells. Here, we used near-IR resonance Raman confocal microscopy to study the effects of pH and membrane potential on the AR3 retinal chromophore structure. Measurements were performed both on AR3 reconstituted into E. coli polar lipids and in vivo in E. coli expressing AR3 in the absence and presence of a negative transmembrane potential. The retinal chromophore structure of AR3 is in an all-trans configuration almost identical to BR over the entire pH range from 3 to 11. Small changes are detected in the retinal ethylenic stretching frequency and Schiff Base (SB) hydrogen bonding strength relative to BR which may be related to a different water structure near the SB. In the case of the AR3 mutant D95N, at neutral pH an all-trans retinal O-like species (O(all-trans)) is found. At higher pH a second 13-cis retinal N-like species (N(13-cis)) is detected which is attributed to a slowly decaying intermediate in the red-light photocycle of D95N. However, the amount of N(13-cis) detected is less in E. coli cells but is restored upon addition of carbonyl cyanide m-chlorophenyl hydrazone (CCCP) or sonication, both of which dissipate the normal negative membrane potential. We postulate that these changes are due to the effect of membrane potential on the N(13-cis) to M(13-cis) levels accumulated in the D95N red-light photocycle and on a molecular level by the effects of the electric field on the protonation/deprotonation of the cytoplasmic accessible SB. This mechanism also provides a possible explanation for the observed fluorescence dependence of AR3 and other microbial rhodopsins on transmembrane

  15. Internal intensity standards for heme protein UV resonance Raman studies: excitation profiles of cacodylic acid and sodium selenate.

    PubMed

    Song, S H; Asher, S A

    1991-02-01

    We examine the utility of SO4(2-), ClO4-, cacodylic acid, and SeO4(2-) as internal intensity standards for Raman spectral measurements of protein structure. We find that 0.1 M SO4(2-) and ClO4- perturb the protein tertiary structure of aquomethemoglobin (met-Hb) and its fluoride (met-HbF) and azide (met-HbN3) complexes. Changes occur for the tryptophan near-UV absorption bands, the iron spin state is altered, and the fluoride ligand affinity decreases. Concentrations of ClO4- and SO4(2-) as low as 0.1 M suppress the met-HbF quaternary R----T transition induced by the allosteric effector inositol hexaphosphate (IHP). In contrast, similar concentrations of cacodylic acid and SeO4(2-) show little effect on the hemoglobin tertiary or quaternary protein structures or upon the R----T transition induced by IHP. We measure the Raman cross sections of cacodylic acid and SeO4(2-) between 218 and 514.5 nm and find that for UV excitation they are ca. 5-fold larger than ClO4- or SO4(2-). Thus, cacodylic acid and selenate can be used at lower concentrations. Cacodylic acid and SeO4(2-) are superior Raman internal intensity standards for protein structural studies.

  16. Docking Prediction of a Water Soluble Porphyrin and Tubulin Assisted with Resonance Raman and Vibrational Mode Analysis

    NASA Astrophysics Data System (ADS)

    McMicken, Brady; Brancaleon, Lorenzo; Thomas, Robert; Parker, James

    2015-03-01

    The ability to modify protein conformation by controlling its partial unfolding may have practical applications such as diminishing its function or blocking its activity. One method used to induce partial unfolding of a protein involves the use of a photosensitizer non-covalently bound to a protein that triggers photochemical reactions upon irradiation leading to protein conformational changes. We are investigating the photoinduced conformational changes of tubulin mediated by a bound water-soluble porphyrin that acts as a photosensitizer. Analysis of how tubulin conformational changes affect its function including polymeric assembly forming microtubules is of interest to uncover the mechanism responsible for the structural change. Our approach to better understand the conformational change, we first plan to discover the binding location between the porphyrin and protein. Use of vibrational mode analysis using density functional theory and resonance Raman experiments targeting the porphyrin molecule will be used to correlate Raman peaks with vibrational modes. The relative intensities of the porphyrin bound to tubulin can be used to calculate the equilibrium geometry observed from Raman spectra. These data will provide the relative distortion of the porphyrin when bound to tubulin, which will subsequently be used in docking simulations to find the most likely binding configuration.

  17. Optical pathology of human brain metastasis of lung cancer using combined resonance Raman and spatial frequency spectroscopies

    NASA Astrophysics Data System (ADS)

    Zhou, Yan; Liu, Cheng-hui; Pu, Yang; Cheng, Gangge; Zhou, Lixin; Chen, Jun; Zhu, Ke; Alfano, Robert R.

    2016-03-01

    Raman spectroscopy has become widely used for diagnostic purpose of breast, lung and brain cancers. This report introduced a new approach based on spatial frequency spectra analysis of the underlying tissue structure at different stages of brain tumor. Combined spatial frequency spectroscopy (SFS), Resonance Raman (RR) spectroscopic method is used to discriminate human brain metastasis of lung cancer from normal tissues for the first time. A total number of thirty-one label-free micrographic images of normal and metastatic brain cancer tissues obtained from a confocal micro- Raman spectroscopic system synchronously with examined RR spectra of the corresponding samples were collected from the identical site of tissue. The difference of the randomness of tissue structures between the micrograph images of metastatic brain tumor tissues and normal tissues can be recognized by analyzing spatial frequency. By fitting the distribution of the spatial frequency spectra of human brain tissues as a Gaussian function, the standard deviation, σ, can be obtained, which was used to generate a criterion to differentiate human brain cancerous tissues from the normal ones using Support Vector Machine (SVM) classifier. This SFS-SVM analysis on micrograph images presents good results with sensitivity (85%), specificity (75%) in comparison with gold standard reports of pathology and immunology. The dual-modal advantages of SFS combined with RR spectroscopy method may open a new way in the neuropathology applications.

  18. Physical origin of Davydov splitting and resonant Raman spectroscopy of Davydov components in multilayer MoTe2

    NASA Astrophysics Data System (ADS)

    Song, Q. J.; Tan, Q. H.; Zhang, X.; Wu, J. B.; Sheng, B. W.; Wan, Y.; Wang, X. Q.; Dai, L.; Tan, P. H.

    2016-03-01

    We systematically study the high-resolution and polarized Raman spectra of multilayer (ML) MoTe2 . The layer-breathing (LB) and shear (C) modes are observed in the ultralow-frequency region, which are used to quantitatively evaluate the interlayer coupling in ML MoTe2 based on the linear chain model, in which only the nearest interlayer coupling is considered. The Raman spectra on three different substrates verify the negligible substrate effect on the phonon frequencies of ML MoTe2 . Ten excitation energies are used to measure the high-frequency modes of N -layer MoTe2 (N L MoTe2 ; N is an integer). Under the resonant excitation condition, we observe N -dependent Davydov components in ML MoTe2 , originating from the Raman-active A1'(A1g 2) modes at ˜172 c m-1 . More than two Davydov components are observed in N L MoTe2 for N >4 by Raman spectroscopy. The N -dependent Davydov components are further investigated based on the symmetry analysis. A van der Waals model only considering the nearest interlayer coupling has been proposed to well understand the Davydov splitting of high-frequency A1'(A1g 2) modes. The different resonant profiles for the two Davydov components in 3L MoTe2 indicate that proper excitation energy of ˜1.8 -2.2 eV must be chosen to observe the Davydov splitting in ML MoTe2 . Our work presents a simple way to identify layer number of ultrathin MoTe2 flakes by the corresponding number and peak position of Davydov components. Our work also provides a direct evidence from Raman spectroscopy of how the nearest van der Waals interactions significantly affect the frequency of the high-frequency intralayer phonon modes in multilayer MoTe2 and expands the understanding on the lattice vibrations and interlayer coupling of transition metal dichalcogenides and other two-dimensional materials.

  19. Selective two-photon absorptive resonance femtosecond-laser electronic-excitation tagging velocimetry.

    PubMed

    Jiang, Naibo; Halls, Benjamin R; Stauffer, Hans U; Danehy, Paul M; Gord, James R; Roy, Sukesh

    2016-05-15

    Selective two-photon absorptive resonance femtosecond-laser electronic-excitation tagging (STARFLEET), a nonseeded ultrafast-laser-based velocimetry technique, is demonstrated in reactive and nonreactive flows. STARFLEET is pumped via a two-photon resonance in N2 using 202.25 nm 100 fs light. STARFLEET greatly reduces the per-pulse energy required (30 μJ/pulse) to generate the signature FLEET emission compared to the conventional FLEET technique (1.1 mJ/pulse). This reduction in laser energy results in less energy deposited in the flow, which allows for reduced flow perturbations (reactive and nonreactive), increased thermometric accuracy, and less severe damage to materials. Velocity measurements conducted in a free jet of N2 and in a premixed flame show good agreement with theoretical velocities, and further demonstrate the significantly less intrusive nature of STARFLEET. PMID:27176968

  20. Effects of hydration levels on the bandwidth of microwave resonant absorption induced by confined acoustic vibrations

    NASA Astrophysics Data System (ADS)

    Liu, Tzu-Ming; Chen, Hung-Pin; Yeh, Shih-Chia; Wu, Chih-Yu; Wang, Chung-Hsiung; Luo, Tang-Nian; Chen, Yi-Jan; Liu, Shen-Iuan; Sun, Chi-Kuang

    2009-10-01

    We found the hydration levels on the capsid surface of viruses can affect the bandwidth of microwave resonant absorption (MRA) induced by the confined acoustic vibrations (CAV). By decreasing the pH value of solution down to 5.2 or inactivating the capsid proteins, we enhanced the surface hydrophilicity and increased the magnitude of surface potentials. Both of these surface manipulations raised the surface affinity to water molecules and narrowed the bandwidths of CAV-induced MRA. Our results validate the viscoelastic transition of hydration shells.

  1. Difference in effect of temperature on absorption and Raman spectra between all-trans-β-carotene and all-trans-retinol

    NASA Astrophysics Data System (ADS)

    Qu, Guan-Nan; Li, Shuo; Sun, Cheng-Lin; Liu, Tian-Yuan; Wu, Yong-Ling; Sun, Shang; Shan, Xiao-Ning; Men, Zhi-Wei; Chen, Wei; Li, Zuo-Wei; Gao, Shu-Qin

    2012-12-01

    Temperature dependencies (81 °C-18 °C) ofvisible absorption and Raman spectra of all-trans-β-carotene and all-trans-retinol extremely diluted in dimethyl sulfoxide are investigated in order to clarify temperature effects on different polyenes. Their absorption spectra are identified to be redshifted with temperature decreasing. Moreover, all-trans-β-carotene is more sensitive to temperature due to the presence of a longer length of conjugated system. The characteristic energy responsible for the conformational changes in all-trans-β-carotene is smaller than that in all-trans-retinol. Both of the Raman scattering cross sections increase with temperature decreasing. The results are explained with electron—phonon coupling theory and coherent weakly damped electron—lattice vibrations model.

  2. The effect of implanting boron on the optical absorption and electron paramagnetic resonance spectra of silica

    NASA Astrophysics Data System (ADS)

    Magruder, R. H.; Stesmans, A.; Weeks, R. A.; Weller, R. A.

    2008-09-01

    Silica samples (type III, Corning 7940) were implanted with B using multiple energies to produce a layer ˜600 nm thick in which the concentration of B ranged from 0.034 to 2.04 at. %. Optical absorption spectra were measured from 1.8 to 6.5 eV. Electron paramagnetic resonance (EPR) measurements were generally made at ˜20.3 and 33 GHz for sample temperatures ranging from 77 to 100 K. Based on the EPR spectra three types of defects, namely, Eγ', the E'-type 73 G split doublet (E73'), and the peroxyradical (POR) were identified. No oxygen-associated hole centers (OHCs) nor specific B-associated paramagnetic defects were detected, not even at the largest B concentration of 2.04 at. %. Unlike previous assignments, there was no correlation between the 4.83 eV optical absorption band and the observed PORs. From these results, we infer that in addition to POR, there is at least one additional Si-related state absorbing in the 4.8-4.9 eV range that is likely diamagnetic. The 5.85 eV optical absorption band is found to be due to the Eγ' and E73' centers, with, in average, quite similar oscillator strengths inferred as before. Both the optical absorption and the electron spin resonance data can be satisfactorily explained without the need for specific B-associated defect site (s). As no OHCs are detected by ESR, these do not seem to make a detectable contribution to the optical spectra.

  3. Effects of core position of locally resonant scatterers on low-frequency acoustic absorption in viscoelastic panel

    NASA Astrophysics Data System (ADS)

    Zhong, Jie; Wen, Ji-Hong; Zhao, Hong-Gang; Yin, Jian-Fei; Yang, Hai-Bin

    2015-08-01

    Locally resonant sonic materials, due to their ability to control the propagation of low-frequency elastic waves, have become a promising option for underwater sound absorption materials. In this paper, the finite element method is used to investigate the absorption characteristics of a viscoelastic panel periodically embedded with a type of infinite-long non-coaxially cylindrical locally resonant scatterers (LRSs). The effect of the core position in the coating layer of the LRS on the low-frequency (500 Hz-3000 Hz) sound absorption property is investigated. With increasing the longitudinal core eccentricity e, there occur few changes in the absorptance at the frequencies below 1500 Hz, however, the absorptance above 1500 Hz becomes gradually better and the valid absorption (with absorptance above 0.8) frequency band (VAFB) of the viscoelastic panel becomes accordingly broader. The absorption mechanism is revealed by using the displacement field maps of the viscoelastic panel and the steel slab. The results show two typical resonance modes. One is the overall resonance mode (ORM) caused by steel backing, and the other is the core resonance mode (CRM) caused by LRS. The absorptance of the viscoelastic panel by ORM is induced mainly by the vibration of the steel slab and affected little by core position. On the contrary, with increasing the core eccentricity, the CRM shifts toward high frequency band and decouples with the ORM, leading to two separate absorption peaks and the broadened VAFB of the panel. Project supported by the National Natural Science Foundation of China (Grant No. 51275519).

  4. RESONANT ABSORPTION OF TRANSVERSE OSCILLATIONS AND ASSOCIATED HEATING IN A SOLAR PROMINENCE. II. NUMERICAL ASPECTS

    SciTech Connect

    Antolin, P.; Okamoto, T. J.; Doorsselaere, T. Van; Yokoyama, T.

