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

Science.gov (United States)

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.

Normal Raman and surface enhanced Raman spectroscopic experiments with thin layer chromatography spots of essential amino acids using different laser excitation sources

Science.gov (United States)

István, Krisztina; Keresztury, Gábor; Szép, Andrea

2003-06-01

A comparative study of the feasibility and efficiency of Raman spectroscopic detection of thin layer chromatography (TLC) spots of some weak Raman scatterers (essential amino acids, namely, glycine and L-forms of alanine, serine, valine, proline, hydroxyproline, and phenylalanine) was carried out using four different visible and near-infrared (NIR) laser radiations with wavelengths of 532, 633, 785, and 1064 nm. Three types of commercial TLC plates were tested and the possibility of inducing surface enhanced Raman scattering (SERS) by means of Ag-sol was also investigated. The spectra obtained from spotted analytes adsorbed on TLC plates were of very different quality strongly depending on the excitation wavelength, the wetness of the samples, and the compounds examined. The best results were obtained with the simple silica TLC plate, and it has been established that the longest wavelength (lowest energy) NIR excitation of a Nd:YAG laser is definitely more suitable for generating normal Raman scattering of analyte spots than any of the visible radiations. Concerning SERS with application of Ag-sol to the TLC spots, 1-3 orders of magnitude enhancement was observed with wet samples, the greatest with the 532 nm radiation and gradually smaller with the longer wavelength excitations. It is shown, however, that due to severe adsorption-induced spectral distortions and increased sensitivity to microscopic inhomogeneity of the sample, none of the SERS spectra obtained with the dispersive Raman microscope operating in the visible region were superior to the best NIR normal FT-Raman spectra, as far as sample identification is concerned.

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

International Nuclear Information System (INIS)

Ye, ChuanXiang; Zhao, Yi; Liang, WanZhen

2015-01-01

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

Combined Raman and continuous-wave-excited two-photon fluorescence cell imaging

NARCIS (Netherlands)

Uzunbajakava, N.; Otto, Cornelis

2003-01-01

We demonstrate a confocal optical microscope that combines cw two-photon-excited fluorescence microscopy with confocal Raman microscopy. With this microscope fast image acquisition with fluorescence imaging can be used to select areas of interest for subsequent chemical analysis with spontaneous

Vibrational spectroscopy of the electronically excited state. 4. Nanosecond and picosecond time-resolved resonance Raman spectroscopy of carotenoid excited states

International Nuclear Information System (INIS)

Dallinger, R.F.; Farquharson, S.; Woodruff, W.H.; Rodgers, M.A.J.

1981-01-01

Resonance Raman and electronic absorption spectra are reported for the S 0 and T 1 states of the carotenoids β-carotene, zeaxanthin, echinenone, canthaxanthin, dihydroxylycopene, astaxanthin, decapreno(C 50 )-β-carotene, β-apo-8'-carotenal, and ethyl β-apo-8'-carotenoate. The results reveal qualitatively similar ground-state spectra and similar frequency shifts in all observed resonance Raman modes between S 0 and T 1 , regardless of carotenoid structure. Examinations of the relationship of the putative C--C and C==C frequencies in S 0 and T 1 reveals anomalous shifts to lower frequency in the ''single-bond'' mode upon electronic excitation. These shifts may be due to molecular distortions in the excited state which force changes in molecular motions comprising the observed modes. However, another possibility requiring no distortion is that the interaction (off-diagonal) force constants connecting the C--C and C==C modes change sign upon electronic excitation. This latter phenomenon may provide a unitary explanation for the ''anomalous'' frequency shifts in the C--C and C==C modes, both in the T 1 states of carotenoids and in the S 1 states of simpler polyenes, without postulating large, unpredicted structural changes upon excitation or general errors in existing vibrational or theoretical analyses. Resonance Raman and absorbance studies with 35-ps time resolution suggest that S 1 lifetime (of the 1 B/sub u/ and/or the 1 A/sub g/* states) of β-carotene in benzene is less than 1 ps

Measurements of stratospheric Pinatubo aerosol extinction profiles by a Raman lidar

International Nuclear Information System (INIS)

Abo, Makoto; Nagasawa, Chikao.

1992-01-01

The Raman lidar has been used for remote measurements of water vapor, ozone and atmospheric temperature in the lower troposphere because the Raman cross section is three orders smaller than the Rayleigh cross section. The authors estimated the extinction coefficients of the Pinatubo volcanic aerosol in the stratosphere using a Raman lidar. If the precise aerosol extinction coefficients are derived, the backscatter coefficient of a Mie scattering lidar will be more accurately estimated. The Raman lidar has performed to measure density profiles of some species using Raman scattering. Here the authors used a frequency-doubled Nd:YAG laser for transmitter and received nitrogen vibrational Q-branch Raman scattering signal. Ansmann et al. (1990) derived tropospherical aerosol extinction profiles with a Raman lidar. The authors think that this method can apply to dense stratospheric aerosols such as Pinatubo volcanic aerosols. As dense aerosols are now accumulated in the stratosphere by Pinatubo volcanic eruption, the error of Ramen lidar signal regarding the fluctuation of air density can be ignored

Comparison of fluorescence rejection methods of baseline correction and shifted excitation Raman difference spectroscopy

Science.gov (United States)

Cai, Zhijian; Zou, Wenlong; Wu, Jianhong

2017-10-01

Raman spectroscopy has been extensively used in biochemical tests, explosive detection, food additive and environmental pollutants. However, fluorescence disturbance brings a big trouble to the applications of portable Raman spectrometer. Currently, baseline correction and shifted-excitation Raman difference spectroscopy (SERDS) methods are the most prevailing fluorescence suppressing methods. In this paper, we compared the performances of baseline correction and SERDS methods, experimentally and simulatively. Through the comparison, it demonstrates that the baseline correction can get acceptable fluorescence-removed Raman spectrum if the original Raman signal has good signal-to-noise ratio, but it cannot recover the small Raman signals out of large noise background. By using SERDS method, the Raman signals, even very weak compared to fluorescence intensity and noise level, can be clearly extracted, and the fluorescence background can be completely rejected. The Raman spectrum recovered by SERDS has good signal to noise ratio. It's proved that baseline correction is more suitable for large bench-top Raman system with better quality or signal-to-noise ratio, while the SERDS method is more suitable for noisy devices, especially the portable Raman spectrometers.

Time-dependent theory of Raman scattering for systems with several excited electronic states: Application to a H+3 model system

International Nuclear Information System (INIS)

Heather, R.; Metiu, H.

1989-01-01

The time-dependent formulation of Raman scattering theory is used to study how nonadiabatic interactions affect the Raman spectrum of a model H + 3 system, which has two excited electronic states. We start with a formula derived by Heller which gives the Raman scattering cross section as the Fourier transform (over time) of a time-dependent overlap integral. The latter is calculated with a method proposed by Fleck, Morris, and Feit, and extended to curve crossing by Alvarellos and Metiu. In performing these calculations we are especially interested in displaying effects typical of systems having more than one upper state. If the incident laser populates two electronic states there are several ways (i.e., excite to state one and emit from state two, excite to state one, and emit from state one, etc.) by which the Raman process can reach a given final state, and this leads to quantum interference. This interference is manifested in the Raman cross section as approximate selection rules controlling which final states can be reached through the Raman process. These selection rules depend on the relative orientation of the transition dipoles that radiatively couple the ground electronic state with the excited electronic states. The magnitude of the nonadiabatic contribution to the Raman emission, e.g., the contribution from absorbing to state one and emitting from state two, can be determined from the polarization dependence of the Raman emission if the transition dipoles have neither parallel nor antiparallel relative orientation

Electronic resonances in broadband stimulated Raman spectroscopy

Science.gov (United States)

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.

Excited-state structure and electronic dephasing time of Nile blue from absolute resonance Raman intensities

Science.gov (United States)

Lawless, Mary K.; Mathies, Richard A.

1992-06-01

Absolute resonance Raman cross sections are measured for Nile blue 690 perchlorate dissolved in ethylene glycol with excitation at 514, 531, and 568 nm. These values and the absorption spectrum are modeled using a time-dependent wave packet formalism. The excited-state equilibrium geometry changes are quantitated for 40 resonance Raman active modes, seven of which (590, 1141, 1351, 1429, 1492, 1544, and 1640 cm-1 ) carry 70% of the total resonance Raman intensity. This demonstrates that in addition to the prominent 590 and 1640 cm-1 modes, a large number of vibrational degrees of freedom are Franck-Condon coupled to the electronic transition. After exposure of the explicit vibrational progressions, the residual absorption linewidth is separated into its homogeneous [350 cm-1 half-width at half-maximum (HWHM)] and inhomogeneous (313 cm-1 HWHM) components through an analysis of the absolute Raman cross sections. The value of the electronic dephasing time derived from this study (25 fs) compares well to previously published results. These data should be valuable in multimode modeling of femtosecond experiments on Nile blue.

UV Raman spectroscopy of H2-air flames excited with a narrowband KrF laser

Science.gov (United States)

Shirley, John A.

1990-01-01

Raman spectra of H2 and H2O in flames excited by a narrowband KrF excimer laser are reported. Observations are made over a porous-plug, flat-flame burner reacting H2 in air, fuel-rich with nitrogen dilution to control the temperature, and with an H2 diffusion flame. Measurements made from UV Raman spectra show good agreement with measurements made by other means, both for gas temperature and relative major species concentrations. Laser-induced fluorescence interferences arising from OH and O2 are observed in emission near the Raman spectra. These interferences do not preclude Raman measurements, however.

