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Sample records for resonance raman study

  1. Resonance Raman spectroscopy study of protonated porphyrin

    NASA Astrophysics Data System (ADS)

    Gorski, A.; Starukhin, A.; Stavrov, S.; Gawinkowski, S.; Waluk, J.

    2017-02-01

    Resonance Raman microscopy was used to study the resonance Raman scattering of the diacid (diprotonated form) of free-base porphyrin (21H,23H-porphine) in a crystal powder and KBr pellets. Intensive lines in the spectral range between 100 ÷ 1000 cm- 1 have been detected and assigned as spectral manifestation of out-of-plane modes. The Raman spectra were simulated by means of DFT methods and compared with the experimental data. It is evident from experimental and theoretical results that the activation of out-of-plane modes arises from saddle distortion of the porphyrin macrocycle upon formation of its diprotonated form.

  2. Resonance Raman studies of the purple membrane.

    PubMed

    Aton, B; Doukas, A G; Callender, R H; Becher, B; Ebrey, T G

    1977-06-28

    The individual resonance Raman spectra of the PM568 and M412 forms of light-adapted purple membrane from Halobacterium halobium have been measured using the newly developed flow technique. For comparison purposes, the Raman spectra of the model chromophores, all-trans- and 13-cis retinal n-butylamine, both as protonated and unprotonated Schiff bases, have also been obtained. In agreement with previous work, the Raman data indicate that the retinal chromophore is linked to the purple membrane protein via a protonated. Schiff base in the case of the PM568 and an unprotonated Schiff base for the M412 form. The basic mechanism for color regulation in both forms appears to be electron delocalization. The spectral features of the two forms are different from each other and different from the model compound spectra.

  3. Resonance and Variable Temperature Raman Studies of Chloroperoxidase and Methemoglobin.

    NASA Astrophysics Data System (ADS)

    Remba, Ronald David

    1980-12-01

    Raman spectra of the heme proteins chloroperoxidase and methemoglobin, chemically and temperature modified, are obtained for laser excitation near the Soret absorption band. Numerous biochemical and physical results are obtained. The following observations for chloroperoxidase have been made. The scattered intensity for resonance (406.7 nm) excitation is at least twenty times that for near resonance (457.9 nm) excitation. In resonance only totally symmetric modes are enhanced. The positions of marker band I ((TURN) 1370 cm(' -1)) for both the native and reduced enzymes are lower than expected for high-spin heme proteins indicating a strongly electron donating axial ligand. From shifts in spin-sensitive Raman peaks as the temperature is lowered, a high-spin to low-spin transition of the heme iron is inferred. Raman spectra of chloroperoxidase liganded with small ions indicate that there is a second anion binding site near the heme. Photo-dissociation of CO from reduced chloroperoxidase is observed. The position of marker band I in the CO complex indicates that electron density is transferred from the heme onto the CO. The resonance Raman spectra of chloroperoxidase and cytochrome P-450 are nearly identical and are very different from those of horseradish peroxidase and cytochrome c. These results, particularly for the reduced enzymes, indicate that the heme sites in chloroperoxidase and P -450 are essentially the same. Raman spectra of a number of methemoglobins complexed with various small ions are obtained as a function of temperature in the region of spin-sensitive marker band (II) ((TURN) 1500 cm('-1)) for laser excitation near the Soret absorption band. For certain ligands, H(,2)O, N(,3)('-), OCN('-), OH('-) and SCN('-), the iron spin state changes from high spin to low spin with decreasing temperature. The relative spin concentrations are monitored by measuring the Raman intensity ratio, I(,h)/I(,1), of the high-spin and low -spin versions of marker band (II

  4. Resonant Raman Scattering Studies of Iii-V Semiconductor Microstructures

    NASA Astrophysics Data System (ADS)

    Delaney, Malcolm Emil

    1991-02-01

    Raman spectroscopy, an inelastic light scattering technique, explores III-V semiconductors by conveying crystal lattice structural information and by probing carrier dynamics both directly and via the electron-phonon interaction. We have examined three physical systems accentuating three aspects of Raman utility. Al_{rm x}Ga_{rm 1-x} As alloy work emphasizes electronic behavior, migration enhanced epitaxy (MEE) studies highlight structural results, and a phonon-assisted lasing project underscores electron -phonon interaction. The disorder-induced frequency difference between the dipole-forbidden and dipole-allowed longitudinal optic (LO) modes in Al_{rm x} Ga_{rm 1-x}As alloys has been investigated as a function of laser photon energy, aluminum mole fraction x, and the indirect versus direct nature of the electronic band gap. For the indirect gap alloy, the intermediate resonant state is an X-valley electron effectively localized because of its short inelastic lifetime. Raman scattering via this state is described by a calculation of the Raman susceptibility that considers the random alloy potential generated by local concentration fluctuations. MEE is a new growth technology that can order these materials in two spatial directions. In a GaSb/AlSb system we show Raman evidence of this ordering via observation of zone folded acoustic modes and compare to AlAs/GaAs results. In other work resonant Raman documents the effects on the dipole-forbidden interface mode of a periodic corrugation introduced in AlAs barrier GaAs single quantum wells. Finally, we investigate "phonon-assisted" lasing in photopumped quantum well heterostructure lasers. Resonant Raman is the natural choice to probe this system purported to have an enhanced electron-phonon interaction. For both the AlGaAs/GaAs and AlGaAs/GaAs/InGaAs structures examined, we provide evidence that indicates first order "phonon -assisted" lasing is actually renormalized band gap luminescence filtered by absorption from

  5. Resonance Raman Studies of Bovine and OCTOPUS Visual Pigments

    NASA Astrophysics Data System (ADS)

    Huang, Liewen

    1995-01-01

    We have regenerated bovine and octopus visual pigments with retinals containing isotopic labels at three positions, i.e., 8-^{13}C -11,12-D_2, 10-^{13 }C-11,12-D_2, 11- ^{13}C-11,12-D_2 , 14-^{13}C-11,12 -D_2, for the studies of bound chromophore ethylenic and Schiff base vibrational modes by resonance Raman spectroscopy. Also regenerated were octopus visual pigments with singly or doubly ^{13 }C labeled retinals, i.e., 9-^ {13}C, 10,11-^{13 }C_2, 12,13- ^{13}C_2, 13-^{13}C, 14,15- ^{13}C_2, 14,15-^{13}C_2 -ND, for the studies of vibrational modes in the fingerprint region. We have analyzed the resonance Raman spectra based upon the observation of the response of individual bands in the spectrum of rhodopsin, isorhodopsin, or bathorhodopsin to a particular label. The observed peaks in the fingerprint and ethylenic regions have been tentatively assigned to specific C-C and C=C stretches. We have also studied a model retinal protonated Schiff base analog and its isotopically labeled derivatives as well as calculations using ab initio methods. Based on the vibrational analysis, new criteria to determine the Schiff base C=N configuration from Raman spectroscopy have been developed, and the C=N configuration in octopus rhodopsin, isorhodopsin and bathorhodopsin has been determined. We have continued the resonance Raman study of the Schiff base hydrogen/deuterium exchange for rhodopsin and bacteriorhodopsin by employing the continuous-flow experiment. The exchange of a deuteron on the Schiff base with a proton is very fast, with half-times of 6.9 +/- 0.9 and 1.3 +/- 0.3 ms for rhodopsin and bacteriorhodopsin, respectively, faster than the proton-deuteron exchange rate of a protonated Schiff base in aqueous solution (16 +/- 2 ms). This anomalous result can be understand if a structural water molecule (or molecules) is present next to the protonated Schiff base in the two pigments.

  6. Resonance Raman Scattering Studies of Gallium - - Aluminum-Arsenide Superlattices.

    NASA Astrophysics Data System (ADS)

    Gant, Thomas Andrew

    We have made resonance Raman scattering studies of folded LA phonons and quantized LO phonons in several GaAs-AlAs superlattices. The motivation for this work was to study the electronic structure and the electron -phonon interaction in these structures. The samples were not intentionally doped. The Raman spectra of optic phonons were usually taken at a temperature of 10 K or less. The folded acoustic phonon work was taken at temperatures ranging from 200-300 K in order to enhance the scattering by the thermal factor. Two samples in particular have received very close attention: sample 2292 (50 A GaAs- 20 A AlAs) and sample 3250 (20 A GaAs- 50 A AlAs). In sample 2292 we have made resonance studies of the folded LA phonons and the GaAs -like confined LO_2 mode near the second heavy hole exciton. The results on the folded acoustic phonons show a very strong resonance enhancement for the second order folded phonons, but very little for the first order. An interference between two different scattering channels (the n = 1 light hole and the n = 2 heavy hole subbands) seems to be responsible for this effect. The resonance profile for the LO_2 confined optic phonon in sample 2292 shows 4 peaks in the region from 1.8 eV to 2.05 eV. We have studied the dependence of this resonance profile on the power density. A higher power density was achieved by using the same laser power with a tighter focus. At the higher power density the peak at 1.93 eV (formerly the strongest peak present) vanished. This "bleaching" effect is related to screening due to the higher carrier density. In sample 3250 we have studied the polarization dependence of the resonance profiles of four peaks (LO _2, LO_4, LO_6, and an interface mode) near the lowest direct gap. The A_1 symmetry confined LO modes are seen in both polarized and depolarized geometries, in violation of the usual selection rule (polarized). A mechanism is proposed to explain this result, which has been previously observed by other

  7. Fourier Transform Infrared and Resonance Raman Spectroscopic Studies of Bacteriorhodopsin.

    NASA Astrophysics Data System (ADS)

    Earnest, Thomas Nixon

    Fourier transform infrared and resonance Raman spectroscopy were used to investigate the structure and function of the light-activated, transmembrane proton pump, bacteriorhodopsin, from the purple membrane of Halobacterium halobium. Bacteriorhodopsin (bR) is a 27,000 dalton integral membrane protein consisting of 248 amino acids with a retinylidene chromophore. Absorption of a photon leads to the translocation of one or two protons from the inside of the cell to the outside. Resonance Raman spectroscopy allows for the study of the configuration of retinal in bR and its photointermediates by the selective enhancement of vibrational modes of the chromophore. This technique was used to determine that the chromophore is attached to lysine-216 in both the bR _{570} and the M _{412} intermediates. In bR with tyrosine-64 selectively nitrated or aminated, the chromophore appears to have the same configuration in that bR _{570} (all- trans) and M _{412} (13- cis) states as it does in unmodified bR. Polarized Fourier transform infrared spectroscopy (FTIR) permits the study of the direction of transition dipole moments arising from molecular vibrations of the protein and the retinal chromophore. The orientation of alpha helical and beta sheet components was determined for bR with the average helical tilt found to lie mostly parallel to the membrane normal. The beta sheet structures also exhibit an IR linear dichroism for the amide I and amide II bands which suggest that the peptide backbone is mostly perpendicular to the membrane plane although it is difficult to determine whether the bands originate from sheet or turn components. The orientation of secondary structure components of the C-1 (residues 72-248) and C-2 (residues 1-71) fragments were also investigated to determine the structure of these putative membrane protein folding intermediates. Polarized, low temperature FTIR -difference spectroscopy was then used to investigate the structure of bR as it undergoes

  8. Photodissociation dynamics of dimethylnitrosamine studied by resonance Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Lenderink, Egbert; Wiersma, Douwe A.

    1994-02-01

    The initial molecular dynamics in the dissociative S 1 (n, π *) state of dimethylnitrosamine (DMN) is investigated using resonance Raman spectroscopy. We find that photochemical N-N bond cleavage in DMN proceeds via a bent conformation around the amine N atom, which supports the outcome of ab initio and classical trajectory calculations [M. Persico, I. Cacelli and A. Ferretti, J. Chem. Phys. 94 (1991) 5508]. Additional information is obtained about the other motions that accompany the photodissociation: a stretch of the N-N bond and a change of the NNO angle.

  9. 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.

  10. Theoretical study of the resonance Raman spectra for meso-tetrakis(3,5-di-tertiarybutylphenyl)-porphyrin.

    PubMed

    Zheng, Ren-hui; Wei, Wen-mei; Zhu, Li-li; Shi, Qiang

    2014-12-10

    Applying time-dependent density functional theory (TDDFT), we study the resonance Raman spectra for the Q and B bands of the meso-tetrakis(3,5-di-tertiarybutylphenyl)-porphyrin (H2TBPP) molecule including both Raman A term (Franck-Condon term) and Raman B term (Herzberg-Teller term) contributions. It is found that Raman B term can be one order of magnitude larger than Raman A term and dominates resonance Raman for the Q band resonance. In comparison with the recent experimental Raman spectra of H2TBPP with incident light frequency 532nm, we predict the absence of 1580cm(-1) band in the resonance Raman spectra which agrees well with the experimental results, whereas the previous theoretical calculation using non-resonance strategy failed to do so.

  11. Resonance Raman spectroscopy.

    PubMed

    Robert, Bruno

    2009-01-01

    Resonance Raman spectroscopy may yield precise information on the conformation of, and on the interactions assumed by, the chromophores involved in the first steps of the photosynthetic process, whether isolated in solvents, embedded in soluble or membrane proteins, or, as shown recently, in vivo. By making use of this technique, it is possible, for instance, to relate the electronic properties of these molecules to their structure and/or the physical properties of their environment, or to determine subtle changes of their conformation associated with regulatory processes. After a short introduction to the physical principles that govern resonance Raman spectroscopy, the information content of resonance Raman spectra of chlorophyll and carotenoid molecules is described in this review, together with the experiments which helped in determining which structural parameter each Raman band is sensitive to. A selection of applications of this technique is then presented, in order to give a fair and precise idea of which type of information can be obtained from its use in the field of photosynthesis.

  12. Comparative study of resonance Raman and surface-enhanced resonance Raman chlorophyll a spectra using soret and red excitation

    SciTech Connect

    Thomas, L.L.; Kim, Jaeho; Cotton, T.M. )

    1990-12-05

    Surface-enhanced resonance Raman scattering (SERRS) spectra are reported for chlorophyll a adsorbed on a silver electrode at 298 and 77 K with 406.7-, 457.9-, 514.5-, and 647.1-nm excitation. Submerging the electrode in degassed water at 298 K was found to improve the spectral quality by minimizing sample heating and photooxidation. Spectral intensities and peak resolutions were greater at all excitation wavelengths at liquid nitrogen temperature. Most significantly, roughened silver at the low temperature quenched the fluorescence accompanying red excitation and minimized sample photooxidation, resulting in richly detailed SERRS spectra of chlorophyll a. The close correspondence between chlorophyll a resonance Raman (RR) and SERRS spectra suggests that an electromagnetic mechanism is the major source of the surface enhancement, rather than a chemical mechanism (e.g. a charge-transfer complex between chlorophyll a and the metal). The spectral similarities, together with the presence of the MgN{sub 4} vibration band in the SERRS spectra, also provide evidence that structural alterations (e.g. cleavage of ring V or loss of Mg) do not occur in chlorophyll a after adsorption at the electrode surface. A distinctive SERRS spectrum was obtained for each excitation wavelength. Selective excitation within the various electronic transitions can thus be utilized to verify assignments of the vibrational modes of chlorophyll a and to monitor its interactions and photochemical behavior in biomimetic systems.

  13. Resonance Raman spectroscopic evaluation of skin carotenoids as a biomarker of carotenoid status for human studies

    USDA-ARS?s Scientific Manuscript database

    Resonance Raman Spectroscopy (RRS) is a non-invasive method that has been developed to assess carotenoid status in human tissues including human skin in vivo. Skin carotenoid status, as assessed by RRS, has been suggested as a promising biomarker for use in human studies. This manuscript describes...

  14. Vacuum ultraviolet resonance Raman studies of the excited electronic states of ethylene

    NASA Astrophysics Data System (ADS)

    Sension, Roseanne J.; Hudson, Bruce S.

    1989-02-01

    A resonance Raman study of ethylene has been performed with the use of excitation wavelengths ranging from 200 to 141 nm. Excitation resonant with the V(pi pi -asterisk) state results in Raman spectra exhibiting intensity in the C = C stretching vibration, the CH2 symmetric scissors vibration, the CH2 torsional vibration and the CH2 out-of-plane wagging vibrations. These spectra confirm that the V state is strongly twisted about the C-C bond. They also indicate that the C = CH2 groups are no longer planar in the V state. The spectrum obtained in resonance with the (pi 3d) Rydberg transitions once again exhibits activity in the CH2 symmetric scissors mode.

  15. 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 CO2 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 CO2, large photoelectrocatalytic effect for the reduction of CO2 was observed in the presence of surface adsorbed methylviologen, which functions as a mediator for the photoexcited electron transfer from silver metal to CO2 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.

  16. Interaction of proflavine with DNA studied by colloid surface enhanced resonance Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Koglin, E.; Séquaris, J.-M.

    1986-03-01

    The interaction of the mutagenic highly fluourescing proflavine (3,6-diaminoacridine: PF) dye with calf thymus DNA has been studied by Surface Enhanced Resonance Raman Scattering (SERRS). Since the Ag-colloids almost completely quenche the strong fluorescence it is possible to obtain excellent vibrational spectra in a wide frequency range providing valuable information about the intercalation. The intercalation does not affect the vibrational frequencies of the proflavine dye. On the other hand, intensity changes are observed in some of the ring- and NH 2-modes of proflavine upon intercalation. This Raman hypochromism is characteristic for ring stacking interactions and in the SERRS spetroscopy for an additional effects of the dye orientation to the surface.

  17. A resonance Raman spectroscopic study of the quadruplex form of polyriboinosinic acid.

    PubMed

    Wheeler, V; Jollès, B; Miskovsky, P; Chinsky, L

    1996-08-01

    The four stranded form of polyriboinosinic acid, or poly(rl), formed under conditions of high ionic strength, has been studied principally by resonance Raman spectroscopy excited in the ultraviolet absorbent band of the hypoxanthine residues. UV Absorption and circular dichroism studies were made, principally in order to verify the presence of the quadruplex form at the low concentrations of poly(rl) used, and a trial experiment with the structural probe Tb3+ was also performed. Experimental evidence is found for highly stacked metastable forms present at low concentrations of polynucleotide, which are destroyed by heating in favor of the two well known forms.

  18. Intermediate and stable redox states of cytochrome c studied by low temperature resonance Raman spectroscopy.

    PubMed Central

    Cartling, B

    1983-01-01

    Stabilized intermediate redox states of cytochrome c are generated by radiolytic reduction of initially oxidized enzyme in glass matrices at liquid nitrogen temperature. In the intermediate states the heme group is reduced by hydrated electrons, whereas the protein conformation is restrained close to its oxidized form by the low-temperature glass matrix. The intermediate and stable redox states of cytochrome c at neutral and alkaline pH are studied by low-temperature resonance Raman spectroscopy using excitations in resonance with the B (Soret) and Q1 (beta) optical transitions. The assignments of the cytochrome c resonance Raman bands are discussed. The observed spectral characteristics of the intermediate states as well as of the alkaline transition in the oxidized state are interpreted in terms of oxidation-state marker modes, spin-state marker modes, heme iron--axial ligand stretching modes, totally symmetric in-plane porphyrin modes, nontotally symmetric in-plane modes, and out-of-plane modes. PMID:6311300

  19. Amantadine DNA interaction as studied by classical and resonance Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Staničová, J.; Fabriciová, G.; Chinsky, L.; Šutiak, V.; Miškovský, P.

    1999-03-01

    The interaction of the antiviral agent amantadine with calf thymus DNA was studied by classical and UV-resonance Raman spectroscopy. It was found that: (i) the drug interacts with purine bases adenine and guanine via hydrogen bonds formation between N7 positions of purines and amino group of amantadine and (ii) the interaction leads to partial DNA structure change, which is demonstrated by a deformation of the hydrogen bonds of the A-T base pairs and by a partial deformation of the sugar-phosphate backbone of DNA, which does not lead to the DNA conformation transition.

  20. 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.

  1. 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.

  2. Excited state structures and decay dynamics of 1,3-dimethyluracils in solutions: resonance Raman and quantum mechanical calculation study.

    PubMed

    Li, Ming-Juan; Liu, Ming-Xia; Zhao, Yan-Ying; Pei, Ke-Mei; Wang, Hui-Gang; Zheng, Xuming; Fang, Wei Hai

    2013-10-03

    The resonance Raman spectroscopic study of the excited state structural dynamics of 1,3-dimethyluracil (DMU), 5-bromo-1,3-dimethyluracil (5BrDMU), uracil, and thymine in water and acetonitrile were reported. Density functional theory calculations were carried out to help elucidate the ultraviolet electronic transitions associated with the A-, and B-band absorptions and the vibrational assignments of the resonance Raman spectra. The effect of the methylation at N1, N3 and C5 sites of pyrimidine ring on the structural dynamics of uracils in different solvents were explored on the basis of the resonance Raman intensity patterns. The relative resonance Raman intensities of DMU and 5BrDMU are computed at the B3LYP-TD level. Huge discrepancies between the experimental resonance Raman intensities and the B3LYP-TD predicted ones were observed. The underlying mechanism was briefly discussed. The decay channel through the S1((1)nπ*)/S2((1)ππ*) conical intersection and the S1((1)nπ*)/T1((3)ππ*) intersystem crossing were revealed by using the CASSCF(8,7)/6-31G(d) level of theory calculations.

  3. 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.

  4. Elementary excitations in charge-tunable InGaAs quantum dots studied by resonant Raman and resonant photoluminescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Köppen, Tim; Franz, Dennis; Schramm, Andreas; Heyn, Christian; Gutjahr, Johann; Pfannkuche, Daniela; Heitmann, Detlef; Kipp, Tobias

    2011-04-01

    We report on resonant optical spectroscopy of self-assembled InGaAs quantum dots in which the number of electrons can accurately be tuned to N=0,1,2 by an external gate voltage. Polarization, wave vector, and magnetic field dependent measurements enable us to clearly distinguish between resonant Raman and resonant photoluminescence processes. The Raman spectra for N=1 and 2 electrons considerably differ from each other. In particular, for N=2, the quantum-dot He, the spectra exhibit both singlet and triplet transitions reflecting the elementary many-particle interaction. Also the resonant photoluminescence spectra are significantly changed by varying the number of electrons in the QDs. For N=1 we observe complex spectra possibly induced by strong polaronic effects that are suppressed for N=2.

  5. a Study of the Hydroxycyclohexadienyl Radical Absorption Using Time-Resolved Resonance Raman Spectroscopy

    NASA Astrophysics Data System (ADS)

    O'Donnell, Deanna M.; Tripathi, G. N. R.; Brinkmann, Nicole R.

    2009-06-01

    Thus far there has been little understanding of the vibrational spectra, structure and electronic absorption of hydroxycyclohexadienyl radicals in water. They are primary chemical species formed on interaction of radiation with aqueous solutions containing aromatic molecules. We have applied time- resolved resonance Raman (TR-RR) spectroscopy to structurally identify isomers of cyclohexadienyl radicals formed in the pulse radiolysis, using aqueous benzoate solutions as a model system. An early ESR study ((Eiben, K; Fessenden, R.W.; J. Phys. Chem. 1971, 75, 1186-1201) has shown that a mixture of three benzoate hydroxycyclohexadienyl radical isomers: ortho-, meta- and para- are formed upon electron irradiation of N_{2}O saturated benzoate solution. Their collective transient absorption is believed to exhibit a single broad band in the near UV region (λ_{max} = 330 nm, ɛ_{330} = 3800 M^{-1}cm^{-1}). To extract the single isomeric contribution to this collective absorption, we applied TR-RR at various wavelengths within the broad transient absorption range looking for the characteristic indication of each individual isomer. Raman signals of various para-substituted benzoates were also collected to aid in the vibrational studies of the aforementioned benzoate hydroxycyclohexadienyl radicals.

  6. 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.

  7. 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.

  8. Solvatochromism of 9,10-phenanthrenequinone: An electronic and resonance Raman spectroscopic study

    SciTech Connect

    Ravi Kumar, Venkatraman; Rajkumar, Nagappan; Umapathy, Siva

    2015-01-14

    Solvent effects play a vital role in various chemical, physical, and biological processes. To gain a fundamental understanding of the solute-solvent interactions and their implications on the energy level re-ordering and structure, UV-VIS absorption, resonance Raman spectroscopic, and density functional theory calculation studies on 9,10-phenanthrenequinone (PQ) in different solvents of diverse solvent polarity has been carried out. The solvatochromic analysis of the absorption spectra of PQ in protic dipolar solvents suggests that the longest (1n-π{sup 1}*; S{sub 1} state) and the shorter (1π-π{sup 1}*; S{sub 2} state) wavelength band undergoes a hypsochromic and bathochromic shift due to intermolecular hydrogen bond weakening and strengthening, respectively. It also indicates that hydrogen bonding plays a major role in the differential solvation of the S{sub 2} state relative to the ground state. Raman excitation profiles of PQ (400–1800 cm{sup −1}) in various solvents followed their corresponding absorption spectra therefore the enhancements on resonant excitation are from single-state rather than mixed states. The hyperchromism of the longer wavelength band is attributed to intensity borrowing from the nearby allowed electronic transition through vibronic coupling. Computational calculation with C{sub 2ν} symmetry constraint on the S{sub 2} state resulted in an imaginary frequency along the low-frequency out-of-plane torsional modes involving the C=O site and therefore, we hypothesize that this mode could be involved in the vibronic coupling.

  9. Resonance Raman spectroscopic and density functional theory study of p-nitroacetophenone (PNAP)

    NASA Astrophysics Data System (ADS)

    Pei, Kemei; Ma, Yufang; Zheng, Xuming; Li, Haiyang

    2007-03-01

    Resonance Raman spectra of p-nitroacetophenone(PNAP) have been obtained in resonance with the charge-transfer (CT) band using 252.7, 266 and 273.9 nm in methanol solvent. The spectra indicate that the Franck-Condon region photodissociation dynamics have multidimensional character with motion mainly along the C dbnd O stretching ν8(1691 cm -1) and the benzene ring stretch ν10(1593 cm -1). A preliminary resonance Raman intensity analysis was done and the results for PNAP were compared with nitrobenzene and aceptophenone. Our results indicate that -NO 2 is more photoactive than -COCH 3. The isomerization process of PNAP takes place somewhere after the wave packet leaves the Franck-Condon region.

  10. 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.

  11. G-band resonant Raman study of 62 isolated single-wall carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Jorio, A.; Souza Filho, A. G.; Dresselhaus, G.; Dresselhaus, M. S.; Swan, A. K.; Ünlü, M. S.; Goldberg, B. B.; Pimenta, M. A.; Hafner, J. H.; Lieber, C. M.; Saito, R.

    2002-04-01

    We report G-band resonance Raman spectra of single-wall carbon nanotubes (SWNTs) at the single-nanotube level. By measuring 62 different isolated SWNTs resonant with the incident laser, and having diameters dt ranging between 0.95 nm and 2.62 nm, we have conclusively determined the dependence of the two most intense G-band features on the nanotube structure. The higher-frequency peak is not diameter dependent (ω+G=1591 cm-1), while the lower-frequency peak is given by ω-G=ω+G-C/d2t, with C being different for metallic and semiconducting SWNTs (CM>CS). The peak frequencies do not depend on nanotube chiral angle. The intensity ratio between the two most intense features is in the range 0.1resonance conditions, i.e., SWNTs for which the incident photons are in resonance with the ES44 interband transition and scattered photons are in resonance with ES33. Since the Eii values depend sensitively on both nanotube diameter and chirality, the (n,m) SWNTs that should exhibit such a special G-band spectra can be predicted by resonance Raman theory. The agreement between theoretical predictions and experimental observations about these special G-band phenomena gives additional support for the (n,m) assignment from resonance Raman spectroscopy.

  12. Resonance Raman studies of the HOOP modes in octopus bathorhodopsin with deuterium-labeled retinal chromophores.

    PubMed

    Deng, H; Manor, D; Weng, G; Rath, P; Koutalos, Y; Ebrey, T; Gebhard, R; Lugtenburg, J; Tsuda, M; Callender, R H

    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-1 for octopus bathorhodopsin. On the basis of their isotopic shifts upon deuterium labeling, we have assigned the band at 887 cm-1 to C10H and C14H HOOP modes, and the band at 940 cm-1 to C11H = C12H Au-like HOOP mode. Except for a 26 cm-1 downward shift, the C11H = C12H Au-like wag appears to be little disturbed in octopus bathorhodopsin from the chromophore in solution since its changes upon deuterium labeling are close to those found in solution model-compound studies. We found also that the C10H and C14H HOOP wags are also similar to those in the model-compound studies. However, we have found that the interaction between the C7H and C8H HOOP internal coordinates of the chromophore in octopus bathorhodopsin is different from that of the chromophore in solution. The intensity of the C11H = C12H and the other HOOP modes suggests that the chromophore of octopus bathorhodopsin is somewhat torsionally distorted from a planar trans geometry. Importantly, a twist about C11 = C12 double bond is inferred. Such a twist breaks the local symmetry, resulting in the observation of the normally Raman-forbidden C11H = C12H Au-like HOOP mode. The twisted nature of the chromophore, semiquantitatively discussed here, likely affects the lambda max of the chromophore and its enthalpy.(ABSTRACT TRUNCATED AT 250 WORDS)

  13. Resonance Raman study of the dark-adapted form of the purple membrane protein.

    PubMed

    Aton, B; Doukas, A G; Callender, R H; Becher, B; Ebrey, T G

    1979-02-26

    The resonance Raman spectrum of the dark-adapted form of the purple membrane protein (bacteriorhodopsin) has been obtained and is compared to the light-adapted pigment and model chromophore spectra. As in the light-adapted form, the chromophore-protein linkage is found to be a protonated Schiff base. Electron delocalization appears to play the dominant role in color regulation. The dark-adapted spectrum indicates a conformation closer to 13-cis than the light-adapted spectrum.

  14. Conformational study of the chromophore of C-phycocyanin by resonance raman and electronic absorption spectroscopy.

    NASA Astrophysics Data System (ADS)

    Margulies, L.; Toporowicz, M.

    1988-05-01

    The conformation of the chromophore of C-phycocyanin (PC) was investigated by using electronic absorption and resonance Raman spectroscopy, and theoretical calculations. Using an A-dihydrobilindione as model compound, the syn, syn, syn conformation was established for the isolated chromophore in solution. For the native PC, the best results were obtained by considering the syn, syn, anti conformation, although the possibility of having a syn, anti, anti conformation could not be excluded.

  15. Resonance Raman and photophysical studies of transition metal complexes in solution and entrapped in zeolites

    SciTech Connect

    Kincaid, J.R.

    1991-03-29

    This program is subdivided into two major categories: (1) the study of complexes of Ru(II) in fluid solution and (2) the investigation of the effects of incorporation of such complexes into organized assemblies. In the first part of this report, clear evidence is presented for the somewhat unexpected observation of quite specific localization of excited state electron density on a rather small fragment of the coordinated asymmetric bidentate ligand. Thus far, two examples of this behavior have been documented and the results will soon be submitted for publication. The second part of the report describes continuing efforts to develop effective methods for selective preparation of heteroleptic complexes within the supercages of Y-type zeolite. One manuscript has been submitted for publication and a second is now in preparation. Also described in this section of the report are Resonance Raman studies of Ru(bipyrazine){sub 3}{sup 2+} in solutions of varying concentrations of H{sub 2}SO{sub 4}; from 0 to 96%.

  16. Resonance Raman spectroscopic evaluation of skin carotenoids as a biomarker of carotenoid status for human studies.

    PubMed

    Mayne, Susan T; Cartmel, Brenda; Scarmo, Stephanie; Jahns, Lisa; Ermakov, Igor V; Gellermann, Werner

    2013-11-15

    Resonance Raman spectroscopy (RRS) is a non-invasive method that has been developed to assess carotenoid status in human tissues including human skin in vivo. Skin carotenoid status has been suggested as a promising biomarker for human studies. This manuscript describes research done relevant to the development of this biomarker, including its reproducibility, validity, feasibility for use in field settings, and factors that affect the biomarker such as diet, smoking, and adiposity. Recent studies have evaluated the response of the biomarker to controlled carotenoid interventions, both supplement-based and dietary [e.g., provision of a high-carotenoid fruit and vegetable (F/V)-enriched diet], demonstrating consistent response to intervention. The totality of evidence supports the use of skin carotenoid status as an objective biomarker of F/V intake, although in the cross-sectional setting, diet explains only some of the variation in this biomarker. However, this limitation is also a strength in that skin carotenoids may effectively serve as an integrated biomarker of health, with higher status reflecting greater F/V intake, lack of smoking, and lack of adiposity. Thus, this biomarker holds promise as both a health biomarker and an objective indicator of F/V intake, supporting its further development and utilization for medical and public health purposes.

  17. Resonance Raman Spectroscopic Evaluation of Skin Carotenoids as a Biomarker of Carotenoid Status for Human Studies

    PubMed Central

    Mayne, Susan T.; Cartmel, Brenda; Scarmo, Stephanie; Jahns, Lisa; Ermakov, Igor V.; Gellermann, Werner

    2013-01-01

    Resonance Raman Spectroscopy (RRS) is a non-invasive method that has been developed to assess carotenoid status in human tissues including human skin in vivo. Skin carotenoid status has been suggested as a promising biomarker for human studies. This manuscript describes research done relevant to the development of this biomarker, including its reproducibility, validity, feasibility for use in field settings, and factors that affect the biomarker such as diet, smoking, and adiposity. Recent studies have evaluated the response of the biomarker to controlled carotenoid interventions, both supplement-based and dietary [e.g., provision of a high-carotenoid fruit and vegetable (F/V)-enriched diet], demonstrating consistent response to intervention. The totality of evidence supports the use of skin carotenoid status as an objective biomarker of F/V intake, although in the cross-sectional setting, diet explains only some of the variation in this biomarker. However, this limitation is also a strength in that skin carotenoids may effectively serve as an integrated biomarker of health, with higher status reflecting greater F/V intake, lack of smoking, and lack of adiposity. Thus, this biomarker holds promise as both a health biomarker and an objective indicator of F/V intake, supporting its further development and utilization for medical and public health purposes. PMID:23823930

  18. 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.

  19. 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.

  20. Vibrational relaxation of nascent diiodide ions studied by femtosecond transient resonance impulsive stimulated Raman scattering (TRISRS); experiment and simulation

    NASA Astrophysics Data System (ADS)

    Banin, Uri; Kosloff, Ronnie; Ruhman, Sanford

    1994-06-01

    Impulsive stimulated Raman scattering performed with femtosecond pulses on resonance with an electronic transition, comprises an all time domain Raman technique providing vibrational dynamics of the ground state chromophore. We report the application of this technique to record transient Raman responses of nascent diiodide ions, undergoing rapid vibrational relaxation following triiodide photodissociation in ethanol solution. Like other Fourier spectroscopic methods, this spectroscopy maximizes high simultaneous time and frequency resolution, making it well adapted, and in the present study exclusively capable, for recovering vibrational dynamics of highly excited molecular populations in transition. Master equation simulations of vibrational relaxation, coupled to quantum wave-packet representation of the light-matter interactions, are combined to provide a semi-quantitative analysis of the experimental results. Previous assignment of spectral narrowing of the nascent diiodide absorption to vibrational relaxation is bourn out by simulations. Inherent limitations and fortitudes of the TRISRS method are theoretically investigated and discussed.

  1. Surface-enhanced resonance Raman study of the photoreduction of methylviologen on a p-InP semiconductor electrode

    SciTech Connect

    Feng, Q.; Cotton, T.M.

    1986-03-13

    The redox reactions of methylviologen (MV) at a silver electrode and at a p-InP electrode have been studied by cyclic voltammetry and Raman spectroscopy. By deposition of a silver island overlayer onto a p-InP semiconductor electrode the surface enhancement effect was obtained, allowing the MV reduction products formed at the semiconductor electrode to be monitored in situ. The photovoltaic response on p-InP electrode was not perturbed by the presence of the silver overlayer. Surface-enhanced resonance Raman (SERR) spectroscopy has verified the adsorption of the products from the reduction reactions MV/sup 2 +/ + e/sup -/ ..-->.. MV/sup +/. and MV/sup +/. + e/sup -/ ..-->.. MV/sup 0/. The Raman spectrum of one-electron and two-electron (MV/sup 0/) reduced methylviologen was obtained by exhaustive electrolysis in acetonitrile solution to provide an assignment of the surface spectra. 31 references, 4 figures.

  2. UV Resonance Raman and DFT Studies of Arginine Side Chains in Peptides: Insights into Arginine Hydration

    PubMed Central

    Hong, Zhenmin; Wert, Jonathan; Asher, Sanford A.

    2013-01-01

    We examined the UV resonance Raman (UVRR) spectra of four models of the arg side chain, guanidinium (gdn), ethylguanidinium (EG), arginine (arg) and Ac-arg-OMe (AAO) in H2O and D2O, in order to identify spectral markers that report on the environment of the arg side chain. To elucidate the resonance Raman enhancement mechanism of the arg side chain, we used DFT to calculate the equilibrium geometries of the electronic ground state and the first excited state. We determined the vibrational mode frequencies of the ground state and the first derivative of the first electronic excited state potential energy with respect to each vibrational normal mode of the electronic ground state at the electronic ground state equilibrium geometry. The DFT calculations and the potential energy distributions reveal that, in addition to the gdn group C-N stretching vibrations, the C-N bond stretching vibration of the gdn group-methylene linkage is also strongly resonance enhanced in EG, arg and AAO. From the UVRR spectra, we find that the Raman cross section and frequency of the ~1170 cm−1 vibration of the arg side chain depends on its hydration state and can be used to determine the hydration state of the arg side chain in peptides and proteins. We examined the hydration of the arg side chain in two polyala peptides and found that in the α-helical conformation the arg side chain in the AEP peptide (sequence: A9RA3EA4RA2) is less hydrated than that in the AP peptide (sequence: A8RA4RA4RA2). PMID:23676082

  3. Infrared, Raman and Magnetic Resonance Spectroscopic Study of SiO2:C Nanopowders

    NASA Astrophysics Data System (ADS)

    Savchenko, Dariya; Vorliček, Vladimir; Kalabukhova, Ekaterina; Sitnikov, Aleksandr; Vasin, Andrii; Kysil, Dmytro; Sevostianov, Stanislav; Tertykh, Valentyn; Nazarov, Alexei

    2017-04-01

    Optical and magnetic properties of SiO2:C nanopowders obtained by chemical and thermal modification of fumed silica were studied by Fourier transform infrared spectroscopy, Raman, continuous wave (CW) electron paramagnetic resonance (EPR), echo-detected EPR and pulsed electron nuclear double resonance (ENDOR) spectroscopy. Two overlapping signals of Lorentzian lineshape were detected in CW EPR spectra of the initial SiO2:C. The EPR signal at g = 2.0055(3) is due to the silicon dangling bonds, which vanishes after thermal annealing, and the second EPR signal at g = 2.0033(3) was attributed to the carbon-related defect (CRD). The annealing of the SiO2:C samples gives rise to the increase of the CRD spin density and shift to the higher g-values due to the appearance of the oxygen in the vicinity of the CRD. Based on the temperature-dependent behavior of the CRD EPR signal intensity, linewidth and resonance field position we have attributed it to the spin system with non-localized electrons hopping between neighboring carbon dangling bonds, which undergo a strong exchange interaction with a localized spin system of carbon nanodots. The observed motional narrowing of the CRD EPR signal in the temperature interval from 4 to 20 K indicates that electrons are mobile at 4 K which can be explained by a quantum character of the conductivity in the vicinity of the carbon layer. The electrons trapped in quantum wells move from one carbon nanodot to another by hopping process through the energy barrier. The fact that echo-detected EPR signal at g = 2.0035(3) was observed in SiO2:C sample annealed at T ann ≥ 700 °C serves as evidence that non-localized electrons coexist with localized electrons that have the superhyperfine interaction with surrounding 13C and 29Si nuclei located at the SiO2:C interface. The presence of the superhyperfine interaction of CRD with 1H nuclei indicates the existence of hydrogenated regions in SiO2:C sample.

  4. Infrared, Raman and Magnetic Resonance Spectroscopic Study of SiO2:C Nanopowders.

    PubMed

    Savchenko, Dariya; Vorliček, Vladimir; Kalabukhova, Ekaterina; Sitnikov, Aleksandr; Vasin, Andrii; Kysil, Dmytro; Sevostianov, Stanislav; Tertykh, Valentyn; Nazarov, Alexei

    2017-12-01

    Optical and magnetic properties of SiO2:C nanopowders obtained by chemical and thermal modification of fumed silica were studied by Fourier transform infrared spectroscopy, Raman, continuous wave (CW) electron paramagnetic resonance (EPR), echo-detected EPR and pulsed electron nuclear double resonance (ENDOR) spectroscopy. Two overlapping signals of Lorentzian lineshape were detected in CW EPR spectra of the initial SiO2:C. The EPR signal at g = 2.0055(3) is due to the silicon dangling bonds, which vanishes after thermal annealing, and the second EPR signal at g = 2.0033(3) was attributed to the carbon-related defect (CRD). The annealing of the SiO2:C samples gives rise to the increase of the CRD spin density and shift to the higher g-values due to the appearance of the oxygen in the vicinity of the CRD. Based on the temperature-dependent behavior of the CRD EPR signal intensity, linewidth and resonance field position we have attributed it to the spin system with non-localized electrons hopping between neighboring carbon dangling bonds, which undergo a strong exchange interaction with a localized spin system of carbon nanodots. The observed motional narrowing of the CRD EPR signal in the temperature interval from 4 to 20 K indicates that electrons are mobile at 4 K which can be explained by a quantum character of the conductivity in the vicinity of the carbon layer. The electrons trapped in quantum wells move from one carbon nanodot to another by hopping process through the energy barrier. The fact that echo-detected EPR signal at g = 2.0035(3) was observed in SiO2:C sample annealed at T ann ≥ 700 °C serves as evidence that non-localized electrons coexist with localized electrons that have the superhyperfine interaction with surrounding (13)C and (29)Si nuclei located at the SiO2:C interface. The presence of the superhyperfine interaction of CRD with (1)H nuclei indicates the existence of hydrogenated regions in SiO2:C sample.

  5. 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.

  6. Resonance Raman spectroscopy in twisted bilayer graphene

    NASA Astrophysics Data System (ADS)

    Righi, A.; Venezuela, P.; Chacham, H.; Costa, S. D.; Fantini, C.; Ruoff, R. S.; Colombo, L.; Bacsa, W. S.; Pimenta, M. A.

    2013-12-01

    In this work we study the Raman spectra of twisted bilayer graphene samples, with different twisting angles, by changing the incident laser energy between 2.54 and 4.14 eV. The spectra exhibit a number of extra peaks, classified in different families, each one associated with bilayer graphenes with different twisting rotational angles. We theoretically analyze the laser energy dependence of these extra peaks considering a set of discrete wavevectors within the interior of the Brillouin zone of graphene, which activate special double-resonance Raman processes. Our result show a nice qualitative agreement between the experimental and simulated spectra, demonstrating that these extra peaks are indeed ascribed to an umklapp double-resonance process in graphene systems.

  7. Comparative resonance Raman study of cytochrome c oxidase from beef heart and Paracoccus denitrificans.

    PubMed

    Heibel, G E; Hildebrandt, P; Ludwig, B; Steinrücke, P; Soulimane, T; Buse, G

    1993-10-12

    Well-resolved, Soret band excited resonance Raman spectra were measured from the fully oxidized and fully reduced cytochrome c oxidase from beef heart and Paracoccus denitrificans. The vibrational patterns in the marker band region (1450-1700 cm-1) were analyzed, and a complete assignment of heme a and heme a3 vibrational modes is presented, permitting a detailed structural comparison of the mammalian and bacterial enzymes. Similar frequencies of the porphyrin modes for the reduced heme a and the reduced and oxidized heme a3 are found, indicating a close relationship of the ground-state conformations in all oxidase species studied. In oxidized heme a, however, significant frequency differences are observed and interpreted in terms of a ruffled porphyrin structure in the three- and two-subunit forms of the Paracoccus enzyme compared to the planar heme a of beef heart oxidase. The structural distortions, which also perturb the conformation of the formyl substituent and its electronic coupling with the porphyrin, reflect the specific heme-protein interactions at heme a. Since in the fully reduced state heme a appears to be largely planar in all oxidase species, the redox-linked conformational transition requires a more drastic rearrangement of the heme a-protein interactions in the bacterial than in the mammalian oxidase. For both heme a and heme a3 in the reduced state and for heme a3 in the oxidize state, frequency, intensity, and bandwidth differences of the formyl stretching vibration and intensity differences of some porphyrin modes are noted between the three oxidase forms. The same modes are also affected by quaternary structure changes in the bovine oxidase caused by different detergents and isolation procedures. These effects are attributed to differences of the dielectric properties of the heme environment, due to subtle structural changes in the heme pockets, induced by protein-protein interactions of subunit III with subunits I and/or II.

  8. Perspective: Two-dimensional resonance Raman spectroscopy

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

    Two-dimensional resonance Raman (2DRR) spectroscopy has been developed for studies of photochemical reaction mechanisms and structural heterogeneity in complex systems. The 2DRR method can leverage electronic resonance enhancement to selectively probe chromophores embedded in complex environments (e.g., a cofactor in a protein). In addition, correlations between the two dimensions of the 2DRR spectrum reveal information that is not available in traditional Raman techniques. For example, distributions of reactant and product geometries can be correlated in systems that undergo chemical reactions on the femtosecond time scale. Structural heterogeneity in an ensemble may also be reflected in the 2D spectroscopic line shapes of both reactive and non-reactive systems. In this perspective article, these capabilities of 2DRR spectroscopy are discussed in the context of recent applications to the photodissociation reactions of triiodide and myoglobin. We also address key differences between the signal generation mechanisms for 2DRR and off-resonant 2D Raman spectroscopies. Most notably, it has been shown that these two techniques are subject to a tradeoff between sensitivity to anharmonicity and susceptibility to artifacts. Overall, recent experimental developments and applications of the 2DRR method suggest great potential for the future of the technique.

  9. 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).

  10. 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.

  11. Study of the orientational ordering of carotenoids in lipid bilayers by resonance-Raman spectroscopy.

    PubMed Central

    van de Ven, M; Kattenberg, M; van Ginkel, G; Levine, Y K

    1984-01-01

    The orientational ordering of beta-carotene and crocetin embedded in lamellar model membranes has been investigated by angle-resolved resonance Raman scattering at a temperature well above the phase transition of the lipid chains. It is shown that the ordering of the carotenoids is dependent on the chemical composition of the lipid bilayers. The orientational distribution functions found clearly show that beta-carotene is oriented parallel to the bilayer plane (dioleoyl lecithin) or perpendicular to it (soybean lecithin). For dimyristoyl lecithin at 40 degrees C, egg-lecithin, and digalactosyl diacylglycerol two maxima were found in the orientational distribution: one parallel and one perpendicular to the bilayer surface. Crocetin embedded in soybean lecithin bilayers yields a similar bimodal distribution function. Because of rapid photodegradation no results could be obtained for spirilloxanthin. PMID:6743750

  12. Absorption and resonance Raman study of the pyromellitic diahydride anion via density functional theory

    NASA Astrophysics Data System (ADS)

    Andruniow, T.; Pawlikowski, M.

    2000-05-01

    The electronic structure of the low-energy states of the pyromellitic diahydride (PMDA) anion is investigated in terms of the VWN (Vosco-Wilk-Nusair) the BP (Becke-Perdew) and the B3LYP density functional (DF) methods employed with 6-31G * basis sets. All the methods are shown to reproduce correctly the absorption and resonance Raman spectra in the region corresponding to the low-energy 1 2Au→1 2B3g transition. The discrepancies between the theory and experiment are attributed to a (weak) Dushinsky effect predominately due to a mixing of the ν3=1593 cm -1 and ν4=1342 cm -1 vibrations in the 1 2B3 g state of the PMDA radical.

  13. 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.

  14. 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. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. Dephasing and resonance electronic Raman scattering

    NASA Astrophysics Data System (ADS)

    Koningstein, J. A.

    1988-05-01

    The intensity of the resonance electronic Raman spectrum of terbium aluminum garnet is discussed in terms of radiative, non-radiative and pure electronic dephasing processes which govern the width of the resonating excited electronic state. As a result of fast electronic dephasing in comparison to the other processes, the enhancement of the intensity of the electronic Raman band of the terbium ion is suppressed.

  16. 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.

  17. DNA-wrapped carbon nanotubes aligned in stretched gelatin films: Polarized resonance Raman and absorption spectroscopy study

    NASA Astrophysics Data System (ADS)

    Glamazda, A. Yu.; Plokhotnichenko, A. M.; Leontiev, V. S.; Karachevtsev, V. A.

    2017-09-01

    We present the study of DNA-wrapped single-walled carbon nanotubes (SWNTs) embedded in the stretched gelatin film by the polarized resonance Raman spectroscopy and visible-NIR optical absorption. The polarized dependent absorption spectra taken along and normal to the stretching direction demonstrate a comparatively high degree of the alignment of isolated SWNTs in the gelatin matrix. The analysis of Raman spectra of isolated SWNTs in the gelatin stretched films showed that the degree of the alignment of carbon nanotubes along the stretching direction is about 62%. The dependence of the peak position of G+-band in Raman spectra on the polarization angle θ between the polarization of the incident light and the direction of the stretching of films was revealed. This shift is explained by the different polarization dependence of the most intensive A and E1 symmetry modes within the G+-band. The performed studies of embedded DNA-wrapped nanotubes in the gelatin film show the simple method for obtaining the controlled ordered biocompatible nanotubes inside a polymer matrix. It can be used for manufacturing sizable flexible self-transparent films with integrated nanoelectrodes.

  18. Intermolecular hydrogen bonding in chlorine dioxide photochemistry: A time-resolved resonance Raman study

    NASA Astrophysics Data System (ADS)

    Philpott, Matthew P.; Hayes, Sophia C.; Thomsen, Carsten L.; Reid, Philip J.

    2001-01-01

    The geminate-recombination and vibrational-relaxation dynamics of chlorine dioxide (OClO) dissolved in ethanol and 2,2,2-trifluoroethanol (TFE) are investigated using time-resolved resonance Raman spectroscopy. Stokes spectra are measured as a function of time following photoexcitation using degenerate pump and probe wavelengths of 398 nm. For OClO dissolved in ethanol, subpicosecond geminate recombination occurs resulting in the reformation of ground-state OClO with a quantum yield of 0.5±0.1. Following recombination, intermolecular-vibrational relaxation of OClO occurs with a time constant of 31±10 ps. For OClO dissolved in TFE, recombination occurs with a time constant of 1.8±0.8 ps and a quantum yield of only 0.3±0.1. The intermolecular-vibrational-relaxation time constant of OClO in TFE is 79±27 ps. The reduced geminate-recombination quantum yield, delayed recombination, and slower vibrational relaxation for OClO in TFE is interpreted in terms of greater self-association of the solvent. Degenerate pump-probe experiments are also presented that demonstrate decay of the Cl-solvent charge-transfer complex on the ˜1-ns time scale in ethanol and TFE. This time is significantly longer than the abstraction times observed for other systems demonstrating that Cl hydrogen abstraction from alcohols occurs in the presence of a significant energy barrier.

  19. 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

  20. Resonance Raman studies of Escherichia coli sulfite reductase hemoprotein. 1. Siroheme vibrational modes.

    PubMed

    Han, S H; Madden, J F; Thompson, R G; Strauss, S H; Siegel, L M; Spiro, T G

    1989-06-27

    Resonance Raman (RR) spectra are reported for the hemoprotein subunit (SiR-HP) of Escherichia coli NADPH-sulfite reductase (EC 1.8.1.2) in various ligation and redox states. Comparison of the RR spectra of extracted siroheme and the mu-oxo FeIII dimer of octaethylisobacteriochlorin with those of mu-oxo FeIII octaethylchlorin dimer and mu-oxo FeIII octaethylporphyrin dimer demonstrates that many siroheme bands can be correlated with established porphyrin skeletal modes. Depolarization measurements are a powerful tool in this correlation, since the 45 degrees rotation of the C2 symmetry axis of the isobacteriochlorin ring relative to the chlorin system results in reversal of the polarization properties (polarized vs anomalously polarized) of bands correlating with B1g and B2g modes of porphyrin. Various SiR-HP adducts (CO, NO, CN-, SO3(2-] show upshifted high-frequency bands, characteristic of the low-spin state and consistent with the expected core size sensitivity of the skeletal modes. Fully reduced unliganded SiR-HP (both siroheme and Fe4S4 cluster reduced) in liquid solution displays RR features comparable to those of high-spin ferrous porphyrins; on freezing, the RR spectrum changes, reflecting an apparent mixture of siroheme spin states. At intermediate reduction levels in solution a RR species is observed whose high-frequency bands are upshifted relative to oxidized and fully reduced SiR-HP. This spectrum, thought to arise from the "one-electron" state of SiR-HP (siroheme reduced, cluster oxidized), may be due to S = 1 FeII siroheme.

  1. Resonance Raman spectroscopy and density functional theory study of the photodissociation dynamics of acetophenone in cyclohexane solution

    NASA Astrophysics Data System (ADS)

    Ma, Yufang; Pei, Kemei; Zheng, Xuming; Li, Haiyang

    2007-11-01

    Resonance Raman spectra were acquired for acetophenone using 228.7, 239.5, and 245.9 nm excitations in cyclohexane solution. The spectra display overtones of the benzene ring C-C stretch (1578 cm -1) and the carbonyl C dbnd O stretch (1671 cm -1) modes and their combination bands with other five vibrational modes. A preliminary resonance Raman intensity analysis was done and these results for acetophenone were compared to the those previously reported for 2-hydroxyacetophenone. The differences between the vibrational reorganizational energies for acetophenone relative to those of 2-hydroxyacetophenone were briefly discussed.