    2015-08-10

    Transverse magnetohydrodynamic (MHD) waves are ubiquitous in the solar atmosphere and may be responsible for generating the Sun’s million-degree outer atmosphere. However, direct evidence of the dissipation process and heating from these waves remains elusive. Through advanced numerical simulations combined with appropriate forward modeling of a prominence flux tube, we provide the observational signatures of transverse MHD waves in prominence plasmas. We show that these signatures are characterized by a thread-like substructure, strong transverse dynamical coherence, an out-of-phase difference between plane-of-the-sky motions and line-of-sight velocities, and enhanced line broadening and heating around most of the flux tube. A complex combination between resonant absorption and Kelvin–Helmholtz instabilities (KHIs) takes place in which the KHI extracts the energy from the resonant layer and dissipates it through vortices and current sheets, which rapidly degenerate into turbulence. An inward enlargement of the boundary is produced in which the turbulent flows conserve the characteristic dynamics from the resonance, therefore guaranteeing detectability of the resonance imprints. We show that the features described in the accompanying paper through coordinated Hinode and Interface Region Imaging Spectrograph observations match the numerical results well.

  5. Electromagnetically-induced-absorption resonance with high contrast and narrow width in the Hanle configuration

    NASA Astrophysics Data System (ADS)

    Brazhnikov, D. V.; Taichenachev, A. V.; Tumaikin, A. M.; Yudin, V. I.

    2014-12-01

    The method for observing the high-contrast and narrow-width resonances of electromagnetically induced absorption (EIA) in the Hanle configuration under counter-propagating pump and probe light waves is proposed. Here, as an example, we study a ‘dark’ type of atomic dipole transition {{F}\\text{g}}={1}\\to {{F}\\text{e}}={1} in D1 line of 87Rb, where usually the electromagnetically induced transparency can be observed. To obtain the EIA signal one should properly choose the polarizations of light waves and intensities. In contrast to regular schemes for observing EIA signals (under a single traveling light wave in the Hanle configuration or under a bichromatic light field consisting of two traveling waves), the proposed scheme allows one to use buffer gas for significantly improving the properties of the resonance. Also the dramatic influence of atomic transition openness on the contrast of the resonance is revealed, which is advantageous in comparison with cyclic atomic transitions. The nonlinear resonances in a probe-wave transmitted signal with contrast close to 100% and sub-kHz widths can be obtained. The results are interesting in high-resolution spectroscopy, nonlinear and magneto-optics.

  6. Dynamical rate theory of enzymatic reactions and triple-resonant coherent anti-Stokes Raman scattering microspectroscopy

    NASA Astrophysics Data System (ADS)

    Min, Wei

    Chapters 2-7 focus on physical enzymology. Despite its long history, recent single-molecule spectroscopy, among many others techniques, has generated new quantitative data that reveal unobserved features of protein dynamics and enzyme catalysis at unprecedented levels. Much of these are beyond the classic framework of transition state theory and Michalis-Menten (MM) enzyme kinetics. Due to the complexity of the problem, theoretical developments in this area have much lagged behind experiments. After an initial experimental characterization on single-molecule protein conformational fluctuations, we then develop a dynamical rate theory for enzyme catalyzed chemical reactions, from a statistical mechanics approach. Towards this goal, we formulate a two-dimensional (2D) multi-surface free energy description of the entire catalytic process that explicitly combines the concept of "fluctuating enzymes" with the MM enzyme kinetics. The outcome of this framework has two folds. On the rate theory side, going much beyond transition state theory, it connects conformational fluctuations to catalysis, allows for the interplay between energetics (e.g. Haldane's stain energy) and dynamics (e.g. Koshland's induced fit), and predicts the time dependence of single-enzyme catalysis. On the enzyme kinetics side, it gives mechanistic and unified understanding of MM and non-MM (both positive and negative cooperativity) kinetics of monomeric enzymes, in term of non-equilibrium steady state cycle on the 2D free energy surface. Chapters 8-11 present the principle and application of a new ultra-sensitive nonlinear optical microspectroscopy, femtosecond (fs) triple-resonant coherent anti-Stokes Raman scattering (CARS), in which the amplitude and phase of input fs laser pulses are optimally shaped to be in triple resonant with the molecular electronic and vibrational transitions to generate a coherent nonlinear signal beam at a new color with a highest possible efficiency. This technique

  7. Theoretical studies of resonance enhance stimulated raman scattering (RESRS) of frequency doubled Alexandrite laser wavelengths in cesium vapor. Semiannual report

    SciTech Connect

    Lawandy, N.M.

    1986-01-01

    It is well known that the presence of a real atomic level which is nearly resonant with the pump field can greatly enhance the Raman emission cross section. In order to accurately calculate the Raman gain in systems where resonance enhancement plays a dominant role, expressions for the pump and signal susceptibilities must be derived. These expressions should be valid for arbitrary field strengths in order to allow for pump and signal saturation. In addition, the theory should allow for arbitrary longitudinal and transverse relaxation rates. This latter point is extremely vital for three level atomic systems such as the alkali earth metals since they do not have population reservoirs and can have widely varying spontaneous lifetimes on the three pertinent transitions. Moreover, the dephasing rates are strong functions of electron states and are therefore also different for the three coupled pairs of levels. These considerations are not as important when molecular systems are concerned since the large reservoir of rotational states serve to produce essentially equal longitudinal recovery rates for the population of the three levels. The three level system with three arbitrary longitudinal and transverse relaxation rates was solved. There is no need for setting either pair of rates equal and the expressions are valid for arbitrarily strong fields.

  8. Spectral properties of protonated Schiff base porphyrins and chlorins. INDO-CI calculations and resonance raman studies

    SciTech Connect

    Hanson, L.K.; Chang, C.K.; Ward, B.; Callahan, P.M.; Babcock, G.T.; Head, J.D.

    1984-07-11

    INDO-CI calculations successfully reproduce the striking changes in optical spectra that occur upon protonation of mono- and disubstituted porphyrin, chlorin, and bacteriochlorin Schiff base complexes. They ascribe the changes to Schiff base C=N ..pi..* orbitals which drop in energy upon protonation and mix with and perturb the ..pi..* orbitals of the macrocycle, a result consistent with resonance Raman data. The perturbation is predicted to affect not only transition energies and intensities but also dipole moment directions. The symmetry of the porphyrin and the substitution site of the chlorin are shown to play an important role, especially in governing whether the lowest energy transition will red shift or blue shift. Blue shifts are calculated for protonation of ketimine and enamine isomers of pyrochlorophyll a (PChl). Comparison with reported optical spectra suggests that PChl a Schiff base may undergo isomerization upon protonation. Resonance Raman data on CHO, CHNR, CHNHR/sup +/, and pyrrolidine adducts of chlorin demonstrate the isolation of the peripheral C=O and C=N groups from the macrocycle ..pi.. system intramolecular hydrogen bonding, and selective enhancement of v/sub C=N/ for those species with a split Soret band. V/sub C=N/ is observed with 488.0-nm excitation into the lower-energy Soret and absent for 406.7-nm excitation into the higher-energy Soret, a result predicted by the calculations. 44 references, 10 figures, 2 tables.

  9. Theoretical studies of Resonance Enhance Stimulated Raman Scattering (RESRS) of frequency doubled Alexandrite laser wavelengths in cesium vapor

    NASA Technical Reports Server (NTRS)

    Lawandy, N. M.

    1986-01-01

    It is well known that the presence of a real atomic level which is nearly resonant with the pump field can greatly enhance the Raman emission cross section. In order to accurately calculate the Raman gain in systems where resonance enhancement plays a dominant role, expressions for the pump and signal susceptibilities must be derived. These expressions should be valid for arbitrary field strengths in order to allow for pump and signal saturation. In addition, the theory should allow for arbitrary longitudinal and transverse relaxation rates. This latter point is extremely vital for three level atomic systems such as the alkali earth metals since they do not have population reservoirs and can have widely varying spontaneous lifetimes on the three pertinent transitions. Moreover, the dephasing rates are strong functions of electron states and are therefore also different for the three coupled pairs of levels. These considerations are not as important when molecular systems are concerned since the large reservoir of rotational states serve to produce essentially equal longitudinal recovery rates for the population of the three levels. The three level system with three arbitrary longitudinal and transverse relaxation rates was solved. There is no need for setting either pair of rates equal and the expressions are valid for arbitrarily strong fields.

  10. Understanding double-resonant Raman scattering in chiral carbon nanotubes: Diameter and energy dependence of the D mode

    NASA Astrophysics Data System (ADS)

    Herziger, Felix; Vierck, Asmus; Laudenbach, Jan; Maultzsch, Janina

    2015-12-01

    We present a theoretical model to describe the double-resonant scattering process in arbitrary carbon nanotubes (CNTs). We use this approach to investigate the defect-induced D mode in CNTs and unravel the dependence of the D -mode frequency on the CNT diameter and on the energy of the resonant optical transition. Our approach is based on the symmetry of the hexagonal lattice and geometric considerations; hence the method is independent of the exact model that is chosen to describe the electronic band structure or the phonon dispersion. We finally clarify the diameter dependence of this Raman mode that has been under discussion in the past and demonstrate that, depending on the experimental conditions, in general two different dependencies can be measured. We also prove that CNTs with an arbitrary chiral index can exhibit a D mode in their Raman spectrum, in contrast to previous symmetry-based arguments. Furthermore, we give a direct quantification of the curvature-induced phonon frequency corrections of the D mode in CNTs with respect to graphite.

  11. Generating monomeric 5-coordinated microperoxidase-11 using carboxylic acid functionalized silver nanoparticles: A surface-enhanced resonance Raman scattering analysis.

    PubMed

    Kalaivani, Govindasamy; Sivanesan, Arumugam; Kannan, Ayyadurai; Sevvel, Ranganathan

    2016-10-01

    Microperoxidase-11 (MP-11), a heme undecapeptide obtained by proteolytic digestion of cytochrome c, resembles peroxidase enzyme when its heme center is 5-coordinated with a vacant sixth coordination site. However, MP-11 always tends to aggregate in both solution and on surface and eventually forms the 6-coordinated heme. Thus, the present study investigates the immobilization strategy of MP-11 on nanoparticle surface in order to generate monomeric 5-coordinated MP-11 and make them as an efficient biocatalyst. The powerful surface-enhanced resonance Raman scattering (SERRS) technique is being employed to attain the detailed structural information of the catalytic site i.e., the heme center. The localized surface plasmon resonance (LSPR) tuned and 6-mercaptohexanoic acid (MHA) functionalized silver nanoparticles (Ag@MHA NPs) are used as Raman signal amplifier. The outcome of the SERRS study unambiguously portrays the existence of monomeric 5-coordinated MP-11 on Ag@MHA NPs surface. Here, Ag@MHA NPs plays a dual role of providing a platform to create monomeric 5-coordinated MP-11 and to load large number of MP-11 due to its high surface to volume ratio. Further, the electrostatic interaction between Ag@MHA NPs and MP-11 leads to instantaneous SERRS signal enhancement with a Raman enhancement factor (EFSERS) of 2.36×10(6). Langmuir adsorption isotherm has been employed for the adsorption of MP-11 on Ag@MHA NPs surface, which provides the real surface coverage (ΓS(*)) and equilibrium constant (K) value of 1.54nm and 5×10(11)M(-1). Furthermore, the peroxidase activity of MP-11 has been demonstrated through electrocatalytic oxygen reduction reaction. PMID:27434160

  12. Generating monomeric 5-coordinated microperoxidase-11 using carboxylic acid functionalized silver nanoparticles: A surface-enhanced resonance Raman scattering analysis.

    PubMed

    Kalaivani, Govindasamy; Sivanesan, Arumugam; Kannan, Ayyadurai; Sevvel, Ranganathan

    2016-10-01

    Microperoxidase-11 (MP-11), a heme undecapeptide obtained by proteolytic digestion of cytochrome c, resembles peroxidase enzyme when its heme center is 5-coordinated with a vacant sixth coordination site. However, MP-11 always tends to aggregate in both solution and on surface and eventually forms the 6-coordinated heme. Thus, the present study investigates the immobilization strategy of MP-11 on nanoparticle surface in order to generate monomeric 5-coordinated MP-11 and make them as an efficient biocatalyst. The powerful surface-enhanced resonance Raman scattering (SERRS) technique is being employed to attain the detailed structural information of the catalytic site i.e., the heme center. The localized surface plasmon resonance (LSPR) tuned and 6-mercaptohexanoic acid (MHA) functionalized silver nanoparticles (Ag@MHA NPs) are used as Raman signal amplifier. The outcome of the SERRS study unambiguously portrays the existence of monomeric 5-coordinated MP-11 on Ag@MHA NPs surface. Here, Ag@MHA NPs plays a dual role of providing a platform to create monomeric 5-coordinated MP-11 and to load large number of MP-11 due to its high surface to volume ratio. Further, the electrostatic interaction between Ag@MHA NPs and MP-11 leads to instantaneous SERRS signal enhancement with a Raman enhancement factor (EFSERS) of 2.36×10(6). Langmuir adsorption isotherm has been employed for the adsorption of MP-11 on Ag@MHA NPs surface, which provides the real surface coverage (ΓS(*)) and equilibrium constant (K) value of 1.54nm and 5×10(11)M(-1). Furthermore, the peroxidase activity of MP-11 has been demonstrated through electrocatalytic oxygen reduction reaction.

  13. Structure-induced resonant tail-state regime absorption in polymer: fullerene bulk-heterojunction solar cells

    NASA Astrophysics Data System (ADS)

    Pfadler, Thomas; Kiel, Thomas; Stärk, Martin; Werra, Julia F. M.; Matyssek, Christian; Sommer, Daniel; Boneberg, Johannes; Busch, Kurt; Weickert, Jonas; Schmidt-Mende, Lukas

    2016-05-01

    In this work, we present resonant tail-state regime absorption enhanced organic photovoltaics. We combine periodically structured TiO2 bottom electrodes with P3HT-PCBM bulk-heterojunction solar cells in an inverted device configuration. The wavelength-scale patterns are transferred to the electron-selective bottom electrodes via direct laser interference patterning, a fast method compatible with roll-to-roll processing. Spectroscopic and optoelectronic device measurements suggest polarization-dependent absorption enhancement along with photocurrent generation unambiguously originating from the population of tail states. We discuss the effects underlying these absorption patterns with the help of electromagnetic simulations using the discontinuous Galerkin time domain method. For this, we focus on the total absorption spectra along with spatially resolved power loss densities. Our simulations stress the tunability of the absorption resonances towards arbitrary wavelength regions.