Sub-50 fs excited state dynamics of 6-chloroguanine upon deep ultraviolet excitation.

Science.gov (United States)

Mondal, Sayan; Puranik, Mrinalini

2016-05-18

The photophysical properties of natural nucleobases and their respective nucleotides are ascribed to the sub-picosecond lifetime of their first singlet states in the UV-B region (260-350 nm). Electronic transitions of the ππ* type, which are stronger than those in the UV-B region, lie at the red edge of the UV-C range (100-260 nm) in all isolated nucleobases. The lowest energetic excited states in the UV-B region of nucleobases have been investigated using a plethora of experimental and theoretical methods in gas and solution phases. The sub-picosecond lifetime of these molecules is not a general attribute of all nucleobases but specific to the five primary nucleobases and a few xanthine and methylated derivatives. To determine the overall UV photostability, we aim to understand the effect of more energetic photons lying in the UV-C region on nucleobases. To determine the UV-C initiated photophysics of a nucleobase system, we chose a halogen substituted purine, 6-chloroguanine (6-ClG), that we had investigated previously using resonance Raman spectroscopy. We have performed quantitative measurements of the resonance Raman cross-section across the Bb absorption band (210-230 nm) and constructed the Raman excitation profiles. We modeled the excitation profiles using Lee and Heller's time-dependent theory of resonance Raman intensities to extract the initial excited state dynamics of 6-ClG within 30-50 fs after photoexcitation. We found that imidazole and pyrimidine rings of 6-ClG undergo expansion and contraction, respectively, following photoexcitation to the Bb state. The amount of distortions of the excited state structure from that of the ground state structure is reflected by the total internal reorganization energy that is determined at 112 cm(-1). The contribution of the inertial component of the solvent response towards the total reorganization energy was obtained at 1220 cm(-1). In addition, our simulation also yields an instantaneous response of the first

Raman scattering of Cisplatin near silver nanoparticles

Science.gov (United States)

Mirsaleh-Kohan, Nasrin; Duplanty, Michael; Torres, Marjorie; Moazzezi, Mojtaba; Rostovtsev, Yuri V.

2018-03-01

The Raman scattering of Cisplatin (the first generation of anticancer drugs) has been studied. In the presence of silver nanoparticles, strong modifications of Raman spectra have been observed. The Raman frequencies have been shifted and the line profiles are broadened. We develop a theoretical model to explain the observed features of the Raman scattering. The model takes into account self-consistently the interaction of molecules with surface plasmonic waves excited in the silver nanoparticles, and it provides a qualitative agreement with the observed Raman spectra. We have demonstrated that the using silver nanoparticles can increase sensitivity of the technique, and potentially it has a broader range of applications to both spectroscopy and microscopy.

A Raman spectroscopic study of organic matter in interplanetary dust particles and meteorites using multiple wavelength laser excitation

OpenAIRE

Starkey, N. A.; Franchi, I. A.; Alexander, C. M. O'D.

2013-01-01

Raman spectroscopy was used to investigate insoluble organic matter (IOM) from a range of chondritic meteorites, and a suite of interplanetary dust particles (IDPs). Three monochromatic excitation wavelengths (473 nm, 514 nm, 632 nm) were applied sequentially to assess variations in meteorite and IDP Raman peak parameters (carbon D and G bands) as a function of excitation wavelength (i.e., dispersion). Greatest dispersion occurs in CVs > OCs > CMs > CRs with type 3 chondrites compared at diff...

Time-resolved resonance raman spectrum of all-trans-diphenylbutadiene in the lowest excited singlet state

DEFF Research Database (Denmark)

Wilbrandt, Robert Walter; Jensen, Niels-Henrik; Langkilde, F.W.

1984-01-01

The resonance Raman spectrwn of all-trans-diphenylbutadiene in its lowest excited S1 state excited in resonance with the S1 → Sn absorption band at 650 nm in non-polar solvents is reported. Three vibrational bands at 1572, 1481 and 1165 cm−1 are observed. A possible assignment of the the 1481 cm−...

Resonance Raman scattering of β-carotene solution excited by visible laser beams into second singlet state.

Science.gov (United States)

Lu, Luyao; Shi, Lingyan; Secor, Jeff; Alfano, Robert

2018-02-01

This study aimed to use self-absorption correction to determine the Raman enhancement of β-carotene. The Raman spectra of β-carotene solutions were measured using 488nm, 514nm, 532nm and 633nm laser beams, which exhibited significant resonance Raman (RR) enhancement when the laser energy approaches the electronic transition energy from S 0 to S 2 state. The Raman intensity and the actual resonance Raman gain without self-absorption from S 2 state by β-carotene were also obtained to evaluate the effect of self-absorption on RR scattering. Moreover, we observed the Raman intensity strength followed the absorption spectra. Our study found that, although 488nm and 514nm pumps seemed better for stronger RR enhancement, 532nm would be the optimum Raman pump laser with moderate RR enhancement due to reduced fluorescence and self-absorption. The 532nm excitation will be helpful for applying resonance Raman spectroscopy to investigate biological molecules in tissues. Copyright © 2017 Elsevier B.V. All rights reserved.

Raman lidar water vapor profiling over Warsaw, Poland

Science.gov (United States)

Stachlewska, Iwona S.; Costa-Surós, Montserrat; Althausen, Dietrich

2017-09-01

Water vapor mixing ratio and relative humidity profiles were derived from the multi-wavelength Raman PollyXT lidar at the EARLINET site in Warsaw, using the Rayleigh molecular extinction calculation based on atmospheric temperature and pressure from three different sources: i) the standard atmosphere US 62, ii) the Global Data Assimilation System (GDAS) model output, and iii) the WMO 12374 radiosoundings launched at Legionowo. With each method, 136 midnight relative humidity profiles were obtained for lidar observations from July 2013 to August 2015. Comparisons of these profiles showed in favor of the latter method (iii), but it also indicated that the other two data sources could replace it, if necessary. Such use was demonstrated for an automated retrieval of water vapor mixing ratio from dusk until dawn on 19/20 March 2015; a case study related to an advection of biomass burning aerosol from forest fires over Ukraine. Additionally, an algorithm that applies thresholds to the radiosounding relative humidity profiles to estimate macro-physical cloud vertical structure was used for the first time on the Raman lidar relative humidity profiles. The results, based on a subset of 66 profiles, indicate that below 6 km cloud bases/tops can be successfully obtained in 53% and 76% cases from lidar and radiosounding profiles, respectively. Finally, a contribution of the lidar derived mean relative humidity to cloudy conditions within the range of 0.8 to 6.2 km, in comparison to clear-sky conditions, was estimated.

Surface-enhanced Raman scattering (SERS) of riboflavin on nanostructured Ag surfaces: The role of excitation wavelength, plasmon resonance and molecular resonance

Science.gov (United States)

Šubr, Martin; Kuzminova, Anna; Kylián, Ondřej; Procházka, Marek

2018-05-01

Optimization of surface-enhanced Raman scattering (SERS)-based sensors for (bio)analytical applications has received much attention in recent years. For optimum sensitivity, both the nanostructure fabrication process and the choice of the excitation wavelength used with respect to the specific analyte studied are of crucial importance. In this contribution, detailed SERS intensity profiles were measured using gradient nanostructures with the localized surface-plasmon resonance (LSPR) condition varying across the sample length and using riboflavin as the model biomolecule. Three different excitation wavelengths (633 nm, 515 nm and 488 nm) corresponding to non-resonance, pre-resonance and resonance excitation with respect to the studied molecule, respectively, were tested. Results were interpreted in terms of a superposition of the enhancement provided by the electromagnetic mechanism and intrinsic properties of the SERS probe molecule. The first effect was dictated mainly by the degree of spectral overlap between the LSPR band, the excitation wavelength along with the scattering cross-section of the nanostructures, while the latter was influenced by the position of the molecular resonance with respect to the excitation wavelength. Our experimental findings contribute to a better understanding of the SERS enhancement mechanism.

Composition profiling of seized ecstasy tablets by Raman spectroscopy.