  2. Optically confined polarized resonance Raman studies in identifying crystalline orientation of sub-diffraction limited AlGaN nanostructure

    SciTech Connect

    Sivadasan, A. K. Patsha, Avinash; Dhara, Sandip

    2015-04-27

    An optical characterization tool of Raman spectroscopy with extremely weak scattering cross section tool is not popular to analyze scattered signal from a single nanostructure in the sub-diffraction regime. In this regard, plasmonic assisted characterization tools are only relevant in spectroscopic studies of nanoscale object in the sub-diffraction limit. We have reported polarized resonance Raman spectroscopic (RRS) studies with strong electron-phonon coupling to understand the crystalline orientation of a single AlGaN nanowire of diameter ∼100 nm. AlGaN nanowire is grown by chemical vapor deposition technique using the catalyst assisted vapor-liquid-solid process. The results are compared with the high resolution transmission electron microscopic analysis. As a matter of fact, optical confinement effect due to the dielectric contrast of nanowire with respect to that of surrounding media assisted with electron-phonon coupling of RRS is useful for the spectroscopic analysis in the sub-diffraction limit of 325 nm (λ/2N.A.) using an excitation wavelength (λ) of 325 nm and near ultraviolet 40× far field objective with a numerical aperture (N.A.) value of 0.50.

  3. A preservation study of carbon nanotubes in alumina-based nanocomposites via Raman spectroscopy and nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Thomson, K. E.; Jiang, Dongtao; Ritchie, R. O.; Mukherjee, A. K.

    2007-11-01

    Raman spectroscopy was used to study the preservation of the carbon nanotube structure in nanotube-reinforced alumina nanocomposites consolidated via spark plasma sintering (SPS). A series of Raman spectroscopy experiments was used to identify the thermal breakdown temperature of single-walled carbon nanotubes (SWCNTs) embedded in nanocrystalline alumina. It was found that the carbon nanotube structure remains intact after sintering at 1150 °C, but almost completely breaks down by 1350 °C after only 5 min. Also, 27Al nuclear magnetic resonance (NMR) was used to study the chemical and structural effects of high-energy ball milling (HEBM) and SPS consolidation on pure alumina and SWCNT-alumina nanocomposites. HEBM does not change the mixed coordination number of the as-received alumina, but slight peak shifts indicate residual stresses. No Al4C3 was detected in any of the consolidated samples - even up to 1550 °C for 10 min. Thus, it is concluded that consolidation of carbon nanotube-reinforced composites should be completed at temperatures below ˜1250 °C in order to preserve the carbon nanotube structure.

  4. Dermal carotenoids as measured by resonance Raman spectroscopy as a biomarker of response to a fruit/vegetable intervention study

    USDA-ARS?s Scientific Manuscript database

    Dermal carotenoid status may have utility as a biomarker for vegetable and fruit consumption. Resonance Raman spectroscopy (RRS) is a valid, non-invasive method to assess dermal carotenoids as a biomarker of usual vegetable and fruit intake, but has not been evaluated in response to a whole-diet in...

  5. 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.

  6. Resonance Raman studies of blue copper proteins: effect of temperature and isotopic substitutions. Structural and thermodynamic implications

    SciTech Connect

    Blair, D.F.; Campbell, G.W.; Schoonover, J.R.; Chan, S.I.; Gray, H.B.; Malmstrom, B.G.; Pecht, I.; Swanson, B.I.; Woodruff, W.H.; Cho, W.K.; English, A.M.

    1985-01-01

    Resonance Raman spectra of the single-copper blue proteins azurin plastocyanin and stellacyanin and the multicopper oxidases laccase ascorbate oxidase and ceruloplasmin are reported. Cryoresonance Raman observations (10-77 K) are reported for selected azurins, stellacyanin, the plastocyanins, and the laccases. Isotope studies employing /sup 63/Cu//sup 65/Cu and H/D substitution are reported for selected azurins and stellacyanin, allowing identification of modes having significant copper-ligand (Cu-L) stretch and internal ligand deformation character. Principal conclusions include the following. The only Cu-L stretching mode near 400 cm/sup -1/ is the Cu-S(Cys) stretch, and the remainder of the elementary motions near this frequency are internal ligand deformations. All the observed modes near 400 cm/sup -1/ are highly mixed, and most derive their intensity from their fractional Cu-S(Cys) stretching character. The Cu-N(His) stretching motions are best identified with the ubiquitous peak(s) near 270 cm/sup -1/, although in azurin these modes have contributions from other coordinates. Internal histidine and cysteine motions contribute to the features near 400 cm/sup -1/. This is consistent with a single resonant electronic chromophore and extremely facile vibrational dephasing or other damping processes in the electronically excited state. Temperature effects upon the spectra suggest a significant temperature-dependent structure change at the plastocyanin active site, and a more subtle one in azurin. It is shown that the Cu-S(Cys) stretching frequency is closely correlated to the electron-transfer exothermicity for several proteins, thereby indicating the reduction potential can be fine tuned by the effects of polypeptide backbone structure on the copper-sulfur bond distance and the copper-ligand field. 41 references.

  7. Resonant Raman spectroscopy of twisted multilayer graphene

    NASA Astrophysics Data System (ADS)

    Wu, Jiang-Bin; Zhang, Xin; Ijäs, Mari; Han, Wen-Peng; Qiao, Xiao-Fen; Li, Xiao-Li; Jiang, De-Sheng; Ferrari, Andrea C.; Tan, Ping-Heng

    2014-11-01

    Graphene and other two-dimensional 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 orientation have different optical and electronic properties. Probing and understanding the interface coupling is thus of primary importance for fundamental science and applications. Here we study twisted multilayer graphene flakes with multi-wavelength Raman spectroscopy. We find a significant intensity enhancement of the interlayer coupling modes (C peaks) due to resonance with new optically allowed electronic transitions, determined by the relative orientation of the layers. The interlayer coupling results in a Davydov splitting of the C peak in systems consisting of two equivalent graphene multilayers. This allows us to directly quantify the interlayer interaction, which is much smaller compared with Bernal-stacked interfaces. This paves the way to the use of Raman spectroscopy to uncover the interface coupling of two-dimensional hybrids and heterostructures.

  8. 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.

  9. UV resonance Raman spectroscopic studies of protein structure and dynamics (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Asher, Sanford A.; Punihaole, David; Dahlburg, Elizabeth M.; Jakubek, Ryan S.; Hong, Zhenmin

    2016-09-01

    UV Raman excitation into the 200 nm peptide bond electronic transitions enhance peptide bond amide vibrations of the backbone. A particular band (the amide III3) reports on the Ramachandran psi angle and peptide bond hydrogen bonding. This band is Raman scattered independently by each peptide bond with insignificant coupling between adjacent peptide bonds. Isotope editing of a peptide bond (by replacing the Calpha- H with Calpha- D) allows us to determine the frequency of individual peptide bonds within a peptide or protein to yield their psi angles. Consideration of the Boltzmann equilibria allows us to determine the psi angle Gibbs free energy landscape along the psi (un)folding coordinate that connects secondary structure conformations. The psi angle coordinate is the most important reaction coordinate necessary to understand mechanism(s) of protein folding. We have also discovered an analogous correlation for the primary amide sidechain of Gln. This allows us to monitor the hydrogen bonding and structure of this sidechain. We examine the details of peptide folding conformation dynamics with laser T-jumps where the water temperature is elevated by an 1.9 mM IR nsec laser pulse and we monitor the 200 nm UV Raman spectrum as a function of time. These spectra show the time evolution of conformation. We will discuss the role of salts on stabilizing conformations in solution

  10. Electronic resonances in broadband stimulated Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    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.

  11. 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

  12. Multiconfigurational Effects in Theoretical Resonance Raman Spectra

    PubMed Central

    Ma, Yingjin

    2017-01-01

    Abstract We analyze resonance Raman spectra of the nucleobase uracil in the short‐time approximation calculated with multiconfigurational methods. We discuss the importance of static electron correlation by means of density‐matrix renormalization group self‐consistent field (DMRG‐SCF) calculations. Our DMRG‐SCF results reveal that a minimal active orbital space that leads to a qualitatively correct description of the resonance Raman spectrum of uracil should encompass parts of the σ/σ* bonding/anti‐bonding orbitals of the pyrimidine ring. We trace these findings back to the considerable entanglement between the σ/σ* bonding/anti‐bonding as well as valence π/π* orbitals in the excited‐state electronic structure of uracil, which indicates non‐negligible non‐dynamical correlation effects that are less pronounced in the electronic ground state. PMID:27933695

  13. Proton nuclear magnetic resonance and Raman spectroscopic studies of Japanese sake, an alcoholic beverage.

    PubMed

    Nose, Akira; Myojin, Makoto; Hojo, Masashi; Ueda, Tadaharu; Okuda, Takeyuki

    2005-05-01

    The hydrogen-bonding property of water--ethanol in Japanese sake, a kind of brewage, was examined on the basis of both (1)H NMR chemical shifts of the OH of water--ethanol and the Raman OH stretching spectra. In 20% (v/v) EtOH-H(2)O solution, amino acids as well as organic acids caused low-field chemical shifts, i.e., the development of a hydrogen-bonding structure. Additional functional groups, apart from the essential amino- and carboxyl groups, in amino acids caused differences in their effects. The low-field chemical shifts caused by solutes were demonstrated under constant pH conditions maintained by sodium hydrogen citrate. Using both the measurement of (1)H NMR chemical shifts and Raman OH stretching spectra, the strength of the hydrogen bond of water--ethanol in Japanese sake products was found to be correlated with the total concentration of organic acids and amino acids. Glucose or saccharides should not have a strengthening effect on the hydrogen bond of water--ethanol. The effects of the main inorganic ions and amines were also discussed. It was concluded that chemical components originating from the starting material, rice, or products produced by microorganisms during the ethanol fermentation affect the hydrogen-bonding structure in Japanese sake.

  14. Key hydride vibrational modes in [NiFe] hydrogenase model compounds studied by resonance Raman spectroscopy and density functional calculations.

    PubMed

    Shafaat, Hannah S; Weber, Katharina; Petrenko, Taras; Neese, Frank; Lubitz, Wolfgang

    2012-11-05

    Hydrogenase proteins catalyze the reversible conversion of molecular hydrogen to protons and electrons. While many enzymatic states of the [NiFe] hydrogenase have been studied extensively, there are multiple catalytically relevant EPR-silent states that remain poorly characterized. Analysis of model compounds using new spectroscopic techniques can provide a framework for the study of these elusive states within the protein. We obtained optical absorption and resonance Raman (RR) spectra of (dppe)Ni(μ-pdt)Fe(CO)(3) and [(dppe)Ni(μ-pdt)(μ-H)Fe(CO)(3)][BF(4)], which are structural and functional model compounds for the EPR-silent Ni-SI and Ni-R states of the [NiFe] hydrogenase active site. The studies presented here use RR spectroscopy to probe vibrational modes of the active site, including metal-hydride stretching vibrations along with bridging ligand-metal and Fe-CO bending vibrations, with isotopic substitution used to identify key metal-hydride modes. The metal-hydride vibrations are essentially uncoupled and represent isolated, localized stretching modes; the iron-hydride vibration occurs at 1530 cm(-1), while the nickel-hydride vibration is observed at 945 cm(-1). The significant discrepancy between the metal-hydride vibrational frequencies reflects the slight asymmetry in the metal-hydride bond lengths. Additionally, time-dependent density functional theory (TD-DFT) calculations were carried out to obtain theoretical RR spectra of these compounds. On the basis of the detailed comparison of theory and experiment, the dominant electronic transitions and significant normal modes probed in the RR experiments were assigned; the primary transitions in the visible wavelengths represent metal-to-metal and metal-to-ligand charge transfer bands. Inherent properties of metal-hydride vibrational modes in resonance Raman spectra and DFT calculations are discussed together with the prospects of observing such vibrational modes in metal-hydride-containing proteins. Such a

  15. Graphene as a substrate to suppress fluorescence in resonance Raman spectroscopy.

    PubMed

    Xie, Liming; Ling, Xi; Fang, Yuan; Zhang, Jin; Liu, Zhongfan

    2009-07-29

    We have measured resonance Raman spectra with greatly suppressed fluorescence (FL) background from rhodamine 6G (R6G) and protoporphyrin IX (PPP) adsorbed on graphene. The FL suppression is estimated to be approximately 10(3) times for R6G. The successful observation of resonance Raman peaks demonstrates that graphene can be used as a substrate to suppress FL in resonance Raman spectroscopy (RRS), which has potential applications in low-concentration detection and RRS study of fluorescent molecules.

  16. Resonant Raman scattering from silicon nanoparticles enhanced by magnetic response

    NASA Astrophysics Data System (ADS)

    Dmitriev, Pavel A.; Baranov, Denis G.; Milichko, Valentin A.; Makarov, Sergey V.; Mukhin, Ivan S.; Samusev, Anton K.; Krasnok, Alexander E.; Belov, Pavel A.; Kivshar, Yuri S.

    2016-05-01

    Enhancement of optical response with high-index dielectric nanoparticles is attributed to the excitation of their Mie-type magnetic and electric resonances. Here we study Raman scattering from crystalline silicon nanoparticles and reveal that magnetic dipole modes have a much stronger effect on the scattering than electric modes of the same order. We demonstrate experimentally a 140-fold enhancement of the Raman signal from individual silicon spherical nanoparticles at the magnetic dipole resonance. Our results confirm the importance of the optically-induced magnetic response of subwavelength dielectric nanoparticles for enhancing light-matter interactions.Enhancement of optical response with high-index dielectric nanoparticles is attributed to the excitation of their Mie-type magnetic and electric resonances. Here we study Raman scattering from crystalline silicon nanoparticles and reveal that magnetic dipole modes have a much stronger effect on the scattering than electric modes of the same order. We demonstrate experimentally a 140-fold enhancement of the Raman signal from individual silicon spherical nanoparticles at the magnetic dipole resonance. Our results confirm the importance of the optically-induced magnetic response of subwavelength dielectric nanoparticles for enhancing light-matter interactions. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07965a

  17. Effective time-independent studies on resonance Raman spectroscopy of trans-stilbene including the Duschinsky effect

    NASA Astrophysics Data System (ADS)

    Lin, Na; Barone, Vincenzo; Cappelli, Chiara; Zhao, Xian; Ruud, Kenneth; Santoro, Fabrizio

    2013-07-01

    We simulate the resonance Raman spectra of trans-stilbene using a recently developed time-independent method that allows computations of the full two-dimensional spectrum as a function of the incident and scattered frequencies, including both the Franck-Condon and the Herzberg-Teller contributions. The potential energy surfaces (PESs) of the ground and resonant states are described in the harmonic approximation using density functional theory PBE0/6-31+G(d,p) calculations in gas phase and in cyclohexane. The simulated spectra are in good agreement with the experimental data [J. Chem. Phys. 83, 5000 (1985)] measured at four different excitation wavelengths, and allow us to unambiguously assign the main experimental bands. We perform an extensive comparison of the performance of four different vertical or adiabatic models for the PES of the resonant state, dissecting the effects of nuclear displacements and Duschinsky mixings on the spectra.

  18. Surface potential on purple membranes and its sidedness studied by a resonance Raman dye probe. [Halobacterium halobium

    SciTech Connect

    Ehrenberg, B.; Berezin, Y.

    1984-04-01

    A new technique for the measurement of membrane surface potential is proposed and demonstrated. The method is based on the fact that a positively charged styryl dye molecule aggregates when present at high concentration in the Debye layer near a membrane bearing a negative surface potential. The dye in its aggregated form exhibits marked differences in its resonance Raman spectrum relative to the free dye molecules. This method was used to study the potential on the surfaces of the purple membrane that contains the pigment bacteriorhodopsin. A value of -29.5 mV was found for membranes with bacteriorhodopsin in its relaxed, light-adapted state, and the potential decreased to -34.5 mV when most of the bacteriorhodopsin was converted to the M/sub 412/ intermediate. Because the dye probe does not diffuse through the lipid bilayer, it can be used to probe the potential on the external or internal surface of a vesicle. Thus, it was found that the potential on the purple membrane was asymmetric and was localized mainly on the surface that faces the cytoplasm in the cell.

  19. 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.

  20. Intricate Resonant Raman Response in Anisotropic ReS2.

    PubMed

    McCreary, Amber; Simpson, Jeffrey R; Wang, Yuanxi; Rhodes, Daniel; Fujisawa, Kazunori; Balicas, Luis; Dubey, Madan; Crespi, Vincent H; Terrones, Mauricio; Hight Walker, Angela R

    2017-09-12

    The strong in-plane anisotropy of rhenium disulfide (ReS2) offers an additional physical parameter that can be tuned for advanced applications such as logic circuits, thin-film polarizers, and polarization-sensitive photodetectors. ReS2 also presents advantages for optoelectronics, as it is both a direct-gap semiconductor for few-layer thicknesses (unlike MoS2 or WS2) and stable in air (unlike black phosphorus). Raman spectroscopy is one of the most powerful characterization techniques to nondestructively and sensitively probe the fundamental photophysics of a 2D material. Here, we perform a thorough study of the resonant Raman response of the 18 first-order phonons in ReS2 at various layer thicknesses and crystal orientations. Remarkably, we discover that, as opposed to a general increase in intensity of all of the Raman modes at excitonic transitions, each of the 18 modes behave differently relative to each other as a function of laser excitation, layer thickness, and orientation in a manner that highlights the importance of electron-phonon coupling in ReS2. In addition, we correct an unrecognized error in the calculation of the optical interference enhancement of the Raman signal of transition metal dichalcogenides on SiO2/Si substrates that has propagated through various reports. For ReS2, this correction is critical to properly assessing the resonant Raman behavior. We also implemented a perturbation approach to calculate frequency-dependent Raman intensities based on first-principles and demonstrate that, despite the neglect of excitonic effects, useful trends in the Raman intensities of monolayer and bulk ReS2 at different laser energies can be accurately captured. Finally, the phonon dispersion calculated from first-principles is used to address the possible origins of unexplained peaks observed in the Raman spectra, such as infrared-active modes, defects, and second-order processes.

  1. Al-doped MgB{sub 2} materials studied using electron paramagnetic resonance and Raman spectroscopy

    SciTech Connect

    Bateni, Ali; Somer, Mehmet E-mail: msomer@ku.edu.tr; Erdem, Emre E-mail: msomer@ku.edu.tr; Repp, Sergej; Weber, Stefan

    2016-05-16

    Undoped and aluminum (Al) doped magnesium diboride (MgB{sub 2}) samples were synthesized using a high-temperature solid-state synthesis method. The microscopic defect structures of Al-doped MgB{sub 2} 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 MgB{sub 2}. Above a certain level of Al doping, enhanced conductive properties of MgB{sub 2} disappear due to filling of vacancies or trapping of Al in Mg-related vacancy sites.

  2. 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.

  3. 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.

  4. The resonance Raman excitation profile of lutein

    NASA Astrophysics Data System (ADS)

    Hoskins, L. C.

    The resonance Raman excitation profiles for the ν 1, ν 2 and ν 3 vibrations of lutein in acetone, toluene and carbon disulfide solvents have been measured. The results are interpreted in terms of a three-mode vibrational theory which includes both homogeneous and inhomogeneous broadening effects. Excellent agreement between calculated and observed excitation profiles and visible spectra was found in acetone and toluene, but the results in carbon disulfide indicate a possible breakdown in the three-mode model. The major broadening mechanism is homogeneous, with about a 25% contribution from inhomogeneous broadening.

  5. Resonance Raman of BCC and normal skin

    NASA Astrophysics Data System (ADS)

    Liu, Cheng-hui; Sriramoju, Vidyasagar; Boydston-White, Susie; Wu, Binlin; Zhang, Chunyuan; Pei, Zhe; Sordillo, Laura; Beckman, Hugh; Alfano, Robert R.

    2017-02-01

    The Resonance Raman (RR) spectra of basal cell carcinoma (BCC) and normal human skin tissues were analyzed using 532nm laser excitation. RR spectral differences in vibrational fingerprints revealed skin normal and cancerous states tissues. The standard diagnosis criterion for BCC tissues are created by native RR biomarkers and its changes at peak intensity. The diagnostic algorithms for the classification of BCC and normal were generated based on SVM classifier and PCA statistical method. These statistical methods were used to analyze the RR spectral data collected from skin tissues, yielding a diagnostic sensitivity of 98.7% and specificity of 79% compared with pathological reports.

  6. 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.

  7. 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.

  8. Resonance Raman study of Bacillus subtilis NO synthase-like protein: similarities and differences with mammalian NO synthases.

    PubMed

    Santolini, Jérôme; Roman, Miruna; Stuehr, Dennis J; Mattioli, Tony A

    2006-02-07

    Bacterial NO synthase (NOS)-like proteins such as that from Bacillus subtilis (bsNOS) share a high degree of structural homology with the oxygenase domain of mammalian NOSs (mNOSs), but biochemical studies have yet failed to establish that they are specifically capable of producing NO. To better understand the actual function and role of bacterial NOSs, the structure and environment of bsNOS heme were examined with resonance Raman (RR) and ATR-FTIR spectroscopies. We analyzed the structural effects of l-arginine (Arg) and tetrahydrobiopterin (H(4)B) binding on several key complexes (ferric, ferrous, ferrous-CO, and ferric-NO) and characterized the bonding properties of the proximal cysteine ligand. While our study fully confirms the similarity between bsNOS and mNOS heme pocket structures, our results also highlight important differences. (i) Contrary to other NOSs, resting native ferric bsNOS exhibits an exclusive five-coordinate high-spin iron status. (ii) The nu(Fe)(-)(CO) and nu(CO) mode frequencies of the bsNOS Fe(II)CO complexes indicate a weaker electrostatic interaction between Arg and CO. (iii) bsNOS is characterized by a stronger Fe-S bond (nu(Fe)(-)(S) = 342 cm(-)(1)), a lower nu(4) frequency, and a negative shift in the nu(Fe)(-)(CO)/nu(CO) correlation. (iv) The effects of H(4)B on bsNOS heme structure are minor compared to the ones reported on mNOS. These results suggest distinct distal heme environments between mNOS and bsNOS, greater electron-donation properties of bsNOS cysteine proximal ligand, and the absence of a significant influence of H(4)B on bsNOS heme properties. These subtle structural differences may reflect changes in the chemistry and physiological role of bacterial NOSs.

  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. 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.

  11. Geminate recombination and vibrational relaxation dynamics of aqueous chlorine dioxide: A time-resolved resonance Raman study

    NASA Astrophysics Data System (ADS)

    Hayes, Sophia C.; Philpott, Matthew J.; Reid, Philip J.

    1998-08-01

    The photochemical dynamics of aqueous chlorine dioxide (OClO) are investigated using time-resolved resonance Raman spectroscopy. Stokes and anti-Stokes spectra are measured as a function of time following photoexcitation of OClO using degenerate pump and probe wavelengths at 390 nm. The temporal evolution of OClO Stokes intensity is found to be consistent with the reformation of ground-state OClO by subpicosecond geminate recombination of the primary ClO and O photofragments. Anti-Stokes intensity is observed for transitions corresponding to the symmetric stretch of OClO demonstrating that upon geminate recombination, excess vibrational energy is deposited along this coordinate. Dissipation of this energy to the surrounding solvent occurs with a time constant of ˜9 ps. Finally, a delay in the appearance of OClO anti-Stokes intensity relative to geminate recombination is observed demonstrating that the excess vibrational energy available to OClO is initially deposited along the resonance Raman inactive asymmetric stretch coordinate with the exchange of energy between this coordinate and the symmetric stretch occurring with a time-constant of ˜5 ps.

  12. 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.

  13. 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.

  14. Ultraviolet Resonance Raman Enhancements in the Detection of Explosives

    DTIC Science & Technology

    2009-06-01

    SUBJECT TERMS Raman Spectroscopy, Standoff Detection, High Explosives, Explosive Detection, Inelastic Scattering, Resonance Raman 16. PRICE CODE...absolute Raman cross sections of TATP, PETN, RDX and TNT explosives from 620 to 248 nm at a constant flux of 2.5 1024 quanta s1 cm2 using KNO3

  15. 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.

  16. Resonance Raman and photophysical studies of transition metal complexes in solution and entrapped in zeolites

    SciTech Connect

    Kincaid, J.R.

    1992-03-31

    We have obtained convincing evidence for localization of the optical electron on a single-ring fragment of a chelated bipyridine-like'' ligand (ie., pyridylpyrazine or 4-Methyl-bipyridine). In addition we have completed studies of Ru(bipyrazine){sub 3}{sup 2+} in aqueous sulfuric acid (0--98% by weight) and find clear evidence for sequential addition of six-protons to the six peripheral nitrogen atoms. Studies of zeolite-entrapped complexes are continuing and a series of homo- and heteroleptic complexes have been prepared and characterized. Finally, the synthesis of zeolite-entrapped metallophthalocyanines has now been developed and the copper and cobalt analogues synthesized. The characterization of these materials is now in progress.

  17. 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).

  18. Light-induced change of configuration of the LHCII-bound xanthophyll (tentatively assigned to violaxanthin): a resonance Raman study.

    PubMed

    Gruszecki, Wiesław I; Gospodarek, Małgorzata; Grudziński, Wojciech; Mazur, Radosław; Gieczewska, Katarzyna; Garstka, Maciej

    2009-02-26

    Raman scattering spectra of light-harvesting complex LHCII isolated from spinach were recorded with an argon laser, tuned to excite the most red-absorbing LHCII-bound xanthophylls (514.5 nm). The intensity of the nu(4) band (at ca. 950 cm-1) corresponding to the out-of-plane wagging modes of the C-H groups in the resonance Raman spectra of carotenoids appears to be inversely dependent on the probing laser power density. This observation can be interpreted in terms of excitation-induced change of configuration of the protein-bound xanthophyll owing to the fact that the intensity of this particular band is diagnostic of a chromophore twisting resulting from its binding to the protein environment. The comparison of the shape of the nu(4) band of a xanthophyll involved in the light-induced spectral changes with the shape of the nu(4) band of the xanthophylls present in LHCII, reported in the literature, lets us conclude that, most probably, violaxanthin is a pigment that undergoes light-driven changes of molecular configuration but also the involvement of lutein may not be excluded. Possible physical mechanisms responsible for the configuration changes and physiological importance of the effect observed are discussed.

  19. Ligation and quaternary structure induced changes in the heme pocket of hemoglobin: a transient resonance Raman study.

    PubMed

    Friedman, J M; Stepnoski, R A; Stavola, M; Ondrias, M R; Cone, R L

    1982-04-27

    The extent to which ligation and quaternary structure modify the heme-heme pocket configuration is determined by generating and analyzing transient resonance Raman spectra from various photolyzed and partially photolyzed hemoglobins (Hb). From small frequently shifts in Raman band I (approximately 1355 cm-1) it is determined that ligation induces a configurational change about the heme. The extent to which ligation modifies the heme pocket is influenced by the quaternary structure. With respect to the structural parameter responsible for variations in the pi orbital electron density of the porphyrin, the degree of alteration of the heme pocket configuration relative to deoxy-Hb(T) follows the sequence: liganded Hb(R) greater than liganded Hb(R) + IHP greater than liganded Hb(T) [alpha chain greater than beta chain] greater than deoxy-Hb(R). This progression of configurations also forms a sequence with respect to the "retentiveness" of the heme pocket as reflected in the ligand dynamics associated with geminate recombination. The results indicate that the heme-heme pocket of the R-state Hb's, relative to those of the T-state species, favors ligand retention in a dynamic, as well as thermodynamic, sense. The analysis of these and other related data implicates a ligation and quaternary structure modulated electronic and/or electrostatic interaction between the pi system of the porphyrin and the surrounding heme pocket as the basis for this variation in ligand dynamics as well as for the energetics of cooperativity.

  20. 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.

  1. 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.

  2. 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

  3. Observation of the Auger resonant Raman effect

    SciTech Connect

    Brown, G.S.; Chen, M.H.; Crasemann, B.; Ice, G.E.

    1980-11-01

    Monochromatized synchrotron radiation near the photoionization threshold was used to produce the (2p/sub 3/2/) vacancy state in atomic Xe. Deexcitation of the state through L/sub 3/-M/sub 4/M/sub 5/(/sup 1/G/sub 4/) Auger-electron emission was measured. The 5d spectator-electron Auger satellite was observed. The satellite energy exhibits linear dispersion. The observed width of the /sup 1/G diagram line decreases by approx. 40% when the exciting photon energy reaches the vicinity of the Xe L/sub 3/ binding energy. This radiationless process can thus be construed as the Auger analog of the x-ray resonant Raman effect. The /sup 1/G diagram line is shifted by -+3 eV due to post-collision interaction; this shift varies with excitation energy.

  4. Resonance Raman excitation profiles of lycopene

    NASA Astrophysics Data System (ADS)

    Hoskins, L. C.

    1981-01-01

    The resonance Raman spectrum of lycopene has been examined in acetone solvent and excitation profiles of the three fundamentals ν1, ν2, and ν3 have been determined. The excitation data and the visible spectrum have been analyzed using two-mode and three-mode vibrational models, with the two-mode model involving virtual states of ν1 and ν2 giving the best fit to the data. This mode mixing or Duskinsky effect was not observed for β-carotene. The single-mode and three-mode theories which have been used to explain the corresponding data for β-carotene are shown to be inconsistent with the experimental data of lycopene. Equations for calculating excitation profiles and visible spectra are given.

  5. Resonant Raman scattering study of BexZn1-xO thin films grown on sapphire by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Wang, Yu-Chao; Su, Long-Xing; Zhao, Yu; Liu, Jian-Feng; Shen, Zheng-Chuan; Feng, Yu-Hua; Wu, Tian-Zhun; Tang, Zi-Kang

    2017-07-01

    Resonance Raman spectra of BexZn1-xO alloy materials were studied using 325 nm Laser. The research showed that the Raman spectra of BexZn1-xO alloys presents a dual-mode vibration. Compare BexZn1-xO alloy with ZnO single crystal, the A1 (LO) phonon vibration mode of BexZn1-xO alloy moved to the larger wave number direction. The position of A1 (LO) phonon vibration modes of Be0.08Zn0.92O and Be0.12Zn0.88O was 580 cm-1 and 582 cm-1, respectively. In addition, the temperature-dependent Raman spectroscopy was employed for Be0.12Zn0.88O, and the phonon mode frequency shift with temperature was studied in detail. Finally, the stability of the polar and nonpolar BexZn1-xO alloy materials was studied using resonance Raman spectroscopy. The results showed that the A1 (LO) phonon mode frequency of polar BexZn1-xO alloy remained in the same position, while the nonpolar BexZn1-xO alloys moved nearly 3.5 cm-1 to larger direction after being placed in the air for two years. The reason may be that the stability of the nonpolar BexZn1-xO alloy is relatively poor upon interaction with molecule such as H2O, O2 in the air.

  6. Resonant Raman studies of compositional and size dispersion of CdS1-xSex nanocrystals in a glass matrix

    NASA Astrophysics Data System (ADS)

    Azhniuk, Yu M.; Milekhin, A. G.; Gomonnai, A. V.; Lopushansky, V. V.; Yukhymchuk, V. O.; Schulze, S.; Zenkevich, E. I.; Zahn, D. R. T.

    2004-12-01

    Resonant Raman scattering spectra of glass-embedded CdS1-xSex nanocrystals are measured and complemented with TEM and optical absorption as well as photoluminescence data. The selectivity of the resonant Raman process not only for the size, but also for the composition of nanocrystals within the ensemble, is directly observed in the dependence of phonon band frequency, linewidth and shape on the excitation wavelength.

  7. Ultrasensitive fiber enhanced UV resonance Raman sensing of drugs.

    PubMed

    Frosch, Torsten; Yan, Di; Popp, Jürgen

    2013-07-02

    Fiber enhanced UV resonance Raman spectroscopy is introduced for chemical selective and ultrasensitive analysis of drugs in aqueous media. The application of hollow-core optical fibers provides a miniaturized sample container for analyte flow and efficient light-guiding, thus leading to strong light-analyte interactions and highly improved analytical sensitivity with the lowest sample demand. The Raman signals of the important antimalaria drugs chloroquine and mefloquine were strongly enhanced utilizing deep UV and electronic resonant excitation augmented by fiber enhancement. An experimental design was developed and realized for reproducible and quantitative Raman fiber sensing, thus the enhanced Raman signals of the pharmaceuticals show excellent linear relationship with sample concentration. A thorough model accounts for the different effects on signal performance in resonance Raman fiber sensing, and conclusions are drawn how to improve fiber enhanced Raman spectroscopy (FERS) for chemical selective analysis with picomolar sensitivity.

  8. Coherent control through near-resonant Raman transitions

    SciTech Connect

    Dai Xingcan; Lerch, Eliza-Beth W.; Leone, Stephen R.

    2006-02-15

    The phase of an electronic wave function is shown to play an important role in coherent control experiments. By using a pulse shaping system with a femtosecond laser, we explore the phase relationships among resonant and off-resonant Raman transitions in Li{sub 2} by measuring the phases of the resulting wave packets, or quantum beats. Specific pixels in a liquid-crystal spatial light modulator are used to isolate the resonant and off-resonant portions of the Raman transitions in Li{sub 2}. The off-resonant Raman transitions have an approximately 90 degree sign phase shift with respect to the resonant Raman transition, and there is an approximately 180 degree sign phase shift between the blue-detuned and the red-detuned off-resonant Raman transitions. Calculations using second-order time-dependent perturbation theory for the electronic transitions agree with the experimental results for the laser pulse intensities used here. Interferences between the off-resonant Raman transitions as a function of detuning are used to demonstrate coherent control of the Raman quantum wave packet.

  9. Interactions of water-soluble porphyrins with hexadeoxyribonucleotides: resonance raman, UV-visible and 1H NMR studies.

    PubMed

    Bütje, K; Schneider, J H; Kim, J J; Wang, Y; Ikuta, S; Nakamoto, K

    1989-10-01

    The interactions of the water-soluble porphyrins M(TMpy-P4) [M = H2, Cu(II), Ni(II), and Co(III); TMpy-P4 = tetrakis(4-N-methylpyridyl)porphyrinato ion], with the hexadeoxyribonucleotides d(CGTACG)2, d(TACGTA)2, d(GCATGC)2, d(TGTGCA)2, and d(CTATAG)2 have been investigated by resonance Raman and/or UV-visible spectroscopy. The results indicate that all hexamers containing the 5'CG3' as well as the 5'GC3' site, and also the mismatched hexamer d(TGTGCA)2, are capable of intercalating the H2, Cu(II) and Ni(II) porphyrins. 1H nuclear magnetic resonance spectra of d(CGTACG)2 mixed with Cu(TMpy-P4) have provided further evidence for the intercalation. For the other cases, outside binding by localized electrostatic interaction is suggested. There is no evidence of groove binding to any of the hexamers. Possible reasons for different binding properties of long and short helices are discussed.

  10. 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

  11. 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

  12. 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. © 2011 Society for Applied Spectroscopy

  13. 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.

  14. Resonant Femtosecond Stimulated Raman Spectra: Theory and Simulations.

    PubMed

    Rao, B Jayachander; Gelin, Maxim F; Domcke, Wolfgang

    2016-05-19

    We present a description of resonant femtosecond stimulated Raman spectra, which is based on the solution of the nonperturbative equation of motion of the chromophore in the laser fields. The theory is applicable for arbitrary shapes and durations of the Raman pulses, accounts for excited-state absorption, and describes nonstationary preparation of the system by an actinic pulse. The method is illustrated by the calculation of femtosecond stimulated Raman spectra of a model system with a conical intersection.

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

    NASA Technical Reports Server (NTRS)

    Lawandy, Nabil M.

    1987-01-01

    The third phase of research will focus on the propagation and energy extraction of the pump and SERS beams in a variety of configurations including oscillator structures. In order to address these questions a numerical code capable of allowing for saturation and full transverse beam evolution is required. The method proposed is based on a discretized propagation energy extraction model which uses a Kirchoff integral propagator coupled to the three level Raman model already developed. The model will have the resolution required by diffraction limits and will use the previous density matrix results in the adiabatic following limit. Owing to its large computational requirements, such a code must be implemented on a vector array processor. One code on the Cyber is being tested by using previously understood two-level laser models as guidelines for interpreting the results. Two tests were implemented: the evolution of modes in a passive resonator and the evolution of a stable state of the adiabatically eliminated laser equations. These results show mode shapes and diffraction losses for the first case and relaxation oscillations for the second one. Finally, in order to clarify the computing methodology used to exploit the speed of the Cyber's computational speed, the time it takes to perform both of the computations previously mentioned to run on the Cyber and VAX 730 must be measured. Also included is a short description of the current laser model (CAVITY.FOR) and a flow chart of the test computations.

  16. 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.

  17. Transform analysis of the resonance Raman excitation profile of lycopene

    NASA Astrophysics Data System (ADS)

    Hoskins, L. C.

    1992-10-01

    The resonance Raman excitation profiles (RREPs) of the ν 1, ν 2 and ν 3 vibrations of lycopene in acetone, ethyl alcohol, toluene and carbon disulphide solvents have been analyzed using the transform method for calculating resonance Raman excitation profiles. The tests show excellent agreement between the calculated and observed profiles for the ν 2 and ν 3 RREPs, but greater difference between experiment and theory occurs for the ν 1 RREP, especially in carbon disulphide solvent.

  18. 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.

  19. Visualization of Vibrational Modes in Real Space by Tip-Enhanced Non-Resonant Raman Spectroscopy.

    PubMed

    Duan, Sai; Tian, Guangjun; Luo, Yi

    2016-01-18

    We present a general theory to model the spatially resolved non-resonant Raman images of molecules. It is predicted that the vibrational motions of different Raman modes can be fully visualized in real space by tip-enhanced non-resonant Raman scattering. As an example, the non-resonant Raman images of water clusters were simulated by combining the new theory and first-principles calculations. Each individual normal mode gives rise its own distinct Raman image, which resembles the expected vibrational motions of the atoms very well. The characteristics of intermolecular vibrations in supermolecules could also be identified. The effects of the spatial distribution of the plasmon as well as nonlinear scattering processes were also addressed. Our study not only suggests a feasible approach to spatially visualize vibrational modes, but also provides new insights in the field of nonlinear plasmonic spectroscopy.

  20. Theoretical studies of Resonance Enhanced Stimulated Raman Scattering (RESRS) of frequency-doubled Alexandrite laser wavelength in cesium vapor

    NASA Technical Reports Server (NTRS)

    Lawandy, Nabil M.

    1987-01-01

    The solutions for the imaginary susceptibility of the Raman field transition with arbitrary relaxation rates and field strengths are examined for three different sets of relaxation rates. These rates correspond to: (1) Far Infrared (FIR) Raman lasers in the diabatic collision regime without consideration of coupled population decay in a closed system, (2) Raman FIR lasers in the diabatic collision regime with coupled population conserving decay, and (3) IR Raman gain in cesium vapor. 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.

  1. Structural dynamics of phenylisothiocyanate in the light-absorbing excited states: resonance Raman and complete active space self-consistent field calculation study.

    PubMed

    Ouyang, Bing; Xue, Jia-Dan; Zheng, Xuming; Fang, Wei-Hai

    2014-05-21

    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 S(2,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.

  2. 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.

  3. Insights into Protein Structure and Dynamics by Ultraviolet and Visible Resonance Raman Spectroscopy.

    PubMed

    López-Peña, Ignacio; Leigh, Brian S; Schlamadinger, Diana E; Kim, Judy E

    2015-08-11

    Raman spectroscopy is a form of vibrational spectroscopy based on inelastic scattering of light. In resonance Raman spectroscopy, the wavelength of the incident light falls within an absorption band of a chromophore, and this overlap of excitation and absorption energy greatly enhances the Raman scattering efficiency of the absorbing species. The ability to probe vibrational spectra of select chromophores within a complex mixture of molecules makes resonance Raman spectroscopy an excellent tool for studies of biomolecules. In this Current Topic, we discuss the type of molecular insights obtained from steady-state and time-resolved resonance Raman studies of a prototypical photoactive protein, rhodopsin. We also review recent efforts in ultraviolet resonance Raman investigations of soluble and membrane-associated biomolecules, including integral membrane proteins and antimicrobial peptides. These examples illustrate that resonance Raman is a sensitive, selective, and practical method for studying the structures of biological molecules, and the molecular bonding, geometry, and environments of protein cofactors, the backbone, and side chains.

  4. 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.

  5. 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.

  6. 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.

  7. Resonance Raman and photophysical studies of transition metal complexes in solution and entrapped in zeolites. Progress report, August 1, 1990--January 1993

    SciTech Connect

    Kincaid, J.R.

    1993-09-01

    Area of most intense activity involves study of effects of entrapment of ruthenium(II)-polypyridyl complexes within the supercages of Y-zeolite. Results of initial studies document alterations in photophysical properties of entrapped complexes and provide insight into the factors responsible for these changes. A second major activity was to undertake an investigation of the feasibility of entrapment of metallophthalocyanines within the Y-zeolite supercages. Initial problems in preparative methodology used for these systems have been overcome and several systems have now been prepared and purified for projected photoredox studies. A third major objective was to develop and utilize a sound interpretive framework for resonance Raman (RR) and time-resolved RR (TR{sup 3}) methods for investigating subtle perturbations in ground- and {sup 3}MLCT-state electronic structure which might be induced by substituent or environmentally-induced asymmetry, effects which could possibly lead to critical functional alterations.

  8. Fourier Transform Infrared (FTIR) Spectroscopy, Ultraviolet Resonance Raman (UVRR) Spectroscopy, and Atomic Force Microscopy (AFM) for Study of the Kinetics of Formation and Structural Characterization of Tau Fibrils.

    PubMed

    Ramachandran, Gayathri

    2017-01-01

    Kinetic studies of tau fibril formation in vitro most commonly employ spectroscopic probes such as thioflavinT fluorescence and laser light scattering or negative stain transmission electron microscopy. Here, I describe the use of Fourier transform infrared (FTIR) spectroscopy, ultraviolet resonance Raman (UVRR) spectroscopy, and atomic force microscopy (AFM) as complementary probes for studies of tau aggregation. The sensitivity of vibrational spectroscopic techniques (FTIR and UVRR) to secondary structure content allows for measurement of conformational changes that occur when the intrinsically disordered protein tau transforms into cross-β-core containing fibrils. AFM imaging serves as a gentle probe of structures populated over the time course of tau fibrillization. Together, these assays help further elucidate the structural and mechanistic complexity inherent in tau fibril formation.

  9. Circular dichroism and UV resonance raman study of the impact of alcohols on the Gibbs free energy landscape of an alpha-helical peptide.

    PubMed

    Xiong, Kan; Asher, Sanford A

    2010-04-20

    We used CD and UV resonance Raman spectroscopy to study the impact of alcohols on the conformational equilibria and relative Gibbs free energy landscapes along the Ramachandran Psi-coordinate of a mainly poly-Ala peptide, AP with an AAAAA(AAARA)(3)A sequence. 2,2,2-Trifluoroethanol (TFE) most stabilizes the alpha-helix-like conformations, followed by ethanol, methanol, and pure water. The pi-bulge conformation is stabilized more than the alpha-helix, while the 3(10)-helix is destabilized due to the alcohol-increased hydrophobicity. Turns are also stabilized by alcohols. We also found that while TFE induces more alpha-helices, it favors multiple, shorter helix segments.

  10. Circular dichroism and UV resonance Raman study of the impact of alcohols on the Gibbs free energy landscape of an α-helical peptide†

    PubMed Central

    Xiong, Kan; Asher, Sanford A

    2010-01-01

    We used CD and UV resonance Raman spectroscopy to study the impact of alcohols on the conformational equilibria and relative Gibbs free energy landscapes along the Ramanchandran Ψ-coordinate of a mainly poly-ala peptide, AP of sequence AAAAA(AAARA)3A. 2,2,2-trifluroethanol (TFE) most stabilizes the α-helical-like conformations, followed by ethanol, methanol and pure water. The π-bulge conformation is stabilized more than the α-helix, while the 310-helix is destabilized due to the alcohol increased hydrophobicity. Turns are also stabilized by alcohols. We also found that while TFE induces more α-helices, it favors multiple, shorter helix segments. PMID:20225890

  11. Structure and reactivity of thiazolium azo dyes: UV-visible, resonance Raman, NMR, and computational studies of the reaction mechanism in alkaline solution.

    PubMed

    Abbott, Laurence C; Batchelor, Stephen N; Moore, John N

    2013-03-07

    UV-visible absorption, resonance Raman, and (1)H NMR spectroscopy, allied with density functional theory (DFT) calculations, have been used to study the structure, bonding, and alkaline hydrolysis mechanism of the cationic thiazloium azo dye, 2-[2-[4-(diethylamino)phenyl]diazenyl]-3-methyl-thiazolium (1a), along with a series of six related dyes with different 4-dialkylamino groups and/or other phenyl ring substituents (2a-c, 3a-c) and the related isothiazolium azo dye, 5-[2-[4-(dimethylamino)phenyl]diazenyl]-2-methyl-isothiazolium (4). These diazahemicyanine dyes are calculated to have a similar low-energy structure that is cis, trans at the (iso)thiazolium-azo group, and for which the calculated Raman spectra provide a good match with the experimental data; the calculations on these structures are used to assign and discuss the transitions giving rise to the experimental spectra, and to consider the bonding and its variation between the dyes. UV-visible, Raman, and NMR spectra recorded from minutes to several weeks after raising the pH of an aqueous solution of 1a to ca. 11.5 show that the dominant initial step in the reaction is loss of diethylamine to produce a quinonimine (ca. hours), with subsequent reactions occurring on longer time scales (ca. days to weeks); kinetic analyses give a rate constant of 2.6 × 10(-2) dm(3) mol(-1) s(-1) for reaction of 1a with OH(-). UV-visible spectra recorded on raising the pH of the other dyes in solution show similar changes that are attributed to the same general reaction mechanism, but with different rate constants for which the dependence on structure is discussed.

  12. Resonance-Enhanced Excited-State Raman Spectroscopy of Conjugated Thiophene Derivatives: Combining Experiment with Theory

    NASA Astrophysics Data System (ADS)

    Barclay, Matthew S.; Quincy, Timothy J.; Caricato, Marco; Elles, Christopher G.

    2017-06-01

    Resonance-enhanced Femtosecond Stimulated Raman Spectroscopy (FSRS) is an ultrafast experimental method that allows for the study of excited-state structural behaviors, as well as the characterization of higher electronically excited states accessible through the resonant conditions of the observed vibrations. However, interpretation of the experiment is difficult without an accurate vibrational assignment of the resonance-enhanced spectra. We therefore utilize simulations of off-resonant excited-state Raman spectra, in which we employ a numerical derivative of the analytical excited-state polarizabilities along the normal mode displacements, in order to identify and interpret the resonance-enhanced vibrations observed in experiment. We present results for a benchmark series of conjugated organic thiophene derivatives, wherein we have computed the off-resonant excited-state Raman spectra for each molecule and matched it with its resonance-enhanced experimental spectrum. This comparison allows us to successfully identify the vibrational displacements of the observed FSRS bands, as well as validate the accuracy of the theoretical results through an experimental benchmark. The agreement between the experimental and computed results demonstrates that we are able to predict qualitatively accurate excited-state Raman spectra for these conjugated thiophenes, allowing for a more thorough interpretation of excited-state Raman signals at relatively low computational cost.

  13. Protonation of carbon single-walled nanotubes studied using 13C and 1H-13C cross polarization nuclear magnetic resonance and Raman spectroscopies.

    PubMed

    Engtrakul, Chaiwat; Davis, Mark F; Gennett, Thomas; Dillon, Anne C; Jones, Kim M; Heben, Michael J

    2005-12-14

    The reversible protonation of carbon single-walled nanotubes (SWNTs) in sulfuric acid and Nafion was investigated using solid-state nuclear magnetic resonance (NMR) and Raman spectroscopies. Magic-angle spinning (MAS) was used to obtain high-resolution 13C and 1H-13C cross polarization (CP) NMR spectra. The 13C NMR chemical shifts are reported for bulk SWNTs, H2SO4-treated SWNTs, SWNT-Nafion polymer composites, SWNT-AQ55 polymer composites, and SWNTs in contact with water. Protonation occurs without irreversible oxidation of the nanotube substrate via a charge-transfer process. This is the first report of a chemically induced change in a SWNT 13C resonance brought about by a reversible interaction with an acidic proton, providing additional evidence that carbon nanotubes behave as weak bases. Cross polarization was found to be a powerful technique for providing an additional contrast mechanism for studying nanotubes in contact with other chemical species. The CP studies confirmed polarization transfer from nearby protons to nanotube carbon atoms. The CP technique was also applied to investigate water adsorbed on carbon nanotube surfaces. Finally, the degree of bundling of the SWNTs in Nafion films was probed with the 1H-13C CP-MAS technique.

  14. Resonance Raman detection of carotenoid antioxidants in living human tissue

    PubMed Central

    Ermakov, Igor V.; Sharifzadeh, M.; Ermakova, Maia; Gellermann, W.

    2011-01-01

    Increasing evidence points to the beneficial effects of carotenoid antioxidants in the human body. Several studies, for example, support the protective role of lutein and zeaxanthin in the prevention of age-related eye diseases. If present in high concentrations in the macular region of the retina, lutein and zeaxanthin provide pigmentation in this most light sensitive retinal spot, and as a result of light filtering and/or antioxidant action, delay the onset of macular degeneration with increasing age. Other carotenoids, such as lycopene and beta-carotene, play an important role as well in the protection of skin from UV and short-wavelength visible radiation. Lutein and lycopene may also have protective function for cardiovascular health, and lycopene may play a role in the prevention of prostate cancer. Motivated by the growing importance of carotenoids in health and disease, and recognizing the lack of any accepted noninvasive technology for the detection of carotenoids in living human tissue, we explore resonance Raman spectroscopy as a novel approach for noninvasive, laser optical carotenoid detection. We review the main results achieved recently with the Raman detection approach. Initially we applied the method to the detection of macular carotenoid pigments, and more recently to the detection of carotenoids in human skin and mucosal tissues. Using skin carotenoid Raman instruments, we measure the carotenoid response from the stratum corneum layer of the palm of the hand for a population of 1375 subjects and develope a portable skin Raman scanner for field studies. These experiments reveal that carotenoids are a good indicator of antioxidant status. They show that people with high oxidative stress, like smokers, and subjects with high sunlight exposure, in general, have reduced skin carotenoid levels, independent of their dietary carotenoid consumption. We find the Raman technique to be precise, specific, sensitive, and well suitable for clinical as well as

  15. Resonance Raman detection of carotenoid antioxidants in living human tissue.

    PubMed

    Ermakov, Igor V; Sharifzadeh, M; Ermakova, Maia; Gellermann, W

    2005-01-01

    Increasing evidence points to the beneficial effects of carotenoid antioxidants in the human body. Several studies, for example, support the protective role of lutein and zeaxanthin in the prevention of age-related eye diseases. If present in high concentrations in the macular region of the retina, lutein and zeaxanthin provide pigmentation in this most light sensitive retinal spot, and as a result of light filtering and/or antioxidant action, delay the onset of macular degeneration with increasing age. Other carotenoids, such as lycopene and beta-carotene, play an important role as well in the protection of skin from UV and short-wavelength visible radiation. Lutein and lycopene may also have protective function for cardiovascular health, and lycopene may play a role in the prevention of prostate cancer. Motivated by the growing importance of carotenoids in health and disease, and recognizing the lack of any accepted noninvasive technology for the detection of carotenoids in living human tissue, we explore resonance Raman spectroscopy as a novel approach for noninvasive, laser optical carotenoid detection. We review the main results achieved recently with the Raman detection approach. Initially we applied the method to the detection of macular carotenoid pigments, and more recently to the detection of carotenoids in human skin and mucosal tissues. Using skin carotenoid Raman instruments, we measure the carotenoid response from the stratum corneum layer of the palm of the hand for a population of 1375 subjects and develop a portable skin Raman scanner for field studies. These experiments reveal that carotenoids are a good indicator of antioxidant status. They show that people with high oxidative stress, like smokers, and subjects with high sunlight exposure, in general, have reduced skin carotenoid levels, independent of their dietary carotenoid consumption. We find the Raman technique to be precise, specific, sensitive, and well suitable for clinical as well as

  16. 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.

  17. 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.

  18. Temperature dependence of resonance Raman spectra of carotenoids

    NASA Astrophysics Data System (ADS)

    Andreeva, A.; Apostolova, I.; Velitchkova, M.

    2011-04-01

    To understand the mechanism of the photoprotective and antioxidative functions of carotenoids, it is essential to have a profound knowledge of their excited electronic and vibronic states. In the present study we investigate the most powerful antioxidants: β-carotene and lutein by means of resonance Raman spectroscopy. The aim was to study in detail their Raman spectra in solution at room temperature and their changes as a function of temperature. To measure the spectra in their natural environment pyridine has been used as a solvent. It has been chosen because of its polarizability ( n = 1.5092) which is close to that of membrane lipids and proteins. The temperature dependence of the most intensive ν1 band in the range from 77 K to 295 K at 514.5 nm excitation has been obtained. It was found that in pyridine the C dbnd C stretching frequency, its intensity, line shape, and line width are very sensitive to the temperature (the sensitivity being different for the two studied carotenoids). The observed linear temperature dependence of the C dbnd C stretching frequency is explained by a mechanism involving changes of the vibronic coupling and the extent of π-electron delocalization. The different behavior of the temperature-induced broadening of the ν1 band and its intensity for the two studied carotenoids can be associated with the different nature of their solid matrices: glassy for β-carotene and crystalline-like for lutein, owing to their different chemical structures.