  14. Sound Absorption of a 2DOF Resonant Liner with Negative Bias Flow

    NASA Technical Reports Server (NTRS)

    Ahuja, K. K.; Cataldi, P.; Gaeta, R. J., Jr.

    2000-01-01

    This report describes an experimental study conducted to determine the effect of negative bias flow on the sound absorption of a two degree-of-freedom liner. The backwall for the liner was designed to act as a double-Helmholtz resonator so as to act as a hard wall at all frequencies except at its resonant frequencies. The effect of bias flow is investigated for a buried septum porosity of 2% and 19.5% for bias flow orifice Mach numbers up to 0.311. The bias flow appears to modify the resistance and reactance of the backwall alone at lower frequencies up to about 2 kHz, with marginal effects at higher frequencies. Absorption coefficients close to unity are achieved for a frequency range of 500 - 4000 Hz for the overall liner for a septum porosity of 2% and orifice Mach number of 0.128. Insertion loss tests performed in a flow duct facility for grazing flow Mach numbers up to 0.2 and septum Mach numbers up to 0.15 showed that negative bias flow can increase insertion loss by as much as 10 dB at frequencies in the range of 500 D 1400 Hz compared to no grazing flow. The effectiveness of the negative bias flow is diminished as the grazing flow velocity is increased.

  15. RESONANT ABSORPTION OF TRANSVERSE OSCILLATIONS AND ASSOCIATED HEATING IN A SOLAR PROMINENCE. I. OBSERVATIONAL ASPECTS

    SciTech Connect

    Okamoto, Takenori J.; Pontieu, Bart De; Doorsselaere, Tom Van; Yokoyama, Takaaki

    2015-08-10

    Transverse magnetohydrodynamic waves have been shown to be ubiquitous in the solar atmosphere and can, in principle, carry sufficient energy to generate and maintain the Sun’s million-degree outer atmosphere or corona. However, direct evidence of the dissipation process of these waves and subsequent heating has not yet been directly observed. Here we report on high spatial, temporal, and spectral resolution observations of a solar prominence that show a compelling signature of so-called resonant absorption, a long hypothesized mechanism to efficiently convert and dissipate transverse wave energy into heat. Aside from coherence in the transverse direction, our observations show telltale phase differences around 180° between transverse motions in the plane-of-sky and line-of-sight velocities of the oscillating fine structures or threads, and also suggest significant heating from chromospheric to higher temperatures. Comparison with advanced numerical simulations support a scenario in which transverse oscillations trigger a Kelvin–Helmholtz instability (KHI) at the boundaries of oscillating threads via resonant absorption. This instability leads to numerous thin current sheets in which wave energy is dissipated and plasma is heated. Our results provide direct evidence for wave-related heating in action, one of the candidate coronal heating mechanisms.

  16. Resonant absorption of kink magnetohydrodynamic waves by a magnetic twist in coronal loops

    NASA Astrophysics Data System (ADS)

    Ebrahimi, Zanyar; Karami, Kayoomars

    2016-10-01

    There is ample evidence of twisted magnetic structures in the solar corona. This motivates us to consider the magnetic twist as the cause of Alfvén frequency continuum in coronal loops, which can support the resonant absorption as a rapid damping mechanism for the observed coronal kink magnetohydrodynamic (MHD) oscillations. We model a coronal loop with a straight cylindrical magnetic flux tube, which has constant but different densities in the interior and exterior regions. The magnetic field is assumed to be constant and aligned with the cylinder axis everywhere except for a thin layer near the boundary of the flux tube, which has an additional small magnetic field twist. Then, we investigate a number of possible instabilities that may arise in our model. In the thin tube thin boundary approximation, we derive the dispersion relation and solve it analytically to obtain the frequencies and damping rates of the fundamental (l = 1) and first/second overtone (l = 2, 3) kink (m = 1) MHD modes. We conclude that the resonant absorption by the magnetic twist can justify the rapid damping of kink MHD waves observed in coronal loops. Furthermore, the magnetic twist in the inhomogeneous layer can cause deviations from P1/P2 = 2 and P1/P3 = 3, which are comparable with the observations.

  17. Mapping the amide I absorption in single bacteria and mammalian cells with resonant infrared nanospectroscopy

    NASA Astrophysics Data System (ADS)

    Baldassarre, L.; Giliberti, V.; Rosa, A.; Ortolani, M.; Bonamore, A.; Baiocco, P.; Kjoller, K.; Calvani, P.; Nucara, A.

    2016-02-01

    Infrared (IR) nanospectroscopy performed in conjunction with atomic force microscopy (AFM) is a novel, label-free spectroscopic technique that meets the increasing request for nano-imaging tools with chemical specificity in the field of life sciences. In the novel resonant version of AFM-IR, a mid-IR wavelength-tunable quantum cascade laser illuminates the sample below an AFM tip working in contact mode, and the repetition rate of the mid-IR pulses matches the cantilever mechanical resonance frequency. The AFM-IR signal is the amplitude of the cantilever oscillations driven by the thermal expansion of the sample after absorption of mid-IR radiation. Using purposely nanofabricated polymer samples, here we demonstrate that the AFM-IR signal increases linearly with the sample thickness t for t \\gt 50 nm, as expected from the thermal expansion model of the sample volume below the AFM tip. We then show the capability of the apparatus to derive information on the protein distribution in single cells through mapping of the AFM-IR signal related to the amide-I mid-IR absorption band at 1660 cm-1. In Escherichia Coli bacteria we see how the topography changes, observed when the cell hosts a protein over-expression plasmid, are correlated with the amide I signal intensity. In human HeLa cells we obtain evidence that the protein distribution in the cytoplasm and in the nucleus is uneven, with a lateral resolution better than 100 nm.

  18. Mapping the amide I absorption in single bacteria and mammalian cells with resonant infrared nanospectroscopy.

    PubMed

    Baldassarre, L; Giliberti, V; Rosa, A; Ortolani, M; Bonamore, A; Baiocco, P; Kjoller, K; Calvani, P; Nucara, A

    2016-02-19

    Infrared (IR) nanospectroscopy performed in conjunction with atomic force microscopy (AFM) is a novel, label-free spectroscopic technique that meets the increasing request for nano-imaging tools with chemical specificity in the field of life sciences. In the novel resonant version of AFM-IR, a mid-IR wavelength-tunable quantum cascade laser illuminates the sample below an AFM tip working in contact mode, and the repetition rate of the mid-IR pulses matches the cantilever mechanical resonance frequency. The AFM-IR signal is the amplitude of the cantilever oscillations driven by the thermal expansion of the sample after absorption of mid-IR radiation. Using purposely nanofabricated polymer samples, here we demonstrate that the AFM-IR signal increases linearly with the sample thickness t for t > 50 nm, as expected from the thermal expansion model of the sample volume below the AFM tip. We then show the capability of the apparatus to derive information on the protein distribution in single cells through mapping of the AFM-IR signal related to the amide-I mid-IR absorption band at 1660 cm(-1). In Escherichia Coli bacteria we see how the topography changes, observed when the cell hosts a protein over-expression plasmid, are correlated with the amide I signal intensity. In human HeLa cells we obtain evidence that the protein distribution in the cytoplasm and in the nucleus is uneven, with a lateral resolution better than 100 nm.

  19. Plasmon resonance and perfect light absorption in subwavelength trench arrays etched in gallium-doped zinc oxide film

    SciTech Connect

    Hendrickson, Joshua R. Leedy, Kevin; Cleary, Justin W.; Vangala, Shivashankar; Nader, Nima; Guo, Junpeng

    2015-11-09

    Near-perfect light absorption in subwavelength trench arrays etched in highly conductive gallium-doped zinc oxide films was experimentally observed in the mid infrared regime. At wavelengths corresponding to the resonant excitation of surface plasmons, up to 99% of impinging light is efficiently trapped and absorbed in the periodic trenches. Scattering cross sectional calculations reveal that each individual trench acts like a vertical split ring resonator with a broad plasmon resonance spectrum. The coupling of these individual plasmon resonators in the grating structure leads to enhanced photon absorption and significant resonant spectral linewidth narrowing. Ellipsometry measurements taken before and after device fabrication result in different permittivity values for the doped zinc oxide material, indicating that localized annealing occurred during the plasma etching process due to surface heating. Simulations, which incorporate a 50 nm annealed region at the zinc oxide surface, are in a good agreement with the experimental results.

  20. Plasmon resonance and perfect light absorption in subwavelength trench arrays etched in gallium-doped zinc oxide film

    NASA Astrophysics Data System (ADS)

    Hendrickson, Joshua R.; Vangala, Shivashankar; Nader, Nima; Leedy, Kevin; Guo, Junpeng; Cleary, Justin W.

    2015-11-01

    Near-perfect light absorption in subwavelength trench arrays etched in highly conductive gallium-doped zinc oxide films was experimentally observed in the mid infrared regime. At wavelengths corresponding to the resonant excitation of surface plasmons, up to 99% of impinging light is efficiently trapped and absorbed in the periodic trenches. Scattering cross sectional calculations reveal that each individual trench acts like a vertical split ring resonator with a broad plasmon resonance spectrum. The coupling of these individual plasmon resonators in the grating structure leads to enhanced photon absorption and significant resonant spectral linewidth narrowing. Ellipsometry measurements taken before and after device fabrication result in different permittivity values for the doped zinc oxide material, indicating that localized annealing occurred during the plasma etching process due to surface heating. Simulations, which incorporate a 50 nm annealed region at the zinc oxide surface, are in a good agreement with the experimental results.

  1. Microwave absorption of a TiO2@PPy hybrid and its nonlinear dielectric resonant attenuation mechanism

    NASA Astrophysics Data System (ADS)

    Jiang, Wanchun; Wang, Yu; Xie, Aming; Wu, Fan

    2016-09-01

    We report on a high-performance electromagnetic absorption material (TiO2@PPy) developed via a facile in situ polymerization process, where lower than  -60 dB maximum absorption and 6.56 dB effective absorption bandwidth (lower than  -10 dB) can be obtained under low thickness. The excellent electromagnetic wave absorption ability is attributed to the synthetic effect of improved impedance matching and the dual loss mechanism, which originates from the polarization relaxations of dipoles induced by vacancy defects and a conductive network constructed by aerogels. An equivalent circuit model is established to explicate the nonlinear dielectric resonant attenuation mechanism.

  2. Time-resolved postdischarge absolute silicon monoxide density measurement by resonant absorption spectroscopy in a nonthermal atmospheric plasma

    SciTech Connect

    Motret, Olivier; Coursimault, Fabien; Pouvesle, Jean-Michel

    2006-11-01

    In this study we present the technique of resonant absorption spectroscopy diagnostic developed to estimate the density of silicon monoxide (SiO) molecules during the postdischarge of an atmospheric dielectric barrier discharge plasma. The ultraviolet (0,0) rovibrational band of the SiO(A {sup 1}{pi}-X {sup 1}{sigma}{sup +}) electronic transition was investigated. Effective values of absorption coefficient and absorption cross section for the rotational transitions under consideration were calculated. The SiO concentration was estimated by comparison between experimental and computed spectra. The self-absorption in the probe reactor was taken into account in the computed spectra.

  3. High-pressure x-ray diffraction, absorption, luminescence, and Raman-scattering study of Cs{sub 2}MoS{sub 4}

    SciTech Connect

    Lorenz, B.; Orgzall, I.; Dorhout, P.K.; Raymond, C.C.; Brister, K.; Weishaupt, K.; DAdamo, R.; Hochheimer, H.D.

    1997-02-01

    Cesium thiomolybdate, Cs{sub 2}MoS{sub 4}, has been investigated at pressures up to 12 GPa. Two phase transitions have been detected by absorption measurements, Raman spectroscopy, and energy dispersive x-ray diffraction. The first phase transition to a monoclinic phase II [a=14.061(9) {Angstrom}, b=11.552(7) {Angstrom}, c=9.852(6) {Angstrom}, {beta}=97.14(6){degree}] has been observed at 8.0 GPa. The second transition at 9.7 GPa has been observed from the monoclinic phase II to an orthorhombic phase III [a=12.085(4) {Angstrom}, b=15.707(6) {Angstrom}, c=11.828(5) {Angstrom}]. Absorption and luminescence measurements have indicated an increase in the absorption edge energy with pressure up to {approximately}3 GPa. At pressures greater than 3.5 GPa, the absorption energy decreases. Raman spectroscopy has revealed a low-frequency phonon mode with a negative pressure shift in the low-pressure phase I. The pressure-temperature phase diagram has been determined up to 250{degree}C. The transition pressures decrease linearly with slopes of {approximately}{minus}0.013 GPa/{degree}C. Models for the pressure-induced structural and electronic transitions are proposed. {copyright} {ital 1997} {ital The American Physical Society}

  4. Shifting of infrared radiation using rotational raman resonances in diatomic molecular gases

    DOEpatents

    Kurnit, Norman A.

    1980-01-01

    A device for shifting the frequency of infrared radiation from a CO.sub.2 laser by stimulated Raman scattering in either H.sub.2 or D.sub.2. The device of the preferred embodiment comprises an H.sub.2 Raman laser having dichroic mirrors which are reflective for 16 .mu.m radiation and transmittive for 10 .mu.m, disposed at opposite ends of an interaction cell. The interaction cell contains a diatomic molecular gas, e.g., H.sub.2, D.sub.2, T.sub.2, HD, HT, DT and a capillary waveguide disposed within the cell. A liquid nitrogen jacket is provided around the capillary waveguide for the purpose of cooling. In another embodiment the input CO.sub.2 radiation is circularly polarized using a Fresnel rhomb .lambda./4 plate and applied to an interaction cell of much longer length for single pass operation.

  5. Multiple relaxation and inhomogeneous broadening in resonance enhanced Raman scattering - Application to tunable infrared generation

    NASA Technical Reports Server (NTRS)

    Ryan, J. C.; Lawandy, N. M.

    1989-01-01

    The solutions for the imaginary susceptibility of the Raman field transition with arbitrary relaxation rates and field strengths are examined for differing sets of relaxation rates with emphasis on alkali metal vapors which have spontaneous emission dominated relaxation. The model is further expanded to include Doppler broadening and used to predict the peak gain as a function of detuning for a frequency doubled alexandrite laser-pumped cesium vapor gain cell.