Science.gov (United States)

Bell, S E; Burns, D T; Dennis, A C; Matchett, L J; Speers, J S

2000-10-01

Raman spectroscopy with far-red excitation has been investigated as a simple and rapid technique for composition profiling of seized ecstasy (MDMA, N-methyl-3,4-methylenedioxyamphetamine) tablets. The spectra obtained are rich in vibrational bands and allow the active drug and excipient used to bulk the tablets to be identified. Relative band heights can be used to determine drug/excipient ratios and the degree of hydration of the drug while the fact that 50 tablets per hour can be analysed allows large numbers of spectra to be recorded. The ability of Raman spectroscopy to distinguish between ecstasy tablets on the basis of their chemical composition is illustrated here by a sample set of 400 tablets taken from a large seizure of > 50,000 tablets that were found in eight large bags. The tablets are all similar in appearance and carry the same logo. Conventional analysis by GC-MS showed they contained MDMA. Initial Raman studies of samples from each of the eight bags showed that despite some tablet-to-tablet variation within each bag the contents could be classified on the basis of the excipients used. The tablets in five of the bags were sorbitol-based, two were cellulose-based and one bag contained tablets with a glucose excipient. More extensive analysis of 50 tablets from each of a representative series of sample bags have distribution profiles that showed the contents of each bag were approximately normally distributed about a mean value, rather than being mixtures of several discrete types. Two of the sorbitol-containing sample sets were indistinguishable while a third was similar but not identical to these, in that it contained the same excipient and MDMA with the same degree of hydration but had a slightly different MDMA/sorbitol ratio. The cellulose-based samples were badly manufactured and showed considerable tablet-to-tablet variation in their drug/excipient ratio while the glucose-based tablets had a tight distribution in their drug/excipient ratios

Femtosecond stimulated Raman spectroscopy as a tool to detect molecular vibrations in ground and excited electronic states

Energy Technology Data Exchange (ETDEWEB)

Gelin, Maxim F.; Domcke, Wolfgang [Department of Chemistry, Technische Universität München, D-85747 Garching (Germany); Rao, B. Jayachander [Departamento de Química and Centro de Química, Universidade de Coimbra, 3004-535 Coimbra (Portugal)

2016-05-14

We give a detailed theoretical analysis of the simplest variant of femtosecond stimulated Raman spectroscopy, where a picosecond Raman pump pulse and a femtosecond Raman probe pulse are applied resonantly to a chromophore in thermal equilibrium in the ground electronic state. We demonstrate that this technique is capable of the detection of dephasing-free Raman-like lines revealing vibrational modes not only in the electronic ground state but also in the excited electronic state of the chromophore. The analytical results obtained with simplifying assumptions for the shape of the laser pulses are substantiated by numerical simulations with realistic laser pulses, employing the equation-of-motion phase-matching approach.

High resolution humidity, temperature and aerosol profiling with MeteoSwiss Raman lidar

Science.gov (United States)

Dinoev, Todor; Arshinov, Yuri; Bobrovnikov, Sergei; Serikov, Ilya; Calpini, Bertrand; van den Bergh, Hubert; Parlange, Marc B.; Simeonov, Valentin

2010-05-01

Meteorological services rely, in part, on numerical weather prediction (NWP). Twice a day radiosonde observations of water vapor provide the required data for assimilation but this time resolution is insufficient to resolve certain meteorological phenomena. High time resolution temperature profiles from microwave radiometers are available as well but have rather low vertical resolution. The Raman LIDARs are able to provide temperature and humidity profiles with high time and range resolution, suitable for NWP model assimilation and validation. They are as well indispensible tools for continuous aerosol profiling for high resolution atmospheric boundary layer studies. To improve the database available for direct meteorological applications the Swiss meteo-service (MeteoSwiss), the Swiss Federal Institute of Technology in Lausanne (EPFL) and the Swiss National Science Foundation (SNSF) initiated a project to design and build an automated Raman lidar for day and night vertical profiling of tropospheric water vapor with the possibility to further upgrade it with an aerosol and temperature channels. The project was initiated in 2004 and RALMO (Raman Lidar for meteorological observations) was inaugurated in August 2008 at MeteoSwiss aerological station at Payerne. RALMO is currently operational and continuously profiles water vapor mixing ratio, aerosol backscatter ratio and aerosol extinction. The instrument is a fully automated, self-contained, eye-safe Raman lidar operated at 355 nm. Narrow field-of-view multi-telescope receiver and narrow band detection allow day and night-time vertical profiling of the atmospheric humidity. The rotational-vibrational Raman lidar responses from water vapor and nitrogen are spectrally separated by a high-throughput fiber coupled diffraction grating polychromator. The elastic backscatter and pure-rotational Raman lidar responses (PRR) from oxygen and nitrogen are spectrally isolated by a double grating polychromator and are used to

A Raman spectroscopic study of organic matter in interplanetary dust particles and meteorites using multiple wavelength laser excitation

Science.gov (United States)

Starkey, N. A.; Franchi, I. A.; Alexander, C. M. O'd.

2013-10-01

Raman spectroscopy was used to investigate insoluble organic matter (IOM) from a range of chondritic meteorites, and a suite of interplanetary dust particles (IDPs). Three monochromatic excitation wavelengths (473 nm, 514 nm, 632 nm) were applied sequentially to assess variations in meteorite and IDP Raman peak parameters (carbon D and G bands) as a function of excitation wavelength (i.e., dispersion). Greatest dispersion occurs in CVs > OCs > CMs > CRs with type 3 chondrites compared at different excitation wavelengths displaying conformable relationships, in contrast to type 2 chondrites. These findings indicate homogeneity in the structural nature of type 3 chondrite IOM, while organic matter (OM) in type 2 chondrites appears to be inherently more heterogeneous. If type 2 and type 3 chondrite IOM shares a common source, then thermal metamorphism may have a homogenizing effect on the originally more heterogeneous OM. IDP Raman G bands fall on an extension of the trend displayed by chondrite IOM, with all IDPs having Raman parameters indicative of very disordered carbon, with almost no overlap with IOM. The dispersion effect displayed by IDPs is most similar to CMs for the G band, but intermediate between CMs and CRs for the D band. The existence of some overlapping Raman features in the IDPs and IOM indicates that their OM may share a common origin, but the IDPs preserve more pristine OM that may have been further disordered by ion irradiation. H, C, and N isotopic data for the IDPs reveal that the disordered carbon in IDPs corresponds with higher δ15N and lower δ13C.

[Surface-enhanced Raman spectroscopy analysis of thiabendazole pesticide].

Science.gov (United States)

Lin, Lei; Wu, Rui-mei; Liu, Mu-hua; Wang, Xiao-bin; Yan, Lin-yuan

2015-02-01

Surface-enhanced Raman spectroscopy (SERS) technique was used to analyze the Raman peaks of thiabendazole pesticides in the present paper. Surface enhanced substrates of silver nanoparticle were made based on microwave technology. Raman signals of thiabendazole were collected by laser Micro-Raman spectrometer with 514. 5 and 785 nm excitation wavelengths, respectively. The Raman peaks at different excitation wavelengths were analyzed and compared. The Raman peaks 782 and 1 012 at 785 nm excitation wavelength were stronger, which were C--H out-of-plane vibrations. While 1284, 1450 and 1592 cm(-1) at 514.5 nm excitation wavelength were stronger, which were vng and C==N stretching. The study results showed that the intensity of Raman peak and Raman shift at different excitation wavelengths were different And strong Raman signals were observed at 782, 1012, 1284, 1450 and 1592 cm(-1) at 514.5 and 785 nm excitation wavelengths. These characteristic vibrational modes are characteristic Raman peaks of carbendazim pesticide. The results can provide basis for the rapid screening of pesticide residue in agricultural products and food based on Raman spectrum.

Laser-excited luminescence of trace Nd3+ impurity in LaBr3 revealed by Raman spectroscopy

Science.gov (United States)

Yu, Jinqiu; Cui, Lei; He, Huaqiang; Hu, Yunsheng; Wu, Hao; Zeng, Jia; Liu, Yuzhu

2012-10-01

Unexpected additional bands with obvious non-vibrational features were observed in Raman spectra of LaBr3. Extensive study was carried out to reveal the origin of these bands. Results indicate that the additional bands correspond to laser-excited luminescence of trace Nd3+ impurity unintentionally introduced from the La2O3 raw material, which was further confirmed by Raman spectra of specially prepared Nd3+-doped LaBr3 and LaOBr samples. The luminescence properties of Nd3+ in different matrix were compared and discussed. The ultrasensitivity of Raman spectroscopy in detecting trace luminescent lanthanide ions shows good potential for analytical applications.

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

International Nuclear Information System (INIS)

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

2014-01-01

The excited state structural dynamics of phenyl isothiocyanate (PITC) after excitation to the light absorbing S 2 (A′), S 6 (A′), and S 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 2 (A′), S 6 (A′), and S 7 (A′) excited states were very different. The conical intersection point CI(S 2 /S 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 2 (A′) state: the radiative S 2,min → S 0 transition and the nonradiative S 2 → S 1 internal conversion via CI(S 2 /S 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 1 /T 1 ) in the excited state decay dynamics of PITC is evaluated

Shifted excitation Raman difference spectroscopy for authentication of cheese and cheese analogues

Science.gov (United States)

Sowoidnich, Kay; Kronfeldt, Heinz-Detlef

2016-04-01

Food authentication and the detection of adulterated products are recent major issues in the food industry as these topics are of global importance for quality control and food safety. To effectively address this challenge requires fast, reliable and non-destructive analytical techniques. Shifted Excitation Raman Difference Spectroscopy (SERDS) is well suited for identification purposes as it combines the chemically specific information obtained by Raman spectroscopy with the ability for efficient fluorescence rejection. The two slightly shifted excitation wavelengths necessary for SERDS are realized by specially designed microsystem diode lasers. At 671 nm the laser (optical power: 50 mW, spectral shift: 0.7 nm) is based on an external cavity configuration whereas an emission at 783 nm (optical power: 110 mW, spectral shift: 0.5 nm) is achieved by a distributed feedback laser. To investigate the feasibility of SERDS for rapid and nondestructive authentication purposes four types of cheese and three different cheese analogues were selected. Each sample was probed at 8 different positions using integration times of 3-10 seconds and 10 spectra were recorded at each spot. Principal components analysis was applied to the SERDS spectra revealing variations in fat and protein signals as primary distinction criterion between cheese and cheese analogues for both excitation wavelengths. Furthermore, to some extent, minor compositional differences could be identified to discriminate between individual species of cheese and cheese analogues. These findings highlight the potential of SERDS for rapid food authentication potentially paving the way for future applications of portable SERDS systems for non-invasive in situ analysis.