  19. 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.

  20. 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.

  1. UV resonance Raman analysis of trishomocubane and diamondoid dimers

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    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 B2g 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 sp2-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.

  2. 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.

  3. UV resonance Raman analysis of trishomocubane and diamondoid dimers.

    PubMed

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

    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 B2g 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(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.

  4. Citrate-reduced silver hydrosol modified with omega-mercaptoalkanoic acids self-assembled monolayers as a substrate for surface-enhanced resonance Raman scattering. A study with cytochrome c.

    PubMed

    Bonifacio, Alois; van der Sneppen, Lineke; Gooijer, Cees; van der Zwan, Gert

    2004-07-06

    A new citrate-reduced silver hydrosol coated with omega-mercaptoalkanoic acids (mercaptopropionic and mercaptoundecanoic acids) self-assembled monolayers was prepared and characterized with surface-enhanced Raman spectroscopy. The structure and the quality of the coating monolayers are discussed and compared to similar coated and uncoated silver hydrosols previously developed. As an application, the new hydrosol was used as a biocompatible and efficient metal substrate for a surface-enhanced resonance Raman scattering (SERRS) study of cytochrome c. The high-quality SERRS spectra reported of cytochrome c (obtained using only 1 microL of a micromolar cytochrome solution) are discussed and compared with data available from literature studies.

  5. A tunable single-monochromator Raman system based on the supercontinuum laser and tunable filters for resonant Raman profile measurements

    NASA Astrophysics Data System (ADS)

    Liu, X.-L.; Liu, H.-N.; Tan, P.-H.

    2017-08-01

    Resonant Raman spectroscopy requires that the wavelength of the laser used is close to that of an electronic transition. A tunable laser source and a triple spectrometer are usually necessary for resonant Raman profile measurements. However, such a system is complex with low signal throughput, which limits its wide application by scientific community. Here, a tunable micro-Raman spectroscopy system based on the supercontinuum laser, transmission grating, tunable filters, and single-stage spectrometer is introduced to measure the resonant Raman profile. The supercontinuum laser in combination with transmission grating makes a tunable excitation source with a bandwidth of sub-nanometer. Such a system exhibits continuous excitation tunability and high signal throughput. Its good performance and flexible tunability are verified by resonant Raman profile measurement of twisted bilayer graphene, which demonstrates its potential application prospect for resonant Raman spectroscopy.

  6. Graphene Moiré patterns observed by umklapp double-resonance Raman scattering

    NASA Astrophysics Data System (ADS)

    Righi, A.; Costa, S. D.; Chacham, H.; Fantini, C.; Venezuela, P.; Magnuson, C.; Colombo, L.; Bacsa, W. S.; Ruoff, R. S.; Pimenta, M. A.

    2011-12-01

    This work reports a Raman study of graphene bilayer samples grown by chemical vapor deposition on a copper foil, using laser lines in the UV range. The Raman spectra show a number of extra peaks, classified in different families, which appear nonuniformly across the Cu surface, in regions with sizes of several μm. We interpret these new extra modes as due to Moiré patterns of twisted layers of graphene, each family of peaks being associated with different twist rotational angles. We theoretically analyze the results, introducing the concept of umklapp double-resonance Raman processes associated with reciprocal lattice vectors of the Moiré pattern supercells.

  7. Ultraviolet resonant Raman spectroscopy of nucleic acid components.

    PubMed

    Blazej, D C; Peticolas, W L

    1977-07-01

    The first resonant Raman excitation profile using UV as well as visible radiation is presented. Measurements of the intensity of the Raman spectrum of adenosine 5'-monophosphate as a function of the frequency of the incident laser light are presented in the range from 20 to 38 kK (1000 cm-1). The scattering intensity per molecule increases by about 10(5) as the laser is tuned from low to high frequencies. The Raman excitation profile has been calculated by using a simple form of the vibronic theory of Raman scattering. The theoretical curves are found to adequately fit the data using only the frequencies of the excited electronic states of AMP and their corresponding vibronic linewidths as adjustable parameters. The Raman bands at 1484 cm-1 and 1583 cm-1 appear to obtain virtually all of their intensity from a weak electronic transition at 276 nm. The set of Raman bands in the range 1300 cm-1-1400 cm-1 appear to derive at least part of their intensity from an electronic band whose 0-0 transition is in the 269-259 nm region although the possibility of some intensity arising from the vibronic mixing between these two electronic states cannot as yet be ruled out.

  8. Ultraviolet Resonance Raman spectroscopy used to study formulations of salmon calcitonin, a starch-peptide conjugate and TGF-β3.

    PubMed

    Patois, E; Larmour, I A; Bell, S E J; Palais, C; Capelle, M A H; Gurny, R; Arvinte, T

    2012-06-01

    Ultraviolet Resonance Raman (UVRR) spectroscopy with excitation at 244 nm was investigated here as a possible useful tool for fast characterization of biopharmaceuticals. Studies were performed on three protein drugs: salmon calcitonin (sCT), starch-peptide conjugate, and transforming growth factor-β3 (TGF-β3) adsorbed onto solid granules of tricalcium phosphate (TCP). Secondary structure of sCT was investigated for solutions of 0.5mg/mL up to 200mg/mL, regardless of the turbidity or aggregation states. An increase in β-sheet content was detected when sCT solutions aggregated. UVRR spectroscopy also detected a small amount of residual organic solvent in a starch-peptide conjugate solution containing only 40 μg/mL of peptide. UVRR spectroscopy was then used to characterize a protein, TGF-β3, adsorbed onto solid granules of TCP at 50 and 250 μg/cm(3). This study shows that UVRR is suitable to characterize the protein formulations in a broad range of concentrations, in liquid, aggregated, and solid states.

  9. Pre-Resonance Raman Spectroscopy-Based Explosives Detector

    NASA Astrophysics Data System (ADS)

    Gupta, S.; Kumar, A.; Gambhir, V.; Reddy, M. N.

    2017-01-01

    A pre-resonance Raman spectroscopy based explosives detection system has been developed using UV laser at wavelength 266 nm having pulse energy of 30 mJ and repetition rate of 20 Hz. A 4-inch UV-enhanced collection optics and back-thinned UV-enhanced charged coupled device (CCD) coupled spectrometer has been used for analysis of the Raman signal. Spectral peak matching software has been developed indigenously for identification of explosives. A compact, tripod mounted and man-portable Raman system is developed for field applications. The system has capability to detect explosives and explosive derivatives over a range up to 40 m and has a sensitivity of 0.1% weight/volume.

  10. Raman Scattering at Resonant or Near-Resonant Conditions: A Generalized Short-Time Approximation

    NASA Astrophysics Data System (ADS)

    Mohammed, Abdelsalam; Sun, Yu-Ping; Miao, Quan; Ågren, Hans; Gel'mukhanov, Faris

    2012-02-01

    We investigate the dynamics of resonant Raman scattering in the course of the frequency detuning. The dephasing in the time domain makes the scattering fast when the photon energy is tuned from the absorption resonance. This makes frequency detuning to act as a camera shutter with a regulated scattering duration and provides a practical tool of controlling the scattering time in ordinary stationary measurements. The theory is applied to resonant Raman spectra of a couple of few-mode model systems and to trans-1,3,5-hexatriene and guanine-cytosine (G-C) Watson-Crick base pairs (DNA) molecules. Besides some particular physical effects, the regime of fast scattering leads to a simplification of the spectrum as well as to the scattering theory itself. Strong overtones appear in the Raman spectra when the photon frequency is tuned in the resonant region, while in the mode of fast scattering, the overtones are gradually quenched when the photon frequency is tuned more than one vibrational quantum below the first absorption resonance. The detuning from the resonant region thus leads to a strong purification of the Raman spectrum from the contamination by higher overtones and soft modes and purifies the spectrum also in terms of avoidance of dissociation and interfering fluorescence decay of the resonant state. This makes frequency detuning a very useful practical tool in the analysis of the resonant Raman spectra of complex systems and considerably improves the prospects for using the Raman effect for detection of foreign substances at ultra-low concentrations.

  11. 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.

  12. Raman Studies of Carbon Nanostructures

    NASA Astrophysics Data System (ADS)

    Jorio, Ado; Souza Filho, Antonio G.

    2016-07-01

    This article reviews recent advances on the use of Raman spectroscopy to study and characterize carbon nanostructures. It starts with a brief survey of Raman spectroscopy of graphene and carbon nanotubes, followed by recent developments in the field. Various novel topics, including Stokes-anti-Stokes correlation, tip-enhanced Raman spectroscopy in two dimensions, phonon coherence, and high-pressure and shielding effects, are presented. Some consequences for other fields—quantum optics, near-field electromagnetism, archeology, materials and soil sciences—are discussed. The review ends with a discussion of new perspectives on Raman spectroscopy of carbon nanostructures, including how this technique can contribute to the development of biotechnological applications and nanotoxicology.

  13. 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.

  14. Density functional theory based studies on the nature of Raman and resonance Raman scattering of nerve agent bound to gold and oxide-supported gold clusters: a plausible way of detection.

    PubMed

    Majumdar, D; Roszak, Szczepan; Leszczynski, Jerzy

    2010-04-01

    A detailed theoretical investigation has been carried out at the density functional level of theories to investigate the nature of Raman intensities of the -P=O stretching mode of a model nerve agent DFP (diisopropylfluorophosphate) when bound to different gold (Au(8), Au(20)) and oxide-supported gold (MgO...Au(4), CaO...Au(4), TiO(2)...Au(4), Al(2)O(3)...Au(4), M(16)O(16)...Au(8), and [M(16)O(15)...Au(8)](2+), M = Ca, Mg) clusters. All of these clusters and the DFP-bound clusters are fully optimized, and the computed energetics shows that DFP attaches itself weakly to these clusters. The normal Raman spectra calculations on these clusters show that there is substantial enhancement of the -P=O stretching mode of DFP compared to the isolated species. This enhancement has been found to be due to the polarization of the -P=O bond of DFP when bound to the clusters. Significant enhancement in intensity has been observed in the case of Au(n)...DFP (n = 8, 20), M(16)O(16)...Au(8)...DFP, and [M(16)O(15)...Au(8)](2+)...DFP (M = Ca, Mg) clusters. The resonance Raman calculations on the Au(n)...DFP (n = 8, 20) reveals that this enhancement could be made quite large and selective, which is a feature that is unique to the nerve agents and could be used as a property for detecting them.

  15. Tissue Oxygenation Monitoring using Resonance Raman Spectroscopy during Hemorrhage

    DTIC Science & Technology

    2013-12-27

    saturation measurements using resonance Raman intravital micros- copy. Am J Physiol Heart Circ Physiol. 2005;289:H488 H495. 14. Ward KR, Ivatury RR, Barbee...Nighswander-Rempel SP, Kupriyanov VV, Shaw RA. Relative contribu- tions of hemoglobin and myoglobin to near-infrared spectroscopic images of cardiac tissue...DC, Shapiro NI. The microcirculation image quality score: development and preliminary evaluation of a proposed approach to grading quality of image

  16. Guided-mode-resonance coupled localized surface plasmons for dually resonance enhanced Raman scattering sensing

    NASA Astrophysics Data System (ADS)

    Wang, Zheng; Liu, Chao; Li, Erwen; Chakravarty, Swapnajit; Xu, Xiaochuan; Wang, Alan X.; Fan, D. L.; Chen, Ray T.

    2017-02-01

    Raman scattering spectroscopy is a unique tool to probe vibrational, rotational, and other low-frequency modes of a molecular system and therefore could be utilized to identify chemistry and quantity of molecules. However, the ultralow efficient Raman scattering, which is only 1/109 1/1014 of the excitation light due to the small Raman scattering cross-sections of molecules, have significantly hindered its development in practical sensing applications. The discovery of surface-enhanced Raman scattering (SERS) in the 1970s and the significant progress in nanofabrication technique, provide a promising solution to overcome the inherent issues of Raman spectroscopy. It is found that In the vicinity of nanoparticles and their junctions, the Raman signals of molecules can be significantly improved by an enhancement factor as high as 1010, due to the ultrahigh electric field generated by the localized surface plasmons resonance (LSPR), where the intensity of Raman scattering is proportional to the |E|4. In this work, we propose and demonstrate a new approach combining LSPR from nanocapsules with densely assembled silver nanoparticles (NC-AgNPs) and guidemode- resonance (GMR) from dielectric photonic crystal slabs (PCSs) for SERS substrates with robustly high performance.

  17. Interferences in and lifetime measurement of a resonance electronic Raman effect using tunable pulsed laser techniques

    NASA Astrophysics Data System (ADS)

    Nicollin, D.; Koningstein, J. A.

    1980-07-01

    The excitation profile for the intensity of electronic Raman transitions of terbium aluminum garnet (TbAlG) in the spectral range of 483.0-680.0 nm is reported. The electronic Raman transitions take place between the crystal field levels of the split 7F 6 ground manifold of TbAlG with shifts of 73 cm -1 and 83 cm -1 and the electronic Raman process is induced with tunable pulsed and fixed wavelength cw lasers. The tunability of the former was employed to obtain detailed information of the behaviour of the Raman intensity if the wavelength of the exciting source is tuned throughout the region of 483.0-490.0 nm where 5Da 4 ← 7F 6 absorptions of TbAlG occur and the data reveal the occurrence of interference effects. We also report measurements of the shape of the pulse — due to resonance enhanced electronic Raman scattered light — in real time. These studies reveal that the lifetime of the resonating state (which is responsible for the enhancement of the Raman intensity) as determined from the tailing end of the said pulse is within experimental error equal to the lifetime τ = 33.5 ± 1 μs of this state measured in a direct way from the intensity decay of an appropriate fluorescence transition of TbAlG.

  18. Direct Observation of Thermal Equilibrium of Excited Triplet States of 9,10-Phenanthrenequinone. A Time-Resolved Resonance Raman Study.

    PubMed

    Kumar, Venkatraman Ravi; Rajkumar, Nagappan; Ariese, Freek; Umapathy, Siva

    2015-10-08

    The photochemistry of aromatic ketones plays a key role in various physicochemical and biological processes, and solvent polarity can be used to tune their triplet state properties. Therefore, a comprehensive analysis of the conformational structure and the solvent polarity induced energy level reordering of the two lowest triplet states of 9,10-phenanthrenequinone (PQ) was carried out using nanosecond-time-resolved absorption (ns-TRA), time-resolved resonance Raman (TR(3)) spectroscopy, and time dependent-density functional theory (TD-DFT) studies. The ns-TRA of PQ in acetonitrile displays two bands in the visible range, and these two bands decay with similar lifetime at least at longer time scales (μs). Interestingly, TR(3) spectra of these two bands indicate that the kinetics are different at shorter time scales (ns), while at longer time scales they followed the kinetics of ns-TRA spectra. Therefore, we report a real-time observation of the thermal equilibrium between the two lowest triplet excited states of PQ, assigned to nπ* and ππ* of which the ππ* triplet state is formed first through intersystem crossing. Despite the fact that these two states are energetically close and have a similar conformational structure supported by TD-DFT studies, the slow internal conversion (∼2 ns) between the T(2)(1(3)nπ*) and T(1)(1(3)ππ*) triplet states indicates a barrier. Insights from the singlet excited states of PQ in protic solvents [ J. Chem. Phys. 2015 , 142 , 24305 ] suggest that the lowest nπ* and ππ* triplet states should undergo hydrogen bond weakening and strengthening, respectively, relative to the ground state, and these mechanisms are substantiated by TD-DFT calculations. We also hypothesize that the different hydrogen bonding mechanisms exhibited by the two lowest singlet and triplet excited states of PQ could influence its ISC mechanism.

  19. 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.

  20. Resonance Raman and UV-visible spectroscopy of black dyes on textiles.

    PubMed

    Abbott, Laurence C; Batchelor, Stephen N; Smith, John R Lindsay; Moore, John N

    2010-10-10

    Resonance Raman and UV-visible diffuse reflectance spectra were recorded from samples of cotton, viscose, polyester, nylon, and acrylic textile swatches dyed black with one of seven single dyes, a mixture of two dyes, or one of seven mixtures of three dyes. The samples generally gave characteristic Raman spectra of the dyes, demonstrating that the technique is applicable for the forensic analysis of dyed black textiles. Survey studies of the widely used dye Reactive Black 5 show that essentially the same Raman spectrum is obtained on bulk sampling from the dye in solution, on viscose, on cotton at different uptakes, and on microscope sampling from the dye in cotton threads and single fibres. The effects of laser irradiation on the Raman bands and emission backgrounds from textile samples with and without dye are also reported. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

  1. Excited state proton transfer dynamics of thioacetamide in S2(ππ*) state: resonance Raman spectroscopic and quantum mechanical calculations study.

    PubMed

    Chen, Xiao; Zhao, Yanying; Zhang, Haibo; Xue, Jiadan; Zheng, Xuming

    2015-02-05

    The photophysics and photochemistry of thioacetamide (CH3CSNH2) after excitation to the S2 electronic state were investigated by using resonance Raman spectroscopy in conjunction with the complete active space self-consistent field (CASSCF) method and density functional theory (DFT) calculations. The A-band resonance Raman spectra in acetonitrile, methanol, and water were obtained at 299.1, 282.4, 266.0, 252.7, and 245.9 nm excitation wavelengths to probe the structural dynamics of thioacetamide in the S2 state. CASSCF calculations were done to determine the transition energies and structures of the lower-lying excited states, the conical intersection points CI(S2/S1) and CI(S1/S0), and intersystem crossing points. The structural dynamics of thioacetamide in the S2 state was revealed to be along eight Franck-Condon active vibrational modes ν15, ν11, ν14, ν10, ν8, ν12, ν18, and ν19, mostly in the CC/CS/CN stretches and the CNH8,9/CCH5,6,7/CCN/CCS in-plane bends as indicated by the corresponding normal mode descriptions. The S2 → S1 decay process via the S2/S1 conical intersection point as the major channel were excluded. The thione-thiol photoisomerization reaction mechanism of thioacetamide via the S2,FC → S'1,min excited state proton transfer (ESPT) reaction channel was proposed.

  2. A Study of the Dynamics of the Heme Pocket and C-helix in CooA upon CO Dissociation Using Time-Resolved Visible and UV Resonance Raman Spectroscopy.

    PubMed

    Otomo, Akihiro; Ishikawa, Haruto; Mizuno, Misao; Kimura, Tetsunari; Kubo, Minoru; Shiro, Yoshitsugu; Aono, Shigetoshi; Mizutani, Yasuhisa

    2016-08-18

    CooA is a CO-sensing transcriptional activator from the photosynthetic bacterium Rhodospirillum rubrum that binds CO at the heme iron. The heme iron in ferrous CooA has two axial ligands: His77 and Pro2. CO displaces Pro2 and induces a conformational change in CooA. The dissociation of CO and/or ligation of the Pro2 residue are believed to trigger structural changes in the protein. Visible time-resolved resonance Raman spectra obtained in this study indicated that the ν(Fe-His) mode, arising from the proximal His77-iron stretch, does not shift until 50 μs after the photodissociation of CO. Ligation of the Pro2 residue to the heme iron was observed around 50 μs after the photodissociation of CO, suggesting that the ν(Fe-His) band exhibits no shift until the ligation of Pro2. UV resonance Raman spectra suggested structural changes in the vicinity of Trp110 in the C-helix upon CO binding, but no or very small spectral changes in the time-resolved UV resonance Raman spectra were observed from 100 ns to 100 μs after the photodissociation of CO. These results strongly suggest that the conformational change of CooA is induced by the ligation of Pro2 to the heme iron.

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

    PubMed

    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.

  4. Resonant Raman scattering in self-assembled quantum dots

    SciTech Connect

    Menendez-Proupin, E.; Trallero-Giner, C.; Ulloa, S. E.

    1999-12-15

    A theoretical treatment for first-order resonant Raman scattering in self-assembled quantum dots (SAQD's) of different materials is presented. The dots are modeled as cylindrical disks with elliptical cross section, to simulate shape and confinement anisotropies obtained from the SAQD growth conditions. Coulomb interaction between electron and hole is considered in an envelope function Hamiltonian approach and the eigenvalues and eigenfunctions are obtained by a matrix diagonalization technique. By including excitonic intermediate states in the Raman process, the scattering efficiency and cross section are calculated for long-range Froehlich exciton-phonon interaction. The Froehlich interaction in the SAQD is considered in an approach in which both the mechanical and electrostatic matching boundary conditions are fulfilled at the SAQD interfaces. Exciton and confined phonon selection rules are derived for Raman processes. Characteristic results for SAQD's are presented, including InAs dots in GaAs, as well as CdSe dots in ZnSe substrates. We analyze how Raman spectroscopy would give information on carrier masses, confinement anisotropy effects, and SAQD geometry. (c) 1999 The American Physical Society.

  5. Vulnerable atherosclerotic plaque detection by resonance Raman spectroscopy

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

    A clear correlation has been observed between the resonance Raman (RR) spectra of plaques in the aortic tunica intimal wall of a human corpse and three states of plaque evolution: fibrolipid plaques, calcified and ossified plaques, and vulnerable atherosclerotic plaques (VPs). These three states of atherosclerotic plaque lesions demonstrated unique RR molecular fingerprints from key molecules, rendering their spectra unique with respect to one another. The vibrational modes of lipids, cholesterol, carotenoids, tryptophan and heme proteins, the amide I, II, III bands, and methyl/methylene groups from the intrinsic atherosclerotic VPs in tissues were studied. The salient outcome of the investigation was demonstrating the correlation between RR measurements of VPs and the thickness measurements of fibrous caps on VPs using standard histopathology methods, an important metric in evaluating the stability of a VP. The RR results show that VPs undergo a structural change when their caps thin to 66 μm, very close to the 65-μm empirical medical definition of a thin cap fibroatheroma plaque, the most unstable type of VP.

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

    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.

  7. 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.

  8. 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. Copyright © 2014 Elsevier B.V. All rights reserved.

  9. Resonance contributions to anti-Stokes/Stokes ratios under surface enhanced Raman scattering conditions

    NASA Astrophysics Data System (ADS)

    Maher, R. C.; Hou, J.; Cohen, L. F.; Le Ru, E. C.; Hadfield, J. M.; Harvey, J. E.; Etchegoin, P. G.; Liu, F. M.; Green, M.; Brown, R. J. C.; Milton, M. J. T.

    2005-08-01

    Anti-Stokes/Stokes asymmetries under surface enhanced Raman scattering (SERS) conditions are studied for a wide variety of SERS-active media and different analytes. Evidence is provided for the existence of underlying resonances that create these asymmetries. We show here that these resonances are associated with the electromagnetic coupling between the analyte (probe) and the metal. The work demonstrates the use of the anti-Stokes/Stokes ratio as a tool to understand the hierarchy of resonances in the SERS problem, which is essential for quantification purposes.

  10. Determination of resonance Raman cross-sections for use in biological SERS sensing with femtosecond stimulated Raman spectroscopy.

    PubMed

    Silva, W Ruchira; Keller, Emily L; Frontiera, Renee R

    2014-08-05

    Surface-enhanced Raman spectroscopy (SERS) is a promising technique for in vivo bioanalyte detection, but accurate characterization of SERS biosensors can be challenging due to difficulties in differentiating resonance and surface enhancement contributions to the Raman signal. Here, we quantitate the resonance Raman cross-sections for a commonly used near-infrared SERS dye, 3,3'-diethylthiatricarbocyanine (DTTC). It is typically challenging to measure resonance Raman cross-sections for fluorescent dye molecules due to the overwhelming isoenergetic fluorescence signal. To overcome this issue, we used etalon-based femtosecond stimulated Raman spectroscopy, which is intrinsically designed to acquire a stimulated Raman signal without strong fluorescence or interference from signals resulting from other four-wave mixing pathways. Using this technique, we found that the cross-sections for most of the resonantly enhanced modes in DTTC exceed 10(-25) cm(2)/molecule. These cross-sections lead to high signal magnitude SERS signals from even weakly enhancing SERS substrates, as much of what appears to be a SERS signal is actually coming from the intrinsically strong resonance Raman signal. Our work will lead to a more accurate determination of SERS enhancement factors and SERS substrate characterization in the biologically relevant near-infrared region, ultimately leading to a more widespread use of SERS for biosensing and bioimaging applications.

  11. Intervalley scattering by acoustic phonons in two-dimensional MoS2 revealed by double-resonance Raman spectroscopy.

    PubMed

    Carvalho, Bruno R; Wang, Yuanxi; Mignuzzi, Sandro; Roy, Debdulal; Terrones, Mauricio; Fantini, Cristiano; Crespi, Vincent H; Malard, Leandro M; Pimenta, Marcos A

    2017-03-09

    Double-resonance Raman scattering is a sensitive probe to study the electron-phonon scattering pathways in crystals. For semiconducting two-dimensional transition-metal dichalcogenides, the double-resonance Raman process involves different valleys and phonons in the Brillouin zone, and it has not yet been fully understood. Here we present a multiple energy excitation Raman study in conjunction with density functional theory calculations that unveil the double-resonance Raman scattering process in monolayer and bulk MoS2. Results show that the frequency of some Raman features shifts when changing the excitation energy, and first-principle simulations confirm that such bands arise from distinct acoustic phonons, connecting different valley states. The double-resonance Raman process is affected by the indirect-to-direct bandgap transition, and a comparison of results in monolayer and bulk allows the assignment of each Raman feature near the M or K points of the Brillouin zone. Our work highlights the underlying physics of intervalley scattering of electrons by acoustic phonons, which is essential for valley depolarization in MoS2.

  12. Intervalley scattering by acoustic phonons in two-dimensional MoS2 revealed by double-resonance Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Carvalho, Bruno R.; Wang, Yuanxi; Mignuzzi, Sandro; Roy, Debdulal; Terrones, Mauricio; Fantini, Cristiano; Crespi, Vincent H.; Malard, Leandro M.; Pimenta, Marcos A.

    2017-03-01

    Double-resonance Raman scattering is a sensitive probe to study the electron-phonon scattering pathways in crystals. For semiconducting two-dimensional transition-metal dichalcogenides, the double-resonance Raman process involves different valleys and phonons in the Brillouin zone, and it has not yet been fully understood. Here we present a multiple energy excitation Raman study in conjunction with density functional theory calculations that unveil the double-resonance Raman scattering process in monolayer and bulk MoS2. Results show that the frequency of some Raman features shifts when changing the excitation energy, and first-principle simulations confirm that such bands arise from distinct acoustic phonons, connecting different valley states. The double-resonance Raman process is affected by the indirect-to-direct bandgap transition, and a comparison of results in monolayer and bulk allows the assignment of each Raman feature near the M or K points of the Brillouin zone. Our work highlights the underlying physics of intervalley scattering of electrons by acoustic phonons, which is essential for valley depolarization in MoS2.

  13. Intervalley scattering by acoustic phonons in two-dimensional MoS2 revealed by double-resonance Raman spectroscopy

    PubMed Central

    Carvalho, Bruno R.; Wang, Yuanxi; Mignuzzi, Sandro; Roy, Debdulal; Terrones, Mauricio; Fantini, Cristiano; Crespi, Vincent H.; Malard, Leandro M.; Pimenta, Marcos A.

    2017-01-01

    Double-resonance Raman scattering is a sensitive probe to study the electron-phonon scattering pathways in crystals. For semiconducting two-dimensional transition-metal dichalcogenides, the double-resonance Raman process involves different valleys and phonons in the Brillouin zone, and it has not yet been fully understood. Here we present a multiple energy excitation Raman study in conjunction with density functional theory calculations that unveil the double-resonance Raman scattering process in monolayer and bulk MoS2. Results show that the frequency of some Raman features shifts when changing the excitation energy, and first-principle simulations confirm that such bands arise from distinct acoustic phonons, connecting different valley states. The double-resonance Raman process is affected by the indirect-to-direct bandgap transition, and a comparison of results in monolayer and bulk allows the assignment of each Raman feature near the M or K points of the Brillouin zone. Our work highlights the underlying physics of intervalley scattering of electrons by acoustic phonons, which is essential for valley depolarization in MoS2. PMID:28276472

  14. 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.

    1993-02-01

    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}][Pt(L){sub 2}](ClO{sub 4}){sub 4} ; L=1, 2-diaminoethane. The luminescence experiments support the existence of tail states in the band gap region, which indicate the presence of disorder. In contrast, the RR measurements conclusively demonstrated that the effects of static structural disorder on the vibrational spectroscopy can be neglected. This apparently paradoxical result can be explained by considering the zero-point motion of the lattice. The experimental results are compared to recent theoretical models.

  15. In vitro recognition of DNA base pairs by histones in histone-DNA complexes and reconstituted core particles: an ultraviolet resonance Raman study.

    PubMed Central

    Laigle, A; Chinsky, L; Turpin, P Y; Liquier, J; Taillandier, E

    1982-01-01

    Resonance Raman spectra of complexes between DNA and the four core histones, alone or associated, have been investigated in vitro using excitations at 300 and 257 nm, which give complementary informations about the DNA bases. H2A and H2B fractions recognize the G-C base pairs, while H3 and H4 (arginine rich fractions) recognize the A-T base pairs. The associated fractions form complexes with DNA which yield about the same DNA spectral modifications as the DNA-H4 complexes. This reveals the important role of the arginine rich fractions in the core particle formation and confirms the preferential in vitro assembly of nucleosome cores on A-T rich regions of DNA (25). PMID:7155896

  16. Potential-dependent surface-enhanced resonance Raman spectroscopy at nanostructured TiO2 : a case study on cytochrome b5.

    PubMed

    Han, Xiao Xia; Köhler, Christopher; Kozuch, Jacek; Kuhlmann, Uwe; Paasche, Lars; Sivanesan, Arumugam; Weidinger, Inez M; Hildebrandt, Peter

    2013-12-20

    Nanostructured titanium dioxide (TiO2 ) electrodes, prepared by anodization of titanium, are employed to probe the electron-transfer process of cytochrome b5 (cyt b5 ) by surface-enhanced resonance Raman (SERR) spectroscopy. Concomitant with the increased nanoscopic surface roughness of TiO2 , achieved by raising the anodization voltage from 10 to 20 V, the enhancement factor increases from 2.4 to 8.6, which is rationalized by calculations of the electric field enhancement. Cyt b5 is immobilized on TiO2 under preservation of its native structure but it displays a non-ideal redox behavior due to the limited conductivity of the electrode material. The electron-transfer efficiency which depends on the crystalline phase of TiO2 has to be improved by appropriate doping for applications in bioelectrochemistry. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Real-Time Measurements of the Redox States of c-Type Cytochromes in Electroactive Biofilms: A Confocal Resonance Raman Microscopy Study

    PubMed Central

    Virdis, Bernardino; Millo, Diego; Donose, Bogdan C.; Batstone, Damien J.

    2014-01-01

    Confocal Resonance Raman Microscopy (CRRM) was used to probe variations of redox state of c-type cytochromes embedded in living mixed-culture electroactive biofilms exposed to different electrode polarizations, under potentiostatic and potentiodynamic conditions. In the absence of the metabolic substrate acetate, the redox state of cytochromes followed the application of reducing and oxidizing electrode potentials. Real-time monitoring of the redox state of cytochromes during cyclic voltammetry (CV) in a potential window where cytochromes reduction occurs, evidenced a measurable time delay between the oxidation of redox cofactors probed by CV at the electrode interface, and oxidation of distal cytochromes probed by CRRM. This delay was used to tentatively estimate the diffusivity of electrons through the biofilm. In the presence of acetate, the resonance Raman spectra of young (10 days, j = 208±49 µA cm−2) and mature (57 days, j = 267±73 µA cm−2) biofilms show that cytochromes remained oxidized homogeneously even at layers as far as 70 µm from the electrode, implying the existence of slow metabolic kinetics that do not result in the formation of a redox gradient inside the biofilm during anode respiration. However, old biofilms (80 days, j = 190±37 µA cm−2) with thickness above 100 µm were characterized by reduced catalytic activity compared to the previous developing stages. The cytochromes in these biofilm were mainly in the reduced redox state, showing that only aged mixed-culture biofilms accumulate electrons during anode respiration. These results differ substantially from recent observations in pure Geobacter sulfurreducens electroactive biofilms, in which accumulation of reduced cytochromes is already observed in thinner biofilms, thus suggesting different bottlenecks in current production for mixed-culture and G. sulfurreducens biofilms. PMID:24587123

  18. Real-time measurements of the redox states of c-type cytochromes in electroactive biofilms: a confocal resonance Raman Microscopy study.

    PubMed

    Virdis, Bernardino; Millo, Diego; Donose, Bogdan C; Batstone, Damien J

    2014-01-01

    Confocal Resonance Raman Microscopy (CRRM) was used to probe variations of redox state of c-type cytochromes embedded in living mixed-culture electroactive biofilms exposed to different electrode polarizations, under potentiostatic and potentiodynamic conditions. In the absence of the metabolic substrate acetate, the redox state of cytochromes followed the application of reducing and oxidizing electrode potentials. Real-time monitoring of the redox state of cytochromes during cyclic voltammetry (CV) in a potential window where cytochromes reduction occurs, evidenced a measurable time delay between the oxidation of redox cofactors probed by CV at the electrode interface, and oxidation of distal cytochromes probed by CRRM. This delay was used to tentatively estimate the diffusivity of electrons through the biofilm. In the presence of acetate, the resonance Raman spectra of young (10 days, j = 208 ± 49 µA cm(-2)) and mature (57 days, j = 267 ± 73 µA cm(-2)) biofilms show that cytochromes remained oxidized homogeneously even at layers as far as 70 µm from the electrode, implying the existence of slow metabolic kinetics that do not result in the formation of a redox gradient inside the biofilm during anode respiration. However, old biofilms (80 days, j = 190 ± 37 µA cm(-2)) with thickness above 100 µm were characterized by reduced catalytic activity compared to the previous developing stages. The cytochromes in these biofilm were mainly in the reduced redox state, showing that only aged mixed-culture biofilms accumulate electrons during anode respiration. These results differ substantially from recent observations in pure Geobacter sulfurreducens electroactive biofilms, in which accumulation of reduced cytochromes is already observed in thinner biofilms, thus suggesting different bottlenecks in current production for mixed-culture and G. sulfurreducens biofilms.

  19. Evidence of the Fano resonance in a temperature dependent Raman study of CaCu3Ti4O12 and SrCu3Ti4O12.

    PubMed

    Mishra, Dileep K; Sathe, V G

    2012-06-27

    Phononic excitations have been investigated using Raman scattering studies on CaCu(3)Ti(4)O(12) and SrCu(3)Ti(4)O(12) compounds as a function of temperature down to 10 K. Evidence of the Fano resonance effect is found in the A(g)(1) mode with an asymmetric phonon line shape that occurs because of composite electron-phonon scattering due to the onset of metallic fractions in the system. The evolution of the Fano line shape with temperature affirms the existence of nanoscale phase separation and the prominence of orbitally disrupted metallic regions above 100 K. Anomalies in the evolution of the line width of the A(g)(1) Raman mode with temperature are observed around 100 K where these compounds show an orbital order/disorder transition. These anomalies manifest mutual coupling of orbital degrees of freedom to lattice degrees of freedom.

  20. 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.

  1. UV Raman imaging--a promising tool for astrobiology: comparative Raman studies with different excitation wavelengths on SNC Martian meteorites.

    PubMed

    Frosch, Torsten; Tarcea, Nicolae; Schmitt, Michael; Thiele, Hans; Langenhorst, Falko; Popp, Jürgen

    2007-02-01

    The great capabilities of UV Raman imaging have been demonstrated on the three Martian meteorites: Sayh al Uhaymir, Dar al Gani, and Zagami. Raman spectra without disturbing fluorescence and with high signal-to-noise-ratios and full of spectral features were derived. This result is of utmost importance for the development of powerful instruments for space missions. By point scanning the surfaces of the meteorite samples, it was possible for the first time to construct UV-Raman images out of the array of Raman spectra. Deep-UV Raman images are to the best of our knowledge presented for the first time. The images were used for a discussion of the chemical-mineralogical composition and texture of the meteorite surfaces. Comparative Raman studies applying visible and NIR Raman excitation wavelengths demonstrate a much better performance for UV Raman excitation. This comparative study of different Raman excitation wavelengths at the same sample spots was done by constructing a versatile, robust sample holder with a fixed micro-raster. The overall advantages of UV resonance Raman spectroscopy in terms of sensitivity and selectivity are demonstrated and discussed. Finally the application of this new technique for a UV Raman instrument for envisaged astrobiological focused space missions is suggested.

  2. Unusual Raman spectra of para-nitroaniline by sequential Fermi resonances.

    PubMed

    Xia, Jiarui; Zhu, Ling; Feng, Yanting; Li, Yongqing; Zhang, Zhenglong; Xia, Lixin; Liu, Liwei; Ma, Fengcai

    2014-01-01

    In this communication, we report the unusual Raman spectra of para-nitroaniline (PNA) by sequential Fermi resonances. The combinational mode 1292 cm(-1) in the experimental Raman spectrum indirectly gains the initial spectral weight at 1392 cm(-1) by three sequential Fermi resonances. These Fermi resonances result in the strong interaction between the donor group of NH2 and the acceptor group of NO2. Our theoretical calculations provide reasonable interpretation for the abnormal Raman spectra of PNA. Experimental surface enhanced Raman scattering (SERS) spectrum of PNA further confirmed our conclusion, where the strongest Raman peak at 1292 cm(-1) is very weak, while the Raman peak at 1392 cm(-1) becoming the strongest Raman peak, which is consistent with the theoretical simulations.

  3. Raman resonance in the strained Ge quantum dot array.

    PubMed

    Talochkin, A B; Markov, V A

    2008-07-09

    We study the Raman resonance of a Ge quantum dot (QD) array grown pseudomorphically to a Si matrix using low-temperature molecular-beam epitaxy. A change of the resonance energy and the shape of the resonance curve in comparison with bulk Ge are observed. These features are shown to be explained by taking into account QD strain and the quasistationary character of the electronic states responsible for the observed resonance. Application of a model of the two-dimensional critical point of the interband density of states allows us to estimate the damping parameter and localization size of these states. It is shown that the observed enhancement of the resonance amplitude in a QD array as compared to the bulk case is related to transformation of the interband density of states into the δ-function due to quantization of the electron-hole spectrum.

  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

    2014-07-09

    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. Quantitative evaluation of proteins with bicinchoninic acid (BCA): resonance Raman and surface-enhanced resonance Raman scattering-based methods.

    PubMed

    Chen, Lei; Yu, Zhi; Lee, Youngju; Wang, Xu; Zhao, Bing; Jung, Young Mee

    2012-12-21

    A rapid and highly sensitive bicinchoninic acid (BCA) reagent-based protein quantitation tool was developed using competitive resonance Raman (RR) and surface-enhanced resonance Raman scattering (SERRS) methods. A chelation reaction between BCA and Cu(+), which is reduced by protein in an alkaline environment, is exploited to create a BCA-Cu(+) complex that has strong RR and SERRS activities. Using these methods, protein concentrations in solutions can be quantitatively measured at concentrations as low as 50 μg mL(-1) and 10 pg mL(-1). There are many advantages of using RR and SERRS-based assays. These assays exhibit a much wider linear concentration range and provide an additional one (RR method) to four (SERRS method) orders of magnitude increase in detection limits relative to UV-based methods. Protein-to-protein variation is determined using a reference to a standard curve at concentrations of BSA that exhibits excellent recoveries. These novel methods are extremely accurate in detecting total protein concentrations in solution. This improvement in protein detection sensitivity could yield advances in the biological sciences and medical diagnostic field and extend the applications of reagent-based protein assay techniques.

  6. Quantitative surface-enhanced resonance Raman scattering of phthalocyanine-labelled oligonucleotides

    PubMed Central

    Macaskill, A.; Chernonosov, A. A.; Koval, V. V.; Lukyanets, E. A.; Fedorova, O. S.; Smith, W. E.; Faulds, K.; Graham, D.

    2007-01-01

    The evaluation of phthalocyanine labels for the surface-enhanced resonance Raman scattering (SERRS) detection of oligonucleotides is reported. Three phthalocyanine-labelled oligonucleotides were assessed, each containing a different metal centre. Detection limits for each labelled oligonucleotide were determined using two excitation frequencies where possible. Limits of detection as low as 2.8 × 10−11 mol. dm−3 were obtained which are comparable to standard fluorescently labelled probes used in previous SERRS studies. The identification of two phthalocyanine-labelled oligonucleotides without separation was also demonstrated indicating their suitability for multiplexing. This study extends the range of labels suitable for quantitative surface-enhanced resonance Raman scattering with silver nanoparticles and offers more flexibility and choice when considering SERRS for quantitative DNA detection. PMID:17289751

  7. 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

  8. Absolute determination of cross sections for resonant Raman scattering on silicon

    NASA Astrophysics Data System (ADS)

    Müller, Matthias; Beckhoff, Burkhard; Ulm, Gerhard; Kanngießer, Birgit

    2006-07-01

    We studied the resonant Raman scattering of x rays in the vicinity of the K absorption edge of silicon. The investigation was carried out at the plane grating monochromator beamline for undulator radiation of the PTB laboratory at BESSY II in Berlin. Cross sections were determined absolutely for a wide energy range of incident photons with small relative uncertainties employing calibrated instrumentation avoiding any reference samples. The experimentally determined values differ clearly from the theoretical ones found in the literature.

  9. Resonance Raman Spectroscopy of Purple Membrane from Halobacterium Halobium.

    NASA Astrophysics Data System (ADS)

    Argade, Pramod Vasant

    Purple membrane from the halophilic bacteria, Halobacterium halobium, contains the protein, bacteriorhodopsin, which functions as a light transducing proton pump. Understanding the molecular mechanism underlying the functioning of bacteriorhodopsin is a key problem in membrane biophysics. After absorbing a photon, this protein cycles through a series of characteristic intermeidate states and pumps H('+) ions across the membrane. In this way, the energy of the absorbed photon is stored in the electrochemical potential gradient formed across the membrane. This energy is subsequently available for metabolism by the bacterium. Bacteriorhodopsin consists of a retinal chromophore (which is responsible for the purple color) bound to the protein, bacterioopsin, whose sequence is known and consists of 248 amino acid residues. There is evidence that conformational changes in the chromophore may contribute to the proton pumping action. Resonance Raman light scattering provides a selective tool to monitor the conformational changes in the chromophore during the proton pumping cycle. This dissertation consists of applying resonance Raman light scattering in conjunction with a variety of newly developed experimental techniques to gain information about the mode of action of bacteriorhodopsin. By selective isotopic labelling of (epsilon)-amino nitrogen of the lysine residues of the protein, the site of attachment of the chromophore with the protein was verified by in situ measurements. Also, a model proposing a secondary interaction of the chromophore with a lysine residue other than the binding site of the chromophore was tested using this method. Furthermore, by selective isotopic labelling of only a part of the protein the location of the lysine on the protein to which the chromophore is bound, was found by in situ measurements to be the fragment consisting of amino acid residues 72 through 248 of the protein. This is inconsistent with the previously reported binding site at

  10. 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.

  11. 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.

  12. Origin invariance in vibrational resonance Raman optical activity.

    PubMed

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

    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.

  13. Elucidation of Chemical Reactions by Two-Dimensional Resonance Raman Spectroscopy

    NASA Astrophysics Data System (ADS)

    Moran, Andrew

    Two-dimensional (2D) Raman spectroscopies were proposed by Mukamel and Loring in1985 as a method for resolving line broadening mechanisms of vibrational motions in liquids. Significant technical issues challenged the development of both five- and seven-pulse 2D Raman spectroscopies. For this reason, 2D Raman experiments were largely abandoned in 2002 following the first demonstrations of 2D infrared spectroscopies (i.e., an alternate approach for obtaining similar information). We have recently shown that 2D Raman experiments conducted under electronically resonant conditions are much less susceptible to the problems encountered in the earlier 2D Raman work, which was carried out off-resonance. In effect, Franck-Condon activity obviates the problematic selection rules encountered under electronically off-resonant conditions. In this presentation, I will discuss applications of 2D resonance Raman spectroscopies to photodissocation reactions of triiodide and myoglobin. It will be shown that vibrational resonances of the reactants and products can be displayed in separate dimensions of a 2D resonance Raman spectrum when the photo-dissociation reaction is fast compared to the vibrational period. Such 2D spectra expose correlations between the nonequilibrium geometry of the reactant and the distribution of vibrational quanta in the product, thereby yielding insight in the photo-dissociation mechanism. Our results suggest that the ability of 2D resonance Raman spectroscopy to detect correlations between reactants and products will generalize to other ultrafast processes such as electron transfer and energy transfer.

  14. Resonance Raman spectroscopic study of the interaction between Co(II)rrinoids and the ATP:corrinoid adenosyltransferase PduO from Lactobacillus reuteri.

    PubMed

    Park, Kiyoung; Mera, Paola E; Escalante-Semerena, Jorge C; Brunold, Thomas C

    2016-09-01

    The human-type ATP:corrinoid adenosyltransferase PduO from Lactobacillus reuteri (LrPduO) catalyzes the adenosylation of Co(II)rrinoids to generate adenosylcobalamin (AdoCbl) or adenosylcobinamide (AdoCbi(+)). This process requires the formation of "supernucleophilic" Co(I)rrinoid intermediates in the enzyme active site which are properly positioned to abstract the adeonsyl moiety from co-substrate ATP. Previous magnetic circular dichroism (MCD) spectroscopic and X-ray crystallographic analyses revealed that LrPduO achieves the thermodynamically challenging reduction of Co(II)rrinoids by displacing the axial ligand with a non-coordinating phenylalanine residue to produce a four-coordinate species. However, relatively little is currently known about the interaction between the tetradentate equatorial ligand of Co(II)rrinoids (the corrin ring) and the enzyme active site. To address this issue, we have collected resonance Raman (rR) data of Co(II)rrinoids free in solution and bound to the LrPduO active site. The relevant resonance-enhanced vibrational features of the free Co(II)rrinoids are assigned on the basis of rR intensity calculations using density functional theory to establish a suitable framework for interpreting rR spectral changes that occur upon Co(II)rrinoid binding to the LrPduO/ATP complex in terms of structural perturbations of the corrin ring. To complement our rR data, we have also obtained MCD spectra of Co(II)rrinoids bound to LrPduO complexed with the ATP analogue UTP. Collectively, our results provide compelling evidence that in the LrPduO active site, the corrin ring of Co(II)rrinoids is firmly locked in place by several amino acid side chains so as to facilitate the dissociation of the axial ligand.

  15. Theoretical studies of resonance enhanced stimulated raman scattering (RESRS) of frequency doubled Alexandrite laser wavelength in cesium vapor. Progress report, July-December 1987

    SciTech Connect

    Lawandy, N.M.

    1987-01-01

    The third phase of research will focus on the propagation and energy extraction of the pump and SERS beams in a variety of configurations including oscillator structures. In order to address these questions a numerical code capable of allowing for saturation and full transverse beam evolution is required. The method proposed is based on a discretized propagation energy extraction model which uses a Kirchoff integral propagator coupled to the three level Raman model already developed. The model will have the resolution required by diffraction limits and will use the previous density matrix results in the adiabatic following limit. Owing to its large computational requirements, such a code must be implemented on a vector array processor. One code on the Cyber is being tested by using previously understood two-level laser models as guidelines for interpreting the results. Two tests were implemented: the evolution of modes in a passive resonator and the evolution of a stable state of the adiabatically eliminated laser equations. These results show mode shapes and diffraction losses for the first case and relaxation oscillations for the second one. Finally, in order to clarify the computing methodology used to exploit the speed of the Cyber's computational speed, the time it takes to perform both of the computations previously mentioned to run on the Cyber and VAX 730 must be measured. Also included is a short description of the current laser model (CAVITY.FOR) and a flow chart of the test computations.

  16. Resonance raman and absorption studies of the configurations of photochromic 3-alkyl-substituted 1,5-diphenylformazans: steric effect of the substituent

    NASA Astrophysics Data System (ADS)

    Hiura, Hidefumi; Takahashi, Hiroaki

    1989-09-01

    Resonance Raman spectra reveal that 3-alkyl-substituted 1,5-diphenylformazans exist as one of the following three isomeric species in the solid state: the yellow isomer has the trans- anti-s- trans configuration with respect to the NN, CN and CN bonds of the formazan skeleton, the red isomer has the trans- syn-s- trans configuration and the other red isomer has the trans- syn-s- cis configuration. The relative stabilities of these isomers are determined by the bulkiness of the substituent. When the substituent is small, the fully extended trans- anti-s- trans configuration is most stable. However, when the substituent is large, the partially folded trans- syn-s- trans configuration becomes stable and when the substituent is very bulky, the more folded trans- syn-s cis configuration is most stable. In solution these isomers are in equilibrium, the relative abundance being dependent on the nature of the solvent as well as on the bulkiness of the substituent.

  17. Structural study of various substituted biphenyls and their radical anions based on time-resolved resonance Raman spectroscopy combined with pulse radiolysis.

    PubMed

    Choi, Jungkweon; Cho, Dae Won; Tojo, Sachiko; Fujitsuka, Mamoru; Majima, Tetsuro

    2015-02-05

    The structures of various para-substituted biphenyls (Bp-X; X = -OH, -OCH3, -CH3, -H, -CONH2, -COOH, and -CN) and their radical anions (Bp-X(•-)) were investigated by time-resolved resonance Raman spectroscopy combined with pulse radiolysis. The inter-ring C1-C1' stretching modes (ν6) of Bp-X were observed at ∼1285 cm(-1), whereas the ν6 modes of Bp-X(•-) with an electron-donating or -withdrawing substituent were significantly up-shifted. The difference (Δf) between the ν6 frequencies of Bp-X and Bp-X(•-) showed a significant dependence on the electron affinity of the substituent and exhibited a correlation with the Hammett substituent constants (σp). In contrast to Bp-H(•-) with a planar geometry, the theoretical and experimental results reveal that all Bp-X(•-) with an electron-donating or -withdrawing substituent have a slightly twisted structure. The twisted structure of Bp-X(•-) is due to the localization of the unpaired electron and negative charge density on one phenyl moiety in Bp-X(•-).

  18. Pre-processing of ultraviolet resonance Raman spectra.

    PubMed

    Simpson, John V; Oshokoya, Olayinka; Wagner, Nicole; Liu, Jing; JiJi, Renee D

    2011-03-21

    The application of UV excitation sources coupled with resonance Raman have the potential to offer information unavailable with the current inventory of commonly used structural techniques including X-ray, NMR and IR analysis. However, for ultraviolet resonance Raman (UVRR) spectroscopy to become a mainstream method for the determination of protein secondary structure content and monitoring protein dynamics, the application of multivariate data analysis methodologies must be made routine. Typically, the application of higher order data analysis methods requires robust pre-processing methods in order to standardize the data arrays. The application of such methods can be problematic in UVRR datasets due to spectral shifts arising from day-to-day fluctuations in the instrument response. Additionally, the non-linear increases in spectral resolution in wavenumbers (increasing spectral data points for the same spectral region) that results from increasing excitation wavelengths can make the alignment of multi-excitation datasets problematic. Last, a uniform and standardized methodology for the subtraction of the water band has also been a systematic issue for multivariate data analysis as the water band overlaps the amide I mode. Here we present a two-pronged preprocessing approach using correlation optimized warping (COW) to alleviate spectra-to-spectra and day-to-day alignment errors coupled with a method whereby the relative intensity of the water band is determined through a least-squares determination of the signal intensity between 1750 and 1900 cm(-1) to make complex multi-excitation datasets more homogeneous and usable with multivariate analysis methods.

  19. η collective mode as A1 g Raman resonance in cuprate superconductors

    NASA Astrophysics Data System (ADS)

    Montiel, X.; Kloss, T.; Pépin, C.; Benhabib, S.; Gallais, Y.; Sacuto, A.

    2016-01-01

    We discuss the possible existence of a spin singlet excitation with charge ±2 (η mode) originating the A1 g Raman resonance in cuprate superconductors. This η mode relates the d -wave superconducting singlet pairing channel to a d -wave charge channel. We show that the η boson forms a particle-particle bound state below the 2 Δ threshold of the particle-hole continuum where Δ is the maximum d -wave gap. Within a generalized random phase approximation and Bethe-Salpeter approximation study, we find that this mode has energies similar to the resonance observed with inelastic neutron scattering below the superconducting (SC) coherent peak at 2 Δ in various SC cuprate compounds. We show that it is a very good candidate for the resonance observed in Raman scattering below the 2 Δ peak in the A1 g symmetry. Since the η mode sits in the S =0 channel, it may be observable via Raman, x-ray, or electron energy loss spectroscopy probes.

  20. Temperature dependence of the resonance Raman spectra of plastocyanin and azurin between cryogenic and ambient conditions.

    PubMed

    Woodruff, W H; Norton, K A; Swanson, B I; Fry, H A

    1984-02-01

    Resonance Raman spectra of spinach plastocyanin and Pseudomonas aeruginosa azurin were studied as a function of temperature between 10 K and 300 K. The spectra are markedly improved both in signal/noise ratio and in resolution at low temperatures. The assignments of the resonance Raman-active vibrations are reinterpreted in view of the number and intensities of peaks observed in the low-temperature spectra. Features appear in the low-temperature spectra of azurin that may be due to copper-bound methionine. The plastocyanin spectra undergo a transition between 220 K and the melting point of water that results in dramatically narrowed peaks at lower temperature and a shift in the carbon-sulfur stretching frequency of the copper-bound cysteine, suggesting a structural change in the active site and an accompanying effect on vibrational dephasing. Considering that the structures and nonvibrational spectroscopies of these two proteins are similar, the substantial differences in the resonance Raman spectra are striking and significant.