  6. Optical fibre probe NIR Raman measurements in ambient light and in combination with a tactile resonance sensor for possible cancer detection.

    PubMed

    Nyberg, Morgan; Ramser, Kerstin; Lindahl, Olof A

    2013-07-21

    First measurements on a combined instrument with a thin fibre optic Raman probe mounted inside a hollow tactile resonance sensor have been performed in ambient light on porcine tissue. The ambient fluorescent light was removed successfully from the spectra. The stiffness and the biomolecular composition of the tissue were analysed.

  7. Resonance Raman spectra of the (2Fe-2S) clusters of the Rieske protein from thermus and phthalate dioxygenase from pseudomonas

    SciTech Connect

    Kuila, D.; Fee, J.A.; Schoonover, J.R.; Woodruff, W.H.

    1987-03-04

    In this paper a resonance Raman (RR) study of novel iron-sulfur-nitrogen clusters is described which provides evidence for an asymmetric distribution of Cys and N ligands on the cluster. The systems examined were Thermus Rieske protein (TRP) and phthalate dioxygenase (PDO) from Pseudomonas cepacia; the RR spectra of these proteins are compared to that of spinach ferredoxin (SFD).

  8. The use of ultraviolet resonance Raman spectroscopy in the analysis of ionizing-radiation-induced damage in DNA.

    PubMed

    Shaw, C P; Jirasek, A

    2009-04-01

    Ultraviolet resonance Raman spectroscopy (UVRRS) was used to determine damage done in both calf-thymus DNA (CT-DNA) and a short stranded DNA oligomer (SS-DNA) due to ionizing radiation from a medical (60)Co radiation therapy unit used in the treatment of cancer. Spectra were acquired at incident UV wavelengths of 248, 257, and 264 nm in order to utilize the differences in UVRR cross-sections of the bases with wavelength. Through the analysis of difference spectra between irradiated and unirradiated DNA at each of the incident UV wavelengths, damage to CT- and SS-DNA was observed and identified. Significant radiation-induced increases in the difference spectra of the CT-DNA indicated disruption of the stable, stacked structure of its bases, as well as the disruption of Watson-Crick hydrogen bonds between the base pairs. Base unstacking was not as evident in the SS-DNA, while radiation-induced spectral decreases suggest disruption of the structure of the nucleotides. As demonstrated, UVRRS has the ability to highlight contributions from specific moieties with the use of varying incident UV wavelengths, thus enhancing the already information-rich content of the Raman spectra.

  9. Resonance Raman and excitation energy dependent charge transfer mechanism in halide-substituted hybrid perovskite solar cells.

    PubMed

    Park, Byung-wook; Jain, Sagar M; Zhang, Xiaoliang; Hagfeldt, Anders; Boschloo, Gerrit; Edvinsson, Tomas

    2015-02-24

    Organo-metal halide perovskites (OMHPs) are materials with attractive properties for optoelectronics. They made a recent introduction in the photovoltaics world by methylammonium (MA) lead triiodide and show remarkably improved charge separation capabilities when chloride and bromide are added. Here we show how halide substitution in OMHPs with the nominal composition CH3NH3PbI2X, where X is I, Br, or Cl, influences the morphology, charge quantum yield, and local interaction with the organic MA cation. X-ray diffraction and photoluminescence data demonstrate that halide substitution affects the local structure in the OMHPs with separate MAPbI3 and MAPbCl3 phases. Raman spectroscopies as well as theoretical vibration calculations reveal that this at the same time delocalizes the charge to the MA cation, which can liberate the vibrational movement of the MA cation, leading to a more adaptive organic phase. The resonance Raman effect together with quantum chemical calculations is utilized to analyze the change in charge transfer mechanism upon electronic excitation and gives important clues for the mechanism of the much improved photovoltage and photocurrent also seen in the solar cell performance for the materials when chloride compounds are included in the preparation. PMID:25668059

  10. A new combined nuclear magnetic resonance and Raman spectroscopic probe applied to in situ investigations of catalysts and catalytic processes

    SciTech Connect

    Camp, Jules C. J.; Mantle, Michael D.; York, Andrew P. E.; McGregor, James

    2014-06-15

    Both Raman and nuclear magnetic resonance (NMR) spectroscopies are valuable analytical techniques capable of providing mechanistic information and thereby providing insights into chemical processes, including catalytic reactions. Since both techniques are chemically sensitive, they yield not only structural information but also quantitative analysis. In this work, for the first time, the combination of the two techniques in a single experimental apparatus is reported. This entailed the design of a new experimental probe capable of recording simultaneous measurements on the same sample and/or system of interest. The individual datasets acquired by each spectroscopic method are compared to their unmodified, stand-alone equivalents on a single sample as a means to benchmark this novel piece of equipment. The application towards monitoring reaction progress is demonstrated through the evolution of the homogeneous catalysed metathesis of 1‑hexene, with both experimental techniques able to detect reactant consumption and product evolution. This is extended by inclusion of magic angle spinning (MAS) NMR capabilities with a custom made MAS 7 mm rotor capable of spinning speeds up to 1600 Hz, quantified by analysis of the spinning sidebands of a sample of KBr. The value of this is demonstrated through an application involving heterogeneous catalysis, namely the metathesis of 2-pentene and ethene. This provides the added benefit of being able to monitor both the reaction progress (by NMR spectroscopy) and also the structure of the catalyst (by Raman spectroscopy) on the very same sample, facilitating the development of structure-performance relationships.

  11. Rapid analysis of malachite green and leucomalachite green in fish muscles with surface-enhanced resonance Raman scattering.

    PubMed

    Zhang, Yuanyuan; Yu, Wansong; Pei, Lu; Lai, Keqiang; Rasco, Barbara A; Huang, Yiqun

    2015-02-15

    Surface-enhanced resonance Raman scattering (SERRS) coupled with gold nanospheres was applied for rapid analysis of the hazardous substances malachite green (MG) and leucomalachite green (LMG) in fish muscle tissues. The lowest concentration of MG that could be detected was 0.5ngmL(-1) with high linear correlation (R(2)=0.970-0.998) between MG concentration and intensities of characteristic Raman peaks. A simplified sample preparation method taking less than 1h for recovering MG and LMG in fish fillets was developed for SERRS analysis, and 4-8 samples could be handled in parallel. MG and LMG could be detected in extracts of tilapia fish fillets at as low as 2ngg(-1) with SERRS and a simple principle component analysis method. For six other fish species, the lowest detectable concentration of MG ranged from 1ngg(-1) to 10ngg(-1). This study provides a new sensitive approach for the detection of trace amounts of the prohibited drugs MG and LMG in muscle food, which has the potential for rapidly screening a large number of samples. PMID:25236201

  12. Rapid analysis of malachite green and leucomalachite green in fish muscles with surface-enhanced resonance Raman scattering.

    PubMed

    Zhang, Yuanyuan; Yu, Wansong; Pei, Lu; Lai, Keqiang; Rasco, Barbara A; Huang, Yiqun

    2015-02-15

    Surface-enhanced resonance Raman scattering (SERRS) coupled with gold nanospheres was applied for rapid analysis of the hazardous substances malachite green (MG) and leucomalachite green (LMG) in fish muscle tissues. The lowest concentration of MG that could be detected was 0.5ngmL(-1) with high linear correlation (R(2)=0.970-0.998) between MG concentration and intensities of characteristic Raman peaks. A simplified sample preparation method taking less than 1h for recovering MG and LMG in fish fillets was developed for SERRS analysis, and 4-8 samples could be handled in parallel. MG and LMG could be detected in extracts of tilapia fish fillets at as low as 2ngg(-1) with SERRS and a simple principle component analysis method. For six other fish species, the lowest detectable concentration of MG ranged from 1ngg(-1) to 10ngg(-1). This study provides a new sensitive approach for the detection of trace amounts of the prohibited drugs MG and LMG in muscle food, which has the potential for rapidly screening a large number of samples.

  13. A new combined nuclear magnetic resonance and Raman spectroscopic probe applied to in situ investigations of catalysts and catalytic processes.

    PubMed

    Camp, Jules C J; Mantle, Michael D; York, Andrew P E; McGregor, James

    2014-06-01

    Both Raman and nuclear magnetic resonance (NMR) spectroscopies are valuable analytical techniques capable of providing mechanistic information and thereby providing insights into chemical processes, including catalytic reactions. Since both techniques are chemically sensitive, they yield not only structural information but also quantitative analysis. In this work, for the first time, the combination of the two techniques in a single experimental apparatus is reported. This entailed the design of a new experimental probe capable of recording simultaneous measurements on the same sample and/or system of interest. The individual datasets acquired by each spectroscopic method are compared to their unmodified, stand-alone equivalents on a single sample as a means to benchmark this novel piece of equipment. The application towards monitoring reaction progress is demonstrated through the evolution of the homogeneous catalysed metathesis of 1‑hexene, with both experimental techniques able to detect reactant consumption and product evolution. This is extended by inclusion of magic angle spinning (MAS) NMR capabilities with a custom made MAS 7 mm rotor capable of spinning speeds up to 1600 Hz, quantified by analysis of the spinning sidebands of a sample of KBr. The value of this is demonstrated through an application involving heterogeneous catalysis, namely the metathesis of 2-pentene and ethene. This provides the added benefit of being able to monitor both the reaction progress (by NMR spectroscopy) and also the structure of the catalyst (by Raman spectroscopy) on the very same sample, facilitating the development of structure-performance relationships.

  14. Guided-Mode Resonance Grating with Self-Assembled Silver Nanoparticles for Surface-Enhanced Raman Scattering Spectroscopy

    PubMed Central

    Chong, Xinyuan; Fan, Donglei; Chakravarty, Swapnajit; Wang, Zheng; Chen, Ray T.; Wang, Alan X.

    2016-01-01

    We designed and fabricated guided-mode resonance (GMR) gratings on indium-tin-oxide (ITO) thin film to generate a significantly enhanced local electric field for surface-enhanced Raman scattering (SERS) spectroscopy. Ag nanoparticles (NPs) were self-assembled onto the surface of the grating, which can provide a large amount of “hot-spots” for SERS sensing. The ITO gratings also exhibit excellent tolerance to fabrication deviations due to the large refractive index contrast of the ITO grating. Quantitative experimental results of 5,5’-dithiobis(2-nitrobenzoic acid) (DTNB) demonstrate the best enhancement factor of ~14× on ITO gratings when compared with Ag NPs on a flat ITO film, and the limit of detection (LOD) of DTNB is as low as 10 pM. PMID:26958546

  15. The cell-cycle dependence of the spectra of proliferating normal and neoplastic single cells using confocal resonance Raman microspectroscopy

    NASA Astrophysics Data System (ADS)

    Boydston-White, Susie; Liu, Cheng-Hui; Alfano, Robert R.

    2013-03-01

    Confocal resonance Raman (RR) spectra were collected from single proliferating cells and analyzed to detect spectral patterns that are cell-cycle dependent, as a consequence of cellular proliferation — normal or abnormal. The cells' biochemical age at each time point was confirmed by immunohistochemical staining to identify the presence or absence of cellular components that appear and/or disappear as the cells proceed through the cell-cycle. The RR spectra were collected and compared for each time point as the cells proceeded through the cell cycle to determine what spectral vibrational patterns are cell-cycle dependent. In this study, the question is whether the cell-cycle dependent RR spectral patterns of the vibrational modes observed in proliferating normal and neoplastic single cells are due to a state of cancer or are simply the consequences of the cells' changing internal biochemistry due to the process of cellular proliferation --- normal or abnormal.

  16. Resonance Raman spectrum of the allyl-d5 radical and the force field analysis of the allyl radical

    NASA Astrophysics Data System (ADS)

    Liu, Xianming; Getty, James D.; Kelly, Peter B.

    1993-08-01

    Resonance Raman spectra of the allyl-d5 radical have been obtained with excitation between 247 and 223 nm. Analysis of the spectra yields the first observation of fundamental frequencies, nu4, nu5, and nu7 and overtone frequencies 2nu9, 2nu10, and 2nu12. The new vibrational data are combined with previously observed frequencies of allyl-h5 and allyl-d5 radical to produce the force field analysis for the allyl radical. This study suggests reassignment of several previously observed infrared (IR) bands. Experimental frequencies and assignments for allyl-h5 and allyl-d5 are compared with results from ab initio calculations. Force constants obtained in the present work are compared with the force constants of other sp2 hybridization molecules such as benzene, allene, and ethylene.

  17. Change of electrical conductivity of Ar welding arc under resonant absorption of laser radiation

    NASA Astrophysics Data System (ADS)

    Kozakov, R.; Emde, B.; Pipa, A. V.; Huse, M.; Uhrlandt, D.; Hermsdorf, J.; Wesling, V.

    2015-03-01

    Experimental investigations of the impact of resonant laser absorption by a tungsten inert gas welding arc in argon are presented. The intensity increase of the arc’s radiation between the laser entrance height and the anode are observed, as well as the variation of arc voltage due to the presence of the laser beam. High-speed camera recordings from different directions combined with absolutely calibrated spectroscopic measurements allow the reconstruction of the three-dimensional emission coefficient profiles without the assumption of axial symmetry. The obtained data are evaluated within the framework of local thermodynamic equilibrium. The local increase in the temperature and conductivity due to the influence of the laser is determined. Changes in the electrical conductivity obtained from the optical measurements coincide well with the measured voltage drop, and show significant redistribution of the current density profile near the anode in particular.