Perpendicular State of an Electronically Excited Stilbene: Observation by Femtosecond-Stimulated Raman Spectroscopy.

Science.gov (United States)

Quick, Martin; Dobryakov, Alexander L; Ioffe, Ilya N; Granovsky, Alex A; Kovalenko, Sergey A; Ernsting, Nikolaus P

2016-10-20

In the photoisomerization path of stilbene, a perpendicular state P on the S 1 potential energy surface is expected just before internal conversion through a conical intersection S 1 /S 0 . For decades the observation of P was thwarted by a short lifetime τ P in combination with slow population flow over a barrier. But these limitations can be overcome by ethylenic substitution. Following optical excitation of trans-1,1'-dicyanostilbene, P is populated significantly (τ P = 27 ps in n-hexane) and monitored by an exited-state absorption band at 370 nm. Here we report stimulated Raman lines of P. The strongest, at 1558 cm -1 , is attributed to stretching vibrations of the phenyl rings. Transient electronic states, resonance conditions, and corresponding Raman signals are discussed.

Equations describing coherent and partially coherent multilevel molecular excitation induced by pulsed Raman transitions: III

International Nuclear Information System (INIS)

Shore, B.W.; Sacks, R.; Karr, T.

1987-01-01

This memo discusses the equations of motion used to describe multilevel molecular excitation induced by Raman transitions. These equations are based upon the time-dependent Schroedinger equation expressed in a basis of molecular energy states. A partition of these states is made into two sets, those that are far from resonance (and hence unpopulated) and those that are close to resonance, either by one-photon transition or two-photon (Raman) processes. By adiabatic elimination an effective Schroedinger equation is obtained for the resonance states alone. The effective Hamiltonian is expressible in terms of a polarizibility operator

The effects of machine parameters on residual stress determined using micro-Raman spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Sparks, R.G.; Enloe, W.S.; Paesler, M.A.

1988-12-01

The effects of machine parameters on residual stresses in single point diamond turned silicon and germanium have been investigated using micro-Raman spectroscopy. Residual stresses were sampled across ductile feed cuts in < 100 > silicon and germanium which were single point diamond turned using a variety of feed rates, rake angles and clearance angles. High spatial resolution micro-Raman spectra (1{mu}m spot) were obtained in regions of ductile cutting where no visible surface damage was present. The use of both 514-5nm and 488.0nm excitation wavelengths, by virtue of their differing characteristic penetration depths in the materials, allowed determinations of stress profiles as a function of depth into the sample. Previous discussions have demonstrated that such Raman spectra will exhibit asymmetrically broadened peaks which are characteristic of the superposition of a continuum of Raman scatterers from the various depths probed. Depth profiles of residual stress were obtained using computer deconvolution of the resulting asymmetrically broadened raman spectra.

Raman Investigation of Temperature Profiles of Phospholipid Dispersions in the Biochemistry Laboratory

Science.gov (United States)

Craig, Norman C.

2015-06-01

The temperature dependence of self-assembled, cell-like dispersions of phospholipids is investigated with Raman spectroscopy in the biochemistry laboratory. Vibrational modes in the hydrocarbon interiors of phospholipid bilayers are strongly Raman active, whereas the vibrations of the polar head groups and the water matrix have little Raman activity. From Raman spectra increases in fluidity of the hydrocarbon chains can be monitored with intensity changes as a function of temperature in the CH-stretching region. The experiment uses detection of scattered 1064-nm laser light (Nicolet NXR module) by a Fourier transform infrared spectrometer (Nicolet 6700). A thermoelectric heater-cooler device (Melcor) gives convenient temperature control from 5 to 95°C for samples in melting point capillaries. Use of deuterium oxide instead of water as the matrix avoids some absorption of the exciting laser light and interference with intensity observations in the CH-stretching region. Phospholipids studied range from dimyristoylphosphotidyl choline (C14, transition T = 24°C) to dibehenoylphosphotidyl choline (C22, transition T = 74°C).

Investigation of germanium implanted with aluminum by multi-laser micro-Raman spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Sanson, A., E-mail: andrea.sanson@unipd.it [Dipartimento di Fisica e Astronomia, Università di Padova, Via Marzolo 8, I-35131 Padova (Italy); Napolitani, E. [MATIS IMM-CNR at Dipartimento di Fisica e Astronomia, Università di Padova, Via Marzolo 8, I-35131 Padova (Italy); Impellizzeri, G. [MATIS IMM-CNR and Dipartimento di Fisica e Astronomia, Università di Catania, Via S. Sofia 64, I-95123 Catania (Italy); Giarola, M. [Dipartimento di Informatica, Università di Verona, Strada le Grazie 15, I-37134 Verona (Italy); De Salvador, D. [Dipartimento di Fisica e Astronomia, Università di Padova, Via Marzolo 8, I-35131 Padova (Italy); Privitera, V.; Priolo, F. [MATIS IMM-CNR and Dipartimento di Fisica e Astronomia, Università di Catania, Via S. Sofia 64, I-95123 Catania (Italy); Mariotto, G. [Dipartimento di Informatica, Università di Verona, Strada le Grazie 15, I-37134 Verona (Italy); Carnera, A. [Dipartimento di Fisica e Astronomia, Università di Padova, Via Marzolo 8, I-35131 Padova (Italy)

2013-08-31

Germanium samples, implanted with aluminum and annealed, have been investigated by micro-Raman spectroscopy using different excitation lines with the aim of gaining insights about the Al distribution at different depths beneath the sample surface and to correlate the Raman spectra with the electrical and chemical profiles, obtained by Spreading Resistance Profiling (SRP) and Secondary Ions Mass Spectrometry (SIMS) measurements, respectively. The intensity of the Al–Ge Raman peak at about 370 cm{sup −1}, due to the local vibrational mode of the substitutional Al atoms in the Ge matrix, has been directly related to the SRP behavior, while no correlation has been observed with SIMS profiles. These findings show that the electrically active content is entirely due to the substitutional Al atoms. Finally, a clear down shift is observed for the Ge–Ge Raman peak at ∼ 300 cm{sup −1}, which also seems to be directly related to the active content of Al dopant atoms. This work shows that micro-Raman spectroscopy can be a suitable tool for the study of doping profiles in Ge. - Highlights: ► Al-implanted Ge and annealed were studied by micro-Raman spectroscopy. ► Using different laser lines we have investigated the implants at different depths. ► The Al–Ge Raman peak at about 370 cm{sup −1} is directly related to the SRP behavior. ► The electrically active content is entirely due to the substitutional Al atoms. ► Carrier effects are observed on the Ge–Ge peak at ∼ 300 cm{sup −1}.

Investigation of germanium implanted with aluminum by multi-laser micro-Raman spectroscopy

International Nuclear Information System (INIS)

Sanson, A.; Napolitani, E.; Impellizzeri, G.; Giarola, M.; De Salvador, D.; Privitera, V.; Priolo, F.; Mariotto, G.; Carnera, A.

2013-01-01

Germanium samples, implanted with aluminum and annealed, have been investigated by micro-Raman spectroscopy using different excitation lines with the aim of gaining insights about the Al distribution at different depths beneath the sample surface and to correlate the Raman spectra with the electrical and chemical profiles, obtained by Spreading Resistance Profiling (SRP) and Secondary Ions Mass Spectrometry (SIMS) measurements, respectively. The intensity of the Al–Ge Raman peak at about 370 cm −1 , due to the local vibrational mode of the substitutional Al atoms in the Ge matrix, has been directly related to the SRP behavior, while no correlation has been observed with SIMS profiles. These findings show that the electrically active content is entirely due to the substitutional Al atoms. Finally, a clear down shift is observed for the Ge–Ge Raman peak at ∼ 300 cm −1 , which also seems to be directly related to the active content of Al dopant atoms. This work shows that micro-Raman spectroscopy can be a suitable tool for the study of doping profiles in Ge. - Highlights: ► Al-implanted Ge and annealed were studied by micro-Raman spectroscopy. ► Using different laser lines we have investigated the implants at different depths. ► The Al–Ge Raman peak at about 370 cm −1 is directly related to the SRP behavior. ► The electrically active content is entirely due to the substitutional Al atoms. ► Carrier effects are observed on the Ge–Ge peak at ∼ 300 cm −1

Depth profiling by Raman spectroscopy of high-energy ion irradiated silicon carbide

Energy Technology Data Exchange (ETDEWEB)

Wang, Xu; Zhang, Yanwen; Liu, Shiyi; Zhao, Ziqiang, E-mail: zqzhao@pku.edu.cn

2014-01-15

Single crystals of 6H–SiC were irradiated at room temperature with 20 MeV carbon ions at fluences of 1.5 × 10{sup 15} and 6.0 × 10{sup 15} cm{sup −2}. Raman measurements were performed to study irradiation induced damage and the in-depth damage profile of SiC. A clear change of damage from the surface down to the stopping region of carbon ions as simulated by SRIM is exhibited. The affected area as detected by Raman is in good agreement with SRIM predictions while a little shallower dpa profile is observed. The partial disorder defined in the present work as a function of depth is demonstrated. A shift of the position of the TO peak towards lower wavenumbers with in-depth damage and then to higher wavenumbers beyond the most damaged region indicates that tensile strain due to defects has a backward V-curve distribution. The damaged layer is subjected to a compressive in-plane stress associated with the out-of-plane strain and the magnitude of this stress also has a backward V-curve depth profile. The evolution of line width of the TO peak with depth clearly shows the density of defects reaches the higher level at the most damaged region. The Raman spectroscopy scanning technique is proved to be a powerful tool for profiling of crystal damage induced by high-energy ion implantation.