  1. 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.

  2. Third-order nonlinearities in molecular hydrogen - Two-photon resonance enhanced third-harmonic generation and Raman scattering

    NASA Technical Reports Server (NTRS)

    Pan, C.-L.; She, C.-Y.; Fairbank, W. M., Jr.; Billman, K. W.

    1977-01-01

    Effects of quantum mechanical interferences on third-order susceptibilities in molecules are studied. First principle calculations for molecular hydrogen are presented and shown to agree with results derived from experimental stimulated Raman gain and spontaneous Raman cross-section data. 10 percent third-harmonic conversion efficiency in H2 at 1 atm without phase matching should require a 150 MW per sq cm at 4.81 microns. As little as 5.9-MW power is sufficient when the beam is properly focused. Resonance Raman scattering (RRS) is proposed for experimentally investigating the interference effects, which tend to reduce the strength of third-order nonlinear susceptibilities.

  3. Theoretical studies of Resonance Enhanced Stimulated Raman Scattering (RESRS) of frequency-doubled Alexandrite laser wavelength in cesium vapor. Progress report, January-June 1987

    SciTech Connect

    Lawandy, N.M.

    1987-01-01

    The solutions for the imaginary susceptibility of the Raman field transition with arbitrary relaxation rates and field strengths are examined for three different sets of relaxation rates. These rates correspond to: (1) Far Infrared (FIR) Raman lasers in the diabatic collision regime without consideration of coupled population decay in a closed system, (2) Raman FIR lasers in the diabatic collision regime with coupled population conserving decay, and (3) IR Raman gain in cesium vapor. 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.

  4. Origin of negative and dispersive features in anti-Stokes and resonance femtosecond stimulated Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Frontiera, Renee R.; Shim, Sangdeok; Mathies, Richard A.

    2008-08-01

    Femtosecond stimulated Raman spectroscopy is extended to probe ground state anti-Stokes vibrational features. Off resonance, negative anti-Stokes features are seen that are the mirror image of the positive Stokes side spectra. On resonance, the observed dispersive lineshapes are dramatically dependent on the frequencies of the picosecond pump and femtosecond probe pulses used to generate the stimulated Raman spectra. These observations are explained by the contributions of the inverse Raman and hot luminescence four-wave mixing processes discussed by Sun et al. [J. Chem. Phys. 128, 144114 (2008)], which contribute to the overall femtosecond stimulated Raman signal.

  5. Absorption and resonance Raman spectra of Pb2, Pb3, and Pb4 in xenon matrices

    NASA Technical Reports Server (NTRS)

    Stranz, D. D.; Khanna, R. K.

    1981-01-01

    Matrix isolation techniques are used to investigate the spectra of lead molecules and, in particular, to obtain resonance Raman spectra of lead vapors isolated in solid xenon matrices. The presence of Pb2 is confirmed by the visible adsorption, and Raman spectra yield a vibrational frequency for the ground state of 108 per cm and a dissociation energy of 8200 per cm. A second resonance Raman progression indicates a Pb3 species of D3h symmetry. Finally, two additional Raman features at approximately 111 per cm spacing are evidence for a third species, tentatively identified as Pb4.

  6. Correlation between vibrational frequencies and hydrogen bonding states of the guanine ring studied by UV resonance Raman spectroscopy of 2'-deoxy-3',5'-bis(triisopropylsilyl)guanosine dissolved in various solvents

    NASA Astrophysics Data System (ADS)

    Toyama, Akira; Hamuara, Mutsuo; Takeuchi, Hideo

    1996-06-01

    Ultraviolet resonance Raman spectra of 2'-deoxy-3',5'-bis(triisopropylsilyl)guanosine (TPS-dGuo) were recorded in non-hydrogen bonding, proton acceptor, and proton donor/acceptor solvents. Raman spectral changes observed on going from inert to proton acceptor solvents were ascribed to the hydrogen bonding at the proton donor sites of the guanine ring (N1H and C2NH 2), and the spectral changes associated with the solvent change from proton acceptor to donor/acceptor were ascribed to the hydrogen bonding at the proton acceptor sites (N3, C6O, and N7). A Raman band appearing at 1624 cm -1 in inert solvents is assigned mainly to the NH 2 scissors mode and its frequency changes to ≈ 1640 cm -1 in acceptor solvents, reflecting the hydrogen bonding at C2NH 2. Another band at 1581 cm -1, arising largely from the N1H bend, shows an upshift of ≈ 10 cm -1 upon hydrogen bonding at either N1H or acceptor sites. Hydrogen bonding at the acceptor sites also produces frequency shifts of other Raman bands (at 1710, 1565, 1528, 1481, and 1154 cm -1 in 1,2-dichloroethane solution). Among the Raman bands listed above, the 1710 cm -1 band due to the C6O stretch decreases in frequency, whereas the others increase. The downshift of the C6O stretching frequency is correlated with the strength of hydrogen bonding at C6O. The frequency of the 1481 cm -1 band increases with a decrease of the C6O stretching frequency, indicating that the 1481 cm -1 band is also a marker of hydrogen bonding at C6O. This finding is in sharp contrast to the previously proposed correlation with the hydrogen bonding at N7. The 1565 cm -1 band is assigned to a vibration mainly involving the N1C2N3 linkage, and its frequency increases with increasing strength of the hydrogen bond at N3. Three bands around 1315, 1180, and 1030 cm -1, which are known to be sensitive to the ribose ring puckering and glycosidic bond orientation, also show small frequency changes upon hydrogen

  7. 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.

  8. Ultranarrow resonance peaks in the transmission and reflection spectra of a photonic crystal cavity with Raman gain

    SciTech Connect

    Arkhipkin, V. G.; Myslivets, S. A.

    2009-12-15

    The Raman gain of a probe light in a three-state LAMBDA scheme placed into a defect of a one-dimensional photonic crystal is studied theoretically. We show that there exists a pump intensity range, where the transmission and reflection spectra of the probe field exhibit simultaneously occurring narrow peaks (resonances) whose position is determined by the Raman resonance. Transmission and reflection coefficients can be larger than unity at pump intensities on the order of tens of muW/cm{sup 2}. When the pump intensity is outside this region, the peak in the transmission spectrum turns into a narrow dip. The nature of narrow resonances is attributed to a drastic dispersion of the nonlinear refractive index in the vicinity of the Raman transition, which leads to a significant reduction in the group velocity of the probe wave.

  9. Deep-UV resonance Raman imaging of a cell (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Kumamoto, Yasuaki

    2016-09-01

    Raman microscopy enables a sensitive, label-free molecular imaging of cells. Employing deep-UV (DUV) light for Raman excitation allows selective measurement of nucleotide bases and aromatic amino acids in a cell, without spectral overlapping of components with a large quantity (i.e. lipid, peptide), because their Raman scattering are specifically enhanced due to the resonance effect. To implement DUV resonance Raman imaging of cells, I previously established a home-built Raman microscope equipped with a DUV laser (λ = 257.2 nm). Raman image representing the distribution of cellular nucleic acid can be reconstructed with the intensity of a Raman band selectively assigned to adenine and guanine. Unfortunately, DUV resonance Raman imaging of cells is severely hindered by molecular photodegradation that occurs after a molecule absorbs DUV light during Raman measurement, precluding a high signal-to-noise ratio and repetitive measurement. To address this issue, I developed a technique for molecular protection under DUV exposure; the trivalent ions of lanthanide group including terbium, europium, and thulium could significantly suppress the molecular photodegradation by relaxing the DUV-excited molecules. The buffer solution containing any of these lanthanide ions with the concentration of 100 µM or higher could provide less destruction of the cellular structures, including nucleotide bases, than the one without the ions, under DUV exposure. Utilizing such protective effects of the lanthanide ions, I successfully achieved a twice higher signal-to-noise ratio and repetitive DUV Raman imaging of cells.

  10. Spectroscopic studies of thiatri-, penta- and heptamethine cyanine dyes II. Infrared and resonance Raman spectra of thiatri-, penta- and heptamethine cyanine dyes

    NASA Astrophysics Data System (ADS)

    Fujimoto, Yasuhiko; Katayama, Norihisa; Ozaki, Yukihiro; Yasui, Shigeo; Iriyama, Keiji

    1992-11-01

    Infrared (IR) and resonance Raman (RR) spectra of thiatri-, penta- and heptamethine cyanine dyes in the solid state and in solution have been measured. Most of the intense bands observed in the 1600-1100 cm -1 region of the RR spectra may be assigned to totally symmetric stretching modes of the central conjugated system of the cyanines, while most of the strong IR bands in the 1600-1300 cm -1 region are probably due to antisymmetric stretching modes. The intense RR bands do not have their counterparts in the IR spectra and vice versa. A pseudo-mutual exclusion rule seems to be operative for the cyanine vibrational spectra in the 1600-1300 cm -1 region, indicating that the central conjugated systems of the cyanines have nearly symmetrical structure, i.e. the extended all-trans forms of the methine chains and the bond orders of 1.5 of the CC and CN bonds in both the solution and solid states. The IR spectra of 3-ethyl-2-[3-(3-ethyl-2-benzothiazolinylidene)-1-propenyl]benzothiazolium iodide (NK-76) and 3-ethyl-2-[7-(3-ethyl-2-benzothiazolinylidene)-1,3,5-heptatrienyl]benzothiazolium iodide (NK-126) change little between the solid and solution states while those of 3-octadecyl-2-[3-(3-octadecyl-2-benzothiazolinylidene)-1-propenyl]benzothiazolium iodide (NK-2560) and 3-octadecyl-2-[7-(3-octadecyl-2-benzothiazolinylidene)-1,3,5-heptatrienyl]benzothiazolium perchlorate (NK-2861) alter significantly between the two states in the frequencies of bands due to the stretching modes of their central conjugated systems. The results suggest that the electronic states of the central conjugated systems of NK-2560 and NK-2861 undergo appreciable changes on going from the solid to the solution states.

  11. Intramolecular hydrogen bonding and excited state proton transfer in hydroxyanthraquinones as studied by electronic spectra, resonance Raman scattering, and transform analysis

    NASA Astrophysics Data System (ADS)

    Marzocchi, Mario P.; Mantini, Anna R.; Casu, Maurizio; Smulevich, Giulietta

    1998-01-01

    The scheme of energy levels previously proposed to describe dual excitation and emission associated to excited state intramolecular proton transfer (ESIPT) of some hydroxyanthraquinones (HAQ's) has been made more quantitative in the present paper. The zero-point energy and the frequency of the νOH mode for the HAQ's have been calculated on the basis of the Lippincott-Schroeder double-minimum potential for the O-H⋯O hydrogen bond. The second derivative absorption (D2) spectra show that the vibrational structures of the electronic excited state of HAQ's giving rise to ESIPT are characterized by the progression of the νOH stretching mode. The νOH mode in the ground state is observed as a very strong band in the vibrational structure of the short wavelength emission for HAQ's showing ESIPT. The combined resonance Raman band assignment of four hydroxyanthraquinones and transform analysis show that the visible transition involves the hydrogen bonded cycle and induces proton transfer in the excited state in most cases. On the basis of the isotopic effects, some vibrations of the hydrogen bonded cycle, namely the νC=O, δC=O, νCOH, and δOH modes, have been identified. The transform method, including the combined analysis of the absorption and D2 spectra in terms of sum-over-states, was checked by directly deriving the displacement parameters (Franck-Condon factors) of 1,4-DHAQ from the high resolution free-jet spectrum. The values of the displacement parameters of the νOH mode are quite large for the HAQ's showing ESIPT, while are negligible for 1,4-DHAQ. High values of the displacement parameters for the other vibrations of the hydrogen bonded cycle were found for all HAQ's.

  12. Near-field enhanced ultraviolet resonance Raman spectroscopy using aluminum bow-tie nano-antenna

    PubMed Central

    Li, Ling; Fang Lim, Shuang; Puretzky, Alexander A.; Riehn, Robert; Hallen, H. D.

    2012-01-01

    An aluminum bow-tie nano-antenna is combined with the resonance Raman effect 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-field Raman peaks for several strong infrared modes. We achieve a gain of ∼105 in signal intensity from the near field 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. PMID:23066168

  13. 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.

  14. Applications of ultraviolet resonance raman spectroscopy to proteins

    NASA Astrophysics Data System (ADS)

    Spiro, Thomas G.; Grygon, Christine A.

    Recent developments in instrumentation for ultraviolet resonance Raman (UVRR) spectroscopy and its application to proteins are reviewed. With excitation near the ˜ 195 nm amide π-π* transition strong enhancement is seen of the amide vibrational modes, particularly amide II, whose intensity is sensitive to secondary structure. With measurements at 200 and 192 nm one can calculate the fractions of α-helix, β sheet and unordered segments from the known cross sections of these structures. The proline imide II band at ˜ 1460 cm -1 is strongly enhanced with 218 nm excitation and its frequency can be used to monitor cis-trans isomerization. Aromatic residues give rise to strong UVRR bands. Phenylalanine (Phe) and tyrosine (Tyr) show scattering patterns typical of substituted benzenes: enhancement of vibronic modes, especially ν 8a and ν 8b in resonance with the quasi-forbidden L a transition (˜ 205 and ˜ 223 nm for Phe and Tyr), and of breathing modes in resonance with the allowed B a,b transitions (˜ 188 and ˜ 193 nm for Phe and Tyr). Tyrosine, and especially tyrosinate, also show strong enhancement of ν 8a and ν 8b in the B a,b-resonant region, behavior attributed to electronic mixing of L a with B a via the OH (or O -) substituent. In proteins the Tyr ν 8a and ν 8b bands are most readily observed with 229 nm excitation, where the Phe contributions are minimal. The ν 8b frequency is sensitive to Tyr H-bonding and has been calibrated in terms of the H-bond strength. The Tyr 830/850 cm -1 Fermi doublet intensity ratio, which can be monitored at 200 nm is sensitive to H-bonding, but also to other environmental influences. With 218 nm excitation protein spectra are dominated by tryptophan (Trp) contributions. The 1340/1360 cm -1 Trp Fermi doublet is sensitive to solvent exposure, while the ˜ 880 cm -1 band frequency is sensitive to H-bonding. Histidine (His) excitation profiles show π-π* resonances at ˜ 218 and ˜ 204 nm. The UVRR bands are sensitive to

  15. 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.

  16. Resonance Raman examination of the wavelength regulation mechanism in human visual pigments.

    PubMed

    Kochendoerfer, G G; Wang, Z; Oprian, D D; Mathies, R A

    1997-06-03

    Resonance Raman spectra of recombinant human green and red cone pigments have been obtained to examine the molecular mechanism of color recognition by visual pigments. Spectra were acquired using a 77 K resonance Raman microprobe or preresonance Raman spectroscopy. The vibrational bands were assigned by comparison to the spectra of bovine rhodopsin and model compounds. The C=NH stretching frequencies of rhodopsin, the green cone pigment, and the red cone pigment in H2O (D2O) are found at 1656 (1623), 1640 (1618), and 1644 cm(-1), respectively. Together with previous resonance Raman studies on iodopsin [Lin, S. W., Imamoto, Y., Fukada, Y., Shichida, Y., Yoshizawa, T., & Mathies, R. A. (1994) Biochemistry 33, 2151-2160], these values suggest that red and green pigments have very similar Schiff base environments, while the Schiff base group in rhodopsin is more strongly hydrogen-bonded to its protein environment. The absence of significant frequency and intensity differences of modes in the fingerprint and the hydrogen out-of-plane wagging regions for all these pigments does not support the hypothesis that local chromophore interactions with charged protein residues and/or chromophore planarization are crucial for the absorption differences among these pigments. However, our data are consistent with the idea that the Schiff base group in blue visual pigments is stabilized by protein and water dipoles and that the removal of this dipolar field shifts the absorption maximum from blue to green. A further red shift of the lambda(max) from the green to the red pigment is successfully modeled by the addition of hydroxyl-bearing amino acids (Ser164, Tyr261, and Thr269) close to the ionone ring that lower the transition energy by interacting with the change of dipole moment of the chromophore upon excitation. The increased hydrogen bonding of the protonated Schiff base group in rhodopsin is predicted to account for the 30 nm blue shift of its absorption maximum compared to

  17. UV resonance Raman investigation of the aqueous solvation dependence of primary amide vibrations.

    PubMed

    Punihaole, David; Jakubek, Ryan S; Dahlburg, Elizabeth M; Hong, Zhenmin; Myshakina, Nataliya S; Geib, Steven; Asher, Sanford A

    2015-03-12

    We investigated the normal mode composition and the aqueous solvation dependence of the primary amide vibrations of propanamide. Infrared, normal Raman, and UV resonance Raman (UVRR) spectroscopy were applied in conjunction with density functional theory (DFT) to assign the vibrations of crystalline propanamide. We examined the aqueous solvation dependence of the primary amide UVRR bands by measuring spectra in different acetonitrile/water mixtures. As previously observed in the UVRR spectra of N-methylacetamide, all of the resonance enhanced primary amide bands, except for the Amide I (AmI), show increased UVRR cross sections as the solvent becomes water-rich. These spectral trends are rationalized by a model wherein the hydrogen bonding and the high dielectric constant of water stabilizes the ground state dipolar (-)O-C═NH2(+) resonance structure over the neutral O═C-NH2 resonance structure. Thus, vibrations with large C-N stretching show increased UVRR cross sections because the C-N displacement between the electronic ground and excited state increases along the C-N bond. In contrast, vibrations dominated by C═O stretching, such as the AmI, show a decreased displacement between the electronic ground and excited state, which result in a decreased UVRR cross section upon aqueous solvation. The UVRR primary amide vibrations can be used as sensitive spectroscopic markers to study the local dielectric constant and hydrogen bonding environments of the primary amide side chains of glutamine (Gln) and asparagine (Asn).

  18. Study and application of new Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Liu, Qiushi; Zhang, Xiaohua

    2016-03-01

    Spatially Offset Raman Spectroscopy (SORS) is a new type of Raman Spectroscopy technology, which can detect the medium concealed in the opaque or sub-transparent material fast and nondestructively. The article summarized Spatially Offset Raman Spectroscopy`s international and domestic study and application progress on contraband detecting, medical science (bone ingredient, cancer diagnose etc.), agricultural products, historical relic identification etc. and stated the technology would become an effective measurement which had wide application prospect.

  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. 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.

  1. Resonance Raman spectra of the anion and cation radicals of bacterial photosynthetic pigments

    SciTech Connect

    Diers, J.R.; Bocian, D.F. )

    1994-12-08

    Resonance Raman (RR) spectra are reported for the radical ions of the bacterial photosynthetic pigments bacteriochlorophyll a (BCh) and its metal-free analog bacteriopheophytin a (BPh). The radical anions, BCh[sup [minus

  2. Evidence for a bound water molecule next to the retinal Schiff base in bacteriorhodopsin and rhodopsin: a resonance Raman study of the Schiff base hydrogen/deuterium exchange.

    PubMed Central

    Deng, H.; Huang, L.; Callender, R.; Ebrey, T.

    1994-01-01

    The retinal chromophores of both rhodopsin and bacteriorhodopsin are bound to their apoproteins via a protonated Schiff base. We have employed continuous-flow resonance Raman experiments on both pigments to determine that the exchange of a deuteron on the Schiff base with a proton is very fast, with half-times of 6.9 +/- 0.9 and 1.3 +/- 0.3 ms for rhodopsin and bacteriorhodopsin, respectively. When these results are analyzed using standard hydrogen-deuteron exchange mechanisms, i.e., acid-, base-, or water-catalyzed schemes, it is found that none of these can explain the experimental results. Because the exchange rates are found to be independent of pH, the deuterium-hydrogen exchange can not be hydroxyl (or acid-)-catalyzed. Moreover, the deuterium-hydrogen exchange of the retinal Schiff base cannot be catalyzed by water acting as a base because in that case the estimated exchange rate is predicted to be orders of magnitude slower than that observed. The relatively slow calculated exchange rates are essentially due to the high pKa values of the Schiff base in both rhodopsin (pKa > 17) and bacteriorhodopsin (pKa approximately 13.5). We have also measured the deuterium-hydrogen exchange of a protonated Schiff base model compound in aqueous solution. Its exchange characteristics, in contrast to the Schiff bases of the pigments, is pH-dependent and consistent with the standard base-catalyzed schemes. Remarkably, the water-catalyzed exchange, which has a half-time of 16 +/- 2 ms and which dominates at pH 3.0 and below, is slower than the exchange rate of the Schiff base in rhodopsin and bacteriorhodopsin. Thus, there are two anomalous results, the inconsistency of the observed hydrogen exchange rates of retinal Schiff base in the two pigments with those predicted from the standard exchange schemes and the enhancement of the rate of hydrogen exchange in the two proteins over the model Schiff base in aqueous solution. We suggest that these results are explained by the

  3. 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.

  4. 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.

  5. Resonant Raman Scattering from Bound Magnetorotons in the Fractional Quantum Hall Regime

    NASA Astrophysics Data System (ADS)

    He, Song

    1996-03-01

    We investigate excitation spectra of a fractional quantum Hall system at ν=1/3 using both theoretical and experimental techniques. Using finite-size numerical diagonalizations, we have studied systematically the excitation spectra, the nature of the low-lying excited states, and the density response function of a ν=1/3 system. Our numerical results indicate that two rotons at the roton minimum can form a weakly bound composite object, giving rise to excited states below the collective mode at long wavelengths. We argue that only these two roton composite objects contribute to the resonant Raman scattering at low momentum transfers. Using the experimental technique of resonant Raman scattering, we have identified the contributions to the Raman intensity from the internal excitations of the fractional quantum Hall system by studying their dependence on the incoming light energy, the filling factor, and the temperature. As a function of the energy shift, the Raman intensity shows a sharp peak at an energy shift of about twice of the energy gap at the roton minimum. We propose that this sharp peak is related to a two roton bound state. The sharp peak is followed by a broader peak, which we think is related to the two-roton continuum. When a grating pattern is put on the sample so that small but finite momentum transfer can be achieved, we observed another peak at about twice of the energy gap Δ_q=∞. We suspect this peak is related to the collective mode at long wavelength. Finally, we propose an excitation spectra consistent with our numerical and experimental results. * This work is a collaboration with P. M. Platzman, A. Pinczuk, B. S. Dennis, L. L. Sohn, L. N. Pfeiffer, and K. W. West.

  6. 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…

  7. 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…

  8. 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.

  9. Identifying the Elusive Framework Niobium in NbS-1 Zeolite by UV Resonance Raman.

    PubMed

    Chen, Yong; Wang, Xinping; Zhang, Lejian

    2017-09-14

    It was found that bands at 739, 963 and 1107 cm-1 in resonant Raman spectra are characteristics of framework penta-coordinated NbV-OH species, and that band at 1336 cm-1 in UV Raman spectra excited by 320 nm is a sensitive detector to identify extraframework niobium species. The change of framework penta-coordinated NbV-OH species into Nb+ and NbO- species due to dehydration was definitively confirmed based on UV resonance Raman and UV/Vis results. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Definitive evidence for linked resonances in surface-enhanced Raman scattering: Excitation profile of Cu phthalocyanine

    NASA Astrophysics Data System (ADS)

    . Londero, Pablo S.; Leona, Marco; Lombardi, John R.

    2013-03-01

    We have characterized the surface-enhanced Raman spectroscopy (SERS) spectrum of copper phthalocyanine as a function of excitation wavelength in the 435-635 nm region using a tunable excitation Raman system. We show that the Raman excitation spectrum within the surface plasmon resonance is dominated by totally symmetric modes in the blue and non-totally symmetric modes in the red. The findings are compared to our recent theoretical work on the nature of SERS enhancement. The experimental results are interpreted to be a consequence of vibronically coupled intensity borrowing by charge transfer resonances from allowed molecular transitions, enhancing non-totally symmetric modes.

  11. Study of virus by Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Moor, K.; Kitamura, H.; Hashimoto, K.; Sawa, M.; Andriana, B. B.; Ohtani, K.; Yagura, T.; Sato, H.

    2013-02-01

    Problem of viruses is very actual for nowadays. Some viruses, which are responsible for human of all tumors, are about 15 %. Main purposes this study, early detection virus in live cell without labeling and in the real time by Raman spectroscopy. Micro Raman spectroscopy (mRs) is a technique that uses a Raman spectrometer to measure the spectra of microscopic samples. According to the Raman spectroscopy, it becomes possible to study the metabolites of a live cultured cell without labeling. We used mRs to detect the virus via HEK 293 cell line-infected adenovirus. We obtained raman specters of lives cells with viruses in 24 hours and 7 days after the infection. As the result, there is some biochemical changing after the treatment of cell with virus. One of biochemical alteration is at 1081 cm-1. For the clarification result, we use confocal fluorescent microscopy and transmission electron microscopy (TEM).

  12. Resonant raman scattering in complexes of nc-Si/SiO2 quantum dots and oligonucleotides

    NASA Astrophysics Data System (ADS)

    Bairamov, F. B.; Poloskin, E. D.; Kornev, A. A.; Chernev, A. L.; Toporov, V. V.; Dubina, M. V.; Röder, C.; Sprung, C.; Lipsanen, H.; Bairamov, B. Kh.

    2014-11-01

    We report on the functionalization of nanocrystalline nc-Si/SiO2 semiconductor quantum dots (QDs) by short d(20G, 20T) oligonucleotides. The obtained complexes have been studied by Raman spectroscopy techniques with high spectral and spatial resolution. A new phenomenon of multiband resonant light scattering on single oligonucleotide molecules has been discovered, and peculiarities of this effect related to the nonradiative transfer of photoexcitation from nc-Si/SiO2 quantum dots to d(20G, 20T) oligonucleotide molecules have been revealed.

  13. 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.

  14. 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

  15. 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.

  16. 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

    2015-07-07

    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.

  17. Raman-like resonant secondary emission causes valley coherence in CVD-grown monolayer Mo S2

    NASA Astrophysics Data System (ADS)

    Yoshikawa, Naotaka; Tani, Shuntaro; Tanaka, Koichiro

    2017-03-01

    Monolayer transition metal dichalcogenides are promising materials for "valleytronics." They have band gaps at energy-degenerate K and K' valleys with opposite spins. Due to the lack of inversion symmetry, electron-hole pairs can be selectively created at K or K' valleys by circularly polarized photons. In addition, linearly polarized light excitation creates the coherent superposition of exciton valley states, referred to as the generation of valley coherence. In this study we performed polarization resolved photoluminescence and resonant Raman spectroscopy of CVD-grown monolayer Mo S2 . We found that the lowest exciton photoluminescence becomes polarized, indicating the effective generation of valley polarization and valley coherence due to the resonant effect, accompanied by a drastic change of the polarization selection rule of Raman scattering. These results were theoretically explained from the viewpoint of the selection rules of resonant Raman scattering. We conclude that the Raman-like resonant second-order optical process should be the main mechanism of valley coherence.

  18. Investigating the phase-dependent photochemical reaction dynamics of chlorine dioxide using resonance Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Hayes, Sophia C.; Wallace, Paul M.; Bolinger, Josh C.; Reid, Philip J.

    Recent progress in understanding the phase-dependent reactivity demonstrated by halooxides is outlined. Specifically, resonance Raman intensity analysis (RRIA) and time-resolved resonance Raman (TRRR) studies of chlorine dioxide (OClO) photochemistry in solution are presented. Using RRIA, it has been determined that the excited-state structural evolution that occurs along the asymmetric-stretch coordinate in the gas phase is restricted in solution. The absence of evolution along this coordinate results in the preservation of groundstate symmetry in the excited state. The role of symmetry in defining the reaction coordinate and the solvent-solute interactions responsible for modification of the excited-state potential energy surface are discussed. TRRR studies are presented which demonstrate that geminate recombination of the primary photoproducts resulting in the reformation of ground-state OClO is a central feature of OClO photochemistry in solution. These studies also demonstrate that a fraction of photoexcited OClO undergoes photoisomerization to form ClOO, with the ground-state thermal decomposition of this species resulting in Cl production on the subnanosecond timescale. Finally, time-resolved anti-Stokes experiments are presented which demonstrate that the OClO vibrational-relaxation dynamics are solvent dependent. The current picture of OClO photochemistry derived from these studies is discussed, and future directions for study are outlined.

  19. 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…

  20. 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…

  1. Surface-enhanced resonance Raman scattering (SERRS) simulates PCR for sensitive DNA detection.

    PubMed

    Zhou, Haibo; Lin, Shenyu; Nie, Yichu; Yang, Danting; Wang, Qiqin; Chen, Weijia; Huang, Ning; Jiang, Zhengjin; Chen, Shanze

    2015-11-21

    This paper describes a novel double-stranded DNA detection method through resonance between SYBR Green I and DNA with the surface-enhanced resonance Raman scattering (SERRS) assay, which opens an avenue to the quantitative and reliable application of SERRS in DNA detection.

  2. 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).

  3. Identification of heme propionate vibrational modes in the resonance Raman spectra of cytochrome c oxidase.

    PubMed

    Egawa, Tsuyoshi; Lee, Hyun Ju; Ji, Hong; Gennis, Robert B; Yeh, Syun-Ru; Rousseau, Denis L

    2009-11-01

    The propionate groups of heme a and a(3) in cytochrome c oxidase (CcO) have been postulated to mediate both the electron and proton transfer within the enzyme. To establish structural markers for the propionate groups, their associated vibrational modes were identified in the resonance Raman spectra of CcO from bovine (bCcO) and Rhodobacter sphaeroides (RsCcO). The distinction between the modes from the propionates of heme a and heme a(3), as well as those from the propionates on the pyrrole rings A and D in each heme, was made on the basis of H2O-D2O isotope substitution experiments combined with wavelength-selective resonance enhancement (for bCcO) or mutagenesis studies (for RsCcO).

  4. Resonant L{sub II,III} x-ray Raman scattering from HCl

    SciTech Connect

    Saathe, C.; Rubensson, J.-E.; Nordgren, J.; Guimaraes, F. F.; Agui, A.; Guo, J.; Ekstroem, U.; Norman, P.; Gel'mukhanov, F.; Aagren, H.

    2006-12-15

    We have studied the spectral features of Cl L{sub II,III} resonant x-ray Raman scattering of HCl molecules in gas phase both experimentally and theoretically. The theory, formulated in the intermediate-coupling scheme, takes into account the spin-orbital and molecular-field splittings in the Cl 2p shells, as well as the Coulomb interaction of the core hole with unoccupied molecular orbitals. Experiment and theory display nondispersive dissociative peaks formed by decay transitions in both molecular and dissociative regions. The molecular and atomic peaks collapse in a single narrow resonance because the dissociative potentials of core-excited and final states are parallel to each other along the whole pathway of the nuclear wave packet.

  5. 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.

  6. Studies on sensitive Raman gas detectors

    NASA Astrophysics Data System (ADS)

    Zuo, Duluo; Xu, Yongyue; Wang, Xinbing; Xiong, Youhui

    2013-05-01

    Recent studies on signal enhancement of spontaneous Raman scattering for developing of sensitive Raman gas detectors are reported. Raman scattering is a gas detecting method with high feasibility, but usually its signal is very low. To improve the level and the quality of the Raman signal, the effects of pumping laser source, sample cell, and optical arrangement are studied in detail. It is found that not only the wall of sample cell will give a wide Raman or fluorescence background which will decrease the sensitivity, but the dichroic beam splitter will also contribute considerable background if it is not aligned properly. The sample cell of hollow fiber is characterized by its high responsibility as well as its high background and low signal contrast. When the hollow fiber is replaced by a free-space sample cell consisted of metal-coated parabolic reflector, the wide background is largely suppressed. If there is no common optical elements between the pumping and collecting optical systems, the wide background will be cut down obviously, which is proved by the intracavity-enhanced Raman scattering in a He-Ne laser. These experimental results will be helpful for the research and developing of highly sensitive Raman gas detectors.

  7. Quantum-mechanical calculation of the intensity distribution in Raman and resonance Raman spectra of a phenylalanine aqueous solution

    NASA Astrophysics Data System (ADS)

    Burova, T. G.; Shcherbakov, R. S.

    2017-03-01

    Quantum-mechanical calculations of the intensity distribution in the resonance Raman spectrum of an aqueous solution of phenylalanine, excited by light with wavelengths of 193, 204, 218, and 235 nm, and in the nonresonant Raman spectrum excited at a wavelength of 488 nm have been performed. The calculation results are in satisfactory agreement with the experimental data in the literature. Spectral lines characteristic of phenylalanine are observed, which can be used as markers when analyzing the peptide structure. It is noted that the contribution of highly excited electronic states (spaced by less than 10 eV from the resonant lines) to the scattering tensor components must be taken into account. The important role of the Herzberg-Teller effect in the description of spectral intensity distribution is demonstrated.

  8. Resonant Raman scattering in single crystal of congruent LiTaO 3 : Effect of excitation energy

    NASA Astrophysics Data System (ADS)

    Bhaumik, Indranil; Kumar, Shailendra; Ganesamoorthy, S.; Bhatt, R.; Karnal, A. K.; Raja Sekhar, B. N.

    2011-12-01

    Large dispersion in the peak position of the OH - stretching mode (˜687.9 and ˜2167.7 cm -1/eV for fundamental and 3rd harmonic, respectively) is observed by Resonance Raman studies in congruent lithium tantalate single crystal under varying excitation energies. This is explained by considering the involvement of multiple LO phonons in the interaction with OH - stretching vibration and the resonantly excited electrons. The intensity of the peaks is also found to vary with the excitation energy. FWHM increases with the increase in excitation energy because of individual contributions of the increasing number of resonance steps to the broadening.

  9. [Raman spectrum study on turquoise].

    PubMed

    Chen, Quan-Li; Qi, Li-Jian; Chen, Jing-Zhong

    2009-02-01

    The Raman spectrum has been employed to discuss the explanation of the structure of water and the vibration of [PO4(3-)] tetrahedron of the turquoise from Hubei and Anhui province. The Raman spectra are resulted mainly from vibrations of water, hydroxyl units and [PO4(3-)] tetrahedron of turquoise. The 3 510-3 440 cm(-1) bands with the main Raman spectra peak at 3 470 cm(-1) were assigned to the upsilon(OH) stretching vibrations and the 3 290-3 070 cm(-1) bands assigned to the upsilon(H2O) stretching vibrations. The bands observed at 1 200-1 030 cm(-1) with the strong peak at 1 039 cm(-1) were assigned to upsilon3 (PO4) antisymmetric stretching vibrations. And the Raman spectra peaks at 650-540 cm(-1) and 500-410 cm(-1) were attributed to the upsilon4 and upsilon2 bending vibrations of [PO4(3-)] tetrahedron, respectively. The spectra of the turquoise from different localities are basically similar and subtly different.

  10. Carotenoid analysis of halophilic archaea by resonance Raman spectroscopy.

    PubMed

    Marshall, Craig P; Leuko, Stefan; Coyle, Candace M; Walter, Malcolm R; Burns, Brendan P; Neilan, Brett A

    2007-08-01

    Recently, halite and sulfate evaporate rocks have been discovered on Mars by the NASA rovers, Spirit and Opportunity. It is reasonable to propose that halophilic microorganisms could have potentially flourished in these settings. If so, biomolecules found in microorganisms adapted to high salinity and basic pH environments on Earth may be reliable biomarkers for detecting life on Mars. Therefore, we investigated the potential of Resonance Raman (RR) spectroscopy to detect biomarkers derived from microorganisms adapted to hypersaline environments. RR spectra were acquired using 488.0 and 514.5 nm excitation from a variety of halophilic archaea, including Halobacterium salinarum NRC-1, Halococcus morrhuae, and Natrinema pallidum. It was clearly demonstrated that RR spectra enhance the chromophore carotenoid molecules in the cell membrane with respect to the various protein and lipid cellular components. RR spectra acquired from all halophilic archaea investigated contained major features at approximately 1000, 1152, and 1505 cm(-1). The bands at 1505 cm(-1) and 1152 cm(-1) are due to in-phase C=C (nu(1) ) and C-C stretching ( nu(2) ) vibrations of the polyene chain in carotenoids. Additionally, in-plane rocking modes of CH(3) groups attached to the polyene chain coupled with C-C bonds occur in the 1000 cm(-1) region. We also investigated the RR spectral differences between bacterioruberin and bacteriorhodopsin as another potential biomarker for hypersaline environments. By comparison, the RR spectrum acquired from bacteriorhodopsin is much more complex and contains modes that can be divided into four groups: the C=C stretches (1600-1500 cm(-1)), the CCH in-plane rocks (1400-1250 cm(-1)), the C-C stretches (1250-1100 cm(-1)), and the hydrogen out-of-plane wags (1000-700 cm(-1)). RR spectroscopy was shown to be a useful tool for the analysis and remote in situ detection of carotenoids from halophilic archaea without the need for large sample sizes and complicated

  11. Carotenoid Analysis of Halophilic Archaea by Resonance Raman Spectroscopy

    NASA Astrophysics Data System (ADS)

    Marshall, Craig P.; Leuko, Stefan; Coyle, Candace M.; Walter, Malcolm R.; Burns, Brendan P.; Neilan, Brett A.

    2007-08-01

    Recently, halite and sulfate evaporate rocks have been discovered on Mars by the NASA rovers, Spirit and Opportunity. It is reasonable to propose that halophilic microorganisms could have potentially flourished in these settings. If so, biomolecules found in microorganisms adapted to high salinity and basic pH environments on Earth may be reliable biomarkers for detecting life on Mars. Therefore, we investigated the potential of Resonance Raman (RR) spectroscopy to detect biomarkers derived from microorganisms adapted to hypersaline environments. RR spectra were acquired using 488.0 and 514.5 nm excitation from a variety of halophilic archaea, including Halobacterium salinarum NRC-1, Halococcus morrhuae, and Natrinema pallidum. It was clearly demonstrated that RR spectra enhance the chromophore carotenoid molecules in the cell membrane with respect to the various protein and lipid cellular components. RR spectra acquired from all halophilic archaea investigated contained major features at approximately 1000, 1152, and 1505 cm-1. The bands at 1505 cm-1 and 1152 cm-1 are due to in-phase C=C (ν1 ) and C-C stretching ( ν2 ) vibrations of the polyene chain in carotenoids. Additionally, in-plane rocking modes of CH3 groups attached to the polyene chain coupled with C-C bonds occur in the 1000 cm-1 region. We also investigated the RR spectral differences between bacterioruberin and bacteriorhodopsin as another potential biomarker for hypersaline environments. By comparison, the RR spectrum acquired from bacteriorhodopsin is much more complex and contains modes that can be divided into four groups: the C=C stretches (1600-1500 cm-1), the CCH in-plane rocks (1400-1250 cm-1), the C-C stretches (1250-1100 cm-1), and the hydrogen out-of-plane wags (1000-700 cm-1). RR spectroscopy was shown to be a useful tool for the analysis and remote in situ detection of carotenoids from halophilic archaea without the need for large sample sizes and complicated extractions, which are

  12. Resonance Raman scattering from Cd1-xZnxS nanoparticles dispersed in oxide glass

    NASA Astrophysics Data System (ADS)

    Arora, Akhilesh K.; Rajalakshmi, M.

    2000-11-01

    Resonance Raman scattering from 1 and 2 LO phonons is investigated from Cd1-xZnxS nanoparticles dispersed in oxide glass before and after annealing. The resonance profiles are found to exhibit asymmetry which is attributed to the interference effects arising from a nonresonant contribution to the polarizability. The energies of the resonances are found to be consistent with the direct interband transition energies estimated from the reported optical data.

  13. [Raman scattering study of DL-alanine].

    PubMed

    Gong, Yan; Wang, Wen-qing

    2006-01-01

    Studies of Raman vibration spectra are useful to obtaining information on biomolecular crystals. The cell dimensions of the L- and DL-alanine crystals are nearly identical, and both structures belong to the orthorhombic system, but the space group is P2(1) 2(1) 2(1) for the L-isomer, and Pna2(1) for the racemate crystal. The Raman spectrum of L-alanine has been measured by many authors. The present work is focusing on the Raman scattering study of DL-alanine powder. Based on the analysis of the differences between DL-alanine and L-alanine Raman spectra, the authors obtained indispensable information on hydrogen bond and the motion of the molecular conformation in alanine crystals.

  14. 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.

  15. Direct excitation of microwave-spin dressed states using a laser-excited resonance Raman interaction

    NASA Astrophysics Data System (ADS)

    Shahriar, M. S.; Hemmer, P. R.

    1990-10-01

    We have used a laser-induced resonance Raman transition between the ground-state hyperfine sublevels in a sodium atomic beam to excite individual dressed states of the microwave-spin hyperfine transition. In addition, we have used the microwave interaction to excite the Raman trapped state. Extension of this technique to mm waves or to the far infrared may lead to applications such as mm-wave-beam steering and holographic image conversion.

  16. Resonance Raman Spectroscopy of human brain metastasis of lung cancer analyzed by blind source separation

    NASA Astrophysics Data System (ADS)

    Zhou, Yan; Liu, Cheng-Hui; Pu, Yang; Cheng, Gangge; Yu, Xinguang; Zhou, Lixin; Lin, Dongmei; Zhu, Ke; Alfano, Robert R.

    2017-02-01

    Resonance Raman (RR) spectroscopy offers a novel Optical Biopsy method in cancer discrimination by a means of enhancement in Raman scattering. It is widely acknowledged that the RR spectrum of tissue is a superposition of spectra of various key building block molecules. In this study, the Resonance Raman (RR) spectra of human metastasis of lung cancerous and normal brain tissues excited by a visible selected wavelength at 532 nm are used to explore spectral changes caused by the tumor evolution. The potential application of RR spectra human brain metastasis of lung cancer was investigated by Blind Source Separation such as Principal Component Analysis (PCA). PCA is a statistical procedure that uses an orthogonal transformation to convert a set of observations of possibly correlated variables into a set of values of linearly uncorrelated variables called principal components (PCs). The results show significant RR spectra difference between human metastasis of lung cancerous and normal brain tissues analyzed by PCA. To evaluate the efficacy of for cancer detection, a linear discriminant analysis (LDA) classifier is utilized to calculate the sensitivity, and specificity and the receiver operating characteristic (ROC) curves are used to evaluate the performance of this criterion. Excellent sensitivity of 0.97, specificity (close to 1.00) and the Area Under ROC Curve (AUC) of 0.99 values are achieved under best optimal circumstance. This research demonstrates that RR spectroscopy is effective for detecting changes of tissues due to the development of brain metastasis of lung cancer. RR spectroscopy analyzed by blind source separation may have potential to be a new armamentarium.

  17. Performance comparison of single and dual-excitation-wavelength resonance-Raman explosives detectors

    NASA Astrophysics Data System (ADS)

    Yellampalle, Balakishore; Martin, Robert; Witt, Kenneth; McCormick, William; Wu, Hai-Shan; Sluch, Mikhail; Ice, Robert; Lemoff, Brian

    2017-05-01

    Deep-ultraviolet Raman spectroscopy is a very useful approach for standoff detection of explosive traces. Using two simultaneous excitation wavelengths improves the specificity and sensitivity to standoff explosive detection. The High Technology Foundation developed a highly compact prototype of resonance Raman explosives detector. In this work, we discuss the relative performance of a dual-excitation sensor compared to a single-excitation sensor. We present trade space analysis comparing three representative Raman systems with similar size, weight, and power. The analysis takes into account, cost, spectral resolution, detection/identification time and the overall system benefit.

  18. Resonance Raman microspectroscopy of myeloperoxidase and cytochrome b558 in human neutrophilic granulocytes.

    PubMed Central

    Sijtsema, N M; Otto, C; Segers-Nolten, G M; Verhoeven, A J; Greve, J

    1998-01-01

    With (resonance) Raman microscospectroscopy, it is possible to investigate the chemical constitution of a very small volume (0.5 fl) in a living cell. We have measured resonance Raman spectra in the cytoplasm of living normal, myeloperoxidase (MPO)-deficient, and cytochrome b558-deficient neutrophils and in isolated specific and azurophilic granule fractions, using an excitation wavelength of 413.1 nm. Similar experiments were performed after reduction of the redox centers by the addition of sodium dithionite. The specific and azurophilic granules in both redox states appeared to have clearly distinguishable Raman spectra when exciting at a wavelength of 413.1 nm. The azurophilic granules and the cytochrome b558-deficient neutrophils showed Raman spectra similar to that of the isolated MPO. The spectra of the specific granules and the MPO-deficient neutrophils corresponded very well to published cytochrome b558 spectra. The resonance Raman spectrum of the cytoplasmic region of normal neutrophilic granulocytes could be fitted with a combination of the spectra of the specific and azurophilic granules, which shows that the Raman signal of neutrophilic granulocytes mainly originates from MPO and cytochrome b558, at an excitation wavelength of 413.1 nm. PMID:9635778

  19. Raman spectroscopic studies on bacteria

    NASA Astrophysics Data System (ADS)

    Maquelin, Kees; Choo-Smith, Lin-P'ing; Endtz, Hubert P.; Bruining, Hajo A.; Puppels, Gerwin J.

    2000-11-01

    Routine clinical microbiological identification of pathogenic micro-organisms is largely based on nutritional and biochemical tests. Laboratory results can be presented to a clinician after 2 - 3 days for most clinically relevant micro- organisms. Most of this time is required to obtain pure cultures and enough biomass for the tests to be performed. In the case of severely ill patients, this unavoidable time delay associated with such identification procedures can be fatal. A novel identification method based on confocal Raman microspectroscopy will be presented. With this method it is possible to obtain Raman spectra directly from microbial microcolonies on the solid culture medium, which have developed after only 6 hours of culturing for most commonly encountered organisms. Not only does this technique enable rapid (same day) identifications, but also preserves the sample allowing it to be double-checked with traditional tests. This, combined with the speed and minimal sample handling indicate that confocal Raman microspectroscopy has much potential as a powerful new tool in clinical diagnostic microbiology.

  20. 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.

  1. NONLINEAR OPTICS: Stimulated resonant hyper-Raman scattering of light by polaritons in alkali metal vapors

    NASA Astrophysics Data System (ADS)

    Galaĭchuk, Yu A.; Yashkir, Yu N.

    1989-12-01

    A theory is developed for the calculation of the gain g due to stimulated resonant hyper-Raman scattering of light by polaritons in gaseous media. It is shown that throughout the tuning range of the pump frequency (including one- and two-photon resonances) a maximum of g corresponds to a dispersion curve of polaritons plotted ignoring attenuation. Theoretical results are used to analyze characteristics of hyper-Raman scattering in sodium vapor. It is shown that under normal experimental conditions the splitting of polariton branches is considerable (amounting to tens of reciprocal centimeters on the frequency scale and several angular degrees). The value of g is estimated for two-photon resonances in the case when the pump frequency is tunable in a wide range. The optimal conditions for stimulated hyper-Raman scattering are identified.

  2. Resonance Raman Spectra of Hemoglobin and Cytochrome c: Inverse Polarization and Vibronic Scattering

    PubMed Central

    Spiro, Thomas G.; Strekas, Thomas C.

    1972-01-01

    Resonance Raman spectra of hemoglobin and cytochrome c in dilute solution contain prominent bands that exhibit inverse polarization, i.e., the polarization vector of the incident radiation is rotated through 90° for 90° scattering, giving infinite depolarization ratios. This phenomenon is shown to require an antisymmetric molecular-scattering tensor. The antisymmetry, which is characteristic of resonance scattering, is associated with the form of a particular class of vibrations, A20, of the tetragonal heme chromophores. The dependence of the resonance Raman spectra on the wavelength of the exciting radiation, as well as their polarization properties, demonstrates that the prominent bands correspond to vibronically active modes of the first electronic transition of the heme proteins, and provide confirmation of Albrecht's vibronic theory of Raman intensities. PMID:4506783

  3. Multiwavelength Resonance Raman Characterization of the Effect of Growth Phase and Culture Medium on Bacteria.

    PubMed

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

    2015-08-01

    We examine the use of multiwavelength ultraviolet (UV) resonance-Raman signatures to identify the effects of growth phase and growth medium on gram-positive and gram-negative bacteria. Escherichia coli (E. coli), Citrobacter koseri (C. koseri), Citrobacter braakii (C. braakii), and Bacillus cereus (B. cereus) were grown to logarithmic and stationary phases in nutrient broth and brain heart infusion broth. Resonance Raman spectra of bacteria were obtained at multiple wavelengths between 220 and 260 nm; a range that encompasses the resonance frequencies of cellular constituents. We find that spectra of the same bacterial species exhibit differences due to both growth condition and growth phase, but the larger differences reflect changes due to growth phase. The differences in the Raman spectra correlate with genetic differences among the species. Using a Pearson correlation based algorithm, we achieve successful identification of these bacteria in 83% of the cases.

  4. Raman Study of SWNT Under High Pressure

    NASA Astrophysics Data System (ADS)

    Venkateswaran, U.; Rao, A. M.; Richter, E.; Eklund, P. C.; Smalley, R. E.

    1998-03-01

    A gasketed Merrill-Bassett-type diamond anvil cell was used for high pressure Raman measurements at room temperature. A 4:1 methanol-ethanol mixture served as the pressure transmitting medium. The radial mode (denoted as R, occuring at 186 cm-1 at 1 bar) and tangential modes (designated T_1, T_2, and T_3, located, respectively, at 1550, 1567, and 1593 cm-1 at 1 bar) were recorded for several representative pressures. With increasing pressure, both the R and T modes shift to higher frequencies with gradual weakening of intensity and broadening of linewidth. The radial mode disappears around ~ 2 GPa whereas the tangential modes, albeit weak in intensity, persist until 5.2 GPa. The decrease in Raman intensity under pressure can be attributed to a loss of resonance, since the strong Raman signals observed at ambient pressure have been interpreted as due a resonance with the electronic bands [1]. The R and T mode frequencies are fit to quadratic function of pressure i.e., ω=ω(0)+aP+bP^2 where `a' represents the linear pressure shift of the mode frequency which is proportional to the mode Gruneisen parameter. The linear pressure coefficient for the R mode is found to be nearly twice that of the high frequency T mode. A. M. Rao et al., Science 275, 187, 1997

  5. Laser Raman Spectroscopy in studies of corrosion and electrocatalysis

    SciTech Connect

    Melendres, C.A.

    1988-01-01

    Laser Raman Spectroscopy (LRS) has become an important tool for the in-situ structural study of electrochemical systems and processes in recent years. Following a brief introduction of the experimental techniques involved in applying LRS to electrochemical systems, we survey the literature for examples of studies in the inhibition of electrode reactions by surface films (e.g., corrosion and passivation phenomena) as well as the acceleration of reactions by electro-sorbates (electrocatalysis). We deal mostly with both normal and resonance Raman effects on fairly thick surface films in contrast to surface-enhanced Raman investigations of monolayer adsorbates, which is covered in another lecture. Laser Raman spectroelectrochemical studies of corrosion and film formation on such metals as Pb, Ag, Fe, Ni, Co, Cr, Au, stainless steel, etc. in various solution conditions are discussed. Further extension of the technique to studies in high-temperature and high-pressure aqueous environments is demonstrated. Results of studies of the structure of corrosion inhibitors are also presented. As applications of the LRS technique in the area of electrocatalysis, we cite studies of the structure of transition metal macrocyclic compounds, i.e., phthalocyanines and porphyrins, used for catalysis of the oxygen reduction reaction. 104 refs., 20 figs.

  6. Effects of inhomogeneous broadening on the resonance Raman excitation profile of lycopene

    NASA Astrophysics Data System (ADS)

    Cotting, J. E.; Hoskins, L. C.; Levan, M. E.

    1982-08-01

    The resonance Raman excitation profiles for the ν1, ν2, and ν3 vibrations of lycopene in ethyl alcohol, toluene, and carbon disulfide solvents have been measured. The results are interpreted in terms of a three-mode vibrational theory which includes both homogeneous and inhomogeneous broadening effects. Excellent agreement between calculated and observed excitation profiles and visible spectra was found, thus emphasizing the need to interpret resonance Raman data using a multimode vibrational model. The results indicate that the major broadening mechanism is homogeneous broadening, with about a 25% contribution from inhomogeneous broadening. The excitation profiles in carbon disulfide gave the largest inhomogeneous broadening.

  7. State-by-state investigation of destructive interference in resonance Raman spectra of neutral tyrosine and the tyrosinate anion with the simplified sum-over-states approach.

    PubMed

    Cabalo, Jerry B; Saikin, Semion K; Emmons, Erik D; Rappoport, Dmitrij; Aspuru-Guzik, Alán

    2014-10-16

    UV resonance Raman scattering is uniquely sensitive to the molecular electronic structure as well as intermolecular interactions. To better understand the relationship between electronic structure and resonance Raman cross section, we carried out combined experimental and theoretical studies of neutral tyrosine and the tyrosinate anion. We studied the Raman cross sections of four vibrational modes as a function of excitation wavelength, and we analyzed them in terms of the contributions of the individual electronic states as well as of the Albrecht A and B terms. Our model, which is based on time-dependent density functional theory (TDDFT), reproduced the experimental resonance Raman spectra and Raman excitation profiles for both studied molecules with good agreement. We found that for the studied modes, the contributions of Albrecht's B terms in the Raman cross sections were important across the frequency range spanning the L(a,b) and B(a,b) electronic excitations in tyrosine and the tyrosinate anion. Furthermore, we demonstrated that interference with high-energy states had a significant impact and could not be neglected even when in resonance with a lower-energy state. The symmetry of the vibrational modes served as an indicator of the dominance of the A or B mechanisms. Excitation profiles calculated with a damping constant estimated from line widths of the electronic absorption bands had the best consistency with experimental results.