  18. Damping of magnetohydrodynamic waves by resonant absorption in the solar atmosphere.

    PubMed

    Goossens, M; Andries, J; Arregui, I

    2006-02-15

    In the last decade we have been overwhelmed by an avalanche of discoveries of magnetohydrodynamic (MHD) waves by the Solar and Heliospheric Observatory and Transition Region and Coronal Explorer observatories. Both standing and propagating versions of fast magnetoacoustic and slow magnetoacoustic MHD waves have been detected. Information on the damping times and damping distances of these waves is less detailed and less accurate than that on periods and amplitudes. Nevertheless, observations show the damping times and damping lengths are often short. Also, different types of MHD waves in different types of magnetic structures likely require different damping mechanisms. The phenomenon of fast damping is well documented for the standing fast magnetosonic kink waves in coronal loops. This paper concentrates on standing fast magnetosonic waves. It reports on results on periods and damping times due to resonant absorption in one-dimensional and two-dimensional models of coronal loops. Special attention is given to multiple modes. PMID:16414889

  19. Resonance-induced absorption enhancement in colloidal quantum dot solar cells using nanostructured electrodes.

    PubMed

    Mahpeykar, Seyed Milad; Xiong, Qiuyang; Wang, Xihua

    2014-10-20

    The application of nanostructured indium-doped tin oxide (ITO) electrodes as diffraction gratings for light absorption enhancement in colloidal quantum dot solar cells is numerically investigated using finite-difference time-domain (FDTD) simulation. Resonant coupling of the incident diffracted light with supported waveguide modes in light absorbing layer at particular wavelengths predicted by grating far-field projection analysis is shown to provide superior near-infrared light trapping for nanostructured devices as compared to the planar structure. Among various technologically feasible nanostructures, the two-dimensional nano-branch array is demonstrated as the most promising polarization-independent structure and proved to be able to maintain its performance despite structural imperfections common in fabrication. PMID:25607315

  20. Resonance-induced absorption enhancement in colloidal quantum dot solar cells using nanostructured electrodes.

    PubMed

    Mahpeykar, Seyed Milad; Xiong, Qiuyang; Wang, Xihua

    2014-10-20

    The application of nanostructured indium-doped tin oxide (ITO) electrodes as diffraction gratings for light absorption enhancement in colloidal quantum dot solar cells is numerically investigated using finite-difference time-domain (FDTD) simulation. Resonant coupling of the incident diffracted light with supported waveguide modes in light absorbing layer at particular wavelengths predicted by grating far-field projection analysis is shown to provide superior near-infrared light trapping for nanostructured devices as compared to the planar structure. Among various technologically feasible nanostructures, the two-dimensional nano-branch array is demonstrated as the most promising polarization-independent structure and proved to be able to maintain its performance despite structural imperfections common in fabrication.

  1. Observing random walks of atoms in buffer gas through resonant light absorption

    NASA Astrophysics Data System (ADS)

    Aoki, Kenichiro; Mitsui, Takahisa

    2016-07-01

    Using resonant light absorption, random-walk motions of rubidium atoms in nitrogen buffer gas are observed directly. The transmitted light intensity through atomic vapor is measured, and its spectrum is obtained, down to orders of magnitude below the shot-noise level to detect fluctuations caused by atomic motions. To understand the measured spectra, the spectrum for atoms performing random walks in a Gaussian light beam is computed, and its analytical form is obtained. The spectrum has 1 /f2 (f is frequency) behavior at higher frequencies, crossing over to a different, but well-defined, behavior at lower frequencies. The properties of this theoretical spectrum agree excellently with the measured spectrum. This understanding also enables us to obtain the diffusion constant, the photon cross section of atoms in buffer gas, and the atomic number density from a single spectral measurement. We further discuss other possible applications of our experimental method and analysis.

  2. A combination of dynamic light scattering and polarized resonance Raman scattering applied in the study of Arenicola Marina extracellular hemoglobin.

    PubMed

    Jernshøj, K D; Hassing, S; Olsen, L F

    2013-08-14

    Arenicola Marina extracellular hemoglobin (Hbl Hb) is considered to be a promising candidate as a blood substitute. To entangle some of the properties of extracellular giant hexagonal bilayer hemoglobin (Hbl Hb) of Arenicola Marina, we combined polarized resonance Raman scattering (532 nm excitation) with dynamic light scattering (DLS) (632.8 nm). An analysis of the depolarization ratio of selected a(2g) skeletal modes of the heme in native Hbl Hb and porcine Hb, shows that the distortion of the heme group away from its ideal fourfold symmetry is much smaller for heme groups bound in the Hbl Hb than for heme groups bound in porcine Hb. Using DLS, the average hydrodynamic diameter () of Hbl Hb was measured at pH = 5, 7, 8, 9, and 10. At pH = 5 to 7, the Hbl Hb was found in its native form with equal to 24.2 nm, while at pH = 8 and 9, a dissociation process starts to take place resulting in = 9 nm. At pH = 10, only large aggregates of fragmented Hbl Hb with larger than 1000 nm was detected, however, a comparison of the DLS results with the polarized resonance Raman scattering (RRS) revealed that the coupling between the fragments did not involve direct interaction between the heme groups, but also that the local heme environment seems to be comparable in the aggregates and in the native Hbl Hb. By comparing the unpolarized RRS results obtained for erythrocytes (RBC) with those for Hbl Hb, led us to the important conclusion that Hbl Hb is much easier photolyzed than porcine RBC.

  3. A combination of dynamic light scattering and polarized resonance Raman scattering applied in the study of Arenicola Marina extracellular hemoglobin

    NASA Astrophysics Data System (ADS)

    Jernshøj, K. D.; Hassing, S.; Olsen, L. F.

    2013-08-01

    Arenicola Marina extracellular hemoglobin (Hbl Hb) is considered to be a promising candidate as a blood substitute. To entangle some of the properties of extracellular giant hexagonal bilayer hemoglobin (Hbl Hb) of Arenicola Marina, we combined polarized resonance Raman scattering (532 nm excitation) with dynamic light scattering (DLS) (632.8 nm). An analysis of the depolarization ratio of selected a2g skeletal modes of the heme in native Hbl Hb and porcine Hb, shows that the distortion of the heme group away from its ideal fourfold symmetry is much smaller for heme groups bound in the Hbl Hb than for heme groups bound in porcine Hb. Using DLS, the average hydrodynamic diameter (⟨dh⟩) of Hbl Hb was measured at pH = 5, 7, 8, 9, and 10. At pH = 5 to 7, the Hbl Hb was found in its native form with ⟨dh⟩ equal to 24.2 nm, while at pH = 8 and 9, a dissociation process starts to take place resulting in ⟨dh⟩ = 9 nm. At pH = 10, only large aggregates of fragmented Hbl Hb with ⟨dh⟩ larger than 1000 nm was detected, however, a comparison of the DLS results with the polarized resonance Raman scattering (RRS) revealed that the coupling between the fragments did not involve direct interaction between the heme groups, but also that the local heme environment seems to be comparable in the aggregates and in the native Hbl Hb. By comparing the unpolarized RRS results obtained for erythrocytes (RBC) with those for Hbl Hb, led us to the important conclusion that Hbl Hb is much easier photolyzed than porcine RBC.

  4. Sound Absorption of a 2DOF Resonant Liner with Negative Bias Flow

    NASA Technical Reports Server (NTRS)

    Ahuja, K. K.; Cataldi, P.; Gaeta, R. J., Jr.; Jones, Mike (Technical Monitor)

    2000-01-01

    This report describes an experimental study conducted to determine the effect of negative bias flow on the sound absorption of a two degree-of-freedom liner. The backwall for the liner was designed to act as a double-Helmholtz resonator so as to act as a hard wall at all frequencies except at its resonant frequencies. All normal incident impedance data presented herein was acquired in an impedance tube. The effect of bias flow is investigated for a buried septum porosity of 2% and 19.5% for bias flow orifice mach numbers up to 03 11. As a porous backwall is needed for the flow to pass through, the effect of bias flow on this backwall all had to be evaluated first. The bias flow appears to modify the resistance and reactance of the backwall alone at lower frequencies up to about 2 kHz, with marginal effects at higher frequencies. Absorption coefficients close to unity are achieved for a frequency range of 500-4000 Hz for the overall liner for a septum porosity of 2% and orifice mach number of 0.128. Insertion loss tests performed in a flow duct facility for grazing flow Mach numbers up to 0.2 and septum mach numbers up to 0.15 showed that negative bias flow can increase insertion loss by as much as 10 dB at frequencies in the range of 500 - 1400 Hz compared to no grazing flow. The effectiveness of the negative bias flow is diminished as the grazing flow velocity is increased.

  5. Synthesis, dual-nonlinear magnetic resonance and microwave absorption properties of nanosheet hierarchical cobalt particles.

    PubMed

    Wen, S L; Liu, Y; Zhao, X C; Cheng, J W; Li, H

    2014-09-14

    In this paper, we report the synthesis of three kinds of novel nanosheet hierarchical cobalt particles by adjusting the [C4H4O6](2-)/Co(2+) ratio through a liquid reduction method. We investigated the electromagnetic properties of the cobalt particles in detail over the microwave frequency range of 1-18 GHz. The results show that the real part of the permittivity decreases and the imaginary part of the permeability increases with an increase in the [C4H4O6](2-)/Co(2+) ratio. The permeability displays two resonance peaks over the frequency range. The cobalt particles with [C4H4O6](2-)/Co(2+) = 6 have a maximum reflection loss of -48.03 dB at 13.61 GHz, and the effective absorption bandwidth (RL ≤ -10 dB) is 6.76 GHz corresponding to a thickness of 1.7 mm. Considering the impedance matching and attenuation based on the electromagnetic parameters, we designed a way to obtain cobalt particles with excellent microwave absorption properties by decreasing the real part of permittivity and increasing the imaginary part of permeability.

  6. Surface plasmon enhanced Raman scattering frequency and angular resonance of Raman scattered light from pyridine on Au, Ag and Cu electrodes

    NASA Astrophysics Data System (ADS)

    Pettinger, B.; Wenning, U.; Wetzel, H.

    1980-12-01

    The strong dependence of the surface Raman intensity on the exciting frequency and on the angle of incidence for pyridine molecules adsorbed on Au, Ag and Cu electrodes after a weak oxidation/reduction cycle is evidence for a surface plasmon enhanced Raman scattering (SPERS).

  7. Two-dimensional stimulated resonance Raman spectroscopy of molecules with broadband x-ray pulses

    PubMed Central

    Biggs, Jason D.; Zhang, Yu; Healion, Daniel; Mukamel, Shaul

    2012-01-01

    Expressions for the two-dimensional stimulated x-ray Raman spectroscopy (2D-SXRS) signal obtained using attosecond x-ray pulses are derived. The 1D- and 2D-SXRS signals are calculated for trans-N-methyl acetamide (NMA) with broad bandwidth (181 as, 14.2 eV FWHM) pulses tuned to the oxygen and nitrogen K-edges. Crosspeaks in 2D signals reveal electronic Franck-Condon overlaps between valence orbitals and relaxed orbitals in the presence of the core-hole. PMID:22583220

  8. Thermoluminescence, electron paramagnetic resonance and optical absorption in natural and synthetic rhodonite crystals

    NASA Astrophysics Data System (ADS)

    Paião, J. R. B.; Watanabe, S.

    2008-10-01

    Thermoluminescence, electron paramagnetic resonance and optical absorption properties of rhodonite, a natural silicate mineral, have been investigated and compared to those of synthetic crystal, pure and doped. The TL peaks grow linearly for radiation dose up to 4 kGy, and then saturate. In all the synthetic samples, 140 and 340°C TL peaks are observed; the difference occurs in their relative intensities, but only 340°C peak grows strongly for high doses. Al2O3 and Al2O3 + CaO-doped synthetic samples presented several decades intenser TL compared to that of synthetic samples doped with other impurities. A heating rate of 4°C/s has been used in all the TL readings. The EPR spectrum of natural rhodonite mineral has only one huge signal around g = 2.0 with width extending from 1,000 to 6,000 G. This is due to Mn dipolar interaction, a fact proved by numerical calculation based on Van Vleck dipolar broadening expression. The optical absorption spectrum is rich in absorption bands in near-UV, visible and near-IR intervals. Several bands in the region from 540 to 340 nm are interpreted as being due to Mn3+ in distorted octahedral environment. A broad and intense band around 1,040 nm is due to Fe2+. It decays under heating up to 900°C. At this temperature it is reduced by 80% of its original intensity. The pink, natural rhodonite, heated in air starts becoming black at approximately 600°C.

  9. Temperature measurement of cold atoms using transient absorption of a resonant probe through an optical nanofibre

    NASA Astrophysics Data System (ADS)

    Kumar, Ravi; Gokhroo, Vandna; Bhushan Tiwari, Vibhuti; Chormaic, Síle Nic

    2016-11-01

    Optical nanofibres are ultrathin optical fibres with a waist diameter typically less than the wavelength of light being guided through them. Cold atoms can couple to the evanescent field of the nanofibre-guided modes and such systems are emerging as promising technologies for the development of atom-photon hybrid quantum devices. Atoms within the evanescent field region of an optical nanofibre can be probed by sending near or on-resonant light through the fibre; however, the probe light can detrimentally affect the properties of the atoms. In this paper, we report on the modification of the local temperature of laser-cooled 87Rb atoms in a magneto-optical trap centred around an optical nanofibre when near-resonant probe light propagates through it. A transient absorption technique has been used to measure the temperature of the affected atoms and temperature variations from 160 μk to 850 μk, for a probe power ranging from 0 to 50 nW, have been observed. This effect could have implications in relation to using optical nanofibres for probing and manipulating cold or ultracold atoms.

  10. Multipitched Diffraction Gratings for Surface Plasmon Resonance-Enhanced Infrared Reflection Absorption Spectroscopy.

    PubMed

    Petefish, Joseph W; Hillier, Andrew C

    2015-11-01

    We demonstrate the application of metal-coated diffraction gratings possessing multiple simultaneous pitch values for surface enhanced infrared absorption (SEIRA) spectroscopy. SEIRA increases the magnitude of vibrational signals in infrared measurements by one of several mechanisms, most frequently involving the enhanced electric field associated with surface plasmon resonance (SPR). While the majority of SEIRA applications to date have employed nanoparticle-based plasmonic systems, recent advances have shown how various metals and structures lead to similar signal enhancement. Recently, diffraction grating couplers have been demonstrated as a highly tunable platform for SEIRA. Indeed, gratings are an experimentally advantageous platform due to the inherently tunable nature of surface plasmon excitation at these surfaces since both the grating pitch and incident angle can be used to modify the spectral location of the plasmon resonance. In this work, we use laser interference lithography (LIL) to fabricate gratings possessing multiple pitch values by subjecting photoresist-coated glass slides to repetitive exposures at varying orientations. After metal coating, these gratings produced multiple, simultaneous plasmon peaks associated with the multipitched surface, as identified by infrared reflectance measurements. These plasmon peaks could then be coupled to vibrational modes in thin films to provide localized enhancement of infrared signals. We demonstrate the flexibility and tunability of this platform for signal enhancement. It is anticipated that, with further refinement, this approach might be used as a general platform for broadband enhancement of infrared spectroscopy. PMID:26458177

  11. Spatial Damping of Propagating Kink Waves Due to Resonant Absorption: Effect of Background Flow

    NASA Astrophysics Data System (ADS)

    Soler, R.; Terradas, J.; Goossens, M.