Blueberry juices: a rapid multi-analysis of quality indicators by means of dispersive Raman spectroscopy excited at 1064 nm

Science.gov (United States)

Ciaccheri, L.; Yuan, T.; Zhang, S.; Mencaglia, A. A.; Trono, C.; Yuan, L.; Mignani, A. G.

2017-04-01

Blueberry juices produced in China and in Italy were analyzed by means of Raman spectroscopy. The reference data of important nutraceutical indicators such as degrees Brix and carbohydrates were available. Some juices were produced from fresh organic fruits, while others were industrial grade, differing in qualities and prices. Raman spectra obtained with excitation at 1064 nm were acquired using a dispersive fiber-optic spectrometer. Degrees Brix were measured by means of a commercial refractometer, while carbohydrate contents were available from the producers. Multivariate processing was used for predicting Brix and carbohydrates from Raman spectra and from the reference data. Determination coefficients equal to 0.88 and 0.84, respectively, were obtained. This experiment further confirms the excellent potentials of Raman spectroscopy for both non-destructive and rapid assessments of food quality.

Resonant Impulsive Stimulated Raman Scattering

Energy Technology Data Exchange (ETDEWEB)

Mokhtari, A; Chesnoy, J

1988-03-15

Using a femtosecond dye laser, we observe in real-time vibrational oscillations excited by impulsive stimulated Raman scattering (ISRS) close to an electronic resonance. We perform single-beam Raman excitation and probe the driven coherence by a polarization-sensitive detection. We demonstrate for the first time impulsively Raman-induced dichroism, birefringence as well as frequency and time delay shifts. We analyse the characteristics of resonant ISRS on a vibrational mode of a dye molecule (malachite green) in solution.

Resonant Impulsive Stimulated Raman Scattering

International Nuclear Information System (INIS)

Mokhtari, A.; Chesnoy, J.

1988-01-01

Using a femtosecond dye laser, we observe in real-time vibrational oscillations excited by impulsive stimulated Raman scattering (ISRS) close to an electronic resonance. We perform single-beam Raman excitation and probe the driven coherence by a polarization-sensitive detection. We demonstrate for the first time impulsively Raman-induced dichroism, birefringence as well as frequency and time delay shifts. We analyse the characteristics of resonant ISRS on a vibrational mode of a dye molecule (malachite green) in solution

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

Science.gov (United States)

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 H 2 O 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

Raman Spectra from Pesticides on the Surface of Fruits

International Nuclear Information System (INIS)

Zhang, P X; Zhou Xiaofang; Cheng, Andrew Y S; Fang Yan

2006-01-01

Raman spectra of several vegetables and fruits were studied by micro-Raman spectrometer (514.5 nm) and Near-infrared Fourier Transform Raman spectrometer (FTRaman). It is shown that at 514.5 nm excitation, most of the spectra are from that of carotene with some very strong fluorescence in some cases. While at 1064 nm wavelength excitation, the spectra from the different samples demonstrate different characteristic Raman spectra without fluorescence. We discuss the spectroscopic difference by the two excitation wavelengths, and the application of Raman spectra for detection of pesticides left on the surface of vegetables and fruits. Raman spectra of fruits and pesticides were successfully recorded, and using the FT-Raman spectra the pesticides left on the surface of the fruits can be detected conveniently

Lidar sprectroscopy instrument (LISSI): An infrastructure facility for chemical aerosol profiling at the University of Hertfordshire

Science.gov (United States)

Tesche, Matthias; Tatarov, Boyan; Noh, Youngmin; Müller, Detlef

2018-04-01

The lidar development at the University of Hertfordshire explores the feasibility of using Raman backscattering for chemical aerosol profiling. This paper provides an overview of the new facility. A high-power Nd:YAG/OPO setup is used to excite Raman backscattering at a wide range of wavelengths. The receiver combines a spectrometer with a 32-channel detector or an ICCD camera to resolve Raman signals of various chemical compounds. The new facility will open new avenues for chemical profiling of aerosol pollution from measurements of Raman scattering by selected chemical compounds, provide data that allow to close the gap between optical and microphysical aerosol profiling with lidar and enables connecting lidar measurements to parameters used in atmospheric modelling.

Dark excited states of carotenoid in light harvesting complex probing with femtosecond stimulated Raman spectroscopy

Directory of Open Access Journals (Sweden)

Sakai S.

2013-03-01

Full Text Available Vibrational dynamics of dark excited states in carotenoids have been investigated using tunable Raman pump pulses. The S1 state has same vibrational dynamics in light-harvesting complex (LH1 and solution. The S* state in LH1 has similar vibrational modes with the triplet state of carotenoid. However, the so-called S* state in solution does not have the modes and is concluded to be different from the S* state in LH1.

Resonance Raman spectra of the copper-sulfur chromophores in Achromobacter cycloclastes nitrite reductase.

Science.gov (United States)

Dooley, D M; Moog, R S; Liu, M Y; Payne, W J; LeGall, J

1988-10-15

Resonance Raman spectroscopy at ambient temperature and 77 K has been used to probe the structures of the copper sites in Achromobacter cycloclastes nitrite reductase. This enzyme contains three copper ions per protein molecule and has two principal electronic absorption bands with lambda max values of 458 and 585 nm. Comparisons between the resonance Raman spectra of nitrite reductase and blue copper proteins establish that both the 458 and 585 nm bands are associated with Cu(II)-S(Cys) chromophores. A histidine ligand probably is also present. Different sets of vibrational frequencies are observed with 457.9 nm (ambient) or 476.1 nm (77 K) excitation as compared with 590 nm (ambient) or 593 nm (77 K) excitation. Excitation profiles indicate that the 458 and 585 nm absorption bands are associated with separate [Cu(II)-S(Cys)N(His)] sites or with inequivalent and uncoupled cysteine ligands in the same site. The former possibility is considered to be more likely.

Calibration of Raman lidar water vapor profiles by means of AERONET photometer observations and GDAS meteorological data

Science.gov (United States)

Dai, Guangyao; Althausen, Dietrich; Hofer, Julian; Engelmann, Ronny; Seifert, Patric; Bühl, Johannes; Mamouri, Rodanthi-Elisavet; Wu, Songhua; Ansmann, Albert

2018-05-01

We present a practical method to continuously calibrate Raman lidar observations of water vapor mixing ratio profiles. The water vapor profile measured with the multiwavelength polarization Raman lidar class="text">PollyXT is calibrated by means of co-located AErosol RObotic NETwork (AERONET) sun photometer observations and Global Data Assimilation System (GDAS) temperature and pressure profiles. This method is applied to lidar observations conducted during the Cyprus Cloud Aerosol and Rain Experiment (CyCARE) in Limassol, Cyprus. We use the GDAS temperature and pressure profiles to retrieve the water vapor density. In the next step, the precipitable water vapor from the lidar observations is used for the calibration of the lidar measurements with the sun photometer measurements. The retrieved calibrated water vapor mixing ratio from the lidar measurements has a relative uncertainty of 11 % in which the error is mainly caused by the error of the sun photometer measurements. During CyCARE, nine measurement cases with cloud-free and stable meteorological conditions are selected to calculate the precipitable water vapor from the lidar and the sun photometer observations. The ratio of these two precipitable water vapor values yields the water vapor calibration constant. The calibration constant for the class="text">PollyXT Raman lidar is 6.56 g kg-1 ± 0.72 g kg-1 (with a statistical uncertainty of 0.08 g kg-1 and an instrumental uncertainty of 0.72 g kg-1). To check the quality of the water vapor calibration, the water vapor mixing ratio profiles from the simultaneous nighttime observations with Raman lidar and Vaisala radiosonde sounding are compared. The correlation of the water vapor mixing ratios from these two instruments is determined by using all of the 19 simultaneous nighttime measurements during CyCARE. Excellent agreement with the slope of 1.01 and the R2 of 0.99 is found. One example is presented to demonstrate the full potential of a well-calibrated Raman

Ultraviolet Resonant Raman Enhancements in the Detection of Explosives

Energy Technology Data Exchange (ETDEWEB)

Short Jr., Billy Joe [Naval Postgraduate School, Monterey, CA (United States)

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.

Analysis of the in vivo confocal Raman spectral variability in human skin

Science.gov (United States)

Mogilevych, Borys; dos Santos, Laurita; Rangel, Joao L.; Grancianinov, Karen J. S.; Sousa, Mariane P.; Martin, Airton A.

2015-06-01

Biochemical composition of the skin changes in each layer and, therefore, the skin spectral profile vary with the depth. In this work, in vivo Confocal Raman spectroscopy studies were performed at different skin regions and depth profile (from the surface down to 10 μm) of the stratum corneum, to verify the variability and reproducibility of the intra- and interindividual Raman data. The Raman spectra were collected from seven healthy female study participants using a confocal Raman system from Rivers Diagnostic, with 785 nm excitation line and a CCD detector. Measurements were performed in the volar forearm region, at three different points at different depth, with the step of 2 μm. For each depth point, three spectra were acquired. Data analysis included the descriptive statistics (mean, standard deviation and residual) and Pearson's correlation coefficient calculation. Our results show that inter-individual variability is higher than intraindividual variability, and variability inside the SC is higher than on the skin surface. In all these cases we obtained r values, higher than 0.94, which correspond to high correlation between Raman spectra. It reinforces the possibility of the data reproducibility and direct comparison of in vivo results obtained with different study participants of the same age group and phototype.