  8. N-hydroxyguanidines as new heme ligands: UV-visible, EPR, and resonance Raman studies of the interaction of various compounds bearing a C=NOH function with microperoxidase-8.

    PubMed

    Lefevre-Groboillot, D; Dijols, S; Boucher, J L; Mahy, J P; Ricoux, R; Desbois, A; Zimmermann, J L; Mansuy, D

    2001-08-21

    Interaction between microperoxidase-8 (MP8), a water-soluble hemeprotein model, and a wide range of N-aryl and N-alkyl N'-hydroxyguanidines and related compounds has been investigated using UV-visible, EPR, and resonance Raman spectroscopies. All the N-hydroxyguanidines studied bind to the ferric form of MP8 with formation of stable low-spin iron(III) complexes characterized by absorption maxima at 405, 535, and 560 nm. The complex obtained with N-(4-methoxyphenyl) N'-hydroxyguanidine exhibits EPR g-values at 2.55, 2.26, and 1.86. The resonance Raman (RR) spectrum of this complex is also in agreement with an hexacoordinated low-spin iron(III) structure. The dissociation constants (K(s)) of the MP8 complexes with mono- and disubstituted N-hydroxyguanidines vary between 15 and 160 microM at pH 7.4. Amidoximes also form low-spin iron(III) complexes of MP8, although with much larger dissociation constants. Under the same conditions, ketoximes, aldoximes, methoxyguanidines, and guanidines completely fail to form such complexes with MP8. The K(s) values of the MP8-N-hydroxyguanidine complexes decrease as the pH of the solution is increased, and the affinity of the N-hydroxyguanidines toward MP8 increases with the pK(a) of these ligands. Altogether these results show that compounds involving a -C(NHR)=NOH moiety act as good ligands of MP8-Fe(III) with an affinity that depends on the electron-richness of this moiety. The analysis of the EPR spectrum of the MP8-N-hydroxyguanidine complexes according to Taylor's equations shows a strong axial distortion of the iron, typical of those observed for hexacoordinated heme-Fe(III) complexes with at least one pi donor axial ligand (HO(-), RO(-), or RS(-)). These data strongly suggest that N-hydroxyguanidines bind to MP8 iron via their oxygen atom after deprotonation or weakening of their O-H bond. It thus seems that N-hydroxyguanidines could constitute a new class of strong ligands for hemeproteins and iron(III)-porphyrins.

  9. Raman and surface-enhanced Raman study of asymmetrically substituted viologens

    SciTech Connect

    Lu, T.; Cotton, T.M.; Hurst, J.K.; Thompson, D.H.P.

    1988-12-01

    The normal Raman (NR), resonance Raman (RR), surface-enhanced Raman scattering (SERS), and surface-enhanced resonance Raman scattering (SERRS) spectra of the three redox forms of several asymmetric viologens, N-octyl-N'-methylviologen (C/sub 8/MV), N-dodecyl-N'-methylviologen (C/sub 12/MV), and N-hexadecyl-N'-methylviologen (C/sub 16/MV), have been characterized and compared with the corresponding spectra of the three redox forms of methylviologen (MV). It was observed that the substituents of the two N atoms of the viologen do not affect its overall symmetry. Only the Raman bands near 1200 cm/sup /minus/1/, containing major contributions from the N-alkyl stretching vibrations, are affected by the asymmetric substitution. The RR spectra of both the monomer and dimer forms of the cation radicals were obtained by varying the experimental conditions used in their preparation. As previously observed for MV, dimerization of the asymmetric viologen radicals produces splitting of certain RR bands. Resonance Raman spectra of the fully reduced viologens were also obtained and used to monitor the disproportionation reaction between the dication and fully reduced form of the viologen. Surface-enhanced Raman and SERRS spectra of the different asymmetric viologens were found to vary slightly due to changes in their adsorption behavior with increasing chain length of the alkyl substituent.

  10. Resonance Raman investigation of the photoreduction of methylviologen with Ru(bpy) 2+3 and proflavine as sensitizers

    NASA Astrophysics Data System (ADS)

    Forster, Martin; Hester, Ronald E.

    1982-01-01

    Reduced methylviologen (MV +) is detected by conventional resonance Raman spectroscopy in photoreactions of Ru(bpy) 2+3 or proflavine (PFH +) with MV 2+ Using apparatus for modulated excitation resonance Raman (MERR) spectroscopy, the irreversible MV + production with PFH + as sensitizer is traced back to triplet-triplet annihilation with simultaneous destruction of PFH +.

  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. UV resonance Raman finds peptide bond-Arg side chain electronic interactions.

    PubMed

    Sharma, Bhavya; Asher, Sanford A

    2011-05-12

    We measured the UV resonance Raman excitation profiles and Raman depolarization ratios of the arginine (Arg) vibrations of the amino acid monomer as well as Arg in the 21-residue predominantly alanine peptide AAAAA(AAARA)(3)A (AP) between 194 and 218 nm. Excitation within the π → π* peptide bond electronic transitions result in UVRR spectra dominated by amide peptide bond vibrations. The Raman cross sections and excitation profiles indicate that the Arg side chain electronic transitions mix with the AP peptide bond electronic transitions. The Arg Raman bands in AP exhibit Raman excitation profiles similar to those of the amide bands in AP which are conformation specific. These Arg excitation profiles distinctly differ from the Arg monomer. The Raman depolarization ratios of Arg in monomeric solution are quite simple with ρ = 0.33 indicating enhancement by a single electronic transition. In contrast, we see very complex depolarization ratios of Arg in AP that indicate that the Arg residues are resonance enhanced by multiple electronic transitions.

  13. 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.

  14. 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.

  15. Sample Modulated Raman Spectroscopy and Frequency Modulated Visible Light: Resonance Raman Spectrum of a Polydiacetylene Fiber.

    DTIC Science & Technology

    1978-04-20

    Raman Spectrum of a / / Polydiacetylene Fiber, j—, " WSSSSSSSfcSSSu Azinis, JUy^aughman, TYPE OF REPORT a PERIOD COVERED Surinder K/Bahl...Spectrum of a Polydiacetylene Fiber Costas Tzlnis, Surinder K. Bahl Paula Davidson and William M. Risen, Jr. Department of Chemistry Brown

  16. Efficient Heterostructures for Combined Interference and Plasmon Resonance Raman Amplification.

    PubMed

    Alvarez-Fraga, Leo; Climent-Pascual, Esteban; Aguilar-Pujol, Montserrat; Ramírez-Jiménez, Rafael; Jiménez-Villacorta, Félix; Prieto, Carlos; de Andrés, Alicia

    2017-02-01

    The detection, identification, and quantification of different types of molecules and the optical imaging of, for example, cellular processes are important challenges. Here, we present how interference-enhanced Raman scattering (IERS) in adequately designed heterostructures can provide amplification factors relevant for both detection and imaging. Calculations demonstrate that the key factor is maximizing the absolute value of the refractive indices' difference between dielectric and metal layers. Accordingly, Si/Al/Al2O3/graphene heterostructures have been fabricated by optimizing the thickness and roughness and reaching enhancement values up to 700 for 488 nm excitation. The deviation from the calculated enhancement, 1200, is mainly due to reflectivity losses and roughness of the Al layer. The IERS platforms are also demonstrated to improve significantly the quality of white light images of graphene and are foreseen to be adequate to reveal the morphology of 2D and biological materials. A graphene top layer is adequate for most organic molecule deposition and often quenches possible fluorescence, permitting Raman signal detection, which, for a rhodamine 6G (R6G) monolayer, presents a gain of 400. Without graphene, the nonquenched R6G fluorescence is similarly amplified. The wavelength dependence of the involved refractive indices predicts much higher amplification (around 10(4)) for NIR excitation. These interference platforms can therefore be used to gain contrast and intensity in white light, Raman, and fluorescence imaging. We also demonstrate that surface-enhanced Raman scattering and IERS amplifications can be efficiently combined, leading to a gain of >10(5) (at 488 nm) by depositing a Ag nanostructured transparent film on the IERS platform. When the plasmonic structures deposited on the IERS platforms are optimized, single-molecule detection can be actively envisaged.

  17. Raman microspectroscopic study of oral buccal mucosa

    NASA Astrophysics Data System (ADS)

    Behl, Isha; Mamgain, Hitesh; Deshmukh, Atul; Kukreja, Lekha; Hole, Arti R.; Krishna, C. Murali

    2014-03-01

    Oral cancer is the most common cancer among Indian males, with 5-year- survival-rates of less than 50%. Efficacy of Raman spectroscopic methods in non-invasive and objective diagnosis of oral cancers and confounding factors has already been demonstrated. The present Raman microspectroscopic study was undertaken for in-depth and site-specific analysis of normal and tumor tissues. 10 normal and 10 tumors unstained sections from 20 tissues were accrued. Raman data of 160 x 60 μm and 140 x 140 μm in normal and tumor sections, respectively, were acquired using WITec alpha 300R equipped with 532 nm laser, 50X objective and 600 gr/mm grating. Spectral data were corrected for CCDresponse, background. First-derivitized and vector-normalized data were then subjected to K-mean cluster analysis to generate Raman maps and correlated with their respective histopathology. In normal sections, stratification among epithelial layers i.e. basal, intermediate, superficial was observed. Tumor, stromal and inflammatory regions were identified in case of tumor section. Extracted spectra of the pathologically annotated regions were subjected to Principal component analysis. Findings suggest that all three layers of normal epithelium can be differentiated against tumor cells. In epithelium, basal and superficial layers can be separated while intermediate layer show misclassifications. In tumors, discrimination of inflammatory regions from tumor cells and tumor-stroma regions were observed. Finding of the study indicate Raman mapping can lead to molecular level insights of normal and pathological states.

  18. Activated vibrational modes and Fermi resonance in tip-enhanced Raman spectroscopy.

    PubMed

    Sun, Mengtao; Fang, Yurui; Zhang, Zhenyu; Xu, Hongxing

    2013-02-01

    Using p-aminothiophenol (PATP) molecules on a gold substrate and high-vacuum tip-enhanced Raman spectroscopy (HV-TERS), we show that the vibrational spectra of these molecules are distinctly different from those in typical surface-enhanced Raman spectroscopy. Detailed first-principles calculations help to assign the Raman peaks in the TERS measurements as Raman-active and IR-active vibrational modes of dimercaptoazobenzene (DMAB), providing strong spectroscopic evidence for the dimerization of PATP molecules to DMAB under the TERS setup. The activation of the IR-active modes is due to enhanced electromagnetic field gradient effects within the gap region of the highly asymmetric tip-surface geometry. Fermi resonances are also observed in HV-TERS. These findings help to broaden the versatility of TERS as a promising technique for ultrasensitive molecular spectroscopy.

  19. Electronic Resonance Enhancement in Raman and CARS Spectroscopy: Surface Enhanced Scattering of Highly Fluorescent Molecules

    NASA Astrophysics Data System (ADS)

    Lawhead, Carlos; Ujj, Laszlo

    2015-03-01

    Surface enhanced Raman spectroscopy (SERS) is an extremely useful tool in increasing sensitivity of Raman spectroscopy; this technique significantly increases the signal from vibrational resonances which can overcome background fluoresces. Silver nanoparticles coated substrates and the silver nanoparticles in solution were used on a variety of fluorescent molecules in order to overcome sample complexities and measure the vibrational spectra. The possible enhancement of SERS using a coherent Raman (CARS) method was investigated, but enhancement factors due to Surface Enhanced CARS have yet to be verified. The instrument used was developed in the University of West Florida Physics Department utilized the second harmonic of a Nd:YAG laser to provide the excitation wavelength at 532 nm and is capable of both transmission and reflection Raman measurements. Special thanks to the UWF Office of Undergraduate Research.

  20. Surface-enhanced resonance Raman spectroscopy as an ancillary high-performance liquid chromatography detector for nitrophenol compounds

    SciTech Connect

    Ni, F.; Thomas, L.; Cotton, T.M. )

    1989-04-15

    In this study, the potential application of surface-enhanced resonance Raman scattering (SERRS) spectroscopy as an off-line secondary detector for HPLC has been evaluated. Four nitrophenol compounds, 2-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol, and 4,6-dinitrocresol were separated by isocratic reverse-phase high-performance liquid chromatography (RP-HPLC) and monitored with a conventional UV detector. Resonance Raman (RR) and SERRS spectroscopy were next used to provide the required specificity for distinguishing the nitrophenol compounds. The SERRS detection limit for both 2-nitrophenol and 4-nitrophenol was calculated to be 14 ppb and that for 2,4-dinitrophenol and 4,6-dinitrocresol was estimated to lie near the parts-per-billion level as well. This detection limit is 2-3 orders of magnitude lower than that obtained by RR spectroscopy.

  1. In vivo macular pigment measurements: a comparison of resonance Raman spectroscopy and heterochromatic flicker photometry

    PubMed Central

    Hogg, R E; Anderson, R S; Stevenson, M R; Zlatkova, M B; Chakravarthy, U

    2007-01-01

    Aim To investigate whether two methods of measuring macular pigment—namely, heterochromatic flicker photometry (HFP) and resonance Raman spectroscopy (RRS)—yield comparable data. Methods Macular pigment was measured using HFP and RRS in the right eye of 107 participants aged 20–79 years. Correlations between methods were sought and regression models generated. RRS was recorded as Raman counts and HFP as macular pigment optical density (MPOD). The average of the top three of five Raman counts was compared with MPOD obtained at 0.5° eccentricity, and an integrated measure (spatial profile; MPODsp) computed from four stimulus sizes on HFP. Results The coefficient of variation was 12.0% for MPODsp and 13.5% for Raman counts. MPODsp exhibited significant correlations with Raman counts (r = 0.260, p = 0.012), whereas MPOD at 0.5° did not correlate significantly (r = 0.163, p = 0.118). MPODsp was not significantly correlated with age (p = 0.062), whereas MPOD at 0.5° was positively correlated (p = 0.011). Raman counts showed a significant decrease with age (p = 0.002) and were significantly lower when pupil size was smaller (p = 0.015). Conclusions Despite a statistically significant correlation, the correlations were weak, with those in excess of 90% of the variance between MPODsp and Raman counts remaining unexplained, meriting further research. PMID:16825281

  2. In vivo macular pigment measurements: a comparison of resonance Raman spectroscopy and heterochromatic flicker photometry.

    PubMed

    Hogg, R E; Anderson, R S; Stevenson, M R; Zlatkova, M B; Chakravarthy, U

    2007-04-01

    To investigate whether two methods of measuring macular pigment-namely, heterochromatic flicker photometry (HFP) and resonance Raman spectroscopy (RRS)--yield comparable data. Macular pigment was measured using HFP and RRS in the right eye of 107 participants aged 20-79 years. Correlations between methods were sought and regression models generated. RRS was recorded as Raman counts and HFP as macular pigment optical density (MPOD). The average of the top three of five Raman counts was compared with MPOD obtained at 0.5 degrees eccentricity, and an integrated measure (spatial profile; MPODsp) computed from four stimulus sizes on HFP. The coefficient of variation was 12.0% for MPODsp and 13.5% for Raman counts. MPODsp exhibited significant correlations with Raman counts (r = 0.260, p = 0.012), whereas MPOD at 0.5 degrees did not correlate significantly (r = 0.163, p = 0.118). MPODsp was not significantly correlated with age (p = 0.062), whereas MPOD at 0.5 degrees was positively correlated (p = 0.011). Raman counts showed a significant decrease with age (p = 0.002) and were significantly lower when pupil size was smaller (p = 0.015). Despite a statistically significant correlation, the correlations were weak, with those in excess of 90% of the variance between MPODsp and Raman counts remaining unexplained, meriting further research.

  3. Microsystem light source at 488 nm for shifted excitation resonance Raman difference spectroscopy.

    PubMed

    Maiwald, Martin; Schmidt, Heinar; Sumpf, Bernd; Güther, Reiner; Erbert, Götz; Kronfeldt, Heinz-Detlef; Tränkle, Günther

    2009-11-01

    A microsystem light source emitting at 488 nm was tested and applied as a light source for shifted excitation resonance Raman difference spectroscopy (SERRDS). A nonlinear frequency conversion using a distributed feedback (DFB) diode laser emission at 976 nm and a periodically poled lithium niobate (PPLN) waveguide crystal was realized on a micro-optical bench with a footprint of 25 mm x 5 mm. Joint temperature management via the microbench is used for wavelength tuning. Two emission lines at 487.61 nm and 487.91 nm are used for the SERRDS experiments. The Raman spectra of the test sample polystyrene demonstrate that a laser bandpass filter did not need to be implemented. Resonance Raman spectra of Tartrazine (FD&C Yellow 5, E 102) in distilled water are presented to demonstrate the suitability of this light source for SERRDS in, e.g., food safety control.

  4. 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.

  5. 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.

  6. 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.

  7. High-pressure Raman study of Terephthalonitrile

    NASA Astrophysics Data System (ADS)

    Li, DongFei; Zhang, KeWei; Song, MingXing; Zhai, NaiCui; Sun, ChengLin; Li, HaiBo

    2017-02-01

    The in situ high-pressure Raman spectra of Terephthalonitrile (TPN) have been investigated from ambient to 12.6 GPa at room temperature. All the fundamental vibrational modes of TPN at ambient were assigned based on the first-principle calculations. A detailed Raman spectroscopy analysis revealed that TPN underwent a phase transition at 5.3 GPa. The frequencies of the TPN Raman peaks increase with increasing the pressure which can be attributed to the reduction in the interatomic distances and the escalation of effective force constants. The intensity of the C-C-C ring-out-plane deformation mode increases gradually as the frequency remains almost constant during the compression which can be explained by the existence of π-π interactions in TPN molecules. Additionally, the pressure-induced structural changes of TPN on the Fermi resonance between the C ≡ N out-of-plane vibration mode and the C - CN out-of-plane vibration mode have been analyzed.

  8. 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…

  9. Ab initio calculation of resonance Raman cross sections based on excited state geometry optimization.

    PubMed

    Gaff, J F; Franzen, S; Delley, B

    2010-11-04

    A method for the calculation of resonance Raman cross sections is presented on the basis of calculation of structural differences between optimized ground and excited state geometries using density functional theory. A vibrational frequency calculation of the molecule is employed to obtain normal coordinate displacements for the modes of vibration. The excited state displacement relative to the ground state can be calculated in the normal coordinate basis by means of a linear transformation from a Cartesian basis to a normal coordinate one. The displacements in normal coordinates are then scaled by root-mean-square displacement of zero point motion to calculate dimensionless displacements for use in the two-time-correlator formalism for the calculation of resonance Raman spectra at an arbitrary temperature. The method is valid for Franck-Condon active modes within the harmonic approximation. The method was validated by calculation of resonance Raman cross sections and absorption spectra for chlorine dioxide, nitrate ion, trans-stilbene, 1,3,5-cycloheptatriene, and the aromatic amino acids. This method permits significant gains in the efficiency of calculating resonance Raman cross sections from first principles and, consequently, permits extension to large systems (>50 atoms).

  10. 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…

  11. Simulation of the resonance Raman spectra for 5-halogenated (F, Cl, and Br) uracils.

    PubMed

    Sun, Shuai; Brown, Alex

    2015-04-30

    The resonance Raman spectra of the 5-halogenated (F, Cl, and Br) uracils are simulated via the Herzberg-Teller (HT) short-time dynamics formalism. The gradient of the S1 excited state is computed at the CAMB3LYP/aug-cc-pVTZ level of theory in the conductor-like polarizable continuum model for water (C-PCM, H2O), based on the equilibrium geometry determined using PBE0/aug-cc-pVTZ in H2O (C-PCM). The simulated resonance Raman spectra show good agreement with the experimental spectra in terms of both peak positions and intensities. The differences between the resonance Raman spectra of the three 5-halogenated uracils, caused by the effect of halogen substitution, are examined in terms of ground-state normal-mode eigenvectors and excited-state Cartesian gradients, according to the HT formalism. The differences in the normal-mode eigenvectors and excited-state Cartesian gradients between 5-fluorouracil and 5-chlorouracil are used to interpret the dissimilarity between their resonance Raman spectra. Meanwhile, the similarity between the spectra of 5-chlorouracil and 5-bromouracil is explained by the correspondence between their normal modes and excited-state gradients.

  12. Using Raman Spectroscopy to Study Diamond Thin Films

    NASA Astrophysics Data System (ADS)

    Lin, Yi-Hsuan; Zwicker, Andrew

    2011-10-01

    Diamond thin films (DTF), due to their extreme hardness, low electrical conductivity and chemical inertness, have various applications in semiconductor and machining industry. DTF strengthen machining and cutting tools that demand more precision and resist chemical corrosions as electrodes. The DTF created in this investigation were produced using a hybrid physical-chemical vapor deposition process in an electron cyclotron resonance sputter source. The samples formed can be amorphous carbon, graphite, or diamond. A method to test whether the sputter source successfully created diamond is Raman spectroscopy, a non-invasive technique that utilizes photo excitation and Raman scattering of monochromatic light. A sharp peak at 1332 inverse cm indicates the signature Raman shift of the sp3 C-C bond of pure diamond in these spectra. Graphite and amorphous carbon have their signature peaks near 1580 inverse cm and 1343 inverse cm. The technique is used to study wafer quality as a function of plasma parameters. Results will ultimately be benchmarked against Raman spectroscopy system at The College of New Jersey, and more samples will be produced to ensure the uniformity of the sputter source.

  13. 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.

  14. 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

  15. The local spin-flip spectral distribution obtained by resonant x-ray Raman scattering

    NASA Astrophysics Data System (ADS)

    de Groot, Frank; Kuiper, Pieter; Sawatzky, George

    1998-03-01

    We will show that resonant x-ray Raman scattering can be used to study the local spin-flip excitation spectral distribution in magnetically ordered 3d transition metal compounds. We demonstrate with realistic calculations on the 3p x-ray absorption edge of a Cu^2+ compound and the 2p edge of a Ni^2+ compound that the scattered x-ray energy and intensity distribution contains the excitation spectrum resulting from a single local spin-flip, as well as dd excitations accompanied by local spin flip satellites. We develop the theory describing this effect and discuss the polarization conditions which can be used to observe these effects.

  16. Polarization dependence of tip-enhanced Raman and plasmon-resonance Rayleigh scattering spectra

    NASA Astrophysics Data System (ADS)

    Kitahama, Yasutaka; Uemura, Shohei; Katayama, Ryota; Suzuki, Toshiaki; Itoh, Tamitake; Ozaki, Yukihiro

    2017-06-01

    Tip-enhanced Raman scattering (TERS) spectroscopy has high sensitivity and high spatial resolution, although it shows low reproducibility due to the variable optical properties of the tips. In the present study, polarized scattering spectra of localized surface plasmon resonance (LSPR) at the apex of the tip induced by conventional dark field illumination were compared with the corresponding TERS spectra, generated by excitation using polarization not only parallel and perpendicular to the tip, but also vertical to the sample plane (z-polarization). The polarization-dependence of LSPR was consistent with that of the TERS. Thus, the optical properties of the tip can be easily optimized before TERS measurement by excitation polarization that induces the largest LSPR signal.

  17. Raman spectroscopic studies of gas/aerosol chemical reactions

    SciTech Connect

    Aardahl, C.L.; Davis, E.J.

    1995-12-31

    Reactions between sorbent particles and SO{sub 2} can be used to reduce atmospheric pollution either by {open_quotes}dry scrubbing{close_quotes} or {open_quotes}wet scrubbing{close_quotes} processes. This paper reports Raman spectroscopy results for single electrodynamically levitated droplets of NaOH reacting with SO{sub 2} and studies of the dehydration reactions of some hygroscopic salt species. The NaOH/SO{sub 2} reaction products and the liquid or solid state of the products are shown to depend on the gas phase SO{sub 2} concentration. Deliquesced particles of NaOH exhibit enhanced light scattering intensities associated with morphological resonances of the incident laser light, but crystalline materials show no such resonances. Raman-active hygroscopic salts exhibit bond frequencies characteristic of the stretching vibrations of the anionic group, but these frequencies are different in the presence of water because hydrogen bonding changes the bond force. This allows efficient tracking of the dehydration reactions in hygroscopic aerosols by Raman spectroscopy as the intensities of the two different modes are related to the degree of dehydration in the particle.

  18. 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.

  19. Single- and few-layer WTe2 and their suspended nanostructures: Raman signatures and nanomechanical resonances

    NASA Astrophysics Data System (ADS)

    Lee, Jaesung; Ye, Fan; Wang, Zenghui; Yang, Rui; Hu, Jin; Mao, Zhiqiang; Wei, Jiang; Feng, Philip X.-L.

    2016-04-01

    Single crystal tungsten ditelluride (WTe2) has recently been discovered to exhibit non-saturating extreme magnetoresistance in bulk; it has also emerged as a new layered material from which atomic layer crystals can be extracted. While atomically thin WTe2 is attractive for its unique properties, little research has been conducted on single- and few-layer WTe2. Here we report the isolation of single- and few-layer WTe2, as well as the fabrication and characterization of the first WTe2 suspended nanostructures. We have observed new Raman signatures of single- and few-layer WTe2 that have been theoretically predicted but have not been reported to date, in both on-substrate and suspended WTe2 flakes. We have further probed the nanomechanical properties of suspended WTe2 structures by measuring their flexural resonances, and obtain a Young's modulus of EY ~ 80 GPa for the suspended WTe2 flakes. This study paves the way for future investigations and utilizations of the multiple new Raman fingerprints of single- and few-layer WTe2, and for explorations of mechanical control of WTe2 atomic layers.

  20. Resonance Raman spectroscopy of red blood cells using near-infrared laser excitation.

    PubMed

    Wood, Bayden R; Caspers, Peter; Puppels, Gerwin J; Pandiancherri, Shveta; McNaughton, Don

    2007-03-01

    Resonance Raman spectra of oxygenated and deoxygenated functional erythrocytes recorded using 785 nm laser excitation are presented. The high-quality spectra show a mixture of enhanced A(1g), A(2g), B(1g), B(2g), E(u) and vinyl modes. The high sensitivity of the Raman system enabled spectra from four oxygenation and deoxygenation cycles to be recorded with only 18 mW of power at the sample over a 60-minute period. This low power prevented photo-/thermal degradation and negated protein denaturation leading to heme aggregation. The large database consisting of 210 spectra from the four cycles was analyzed with principal components analysis (PCA). The PC1 loadings plot provided exquisite detail on bands associated with the oxygenated and deoxygenated states. The enhancement of a band at 567 cm(-1), observed in the spectra of oxygenated cells and the corresponding PC1 loadings plot, was assigned to the Fe-O(2) stretching mode, while a band appearing at 419 cm(-1) was assigned to the Fe-O-O bending mode based on previous studies. For deoxygenated cells, the enhancement of B(1g) modes at 785 nm excitation is consistent with vibronic coupling between band III and the Soret transition. In the case of oxygenated cells, the enhancement of iron-axial out-of-plane modes and non-totally symmetric modes is consistent with enhancement into the y,z-polarized transition a(iu)(pi)-->d(xz)+O(2)(pi(g)) centered at 785 nm. The enhancement of non-totally symmetric B(1g) modes in oxygenated cells suggests vibronic coupling between band IV and the Soret band. This study provides new insights into the vibrational dynamics, electronic structure and resonant enhancement of heme moieties within functional erythrocytes at near-IR excitation wavelengths.

  1. "Parallel factor analysis of multi-excitation ultraviolet resonance Raman spectra for protein secondary structure determination".

    PubMed

    Oshokoya, Olayinka O; JiJi, Renee D

    2015-09-10

    Protein secondary structural analysis is important for understanding the relationship between protein structure and function, or more importantly how changes in structure relate to loss of function. The structurally sensitive protein vibrational modes (amide I, II, III and S) in deep-ultraviolet resonance Raman (DUVRR) spectra resulting from the backbone C-O and N-H vibrations make DUVRR a potentially powerful tool for studying secondary structure changes. Experimental studies reveal that the position and intensity of the four amide modes in DUVRR spectra of proteins are largely correlated with the varying fractions of α-helix, β-sheet and disordered structural content of proteins. Employing multivariate calibration methods and DUVRR spectra of globular proteins with varying structural compositions, the secondary structure of a protein with unknown structure can be predicted. A disadvantage of multivariate calibration methods is the requirement of known concentration or spectral profiles. Second-order curve resolution methods, such as parallel factor analysis (PARAFAC), do not have such a requirement due to the "second-order advantage." An exceptional feature of DUVRR spectroscopy is that DUVRR spectra are linearly dependent on both excitation wavelength and secondary structure composition. Thus, higher order data can be created by combining protein DUVRR spectra of several proteins collected at multiple excitation wavelengths to give multi-excitation ultraviolet resonance Raman data (ME-UVRR). PARAFAC has been used to analyze ME-UVRR data of nine proteins to resolve the pure spectral, excitation and compositional profiles. A three factor model with non-negativity constraints produced three unique factors that were correlated with the relative abundance of helical, β-sheet and poly-proline II dihedral angles. This is the first empirical evidence that the typically resolved "disordered" spectrum represents the better defined poly-proline II type structure.

  2. Signal enhancement of surface enhanced Raman scattering and surface enhanced resonance Raman scattering using in situ colloidal synthesis in microfluidics.

    PubMed

    Wilson, Rab; Bowden, Stephen A; Parnell, John; Cooper, Jonathan M

    2010-03-01

    We demonstrate the enhanced analytical sensitivity of both surface enhanced Raman scattering (SERS) and surface enhanced resonance Raman scattering (SERRS) responses, resulting from the in situ synthesis of silver colloid in a microfluidic flow structure, where both mixing and optical interrogation were integrated on-chip. The chip-based sensor was characterized with a model Raman active label, rhodamine-6G (R6G), and had a limit of detection (LOD) of ca. 50 fM (equivalent to single molecule detection). The device was also used for the determination of the natural pigment, scytonemin, from cyanobacteria (as an analogue for extraterrestrial life existing in extreme environments). The observed LOD of approximately 10 pM (ca. <400 molecules) demonstrated the analytical advantages of working with freshly synthesized colloid in such a flow system. In both cases, sensitivities were between 1 and 2 orders of magnitude greater in the microfluidic system than those measured using the same experimental parameters, with colloid synthesized off-chip, under quiescent conditions.

  3. 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.

  4. Spectral shapes of surface-enhanced resonance Raman scattering sensitive to the refractive index of media around single Ag nanoaggregates

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    We found large spectral changes in surface-enhanced resonance Raman scattering (SERRS) with increasing refractive index of media around single Ag nanoaggregates. We analyzed relationship between the spectral changes in SERRS and those in plasma (plasmon) resonance based on the twofold electromagnetic (EM) enhancement theory. The analysis revealed that the changes in SERRS spectra are induced by changes in spectral shapes of twofold EM enhancement factors, which arise from coupling of plasma resonance with both incident and Raman scattering light.

  5. 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

  6. Study of the configurations of 3-aryl-substituted 1,5-diphenylformazans by resonance Raman and absorption spectroscopy: steric and conjugation effects of the substituent

    NASA Astrophysics Data System (ADS)

    Hiura, Hidefumi; Takahashi, Hiroaki

    1989-09-01

    3-Aryl-substituted 1,5-diphenylformazans exist as one of the following two isomeric species in the solid state; the yellow isomer having the trans-anti-s- trans configuration with respect to the NN, CN and CN bonds of the formazan skeleton and the red isomer having the trans-syn-s- cis configuration. The other red isomer having the trans-syn-s- trans configuration, which exists when the substituent is an alkyl group, is not detected. Two effects are considered to be operative in determining the relative stabilities of these configurations: (1) the resonance energy arising from the conjugation between the π-electron systems of the formazan skeleton and the aryl substituent, and (2) the steric repulsion between the formazan skeleton and the groups (or atoms) attached to the ortho positions of the aryl substituent. In solutions, these two isomers are in equilibrium, their relative populations being dependent on the nature of the solvent as well as on the bulkiness of the groups attached to the ortho positions of the aryl substituent.

  7. Time-gated pre-resonant femtosecond stimulated Raman spectroscopy of diethylthiatricarbocyanine iodide.

    PubMed

    Kim, Hyung Min; Kim, Hyunmin; Yang, Ilseung; Jin, Seung Min; Suh, Yung Doug

    2014-03-21

    We present time-gated femtosecond stimulated Raman spectroscopy (fSRS) under the pre-resonance Raman conditions of diethylthiatricarbocyanine (DTTC) iodide. A 'pseudo emission-free' condition is achieved by delivering the probe beam ahead of the pump beam. Regeneratively amplified pulse trains are employed to create an angle-geometry (non-collimated) mixing between the pump and probe beams, leading to highly sensitive measurement of the stimulated Raman gain. Time-integrated spectroscopy allows for a more quantitative distinction between the contributions of stimulated Raman scattering and stimulated emission. We successfully obtain a highly sensitive (signal-to-noise ratio >100) stimulated Raman spectrum under the optimized conditions, which compares favourably to results obtained using two-dimensional correlation spectroscopy (2DCOS). Given the optical pre-resonance of ∼0.1 eV, the background signals mostly originate from the stimulated emission of excited electrons and are significantly reduced by partial overlapping of the pump and probe beams; a genuine fSRS spectral profile is obtained for a temporal delay of ∼0.2 ps between the two beams.

  8. 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.

  9. 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.

  10. Resonance Raman Measurement of Macular Carotenoids in Normal Subjects and in Age-related Macular Degeneration Patients

    PubMed Central

    Bernstein, Paul S.; Zhao, Da-You; Wintch, Steven W.; Ermakov, Igor V.; McClane, Robert W.; Gellermann, Werner

    2011-01-01

    Purpose Dietary carotenoids lutein and zeaxanthin may play a protective role against visual loss from age-related macular degeneration (AMD) through antioxidant and light screening mechanisms. We used a novel noninvasive objective method to quantify lutein and zeaxanthin in the human macula using resonance Raman spectroscopy and compared macular pigment levels in AMD and normal subjects. Design Observational study of an ophthalmology clinic-based population. Participants and Controls Ninety-three AMD eyes from 63 patients and 220 normal eyes from 138 subjects. Methods Macular carotenoid levels were quantified by illuminating the macula with a low-power argon laser spot and measuring Raman backscattered light using a spectrograph. This technique is sensitive, specific, and repeatable even in subjects with significant macular pathologic features. Main Outcome Measure Raman signal intensity at 1525 cm−1 generated by the carbon–carbon double-bond vibrations of lutein and zeaxanthin. Results Carotenoid Raman signal intensity declined with age in normal eyes (P < 0.001). Average levels of lutein and zeaxanthin were 32% lower in AMD eyes versus normal elderly control eyes as long as the subjects were not consuming high-dose lutein supplements (P = 0.001). Patients who had begun to consume supplements containing high doses of lutein (≥4 mg/day) regularly after their initial diagnosis of AMD had average macular pigment levels that were in the normal range (P = 0.829) and that were significantly higher than in AMD patients not consuming these supplements (P = 0.038). Conclusions These findings are consistent with the hypothesis that low levels of lutein and zeaxanthin in the human macula may represent a pathogenic risk factor for the development of AMD. Resonance Raman measurement of macular carotenoid pigments could play an important role in facilitating large-scale prospective clinical studies of lutein and zeaxanthin protection against AMD, and this technology may

  11. Demonstration of composite signal enhancement from surface enhanced Raman spectroscopy in a liquid core optical ring resonator

    NASA Astrophysics Data System (ADS)

    White, Ian M.; Gohring, John; Fan, Xudong

    2007-09-01

    Surface enhanced Raman spectroscopy (SERS) utilizing silver colloids for localized plasmonic enhancement has been heavily researched due to its tremendous increase in the Raman signal of bio/chemical molecules. We demonstrate further enhancement by multiplying the SERS effect by the resonant enhancement of a ring resonator microcavity. The liquid core optical ring resonator (LCORR) offers a high-performance and practical design to obtain this composite enhancement for bio/chemical molecule detection. The LCORR integrates an array of optical ring resonators into a capillary-based microfluidic channel to form a novel bio/chemical sensing platform. The circular cross-section of the glass capillary acts as an optical ring resonator, with the evanescent field of the resonant light interacting with the sample passing through the capillary. The LCORR has already been well-studied for applications in label free biomolecule sensing. In this work, we utilize a silver colloid solution inside the capillary to perform SERS-based detection. In contrast to a typical SERS system where the incident light interacts with the colloid and target molecules only once, in the LCORR system, the tightly confined light resonates around the capillary wall, repeatedly interacting with the SERS system. Our experimental results show the increased enhancement due to the composite effect of the cavity resonance and the localized plasmonic effect of the nanoparticles inside the cavity. We have achieved detection of 3.3 nM R6G inside the LCORR. In addition to the excellent sensitivity, this detection system represents an advancement in the development of practical SERS bio/chemical sensors due to the arrayed nature of the sensors combined with the integrated microfluidics of the LCORR.

  12. Resonance Raman and photoluminescence excitation profiles and excited-state dynamics in CdSe nanocrystals

    NASA Astrophysics Data System (ADS)

    Baker, Joshua A.; Kelley, David F.; Kelley, Anne Myers

    2013-07-01

    Resonance Raman excitation profiles for the longitudinal optical (LO) phonon fundamental and its first overtone have been measured for organic ligand capped, wurtzite form CdSe nanocrystals of ˜3.2 nm diameter dissolved in chloroform. The absolute differential Raman cross-section for the fundamental is much larger when excited at 532 or 543 nm, on the high-frequency side of the lowest-wavelength absorption maximum, than for excitation in the 458-476 nm range although the absorbance is higher at the shorter wavelengths. That is, the quantum yield for resonance Raman scattering is reduced for higher-energy excitation. In contrast, the photoluminescence quantum yield is relatively constant with wavelength. The optical absorption spectrum and the resonance Raman excitation profiles and depolarization dispersion curves are reproduced with a model for the energies, oscillator strengths, electron-phonon couplings, and dephasing rates of the multiple low-lying electronic excitations. The Huang-Rhys factor for LO phonon in the lowest excitonic transition is found to lie in the range S = 0.04-0.14. The strong, broad absorption feature about 0.5 eV above the lowest excitonic peak, typically labeled as the 1P3/21Pe transition, is shown to consist of at least two significant components that vary greatly in the magnitude of their electron-phonon coupling.

  13. Quantitative resonance Raman spectroscopy of N-acetylpyrrolidine in aqueous solution

    SciTech Connect

    Harhay, G.P.; Hudson, B.S. )

    1993-08-05

    The resonance Raman spectra of aqueous solutions of N-acetylpyrrolidine are determined at seven excitation frequencies from 40 660 to 53 130 cm[sup [minus]1] spanning the first strong absorption band which is broad and diffuse The resonance Raman spectra are dominated by the single amide II[prime]-like vibration at 1485 cm[sup [minus]1] and its overtones of up to five quanta. Absolute resonance Raman cross sections are determined for these fundamental and overtone transitions at each excitation wavelength by reference to an internal standard of sodium perchlorate. A quantitative analysis of these data and the broad absorption spectrum is made on the basis of a model for the electronic excitation that includes the effects of inhomogeneous broadening. The observation of only a single enhanced vibrational normal mode, with the assumption that there is no Duschinsky rotation upon electronic excitation, makes this a particularly simple case for detailed analysis. A reasonably good fit to the experimental data is obtained using standard assumptions of Lorentzian inhomogeneous broadening and A-term (Condom) Raman scattering. In this fitting procedure, the integrated absorption spectrum determines the transition dipole length. 43 refs., 4 figs., 2 tabs.

  14. Distance dependence of surface-enhanced resonance raman enhancement in Langmuir-Blodgett dye multilayers

    SciTech Connect

    Cotton, T.M.; Uphaus, R.A.; Moebius, D.

    1986-11-06

    Monolayers of a surface-active dye incorporated into inert matrix material were transferred onto structurally defined silver island films by the Langmuir-Blodgett technique. The dye-containing monolayers were spaced from the surface by accurately known increments by deposition of inert spacer monolayers. Surface-enhanced resonance Raman spectra were observed from dye molecules spaced as distant as six spacer increments (ca. 16 nm) from the silver surface. These results indicate an electromagnetic mechanism is operative in this system in contradiction to a chemical mechanism which would require direct contact between the Raman-active species and the metal surface.

  15. 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.

  16. Detection of acetylene by electronic resonance-enhanced coherent anti-Stokes Raman scattering

    NASA Astrophysics Data System (ADS)

    Chai, N.; Naik, S. V.; Kulatilaka, W. D.; Laurendeau, N. M.; Lucht, R. P.; Roy, S.; Gord, J. R.

    2007-06-01

    We report the detection of acetylene (C2H2) at low concentrations by electronic resonance-enhanced coherent anti-Stokes Raman scattering (ERE-CARS). Visible pump and Stokes beams are tuned into resonance with Q-branch transitions in the v2 Raman band of acetylene. An ultraviolet probe beam is tuned into resonance with the tilde{A}-tilde{X} electronic transition of C2H2, resulting in significant electronic resonance enhancement of the CARS signal. The signal is found to increase significantly with rising pressure for the pressure range 0.1-8 bar at 300 K. Collisional narrowing of the spectra appears to be important at 2 bar and above. A detection limit of approximately 25 ppm at 300 K and 1 bar is achieved for our experimental conditions. The signal magnitudes and the shape of the C2H2 spectrum are essentially constant for UV probe wavelengths from 233.0 to 238.5 nm, thus indicating that significant resonant enhancement is achieved even without tuning the probe beam into resonance with a specific electronic resonance transition.

  17. Krypton isotope analysis using near-resonant stimulated Raman spectroscopy

    SciTech Connect

    Whitehead, C.A.; Cannon, B.D.; Wacker, J.F.

    1994-12-01

    A method for measuring low relative abundances of {sup 85}Kr in one liter or less samples of air has been under development here at Pacific Northwest Laboratory. The goal of the Krypton Isotope Laser Analysis (KILA) method is to measure ratios of 10{sup {minus}10} or less of {sup 85}Kr to more abundant stable krypton. Mass spectrometry and beta counting are the main competing technologies used in rare-gas trace analysis and are limited in application by such factors as sample size, counting times, and selectivity. The use of high-resolution lasers to probe hyperfine levels to determine isotopic abundance has received much attention recently. In this study, we report our progress on identifying and implementing techniques for trace {sup 85}Kr analysis on small gas samples in a static cell as well as limitations on sensitivity and selectivity for the technique. High-resolution pulsed and cw lasers are employed in a laser-induced fluorescence technique that preserves the original sample. This technique, is based on resonant isotopic depletion spectroscopy (RIDS) in which one isotope is optically depleted while preserving the population of a less abundant isotope. The KILA method consists of three steps. In the first step, the 1s{sub 5} metastable level of krypton is populated via radiative cascade following two-photon excitation of the 2p{sub 6} energy level. Next, using RBDS, the stable krypton isotopes are optically depleted to the ground state through the 1s{sub 4} level with the bulk of the {sup 85}Kr population being preserved. Finally, the remaining metastable population is probed to determine {sup 85}Kr concentration. The experimental requirements for each of these steps are outlined below.

  18. Resonant Raman spectroscopy of single-wall carbon nanotubes under pressure

    NASA Astrophysics Data System (ADS)

    Merlen, A.; Bendiab, N.; Toulemonde, P.; Aouizerat, A.; San Miguel, A.; Sauvajol, J. L.; Montagnac, G.; Cardon, H.; Petit, P.

    2005-07-01

    We performed high pressure resonant Raman experiments on well characterized purified single-wall carbon nanotubes up to 40GPa using argon as pressure transmitting medium. We used two different excitating wavelengths, at 632.8nm and 514.5nm . In contrast with other studies no clear sign of phase transformation is observed up to the highest studied pressure of 40GPa . Our results suggest that the progressive disappearance of the radial breathing modes observed while increasing pressure should not be interpreted as the sign of a structural phase transition. Moreover, a progressive change of profile of the tangential modes is observed. For pressures higher than 20GPa the profile of those modes is the same for both laser excitations. We conclude that a progressive loss of resonance of single-wall carbon nanotubes under pressure might occur. In addition, after high pressure cycle we observed a decrease of intensity of the radial breathing and tangential modes and a strong increase of the D band.

  19. A detailed resonance Raman spectrum of Nickel(II)-substituted Pseudomonas aeruginosa azurin.

    PubMed

    Czernuszewicz, Roman S; Fraczkiewicz, Grazyna; Zareba, Adelajda A

    2005-08-08

    Nickel(II) and cobalt(II) derivatives of the blue copper protein Pseudomonas aeruginosa azurin have been studied by resonance Raman (RR) spectroscopy at liquid-nitrogen temperatures. Vibrational assignments for the observed RR bands of Ni(II)-azurin have been made through a study of (62)Ni-substituted azurin. A comparison of Ni(II)-azurin RR spectra with those of the wild type (Cu-containing) protein showed Ni(II)-S(Cys) stretching vibrations, nu(Ni-S)(Cys), at substantially lower frequencies (approximately 360 versus approximately 400 cm(-1), respectively), indicating that the Ni(II)-S(Cys) bond is much weaker than the corresponding Cu(II)-S(Cys) bond. Resonance enhanced predominantly nu(Ni-N)(His) modes indicate that the metal-N(His) bond distances in the Ni(II) derivative are the same as those in native azurin. The vibrational data also confirm a tetrahedral disposition of ligands about the metal in Ni(II)-azurin found in the protein crystallographic structures. As expected, excitation profile measurements on Ni(II)-azurin show that the nu(Ni-S)(Cys) assignable modes give maxima at the 440-nm absorption band, which confirms a S(Cys) --> Ni(II) charge-transfer origin of the 440-nm electronic transition in Ni(II)-substituted azurin.

  20. Measurement of sex steroids and analogs with a fiber optic probe using pulsed ultraviolet resonance Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Schulze, H. Georg; Greek, L. Shane; Blades, Michael W.; Bree, Alan V.; Gorzalka, Boris B.; Turner, Robin F. B.

    1997-05-01

    Resonance Raman spectroscopy, performed via an optical fiber probe, can be used in aqueous samples to detect a wide variety of chemical species in situ. It offers a potentially rapid, on-site alternative to the high performance chromatography/mass spectrometry methods currently considered definitive for the detection of sex steroids in human urine. As a first step in the development of a resonance Raman instrument for the rapid detection of sex steroids in biological samples, it had to be shown that these substances, their analogs, and the major components of human urine can be differentiated on the basis of their resonance Raman spectra. A fiber-optic linked Raman and tunable ultraviolet resonance Raman system was assembled with custom designed optical fiber probes. The ultraviolet absorption spectra of some sex steroids, analogs, and components of human urine were measured in order to determine feasible excitation light frequencies. We present here for the first time the UV resonance Raman spectra of these substances obtained via our novel fiber probes. These results indicate that some of the steroids tested can be differentiated from each other and from the major components of human urine on the basis of their resonance Raman spectra.

  1. Probing microstructures of molybdenum disulfide quantum dots by resonant Raman scattering

    NASA Astrophysics Data System (ADS)

    Bai, Ruipeng; Wang, Peijie; Fang, Yan

    2017-04-01

    Research on the photoluminescence (PL) mechanism of MoS2 quantum dots (MQDs) has entered into a new age that involves analyzing the complicated microstructures of MQDs that are presumably significant for PL emission. However, microstructures of MQDs have not been clearly observed and thoroughly identified by conventional detection techniques. In this work, pure MQDs were fabricated by pulsed laser ablation along the direction parallel to basal planes of the MoS2 crystal in deionized water to enable resonant Raman measurements. Resonant Raman scattering (RRS) that corresponds to microstructures of MQDs, especially defects and disorders at the edges and surfaces of MQDs, is obtained, which is distinctly different from that of bulk and monolayer MoS2 and has not been characterized in such a direct method by RRS spectroscopy. The highest intensity of the defect-induced LA(M) peak at approximately 217 cm-1, which is similar to the D band of graphene, indicates the existence of enormous defects and disorders. Furthermore, the LA(M) peak is split into a shoulder at 212 cm-1 and a peak at 217 cm-1 which are due to double resonance processes derived from defects on the edges and disorders in the planes, respectively. More resonant two-phonon Raman processes appear because of the strong electron-phonon coupling at resonance. In addition, the typical phonon modes of MoS2 and Raman-silent phonon modes are analyzed and identified. This work indicates that the features of microstructures of MQDs can be convincingly and experimentally characterized by RRS spectroscopy.

  2. Surface-enhanced Raman spectroscopy on a surface plasmon resonance biosensor platform for gene diagnostics

    NASA Astrophysics Data System (ADS)

    Yuan, W.; Ho, H. P.; Suen, Y. K.; Kong, S. K.; Lin, Chinlon; Prasad, Paras N.; Li, J.; Ong, Daniel H. C.

    2008-02-01

    We propose to integrate the surface-enhanced Raman spectroscopy (SERS) detection capability with a surface plasmon resonance (SPR) biosensor platform. As a demonstration setup, the experimental scheme is built from a Total Internal Reflection Fluorescence (TIRF) microscope. The sample surface is a gold-coated plasmonic crystal substrate. Two oligonucleotide (ODN) probes that have been labeled with two different Raman active dyes are used to achieve a sandwich assay of target ODNs or polynucleotide. Upon complementary hybridizations between the target and probe ODNs, the target can be identified by detecting the narrow-band spectroscopic fingerprints of the Raman tags. This concept has high potential for achieving multiplexed detection of ODN targets because a very large number of probes can be incorporated to the plasmonic crystal substrate, which may find applications in gene based diseases diagnostics. We also explored the detection of single molecules and achieved some preliminary results.

  3. Surface-enhanced Raman spectroscopic and surface plasmon resonance in situ study of self-assembly of 4-mercaptobenzoic acid on gold surface

    NASA Astrophysics Data System (ADS)

    Thi, Minh Do; Volka, Karel

    2010-07-01

    A feasibility study has been undertaken to assess the suitability of a commercially available SERS substrate for monitoring of self-assembling deposition process. Monolayer self-assembly of 4-mercaptobenzoic acid on SERS active substrate Klarite™ from absolute and acidified ethanol was studied and compared with deposition on SPR substrate from absolute ethanol. Changes in integral intensity of the phenyl bands at 1587 and 1076 cm -1 and ethanol band at 1451 cm -1 allow to follow structural changes in the monolayer. Stability of the monolayer assembled from acidified ethanol in contrast to the pure ethanol was demonstrated.

  4. Resonance Raman and photophysical studies of transition metal complexes in solution and entrapped in zeolites. Progress report, August 1, 1991--March 31, 1992

    SciTech Connect

    Kincaid, J.R.

    1992-03-31

    We have obtained convincing evidence for localization of the optical electron on a single-ring fragment of a chelated ``bipyridine-like`` ligand (ie., pyridylpyrazine or 4-Methyl-bipyridine). In addition we have completed studies of Ru(bipyrazine){sub 3}{sup 2+} in aqueous sulfuric acid (0--98% by weight) and find clear evidence for sequential addition of six-protons to the six peripheral nitrogen atoms. Studies of zeolite-entrapped complexes are continuing and a series of homo- and heteroleptic complexes have been prepared and characterized. Finally, the synthesis of zeolite-entrapped metallophthalocyanines has now been developed and the copper and cobalt analogues synthesized. The characterization of these materials is now in progress.

  5. 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.

  6. Surface-enhanced resonance Raman spectroscopic characterization of the protein native structure.

    PubMed

    Feng, Manliang; Tachikawa, Hiroyasu

    2008-06-11

    Surface-enhanced resonance Raman scattering (SERRS) spectra of biological species are often different from their resonance Raman (RR) spectra. A home-designed Raman flow system is used to determine the factors that contribute to the difference between the SERRS and RR of met-myoglobin (metMb). The results indicate that both the degree of protein-nanoparticles interaction and the laser irradiation contribute to the structural changes and are responsible for the observed differences between the SERRS and RR spectra of metMb. The prolonged adsorption of the protein molecules on the nanoparticle surface, which is the condition normally used for the conventional SERRS experiments, disturbs the heme pocket structure and facilitates the charge transfer process and the photoinduced transformation of proteins. The disruption of the heme pocket results in the loss of the distal water molecule, and the resulting SERRS spectrum of metMb shows a 5-coordinated high-spin heme. The flow system, when operated at a moderately high flow rate, can basically eliminate the factors that disturb the protein structure while maintaining a high enhancement factor. The SERRS spectrum obtained from a 1 x 10 (-7) M metMb solution using this flow system is basically identical to the RR spectrum of a 5 x 10 (-4) M metMb solution. Therefore, the Raman flow system reported here should be useful for characterizing the protein-nanoparticles interaction and the native structure of proteins using SERRS spectroscopy.

  7. 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.