    2011-06-01

    Observations show the ubiquitous presence of propagating magnetohydrodynamic (MHD) kink waves in the solar atmosphere. Waves and flows are often observed simultaneously. Due to plasma inhomogeneity in the direction perpendicular to the magnetic field, kink waves are spatially damped by resonant absorption. The presence of flow may affect the wave spatial damping. Here, we investigate the effect of longitudinal background flow on the propagation and spatial damping of resonant kink waves in transversely nonuniform magnetic flux tubes. We combine approximate analytical theory with numerical investigation. The analytical theory uses the thin tube (TT) and thin boundary (TB) approximations to obtain expressions for the wavelength and the damping length. Numerically, we verify the previously obtained analytical expressions by means of the full solution of the resistive MHD eigenvalue problem beyond the TT and TB approximations. We find that the backward and forward propagating waves have different wavelengths and are damped on length scales that are inversely proportional to the frequency as in the static case. However, the factor of proportionality depends on the characteristics of the flow, so that the damping length differs from its static analog. For slow, sub-Alfvénic flows the backward propagating wave gets damped on a shorter length scale than in the absence of flow, while for the forward propagating wave the damping length is longer. The different properties of the waves depending on their direction of propagation with respect to the background flow may be detected by the observations and may be relevant for seismological applications.

  12. Heating of the solar corona by the resonant absorption of Alfven waves

    NASA Technical Reports Server (NTRS)

    Davila, Joseph M.

    1987-01-01

    An improved method for calculating the resonance absorption heating rate is discussed and the results are compared with observations in the solar corona. To accomplish this, the wave equation for a dissipative, compressible plasma is derived from the linearized magnetohydrodynamic equations for a plasma with transverse Alfven speed gradients. For parameters representative of the solar corona, it is found that a two-scale description of the wave motion is appropriate. The large-scale motion, which can be approximated as nearly ideal, has a scale which is on the order of the width of the loop. The small-scale wave, however, has a transverse scale much smaller than the width of the loop, with a width of about 0.3-250 km, and is highly dissipative. These two wave motions are coupled in a narrow resonance region in the loop where the global wave frequency equals the local Alfven wave frequency. Formally, this coupling comes about from using the method of matched asymptotic expansions to match the inner and outer (small and large scale) solutions. The resultant heating rate can be calculated from either of these solutions. A formula derived using the outer (ideal) solution is presented, and shown to be consistent with observations of heating and line broadening in the solar corona.

  13. Multipitched Diffraction Gratings for Surface Plasmon Resonance-Enhanced Infrared Reflection Absorption Spectroscopy.

    PubMed

    Petefish, Joseph W; Hillier, Andrew C

    2015-11-01

    We demonstrate the application of metal-coated diffraction gratings possessing multiple simultaneous pitch values for surface enhanced infrared absorption (SEIRA) spectroscopy. SEIRA increases the magnitude of vibrational signals in infrared measurements by one of several mechanisms, most frequently involving the enhanced electric field associated with surface plasmon resonance (SPR). While the majority of SEIRA applications to date have employed nanoparticle-based plasmonic systems, recent advances have shown how various metals and structures lead to similar signal enhancement. Recently, diffraction grating couplers have been demonstrated as a highly tunable platform for SEIRA. Indeed, gratings are an experimentally advantageous platform due to the inherently tunable nature of surface plasmon excitation at these surfaces since both the grating pitch and incident angle can be used to modify the spectral location of the plasmon resonance. In this work, we use laser interference lithography (LIL) to fabricate gratings possessing multiple pitch values by subjecting photoresist-coated glass slides to repetitive exposures at varying orientations. After metal coating, these gratings produced multiple, simultaneous plasmon peaks associated with the multipitched surface, as identified by infrared reflectance measurements. These plasmon peaks could then be coupled to vibrational modes in thin films to provide localized enhancement of infrared signals. We demonstrate the flexibility and tunability of this platform for signal enhancement. It is anticipated that, with further refinement, this approach might be used as a general platform for broadband enhancement of infrared spectroscopy.

  14. Single molecule surface enhanced resonance Raman scattering (SERRS) of the enhanced green fluorescent protein (EGFP)

    NASA Astrophysics Data System (ADS)

    Hofkens, Johan; De Schryver, Frans C.; Cotlet, Mircea; Habuchi, Satoshi

    2004-06-01

    One of the most intriguing findings in single molecule spectroscopy (SMS) is the observation of Raman spectra of individual molecules, despite the small cross section of the transitions involved. The observation of the spectra can be explained by the surface enhanced Raman scattering (SERRS) effect. At the single-molecule level, the SERRS-spectra recorded as a function of time reveal inhomogeneous behaviour such as on/off blinking, spectral diffusion, intensity fluctuations of vibrational line, and even splitting of some lines within the spectrum of one molecule. Single-molecule SERRS (SM-SERRS) spectroscopy opens up exciting opportunities in the field of biophysics and biomedical spectroscopy. The first example of single protein SERRS was performed on hemoglobin. However, the possibility of extracting the heme group by silver sols can not be excluded. Here we report on SM-SERRS spectra of enhanced green fluorescent protein (EGFP) in which the chromophore is kept in the protein. The time series of SM-SERRS spectra suggest the conversion of the EGFP chromophore between the deprotonated and the protonated form. Autocorrelation analysis of SM-SERRS trajectory reveals the presence of fast dynamics taking place in the protein. Our findings show the potential of the technique to study structural dynamics of protein molecules.

  15. A UV resonance Raman (UVRR) spectroscopic study on the extractable compounds of Scots pine ( Pinus sylvestris) wood . Part I: Lipophilic compounds

    NASA Astrophysics Data System (ADS)

    Nuopponen, M.; Willför, S.; Jääskeläinen, A.-S.; Sundberg, A.; Vuorinen, T.

    2004-11-01

    The wood resin in Scots pine ( Pinus sylvestris) stemwood and branch wood were studied using UV resonance Raman (UVRR) spectroscopy. UVRR spectra of the sapwood and heartwood hexane extracts, solid wood samples and model compounds (six resin acids, three fatty acids, a fatty acid ester, sitosterol and sitosterol acetate) were collected using excitation wavelengths of 229, 244 and 257 nm. In addition, visible Raman spectra of the fatty and resin acids were recorded. Resin compositions of heartwood and sapwood hexane extracts were determined using gas chromatography. Raman signals of both conjugated and isolated double bonds of all the model compounds were resonance enhanced by UV excitation. The oleophilic structures showed strong bands in the region of 1660-1630 cm -1. Distinct structures were enhanced depending on the excitation wavelength. The UVRR spectra of the hexane extracts showed characteristic bands for resin and fatty acids. It was possible to identify certain resin acids from the spectra. UV Raman spectra collected from the solid wood samples containing wood resin showed a band at ˜1650 cm -1 due to unsaturated resin components. The Raman signals from extractives in the resin rich branch wood sample gave even more strongly enhanced signals than the aromatic lignin.

  16. A UV resonance Raman (UVRR) spectroscopic study on the extractable compounds of Scots pine (Pinus sylvestris) wood. Part I: lipophilic compounds.

    PubMed

    Nuopponen, M; Willför, S; Jääskeläinen, A-S; Sundberg, A; Vuorinen, T

    2004-11-01

    The wood resin in Scots pine (Pinus sylvestris) stemwood and branch wood were studied using UV resonance Raman (UVRR) spectroscopy. UVRR spectra of the sapwood and heartwood hexane extracts, solid wood samples and model compounds (six resin acids, three fatty acids, a fatty acid ester, sitosterol and sitosterol acetate) were collected using excitation wavelengths of 229, 244 and 257 nm. In addition, visible Raman spectra of the fatty and resin acids were recorded. Resin compositions of heartwood and sapwood hexane extracts were determined using gas chromatography. Raman signals of both conjugated and isolated double bonds of all the model compounds were resonance enhanced by UV excitation. The oleophilic structures showed strong bands in the region of 1660-1630 cm(-1). Distinct structures were enhanced depending on the excitation wavelength. The UVRR spectra of the hexane extracts showed characteristic bands for resin and fatty acids. It was possible to identify certain resin acids from the spectra. UV Raman spectra collected from the solid wood samples containing wood resin showed a band at approximately 1650 cm(-1) due to unsaturated resin components. The Raman signals from extractives in the resin rich branch wood sample gave even more strongly enhanced signals than the aromatic lignin.

  17. Effect of collisions on dc magnetic-field generation in a plasma by resonance absorption of light

    SciTech Connect

    Adam, J.C.; Gourdin-Serveniere, A.; Mora, P.; Pellat, R.

    1982-05-01

    The importance of collisional ponderomotive effects on dc magnetic field generation is stressed. Computer simulations show that a weak rate of collision is sufficient to completely modify dc magnetic field generation in the resonant absorption of light, as compared with previous collisionless simulations. The agreement with theoretical predictions is shown.

  18. Resonant surface enhancement of Raman scattering of Ag nanoparticles on silicon substrates fabricated by dc sputtering

    SciTech Connect

    Fang Yingcui; Li Xiaxi; Blinn, Kevin; Mahmoud, Mahmoud A.; Liu Meilin

    2012-09-15

    Ag nanoparticles (AgNPs) were deposited onto silicon substrates by direct current (dc) magnetron sputtering. The influences of sputtering power and sputtering time on the AgNP film morphology were studied using atomic force microscopy. The particle size was successfully tuned from 19 nm to 53 nm by varying the sputtering time at a dc power of 10 W. When Rhodamine 6 G (R6G) was used as the probe molecule, the AgNP films showed significant surface enhanced Raman scattering effect. In particular, it is found that larger particles show stronger enhancement for lower concentrations of R6G while smaller particles display stronger enhancement for higher concentrations of R6G.

  19. Resonant absorption in semiconductor nanowires and nanowire arrays: Relating leaky waveguide modes to Bloch photonic crystal modes

    SciTech Connect

    Fountaine, Katherine T.; Whitney, William S.; Atwater, Harry A.

    2014-10-21

    We present a unified framework for resonant absorption in periodic arrays of high index semiconductor nanowires that combines a leaky waveguide theory perspective and that of photonic crystals supporting Bloch modes, as array density transitions from sparse to dense. Full dispersion relations are calculated for each mode at varying illumination angles using the eigenvalue equation for leaky waveguide modes of an infinite dielectric cylinder. The dispersion relations along with symmetry arguments explain the selectivity of mode excitation and spectral red-shifting of absorption for illumination parallel to the nanowire axis in comparison to perpendicular illumination. Analysis of photonic crystal band dispersion for varying array density illustrates that the modes responsible for resonant nanowire absorption emerge from the leaky waveguide modes.

  20. Sub-bandgap linear-absorption-based photodetectors in avalanche mode in PN-diode-integrated silicon microring resonators.

    PubMed

    Li, Yu; Feng, Shaoqi; Zhang, Yu; Poon, Andrew W

    2013-12-01

    We report a sub-bandgap linear-absorption-based photodetector in avalanche mode at 1550 nm in a PN-diode-integrated silicon microring resonator. The photocurrent is primarily generated by the defect-state absorption introduced by the boron and phosphorous ion implantation during the PN diode formation. The responsivity is enhanced by both the cavity effect and the avalanche multiplication. We measure a responsivity of ~72.8 mA/W upon 8 V at cavity resonances in avalanche mode, corresponding to a gain of ~72 relative to the responsivity of ~1.0 mA/W upon 3 V at cavity resonances in normal mode. Our device exhibits a 3 dB bandwidth of ~7 GHz and an open eye diagram at 15 Gbit/s upon 8 V.

  1. Structural characterization of titania by X-ray diffraction, photoacoustic, Raman spectroscopy and electron paramagnetic resonance spectroscopy.

    PubMed

    Kadam, R M; Rajeswari, B; Sengupta, Arijit; Achary, S N; Kshirsagar, R J; Natarajan, V

    2015-02-25

    A titania mineral (obtained from East coast, Orissa, India) was investigated by X-ray diffraction (XRD), photoacoustic spectroscopy (PAS), Raman and Electron Paramagnetic Resonance (EPR) studies. XRD studies indicated the presence of rutile (91%) and anatase (9%) phases in the mineral. Raman investigation supported this information. Both rutile and anatase phases have tetragonal structure (rutile: space group P4(2)/mnm, a=4.5946(1) Å, c=2.9597(1) Å, V=62.48(1) (Å)(3), Z=2; anatase: space group I4(1)/amd, 3.7848(2) Å, 9.5098(11) Å, V=136.22(2) (Å)(3), Z=4). The deconvoluted PAS spectrum showed nine peaks around 335, 370, 415,485, 555, 605, 659, 690,730 and 785 nm and according to the ligand field theory, these peaks were attributed to the presence of V(4+), Cr(3+), Mn(4+) and Fe(3+) species. EPR studies revealed the presence of transition metal ions V(4+)(d(1)), Cr(3+)(d(3)), Mn(4+)(d(3)) and Fe(3+)(d(5)) at Ti(4+) sites. The EPR spectra are characterized by very large crystal filed splitting (D term) and orthorhombic distortion term (E term) for multiple electron system (s>1) suggesting that the transition metal ions substitute the Ti(4+) in the lattice which is situated in distorted octahedral coordination of oxygen. The possible reasons for observation of unusually large D and E term in the EPR spectra of transition metal ions (S=3/2 and 5/2) are discussed. PMID:25233027

  2. Structural characterization of titania by X-ray diffraction, photoacoustic, Raman spectroscopy and electron paramagnetic resonance spectroscopy.