In situ oxidation state profiling of nickel hexacyanoferrate derivatized electrodes using line-imaging Raman spectroscopy and multivariate calibration

International Nuclear Information System (INIS)

Haight, S.M.; Schwartz, D.T.

1999-01-01

Metal hexacyanoferrate compounds show promise as electrochemically switchable ion exchange materials for use in the cleanup of radioactive wastes such as those found in storage basins and underground tanks at the Department of Energy's Hanford Nuclear Reservation. Reported is the use of line-imaging Raman spectroscopy for the in situ determination of oxidation state profiles in nickel hexacyanoferrate derivatized electrodes under potential control in an electrochemical cell. Line-imaging Raman spectroscopy is used to collect 256 contiguous Raman spectra every ∼5 microm from thin films (ca. 80 nm) formed by electrochemical derivatization of nickel electrodes. The cyanide stretching region of the Raman spectrum of the film is shown to be sensitive to iron oxidation state and is modeled by both univariate and multivariate correlations. Although both correlations fit the calibration set well, the multivariate (principle component regression or PCR) model's predictions of oxidation state are less sensitive to noise in the spectrum, yielding a much smoother oxidation state profile than the univariate model. Oxidation state profiles with spatial resolution of approximately 5 microm are shown for a nickel hexacyanoferrate derivatized electrode in reduced, intermediate, and oxidized states. In situ oxidation state profiles indicate that the 647.1 nm laser illumination photo-oxidizes the derivatized electrodes. This observation is confirmed using photoelectrochemical methods

An innovative rotational Raman lidar to measure the temperature profile from the surface to 30 km altitude

Science.gov (United States)

Hauchecorne, Alain; Keckhut, Philippe; Mariscal, Jean-François; d'Almeida, Eric; Dahoo, Pierre-Richard; Porteneuve, Jacques

2016-06-01

A concept of innovative rotational Raman lidar with daylight measurement capability is proposed to measure the vertical profile of temperature from the ground to the middle stratosphere. The optical filtering is made using a Fabry-Pérot Interferometer with line spacing equal to the line spacing of the Raman spectrum. The detection is made using a linear PMT array operated in photon counting mode. We plan to build a prototype and to test it at the Haute-Provence Observatory lidar facility. to achieve a time resolution permitting the observation of small-scale atmospheric processes playing a role in the troposphere-stratosphere interaction as gravity waves. If successful, this project will open the possibility to consider a Raman space lidar for the global observation of atmospheric temperature profiles.

All-Fiber Raman Probe

DEFF Research Database (Denmark)

Brunetti, Anna Chiara

by means of fiber components. Assuming the possibility to use a fiber laser with a fundamental radiation at 1064nm, in-fiber efficient second harmonic generation is achieved by optically poling the core of the waveguide delivering the excitation light to the sample. In this way, Raman spectroscopy...... in the visible range can be performed. The simultaneous delivery of the excitation light and collection of the Raman signal from the sample are achieved by means of a doubleclad fiber, whose core and inner cladding act as \\independent" transmission channels. A double-clad fiber coupler allows for the recovery...... of the collected Raman scattering from the inner-cladding region of the double-clad fiber, thus replacing the bulk dichroic component normally used to demultiplex the pump and Raman signal. A tunable Rayleigh-rejection filter based on a liquid filled-photonic bandgap fiber is also demonstrated in this work...

Profile disparity of Raman-scattered O VI in symbiotic stars

International Nuclear Information System (INIS)

Lee, Hee-Won

2016-01-01

Symbiotic stars are wide binary systems consisting of a hot compact star (usually a white dwarf) and a mass losing giant. Symbiotic activities are believed to occur through gravitational capture of a fraction of the slow stellar wind from the giant. Raman scattered features of O VI resonance doublet 1032 and 1038 appearing at around 6825 Å and 7082 Å are a unique spectroscopic diagnostic tool to probe the mass transfer process in symbiotic stars. The Raman O VI features often exhibit multiple peak structures and in many cases the blue peak of 7082 features is relatively more suppressed than that of 6825 features. We propose that the disparity of the two profiles is attributed to the local variation of optical depths of O VI, implying that the accretion flow is convergent in the red emission region and divergent in the blue emission region. It is argued in this presentation that Raman scattering by atomic hydrogen is a natural mirror to provide an edge-on view of the accretion disk and a lateral view of the bipolar outflow in symbiotic stars. We discuss the spectropolarimetric implications of this interpretation. (paper)

An innovative rotational Raman lidar to measure the temperature profile from the surface to 30 km altitude

Directory of Open Access Journals (Sweden)

Hauchecorne Alain

2016-01-01

Full Text Available A concept of innovative rotational Raman lidar with daylight measurement capability is proposed to measure the vertical profile of temperature from the ground to the middle stratosphere. The optical filtering is made using a Fabry-Pérot Interferometer with line spacing equal to the line spacing of the Raman spectrum. The detection is made using a linear PMT array operated in photon counting mode. We plan to build a prototype and to test it at the Haute-Provence Observatory lidar facility. to achieve a time resolution permitting the observation of small-scale atmospheric processes playing a role in the troposphere-stratosphere interaction as gravity waves. If successful, this project will open the possibility to consider a Raman space lidar for the global observation of atmospheric temperature profiles.

Raman Probe Based on Optically-Poled Double-Core Fiber

DEFF Research Database (Denmark)

Brunetti, Anna Chiara; Margulis, Walter; Rottwitt, Karsten

2012-01-01

A Raman probe based on an optically-poled double-core fiber. In-fiber SHG allows for Raman spectroscopy of DMSO at 532nm when illuminating the fiber with 1064nm light. The fiber structure provides independent excitation and collection paths.......A Raman probe based on an optically-poled double-core fiber. In-fiber SHG allows for Raman spectroscopy of DMSO at 532nm when illuminating the fiber with 1064nm light. The fiber structure provides independent excitation and collection paths....

Confocal Raman Microscopy

CERN Document Server

Dieing, Thomas; Toporski, Jan

2011-01-01

Confocal Raman Microscopy is a relatively new technique that allows chemical imaging without specific sample preparation. By integrating a sensitive Raman spectrometer within a state-of-the-art microscope, Raman microscopy with a spatial resolution down to 200nm laterally and 500nm vertically can be achieved using visible light excitation. Recent developments in detector and computer technology as well as optimized instrument design have reduced integration times of Raman spectra by orders of magnitude, so that complete images consisting of tens of thousands of Raman spectra can be acquired in seconds or minutes rather than hours, which used to be standard just one decade ago. The purpose of this book is to provide the reader a comprehensive overview of the rapidly developing field of Confocal Raman Microscopy and its applications.

Effects of excitation spectral width on decay profile of weakly confined excitons

International Nuclear Information System (INIS)

Kojima, O.; Isu, T.; Ishi-Hayase, J.; Kanno, A.; Katouf, R.; Sasaki, M.; Tsuchiya, M.

2008-01-01

We report the effect due to a simultaneous excitation of several exciton states on the radiative decay profiles on the basis of the nonlocal response of weakly confined excitons in GaAs thin films. In the case of excitation of single exciton state, the transient grating signal has two decay components. The fast decay component comes from nonlocal response, and the long-lived component is attributed to free exciton decay. With an increase of excitation spectral width, the nonlocal component becomes small in comparison with the long-lived component, and disappears under irradiation of a femtosecond-pulse laser with broader spectral width. The transient grating spectra clearly indicates the contribution of the weakly confined excitons to the signal, and the exciton line width hardly changes by excitation spectral width. From these results, we concluded that the change of decay profile is attributed not to the many-body effect but to the effect of simultaneous excitation of several exciton states

Highly sensitive high resolution Raman spectroscopy using resonant ionization methods

International Nuclear Information System (INIS)

Owyoung, A.; Esherick, P.

1984-05-01

In recent years, the introduction of stimulated Raman methods has offered orders of magnitude improvement in spectral resolving power for gas phase Raman studies. Nevertheless, the inherent weakness of the Raman process suggests the need for significantly more sensitive techniques in Raman spectroscopy. In this we describe a new approach to this problem. Our new technique, which we call ionization-detected stimulated Raman spectroscopy (IDSRS), combines high-resolution SRS with highly-sensitive resonant laser ionization to achieve an increase in sensitivity of over three orders of magnitude. The excitation/detection process involves three sequential steps: (1) population of a vibrationally excited state via stimulated Raman pumping; (2) selective ionization of the vibrationally excited molecule with a tunable uv source; and (3) collection of the ionized species at biased electrodes where they are detected as current in an external circuit

Subwavelength Localization of Atomic Excitation Using Electromagnetically Induced Transparency

Directory of Open Access Journals (Sweden)

J. A. Miles

2013-09-01

Full Text Available We report an experiment in which an atomic excitation is localized to a spatial width that is a factor of 8 smaller than the wavelength of the incident light. The experiment utilizes the sensitivity of the dark state of electromagnetically induced transparency (EIT to the intensity of the coupling laser beam. A standing-wave coupling laser with a sinusoidally varying intensity yields tightly confined Raman excitations during the EIT process. The excitations, located near the nodes of the intensity profile, have a width of 100 nm. The experiment is performed using ultracold ^{87}Rb atoms trapped in an optical dipole trap, and atomic localization is achieved with EIT pulses that are approximately 100 ns long. To probe subwavelength atom localization, we have developed a technique that can measure the width of the atomic excitations with nanometer spatial resolution.