  8. Multi-wavelength Raman Spectroscopic Study of Silica-supported Vanadium Oxide Catalysts

    SciTech Connect

    Wu, Zili; Dai, Sheng; Overbury, Steven {Steve} H

    2010-01-01

    The molecular structure of silica-supported vanadium oxide (VOx) catalysts over wide range of surface VOx density (0.0002 8 V/nm2) has been investigated in detail under dehydrated condition by in situ multi-wavelength Raman spectroscopy (laser excitations at 244, 325, 442, 532, and 633 nm) and in situ UV-Vis diffuse reflectance spectroscopy. Resonance Raman scattering is clearly observed using 244 and 325-nm excitations while normal Raman scattering occurs using excitation at the three visible wavelengths. The observation of strong fundamentals, overtones and combinational bands due to selective resonance enhancement effect helps clarify assignments of some of the VOx Raman bands (920, 1032, and 1060 cm-1) whose assignments have been controversial. The resonance Raman spectra of dehydrated VOx/SiO2 show V=O band at smaller Raman shift than that in visible Raman spectra, an indication of the presence of two different surface VOx species on dehydrated SiO2 even at sub-monolayer VOx loading. Quantitative estimation shows that the two different monomeric VOx species coexist on silica surface from very low VOx loadings and transform to crystalline V2O5 at VOx loadings above monolayer. It is postulated that one of the two monomeric VOx species has pyramidal structure and the other is in partially hydroxylated pyramidal mode. The two VOx species show similar reduction-oxidation behavior and may both participate in redox reactions catalyzed by VOx/SiO2 catalysts. This study demonstrates the advantages of multi-wavelength Raman spectroscopy over conventional single-wavelength Raman spectroscopy in structural characterization of supported metal oxide catalysts.

  9. Distinct structural and redox properties of the heme active site in bacterial dye decolorizing peroxidase-type peroxidases from two subfamilies: resonance Raman and electrochemical study.

    PubMed

    Sezer, Murat; Santos, Ana; Kielb, Patrycja; Pinto, Tiago; Martins, Ligia O; Todorovic, Smilja

    2013-05-07

    Spectroscopic data of dye decolorizing peroxidases (DyPs) from Bacillus subtilis (BsDyP), an A subfamily member, and Pseudomonas putida (PpDyP), a B subfamily enzyme, reveal distinct heme coordination patterns of the respective active sites. In solution, both enzymes show a heterogeneous spin population, with the six-coordinated low-spin state being the most populated in the former and the five-coordinated quantum mechanically mixed-spin state in the latter. We ascribe the poor catalytic activity of BsDyP to the presence of a catalytically incompetent six-coordinated low-spin population. The spin populations of the two DyPs are sensitively dependent on the pH, temperature, and physical, i.e., solution versus crystal versus immobilized, state of the enzymes. We observe a redox potential for the Fe(2+)/Fe(3+) couple in BsDyP (-40 mV) at pH 7.6 substantially more positive than those reported for the majority of other peroxidases, including PpDyP (-260 mV). Furthermore, we evaluate the potential of the studied enzymes for biotechnological applications on the basis of electrochemical and spectroelectrochemical data.

  10. Characterization of photosynthetic reaction centers by surface-enhanced resonance Raman scattering

    NASA Astrophysics Data System (ADS)

    Chumanov, George D.; Cotton, Therese M.; Zhou, Chengli; Gaul, Dale; Picorel, Rafael; Seibert, Michael

    1993-06-01

    Surface-enhanced Resonance Raman scattering (SERRS) spectra were obtained for the reaction center complexes of the photosynthetic bacterium Rhodobacter sphaeroides (RC) and from photosystem II (PSII) of spinach, adsorbed on Ag and Au surfaces. These preliminary results demonstrate the considerable potential of this technique for selectively exciting resonance Raman scattering from reaction center components within their distinct absorption bands. Because of the high sensitivity afforded by SERRS, spectra could be measured from a single monolayer of reaction centers adsorbed on a metal surface. The surface-sensitivity provides new information indicating the topology of the PSII reaction center 47 kD light-harvesting protein complex. The activity of the PSII reaction center complex adsorbed on metal surfaces was monitored by photochemical reduction of cyt b-559. Measurement of fluorescence emission was shown to be a new and sensitive method for monitoring the structural and functional integrity of the PSII reaction center complex on the metal surface.

  11. Nonadiabaticity in a Jahn-Teller system probed by absorption and resonance Raman scattering.

    PubMed

    Pae, K; Hizhnyakov, V

    2013-03-14

    A theory of absorption and resonance Raman scattering of impurity centers in crystals with E⊗e-type Jahn-Teller effect in the excited state is presented. The vibronic interaction with non-totally symmetric local or pseudolocal modes and with a continuum of bath modes (phonons) is considered. A number of specific quantum effects, such as the nonadiabaticity-induced enhancement of the Raman scattering at high-energy excitation, the size effect of the final state, the interference of different channels of scattering, the Fermi resonances in the conical intersection, and others, were shown to become apparent in the calculated spectra. The vibronic interaction with phonons essentially determines the structure of the spectra.

  12. 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.

  13. Continuous cell sorting in a flow based on single cell resonance Raman spectra.

    PubMed

    McIlvenna, David; Huang, Wei E; Davison, Paul; Glidle, Andrew; Cooper, Jon; Yin, Huabing

    2016-04-21

    Single cell Raman spectroscopy measures a spectral fingerprint of the biochemistry of cells, and provides a powerful method for label-free detection of living cells without the involvement of a chemical labelling strategy. However, as the intrinsic Raman signals of cells are inherently weak, there is a significant challenge in discriminating and isolating cells in a flowing stream. Here we report an integrated Raman-microfluidic system for continuous sorting of a stream of cyanobacteria, Synechocystis sp. PCC6803. These carotenoid-containing microorganisms provide an elegant model system enabling us to determine the sorting accuracy using the subtly different resonance Raman spectra of microorganism cultured in a (12)C or (13)C carbon source. Central to the implementation of continuous flow sorting is the use of "pressure dividers" that eliminate fluctuations in flow in the detection region. This has enabled us to stabilise the flow profile sufficiently to allow automated operation with synchronisation of Raman acquisition, real-time classification and sorting at flow rates of ca. <100 μm s(-1), without the need to "trap" the cells. We demonstrate the flexibility of this approach in sorting mixed cell populations with the ability to achieve 96.3% purity of the selected cells at a speed of 0.5 Hz.

  14. An Empirical Study on Raman Peak Fitting and Its Application to Raman Quantitative Research.

    PubMed

    Yuan, Xueyin; Mayanovic, Robert A

    2017-10-01

    Fitting experimentally measured Raman bands with theoretical model profiles is the basic operation for numerical determination of Raman peak parameters. In order to investigate the effects of peak modeling using various algorithms on peak fitting results, the representative Raman bands of mineral crystals, glass, fluids as well as the emission lines from a fluorescent lamp, some of which were measured under ambient light whereas others under elevated pressure and temperature conditions, were fitted using Gaussian, Lorentzian, Gaussian-Lorentzian, Voigtian, Pearson type IV, and beta profiles. From the fitting results of the Raman bands investigated in this study, the fitted peak position, intensity, area and full width at half-maximum (FWHM) values of the measured Raman bands can vary significantly depending upon which peak profile function is used in the fitting, and the most appropriate fitting profile should be selected depending upon the nature of the Raman bands. Specifically, the symmetric Raman bands of mineral crystals and non-aqueous fluids are best fit using Gaussian-Lorentzian or Voigtian profiles, whereas the asymmetric Raman bands are best fit using Pearson type IV profiles. The asymmetric O-H stretching vibrations of H2O and the Raman bands of soda-lime glass are best fit using several Gaussian profiles, whereas the emission lines from a florescent light are best fit using beta profiles. Multiple peaks that are not clearly separated can be fit simultaneously, provided the residuals in the fitting of one peak will not affect the fitting of the remaining peaks to a significant degree. Once the resolution of the Raman spectrometer has been properly accounted for, our findings show that the precision in peak position and intensity can be improved significantly by fitting the measured Raman peaks with appropriate profiles. Nevertheless, significant errors in peak position and intensity were still observed in the results from fitting of weak and wide Raman

  15. Surface-enhanced resonance hyper-Raman spectra of bacteriorhodopsin adsorbed on silver colloids

    NASA Astrophysics Data System (ADS)

    Baranov, A. V.; Nabiev, Igor R.

    1991-05-01

    Surface-enhanced resonance hyper-Raman scattering (SERHRS) spectra of bacteriorhodopsin (BRh) located in purple membranes of Halobacterium halobium adsorbed on aggregated hydrosol Ag particles are obtained for the first time. The SERIIR spectra excited by pulse 1064 nm radiation are compared with SERR spectra excited by radiation with doubled frequency (532 nm). The bands corresponding to the BRh57O and M412 forms of Brh are observed in both spectra. The relative intensities of these bands are discussed. 1.

  16. Polarized Raman scattering study of kesterite type Cu2ZnSnS4 single crystals.

    PubMed

    Guc, Maxim; Levcenko, Sergiu; Bodnar, Ivan V; Izquierdo-Roca, Victor; Fontane, Xavier; Volkova, Larisa V; Arushanov, Ernest; Pérez-Rodríguez, Alejandro

    2016-01-18

    A non-destructive Raman spectroscopy has been widely used as a complimentary method to X-ray diffraction characterization of Cu2ZnSnS4 (CZTS) thin films, yet our knowledge of the Raman active fundamental modes in this material is far from complete. Focusing on polarized Raman spectroscopy provides important information about the relationship between Raman modes and CZTS crystal structure. In this framework the zone-center optical phonons of CZTS, which is most usually examined in active layers of the CZTS based solar cells, are studied by polarized resonant and non-resonant Raman spectroscopy in the range from 60 to 500 cm(-1) on an oriented single crystal. The phonon mode symmetry of 20 modes from the 27 possible vibrational modes of the kesterite structure is experimentally determined. From in-plane angular dependences of the phonon modes intensities Raman tensor elements are also derived. Whereas a strong intensity enhancement of the polar E and B symmetry modes is induced under resonance conditions, no mode intensity dependence on the incident and scattered light polarization configurations was found in these conditions. Finally, Lyddane-Sachs-Teller relations are applied to estimate the ratios of the static to high-frequency optic dielectric constants parallel and perpendicular to c-optical axis.

  17. Polarized Raman scattering study of kesterite type Cu2ZnSnS4 single crystals

    NASA Astrophysics Data System (ADS)

    Guc, Maxim; Levcenko, Sergiu; Bodnar, Ivan V.; Izquierdo-Roca, Victor; Fontane, Xavier; Volkova, Larisa V.; Arushanov, Ernest; Pérez-Rodríguez, Alejandro

    2016-01-01

    A non-destructive Raman spectroscopy has been widely used as a complimentary method to X-ray diffraction characterization of Cu2ZnSnS4 (CZTS) thin films, yet our knowledge of the Raman active fundamental modes in this material is far from complete. Focusing on polarized Raman spectroscopy provides important information about the relationship between Raman modes and CZTS crystal structure. In this framework the zone–center optical phonons of CZTS, which is most usually examined in active layers of the CZTS based solar cells, are studied by polarized resonant and non-resonant Raman spectroscopy in the range from 60 to 500 cm‑1 on an oriented single crystal. The phonon mode symmetry of 20 modes from the 27 possible vibrational modes of the kesterite structure is experimentally determined. From in-plane angular dependences of the phonon modes intensities Raman tensor elements are also derived. Whereas a strong intensity enhancement of the polar E and B symmetry modes is induced under resonance conditions, no mode intensity dependence on the incident and scattered light polarization configurations was found in these conditions. Finally, Lyddane-Sachs-Teller relations are applied to estimate the ratios of the static to high-frequency optic dielectric constants parallel and perpendicular to c-optical axis.

  18. Polarized Raman scattering study of kesterite type Cu2ZnSnS4 single crystals

    PubMed Central

    Guc, Maxim; Levcenko, Sergiu; Bodnar, Ivan V.; Izquierdo-Roca, Victor; Fontane, Xavier; Volkova, Larisa V.; Arushanov, Ernest; Pérez-Rodríguez, Alejandro

    2016-01-01

    A non-destructive Raman spectroscopy has been widely used as a complimentary method to X-ray diffraction characterization of Cu2ZnSnS4 (CZTS) thin films, yet our knowledge of the Raman active fundamental modes in this material is far from complete. Focusing on polarized Raman spectroscopy provides important information about the relationship between Raman modes and CZTS crystal structure. In this framework the zone–center optical phonons of CZTS, which is most usually examined in active layers of the CZTS based solar cells, are studied by polarized resonant and non-resonant Raman spectroscopy in the range from 60 to 500 cm−1 on an oriented single crystal. The phonon mode symmetry of 20 modes from the 27 possible vibrational modes of the kesterite structure is experimentally determined. From in-plane angular dependences of the phonon modes intensities Raman tensor elements are also derived. Whereas a strong intensity enhancement of the polar E and B symmetry modes is induced under resonance conditions, no mode intensity dependence on the incident and scattered light polarization configurations was found in these conditions. Finally, Lyddane-Sachs-Teller relations are applied to estimate the ratios of the static to high-frequency optic dielectric constants parallel and perpendicular to c-optical axis. PMID:26776727

  19. Anisotropy of electron-phonon interaction in nanoscale CdSe platelets as seen via off-resonant and resonant Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Cherevkov, S. A.; Fedorov, A. V.; Artemyev, M. V.; Prudnikau, A. V.; Baranov, A. V.

    2013-07-01

    The off-resonant and resonant Raman spectra of optical phonons in colloidal CdSe nanoplatelets (NPLs) with the thickness of 4, 5, and 6 CdSe monolayers are analyzed. These spectra are dominated by SO and LO phonon bands of CdSe whose frequencies are thickness independent in the off-resonant Raman but demonstrate evident thickness dependence similar to that observed for confined optical phonons in CdSe quantum dots in the resonant Raman. The results show that conventional optical phonons propagating along the NPL lateral planes contribute mainly to the off-resonant Raman while confined optical phonons propagating in the perpendicular direction dominate the Raman spectra excited in the resonance with confined exciton transitions of CdSe NPLs. An anisotropic electron-phonon interaction is proposed to be responsible for this effect in the CdSe NPLs. A formation of Cd-S monolayer on the surface of CdSe NPLs treated by thiol-containing ligands is also detected in Raman spectra.

  20. Raman spectroscopy study on the ν1-2ν2 Fermi resonance of liquid carbon disulfide in binary solutions: effect of the weak hydrogen bond formation on the Fermi resonance.

    PubMed

    Li, DongFei; Sun, Shang; Sun, ChengLin; Jiang, XiuLan; Gao, ShuQin; Li, ZuoWei

    2012-10-01

    We have measured the Raman spectra of liquid CS(2) at different volume concentrations in CHCl(3) and CH(2)Cl(2) solutions. With decreasing the volume concentration of CS(2), a noticeable growth in the 2ν(2) band frequency was observed, while the ν(1) band location remained practically unchanged. This asymmetric wavenumber shift phenomenon of the Fermi doublet ν(1) and 2ν(2) of CS(2) has been ascribed to weak, non-conventional hydrogen bonds formed between the CS(2) and the solvent molecules. These weak hydrogen bonds were also responsible for significant decreases in the C-H bond symmetric stretching vibration band frequencies of CHCl(3) and CH(2)Cl(2). The values of the ν(1)-2ν(2) FR parameters of CS(2) in CH(2)Cl(2) and CHCl(3) at different volume concentrations were calculated according to the FR theory. The magnitude of the FR coupling coefficient W of CS(2) increases upon dilution with CH(2)Cl(2) and CHCl(3), indicating that the vibrational anharmonicity is relatively sensitive to variations in the weak hydrogen bonding. Compared with the changing tendencies of Fermi coupling coefficient W of CS(2) in CH(2)Cl(2) and CHCl(3) at different volume concentrations, we discussed the effect of the weak hydrogen bond formation on the FR and the asymmetric wavenumber shift phenomenon of the Fermi doublet ν(1) and 2ν(2) of CS(2).

  1. Resonance Raman spectroscopic measurements delineate the structural changes that occur during tau fibril formation.

    PubMed

    Ramachandran, Gayathri; Milán-Garcés, Erix A; Udgaonkar, Jayant B; Puranik, Mrinalini

    2014-10-21

    The aggregation of the microtubule-associated protein, tau, into amyloid fibrils is a hallmark of neurodegenerative diseases such as the tauopathies and Alzheimer's disease. Since monomeric tau is an intrinsically disordered protein and the polymeric fibrils possess an ordered cross-β core, the aggregation process is known to involve substantial conformational conversion besides growth. The aggregation mechanism of tau in the presence of inducers such as heparin, deciphered using probes such as thioflavin T/S fluorescence, light scattering, and electron microscopy assays, has been shown to conform to ligand-induced nucleation-dependent polymerization. These probes do not, however, distinguish between the processes of conformational conversion and fibril growth. In this study, UV resonance Raman spectroscopy is employed to look directly at signatures of changes in secondary structure and side-chain packing during fibril formation by the four repeat functional domain of tau in the presence of the inducer heparin, at pH 7 and at 37 °C. Changes in the positions and intensities of the amide Raman bands are shown to occur in two distinct stages during the fibril formation process. The first stage of UVRR spectral changes corresponds to the transformation of monomer into early fibrillar aggregates. The second stage corresponds to the transformation of these early fibrillar aggregates into the final, ordered, mature fibrils and during this stage; the processes of conformational conversion and the consolidation of the fibril core occur simultaneously. Delineation of these secondary structural changes accompanying the formation of tau fibrils holds significance for the understanding of generic and tau-specific principles of amyloid assembly.

  2. 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.

  3. 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

  4. Solitons and frequency combs in silica microring resonators: Interplay of the Raman and higher-order dispersion effects

    NASA Astrophysics Data System (ADS)

    Milián, C.; Gorbach, A. V.; Taki, M.; Yulin, A. V.; Skryabin, D. V.

    2015-09-01

    The influence of Raman scattering and higher order dispersions on solitons and frequency comb generation in silica microring resonators is investigated. The Raman effect introduces a threshold value in the resonator quality factor above which the frequency-locked solitons cannot exist, and instead, a rich dynamics characterized by generation of self-frequency-shifting solitons and dispersive waves is observed. A mechanism for broadening the Cherenkov radiation through Hopf instability of the frequency-locked solitons is also reported.

  5. 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.

  6. Black phosphorus edges: a polarized Raman study

    NASA Astrophysics Data System (ADS)

    Ribeiro, H.; Villegas, C.; Bahamon, D.; Castro Neto, A.; de Souza, E.; Rocha, A.; Pimenta, M.; de Matos, C.

    Black phosphorus (BP) has been recently exfoliated down to few-layer thicknesses revealing numerous interesting features such as a tunable direct bandgap. Ever since, demonstrations of BP electronic devices have bloomed, as well as studies of the electric, optical, mechanical and thermal properties of its bulk and few-layer forms. However, the edges of BP crystals have, so far, been poorly characterized, even though the terminations of layered crystals are known to possess a range of interesting properties. In this work, the edges of exfoliated BP flakes are characterized by polarized confocal Raman spectroscopy. We will present experimental Raman spectra at zigzag and armchair edges, as well as density functional theory calculations that explain the peculiarities of the experimental data. Fapesp, INCT/Nanocarbono, Fapemig, CNPq, MackPesquisa, Grid-Unesp, CENAPAD-SP, and NRF.

  7. Synthesis, characterization, Raman, and surface enhanced Raman studies of semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Pan, Yi

    The major contributions and discoveries of the dissertation include: (1) Homogeneous nucleation processes for the formation of nanocrystals can occur at low temperature and do not need to proceed at high temperature to overcome a high energy barrier. Monodisperse PbS quantum dots (QDs) obtained with nucleation and growth at 45°C support this finding. (2) Monodisperse single elemental Se QDs can be produced by simple solution crystallization from TDE (1-tetradecene) or ODE (1-octadecene). (3) TDE is a better non-coordinating solvent compare to ODE. STDE (S dissolved in TDE) and SeTDE (Se dissolved in TDE) are stable reagents with long storage time. They can be used as universal precursors for S-containing and Se-containing QDs. (4) QDs synthesis can be carried out at low temperature and relatively short reaction time using the simple, non-injection, one-pot synthetic method. (5) The one-pot method can be extended for the synthesis of QDs and graphene oxide nanocomposites and metal and graphene oxide nanocomposites. (6) PbCl2-OLA (oleylamine) is a universal system for the synthesis of Pb-chaclogenides QDs. (7) Surface enhanced Raman spectroscopy (SERS) is used to probe both size and wave length dependent quantum confinement effects (QCEs) of PbS QDs. (8) Raman spectroscopy is a powerful tool to elucidate crystal structure of Se nanoclusters with size of 1--2 nm. Semiconductor QDs have attracted considerable attention due to their potential for energy-efficient materials in optoelectronic and solar cell applications. When the radius of a QD is decreased to that of the exciton Bohr radius, the valence and conduction bands are known to split into narrower bands due to QCEs. QCEs are both size and wave length dependent. We have developed, synthesized and characterized a series of Pb-chaclogenide QDs, which all the sizes of the QDs are monodisperse and smaller than their respective exciton Bohr radius, to study the QCEs of these QDs. SERS is used as a crucial tool to

  8. Raman study of opal at high pressure

    NASA Astrophysics Data System (ADS)

    Farfan, G.; Wang, S.; Mao, W. L.

    2011-12-01

    More commonly known for their beauty and lore as gemstones, opals are also intriguing geological materials which may have potential for materials science applications. Opal lacks a definite crystalline structure, and is composed of an amorphous packing of hydrated silica (SiO2) spheroids, which provides us with a unique nano-scaled mineraloid with properties unlike those of other amorphous materials like glass. Opals from different localities were studied at high pressure using a diamond anvil cell to apply pressure and Raman spectroscopy to look at changes in bonding as pressure was increased. We first tested different samples from Virgin Valley, NV, Spencer, ID, Juniper Ridge, OR, and Australia, which contain varying amounts of water at ambient conditions, using Raman spectroscopy to determine if they were opal-CT (semicrystalline cristobalite-trydimite volcanic origin) or opal-A (amorphous sedimentary origin). We then used x-ray diffraction and Raman spectroscopy in a diamond anvil cell to see how their bonding and structure changed under compression and to determine what effect water content had on their high pressure behavior. Comparison of our results on opal to other high pressure studies of amorphous materials like glass has implications from a geological and materials science standpoint.

  9. Studies of Raman scattering in novel disubstituted acetylene polymers

    NASA Astrophysics Data System (ADS)

    Fujii, Akihiko; Shkunov, Maxim N.; Vardeny, Z. Valy; Tada, Kazuya; Yoshino, Katsumi; Teraguchi, Masahiro; Masuda, Toshio

    1997-12-01

    We have studied resonant and non-resonant Raman scattering spectra in thin films of novel disubstituted acetylene polymers such as poly(1-ethyl-2-phenylacetylene) (PEtPA), poly(1-n-hexyl-2-phenylacetylene) (PHxPA) and poly(1-phenyl- 2-p-n-butylphenylacetylene) (PDPA-nBu), which possess high photoluminescence (PL) quantum efficiency. We found that the Raman scattering frequency dispersion is smaller in disubstituted acetylene polymers than in other acetylene polymers, in agreement with many other strongly luminescent polymers. Assuming the model of short polyene conjugation length in these acetylene polymers, we can obtain the conjugation length (N) for each polymer from the respective phonon frequency of the carbon-carbon double bond; we obtained N equals 7 for PDPA-nBu, and N equals 5 or 6 for PHxPA and PEtPA. The related energies of 11Bu and 21Ag can be estimated from these N and are in good agreement with the respective absorption and PL spectra of the various disubstituted polymers.

  10. 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).

  11. 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).

  12. Surface-enhanced resonance Raman scattering spectroscopy applied to phytochrome and its model compounds. 2. Phytochrome and phycocyanin chromophores

    SciTech Connect

    Farrens, D.L.; Holt, R.E.; Rospendowski, B.N.; Song, Pillsoon; Cotton, T.M. )

    1989-12-20

    Surface-enhanced resonance Raman scattering (SERRS) spectra of phytochrome at 77 K are reported. The spectra reveal significant differences between Pr and Pfr forms of phytochrome. SERRS spectra of C-phycocyanin Z,Z,Z- and Z,Z,E-chromopeptide isomers at 77 K are also reported. The phycocyanin chromopeptide studies are used to provide a basis for interpreting the phytochrome SERRS spectra. The spectra indicate that photoisomerization of chromophores from C-phycocyanin chromopeptides (from a Z,Z,Z to a Z,Z,E configuration) is detectable with SERRS.

  13. Applicability of surface-enhanced resonance Raman scattering for the direct discrimination of ballpoint pen inks.

    PubMed

    Seifar, R M; Verheul, J M; Ariese, F; Brinkman, U A; Gooijer, C

    2001-08-01

    In situ surface-enhanced resonance Raman spectroscopy (SERRS) with excitation at 685 nm is suitable for the direct discrimination of blue and black ballpoint pen inks on paper. For black inks, shorter excitation wavelengths can also be used. For blue inks, SERRS at 514.5 and 457.9 nm does not provide adequate discriminative power. At these excitation wavelengths, the SERRS signals of the Methyl Violet derivatives present in inks easily dominate the overall spectrum because of resonance enhancement and preferential interaction with silver sol particles. At 685 nm, this problem is not encountered as the Methyl Violet derivatives do not show resonance enhancement, while other components may still exhibit resonance. Thirteen blue and thirteen black ink lines were examined. For the blue and black inks, on the basis of the 685 nm SERR spectra, eight and six groups of spectra, respectively, could be distinguished. This discrimination largely agrees with information from thin layer chromatography (TLC) experiments, although some differences in group compositions are found. The in situ SERR spectra show good repeatability with regard to the Raman frequencies, band shapes and relative intensities of the spectral bands. However, absolute intensities cannot be used for discrimination purposes.

  14. Redox State of Cytochromes in Frozen Yeast Cells Probed by Resonance Raman Spectroscopy

    PubMed Central

    Okotrub, Konstantin A.; Surovtsev, Nikolay V.

    2015-01-01

    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 ∼1015 times slower at liquid nitrogen temperature than at room temperature. PMID:26636934

  15. 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. Copyright © 2015 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  16. Elucidating Peptide and Protein Structure and Dynamics: UV Resonance Raman Spectroscopy

    PubMed Central

    Oladepo, Sulayman A.; Xiong, Kan; Hong, Zhenmin; Asher, Sanford A.

    2011-01-01

    UV resonance Raman spectroscopy (UVRR) is a powerful method that has the requisite selectivity and sensitivity to incisively monitor biomolecular structure and dynamics in solution. In this perspective, we highlight applications of UVRR for studying peptide and protein structure and the dynamics of protein and peptide folding. UVRR spectral monitors of protein secondary structure, such as the Amide III3 band and the Cα-H band frequencies and intensities can be used to determine Ramachandran Ψ angle distributions for peptide bonds. These incisive, quantitative glimpses into conformation can be combined with kinetic T-jump methodologies to monitor the dynamics of biomolecular conformational transitions. The resulting UVRR structural insight is impressive in that it allows differentiation of, for example, different α-helix-like states that enable differentiating π- and 310- states from pure α-helices. These approaches can be used to determine the Gibbs free energy landscape of individual peptide bonds along the most important protein (un)folding coordinate. Future work will find spectral monitors that probe peptide bond activation barriers that control protein (un)folding mechanisms. In addition, UVRR studies of sidechain vibrations will probe the role of side chains in determining protein secondary, tertiary and quaternary structures. PMID:21379371

  17. Analysis of structure-function relationships in cytochrome c oxidase and its biomimetic analogs via resonance Raman and surface enhanced resonance Raman spectroscopies.

    PubMed

    Weidinger, Inez M

    2015-01-01

    Cytochrome c oxidase (CcO) catalyzes the four electron reduction of molecular oxygen to water while avoiding the formation of toxic peroxide; a quality that is of high relevance for the development of oxygen-reducing catalysts. Resonance Raman spectroscopy has been used since many years as a technique to identify electron transfer pathways in cytochrome c oxidase and to identify the key intermediates in the catalytic cycle. This information can be compared to artificial systems such as modified heme-copper enzymes, molecular heme-copper catalysts or CcO/electrode complexes in order to shed light into the reaction mechanism of these non-natural systems. Understanding the structural commonalities and differences of CcO with its non-natural analogs is of great value for designing efficient oxygen-reducing catalysts. In this review therefore Raman spectroscopic measurements on artificial heme-copper enzymes and model complexes are summarized and compared to the natural enzyme cytochrome c oxidase. This article is part of a Special Issue entitled: Vibrational spectroscopies and bioenergetic systems.

  18. Neurotransmitter measurement with a fiber optic probe using pulsed ultraviolet resonance Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Schulze, H. Georg; Greek, L. Shane; Blades, Michael W.; Bree, Alan V.; Gorzalka, Boris B.; Turner, Robin F. B.

    1997-05-01

    Many techniques have been developed to investigate the chemistry associated with brain activity. These techniques generally fall into two categories: fast techniques with species restricted sensitivity and slow techniques with generally unrestricted species sensitivity. Therefore, a need exists for a fast non-invasive technique sensitive to a wide array of biologically relevant compounds in order to measure chemical brain events in real time. The work presented here describes the progress made toward the development of a novel neurotransmitter probe. A fiber-optic linked Raman and tunable ultraviolet resonance Raman system was assembled with custom designed optical fiber probes. Probes of several different geometries were constructed and their working curves obtained in aqueous mixtures of methyl orange and potassium nitrate to determine the best probe configuration given particular sample characteristics. Using this system, the ultraviolet resonance Raman spectra of some neurotransmitters were measured with a fiber-optic probe and are reported here for the first time. The probe has also been used to measure neurotransmitter secretions obtained from depolarized rat pheochromocytoma cells.

  19. Surface-Enhanced Resonance Raman Scattering Nanostars for High Precision Cancer Imaging

    PubMed Central

    Harmsen, Stefan; Huang, Ruimin; Wall, Matthew A.; Karabeber, Hazem; Samii, Jason M.; Spaliviero, Massimiliano; White, Julie R.; Monette, Sébastien; O’Connor, Rachael; Pitter, Kenneth L.; Sastra, Stephen A.; Saborowski, Michael; Holland, Eric C.; Singer, Samuel; Olive, Kenneth P.; Lowe, Scott W.; Blasberg, Ronald G.; Kircher, Moritz F.

    2015-01-01

    The inability to visualize the true extent of cancers represents a significant challenge in many areas of oncology. The margins of most cancer types are not well demarcated because the cancer diffusely infiltrates the surrounding tissues. Furthermore, cancers may be multifocal and characterized by the presence of microscopic satellite lesions. Such microscopic foci represent a major reason for persistence of cancer, local recurrences, and metastatic spread and are usually impossible to visualize with currently available imaging technologies. An imaging method to reveal the tumor extent is desired clinically and surgically. Here we show the precise visualization of tumor margins, microscopic tumor invasion, and multifocal loco-regional tumor spread using a new generation of surface-enhanced resonance Raman scattering (SERRS) nanoparticles, which are termed here SERRS-nanostars. The SERRS-nanostars feature a star-shaped gold core, a Raman reporter resonant in the near-infrared spectrum, and a primer-free silication method. In mouse models of pancreatic cancer, breast cancer, prostate cancer, and sarcoma, SERRS-nanostars enabled accurate detection of macroscopic malignant lesions as well as microscopic disease, without the need for a targeting moiety. Moreover, the sensitivity (1.5 femtomolar limit of detection under in vivo Raman imaging conditions) of SERRS-nanostars allowed imaging of premalignant lesions of pancreatic and prostatic neoplasias. High sensitivity and broad applicability, in conjunction with their inert gold-silica composition, render SERRS-nanostars a promising imaging agent for more precise cancer imaging and resection. PMID:25609167

  20. Resonance Raman scattering of perovskite-type relaxor ferroelectrics under nonambient conditions

    NASA Astrophysics Data System (ADS)

    de la Flor, G.; Wehber, M.; Rohrbeck, A.; Aroyo, M. I.; Bismayer, U.; Mihailova, B.

    2014-08-01

    Resonance Raman scattering (RRS) of two model perovskite-type (ABO3) relaxor compounds PbSc0.5Ta0.5O3 (PST) and PbSc0.5Nb0.5O3 (PSN) excited with a laser wavelength of 325 nm (3.8 eV) is studied at different temperatures and ambient pressure as well as at high pressures and room temperature (for PST). The origin of the observed RRS is reinspected by applying group-theory analysis of phonons compatible with symmetry-allowed electron transitions in cubic and possible polar and nonpolar rhombohedral ferroic structures. It is shown that the simultaneous enhancement of first- and second-order RRS generated by antisymmetric BO6 bending and stretching modes under resonance conditions when the photon energy is slightly above the energy gap Eg˜3.2eV results exclusively from spatial regions with coherent polar structural distortions. Upon cooling RRS appears in the vicinity of the characteristic temperature T*, and its total intensity significantly increases upon further temperature decrease. The predominate type of BO6 polarity changes from related to difference in B-O bonds to related to distorted O-B-O bond angles. At room temperature and high pressures RRS drops in intensity above the critical pressure of development of long-range antiphase octahedral tilting. However it persists up to 8.3 GPa, which is the highest pressure reached in the experiment, indicating that the high-pressure phase is polar due to the slight BO6 distortions accompanying the tilt order.

  1. 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.

  2. Resonance Raman interrogation of the consequences of heme rotational disorder in myoglobin and its ligated derivatives.

    PubMed

    Rwere, Freeborn; Mak, Piotr J; Kincaid, James R

    2008-12-02

    Resonance Raman spectroscopy is employed to characterize heme site structural changes arising from conformational heterogeneity in deoxyMb and ligated derivatives, i.e., the ferrous CO (MbCO) and ferric cyanide (MbCN) complexes. The spectra for the reversed forms of these derivatives have been extracted from the spectra of reconstituted samples. Dramatic changes in the low-frequency spectra are observed, where newly observed RR modes of the reversed forms are assigned using protohemes that are selectively deuterated at the four methyl groups or at the four methine carbons. Interestingly, while substantial changes in the disposition of the peripheral vinyl and propionate groups can be inferred from the dramatic spectral shifts, the bonds to the internal histidyl imidazole ligand and those of the Fe-CO and Fe-CN fragments are not significantly affected by the heme rotation, as judged by lack of significant shifts in the nu(Fe-N(His)), nu(Fe-C), and nu(C-O) modes. In fact, the apparent lack of an effect on these key vibrational parameters of the Fe-N(His), Fe-CO, and Fe-CN fragments is entirely consistent with previously reported equilibrium and kinetic studies that document virtually identical functional properties for the native and reversed forms.

  3. DNA sequence detection using surface-enhanced resonance Raman spectroscopy in a homogeneous multiplexed assay.

    PubMed

    MacAskill, Alexandra; Crawford, David; Graham, Duncan; Faulds, Karen

    2009-10-01

    Detection of specific DNA sequences is central to modern molecular biology and also to molecular diagnostics where identification of a particular disease is based on nucleic acid identification. Many methods exist, and fluorescence spectroscopy dominates the detection technologies employed with different assay formats. This study demonstrates the use of surface-enhanced resonance Raman scattering (SERRS) to detect specific DNA sequences when coupled with modified SERRS-active probes that have been designed to modify the affinity of double- and single-stranded DNA for the surface of silver nanoparticles resulting in discernible differences in the SERRS which can be correlated to the specific DNA hybridization event. The principle of the assay lies on the lack of affinity of double-stranded DNA for silver nanoparticle surfaces; therefore, hybridization of the probe to the target results in a reduction in the SERRS signal. Use of locked nucleic acid (LNA) residues in the DNA probes resulted in greater discrimination between exact match and mismatches when used in comparison to unmodified labeled DNA probes. Polymerase chain reaction (PCR) products were detected using this methodology, and ultimately a multiplex detection of sequences relating to a hospital-acquired infection, namely, methicillin-resistant Staphylococcus aureus (MRSA), demonstrated the versatility and applicability of this approach to real-life situations.

  4. Surface-enhanced resonance Raman scattering of polyaniline on silver and gold colloids.

    PubMed

    Izumi, Celly M S; Andrade, Gustavo F S; Temperini, Marcia L A

    2008-12-25

    The interaction of emeraldine base (PANI-EB) with silver and gold colloids was probed by using Surface-Enhanced Resonance Raman Scattering (SERRS) at 3 different exciting radiations. Due to the great sensitivity of SERRS technique the detection limit of PANI-EB concentration was ca. 2 x 10(-7) mol L(-1) in Ag and Au colloidal suspensions. The UV-vis-NIR spectra of metal colloids in function of PANI-EB concentrations showed that gold colloids present a higher degree of aggregation than silver colloids. SERRS of PANI-EB on metal colloids allowed the study of the polymeric species formed primarily on the metallic surface. The polymer formed after the adsorption of PANI-EB on metallic nanoparticles is strongly dependent on the nature of the metal colloids. The oxidation of PANI-EB to pernigraniline occurred for silver colloids, while a doping process of PANI-EB on Au nanoparticles was evidenced through the observation of the characteristic SERRS spectrum of emeraldine salt at 1064nm.

  5. 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. © The Author(s) 2016.

  6. Two-dimensional resonance Raman spectroscopy of oxygen- and water-ligated myoglobins.

    PubMed

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

    2016-07-21

    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.

  7. Combining fibre optic Raman spectroscopy and tactile resonance measurement for tissue characterization

    NASA Astrophysics Data System (ADS)

    Candefjord, Stefan; Nyberg, Morgan; Jalkanen, Ville; Ramser, Kerstin; Lindahl, Olof A.

    2010-12-01

    Tissue characterization is fundamental for identification of pathological conditions. Raman spectroscopy (RS) and tactile resonance measurement (TRM) are two promising techniques that measure biochemical content and stiffness, respectively. They have potential to complement the golden standard--histological analysis. By combining RS and TRM, complementary information about tissue content can be obtained and specific drawbacks can be avoided. The aim of this study was to develop a multivariate approach to compare RS and TRM information. The approach was evaluated on measurements at the same points on porcine abdominal tissue. The measurement points were divided into five groups by multivariate analysis of the RS data. A regression analysis was performed and receiver operating characteristic (ROC) curves were used to compare the RS and TRM data. TRM identified one group efficiently (area under ROC curve 0.99). The RS data showed that the proportion of saturated fat was high in this group. The regression analysis showed that stiffness was mainly determined by the amount of fat and its composition. We concluded that RS provided additional, important information for tissue identification that was not provided by TRM alone. The results are promising for development of a method combining RS and TRM for intraoperative tissue characterization.

  8. Study of spin-ordering and spin-reorientation transitions in hexagonal manganites through Raman spectroscopy

    PubMed Central

    Chen, Xiang-Bai; Hien, Nguyen Thi Minh; Han, Kiok; Nam, Ji-Yeon; Huyen, Nguyen Thi; Shin, Seong-Il; Wang, Xueyun; Cheong, S. W.; Lee, D.; Noh, T. W.; Sung, N. H.; Cho, B. K.; Yang, In-Sang

    2015-01-01

    Spin-wave (magnon) scattering, when clearly observed by Raman spectroscopy, can be simple and powerful for studying magnetic phase transitions. In this paper, we present how to observe magnon scattering clearly by Raman spectroscopy, then apply the Raman method to study spin-ordering and spin-reorientation transitions of hexagonal manganite single crystal and thin films and compare directly with the results of magnetization measurements. Our results show that by choosing strong resonance condition and appropriate polarization configuration, magnon scattering can be clearly observed, and the temperature dependence of magnon scattering can be simple and powerful quantity for investigating spin-ordering as well as spin-reorientation transitions. Especially, the Raman method would be very helpful for investigating the weak spin-reorientation transitions by selectively probing the magnons in the Mn3+ sublattices, while leaving out the strong effects of paramagnetic moments of the rare earth ions. PMID:26300075

  9. Study of spin-ordering and spin-reorientation transitions in hexagonal manganites through Raman spectroscopy.

    PubMed

    Chen, Xiang-Bai; Hien, Nguyen Thi Minh; Han, Kiok; Nam, Ji-Yeon; Huyen, Nguyen Thi; Shin, Seong-Il; Wang, Xueyun; Cheong, S W; Lee, D; Noh, T W; Sung, N H; Cho, B K; Yang, In-Sang

    2015-08-24

    Spin-wave (magnon) scattering, when clearly observed by Raman spectroscopy, can be simple and powerful for studying magnetic phase transitions. In this paper, we present how to observe magnon scattering clearly by Raman spectroscopy, then apply the Raman method to study spin-ordering and spin-reorientation transitions of hexagonal manganite single crystal and thin films and compare directly with the results of magnetization measurements. Our results show that by choosing strong resonance condition and appropriate polarization configuration, magnon scattering can be clearly observed, and the temperature dependence of magnon scattering can be simple and powerful quantity for investigating spin-ordering as well as spin-reorientation transitions. Especially, the Raman method would be very helpful for investigating the weak spin-reorientation transitions by selectively probing the magnons in the Mn(3+) sublattices, while leaving out the strong effects of paramagnetic moments of the rare earth ions.

  10. Observation of forbidden phonons, Fano resonance and dark excitons by resonance Raman scattering in few-layer WS2

    NASA Astrophysics Data System (ADS)

    Tan, Qing-Hai; Sun, Yu-Jia; Liu, Xue-Lu; Zhao, Yanyuan; Xiong, Qihua; Tan, Ping-Heng; Zhang, Jun

    2017-09-01

    The optical properties of the two-dimensional (2D) crystals are dominated by tightly bound electron-hole pairs (excitons) and lattice vibration modes (phonons). The exciton-phonon interaction is fundamentally important to understand the optical properties of 2D materials and thus helps to develop emerging 2D crystal based optoelectronic devices. Here, we presented the excitonic resonant Raman scattering (RRS) spectra of few-layer WS2 excited by 11 lasers lines covered all of A, B and C exciton transition energies at different sample temperatures from 4 to 300 K. As a result, we are not only able to probe the forbidden phonon modes unobserved in ordinary Raman scattering, but also can determine the bright and dark state fine structures of 1s A exciton. In particular, we also observed the quantum interference between low-energy discrete phonon and exciton continuum under resonant excitation. Our works pave a way to understand the exciton-phonon coupling and many-body effects in 2D materials.

  11. Pressure Induced Resonance Raman Effects in Shocked Carbon Disulfide

    DTIC Science & Technology

    1989-03-01

    currently underway. The assistance of Paul Bellamy and Jerry Thompson with the experimental work is acknowledged. This work was supported by ONR contract...Renlund, S.A. Sheffiel, and W.M. Trott , ’Time Resolved Infrared Spec- tral Photograph Studies of Shock Induced Chemistry in CS2 ’ pp 237 in Ref. 1 14. N.C

  12. Resonance Raman and theoretical investigation of the photodissociation dynamics of benzamide in S3 state.

    PubMed

    Pei, Ke-Mei; Ma, Yufang; Zheng, Xuming

    2008-06-14

    Resonance Raman spectra were obtained for benzamide in methanol and acetonitrile solutions with excitation wavelengths in resonance with the S(3) state. These spectra indicate that the Franck-Condon region photodissociation dynamics have multidimensional character with the motions mainly along the benzene ring C[Double Bond]C stretch nu(9), the Ph-CO-NH(2) and ring benzene stretch nu(14), the CCH in plane bend nu(17), the Ph-CO-NH(2) stretch and NH(2) rock nu(19), the ring trigonal bend nu(23), and the ring deformation and Ph-CO-NH(2) stretch nu(29). A preliminary resonance Raman intensity analysis was done, and the results were compared to those previously reported for acetophenone to examine the substituent effect. Solvent effect on the short-time photodissociation dynamics of benzamide was also examined. A conical intersection point S(2)S(3) between S(3) and S(2) potential energy surfaces of benzamide was determined by using a complete active space self-consistent field theory computations. The structural differences and similarities between S(3)S(2) point and S(0) were examined, and the results were used to correlate to the Franck-Condon photodissociation dynamics of benzamide in S(3) state.

  13. Normal mode analysis of Pyrococcus furiosus rubredoxin via nuclear resonance vibrational spectroscopy (NRVS) and resonance raman spectroscopy.

    PubMed

    Xiao, Yuming; Wang, Hongxin; George, Simon J; Smith, Matt C; Adams, Michael W W; Jenney, Francis E; Sturhahn, Wolfgang; Alp, Ercan E; Zhao, Jiyong; Yoda, Y; Dey, Abishek; Solomon, Edward I; Cramer, Stephen P

    2005-10-26

    We have used (57)Fe nuclear resonance vibrational spectroscopy (NRVS) to study the Fe(S(cys))(4) site in reduced and oxidized rubredoxin (Rd) from Pyrococcus furiosus (Pf). The oxidized form has also been investigated by resonance Raman spectroscopy. In the oxidized Rd NRVS, strong asymmetric Fe-S stretching modes are observed between 355 and 375 cm(-1); upon reduction these modes shift to 300-320 cm(-1). This is the first observation of Fe-S stretching modes in a reduced Rd. The peak in S-Fe-S bend mode intensity is at approximately 150 cm(-1) for the oxidized protein and only slightly lower in the reduced case. A third band occurs near 70 cm(-1) for both samples; this is assigned primarily as a collective motion of entire cysteine residues with respect to the central Fe. The (57)Fe partial vibrational density of states (PVDOS) were interpreted by normal mode analysis with optimization of Urey-Bradley force fields. The three main bands were qualitatively reproduced using a D(2)(d) Fe(SC)(4) model. A C(1) Fe(SCC)(4) model based on crystallographic coordinates was then used to simulate the splitting of the asymmetric stretching band into at least 3 components. Finally, a model employing complete cysteines and 2 additional neighboring atoms was used to reproduce the detailed structure of the PVDOS in the Fe-S stretch region. These results confirm the delocalization of the dynamic properties of the redox-active Fe site. Depending on the molecular model employed, the force constant K(Fe-S) for Fe-S stretching modes ranged from 1.24 to 1.32 mdyn/A. K(Fe-S) is clearly diminished in reduced Rd; values from approximately 0.89 to 1.00 mdyn/A were derived from different models. In contrast, in the final models the force constants for S-Fe-S bending motion, H(S-Fe-S), were 0.18 mdyn/A for oxidized Rd and 0.15 mdyn/A for reduced Rd. The NRVS technique demonstrates great promise for the observation and quantitative interpretation of the dynamical properties of Fe-S proteins.

  14. Surface-enhanced Raman scattering (SERS) study of anthocyanidins

    NASA Astrophysics Data System (ADS)

    Zaffino, Chiara; Russo, Bianca; Bruni, Silvia

    2015-10-01

    Anthocyanins are an important class of natural compounds responsible for the red, purple and blue colors in a large number of flowers, fruits and cereal grains. They are polyhydroxy- and polymethoxy-derivatives of 2-phenylbenzopyrylium (flavylium) salts, which are present in nature as glycosylated molecules. The aim of the present study is to assess the identification of anthocyanidins, i.e. anthocyanins without the glycosidic moiety, by means of surface-enhanced Raman spectroscopy (SERS), a very chemically-specific technique which is moreover sensitive to subtle changes in molecular structures. These features can lead to elect SERS, among the spectroscopic tools currently at disposal of scientists, as a technique of choice for the identification of anthocyanidins, since: (1) anthocyanidins structurally present the same benzopyrylium moiety and differentiate only for the substitution pattern on their phenyl ring, (2) different species are present in aqueous solution depending on the pH. It will be demonstrated that, while resonance Raman spectra of anthocyanidins are very similar to one another, SER spectra show greater differences, leading to a further step in the identification of such important compounds in diluted solutions by means of vibrational spectroscopy. Moreover, the dependence on the pH of the six most common anthocyanidins, i.e. cyanidin, delphinidin, pelargonidin, peonidin, malvidin and petunidin, is studied. To the best of the authors' knowledge, a complete SERS study of such important molecules is reported in the present work for the first time.

  15. Interpretation of unusual absorption bandwidths and resonance Raman intensities in excited state mixed valence.

    PubMed

    Lockard, Jenny V; Valverde, Guadalupe; Neuhauser, Daniel; Zink, Jeffrey I; Luo, Yun; Weaver, Michael N; Nelsen, Stephen F

    2006-01-12

    Excited state mixed valence (ESMV) occurs in molecules in which the ground state has a symmetrical charge distribution but the excited state possesses two or more interchangeably equivalent sites that have different formal oxidation states. Although mixed valence excited states are relatively common in both organic and inorganic molecules, their properties have only recently been explored, primarily because their spectroscopic features are usually overlapped or obscured by other transitions in the molecule. The mixed valence excited state absorption bands of 2,3-di-p-anisyl-2,3-diazabicyclo[2.2.2]octane radical cation are well-separated from others in the absorption spectrum and are particularly well-suited for detailed analysis using the ESMV model. Excited state coupling splits the absorption band into two components. The lower energy component is broader and more intense than the higher energy component. The absorption bandwidths are caused by progressions in totally symmetric modes, and the difference in bandwidths is caused by the coordinate dependence of the excited state coupling. The Raman intensities obtained in resonance with the high and low energy components differ significantly from those expected based on the oscillator strengths of the bands. This unexpected observation is a result of the excited state coupling and is explained by both the averaging of the transition dipole moment orientation over all angles for the two types of spectroscopies and the coordinate-dependent coupling. The absorption spectrum is fit using a coupled two-state model in which both symmetric and asymmetric coordinates are included. The physical meaning of the observed resonance Raman intensity trends is discussed along with the origin of the coordinate-dependent coupling. The well-separated mixed valence excited state spectroscopic components enable detailed electronic and resonance Raman data to be obtained from which the model can be more fully developed and tested.

  16. Determination of retinal chromophore structure in bacteriorhodopsin with resonance Raman spectroscopy.

    PubMed

    Smith, S O; Lugtenburg, J; Mathies, R A

    1985-01-01

    The analysis of the vibrational spectrum of the retinal chromophore in bacteriorhodopsin with isotopic derivatives provides a powerful "structural dictionary" for the translation of vibrational frequencies and intensities into structural information. Of importance for the proton-pumping mechanism is the unambiguous determination of the configuration about the C13=C14 and C=N bonds, and the protonation state of the Schiff base nitrogen. Vibrational studies have shown that in light-adapted BR568 the Schiff base nitrogen is protonated and both the C13=C14 and C=N bonds are in a trans geometry. The formation of K625 involves the photochemical isomerization about only the C13=C14 bond which displaces the Schiff base proton into a different protein environment. Subsequent Schiff base deprotonation produces the M412 intermediate. Thermal reisomerization of the C13=C14 bond and reprotonation of the Schiff base occur in the M412------O640 transition, resetting the proton-pumping mechanism. The vibrational spectra can also be used to examine the conformation about the C--C single bonds. The frequency of the C14--C15 stretching vibration in BR568, K625, L550 and O640 argues that the C14--C15 conformation in these intermediates is s-trans. Conformational distortions of the chromophore have been identified in K625 and O640 through the observation of intense hydrogen out-of-plane wagging vibrations in the Raman spectra (see Fig. 2). These two intermediates are the direct products of chromophore isomerization. Thus it appears that following isomerization in a tight protein binding pocket, the chromophore cannot easily relax to a planar geometry. The analogous observation of intense hydrogen out-of-plane modes in the primary photoproduct in vision (Eyring et al., 1982) suggests that this may be a general phenomenon in protein-bound isomerizations. Future resonance Raman studies should provide even more details on how bacterio-opsin and retinal act in concert to produce an

  17. 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.

  18. Measurements of vitamin B12 in human blood serum using resonance Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Tsiminis, G.; Schartner, E. P.; Brooks, J. L.; Hutchinson, M. R.

    2016-12-01

    Vitamin B12 (cobalamin and its derivatives) deficiency has been identified as a potential modifiable risk factor for dementia and Alzheimer's disease. Chronic deficiency of vitamin B12 has been significantly associated with an increased risk of cognitive decline. An effective and efficient method for measuring vitamin B12 concentration in human blood would enable ongoing tracking and assessment of this potential modifiable risk factor. In this work we present an optical sensor based on resonance Raman spectroscopy for rapid measurements of vitamin B12 in human blood serum. The measurement takes less than a minute and requires minimum preparation (centrifuging) of the collected blood samples.

  19. Absorption and resonance Raman spectra of Pb2, Pb3 and Pb4 in xenon matrices

    NASA Technical Reports Server (NTRS)

    Stranz, D. D.; Khanna, R. K.

    1980-01-01

    Lead metal was vaporized and trapped in solid xenon at 12K. Electronic absorption and resonance Raman spectra were recorded of the resulting matrix, which was shown to contain Pb2, Pb3, and possibly Pb4 molecular species. The vibrational frequency for Pb2 is determined to be 108/cm for the ground state, with a dissociation energy of 82000/cm. Ad3h symmetry is indicated for the Pb3 species, with nu sub 1=117/cm and nu sub 2 = 96 /cm. The existence of Pb4 is suggested by a fundamental and overtone of 111/cm spacing.

  20. Resonant femtosecond stimulated Raman spectroscopy with an intense actinic pump pulse: Application to conical intersections

    NASA Astrophysics Data System (ADS)

    Rao, B. Jayachander; Gelin, Maxim F.; Domcke, Wolfgang

    2017-02-01

    We theoretically investigate the feasibility of characterizing conical intersections with time-resolved resonant femtosecond stimulated Raman spectroscopy (FSRS) using an intense actinic pump pulse. We perform nonperturbative numerical simulations of FSRS signals for a three-electronic-state two-vibrational-mode model, which is inspired by the S 2 ( π π * )- S 1 ( n π * ) conical intersection in pyrazine. Our results show that moderately strong actinic pulses increase the intensity of vibrational fingerprint lines in FSRS transients. They facilitate the extraction of useful spectroscopic information by enhancing peaks revealing the coupling and tuning modes of the conical intersection.

  1. Surface-enhanced resonance Raman scattering in optical tweezers using co-axial second harmonic generation.

    PubMed

    Jordan, Pamela; Cooper, Jon; McNay, Graeme; Docherty, Frances; Graham, Duncan; Smith, W; Sinclair, Gavin; Padgett, Miles

    2005-05-30

    Silica particles were partially coated with silver, and a suitable chromophore, such that they could be simultaneously trapped within an optical tweezers system, and emit a surface-enhanced resonance Raman scattering (SERRS) response. A standard 1064 nm TEM00 mode laser was used to trap the bead whilst a frequency doubling crystal inserted into the beam gave several microwatts of 532 nm co-linear light to excite the SERRS emission. The con fi guration has clear applications in providing apparatus that can simultaneously manipulate a particle whilst obtaining surface sensitive sensory information.