    PubMed

    Kadam, R M; Rajeswari, B; Sengupta, Arijit; Achary, S N; Kshirsagar, R J; Natarajan, V

    2015-02-25

    A titania mineral (obtained from East coast, Orissa, India) was investigated by X-ray diffraction (XRD), photoacoustic spectroscopy (PAS), Raman and Electron Paramagnetic Resonance (EPR) studies. XRD studies indicated the presence of rutile (91%) and anatase (9%) phases in the mineral. Raman investigation supported this information. Both rutile and anatase phases have tetragonal structure (rutile: space group P4(2)/mnm, a=4.5946(1) Å, c=2.9597(1) Å, V=62.48(1) (Å)(3), Z=2; anatase: space group I4(1)/amd, 3.7848(2) Å, 9.5098(11) Å, V=136.22(2) (Å)(3), Z=4). The deconvoluted PAS spectrum showed nine peaks around 335, 370, 415,485, 555, 605, 659, 690,730 and 785 nm and according to the ligand field theory, these peaks were attributed to the presence of V(4+), Cr(3+), Mn(4+) and Fe(3+) species. EPR studies revealed the presence of transition metal ions V(4+)(d(1)), Cr(3+)(d(3)), Mn(4+)(d(3)) and Fe(3+)(d(5)) at Ti(4+) sites. The EPR spectra are characterized by very large crystal filed splitting (D term) and orthorhombic distortion term (E term) for multiple electron system (s>1) suggesting that the transition metal ions substitute the Ti(4+) in the lattice which is situated in distorted octahedral coordination of oxygen. The possible reasons for observation of unusually large D and E term in the EPR spectra of transition metal ions (S=3/2 and 5/2) are discussed.

  3. Hydrogen bonding interactions with the Schiff base of bacteriorhodopsin. Resonance Raman spectroscopy of the mutants D85N and D85A.

    PubMed

    Rath, P; Marti, T; Sonar, S; Khorana, H G; Rothschild, K J

    1993-08-25

    The bacteriorhodopsin (bR) mutants Asp-85-->Asn (D85N) and Asp-85-->Ala (D85A) have a red-shifted chromophore absorption and exhibit no proton pumping (Otto, H., Marti, T., Holz, M., Mogi, T., Stern, L., Engel, F., Khorana, H. G., and Heyn, M. P. (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 1018-1022) consistent with the hypothesis that Asp-85 functions as a counterion and proton acceptor for the retinal Schiff base (Braiman, M. S., Mogi, T., Marti, T., Stern, L. J., Khorana, H. G., and Rothschild, K. J. (1988) Biochemistry 27, 8516-8520). Resonance Raman spectroscopy reveals that these mutants contain a mixture of all-trans and 13-cis/C = N syn chromophores, similar to dark-adapted purple membrane and acid-induced or deionized blue membrane. At high NaCl concentrations, both mutants adopt a predominantly all-trans chromophore structure similar to acid purple membrane. A comparison of the Schiff base C = NH+ stretch frequency (vC = N) and deuterium isotope shift for D85N, D85A as well as various forms of bR, including light-adapted bR, blue membrane, and acid purple membrane, provides information about hydrogen bonding interactions to the Schiff base. D85N has as strong a hydrogen bond as light-adapted bR despite the loss of the negative charge at residue 85. In contrast, D85A has a weaker hydrogen bond. These results can be explained if a direct interaction exists between the Schiff base and Asn-85 in D85N and between the Schiff base and a substituted water molecule in D85A. Many of the properties of wild type bR, D85N, D85A, blue membrane, and acid purple membrane can be explained on the basis of changes in the local hydrogen bonding near the Schiff base.

  4. Double resonant absorption measurement of acetylene symmetric vibrational states probed with cavity ring down spectroscopy.

    PubMed

    Karhu, J; Nauta, J; Vainio, M; Metsälä, M; Hoekstra, S; Halonen, L

    2016-06-28

    A novel mid-infrared/near-infrared double resonant absorption setup for studying infrared-inactive vibrational states is presented. A strong vibrational transition in the mid-infrared region is excited using an idler beam from a singly resonant continuous-wave optical parametric oscillator, to populate an intermediate vibrational state. High output power of the optical parametric oscillator and the strength of the mid-infrared transition result in efficient population transfer to the intermediate state, which allows measuring secondary transitions from this state with a high signal-to-noise ratio. A secondary, near-infrared transition from the intermediate state is probed using cavity ring-down spectroscopy, which provides high sensitivity in this wavelength region. Due to the narrow linewidths of the excitation sources, the rovibrational lines of the secondary transition are measured with sub-Doppler resolution. The setup is used to access a previously unreported symmetric vibrational state of acetylene, ν1+ν2+ν3+ν4 (1)+ν5 (-1) in the normal mode notation. Single-photon transitions to this state from the vibrational ground state are forbidden. Ten lines of the newly measured state are observed and fitted with the linear least-squares method to extract the band parameters. The vibrational term value was measured to be at 9775.0018(45) cm(-1), the rotational parameter B was 1.162 222(37) cm(-1), and the quartic centrifugal distortion parameter D was 3.998(62) × 10(-6) cm(-1), where the numbers in the parenthesis are one-standard errors in the least significant digits. PMID:27369508

  5. Double resonant absorption measurement of acetylene symmetric vibrational states probed with cavity ring down spectroscopy.

    PubMed

    Karhu, J; Nauta, J; Vainio, M; Metsälä, M; Hoekstra, S; Halonen, L

    2016-06-28

    A novel mid-infrared/near-infrared double resonant absorption setup for studying infrared-inactive vibrational states is presented. A strong vibrational transition in the mid-infrared region is excited using an idler beam from a singly resonant continuous-wave optical parametric oscillator, to populate an intermediate vibrational state. High output power of the optical parametric oscillator and the strength of the mid-infrared transition result in efficient population transfer to the intermediate state, which allows measuring secondary transitions from this state with a high signal-to-noise ratio. A secondary, near-infrared transition from the intermediate state is probed using cavity ring-down spectroscopy, which provides high sensitivity in this wavelength region. Due to the narrow linewidths of the excitation sources, the rovibrational lines of the secondary transition are measured with sub-Doppler resolution. The setup is used to access a previously unreported symmetric vibrational state of acetylene, ν1+ν2+ν3+ν4 (1)+ν5 (-1) in the normal mode notation. Single-photon transitions to this state from the vibrational ground state are forbidden. Ten lines of the newly measured state are observed and fitted with the linear least-squares method to extract the band parameters. The vibrational term value was measured to be at 9775.0018(45) cm(-1), the rotational parameter B was 1.162 222(37) cm(-1), and the quartic centrifugal distortion parameter D was 3.998(62) × 10(-6) cm(-1), where the numbers in the parenthesis are one-standard errors in the least significant digits.

  6. Double resonant absorption measurement of acetylene symmetric vibrational states probed with cavity ring down spectroscopy

    NASA Astrophysics Data System (ADS)

    Karhu, J.; Nauta, J.; Vainio, M.; Metsälä, M.; Hoekstra, S.; Halonen, L.

    2016-06-01

    A novel mid-infrared/near-infrared double resonant absorption setup for studying infrared-inactive vibrational states is presented. A strong vibrational transition in the mid-infrared region is excited using an idler beam from a singly resonant continuous-wave optical parametric oscillator, to populate an intermediate vibrational state. High output power of the optical parametric oscillator and the strength of the mid-infrared transition result in efficient population transfer to the intermediate state, which allows measuring secondary transitions from this state with a high signal-to-noise ratio. A secondary, near-infrared transition from the intermediate state is probed using cavity ring-down spectroscopy, which provides high sensitivity in this wavelength region. Due to the narrow linewidths of the excitation sources, the rovibrational lines of the secondary transition are measured with sub-Doppler resolution. The setup is used to access a previously unreported symmetric vibrational state of acetylene, ν 1 + ν 2 + ν 3 + ν4 1 + ν5 - 1 in the normal mode notation. Single-photon transitions to this state from the vibrational ground state are forbidden. Ten lines of the newly measured state are observed and fitted with the linear least-squares method to extract the band parameters. The vibrational term value was measured to be at 9775.0018(45) cm-1, the rotational parameter B was 1.162 222(37) cm-1, and the quartic centrifugal distortion parameter D was 3.998(62) × 10-6 cm-1, where the numbers in the parenthesis are one-standard errors in the least significant digits.

  7. A 2A2<--X 2B1 absorption and Raman spectra of the OClO molecule: A three-dimensional time-dependent wave packet study

    NASA Astrophysics Data System (ADS)

    Sun, Zhigang; Lou, Nanquan; Nyman, Gunnar

    2005-02-01

    Time-dependent wave packet calculations of the (A 2A2←X 2B1) absorption and Raman spectra of the OClO molecule are reported. The Fourier grid Hamiltonian method in three dimensions is employed. The X 2B1 ground state ab initio potential energy surface reported by Peterson [J. Chem. Phys. 109, 8864 (1998)] is used together with his corresponding A 2A2 state surface or the revised surface of the A 2A2 state by Xie and Guo [Chem. Phys. Lett. 307, 109 (1999)]. Radau coordinates are used to describe the vibrations of a nonrotating OClO molecule. The split-operator method combined with fast Fourier transform is applied to propagate the wave function. We find that the ab initio A 2A2 potential energy surface better reproduces the detailed structures of the absorption spectrum at long wavelength, while the revised surface of the A 2A2 state, consistent with the work of Xie and Guo, better reproduces the overall shape and the energies of the vibrational levels. Both surfaces of the A 2A2 state can reasonably reproduce the experimental Raman spectra but neither does so in detail for the numerical model employed in the present work.

  8. Temperature induced changes in resonance Raman spectra intensity of all-trans-β-carotene: Changes in the fundamental, combination and overtone modes

    NASA Astrophysics Data System (ADS)

    Liu, Tianyuan; Xu, Shengnan; Li, Zuowei; Wang, Mengzhou; Sun, Chenglin

    2014-10-01

    The resonance Raman spectra of the fundamental, combination and overtone modes around the Csbnd C and Cdbnd C stretches of all-trans-β-carotene in 1,2-dichloroethane solution are obtained from the 293 K to 83 K temperature range. The results indicate that the intensity of the fundamentals in the liquid and solid phases generally increases as the temperature decreases, except for the liquid-solid phase transition, which exhibits a decreasing trend. The Raman intensities ratio between the fundamentals υ1 and υ2, combinations (overtones) and the fundamentals both increases with decreasing temperature. The Raman bandwidths of the Cdbnd C bonds gradually become narrow as the temperature decreases. These varieties of relative intensity are analyzed using the coherent weakly damped electron-lattice vibration mode, the effective conjugation length mode as well as the theory of electron-phonon interaction in this work.

  9. The effect of chemical variations on the structural polarity of relaxor ferroelectrics studied by resonance Raman spectroscopy.

    PubMed

    Rohrbeck, A; de la Flor, G; Aroyo, M I; Gospodinov, M; Bismayer, U; Mihailova, B

    2016-11-30

    Resonance Raman spectroscopy was applied to doped PbSc0.5Ta0.5O3 and PbSc0.5Nb0.5O3 relaxor ferroelectrics, to better understand the effect of composition disorder on the mesoscopic-scale polar order in complex perovskite-type (ABO3) ferroelectrics. The excitation photon energy used was 3.8 eV, which is slightly above the energy gap and corresponds to the maximum of the optical dielectric permittivity. Group-theory analysis reveals that the resonance Raman scattering (RRS) observed under these conditions is allowed only in polar crystal classes. Therefore, RRS is dominated by the atomic dynamics of nanoregions with coherent polar distortions, which considerably facilitates the comparison of polar order in various compounds. The results show that A-site doping (Ba(2+), Sr(2+), La(3+), Bi(3+)) has significantly stronger effect on the structural polarity than the introduction of a third element at the B site (Nb(5+) or Sn(4+) doped in PbSc0.5Ta0.5O3). The A-site substitution by cations that in contrast to Pb(2+) have isotropic outermost electron shells disturbs the system of lone-pair electrons, thus reducing the correlation length of coupled polar distortions and the strength of the electric field associated with the mean polarization of polar nanoregions. A-site doping with larger cations (Ba(2+)) augments the polar deformation of the individual BO6 octahedra due to local elastic fields. As a result, such A-site doping intensifies the initial structural polarity at high temperatures and prevails the enlargement of the polar fraction at low temperatures. A-site doping with smaller cations (Sr(2+), La(3+)), regardless if they are isovalent or aliovalent to Pb(2+), increases the correlation length of antiferrodistortive order (BO6 tilts), which in turn assists the development of double-perovskite structure with coherent local polar distortions. A-site doping with aliovalent cations (Bi(3+)) having the same outermost electron shell and ionic radius as the host A

  10. The effect of chemical variations on the structural polarity of relaxor ferroelectrics studied by resonance Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Rohrbeck, A.; de la Flor, G.; Aroyo, M. I.; Gospodinov, M.; Bismayer, U.; Mihailova, B.

    2016-11-01

    Resonance Raman spectroscopy was applied to doped PbSc0.5Ta0.5O3 and PbSc0.5Nb0.5O3 relaxor ferroelectrics, to better understand the effect of composition disorder on the mesoscopic-scale polar order in complex perovskite-type (ABO3) ferroelectrics. The excitation photon energy used was 3.8 eV, which is slightly above the energy gap and corresponds to the maximum of the optical dielectric permittivity. Group-theory analysis reveals that the resonance Raman scattering (RRS) observed under these conditions is allowed only in polar crystal classes. Therefore, RRS is dominated by the atomic dynamics of nanoregions with coherent polar distortions, which considerably facilitates the comparison of polar order in various compounds. The results show that A-site doping (Ba2+, Sr2+, La3+, Bi3+) has significantly stronger effect on the structural polarity than the introduction of a third element at the B site (Nb5+ or Sn4+ doped in PbSc0.5Ta0.5O3). The A-site substitution by cations that in contrast to Pb2+ have isotropic outermost electron shells disturbs the system of lone-pair electrons, thus reducing the correlation length of coupled polar distortions and the strength of the electric field associated with the mean polarization of polar nanoregions. A-site doping with larger cations (Ba2+) augments the polar deformation of the individual BO6 octahedra due to local elastic fields. As a result, such A-site doping intensifies the initial structural polarity at high temperatures and prevails the enlargement of the polar fraction at low temperatures. A-site doping with smaller cations (Sr2+, La3+), regardless if they are isovalent or aliovalent to Pb2+, increases the correlation length of antiferrodistortive order (BO6 tilts), which in turn assists the development of double-perovskite structure with coherent local polar distortions. A-site doping with aliovalent cations (Bi3+) having the same outermost electron shell and ionic radius as the host A-site Pb2+ cations leads to

  11. The effect of chemical variations on the structural polarity of relaxor ferroelectrics studied by resonance Raman spectroscopy.