Raman scattering in condensed media placed in photon traps

Science.gov (United States)

Goncharov, A. P.; Gorelik, V. S.; Krawtsow, A. V.

2007-11-01

A new type of resonator cells (photon traps) has been worked out, which ensures the Raman opalescence regime (i.e., the conditions under which the relative Raman scattering intensity at the outlet of the cells increases significantly as compared to the exciting line intensity. The Raman scattering spectra of a number of organic and inorganic compounds placed in photon traps are studied under pulse-periodic excitation by a copper-vapor laser.

The Raman effect and its application to electronic spectroscopies in metal-centered species : Techniques and investigations in ground and excited states

NARCIS (Netherlands)

Browne, W.R.; J. McGarvey, J.

In the decades since its discovery and somewhat limited early applications, Raman scattering has become the basis for the development of a variety of methods for probing molecular structure both in ground and electronically excited states. In this review, following a brief look at the underlying

Development of a Raman spectrometer to study surface-enhanced Raman scattering

International Nuclear Information System (INIS)

Biswas, Nandita; Chadha, Ridhima; Kapoor, Sudhir; Sarkar, Sisir K.; Mukherjee, Tulsi

2011-02-01

Raman spectroscopy is an important tool, which provides enormous information on the vibrational and structural details of materials. This understanding is not only interesting due to its fundamental importance, but also of considerable importance in optoelectronics and device applications of these materials in nanotechnology. In this report, we begin with a brief introduction on the Raman effect and various Raman scattering techniques, followed by a detailed discussion on the development of an instrument with home-built collection optics attachment. This Raman system consists of a pulsed laser excitation source, a sample compartment, collection optics to collect the scattered light, a notch filter to reject the intense laser light, a monochromator to disperse the scattered light and a detector to detect the Raman signal. After calibrating the Raman spectrometer with standard solvents, we present our results on Surface-Enhanced Raman Scattering (SERS) investigations on three different kinds of chemical systems. (author)

Micro-Raman depth profile investigations of beveled Al+-ion implanted 6H-SiC samples

International Nuclear Information System (INIS)

Zuk, J.; Romanek, J.; Skorupa, W.

2009-01-01

6H-SiC single crystals were implanted with 450 keV Al + -ions to a fluence of 3.4 x 10 15 cm -2 , and in a separate experiment subjected to multiple Al + implantations with the four energies: 450, 240, 115 and 50 keV and different fluences to obtain rectangular-like depth distributions of Al in SiC. The implantations were performed along [0 0 0 1] channeling and non-channeling ('random') directions. Subsequently, the samples were annealed for 10 min at 1650 deg. C in an argon atmosphere. The depth profiles of the implanted Al atoms were obtained by secondary ion mass spectrometry (SIMS). Following implantation and annealing, the samples were beveled by mechanical polishing. Confocal micro-Raman spectroscopic investigations were performed with a 532 nm wavelength laser beam of a 1 μm focus diameter. The technique was used to determine precisely the depth profiles of TO and LO phonon lines intensity in the beveled samples to a depth of about 2000 nm. Micro-Raman spectroscopy was also found to be useful in monitoring very low levels of disorder remaining in the Al + implanted and annealed 6H-SiC samples. The micro-Raman technique combined with sample beveling also made it possible the determination of optical absorption coefficient profiles in implanted subsurface layers.

Inelastic electron and Raman scattering from the collective excitations in quantum wires: Zero magnetic field

Directory of Open Access Journals (Sweden)

Manvir S. Kushwaha

2013-04-01

intrasubband and intersubband single-particle as well as collective excitations], the loss functions for the IES and the Raman intensity for the ILS. We observe that it is the collective (plasmon excitations that largely contribute to the predominant peaks in the energy-loss and the Raman spectra. The inductive reasoning is that the IES can be a potential alternative of the overused ILS for investigating collective excitations in quantum wires. We trust that this research work shall be useful to all – from novice to expert and from theorist to experimentalist – who believe in the power of traditional science.

Development of a miRNA surface-enhanced Raman scattering assay using benchtop and handheld Raman systems

Science.gov (United States)

Schechinger, Monika; Marks, Haley; Locke, Andrea; Choudhury, Mahua; Cote, Gerard

2018-01-01

DNA-functionalized nanoparticles, when paired with surface-enhanced Raman spectroscopy (SERS), can rapidly detect microRNA. However, widespread use of this approach is hindered by drawbacks associated with large and expensive benchtop Raman microscopes. MicroRNA-17 (miRNA-17) has emerged as a potential epigenetic indicator of preeclampsia, a condition that occurs during pregnancy. Biomarker detection using an SERS point-of-care device could enable prompt diagnosis and prevention as early as the first trimester. Recently, strides have been made in developing portable Raman systems for field applications. An SERS assay for miRNA-17 was assessed and translated from traditional benchtop Raman microscopes to a handheld system. Three different photoactive molecules were compared as potential Raman reporter molecules: a chromophore, malachite green isothiocyanate (MGITC), a fluorophore, tetramethylrhodamine isothiocyanate, and a polarizable small molecule 5,5-dithio-bis-(2-nitrobenzoic acid) (DTNB). For the benchtop Raman microscope, the DTNB-labeled assay yielded the greatest sensitivity under 532-nm laser excitation, but the MGITC-labeled assay prevailed at 785 nm. Conversely, DTNB was preferable for the miniaturized 785-nm Raman system. This comparison showed significant SERS enhancement variation in response to 1-nM miRNA-17, implying that the sensitivity of the assay may be more heavily dependent on the excitation wavelength, instrumentation, and Raman reporter chosen than on the plasmonic coupling from DNA/miRNA-mediated nanoparticle assemblies.

Theoretical investigation of the hyper-Raman scattering in hexagonal semiconductors under two-photon excitation near resonance with the An=2 exciton level

Science.gov (United States)

Semenova, L. E.

2018-04-01

The hyper-Raman scattering of light by LO-phonons under two-photon excitation near resonance with the An=2 exciton level in the wurtzite semiconductors A2B6 was theoretically investigated, taking into account the influence of the complex structure of the top valence band.

Resonance Raman spectra of wurtzite and zincblende CdSe nanocrystals

Energy Technology Data Exchange (ETDEWEB)

Kelley, Anne Myers, E-mail: amkelley@ucmerced.edu [Chemistry and Chemical Biology, School of Natural Sciences, University of California, 5200 North Lake Road, Merced, CA 95343 (United States); Dai, Quanqin; Jiang, Zhong-jie; Baker, Joshua A.; Kelley, David F. [Chemistry and Chemical Biology, School of Natural Sciences, University of California, 5200 North Lake Road, Merced, CA 95343 (United States)

2013-08-30

Highlights: ► Very similar resonance Raman spectra of wurtzite and zincblende CdSe nanocrystals. ► First absolute resonance Raman cross-sections reported for CdSe nanocrystals. ► LO overtones suggest slightly stronger electron–phonon coupling in wurtzite form. - Abstract: Resonance Raman spectra and absolute differential Raman cross-sections have been measured for CdSe nanocrystals in both the wurtzite and zincblende crystal forms at four excitation wavelengths from 457.9 to 514.5 nm. The frequency and bandshape of the longitudinal optical (LO) phonon fundamental is essentially identical for both crystal forms at each excitation wavelength. The LO phonon overtone to fundamental intensity ratio appears to be slightly higher for the wurtzite form, which may suggest slightly stronger exciton–phonon coupling from the Fröhlich mechanism in the wurtzite form. The LO fundamental Raman cross-sections are very similar for both crystal forms at each excitation wavelength.

Prospects for in vivo Raman spectroscopy

International Nuclear Information System (INIS)

Hanlon, E.B.; Manoharan, R.; Koo, T.-W.; Shafer, K.E.; Motz, J.T.; Fitzmaurice, M.; Kramer, J.R.; Itzkan, I.; Dasari, R.R.; Feld, M.S.

2000-01-01

Raman spectroscopy is a potentially important clinical tool for real-time diagnosis of disease and in situ evaluation of living tissue. The purpose of this article is to review the biological and physical basis of Raman spectroscopy of tissue, to assess the current status of the field and to explore future directions. The principles of Raman spectroscopy and the molecular level information it provides are explained. An overview of the evolution of Raman spectroscopic techniques in biology and medicine, from early investigations using visible laser excitation to present-day technology based on near-infrared laser excitation and charge-coupled device array detection, is presented. State-of-the-art Raman spectrometer systems for research laboratory and clinical settings are described. Modern methods of multivariate spectral analysis for extracting diagnostic, chemical and morphological information are reviewed. Several in-depth applications are presented to illustrate the methods of collecting, processing and analysing data, as well as the range of medical applications under study. Finally, the issues to be addressed in implementing Raman spectroscopy in various clinical applications, as well as some long-term directions for future study, are discussed. (author)

Surface-Enhanced Raman Scattering Physics and Applications

CERN Document Server

Kneipp, Katrin; Kneipp, Harald

2006-01-01

Almost 30 years after the first reports on surface-enhanced Raman signals, the phenomenon of surface-enhanced Raman scattering (SERS) is now well established. Yet, explaining the enhancement of a spectroscopic signal by fouteen orders of magnitude continues to attract the attention of physicists and chemists alike. And, at the same time and rapidly growing, SERS is becoming a very useful spectroscopic tool with exciting applications in many fields. SERS gained particular interest after single-molecule Raman spectroscopy had been demonstrated. This bookl summarizes and discusses present theoretical approaches that explain the phenomenon of SERS and reports on new and exciting experiments and applications of the fascinating spectroscopic effect.