  2. Surface plasmon resonance and surface-enhanced Raman scattering sensing enabled by digital versatile discs

    NASA Astrophysics Data System (ADS)

    Dou, Xuan; Chung, Pei-Yu; Jiang, Peng; Dai, Jianli

    2012-01-01

    We report the simultaneous achievement of sensitive surface plasmon resonance (SPR) and surface-enhanced Raman scattering (SERS) sensing using digital versatile discs (DVDs). The aluminum-covered data tracks of DVDs can efficiently concentrate local electromagnetic field, resulting in an excellent SPR medium (with sensitivity of ˜850 nm per refractive index unit which is higher than that of most available nanofabricated plasmonic substrates) with a small but measurable SERS enhancement. The SPR sensitivity and the optical spectra, as well as the distribution of electric field amplitude, are simulated using a finite-difference time-domain model. The theoretical predictions agree reasonably well with the experimental results.

  3. Surface-enhanced Raman scattering on nanoshells with tunable surface plasmon resonance.

    PubMed

    Alvarez-Puebla, Ramon A; Ross, Daniel J; Nazri, G-Abbas; Aroca, Ricardo F

    2005-11-08

    Fabrication, characterization, and optical enhancement applications of bimetallic AgAu nanoparticles and nanoshells are reported. Nanoparticles with tunable surface plasmon resonances are synthesized at room temperature and characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, and photon correlation spectroscopy. The collective electron oscillation of the nanoparticles shows a controllable tunability in the 400-990 nm spectral range, in agreement with plasmon absorption calculated using Mie theory, providing an optimum substrate for surface plasmon-assisted enhanced spectroscopy. Surface-enhanced Raman scattering experiments show that the average enhancement factor obtained with nanoshells could be higher than those obtained with silver sols.

  4. Resonant femtosecond stimulated Raman spectroscopy with an intense actinic pump pulse: Application to conical intersections.

    PubMed

    Rao, B Jayachander; Gelin, Maxim F; Domcke, Wolfgang

    2017-02-28

    We theoretically investigate the feasibility of characterizing conical intersections with time-resolved resonant femtosecond stimulated Raman spectroscopy (FSRS) using an intense actinic pump pulse. We perform nonperturbative numerical simulations of FSRS signals for a three-electronic-state two-vibrational-mode model, which is inspired by the S2(ππ(*))-S1(nπ(*)) conical intersection in pyrazine. Our results show that moderately strong actinic pulses increase the intensity of vibrational fingerprint lines in FSRS transients. They facilitate the extraction of useful spectroscopic information by enhancing peaks revealing the coupling and tuning modes of the conical intersection.

  5. Quantum Interference Effects in Resonant Raman Spectroscopy of Single- and Triple-Layer MoTe2 from First-Principles.

    PubMed

    Miranda, Henrique P C; Reichardt, Sven; Froehlicher, Guillaume; Molina-Sánchez, Alejandro; Berciaud, Stéphane; Wirtz, Ludger

    2017-03-02

    We present a combined experimental and theoretical study of resonant Raman spectroscopy in single- and triple-layer MoTe2. Raman intensities are computed entirely from first-principles by calculating finite differences of the dielectric susceptibility. In our analysis, we investigate the role of quantum interference effects and the electron-phonon coupling. With this method, we explain the experimentally observed intensity inversion of the A1(') vibrational modes in triple-layer MoTe2 with increasing laser photon energy. Finally, we show that a quantitative comparison with experimental data requires the proper inclusion of excitonic effects.

  6. In vivo resonant Raman measurement of macular carotenoid pigments in the young and the aging human retina

    NASA Astrophysics Data System (ADS)

    Gellermann, Werner; Ermakov, Igor V.; Ermakova, Maia R.; McClane, Robert W.; Zhao, Da-You; Bernstein, Paul S.

    2002-06-01

    We have used resonant Raman scattering spectroscopy as a novel, noninvasive, in vivo optical technique to measure the concentration of the macular carotenoid pigments lutein and zeaxanthin in the living human retina of young and elderly adults. Using a backscattering geometry and resonant molecular excitation in the visible wavelength range, we measure the Raman signals originating from the single- and double-bond stretch vibrations of the π-conjugated molecule's carbon backbone. The Raman signals scale linearly with carotenoid content, and the required laser excitation is well below safety limits for macular exposure. Furthermore, the signals decline significantly with increasing age in normal eyes. The Raman technique is objective and quantitative and may lead to a new method for rapid screening of carotenoid pigment levels in large populations at risk for vision loss from age-related macular degeneration, the leading cause of blindness in the elderly in the United States.

  7. Binding of bufuralol, dextromethorphan, and 3,4-methylenedioxymethylamphetamine to wild-type and F120A mutant cytochrome P450 2D6 studied by resonance Raman spectroscopy

    SciTech Connect

    Bonifacio, Alois . E-mail: zwan@few.vu.nl

    2006-05-12

    Cytochrome P450 2D6 (CYP2D6) is one of the most important drug-metabolizing enzymes in humans. Resonance Raman data, reported for First time for CYP2D6, show that the CYP2D6 heme is found to be in a six-coordinated low-spin state in the absence of substrates, and it is perturbed to different extents by bufuralol, dextromethorphan, and 3,4-methylenedioxymethylamphetamine (MDMA). Dextromethorphan and MDMA induce in CYP2D6 a significant amount of five-coordinated high-spin heme species and reduce the polarity of its heme-pocket, whereas bufuralol does not. Spectra of the F120A mutant CYP2D6 suggest that Phe{sup 12} is involved in substrate-binding of dextromethorphan and MDMA, being responsible for the spectral differences observed between these two compounds and bufuralol. These differences could be explained postulating a different substrate mobility for each compound in the CYP2D6 active site, consistently with the role previously suggested for Phe{sup 12} in binding dextromethorphan and MDMA.

  8. Resonance enhancement of electronic Raman scattering from nitrogen defect levels in silicon carbide

    NASA Astrophysics Data System (ADS)

    Burton, J. C.; Long, F. H.; Ferguson, I. T.

    1999-08-01

    Electronic Raman scattering from nitrogen defect levels in SiC is seen to be significantly enhanced with excitation by red (633 nm, 1.98 eV) or near-IR (785 nm, 1.58 eV) laser light at room temperature. Four nitrogen peaks are observed in 6H-SiC (380, 430, 510, and 638 cm-1) and three peaks in 4H-SiC (about 400, 530, and 570 cm-1). The peaks in the 4H-SiC spectrum are seen to shift to lower frequency with increasing nominal doping concentration. Raman spectra taken at low temperature in 6H-SiC reveal differences between wafers and Lely grown platelets by the appearance of several additional peaks. The origin of the resonant enhancement is the near-IR absorption band associated with the green color characteristic of n-type SiC. These results demonstrate that the laser wavelength is a key parameter in the characterization of SiC by Raman scattering.

  9. 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.

  10. 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).

  11. Preliminary identification of unicellular algal genus by using combined confocal resonance Raman spectroscopy with PCA and DPLS analysis.

    PubMed

    He, Shixuan; Xie, Wanyi; Zhang, Ping; Fang, Shaoxi; Li, Zhe; Tang, Peng; Gao, Xia; Guo, Jinsong; Tlili, Chaker; Wang, Deqiang

    2017-09-18

    The analysis of algae and dominant alga plays important roles in ecological and environmental fields since it can be used to forecast water bloom and control its potential deleterious effects. Herein, we combine in vivo confocal resonance Raman spectroscopy with multivariate analysis methods to preliminary identify the three algal genera in water blooms at unicellular scale. Statistical analysis of characteristic Raman peaks demonstrates that certain shifts and different normalized intensities, resulting from composition of different carotenoids, exist in Raman spectra of three algal cells. Principal component analysis (PCA) scores and corresponding loading weights show some differences from Raman spectral characteristics which are caused by vibrations of carotenoids in unicellular algae. Then, discriminant partial least squares (DPLS) classification method is used to verify the effectiveness of algal identification with confocal resonance Raman spectroscopy. Our results show that confocal resonance Raman spectroscopy combined with PCA and DPLS could handle the preliminary identification of dominant alga for forecasting and controlling of water blooms. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Raman and AFM study of gamma irradiated plastic bottle sheets

    NASA Astrophysics Data System (ADS)

    Ali, Yasir; Kumar, Vijay; Sonkawade, R. G.; Dhaliwal, A. S.

    2013-02-01

    In this investigation, the effects of gamma irradiation on the structural properties of plastic bottle sheet are studied. The Plastic sheets were exposed with 1.25MeV 60Co gamma rays source at various dose levels within the range from 0-670 kGy. The induced modifications were followed by micro-Raman and atomic force microscopy (AFM). The Raman spectrum shows the decrease in Raman intensity and formation of unsaturated bonds with an increase in the gamma dose. AFM image displays rough surface morphology after irradiation. The detailed Raman analysis of plastic bottle sheets is presented here, and the results are correlated with the AFM observations.

  13. Raman and infrared spectroscopic study of turquoise minerals.

    PubMed

    Čejka, Jiří; Sejkora, Jiří; Macek, Ivo; Malíková, Radana; Wang, Lina; Scholz, Ricardo; Xi, Yunfei; Frost, Ray L

    2015-10-05

    Raman and infrared spectra of three well-defined turquoise samples, CuAl6(PO4)4(OH)8·4H2O, from Lavender Pit, Bisbee, Cochise county, Arizona; Kouroudaiko mine, Faleme river, Senegal and Lynch Station, Virginia were studied, interpreted and compared. Observed Raman and infrared bands were assigned to the stretching and bending vibrations of phosphate tetrahedra, water molecules and hydroxyl ions. Approximate O-H⋯O hydrogen bond lengths were inferred from the Raman and infrared spectra. No Raman and infrared bands attributable to the stretching and bending vibrations of (PO3OH)(2-) units were observed.

  14. Raman and infrared spectroscopic study of turquoise minerals

    NASA Astrophysics Data System (ADS)

    Čejka, Jiří; Sejkora, Jiří; Macek, Ivo; Malíková, Radana; Wang, Lina; Scholz, Ricardo; Xi, Yunfei; Frost, Ray L.

    2015-10-01

    Raman and infrared spectra of three well-defined turquoise samples, CuAl6(PO4)4(OH)8·4H2O, from Lavender Pit, Bisbee, Cochise county, Arizona; Kouroudaiko mine, Faleme river, Senegal and Lynch Station, Virginia were studied, interpreted and compared. Observed Raman and infrared bands were assigned to the stretching and bending vibrations of phosphate tetrahedra, water molecules and hydroxyl ions. Approximate O-H⋯O hydrogen bond lengths were inferred from the Raman and infrared spectra. No Raman and infrared bands attributable to the stretching and bending vibrations of (PO3OH)2- units were observed.

  15. Lipid-cell interactions in human monocytes investigated by doubly-resonant coherent anti-Stokes Raman scattering microscopy

    PubMed Central

    Weeks, Tyler; Schie, Iwan; den Hartigh, Laura J.; Rutledge, John C.; Huser, Thomas

    2011-01-01

    We demonstrate that doubly-resonant coherent anti-Stokes Raman scattering can provide enhanced and highly specific contrast for molecules containing unique Raman-active small molecular groups. This combination provides contrast for molecules that can otherwise be difficult to discriminate by Raman spectroscopy. Here, human monocytes were incubated with either deuterated oleic acid or 17-octadecynoic acid (a fatty acid with an end terminal acetylene group). The carbon-deuterium stretching vibration of the deuterated fatty acid, as well as the unique alkyne stretching vibration of the alkyne-containing fatty acid, were used to provide contrast for these exogenous free fatty acids. The combination of these unique modes with the common aliphatic carbon-hydrogen stretching vibration inherent to all fatty acid allowed for doubly-resonant detection of these unique molecules and enabled us to detect the presence of these lipids in areas within a cell where each molecular resonance by itself did not generate sufficient signal. PMID:21361680

  16. 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.

  17. 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.

  18. Resonance Raman spectrum of the solvated electron in methanol: simulation within a cluster model.

    PubMed

    Neumann, Stefanie; Eisfeld, Wolfgang; Sobolewski, Andrzej L; Domcke, Wolfgang

    2006-05-04

    The microsolvation of the CH(3)OH(2) hypervalent radical in methanol clusters has been investigated by density functional theory. It is shown that the CH(3)OH(2) radical spontaneously decomposes within methanol clusters into protonated methanol and a localized solvated electron cloud. The geometric and electronic structures of these clusters as well as their vibrational frequencies have been characterized. Resonance Raman intensities, associated with the s --> p transition of the unpaired electron, have been estimated for CH(3)OH(2)M(n) (M = CH(3)OH, n = 1-3) clusters. It is shown that with increasing cluster size the simulated spectra converge toward the resonance Raman spectrum of the solvated electron in methanol measured recently by Tauber and Mathies (J. Am. Chem. Soc. 2004, 126, 3414). The results suggest that CH(3)OH(2)M(n) clusters are useful finite-size model systems for the computational investigation of the spectroscopic properties of the solvated electron in liquid methanol.

  19. Solute-solvent intermolecular vibronic coupling as manifested by the molecular near-field effect in resonance hyper-Raman scattering.

    PubMed

    Shimada, Rintaro; Hamaguchi, Hiro-o

    2011-01-21

    Vibronic coupling within the excited electronic manifold of the solute all-trans-β-carotene through the vibrational motions of the solvent cyclohexane is shown to manifest as the "molecular near-field effect," in which the solvent hyper-Raman bands are subject to marked intensity enhancements under the presence of all-trans-β-carotene. The resonance hyper-Raman excitation profiles of the enhanced solvent bands exhibit similar peaks to those of the solute bands in the wavenumber region of 21,700-25,000 cm(-1) (10,850-12,500 cm(-1) in the hyper-Raman exciting wavenumber), where the solute all-trans-β-carotene shows a strong absorption assigned to the 1A(g) → 1B(u) transition. This fact indicates that the solvent hyper-Raman bands gain their intensities through resonances with the electronic states of the solute. The observed excitation profiles are quantitatively analyzed and are successfully accounted for by an extended vibronic theory of resonance hyper-Raman scattering that incorporates the vibronic coupling within the excited electronic manifold of all-trans-β-carotene through the vibrational motions of cyclohexane. It is shown that the major resonance arises from the B-term (vibronic) coupling between the first excited vibrational level (v = 1) of the 1B(u) state and the ground vibrational level (v = 0) of a nearby A(g) state through ungerade vibrational modes of both the solute and the solvent molecules. The inversion symmetry of the solute all-trans-β-carotene is preserved, suggesting the weak perturbative nature of the solute-solvent interaction in the molecular near-field effect. The present study introduces a new concept, "intermolecular vibronic coupling," which may provide an experimentally accessible∕theoretically tractable model for understanding weak solute-solvent interactions in liquid.

  20. Remote-Raman spectroscopic study of minerals under supercritical CO2 relevant to Venus exploration.

    PubMed

    Sharma, Shiv K; Misra, Anupam K; Clegg, Samuel M; Barefield, James E; Wiens, Roger C; Acosta, Tayro E; Bates, David E

    2011-10-01

    The authors have utilized a recently developed compact Raman spectrometer equipped with an 85 mm focal length (f/1.8) Nikon camera lens and a custom mini-ICCD detector at the University of Hawaii for measuring remote Raman spectra of minerals under supercritical CO(2) (Venus chamber, ∼102 atm pressure and 423 K) excited with a pulsed 532 nm laser beam of 6 mJ/pulse and 10 Hz. These experiments demonstrate that by focusing a frequency-doubled 532 nm Nd:YAG pulsed laser beam with a 10× beam expander to a 1mm spot on minerals located at 2m inside a Venus chamber, it is possible to measure the remote Raman spectra of anhydrous sulfates, carbonates, and silicate minerals relevant to Venus exploration during daytime or nighttime with 10s integration time. The remote Raman spectra of gypsum, anhydrite, barite, dolomite and siderite contain fingerprint Raman lines along with the Fermi resonance doublet of CO(2). Raman spectra of gypsum revealed dehydration of the mineral with time under supercritical CO(2) at 423 K. Fingerprint Raman lines of olivine, diopside, wollastonite and α-quartz can easily be identified in the spectra of these respective minerals under supercritical CO(2). The results of the present study show that time-resolved remote Raman spectroscopy with a compact Raman spectrometer of moderate resolution equipped with a gated intensified CCD detector and low power laser source could be a potential tool for exploring Venus surface mineralogy both during daytime and nighttime from a lander. Copyright © 2011 Elsevier B.V. All rights reserved.

  1. Vibrations and reorientations of H2O molecules in [Sr(H2O)6]Cl2 studied by Raman light scattering, incoherent inelastic neutron scattering and proton magnetic resonance.

    PubMed

    Hetmańczyk, Joanna; Hetmańczyk, Lukasz; Migdał-Mikuli, Anna; Mikuli, Edward; Florek-Wojciechowska, Małgorzata; Harańczyk, Hubert

    2014-04-24

    Vibrational-reorientational dynamics of H2O ligands in the high- and low-temperature phases of [Sr(H2O)6]Cl2 was investigated by Raman Spectroscopy (RS), proton magnetic resonance ((1)H NMR), quasielastic and inelastic incoherent Neutron Scattering (QENS and IINS) methods. Neutron powder diffraction (NPD) measurements, performed simultaneously with QENS, did not indicated a change of the crystal structure at the phase transition (detected earlier by differential scanning calorimetry (DSC) at TC(h)=252.9 K (on heating) and at TC(c)=226.5K (on cooling)). Temperature dependence of the full-width at half-maximum (FWHM) of νs(OH) band at ca. 3248 cm(-1) in the RS spectra indicated small discontinuity in the vicinity of phase transition temperature, what suggests that the observed phase transition may be associated with a change of the H2O reorientational dynamics. However, an activation energy value (Ea) for the reorientational motions of H2O ligands in both phases is nearly the same and equals to ca. 8 kJ mol(-1). The QENS peaks, registered for low temperature phase do not show any broadening. However, in the high temperature phase a small QENS broadening is clearly visible, what implies that the reorientational dynamics of H2O ligands undergoes a change at the phase transition. (1)H NMR line is a superposition of two powder Pake doublets, differentiated by a dipolar broadening, suggesting that there are two types of the water molecules in the crystal lattice of [Sr(H2O)6]Cl2 which are structurally not equivalent average distances between the interacting protons are: 1.39 and 1.18 Å. However, their reorientational dynamics is very similar (τc=3.3⋅10(-10) s). Activation energies for the reorientational motion of these both kinds of H2O ligands have nearly the same values in an experimental error limit: and equal to ca. 40 kJ mole(-1). The phase transition is not seen in the (1)H NMR spectra temperature dependencies. Infrared (IR), Raman (RS) and inelastic

  2. Raman spectroscopy of gliomas: an exploratory study

    NASA Astrophysics Data System (ADS)

    Shenoy, Mahesh; Hole, Arti R.; Shridhar, E.; Moiyadi, Aliasgar V.; Krishna, C. Murali

    2014-03-01

    Gliomas are extremely infiltrative type of brain cancers, the borders of which are difficult to locate. Gliomas largely consist of tumors of astrocytic or oligodendroglial lineage. Usually stereotactic surgery is performed to obtain tumor tissue sample. Complete excision of these tumors with preservation of uninvolved normal areas is important during brain tumor surgeries. The present study was undertaken to explore feasibility of classifying abnormal and normal glioma tissues with Raman spectroscopy (RS). RS is a nondestructive vibrational spectroscopic technique, which provides information about molecular composition, molecular structures and molecular interactions in tissue. Postoperated 33 (20-abnormal and 13-normal) gliomas tissue samples of different grades were collected under clinical supervision. Five micron section from tissue sample was used for confirmatory histopathological diagnosis while the remaining tissue was placed on CaF2 window and spectra were acquired using a fiberoptic-probe-coupled HE-785 Raman-spectrometer. Spectral acquisition parameters were laser power-80mW, integration-20s and averaged over 3 accumulations. Spectra were pre-processed and subjected to unsupervised Principal-Component Analysis (PCA) to identify trends of classification. Supervised PC-LDA (Principal-Component-Linear-Discriminant Analysis) was used to develop standard-models using spectra of 12 normal and abnormal specimens each. Leave-one-out crossvalidation yielded classification-efficiency of 90% and 80% for normal and abnormal conditions, respectively. Evaluation with an independent-test data-set comprising of 135 spectra of 9 samples provided sensitivity of 100% and specificity of 70%. Findings of this preliminary study may pave way for objective tumor margin assessment during brain surgery.

  3. PiezoForce and Contact Resonance Microscopy Correlated with Raman Spectroscopy applied to a Non-linear Optical Material and to a Lithium Battery Material

    NASA Astrophysics Data System (ADS)

    Lewis, Aaron; Zeltzer, Gabi; Zinoviev, Oleg; Roth, Michael; Roling, Bernhard; Lewis, Aaron; Dekhter, Rimma

    2014-03-01

    A non-linear optical material (KTP) and a lithium-ion conductive glass ceramic (LICGC) for lithium batteries have been studied with Raman Spectroscopy on-line with Piezo Force and Contact Resonance Microscopies. This is allowed by a unique design of the scanned probe microscopy platform used in these studies and the electrical probes that have been developed that keep the optical axis completely free from above so that such combinations are feasible. The integration allows the investigation of alterations in the strain induced in the chemical structure of the materials as a result of the induction of piezo force. The combination of chemical characterization with both piezo force and contact resonance [1] microscopy allows for the monitoring of structural and ionic changes using Raman scattering correlated with these modalities. In KTP, it has been seen that the largest changes take place in TiO6 octahedral structure symmetric and antisymmetric stretch in the interfaces between the regions of the poling of the structure. In the LICGC, defined Raman changes are observed that are related to the contact resonance frequency. The combination adds considerable insight into both the techniques of Piezo Force Microscopy and Contact Resonance Microscopy.

  4. Metamictization of zircon: Raman spectroscopic study

    NASA Astrophysics Data System (ADS)

    Zhang, Ming; Salje, Ekhard K. H.; Farnan, Ian; Graeme-Barber, Ann; Daniel, Philippe; Ewing, Rodney C.; Clark, Andrew M.; Leroux, Hugues

    2000-02-01

    Raman spectroscopy of radiation-damaged natural zircon samples shows increased line broadening and shifts of phonon frequencies with increasing radiation dose. Stretching and bending frequencies of SiO4 tetrahedra soften dramatically with increasing radiation damage. The frequency shifts can be used to determine the degree of radiation damage. Broad spectral bands related to Si-O stretching vibrations between 900 and 1000 cm-1 were observed in metamict/amorphous zircon. The radiation-dose-independent spectral profiles and the coexistence of this broad background and relative sharp Raman modes in partially damaged samples indicate that these bands are correlated with amorphous domains in zircon. The spectral profiles of metamict zircon suggest that in comparison with silica, the SiO4 tetrahedra are less polymerized in metamict zircon. This study also shows that ZrO2 and SiO2 are not the principal products of metamictization in zircon. No indication of bulk chemical unmixing of zircon into ZrO2 and SiO2 was found in 26 samples with a large variation of radiation damage (maximum dose: 23.5 × 1018 icons/Journals/Common/alpha" ALT="alpha" ALIGN="TOP"/> -events g-1 ). Only one sample showed clearly, in all measured sample areas, extra sharp lines at 146, 260, 312, 460 and 642 cm-1 characteristic of tetragonal ZrO2 . The geological (and possibly artificial heating) history of this sample is not known. It is concluded that radiation damage without subsequent high temperature annealing does not cause unmixing of zircon into constituent oxides.

  5. Semi-quantification of surface-enhanced Raman scattering using a handheld Raman spectrometer: a feasibility study.

    PubMed

    Zheng, Jinkai; Pang, Shintaro; Labuza, Theodore P; He, Lili

    2013-12-07

    The feasibility of utilizing a handheld Raman spectrometer for surface-enhanced Raman scattering detection was evaluated on the pesticide ferbam. A layman's "answer box" was established for semi-quantifying the risk level of ferbam. This study advanced the application of a handheld Raman spectrometer to on-site evaluation of trace amounts of analytes.

  6. Elemental sulfur under high hydrostatic pressure. An up-to-date Raman study

    NASA Astrophysics Data System (ADS)

    Andrikopoulos, K. S.; Gorelli, F. A.; Santoro, M.; Yannopoulos, S. N.

    2013-03-01

    We report a high pressure Raman study of orthorhombic elemental sulfur from ambient pressure to ∼ 25 GPa. Using a near infrared laser and low laser intensity on the scattering volume, we achieve off-resonant conditions up to larger pressures in comparison with previous studies. Raman spectra were recorded over the full spectral range including external (librational, translational) and internal (bond bending and bond stretching) modes. Drastic changes are observed as regards the peak frequencies, relative intensities and band splitting of degenerate modes. The main outcome of the present study is the observation of a "structural" transition at ∼ 16 GPa manifested as slope changes of certain frequencies and sudden relative intensities changes. The present findings are discussed in the context of previous pressure Raman studies and comparison with existing X-ray diffraction as well as ab initio molecular dynamics results is attempted.

  7. Active-site structure, binding and redox activity of the heme–thiolate enzyme CYP2D6 immobilized on coated Ag electrodes: a surface-enhanced resonance Raman scattering study

    PubMed Central

    Bonifacio, Alois; Millo, Diego; Keizers, Peter H. J.; Boegschoten, Roald; Commandeur, Jan N. M.; Vermeulen, Nico P. E.; Gooijer, Cees

    2007-01-01

    Surface-enhance resonance Raman scattering spectra of the heme–thiolate enzyme cytochrome P450 2D6 (CYP2D6) adsorbed on Ag electrodes coated with 11-mercaptoundecanoic acid (MUA) were obtained in various experimental conditions. An analysis of these spectra, and a comparison between them and the RR spectra of CYP2D6 in solution, indicated that the enzyme’s active site retained its nature of six-coordinated low-spin heme upon immobilization. Moreover, the spectral changes detected in the presence of dextromethorphan (a CYP2D6 substrate) and imidazole (an exogenous heme axial ligand) indicated that the immobilized enzyme also preserved its ability to reversibly bind a substrate and form a heme–imidazole complex. The reversibility of these processes could be easily verified by flowing alternately solutions of the various compounds and the buffer through a home-built spectroelectrochemical flow cell which contained a sample of immobilized protein, without the need to disassemble the cell between consecutive spectral data acquisitions. Despite immobilized CYP2D6 being effectively reduced by a sodium dithionite solution, electrochemical reduction via the Ag electrode was not able to completely reduce the enzyme, and led to its extensive inactivation. This behavior indicated that although the enzyme’s ability to exchange electrons is not altered by immobilization per se, MUA-coated electrodes are not suited to perform direct electrochemistry of CYP2D6. Electronic supplementary material The online version of this article (doi:10.1007/s00775-007-0303-1) contains supplementary material, which is available to authorized users. PMID:17899220

  8. A Comparative Study between Carcinoma and Sarcoma Using Raman Spectroscopy

    NASA Astrophysics Data System (ADS)

    Dehghani-Bidgoli, Z.; Baygi, M. H. Miran; Kabir, E.; Malekfar, R.

    2014-01-01

    The purpose of this study was to find discriminating Raman spectral features between two major types of cancer, i.e., carcinoma and sarcoma. To this end, Raman spectra from adenocarcinoma, liposarcoma and fibrosarcoma samples were compared. A Raman system was used for the tissue Raman spectroscopic measurements at 785-nm laser excitation. After pre-processings, the Raman spectra were investigated, in major bands associated with protein and lipids, in the adenocarcinoma, liposarcoma, and fibrosarcoma groups. Principal component analysis and nonnegative matrix factorization were performed for finding most significant features in discriminating the spectra of carcinoma from those of sarcoma samples. The findings of this study show that the lipid content in the sarcoma samples decreases compared with the carcinoma samples. The achieved accuracy in discriminating carcinoma from sarcoma by linear discriminant analysis is 93.75 % and 90.63 % using the first nine principal components and nonnegative matrix factorization analysis, respectively.

  9. [Study on Raman Spectra of Some Animal and Plant Oils].

    PubMed

    Wang, Xiang; Dai, Chang-jian

    2015-04-01

    The spectral characteristics of different kinds of oil, either from plant seeds or animal fat, were studied with Raman spectroscopy. The experimental data were processed with the adaptive iteratively reweighted penalized least squares method to realize baseline correction, and provide evident information about their microscopic world. The spectra were analyzed and compared with each other in three parts: the Raman spectra comparison among different samples of plant oils, the analysis of the animal fat and the comparison between plant oils and the animal fat. The differences among the oils were observed in the analysis, including Raman shift and Raman intensity differences. This study not only yields the spectral basis for distinguishing or recognizing the different edible oils, but also confirms that Raman spectroscopy is an effective tool for identifying different oils.

  10. Raman scattering or fluorescence emission? Raman spectroscopy study on lime-based building and conservation materials

    NASA Astrophysics Data System (ADS)

    Kaszowska, Zofia; Malek, Kamilla; Staniszewska-Slezak, Emilia; Niedzielska, Karina

    2016-12-01

    This work presents an in-depth study on Raman spectra excited with 1064 and 532 nm lasers of lime binders employed in the past as building materials and revealed today as valuable conservation materials. We focus our interest on the bands of strong intensity, which are present in the spectra of all binders acquired with laser excitation at 1064 nm, but absent in the corresponding spectra acquired with laser excitation at 532 nm. We suggest, that the first group of spectra represents fluorescence phenomena of unknown origin and the second true Raman scattering. In our studies, we also include two other phases of lime cycle, i.e. calcium carbonate (a few samples of calcite of various origins) and calcium oxide (quicklime) to assess how structural and chemical transformations of lime phases affect the NIR-Raman spectral profile. Furthermore, we analyse a set of carbonated limewashes and lime binders derived from old plasters to give an insight into their spectral characteristics after excitation with the 1064 nm laser line. NIR-Raman micro-mapping results are also presented to reveal the spatial distribution of building materials and fluorescent species in the cross-section of plaster samples taken from a 15th century chapel. Our study shows that the Raman analysis can help identify lime-based building and conservation materials, however, a caution is advised in the interpretation of the spectra acquired using 1064 nm excitation.

  11. Raman scattering or fluorescence emission? Raman spectroscopy study on lime-based building and conservation materials.

    PubMed

    Kaszowska, Zofia; Malek, Kamilla; Staniszewska-Slezak, Emilia; Niedzielska, Karina

    2016-12-05

    This work presents an in-depth study on Raman spectra excited with 1064 and 532nm lasers of lime binders employed in the past as building materials and revealed today as valuable conservation materials. We focus our interest on the bands of strong intensity, which are present in the spectra of all binders acquired with laser excitation at 1064nm, but absent in the corresponding spectra acquired with laser excitation at 532nm. We suggest, that the first group of spectra represents fluorescence phenomena of unknown origin and the second true Raman scattering. In our studies, we also include two other phases of lime cycle, i.e. calcium carbonate (a few samples of calcite of various origins) and calcium oxide (quicklime) to assess how structural and chemical transformations of lime phases affect the NIR-Raman spectral profile. Furthermore, we analyse a set of carbonated limewashes and lime binders derived from old plasters to give an insight into their spectral characteristics after excitation with the 1064nm laser line. NIR-Raman micro-mapping results are also presented to reveal the spatial distribution of building materials and fluorescent species in the cross-section of plaster samples taken from a 15th century chapel. Our study shows that the Raman analysis can help identify lime-based building and conservation materials, however, a caution is advised in the interpretation of the spectra acquired using 1064nm excitation. Copyright © 2016. Published by Elsevier B.V.

  12. One-dimensional plasmonic hotspots located between silver nanowire dimers evaluated by surface-enhanced resonance Raman scattering

    NASA Astrophysics Data System (ADS)

    Itoh, Tamitake; Yamamoto, Yuko S.; Kitahama, Yasutaka; Balachandran, Jeyadevan

    2017-03-01

    Hotspots of surface-enhanced resonance Raman scattering (SERRS) are localized within 1 nm at gaps or crevices of plasmonic nanoparticle dimers. We demonstrate SERRS hotspots with volumes that are extended in one dimension tens of thousand times compared to standard zero-dimensional hotspots using crevices of plasmonic nanowire dimers. According to the polarization measurements, a plasmon resonance in the direction along the dimer width generates SERRS hotspots. SERRS images show oscillating patterns between edges of the hotspot. The SERRS intensity becomes the strongest at the edges, indicating that Fabry-Perot-type resonance of surface plasmons is involved in the Raman enhancement. These optical properties of the SERRS hotspots are quantitatively reproduced by numerical calculations based on the electromagnetic (EM) mechanism. EM coupling energy between dye molecule excitons and plasmons is evaluated using spectral changes in plasmon resonance reflected in a loss of SERRS activity at the hotspots. The coupling energies are consistent with the calculated EM enhancement factors.

  13. Measurement of nitric oxide concentrations in flames by using electronic-resonance-enhanced coherent anti-Stokes Raman scattering

    NASA Astrophysics Data System (ADS)

    Kulatilaka, Waruna D.; Chai, Ning; Naik, Sameer V.; Laurendeau, Normand M.; Lucht, Robert P.; Kuehner, Joel P.; Roy, Sukesh; Gord, James R.

    2006-11-01

    We have measured nitric oxide (NO) concentrations in flames by using electronic-resonance-enhanced coherent anti-Stokes Raman spectroscopy (ERE-CARS). Visible pump and Stokes beams were tuned to a Q-branch vibrational Raman resonance of NO. A UV probe beam was tuned into resonance with specific rotational transitions in the (v″=1,v‧=0) vibrational band in the A2Σ+-X2Π electronic transition, thus providing a substantial electronic-resonance enhancement of the resulting CARS signal. NO concentrations were measured at levels down to 50 parts in 106 in H2/air flames at atmospheric pressure. NO was also detected in heavily sooting C2H2/air flames at atmospheric pressure with minimal background interference.

  14. Elucidation of chemical reactions by two-dimensional resonance Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Molesky, Brian Paul

    It has been shown for many systems, including photosynthetic complexes, molecule-semiconductor interfaces, and bulk heterojunctions, that interaction between electronic and nuclear dynamics may heavily influence chemical mechanisms. Four-wave-mixing spectroscopies (i.e. transient absorption, two-dimensional spectroscopy) provide some insight into such non-equilibrium processes but are limited by the single "population time" available in these types of experiments. In this dissertation, two-dimensional resonance Raman spectroscopy (2DRR) is developed to obtain new information regarding chemical reactions that possess time coincident electronic and nuclear evolution. These new insights can only be acquired through higher-order techniques possessing two "population times". Specifically, the coherent reaction mechanism in triiodide photodissociation and structural heterogeneity in myoglobin are investigated. All multidimensional spectroscopies have roots in the off-resonant multidimensional Raman techniques developed from the late 1980's to the early 2000's. Throughout their development these experiments were plagued with technical challenges that eventually halted further use. In this dissertation it is shown through rigorous experimental tests that the technical challenges of the past are obviated for 2DRR, which is done under electronically resonant conditions. The key is that under electronic resonance the harmonic character of vibrational modes contributes to the signal. Under off-resonant conditions signal generation depends on much weaker effects. Upon absorption of light ranging from 250 to 500 nm triiodide photodissociates into diiodide and radical iodine on the same time scale as the period of triiodide's symmetric stretch, impulsively initiating coherence in the stretching coordinate of diiodide. In this dissertation, the sensitivity of 2DRR to coherent reaction mechanisms is shown by directly measuring, for the first time, how the nonequilibrium geometry of

  15. Raman spectroscopy in graphene

    NASA Astrophysics Data System (ADS)

    Malard, L. M.; Pimenta, M. A.; Dresselhaus, G.; Dresselhaus, M. S.

    2009-04-01

    Recent Raman scattering studies in different types of graphene samples are reviewed here. We first discuss the first-order and the double resonance Raman scattering mechanisms in graphene, which give rise to the most prominent Raman features. The determination of the number of layers in few-layer graphene is discussed, giving special emphasis to the possibility of using Raman spectroscopy to distinguish a monolayer from few-layer graphene stacked in the Bernal (AB) configuration. Different types of graphene samples produced both by exfoliation and using epitaxial methods are described and their Raman spectra are compared with those of 3D crystalline graphite and turbostratic graphite, in which the layers are stacked with rotational disorder. We show that Resonance Raman studies, where the energy of the excitation laser line can be tuned continuously, can be used to probe electrons and phonons near the Dirac point of graphene and, in particular allowing a determination to be made of the tight-binding parameters for bilayer graphene. The special process of electron-phonon interaction that renormalizes the phonon energy giving rise to the Kohn anomaly is discussed, and is illustrated by gated experiments where the position of the Fermi level can be changed experimentally. Finally, we discuss the ability of distinguishing armchair and zig-zag edges by Raman spectroscopy and studies in graphene nanoribbons in which the Raman signal is enhanced due to resonance with singularities in the density of electronic states.

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

    SciTech Connect

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

    2016-06-06

    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.

  17. A theoretical simulation of the resonant Raman spectroscopy of the H2O⋯Cl2 and H2O⋯Br2 halogen-bonded complexes.

    PubMed

    Franklin-Mergarejo, Ricardo; Rubayo-Soneira, Jesús; Halberstadt, Nadine; Janda, Kenneth C; Apkarian, V Ara

    2016-02-07

    The resonant Raman spectra of the H2O⋯Cl2 and H2O⋯Br2 halogen-bonded complexes have been studied in the framework of a 2-dimensional model previously used in the simulation of their UV-visible absorption spectra using time-dependent techniques. In addition to the vibrational progression along the dihalogen mode, a progression is observed along the intermolecular mode and its combination with the intramolecular one. The relative intensity of the inter to intramolecular vibrational progressions is about 15% for H2O⋯Cl2 and 33% for H2O⋯Br2. These results make resonant Raman spectra a potential tool for detecting the presence of halogen bonded complexes in condensed phase media such as clathrates and ice.

  18. Dual-modality probe intended for prostate cancer detection combining Raman spectroscopy and tactile resonance technology--discrimination of normal human prostate tissues ex vivo.

    PubMed

    Nyberg, M; Jalkanen, V; Ramser, K; Ljungberg, B; Bergh, A; Lindahl, O A

    2015-04-01

    Prostate cancer is the most common cancer for men in the western world. For the first time, a dual-modality probe, combining Raman spectroscopy and tactile resonance technology, has been used for assessment of fresh human prostate tissue. The study investigates the potential of the dual-modality probe by testing its ability to differentiate prostate tissue types ex vivo. Measurements on four prostates show that the tactile resonance modality was able to discriminate soft epithelial tissue and stiff stroma (p < 0.05). The Raman spectra exhibited a strong fluorescent background at the current experimental settings. However, stroma could be discerned from epithelia by integrating the value of the spectral background. Combining both parameters by a stepwise analysis resulted in 100% sensitivity and 91% specificity. Although no cancer tissue was analysed, the results are promising for further development of the instrument and method for discriminating prostate tissues and cancer.

  19. Raman studies of Ball mill synthesized bulk Cu2ZnSnSe4

    NASA Astrophysics Data System (ADS)

    Tiwari, Kunal J.; Prem Kumar D., S.; Mallik, Ramesh Chandra; Malar, P.

    2017-05-01

    Kesterite with chemical formula Cu2ZnSnSe4 (CZTSe) has been synthesized by ball milling followed by annealing and hot pressing. Mechanochemical synthesis was carried out in the presence of process control agent namely toluene under two different milling conditions. Structural and phase evolution during different stages of the synthesis was studied with X-ray diffraction (XRD) and Raman spectroscopy. Near resonant Raman spectrum was obtained by making use of laser wavelength of 488 nm to resolve the presence of secondary ZnSe which otherwise is difficult to conclude with XRD alone. Deconvoluted Raman spectrum confirmed the presence of CZTSe along with secondary phases Cu2SnSe3 (CTSe) and ZnSe. This inference was further confirmed by electron probe micro analysis (EPMA) and wavelength dispersive spectroscopy (WDS) studies.

  20. 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.

  1. 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.

  2. Identification of metalloporphyrins with high sensitivity using graphene-enhanced resonance Raman scattering.

    PubMed

    Kim, Bo-Hyun; Kim, Daechul; Song, Sungho; Park, DongHyuk; Kang, Il-Suk; Jeong, Dae Hong; Jeon, Seokwoo

    2014-03-18

    Graphene-enhanced resonance Raman scattering (GERRS) was performed for the detection of three different metallo-octaethylporphyrins (M-OEPs; M = 2H, FeCl, and Pt) homogeneously thermal vapor deposited on a graphene surface. GERRS of M-OEPs were measured using three different excitation wavelengths, λ(ex) = 405, 532, and 633 nm, and characterized detail vibrational bands for the identification of M-OEPs. The GERRS spectra of Pt-OEP at λ(ex) = 532 nm showed ~29 and ~162 times signal enhancement ratio on graphene and on graphene with Ag nanoclusters, respectively, compared to the spectra from bare SiO2 substrate. This enhancement ratio, however, was varied with M-OEPs and excitation wavelengths. The characteristic peaks and band shapes of GERRS for each M-OEP were measured with high sensitivity (100 pmol of thermal vapor deposited Pt-OEP), and these facilitate the selectively recognition of molecules. Also, the peaks shift and broadening provide the evidence of the interaction between graphene and M-OEPs through the charge transfer and π-orbital interaction. The increase of graphene layer induced the decrease of signal intensity and GERRS effect was almost not observed on the thick graphite flakes. Further experiments with various substrates demonstrated that the interaction of single layer of graphene with molecule is the origin of the Raman signal enhancement of M-OEPs. In this experiment, we proved the graphene is a good alternative substrate of Raman spectroscopy for the selective detection of various metalloporphyrins with high sensitivity.

  3. Surface-enhanced resonance Raman scattering spectroscopy applied to phytochrome and its model compounds. 1. Biliverdin photoisomers

    SciTech Connect

    Holt, R.E.; Farrens, D.L.; Song, Pillsoon; Cotton, T.M. )

    1989-12-20

    The application of surface-enhanced resonance Raman scattering (SERRS) spectroscopy to the analysis of the configuration of biliverdin dimethyl ester (BVDE) is reported. SERRS spectra obtained by adsorption of the compounds onto an electrochemically roughened silver electrode and recorded at 7 K were intense and free of significant photodegradation. The similarity of the SERRS and resonance Raman (RR) spectra obtained under identical conditions suggests that no perturbation of the electronic structure of the BVDE occurs upon interaction with the silver surface, and that the distribution of conformers comprising the BVDE solution is not changed. SERRS spectra of the deuterated and monoprotonated Z,Z,Z isomer are also presented. To investigate the influence of configuration upon the Raman spectrum we have synthesized and purified the E,Z,A, and Z,Z,E isomers of BVDE. Excellent SERRS spectra were obtained from the solutions of the compounds eluted directly from the TLC plates.

  4. Status of miniature integrated UV resonance fluorescence and Raman sensors for detection and identification of biochemical warfare agents

    NASA Astrophysics Data System (ADS)

    Hug, William F.; Bhartia, Rohit; Taspin, Alexandre; Lane, Arthur; Conrad, Pamela; Sijapati, Kripa; Reid, Ray D.

    2005-11-01

    Laser induced native fluorescence (LINF) is the most sensitive method of detection of biological material including microorganisms, virus', and cellular residues. LINF is also a sensitive method of detection for many non-biological materials as well. The specificity with which these materials can be classified depends on the excitation wavelength and the number and location of observation wavelengths. Higher levels of specificity can be obtained using Raman spectroscopy but a much lower levels of sensitivity. Raman spectroscopy has traditionally been employed in the IR to avoid fluorescence. Fluorescence rarely occurs at wavelength below about 270nm. Therefore, when excitation occurs at a wavelength below 250nm, no fluorescence background occurs within the Raman fingerprint region for biological materials. When excitation occurs within electronic resonance bands of the biological target materials, Raman signal enhancement over one million typically occurs. Raman sensitivity within several hundred times fluorescence are possible in the deep UV where most biological materials have strong absorption. Since the Raman and fluorescence emissions occur at different wavelength, both spectra can be observed simultaneously, thereby providing a sensor with unique sensitivity and specificity capability. We will present data on our integrated, deep ultraviolet, LINF/Raman instruments that are being developed for several applications including life detection on Mars as well as biochemical warfare agents on Earth. We will demonstrate the ability to discriminate organic materials based on LINF alone. Together with UV resonance Raman, higher levels of specificity will be demonstrated. In addition, these instruments are being developed as on-line chemical sensors for industrial and municipal waste streams and product quality applications.

  5. 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.; ...

    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

  6. Electronic absorption and resonance Raman spectra of large linear carbon clusters isolated in solid argon.

    PubMed

    Szczepanski, J; Fuller, J; Ekern, S; Vala, M

    2001-03-15

    Neutral and anionic carbon clusters have been generated via a laser-induced graphite-based plasma and deposited in a solid argon matrix. Anionic clusters were formed from neutral clusters by using crossed electron/carbon cluster beams. Thermal annealing (to 36 K) resulted in the aggregation of the smaller carbon species, leading to the formation of long chain neutral and anionic clusters. Spectroscopic measurements in the ultraviolet, visible, near-infrared and infrared regions revealed a series of bands attributable to a homologous set of odd-numbered C5-C29 neutral clusters and even-numbered C6(-)-C36- anionic clusters. Good agreement is found for the band positions of carbon chains containing odd C15-C21 neutrals and even C6(-)-C22- anions, with species previously identified by Maier and coworkers using mass selection or laser vaporization, followed by neon matrix isolation. Resonance Raman frequencies for the neutral C17, C21 and C23 species are shown to be consistent with the above attributions. Density functional theory calculations agree well with the observed bands. It is found that certain low frequency Raman stretching frequencies decrease in a predictable way with increasing chain length. Comparison of the 0(0)0 absorption transitions of the even C18(-)-C36- anionic clusters with the 'unidentified' infrared (UIR) interstellar emission bands suggests that the electronic emission from specific long chain carbon anions may contribute to the some of the UIR bands.

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

    SciTech Connect

    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.; He, Y.; Shen, Z. X.; Yoshida, Y.; Eisaki, H.; Mou, C. Y.; Chen, C. T.; Huang, D. J.

    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, 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.

  8. Analysis of plasmon resonance and surface-enhanced Raman scattering on periodic silver structures

    NASA Astrophysics Data System (ADS)

    Kahl, M.; Voges, E.

    2000-05-01

    Surface plasmon excitation and surface-enhanced Raman scattering (SERS) are investigated for periodic grating-type substrates such as binary silver gratings and silver gratings on silica. Electromagnetic near fields are calculated by an efficient implementation of a Rayleigh-expansion technique for rectangular-groove gratings. Far-field signals of Raman-active molecules adsorbed at the grating surface are determined by application of the Lorentz reciprocity theorem. SERS enhancement factors are considered for different types of gratings and for structures with different dimensions with respect to both the intensity and angular width of the emitted Stokes light. Thus, consideration of plasmon resonance widths leads to optimum structures for periodic SERS substrates if realistic experimental configurations involving a lens for detection are taken into account. For binary silver gratings, optimum grating depths of more than 80 nm are proposed for SERS measurements in a realistic experimental configuration, whereas maximum SERS signals are emitted into a single direction at shallow gratings with depths between 10 nm and 20 nm. Furthermore, silica gratings with isolated silver layers are superior to binary silver gratings. Due to both the large intensity and angular width of the emitted signals, SERS enhancement factors are additionally increased on such structures.

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

    PubMed Central

    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.; He, Y.; Shen, Z. X.; Yoshida, Y.; Eisaki, H.; Mou, C. Y.; Chen, C. T.; Huang, D. J.

    2016-01-01

    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, 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. PMID:26794437

  10. Dispersion of the resonant nonlinear optical susceptibility obtained with femtosecond time-domain coherent anti-Stokes Raman scattering.

    PubMed

    Yang, Shan; Ganikhanov, Feruz

    2013-11-15

    We propose and experimentally demonstrate a method that is capable of resolving both real and imaginary parts of third-order nonlinearity (χ(3)) in the vicinity of Raman resonances. Dispersion of χ(3) can be obtained from a medium probed within microscopic volumes with a spectral resolution of better than 0.10 cm(-1).

  11. 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.

  12. Resonant Raman scattering in Mn:ZnO dilute magnetic semiconductors

    NASA Astrophysics Data System (ADS)

    Gleize, J.; Chikoidze, E.; Dumont, Y.; Rzepka, E.; Gorochov, O.

    2007-07-01

    We report on micro-Raman measurements performed under various visible excitations on wurtzite Zn 1- xMn xO thin films grown by MOCVD, for a wide range of Mn content (0resonantly enhanced by the absorption of the incident laser light by internal transitions of the Mn 2+ ions.

  13. Selective resonance enhancement of Raman scattering intensity in photoinduced nonradiative charge transfer

    NASA Astrophysics Data System (ADS)

    Bairamov, B. Kh.

    2016-04-01

    This paper reports on the formation of complexes consisting of isolated free-standing crystalline semiconductor quantum dots, for example, nc-Si/SiO2, functionalized by short oligonucleotides, for example, the single-stranded system d(20G, 20T). Here, d are deoxyribonucleotides, G and T are guanine and thymine nucleotides, respectively. It has been found that these complexes are unique objects for the elucidation of the specific features in the manifestation of new quantum-size effects in biomacromolecules. It has been demonstrated that the possibility exists of detecting and recording, in such complexes of biomacromolecules, spectrally selective resonance enhancement of Raman scattering intensity in fluctuations of nucleotide molecules due to coherent nonradiative transfer of a photoexcited electron and a hole at the interface of the complex. This dynamic optical imaging of spectral responses can be of applied interest for the development of nanobiophotonic technologies.

  14. 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.

  15. 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

  16. Theoretical analysis of resonant raman scattering: Simulations of lineshapes and excitation profiles

    NASA Astrophysics Data System (ADS)

    Angeloni, Leonardo; Fracassi, Pier Francesco; Della Valle, Raffaele Guido

    1985-04-01

    The steady-state response of a three-level system in the presence of a strong laser field is described with the density operator formalism, in order to derive an analytical expression for the intensity of resonance Raman scattering. The Liouville equation for the density operator is written in quantum form for both the molecular system and the radiation field, making use of the dipole and rotating-wave approximations for the matter-radiation interaction, and of the Markov approximation for the molecular decays. The equation is solved exactly for the laser field, and in perturbative way for the generated field. The results account for power broadening of the generated line. Rabi intensity-dip of the generated signal, and for the excitation profiles in the Franck-Condom approximation.

  17. Detection and imaging of quorum sensing in Pseudomonas aeruginosa biofilm communities by surface-enhanced resonance Raman scattering

    NASA Astrophysics Data System (ADS)

    Bodelón, Gustavo; Montes-García, Verónica; López-Puente, Vanesa; Hill, Eric H.; Hamon, Cyrille; Sanz-Ortiz, Marta N.; Rodal-Cedeira, Sergio; Costas, Celina; Celiksoy, Sirin; Pérez-Juste, Ignacio; Scarabelli, Leonardo; La Porta, Andrea; Pérez-Juste, Jorge; Pastoriza-Santos, Isabel; Liz-Marzán, Luis M.

    2016-11-01

    Most bacteria in nature exist as biofilms, which support intercellular signalling processes such as quorum sensing (QS), a cell-to-cell communication mechanism that allows bacteria to monitor and respond to cell density and changes in the environment. As QS and biofilms are involved in the ability of bacteria to cause disease, there is a need for the development of methods for the non-invasive analysis of QS in natural bacterial populations. Here, by using surface-enhanced resonance Raman scattering spectroscopy, we report rationally designed nanostructured plasmonic substrates for the in situ, label-free detection of a QS signalling metabolite in growing Pseudomonas aeruginosa biofilms and microcolonies. The in situ, non-invasive plasmonic imaging of QS in biofilms provides a powerful analytical approach for studying intercellular communication on the basis of secreted molecules as signals.

  18. Detection and imaging of quorum sensing in Pseudomonas aeruginosa biofilm communities by surface-enhanced resonance Raman scattering

    PubMed Central

    Bodelón, Gustavo; Montes-García, Verónica; López-Puente, Vanesa; Hill, Eric H.; Hamon, Cyrille; Sanz-Ortiz, Marta N.; Rodal-Cedeira, Sergio; Costas, Celina; Celiksoy, Sirin; Pérez-Juste, Ignacio; Scarabelli, Leonardo; Porta, Andrea La; Pérez-Juste, Jorge; Pastoriza-Santos, Isabel

    2016-01-01

    Most bacteria in nature exist as biofilms, which support intercellular signaling processes such as quorum sensing (QS), a cell-to-cell communication mechanism that allows bacteria to monitor and respond to cell density and changes in the environment. Because QS and biofilms are involved in the ability of bacteria to cause disease, there is a need for the development of methods for the non-invasive analysis of QS in natural bacterial populations. Here, by using surface-enhanced resonance Raman scattering spectroscopy, we report rationally designed nanostructured plasmonic substrates for the in-situ, label-free detection of a QS signaling metabolite in growing Pseudomonas aeruginosa biofilms and microcolonies. The in situ, non-invasive plasmonic imaging of QS in biofilms provides a powerful analytical approach for studying intercellular communication on the basis of secreted molecules as signals. PMID:27500808

  19. Effects of quenching on electronic-resonance-enhanced coherent anti-Stokes Raman scattering of nitric oxide

    NASA Astrophysics Data System (ADS)

    Roy, Sukesh; Kulatilaka, Waruna D.; Naik, Sameer V.; Laurendeau, Normand M.; Lucht, Robert P.; Gord, James R.