    PubMed

    Rohrbeck, A; de la Flor, G; Aroyo, M I; Gospodinov, M; Bismayer, U; Mihailova, B

    2016-11-30

    Resonance Raman spectroscopy was applied to doped PbSc0.5Ta0.5O3 and PbSc0.5Nb0.5O3 relaxor ferroelectrics, to better understand the effect of composition disorder on the mesoscopic-scale polar order in complex perovskite-type (ABO3) ferroelectrics. The excitation photon energy used was 3.8 eV, which is slightly above the energy gap and corresponds to the maximum of the optical dielectric permittivity. Group-theory analysis reveals that the resonance Raman scattering (RRS) observed under these conditions is allowed only in polar crystal classes. Therefore, RRS is dominated by the atomic dynamics of nanoregions with coherent polar distortions, which considerably facilitates the comparison of polar order in various compounds. The results show that A-site doping (Ba(2+), Sr(2+), La(3+), Bi(3+)) has significantly stronger effect on the structural polarity than the introduction of a third element at the B site (Nb(5+) or Sn(4+) doped in PbSc0.5Ta0.5O3). The A-site substitution by cations that in contrast to Pb(2+) have isotropic outermost electron shells disturbs the system of lone-pair electrons, thus reducing the correlation length of coupled polar distortions and the strength of the electric field associated with the mean polarization of polar nanoregions. A-site doping with larger cations (Ba(2+)) augments the polar deformation of the individual BO6 octahedra due to local elastic fields. As a result, such A-site doping intensifies the initial structural polarity at high temperatures and prevails the enlargement of the polar fraction at low temperatures. A-site doping with smaller cations (Sr(2+), La(3+)), regardless if they are isovalent or aliovalent to Pb(2+), increases the correlation length of antiferrodistortive order (BO6 tilts), which in turn assists the development of double-perovskite structure with coherent local polar distortions. A-site doping with aliovalent cations (Bi(3+)) having the same outermost electron shell and ionic radius as the host A

  12. Microwave absorption of a TiO2@PPy hybrid and its nonlinear dielectric resonant attenuation mechanism

    NASA Astrophysics Data System (ADS)

    Jiang, Wanchun; Wang, Yu; Xie, Aming; Wu, Fan

    2016-09-01

    We report on a high-performance electromagnetic absorption material (TiO2@PPy) developed via a facile in situ polymerization process, where lower than  ‑60 dB maximum absorption and 6.56 dB effective absorption bandwidth (lower than  ‑10 dB) can be obtained under low thickness. The excellent electromagnetic wave absorption ability is attributed to the synthetic effect of improved impedance matching and the dual loss mechanism, which originates from the polarization relaxations of dipoles induced by vacancy defects and a conductive network constructed by aerogels. An equivalent circuit model is established to explicate the nonlinear dielectric resonant attenuation mechanism.

  13. Optical resonance-enhanced absorption-based near-field immunochip biosensor for allergen detection.

    PubMed

    Maier, Irene; Morgan, Michael R A; Lindner, Wolfgang; Pittner, Fritz

    2008-04-15

    An optical immunochip biosensor has been developed as a rapid method for allergen detection in complex food matrixes, and its application evaluated for the detection of the egg white allergens, ovalbumin and ovomucoid. The optical near-field phenomenon underlying the basic principle of the sensor design is called resonance-enhanced absorption (REA), which utilizes gold nanoparticles (Au NPs) as signal transducers in a highly sensitive interferometric setup. Using this approach, a novel, simple, and rapid colorimetric solid-phase immunoassay on a planar chip substrate was realized in direct and sandwich assay formats, with a detection system that does not require any instrumentation for readout. Semiquantitative immunochemical responses are directly visible to the naked eye of the analyst. The biosensor shows concentration-dependent color development by capturing antibody-functionalized Au NPs on allergen-coated chips and has a detection limit of 1 ng/mL. To establish a rapid method, we took advantage of the physicochemical microenvironment of the Au NP-antibody bioconjugate to be bound directly over an interacting poly(styrene-methyl methacrylate) interlayer by an immobilized antigen. In the direct assay format, a coating time with allergen of only 5 min under "soft" nondenaturing conditions was sufficient for accurate reproducibility and sensitivity. In conclusion, the REA-based immunochip sensor is easy to fabricate, is reproducible and selective in its performance, has minimal technical requirements, and will enable high-throughput screening of affinity binding interactions in technological and medical applications. PMID:18358010

  14. Sensitive Trimodal Magnetic Resonance Imaging-Surface-Enhanced Resonance Raman Scattering-Fluorescence Detection of Cancer Cells with Stable Magneto-Plasmonic Nanoprobes.

    PubMed

    Carrouée, Ambre; Allard-Vannier, Emilie; Même, Sandra; Szeremeta, Frederic; Beloeil, Jean-Claude; Chourpa, Igor

    2015-11-17

    Novel magneto-plasmonic nanoprobes were designed for multimodal diagnosis of cancer by combination of magnetic resonance imaging (MRI), surface-enhanced resonance Raman scattering (SERRS), and fluorescence emission in the very near infrared (VNIR). A controlled electrostatic assembly of silver nanoparticles (AgNPs), superparamagnetic iron oxide nanoparticles (SPIONs), VNIR dye Nile Blue (NB), and biopolymer chitosan (Chi) was used to formulate the AgIONs-Chi nanoprobes. The formulation protocol did not involve organic solvents and was rapid and efficient as confirmed by magnetic sorting. The SERRS response of the nanoprobes was very intense and constant for days. It decreased linearly upon 1000-fold dilution and was still recognizable at 0.1 nM NB concentration. After 30 days of storage, the SERRS loss was less than 30% and the hydrodynamic size of the AgIONs-Chi in PBS remained below 200 nm. The gradual decrease of the ratio SERRS/fluorescence allowed one to monitor the release of the fluorescent molecule upon long-term nanoprobe dissociation. The AgIONs-Chi exhibited 2-fold higher MRI contrast than that of commercially available SPION suspensions. Finally, the nanoprobes were actively uptaken by HeLa cancer cells and ensured trimodal MRI-SERRS-fluorescence detection of 10 μL cell inclusions in cm-sized agarose gels used here as phantom models of microtumors. The above results show that the magneto-plasmonic AgIONs-Chi are promising substrates for SERRS analysis in solution and for multimodal imaging of cancer cells. PMID:26488315

  15. Excitons and exciton-phonon interactions in 2D MoS2 , WS2 and WSe2 studied by resonance Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Pimenta, Marcos; Del Corro, Elena; Carvalho, Bruno; Malard, Leandro; Alves, Juliana; Fantini, Cristiano; Terrones, Humberto; Elias, Ana Laura; Terrones, Mauricio

    The 2D materials exhibit a very strong exciton binding energy, and the exciton-phonon coupling plays an important role in their optical properties. Resonance Raman spectroscopy (RRS) is a very useful tool to provide information about excitons and their couplings with phonons. We will present in this work a RRS study of different samples of 2D transition metal dichalcogenides (MoS2, WS2 and WSe2) with one, two and three layers (1L, 2L, 3L) and bulk samples, using more than 30 different laser excitation lines covering the visible range. We have observed that all Raman features are enhanced by resonances with excitonic transitions. From the laser energy dependence of the Raman excitation profile (REP) we obtained the energies of the excitonic states and their dependence with the number of atomic layers.. In the case of MoS2, we observed that the electron-phonon coupling is symmetry dependent, and our results provide experimental evidence of the C exciton recently predicted theoretically. The RRS results WSe2 show that the Raman modes are enhanced by the excited excitonic states and we will present the dependence of the excited states energies on the number of layers.

  16. A copper(II) complex with a Cu-S₈ bond. Attenuated total reflectance, electron paramagnetic resonance, resonance Raman and atoms-in-molecule calculations.

    PubMed

    Shee, Nirmal K; Adekunle, Florence A O; Verma, Ravi; Kumar, Devesh; Datta, Dipankar

    2015-12-01

    Green [Cu(1,10-phenanthroline)2OH2](ClO4)2 (1) reacts with yellow elemental sulfur at room temperature in methanol to yield turquoise blue [Cu(1,10-phenanthro-line)2(S8)](ClO4)2 (2). A comparative study of the EPR spectra of 1 and 2 in solid state and in methanol glass indicates that the S8 unit in 2 is bound to the metal. High level DFT calculations show that the cation in 2 is five coordinate, distorted square pyramidal with S8 occupying the apical position. The crucial Cu(II)-S bond is around 2.9Å. Such long Cu(II)-S bonds occur in oxidized plastocyanin where it is considered to be bonding. Presence of a weak Cu-S8 bond is revealed in the resonance Raman spectra of 2. Satisfactory matching of the calculated and experimental IR spectra vindicates the theoretically derived structure of the cation in 2.

  17. A copper(II) complex with a Cu-S₈ bond. Attenuated total reflectance, electron paramagnetic resonance, resonance Raman and atoms-in-molecule calculations.

    PubMed

    Shee, Nirmal K; Adekunle, Florence A O; Verma, Ravi; Kumar, Devesh; Datta, Dipankar

    2015-12-01

    Green [Cu(1,10-phenanthroline)2OH2](ClO4)2 (1) reacts with yellow elemental sulfur at room temperature in methanol to yield turquoise blue [Cu(1,10-phenanthro-line)2(S8)](ClO4)2 (2). A comparative study of the EPR spectra of 1 and 2 in solid state and in methanol glass indicates that the S8 unit in 2 is bound to the metal. High level DFT calculations show that the cation in 2 is five coordinate, distorted square pyramidal with S8 occupying the apical position. The crucial Cu(II)-S bond is around 2.9Å. Such long Cu(II)-S bonds occur in oxidized plastocyanin where it is considered to be bonding. Presence of a weak Cu-S8 bond is revealed in the resonance Raman spectra of 2. Satisfactory matching of the calculated and experimental IR spectra vindicates the theoretically derived structure of the cation in 2. PMID:26125988

  18. Ionic strength dependence of cytochrome c structure and Trp-59 H/D exchange from ultraviolet resonance Raman spectroscopy.

    PubMed

    Liu, G Y; Grygon, C A; Spiro, T G

    1989-06-13

    Ultraviolet resonance Raman spectra are reported for cytochrome c (cyt c) in FeII and FeIII oxidation states at low (0.005 M) and high (0.9-1.5 M) ionic strength. With 200-nm excitation the amide band intensities are shown to remain constant, establishing that redox state and ionic strength have no influence on the alpha-helical content. The tyrosine 830/850-cm-1 doublet, however, shows a loss in 830-cm-1 intensity at I = 0.005 M for the FeIII protein, suggesting a weakening or a loss of H-bonding from an internal tyrosine, probably Tyr-48, which is H-bonded to a heme propionate group in cyt c crystals. Excitation profiles of tryptophan peak at approximately 229 nm for both FeII and FeIII forms of cyt c, but at approximately 218 nm for aqueous tryptophan. The approximately 2200-cm-1 red shift of the resonant electronic transition is attributed to the Trp-59 residue being buried and H-bonded. Consistent with this Trp environment, the H-bond-sensitive 877-cm-1 Trp band is strong and sharp, and the 1357/1341-cm-1 doublet has a large intensity ratio, approximately 1.5, for both FeII and FeIII cyt c. The 877-cm-1-band frequency shifts to 860 cm-1 when the Trp indole proton is replaced by a deuteron. This band was used to show that Trp H/D exchange in D2O is much faster for FeIII than FeII cyt c. The half-time for exchange at room temperature is estimated to be approximately 30 and approximately 5 h, respectively, for FeII and FeIII when examined at I = 0.005.(ABSTRACT TRUNCATED AT 250 WORDS)

  19. Structure of the retinal chromophore in the hR/sub L/ intermediate of halorhodopsin from resonance raman spectroscopy

    SciTech Connect

    Fodor, S.P.A.; Bogomolni, R.A.; Mathies, R.A.

    1987-10-20

    Time-resolved resonance Raman spectra of the hR/sub L/ intermediate of halorhodopsin have been obtained. The structurally sensitive fingerprint region of the hR/sub L/ spectrum is very similar to that of bacteriorhodospin's L/sub 550/ intermediate, which is known to have a 13-cis configuration. This indicates that hR/sub L/ contains a 13-cis chromophore and that an all-trans ..-->.. 13-cis isomerization occurs in the halorhodopsin photocycle.hR/sub L/ exhibits a Schiff base stretching mode at 1644 cm/sup -1/, which shifts to 1620 cm/sup -1/ in D/sub 2/O. This demonstrates that the Schiff base linkage to the protein is protonated. The insensitivity of the C-C stretching mode frequencies to N-deuteriation suggests that the Schiff base configuration is anti. The 24 cm/sup -1/ shift of the Schiff base mode in D/sub 2/O indicates that the Schiff base proton in hR/sub L/ has a stronger hydrogen-bonding interaction with the protein than does hR/sub 578/.

  20. Anti-Stokes resonant x-ray Raman scattering for atom specific and excited state selective dynamics

    NASA Astrophysics Data System (ADS)

    Kunnus, Kristjan; Josefsson, Ida; Rajkovic, Ivan; Schreck, Simon; Quevedo, Wilson; Beye, Martin; Grübel, Sebastian; Scholz, Mirko; Nordlund, Dennis; Zhang, Wenkai; Hartsock, Robert W.; Gaffney, Kelly J.; Schlotter, William F.; Turner, Joshua J.; Kennedy, Brian; Hennies, Franz; Techert, Simone; Wernet, Philippe; Odelius, Michael; Föhlisch, Alexander

    2016-10-01

    Ultrafast electronic and structural dynamics of matter govern rate and selectivity of chemical reactions, as well as phase transitions and efficient switching in functional materials. Since x-rays determine electronic and structural properties with elemental, chemical, orbital and magnetic selectivity, short pulse x-ray sources have become central enablers of ultrafast science. Despite of these strengths, ultrafast x-rays have been poor at picking up excited state moieties from the unexcited ones. With time-resolved anti-Stokes resonant x-ray Raman scattering (AS-RXRS) performed at the LCLS, and ab initio theory we establish background free excited state selectivity in addition to the elemental, chemical, orbital and magnetic selectivity of x-rays. This unparalleled selectivity extracts low concentration excited state species along the pathway of photo induced ligand exchange of Fe(CO)5 in ethanol. Conceptually a full theoretical treatment of all accessible insights to excited state dynamics with AS-RXRS with transform-limited x-ray pulses is given—which will be covered experimentally by upcoming transform-limited x-ray sources.