    2006-09-01

    We investigate the effects of gas-mixture composition on the electronic-resonance-enhanced coherent anti-Stokes Raman scattering (ERE-CARS) signals of nitric oxide (NO). From previous laser-induced fluorescence (LIF) studies, quenching rates are known to change drastically, by factors of 400-800, in mixtures of CO2/O2/N2. The observed ERE-CARS signal remains constant to within 30% whereas LIF signals from NO are predicted to decrease by more than two orders of magnitudes in the same environments. This is very significant for using NO ERE-CARS in high-pressure combustion environments where the electronic quenching rate can vary rapidly as a function of both space and time.

  20. Raman and FT-IR studies of ocular tissues

    NASA Astrophysics Data System (ADS)

    Ozaki, Yukihiro; Mizuno, Aritake

    1991-05-01

    Two examples of Raman and FT-IR studies of the ocular tissues are reviewed in this paper. The first example treats Raman studies on cataract development cataract-related lens hydration and structural changes in the lens proteins monitored in situ by Raman spectroscopy are described. The second example is concerned with FT-IR studies on the ocular tissues contain ing collagen nondestructive identification of Type I and IV collagen in the tissues and their structural differences elucidated by infrared spectroscopy are discussed. 1 .

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

    PubMed

    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 (TTF⊂CBPQT(4+)). 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. 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.

  2. 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.

  3. 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.

  4. Effects of collisions on electronic-resonance-enhanced coherent anti-Stokes Raman scattering of nitric oxide

    NASA Astrophysics Data System (ADS)

    Patnaik, Anil K.; Roy, Sukesh; Gord, James R.; Lucht, Robert P.; Settersten, Thomas B.

    2009-06-01

    A six-level model is developed and used to study the effects of collisional energy transfer and dephasing on electronic-resonance-enhanced coherent anti-Stokes Raman scattering (ERE-CARS) in nitric oxide. The model includes the three levels that are coherently coupled by the three applied lasers as well as three additional bath levels that enable inclusion of the effects of electronic quenching and rotational energy transfer. The density-matrix equations that describe the evolution of the relevant populations and coherences are presented. The parametric dependencies of the ERE-CARS signal on collisional energy transfer and dephasing processes are described in terms of both a steady-state analytical solution and the numerical solutions to the governing equations. In the weak-field limit, the ERE-CARS signal scales inversely with the square of the dephasing rates for the electronic and Raman coherences. In accord with published experimental observations [Roy et al., Appl. Phys. Lett. 89, 104105 (2006)], the ERE-CARS signal is shown to be insensitive to the collisional quenching rate. Parametric dependencies on quenching, rotational energy transfer, and pure electronic dephasing are presented, demonstrating reduced collisional dependence for saturating laser fields.

  5. 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

  6. 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

  7. Spectroscopic and Raman excitation profile studies of 3-benzoylpyridine

    NASA Astrophysics Data System (ADS)

    Sett, Pinaky; Datta, Shirsendu; Chowdhury, Joydeep; Ghosh, Manash; Mallick, Prabal Kumar

    2017-03-01

    In the present work IR, UV absorption and Raman spectra including Raman excitation profiles and structure of 3-benzoyl pyridine have been investigated. Detailed studies on the vibrational and electronic properties of the molecule have been carried out. All these studies are aided with valuable quantum chemical calculations. The structural changes encountered on excitation to the low lying excited states have been investigated. Theoretical profiles determined by the sum-over-states method based on pertinent Franck-Condon and Herzberg-Teller terms have satisfactorily simulated the experimentally measured relative Raman intensities and these are also in compliance with the structural changes and potential energy distributions.

  8. Raman scattering studies of pollutant systems.

    NASA Technical Reports Server (NTRS)

    Schwiesow, R. L.

    1971-01-01

    Results and techniques for laboratory measurements of Raman scattering cross sections and depolarization ratios of atmospheric gases as a function of the incident photon energy are discussed. Referred to N2, the cross section of H2O changes by a factor of 2 as the incident photon energy is changed by 5%. Less striking results are obtained for SO2, NO and other atmospheric gases. Tentative results are given for spectral features of scattering from polluted air-water interfaces. Raman lidar is assessed as a potentially useful aid in remote sensing of atmospheric and water-borne pollution distributions at least in near-source concentrations.

  9. Raman spectroscopic study of reaction dynamics

    NASA Astrophysics Data System (ADS)

    MacPhail, R. A.

    1990-12-01

    The Raman spectra of reacting molecules in liquids can yield information about various aspects of the reaction dynamics. The author discusses the analysis of Raman spectra for three prototypical unimolecular reactions, the rotational isomerization of n-butane and 1,2-difluoroethane, and the barrierless exchange of axial and equatorial hydrogens in cyclopentane via pseudorotation. In the first two cases the spectra are sensitive to torsional oscillations of the gauche conformer, and yield estimates of the torsional solvent friction. In the case of cyclopentane, the spectra can be used to discriminate between different stochastic models of the pseudorotation dynamics, and to determine the relevant friction coefficients.

  10. Raman structural studies of the nickel electrode

    NASA Technical Reports Server (NTRS)

    Cornilsen, Bahne C.

    1994-01-01

    The objectives of this investigation have been to define the structures of charged active mass, discharged active mass, and related precursor materials (alpha-phases), with the purpose of better understanding the chemical and electrochemical reactions, including failure mechanisms and cobalt incorporation, so that the nickel electrode may be improved. Although our primary tool has been Raman spectroscopy, the structural conclusions drawn from the Raman data have been supported and augmented by three other analysis methods: infrared spectroscopy, powder X-ray Diffraction (XRD), and x-ray absorption spectroscopy (in particular EXAFS, Extended X-ray Absorption Fine Structure spectroscopy).

  11. Symmetry-dependent exciton-phonon coupling in 2D and bulk MoS2 observed by resonance Raman scattering.

    PubMed

    Carvalho, Bruno R; Malard, Leandro M; Alves, Juliana M; Fantini, Cristiano; Pimenta, Marcos A

    2015-04-03

    This work describes a resonance Raman study performed on samples with one, two, and three layers (1L, 2L, 3L), and bulk MoS2, using more than 30 different laser excitation lines covering the visible range, and focusing on the intensity of the two most pronounced features of the Raman scattering spectrum of MoS2 (E2g(1) and A1g bands). The Raman excitation profiles of these bands were obtained experimentally, and it is found that the A1g feature is enhanced when the excitation laser is in resonance with A and B excitons of MoS2, while the E2g1 feature is shown to be enhanced when the excitation laser is close to 2.7 eV. We show from the symmetry analysis of the exciton-phonon interaction that the mode responsible for the E2g(1) resonance is identified as the high energy C exciton recently predicted [D. Y. Qiu, F. H. da Jornada, and S. G. Louie, Phys. Rev. Lett. 111, 216805 (2013)].

  12. Feasibility study of a Raman spectroscopic route to drug detection

    NASA Astrophysics Data System (ADS)

    Wróbel, Maciej S.; Siddhanta, Soumik; Jedrzejewska-Szczerska, Małgorzata; Smulko, Janusz; Barman, Ishan

    2017-02-01

    We present an surface-enhanced Raman spectroscopy (SERS) approach for detection of drugs of abuse in whole human blood. We utilize a near infrared laser with 830 nm excitation wavelength in order to reduce the influence of fluorescence on the spectra of blood. However, regular plasmon resonance peak of plasmonic nanoparticles, such as silver or gold fall in a much lower wavelength regime about 400 nm. Therefore, we have shifted the plasmon resonance of nanoparticles to match that of an excitation laser wavelength, by fabrication of the silver-core gold-shell nanoparticles. By combining the laser and plasmon resonance shift towards longer wavelengths we have achieved a great reduction in background fluorescence of blood. Great enhancement of Raman signal coming solely from drugs was achieved without any prominent lines coming from the erythrocytes. We have applied chemometric processing methods, such as Principal Component Analysis (PCA), to detect the elusive differences in the Raman bands which are specific for the investigated drugs. We have achieved good classification for the samples containing particular drugs (e.g., butalbital, α-hydroxyalprazolam). Furthermore, a quantitative analysis was carried out to assess the limit of detection (LOD) using Partial Least Squares (PLS) regression method. In conclusion, our LOD values obtained for each class of drugs was competitive with the gold standard GC/MS method.

  13. A comparative study of Raman enhancement in capillaries

    NASA Astrophysics Data System (ADS)

    Eftekhari, Fatemeh; Irizar, Juan; Hulbert, Laila; Helmy, Amr S.

    2011-06-01

    This work reports on the comparative studies of Raman enhancement in liquid core waveguides (LCWs). The theoretical considerations that describe Raman enhancement in LCWs is adapted to analyze and compare the performance of hollow core photonic crystal fibers (HCPCFs) to conventional Teflon capillary tubes. The optical losses in both platforms are measured and used to predict their performance for different lengths. The results show that for an optimal waveguide length, two orders of magnitude enhancement in the Raman signal can be achieved for aqueous solutions using HCPCFs. This length, however, cannot be achieved using normal capillary effects. By integrating the interface of the fluidic pump and the HCPCF into a microfluidic chip, we are able to control fluid transport and fill longer lengths of HCPCFs regardless of the viscosity of the sample. The long-term stability and reproducibility of Raman spectra attained through this platform are demonstrated for naphthalenethiol, which is a well-studied organic compound. Using the HCPCF platform, the detection limit of normal Raman scattering in the range of micro-molars has been achieved. In addition to the higher signal-to-noise ratio of the Raman signal from the HCPCF-platform, more Raman modes of naphthalenethiol are revealed using this platform.

  14. Probing Soluble Guanylate Cyclase Activation by CO and YC-1 using Resonance Raman Spectroscopy†

    PubMed Central

    Ibrahim, Mohammed; Derbyshire, Emily R.; Marletta, Michael A.; Spiro, Thomas G.

    2010-01-01

    Soluble guanylate cyclase (sGC) is weakly activated by CO but is significantly activated by the binding of YC-1 to the sGC-CO complex. In this report resonance Raman (RR) spectroscopy was used to study selected sGC variants. Addition of YC-1 to the sGC-CO complex alters the intensity pattern of RR bands assigned to the vinyl and propionate heme substituents, suggesting changes in the tilting of the pyrrole rings to which they are attached. YC-1 also shifts the RR intensity of the νFeC and νCO bands from 473 and 1985 cm−1 to 487 and 1969 cm−1, respectively, and induces an additional νFeC band, at 521 cm−1, assigned to 5-coordinate heme-CO. Site-directed variants in the proximal heme pocket (P118A) or in the distal heme pocket (V5Y and I149Y) reduce the extent of YC-1 activation, along with the 473 cm−1 band intensity. These lower activity sGC variants display another νFeC band at 493 cm−1 which is insensitive to YC-1 addition and is attributed to protein that cannot be activated by the allosteric activator. The results are consistent with a model in which YC-1 binding to sGC-CO results in a conformational change that activates the protein. Specifically, YC-1 binding alters the heme geometry via peripheral non-bonded contacts, and also relieves an intrinsic electronic effect that diminishes FeCO backbonding in the native, YC-1 responsive protein. This electronic effect might involve neutralization of the heme propionates via H-bond contacts, or negative polarization by a distal cysteine residue. YC-1 binding also strains the Fe-histidine bond, leading to a population of 5-coordinate sGC-CO in addition to a conformationally distinct population of 6-coordinate sGC-CO. The loss of YC-1 activation in the sGC variants might involve a weakening of the heme-protein contacts which are thought to be critical to a YC-1-induced conformational change. PMID:20353168

  15. Off Resonance Surface Enhanced Raman Spectroscopy from Gold Nanorod Suspensions as a Function of Aspect Ratio: Not What We Thought

    PubMed Central

    Sivapalan, Sean T.; DeVetter, Brent M.; Yang, Timothy K.; van Dijk, Thomas; Schulmerich, Matthew V.; Carney, P. Scott; Bhargava, Rohit; Murphy, Catherine Jones

    2013-01-01

    The design of nanoparticles for surface enhanced Raman scattering (SERS) within suspensions is more involved than simply maximizing the local field enhancement. The enhancement at the nanoparticle surface and the extinction of both the incident and scattered light during propagation act in concert to determine the observed signal intensity. Here we explore these critical aspects of signal generation and propagation through experiment and theory. We synthesized gold nanorods of six different aspect ratios in order to obtain longitudinal surface plasmon resonances that incrementally spanned 600-800 nm. The Raman reporter molecule methylene blue was trap-coated near the surface of each nanorod sample, generating SERS spectra, which were used to compare Raman signals. The average number of reporter molecules per nanorod was quantified against known standards using electrospray ionization liquid chromatography mass spectrometry. The magnitude of the observed Raman signal is reported for each aspect ratio along with the attenuation due to extinction in suspension. The highest Raman signal was obtained from the nanorod suspension with a plasmon resonance blue-shifted from the laser excitation wavelength. This finding is in contrast to SERS measurements obtained from molecules dried onto the surface of roughened or patterned metal substrates where the maximum observed signal is near or red-shifted from the laser excitation wavelength. We explain these results as a competition between SERS enhancement and extinction, at the excitation and scattered wavelengths, on propagation through the sample. PMID:23438342

  16. Dispersion of electron-phonon resonances in one-layer graphene and its demonstration in micro-Raman scattering.

    PubMed

    Strelchuk, V V; Nikolenko, A S; Gubanov, V O; Biliy, M M; Bulavin, L A

    2012-11-01

    In the present work, we used Raman spectroscopy as sensitive tool for characterization of dispersion of electron-phonon resonances in one-layer graphene. We analyzed Stokes and anti-Stokes components of the Raman spectra to investigate the temperature dependence of the graphene G-band on the power of exciting radiation. Appearance and drastic intensity increase of zone-edge D-like modes caused by introduction of structural defects and/or deformations in the graphene layer were observed in the Raman spectra at high powers of excitation. We investigated phonon dispersion of one-layer graphene for iTO phonon branch at K point along K-M direction, which is involved in double-resonance Raman scattering. Raman dispersion slope of D-band is in good agreement with results of theoretical calculations based on the Green's functions approach based on the screened electron-electron interaction. Deviation of the experimental iTO phonon frequency from the linear dependence on excitation energy was observed at excitation E(exc) = 3.81 eV. Self-consistent classification of phonon states according to the symmetry for all dispersion branches of one-layer graphene was carried out.

  17. Resonance Raman spectroscopy and quantum-chemical calculations of push-pull molecules: 4-hydroxy-4'-nitroazobenzene and its anion.

    PubMed

    Ando, Rômulo A; Rodríguez-Redondo, José L; Sastre-Santos, A; Fernandez-Lazaro, Fernando; Azzellini, Gianluca C; Borin, Antonio C; Santos, Paulo S

    2007-12-27

    The deprotonation of the push-pull molecule 4-hydroxy-4'-nitroazobenzene leads to a substantial variation in the charge distribution over the donor and acceptor moieties in the D-pi-azo-pi-A system. The extra charge stabilizes the excited state, leading to a drastic red shift of ca. 100 nm in the lambda max of the electronic transition and consequently causes significant changes in the resonance Raman enhancement profiles. In the neutral species the chromophore involves several modes, as nu(CN), nu(NN), and nu s(NO2), while in the anion the selective enhancement of the nu s(NO2) and nu(CO-) modes indicates a greater geometric variation of the NO2 and CO- moieties in the resonant excited electronic state. The interpretation of the electronic transitions and the vibrational assignment are supported by quantum-mechanical calculations, allowing a consistent analysis of the enhancement patterns observed in the resonance Raman spectra.

  18. Effects of Ni-coating on ZnO nanowires: A Raman scattering study

    NASA Astrophysics Data System (ADS)

    Filippov, S.; Wang, X. J.; Devika, M.; Koteeswara Reddy, N.; Tu, C. W.; Chen, W. M.; Buyanova, I. A.

    2013-06-01

    Structural properties of ZnO/Ni core/shell nanowires (NWs) are studied in detail by means of Raman spectroscopy. It is shown that formation of the Ni shell leads to passivation of surface states responsible for the observed enhanced intensity of the A1(LO) Raman mode of the bare ZnO NWs. It also causes appearance of 490 cm-1 and 710 cm-1 modes that are attributed to local vibrational modes of a defect/impurity (or defects/impurities). This defect is concluded to be preferably formed in annealed ZnO/Ni NWs and is unlikely to contain a Ni atom, as the same Raman modes were also reported for the Ni-free ZnO nanostructures. From our resonant Raman studies, we also show that the ZnO/Ni core/shell NWs exhibit an enhanced Raman signal with a multiline structure involving A1(LO). This observation is attributed to combined effects of an enhanced Fröhlich interaction at the ZnO/Ni heterointerface and coupling of the scattered light with local surface plasmons excited in the Ni shell. The plasmonic effect is also suggested to allow detection of carbon-related species absorbed at the surface of a single ZnO/Ni NW, promising for applications of such structures as efficient nano-sized gas sensors.

  19. Raman study of magnetic phase transitions of hexagonal manganites

    NASA Astrophysics Data System (ADS)

    Nam, Ji-Yeon; Hien, Nguyen T. M.; Huyen, Nguyen T.; Han, Kiok; Chen, Xiang-Bai; Cheong, S. W.; Lee, D.; Noh, T. W.; Sung, N. H.; Cho, B. K.; Yang, In-Sang

    2014-03-01

    Results of Raman studies of magnetic phase transitions of hexagonal LuMnO3 single crystal and HoMnO3 thin films are compared directly with the results of magnetic measurements. Our results show that the temperature dependent Raman study of magnon scattering provides a simple and accurate method for investigating magnetic phase transitions, especially in HoMnO3 thin films. In single crystal, our optical method provides results as good as magnetization measurements.

  20. Evidence for the 2B1-2A1 electronic transition in chlorine dioxide from resonance Raman depolarization ratios

    NASA Astrophysics Data System (ADS)

    Reid, Philip J.; Esposito, Anthony P.; Foster, Catherine E.; Beckman, Robert A.

    1997-11-01

    The resonance Raman depolarization ratios of chlorine dioxide (OClO) dissolved in cyclohexane are measured and analyzed to establish the existence of a 2A1 excited state that is nearly degenerate with the optically stronger, 2A2 excited state. The depolarization ratio of the symmetric stretch fundamental transition is measured at several excitation wavelengths spanning the lowest-energy electronic transition centered at ˜360 nm. The depolarization ratio of this transition reaches a maximum value of 0.25±0.04 directly on resonance suggesting that scattered intensity is not derived from a single excited state. The depolarization ratios are modeled utilizing the time-dependent formalism for Raman scattering. This analysis demonstrates that the observed Raman depolarization ratios are derived from contributions of two excited states of 2A1 and 2A2 symmetry to the observed scattering. The results presented here support the emerging picture of OClO excited-state reaction dynamics in which photoexcitation to the 2A2 excited state is followed by internal conversion from this state to the 2A1 surface. Both the role of the 2A1 state in the photochemistry of OClO and the importance of this state in modeling resonance Raman intensities are discussed.

  1. Perturbative theory and modeling of electronic-resonance-enhanced coherent anti-Stokes Raman scattering spectroscopy of nitric oxide

    NASA Astrophysics Data System (ADS)

    Kuehner, Joel P.; Naik, Sameer V.; Kulatilaka, Waruna D.; Chai, Ning; Laurendeau, Normand M.; Lucht, Robert P.; Scully, Marlan O.; Roy, Sukesh; Patnaik, Anil K.; Gord, James R.

    2008-05-01

    A theory is developed for three-laser electronic-resonance-enhanced (ERE) coherent anti-Stokes Raman scattering (CARS) spectroscopy of nitric oxide (NO). A vibrational Q-branch Raman polarization is excited in the NO molecule by the frequency difference between visible Raman pump and Stokes beams. An ultraviolet probe beam is scattered from the induced Raman polarization to produce an ultraviolet ERE-CARS signal. The frequency of the ultraviolet probe beam is selected to be in electronic resonance with rotational transitions in the AΣ+2←XΠ2 (1,0) band of NO. This choice results in a resonance between the frequency of the ERE-CARS signal and transitions in the (0,0) band. The theoretical model for ERE-CARS NO spectra has been developed in the perturbative limit. Comparisons to experimental spectra are presented where either the probe laser was scanned with fixed Stokes frequency or the Stokes laser was scanned with fixed probe frequency. At atmospheric pressure and an NO concentration of 100ppm, good agreement is found between theoretical and experimental spectral peak locations and relative intensities for both types of spectra. Factors relating to saturation in the experiments are discussed, including implications for the theoretical predictions.

  2. Vibrationally resonant imaging of a single living cell by supercontinuum-based multiplex coherent anti-Stokes Raman scattering microspectroscopy

    NASA Astrophysics Data System (ADS)

    Kano, Hideaki; Hamaguchi, Hiro-O.

    2005-02-01

    Supercontinuum-based multiplex coherent anti-Stokes Raman scattering (CARS) microspectroscopy has been applied to vibrational imaging of a living fission yeast cell. We have successfully extracted only a vibrationally resonant CARS image from a characteristic spectral profile in the C-H stretching vibrational region. Using our simple but sensitive analysis, the vibrational contrast is significantly improved in comparison with a CARS imaging at a fixed Raman shift. The CARS image of a living yeast cell indicates several areas at which the signal is remarkably strong. They are considered to arise from mitochondria.

  3. Strong forward-backward asymmetry of stimulated Raman scattering in lithium-niobate-based whispering gallery resonators.

    PubMed

    Leidinger, M; Sturman, B; Buse, K; Breunig, I

    2016-06-15

    We show experimentally and prove theoretically that the pump-power thresholds of stimulated Raman scattering (SRS) in lithium-niobate-based whispering gallery resonators (WGRs) are strongly different for the signal waves propagating in the backward and forward directions with respect to the pump wave. This feature is due to a strong polaritonic effect. It leads to a cascade of alternating forward-backward Raman lines with increasing pump power. The measured polarization and spectral properties of SRS are in good agreement with theory. Similar properties have to be inherent in other WGRs made of polar crystals.

  4. Probing high-pressure phase transitions in Ti-based perovskite-type ferroelectrics using visible resonance Raman spectroscopy.

    PubMed

    Fraysse, Guillaume; Rouquette, Jérôme; Haines, Julien; Bornand, Véronique; Papet, Philippe; Pereira, Altaïr Soria

    2012-12-03

    We report unprecedented dramatic changes in the 647.1 nm Raman signal of PbZr(0.6)Ti(0.4)O(3) occurring in the same pressure ranges as the critical pressures of the antiferrodistortive and ferroelectric-paraelectric phase transitions. This huge decrease in intensity of both the Raman modes and the background, observed for both pressure transmitting media used (glycerol or 4:1 methanol ethanol mixture), is shown to originate from the two-step loss of a resonance Raman effect and the concomitant fluorescence. Changes in the local titanium environment (first with the onset of octahedral tilting and then with the removal of polar cation displacements) alter the electronic band structure and modify the resonance conditions. Furthermore, the optimal resonance conditions are found to be particularly narrow, as shown by the fluorescence spectrum of PbZr(0.6)Ti(0.4)O(3) at atmospheric pressure characterized by the presence of a very well-defined sharp peak (fwhm = 8 nm) centered around 647.1 nm. These results thus demonstrate that visible resonance Raman spectroscopy can be used as a quick and efficient technique for probing phase transitions in PbZr(1-x)Ti(x)O(3) (PZT) and other technologically important perovskite-type materials such as PMN-xPT, PZN-xPT relaxors, lead free piezoelectrics, and ferroelectric nanopowders. This technique appears also a good alternative to UV Raman spectroscopy for probing the polar order at the nanoscale in ultrathinfilms and superlattices.

  5. [Laser Raman Spectroscopy and Its Application in Gas Hydrate Studies].

    PubMed

    Fu, Juan; Wu, Neng-you; Lu, Hai-long; Wu, Dai-dai; Su, Qiu-cheng

    2015-11-01

    Gas hydrates are important potential energy resources. Microstructural characterization of gas hydrate can provide information to study the mechanism of gas hydrate formation and to support the exploitation and application of gas hydrate technology. This article systemly introduces the basic principle of laser Raman spectroscopy and summarizes its application in gas hydrate studies. Based on Raman results, not only can the information about gas composition and structural type be deduced, but also the occupancies of large and small cages and even hydration number can be calculated from the relative intensities of Raman peaks. By using the in-situ analytical technology, laser Raman specstropy can be applied to characterize the formation and decomposition processes of gas hydrate at microscale, for example the enclathration and leaving of gas molecules into/from its cages, to monitor the changes in gas concentration and gas solubility during hydrate formation and decomposition, and to identify phase changes in the study system. Laser Raman in-situ analytical technology has also been used in determination of hydrate structure and understanding its changing process under the conditions of ultra high pressure. Deep-sea in-situ Raman spectrometer can be employed for the in-situ analysis of the structures of natural gas hydrate and their formation environment. Raman imaging technology can be applied to specify the characteristics of crystallization and gas distribution over hydrate surface. With the development of laser Raman technology and its combination with other instruments, it will become more powerful and play a more significant role in the microscopic study of gas hydrate.

  6. Probing the photoreaction mechanism of phytochrome through analysis of resonance Raman vibrational spectra of recombinant analogues.

    PubMed

    Andel, F; Murphy, J T; Haas, J A; McDowell, M T; van der Hoef, I; Lugtenburg, J; Lagarias, J C; Mathies, R A

    2000-03-14

    Resonance Raman spectra of native and recombinant analogues of oat phytochrome have been obtained and analyzed in conjunction with normal mode calculations. On the basis of frequency shifts observed upon methine bridge deuteration and vinyl and C(15)-methine bridge saturation of the chromophore, intense Raman lines at 805 and 814 cm(-)(1) in P(r) and P(fr), respectively, are assigned as C(15)-hydrogen out-of-plane (HOOP) wags, lines at 665 cm(-)(1) in P(r) and at 672 and 654 cm(-)(1) in P(fr) are assigned as coupled C=C and C-C torsions and in-plane ring twisting modes, and modes at approximately 1300 cm(-)(1) in P(r) are coupled N-H and C-H rocking modes. The empirical assignments and normal mode calculations support proposals that the chromophore structures in P(r) and P(fr) are C(15)-Z,syn and C(15)-E,anti, respectively. The intensities of the C(15)-hydrogen out-of-plane, C=C and C-C torsional, and in-plane ring modes in both P(r) and P(fr) suggest that the initial photochemistry involves simultaneous bond rotations at the C(15)-methine bridge coupled to C(15)-H wagging and D-ring rotation. The strong nonbonded interactions of the C- and D-ring methyl groups in the C(15)-E,anti P(fr) chromophore structure indicated by the intense 814 cm(-1) C(15) HOOP mode suggest that the excited state of P(fr) and its photoproduct states are strongly coupled.

  7. Resonance Raman intensity analysis of chlorine dioxide dissolved in chloroform: The role of nonpolar solvation

    NASA Astrophysics Data System (ADS)

    Foster, Catherine E.; Barham, Bethany P.; Reid, Philip J.

    2001-05-01

    Absolute resonance Raman cross sections for chlorine dioxide (OClO) dissolved in chloroform are obtained at several excitation wavelengths spanning the photochemically relevant 2B1-2A2 optical transition. The absolute scattering cross sections of OClO are determined by reference to the 666 cm-1 transition of chloroform whose absolute scattering cross sections are reported here. The time-dependent theory for Raman and absorption are used to develop a mode-specific description of the 2A2 excited state surface. This description demonstrates that photoexcitation of OClO leads to significant structural evolution along the symmetric stretch and bend coordinates, with only limited evolution occurring along the asymmetric stretch. This description is similar to that determined for OClO dissolved in cyclohexane and water demonstrating that the excited-state structural evolution of OClO is similar in these solvents. Analysis of the OClO absolute scattering cross sections establishes that the homogeneous linewidth is 95±15 cm-1 in chloroform, essentially identical to the linewidths in cyclohexane and water. To establish the origin of this linewidth, the fluorescence cross section for OClO dissolved in cyclohexane is measured and found to be consistent with an excited-state lifetime of ˜200 fs. Comparison of this lifetime to the homogeneous linewidth establishes that the homogeneous broadening is dominated by solvent-induced pure dephasing. It is proposed that the apparent solvent independence of the homogeneous linewidth reflects the mechanical response of the solvent to the photoinitiated change in solute geometry. In support of this hypothesis, the homogeneous linewidth is reproduced using the viscoelastic continuum model of nonpolar solvation. Finally, it is argued that the restricted evolution along the asymmetric-stretch coordinate is due to dielectric solvent-solute interactions consistent with the increase in inhomogeneous linewidth with an increase in solvent

  8. Resonance Raman investigation of β-cyclodextrin-encapsulated π-conjugated polymers.

    PubMed

    Kasiouli, Soulianna; Di Stasio, Francesco; McDonnell, Shane O; Constantinides, Christos P; Anderson, Harry L; Cacialli, Franco; Hayes, Sophia C

    2013-05-09

    Resonance Raman (RR) spectroscopy is used to investigate the effect of β-cyclodextrin encapsulation on the structural and photophysical properties of poly(4,4'-diphenylenevinylene). We especially focus on the thermal stability of the polymer. We find that within the range of 10-55 °C the uninsulated polymer exhibits decreased Raman intensity in all the vibrational bands with temperature, along with changes in the relative intensity of the C-C inter-ring stretch mode at 1270 cm(-1) with respect to the ring C-H in-plane symmetric bend at 1187 cm(-1), which provides evidence for conformational changes as a function of temperature. No changes are observed in the intensity of the in-phase CH out-of-plane wag of the vinylene group at 968 cm(-1). Therefore, the conformational changes involve mainly dihedral angle modification between the adjacent phenyl rings toward planarization, and little or no change in the planarity of the trans-vinylene group. The decrease of the optical absorption at 55 °C with respect to that at room temperature and the appearance of a new absorption band at lower energies explain the decrease in the RR intensities and the wavelength dependence of the relative intensities of the Raman band. We note that the conformational change into a more planar geometry, which affects a significant portion of the polymer population, is irreversible and consistent with thermally induced aggregation. Such a planarization is unexpected in view of the usually observed thermochromic behavior of conjugated polymers, which leads to an increase of the energy gap for increasing temperature, as the average dihedral angles are increased due to excitation of a larger number of vibrational modes. Interestingly, the higher threading ratio polymers are resistant to any conformational changes within this temperature range, as reflected by their unchanged RR spectra, due to the rotaxane's ability to suppress intermolecular interactions and aggregation. Interestingly, the

  9. Raman scattering study of filled skutterudite compounds

    NASA Astrophysics Data System (ADS)

    Ogita, N.; Kojima, R.; Hasegawa, T.; Takasu, Y.; Udagawa, M.; Kondo, T.; Takeda, N.; Ikeno, T.; Ishikawa, K.; Sugawara, H.; Kikuchi, D.; Sato, H.; Sekine, C.; Shirotani, I.

    2007-12-01

    Raman scattering of skutterudite compounds RT4X12 (R=La, Ce, Pr, Nd, Sm and Yb, T=Fe, Ru and Os, X=P and Sb) have been measured. All first-order Raman active phonons are observed and are assigned as the pnicogen vibrations. At the low energy region, the second-order phonons, due to the vibration of the rare earth ions with a flat phonon dispersion, are observed in the spectra of RRu4P12 (R=La and Sm) and ROs4Sb12 (R=La, Ce, Pr, Nd, and Sm). The appearance of the second-order phonons in the spectra is caused by an anharmonic vibrations of rare earth ions in large cage space and a large density of state due to the flat phonon dispersion. However, in spite of the similar cage space, the 2nd-order phonons are hardly observed for RFe4Sb12 and RRu4Sb12. Thus, these results suggest that the dynamics of the rare earth ion is closely related to not only the cage size but also the electronic state due to the transition metals. Raman spectra of PrRu4P12 show the drastic spectral change due to the metal-insulator transition. The phonon spectra and crystal field excitations due to the structural change have been assigned above and below the transition temperature.

  10. FT-Raman spectroscopy study of human breast tissue

    NASA Astrophysics Data System (ADS)

    Bitar Carter, Renata A.; Martin, Airton A.; Netto, Mario M.; Soares, Fernando A.

    2004-07-01

    Optical spectroscopy has been extensively studied as a potential in vivo diagnostic tool to provide information about the chemical and morphologic structure of tissue. Raman Spectroscpy is an inelastic scattering process that can provide a wealth of spectral features that can be related to the specific molecular structure of the sample. This article reports results of an in vitro study of the FT-Raman human breast tissue spectra. An Nd:YAG laser at 1064nm was used as the excitation source in the FT-Raman Spectrometer. The neoplastic human breast samples, both Fibroadenoma and ICD, were obtained during therapeutical routine medical procedures required by the primary disease, and the non-diseased human tissue was obtained in plastic surgery. No sample preparation was needed for the FT-Raman spectra collection. The FT-Raman spectra were recorded from normal, benign (Fibroadenomas) and malignant (IDC-Intraductal Carcinoma) samples, adding up 51 different areas. The main spectral differences of a typical FT-Raman spectra of a Normal (Non-diseased), Fibroadenoma, and Infiltrating Ductal Carcinoma (IDC) breast tissue at the interval of 600 to 1800cm-1, which may differentiate diagnostically the sample, were found in the bands of 1230 to 1295cm-1, 1440 to 1460 cm-1 and 1650 to 1680 cm-1, assigned to the vibrational bands of the carbohydrate-amide III, proteins and lipids, and carbohydrate-amide I, respectively.

  11. [Study on the treatment turquoise using Raman spectroscopy].

    PubMed

    Chen, Quan-li; Yuan, Xin-qiang; Chen, Jing-zhong; Qi, Li-jian

    2010-07-01

    Due to a variety of the enhancement and treatment turquoises discovered in gem markets, the identification of turquoise is becoming more and more difficult. By using laser Raman spectroscopy analysis, the characteristics of Raman spectra of the pressed and filled turquoises were studied. The results show that laser Raman spectroscopy is an effective technique to identify the enhancement and treatment turquoises and the natural ones, moreover, it's a non-destructive testing method. The Raman spectra of the enhancement and treatment turquoises are resulted mainly from the vibrational mode and frequency of water, hydroxyl units, PO4 tetrahedron and CH2 units. Besides, they have the characteristic Raman spectra peaks at 2,937, 2,883 and 1,451 cm(-1) which are attributed to the stretching vibration and the bending vibration of CH2, respectively. These characteristic Raman vibration bands, it will help to distinguish the natural turquoises and the treatment ones. The study provides a new train of thought on the rapid, accurate, and non-destructive identification of turquoise.

  12. Resonance Raman and time-resolved resonance Raman evidence for enhanced localization in the [sup 3]MLCT states of ruthenium(II) complexes with the inherently asymmetric ligand 2-(2-pyridyl)pyrazine

    SciTech Connect

    Danzer, G.D.; Golus, J.A.; Kincaid, J.R. )

    1993-09-22

    The resonance Raman (RR) and time-resolved resonance Raman (TR[sup 3]) spectra of ruthenium(II) complexes containing the inherently asymmetric 2-(2-pyridyl)pyrazine (pypz) and its selectively deuteriated analogue are reported. The spectrum of the ground-state species is interpretable in terms of vibrationally isolated fragments with the exception of several modes which involve the interring and adjacent bonds. More importantly, the TR[sup 3] spectra of the (triplet) metal-to-ligand-charge-transfer state are shown to be consistent with the presence of a coordinated pypz in which the electronic charge is polarized toward the pyrazine fragment. A detailed discussion of the spectral analysis which leads to this conclusion is provided, and the potential implication of the effect for the design of practical devices is discussed. 19 refs., 4 figs., 1 tab.

  13. 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.

  14. 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.

  15. 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.

  16. Near-resonant rovibronic Raman scattering from 0 g + ( bb) valence state via the D0 u + ion-pair state in iodine molecule

    NASA Astrophysics Data System (ADS)

    Baturo, V. V.; Cherepanov, I. N.; Lukashov, S. S.; Petrov, A. N.; Poretsky, S. A.; Pravilov, A. M.

    2016-12-01

    Near-resonant Raman scattering from the electronic excited {I_2}( {0_g^ + ( {bb} )xrightarrow{{hv}}D0_u^ + to X0_g^ + } ) state via the intermediate ion-pair D0 u + state to the X one is observed for the first time. The Raman scattering follows a laser pulse. Its intensity I R is inversely proportional to the squared value of detuning from the resonant D, 22, 51 ← 0 g +( bb), 7, 52 transition, (Δν2)2, according to the theory of near-resonant Raman scattering. The ratio of Raman D → X scattering intensity to that of the D0 u +, ν D = 22, J D = 51 → X0 g + luminescence, I R / I D‒ X < 1.5 × 10-4 for Δν2 > 0.5 cm-1. The Raman and luminescence spectra are found to be identical.

  17. Raman Spectroscopy Study of Prostatic Adenocarcinoma Bulk Tissues

    NASA Astrophysics Data System (ADS)

    Devpura, S.; Dai, H.; Thakur, J. S.; Naik, R.; Cao, A.; Pandya, A.; Auner, G. W.; Sarkar, F.; Sakr, W.; Naik, V.

    2009-03-01

    Prostate cancer is one of the most common types of cancer among men. The mortality rate for this disease can be dramatically reduced if it can be diagnosed in its early stages. Raman spectroscopy is one of the optical techniques which can provide fingerprints of a disease in terms of its molecular composition which changes due to the onset of disease. The aim of this project is to investigate the differences in the Raman spectra to identify benign epithelium (BE), prostatic intraepithelial neoplasia (PIN) and adenocarcinoma of various Gleason grades in archived bulk tissues embedded in paraffin wax. For each tissue, two adjacent tissue sections were cut and dewaxed, where one of the sections was stained using haematoxylin and eosin for histological examination and the other unstained adjacent section was used for Raman spectroscopic studies. We have collected Raman spectra from 10 prostatic adenocarcinoma dewaxed tissue sections using Raman microscope (785 nm excitation laser). The data were analyzed using statistical methods of principal component analysis and discriminant function analysis to classify the tissue regions. The results indicate that Raman Spectroscopy can differentiate between BE, PIN and Cancer regions.

  18. 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.

  19. Electron-phonon coupling in perovskites studied by Raman Scattering

    NASA Astrophysics Data System (ADS)

    Sathe, V. G.; Tyagi, S.; Sharma, G.

    2016-10-01

    Raman scattering is an unique technique for characterization and quantification of electron-phonon, spin-phonon and spin-lattice coupling in many of the currently prominent compounds like multiferroics and manganites. In manganites, it is understood now that a phase separated landscape with coexisting metallic and insulating regions exist in most of the compounds and application of small external perturbation causes an alteration in this landscape. In such scenario, local metallic regions grow suddenly at the expense of insulating regions below the magnetic ordering temperature. Such regions can be characterized effectively using Raman scattering measurements where delocalized electrons couple with the adjacent phonon peaks giving a Fano resonance in the form of asymmetric line shape.

  20. 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.

  1. 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

    2016-02-04

    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.

  2. UV Resonance Raman Elucidation of the Terminal and Internal Peptide Bond Conformations of Crystalline and Solution Oligoglycines

    PubMed Central

    Bykov, Sergei V.; Asher, Sanford A.

    2010-01-01

    Spectroscopic investigations of macromolecules generally attempt to interpret the measured spectra in terms of the summed contributions of the different molecular fragments. This is the basis of the local mode approximation in vibrational spectroscopy. In the case of resonance Raman spectroscopy independent contributions of molecular fragments require both a local mode-like behavior and the uncoupled electronic transitions. Here we show that the deep UV resonance Raman spectra of aqueous solution phase oligoglycines show independent peptide bond molecular fragment contributions indicating that peptide bonds electronic transitions and vibrational modes are uncoupled. We utilize this result to separately determine the conformational distributions of the internal and penultimate peptide bonds of oligoglycines. Our data indicate that in aqueous solution the oligoglycine terminal residues populate conformations similar to those found in crystals (31-helices and β-strands), but with a broader distribution, while the internal peptide bond conformations are centered around the 31-helix Ramachandran angles. PMID:20657703

  3. Coherent Raman Studies of Shocked Liquids

    NASA Astrophysics Data System (ADS)

    McGrane, Shawn; Brown, Kathryn; Dang, Nhan; Bolme, Cynthia; Moore, David

    2013-06-01

    Transient vibrational spectroscopies offer the potential to directly observe time dependent shock induced chemical reaction kinetics. We report recent experiments that couple a hybrid picosecond/femtosecond coherent anti-Stokes Raman spectroscopy (CARS) diagnostic with our tabletop ultrafast laser driven shock platform. Initial results on liquids shocked to 20 GPa suggest that sub-picosecond dephasing at high pressure and temperature may limit the application of this nonresonant background free version of CARS. Initial results using interferometric CARS to increase sensitivity and overcome these limitations will be presented.

  4. Low frequency Raman study of the nucleosides

    NASA Astrophysics Data System (ADS)

    Koontz, Craig; Lee, Scott

    2011-03-01

    In both transcription and replication, the two helices of the DNA molecule move apart. Consequently, vibrations involving the relative motions of large portions of the molecule with respect to one another are of intrinsic interest. Such vibrations have relatively low frequencies because they involve weak bonds and large masses. Low frequency modes are difficult to observe in Raman spectroscopy because they are very close to the signal from the Rayleigh scattered light (which is very intense). In this poster, we will describe our results for the eight nucleosides: adenosine, deoxyadenosine, guanosine, deoxyguanosine, cytidine, deoxycytidine, uracil and deoxythymidine.

  5. Low frequency Raman study of the nucleosides

    NASA Astrophysics Data System (ADS)

    Koontz, Craig; Lee, Scott

    2010-10-01

    In both transcription and replication, the two helices of the DNA molecule move apart. Consequently, vibrations involving the relative motions of large portions of the molecule with respect to one another are of intrinsic interest. Such vibrations have relatively low frequencies because they involve weak bonds and large masses. Low frequency modes are difficult to observe in Raman spectroscopy because they are very close to the signal from the Rayleigh scattered light (which is very intense). In this poster, we will describe our results for the eight nucleosides: adenosine, deoxyadenosine, guanosine, deoxyguanosine, cytidine, deoxycytidine, uracil and deoxythymidine.

  6. Low frequency Raman study of the nucleosides

    NASA Astrophysics Data System (ADS)

    Koontz, Craig; Lee, Scott

    2011-04-01

    In both transcription and replication, the two helices of the DNA molecule move apart. Consequently, vibrations involving the relative motions of large portions of the molecule with respect to one another are of intrinsic interest. Such vibrations have relatively low frequencies because they involve weak bonds and large masses. Low frequency modes are difficult to observe in Raman spectroscopy because they are very close to the signal from the Rayleigh scattered light (which is very intense). In this poster, we will describe our results for the eight nucleosides: adenosine, deoxyadenosine, guanosine, deoxyguanosine, cytidine, deoxycytidine, uracil and deoxythymidine.

  7. 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.

  8. 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.

  9. Quantitative methods for structural characterization of proteins based on deep UV resonance Raman spectroscopy.

    PubMed

    Shashilov, Victor A; Sikirzhytski, Vitali; Popova, Ludmila A; Lednev, Igor K

    2010-09-01

    Here we report on novel quantitative approaches for protein structural characterization using deep UV resonance Raman (DUVRR) spectroscopy. Specifically, we propose a new method combining hydrogen-deuterium (HD) exchange and Bayesian source separation for extracting the DUVRR signatures of various structural elements of aggregated proteins including the cross-beta core and unordered parts of amyloid fibrils. The proposed method is demonstrated using the set of DUVRR spectra of hen egg white lysozyme acquired at various stages of HD exchange. Prior information about the concentration matrix and the spectral features of the individual components was incorporated into the Bayesian equation to eliminate the ill-conditioning of the problem caused by 100% correlation of the concentration profiles of protonated and deuterated species. Secondary structure fractions obtained by partial least squares (PLS) and least squares support vector machines (LS-SVMs) were used as the initial guess for the Bayessian source separation. Advantages of the PLS and LS-SVMs methods over the classical least squares calibration (CLSC) are discussed and illustrated using the DUVRR data of the prion protein in its native and aggregated forms.

  10. 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.

  11. Sensitive molecular diagnostics using surface-enhanced resonance Raman scattering (SERRS)

    NASA Astrophysics Data System (ADS)

    Faulds, Karen; Graham, Duncan; McKenzie, Fiona; MacRae, Douglas; Ricketts, Alastair; Dougan, Jennifer

    2009-02-01

    Surface enhanced resonance Raman scattering (SERRS) is an analytical technique with several advantages over competitive techniques in terms of improved sensitivity and multiplexing. We have made great progress in the development of SERRS as a quantitative analytical method, in particular for the detection of DNA. SERRS is an extremely sensitive and selective technique which when applied to the detection of labelled DNA sequences allows detection limits to be obtained which rival, and in most cases, are better than fluorescence. Here the conditions are explored which will enable the successful detection of DNA using SERRS. The enhancing surface which is used is crucial and in this case suspensions of nanoparticles were used as they allow quantitative behaviour to be achieved and allow analogous systems to current fluorescence based systems to be made. The aggregation conditions required to obtain SERRS of DNA are crucial and herein we describe the use of spermine as an aggregating agent. The nature of the label which is used, be it fluorescent, positively or negatively charged also effects the SERRS response and these conditions are again explored here. We have clearly demonstrated the ability to identify the components of a mixture of 5 analytes in solution by using two different excitation wavelengths and also of a 6-plex using data analysis techniques. These conditions will allow the use of SERRS for the detection of target DNA in a meaningful diagnostic assay.

  12. Uniaxially Stretched Flexible Surface Plasmon Resonance Film for Versatile Surface Enhanced Raman Scattering Diagnostics.

    PubMed

    Xu, Kaichen; Wang, Zuyong; Tan, Chuan Fu; Kang, Ning; Chen, Lianwei; Ren, Lei; Thian, Eng San; Ho, Ghim Wei; Ji, Rong; Hong, Minghui

    2017-08-09

    Surface-enhanced Raman scattering (SERS) spectroscopy affords a rapid, highly sensitive, and nondestructive approach for label-free and fingerprint diagnosis of a wide range of chemicals. It is of great significance to develop large-area, uniform, and environmentally friendly SERS substrates for in situ identification of analytes on complex topological surfaces. In this work, we demonstrate a biodegradable flexible SERS film via irreversibly and longitudinally stretching metal deposited biocompatible poly(ε-caprolactone) film. This composite film after stretching shows surprising phenomena: three-dimensional and periodic wave-shaped microribbons array embedded with a high density of nanogaps functioning as hot-spots at an average gap size of 20 nm and nanogrooves array along the stretching direction. The stretched polymer surface plasmon resonance film gives rise to more than 10 times signal enhancement in comparison with that of the unstretched composite film. Furthermore, the SERS signals with high uniformity exhibit good temperature stability. The polymer SPR film with excellent flexibility and transparency can be conformally attached onto arbitrary nonplanar surfaces for in situ detection of various chemicals. Our results pave a new way for next-generation flexible SERS detection means, as well as enabling its huge potentials toward green wearable devices for point-of-care diagnostics.

  13. Probing nitrite coordination in horseradish peroxidase by resonance Raman spectroscopy: Detection of two binding sites.

    PubMed

    Ioannou, Androulla; Pinakoulaki, Eftychia

    2017-04-01

    Nitrite is a powerful oxidant that affects the activity of peroxidases towards various substrates and leads to heme macrocycle modifications in members of the peroxidase family, such as the horseradish peroxidase (HRP). We have applied resonance Raman spectroscopy to investigate the structural properties of the species formed in the reaction of NO2(-) with the ferric form of HRP. Our data demonstrate that the heme nitrovinyl group is partially formed at near neutral pH, without coordination of NO2(-) to the heme Fe. Nitrite coordinates to the heme Fe at acidic pH in the nitro binding mode, characterized by the detection of the ν(Fe-NO2) at 563cm(-1), δ(FeNO2) at 822cm(-1) and νsym(NO2) at 1272cm(-1). The sensitivity of the vibrations of the heme Fe-nitro complex to H/D exchange indicates H-bonding interaction of the heme-bound ligand with the distal environment that determines the NO2(-) binding mode. A model describing the different modes of NO2(-) binding in HRP is presented. Copyright © 2017 Elsevier Inc. All rights reserved.

  14. Solvent effects on resonance Raman and hyper-Raman scatterings for a centrosymmetric distyrylbenzene and relationship to two-photon absorption.

    PubMed

    Leng, Weinan; Bazan, Guillermo C; Kelley, Anne Myers

    2009-01-28

    Resonance Raman (RR) and resonance hyper-Raman (RHR) spectra have been obtained for a nominally centrosymmetric dialkylammonium-substituted distyrylbenzene that was previously shown to exhibit a strong solvent polarity effect on its two-photon absorption strength. Spectra have been obtained in acetonitrile, methanol, dimethylsulfoxide, and water. In each solvent, the RR and RHR spectra show very similar intensity patterns in the strongest lines in both the C=C and C-C stretching regions, but the RHR peaks are shifted to higher energies by 5-10 cm(-1). These are interpreted as vibrations of similar mode character but different symmetries, with u symmetry modes observed in RHR and g symmetry modes in RR. In all solvents the nonzero chromophore contribution to the hyper-Rayleigh scattering indicates that the center of symmetry is broken to some degree, and this effect is more pronounced in water than in the other three solvents. The ratio of RR intensity to one-photon fluorescence intensity shows an approximate inverse relationship with the fluorescence quantum yield, consistent with the approximate solvent independence of the one-photon transition strength implied by the linear absorption spectra. The ratio of RHR intensity to two-photon fluorescence intensity is smaller than the corresponding RR to one-photon fluorescence ratio in all four solvents.

  15. 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)

  16. 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

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

    PubMed

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

    2013-02-19

    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.

  18. Brillouin and Raman Scattering Study of Ethylene Glycol Aqueous Solutions

    NASA Astrophysics Data System (ADS)

    Seshimo, Y.; Ike, Y.; Kojima, S.

    2008-02-01

    We studied the cluster structure of ethylene glycol aqueous solutions by Brillouin and Raman scattering. We measured the ultrasonic sound velocity of the sample by Brillouin scattering. From the concentration dependence of the sound velocity, we studied the cluster structure in the solution. We showed that the number of H2O molecule neighboring a EG molecule becomes a little higher with increasing temperature and the intermolecular interaction between EG and H2O molecules weakened with increasing temperature. In Raman scattering study, We studied the hydrogen bond in the solution using the OD stretching band. We revealed that the strength of the hydrogen bond is independent of the EG concentration.

  19. Time dependent density functional theory investigation of the resonance Raman properties of the julolidinemalononitrile push-pull chromophore in various solvents.

    PubMed

    Guthmuller, Julien; Champagne, Benoît

    2007-10-28

    The absorption and resonance Raman spectra have been investigated for the first excited state of the julolidinemalononitrile push-pull chromophore in cyclohexane, dichloromethane, and acetonitrile by means of time dependent density functional theory calculations. The effect of nonlocal exchange has been considered by using three different hybrid exchange-correlation functionals containing 20%, 35%, and 50% of exact Hartree-Fock exchange. The interactions with the solvent have been described by the polarizable continuum model. The short-time approximation expression has been used to evaluate the resonance Raman intensities, while the vibronic theory of resonance Raman spectroscopy has been employed to determine both the intensities and the excitation profiles. It is shown that a consistent description of the vibronic structure of the excited state and resonance Raman spectra can be obtained provided that an adequate amount, close to 35%, of exact exchange is included in the exchange-correlation functional. The effect of increasing the polarity of the solvent is well represented by the polarizable continuum model, both for the absorption spectra and resonance Raman intensities. In particular, these simulations can reproduce the observed variations of the 1560 cm(-1) band intensity and attribute them to elongations of a CC double bond upon electronic excitation. Moreover, the short-time approximation has been found sufficient to reproduce most of the results of the more evolved vibronic theory of resonance Raman spectroscopy, which includes summations over vibrational excited states, for both the spectral signatures and their solvent dependencies.

  20. Doubly resonant Raman electron paramagnetic transitions of Cr{sup 3+} in ruby (Al{sub 2}O{sub 3}:Cr{sup 3+}).

    SciTech Connect

    Lu, X.; Venugopalan, S.; Kim, H.; Grimsditch, M.; Rodriguez, S.; Ramdas, A. K.; Materials Science Division; Purdue Univ.; State Univ. of New York at Binghamton; Sogang Univ.

    2009-06-01

    We report the Raman electron paramagnetic resonance (EPR) of Cr{sup 3+} in ruby (Al{sub 2}O{sub 3}:Cr{sup 3+}) in the {sup 4}A{sub 2} (ground) and E{sup -} (excited) states of its well-known R{sub 1} emission line. Using tunable dye laser excitation within the range of the Zeeman components of R{sub 1}, we observe highly selective doubly resonant enhancements of the Raman EPR lines. The double resonances confirm the assignments of the Raman EPR lines, and they underscore the simultaneous occurrence of both 'in resonance' and 'out resonance' as visualized in the Kramers-Heisenberg quantum-mechanical picture of inelastic light scattering. The g factors of the {sup 4}A{sub 2} and E{sup -} states are consistent with the observed magnetic field dependence of the Raman EPR shifts. Through the interplay of Raman effect and the sharp Zeeman components of R{sub 1}, the results provide clear insights into the underlying microscopic mechanism of these resonant Raman EPR spectra of ruby.