Detection of biologically active diterpenoic acids by Raman Spectroscopy

DEFF Research Database (Denmark)

Talian, Ivan; Orinak, Andrej; Efremov, Evtim V.

2010-01-01

Three poorly detectable, biologically active diterpenoic acids, kaurenoic, abietic, and gibberellic acid, were studied by using different modes of Raman spectroscopy. Because of their structural similarities, in the absence of strongly polarizable groups, conventional Raman spectroscopy is not su......Three poorly detectable, biologically active diterpenoic acids, kaurenoic, abietic, and gibberellic acid, were studied by using different modes of Raman spectroscopy. Because of their structural similarities, in the absence of strongly polarizable groups, conventional Raman spectroscopy...... few enhanced Raman lines. SERS spectra with 514-nm excitation with Ag colloids were also relatively weak. The best SERS spectrawere obtained with 785-nm excitation on a novel nanostructured substrate, 'black silicon' coated with a 400-nm gold layer. The spectra showed clear differences...

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

International Nuclear Information System (INIS)

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

2013-01-01

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

Frequency-asymmetric gain profile in a seeded Raman amplifier

International Nuclear Information System (INIS)

Repasky, K.S.; Carlsten, J.L.

1996-01-01

This paper examines the effect of index guiding on Raman gain. The slowly varying Maxwell wave equation including both the real and imaginary parts of the Raman susceptibility for a seeded Raman amplifier is explored. Using a Gauss-Laguerre mode expansion for the Stokes field, the output Stokes energy is numerically studied as a function of gain and detuning from the Raman resonance. The calculations indicate that the real part of the Raman susceptibility causes the Raman medium to act as a lens when the Stokes seed is detuned from the Raman resonance. This focusing effect leads to higher peak Stokes energy when the Stokes seed is tuned to the blue side of the Raman resonance. Specifically for Raman scattering in H 2 with a pump laser at 532 nm and an input seed near 683 nm, the peak Stokes energy can shift by as much as 300 MHz from the Raman resonance. An experiment which confirms these predictions is also presented. copyright 1996 The American Physical Society

Ultraviolet Raman scattering from persistent chemical warfare agents

Science.gov (United States)

Kullander, Fredrik; Wästerby, Pär.; Landström, Lars

2016-05-01

Laser induced Raman scattering at excitation wavelengths in the middle ultraviolet was examined using a pulsed tunable laser based spectrometer system. Droplets of chemical warfare agents, with a volume of 2 μl, were placed on a silicon surface and irradiated with sequences of laser pulses. The Raman scattering from V-series nerve agents, Tabun (GA) and Mustard gas (HD) was studied with the aim of finding the optimum parameters and the requirements for a detection system. A particular emphasis was put on V-agents that have been previously shown to yield relatively weak Raman scattering in this excitation band.

Development of a miRNA surface-enhanced Raman scattering assay using benchtop and handheld Raman systems.

Science.gov (United States)

Schechinger, Monika; Marks, Haley; Locke, Andrea; Choudhury, Mahua; Cote, Gerard

2018-01-01

DNA-functionalized nanoparticles, when paired with surface-enhanced Raman spectroscopy (SERS), can rapidly detect microRNA. However, widespread use of this approach is hindered by drawbacks associated with large and expensive benchtop Raman microscopes. MicroRNA-17 (miRNA-17) has emerged as a potential epigenetic indicator of preeclampsia, a condition that occurs during pregnancy. Biomarker detection using an SERS point-of-care device could enable prompt diagnosis and prevention as early as the first trimester. Recently, strides have been made in developing portable Raman systems for field applications. An SERS assay for miRNA-17 was assessed and translated from traditional benchtop Raman microscopes to a handheld system. Three different photoactive molecules were compared as potential Raman reporter molecules: a chromophore, malachite green isothiocyanate (MGITC), a fluorophore, tetramethylrhodamine isothiocyanate, and a polarizable small molecule 5,5-dithio-bis-(2-nitrobenzoic acid) (DTNB). For the benchtop Raman microscope, the DTNB-labeled assay yielded the greatest sensitivity under 532-nm laser excitation, but the MGITC-labeled assay prevailed at 785 nm. Conversely, DTNB was preferable for the miniaturized 785-nm Raman system. This comparison showed significant SERS enhancement variation in response to 1-nM miRNA-17, implying that the sensitivity of the assay may be more heavily dependent on the excitation wavelength, instrumentation, and Raman reporter chosen than on the plasmonic coupling from DNA/miRNA-mediated nanoparticle assemblies. (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

All-fiber Raman Probe using Higher Order Modes

DEFF Research Database (Denmark)

Larsen, Stine Højer Møller; Rishøj, Lars Søgaard; Rottwitt, Karsten

2013-01-01

We demonstrate the first all-fiber Raman probe utilizing higher order modes for the excitation. The spectrum of cyclohexane is measured using both the fundamental mode as well as in-fiber-generated Bessel-like modes.......We demonstrate the first all-fiber Raman probe utilizing higher order modes for the excitation. The spectrum of cyclohexane is measured using both the fundamental mode as well as in-fiber-generated Bessel-like modes....

The Raman Spectrum of the Squarate (C4O4-2 Anion: An Ab Initio Basis Set Dependence Study

Directory of Open Access Journals (Sweden)

Miranda Sandro G. de

2002-01-01

Full Text Available The Raman excitation profile of the squarate anion, C4O4-2 , was calculated using ab initio methods at the Hartree-Fock using Linear Response Theory (LRT for six excitation frequencies: 632.5, 514.5, 488.0, 457.9, 363.8 and 337.1 nm. Five basis set functions (6-31G*, 6-31+G*, cc-pVDZ, aug-cc-pVDZ and Sadlej's polarizability basis set were investigated aiming to evaluate the performance of the 6-31G* set for numerical convergence and computational cost in relation to the larger basis sets. All basis sets reproduce the main spectroscopic features of the Raman spectrum of this anion for the excitation interval investigated. The 6-31G* basis set presented, on average, the same accuracy of numerical results as the larger sets but at a fraction of the computational cost showing that it is suitable for the theoretical investigation of the squarate dianion and its complexes and derivatives.

Study of crystal-field excitations and Raman active phonons in o-DyMnO3

International Nuclear Information System (INIS)

Jandl, S.; Mansouri, S.; Mukhin, A.A.; Yu Ivanov, V.; Balbashov, A.; Gospodino, M.M.; Nekvasil, V.; Orlita, M.

2011-01-01

In DyMnO 3 orthorhombic single crystals, the weak Raman active phonon softening below T=100 K is correlated with the study of infrared active Dy 3+ CF excitations as a function of temperature and under applied magnetic field. We detect five H 13/2 CF transitions that we predict with appropriate CF Hamiltonian and we confirm that the magnetic easy axis lies in the ab plane. While the CF energy level shifts below T=100 K reflect different displacements of the oxygen ions that contribute to the phonon softening, lifting of the ground state Kramers doublet degeneracy (∼30 cm -1 ) is observed below T N =39 K due to the anisotropic Mn 3+ -Dy 3+ interaction, which could be responsible for the stability of the bc-cycloid ferroelectric phase. - Research highlights: → Origin of Raman active phonon softening in the multiferroic o-DyMnO 3 . → A crystal-field study under magnetic field of Dy 3+ in o-DyMnO 3 . → Location of the magnetic easy axis in o-DyMnO 3 . → Lifting of Kramers doublet degeneracy in o-DyMnO 3 .

Stimulated Raman scattering: old physics, new applications.

Science.gov (United States)

Yakovlev, Vladislav V; Petrov, Georgi I; Zhang, Hao F; Noojin, Gary D; Denton, Michael L; Thomas, Robert J; Scully, Marlan O

2009-10-01

Stimulated Raman scattering as a promising way of expanding the tunability of ultrafast lasers and as an exciting new biomedical imaging modality capable of selective excitation and chemically-specific diagnostics of molecular species.

Raman spectroscopic characterization of multiwall carbon nanotubes and of composites

Directory of Open Access Journals (Sweden)

L. Bokobza

2012-07-01

Full Text Available In this work Raman spectroscopy was used for extensive characterization of multiwall carbon nanotube (MWNTs and of MWCNTs/rubber composites. We have measured the Raman spectra of bundled and dispersed multiwall carbon nanotubes. All the Raman bands of the carbon nanotubes are seen to shift to higher wavenumbers upon debundling on account of less intertube interactions. Effects of laser irradiation were also investigated. Strong effects are observed by changing the wavelength of the laser excitation. On the other hand, at a given excitation wavelength, changes on the Raman bands are observed by changing the laser power density due to sample heating during the measurement procedure.

Retrieval method of aerosol extinction coefficient profile based on backscattering, side-scattering and Raman-scattering lidar

Science.gov (United States)

Shan, Huihui; Zhang, Hui; Liu, Junjian; Tao, Zongming; Wang, Shenhao; Ma, Xiaomin; Zhou, Pucheng; Yao, Ling; Liu, Dong; Xie, Chenbo; Wang, Yingjian

2018-03-01

Aerosol extinction coefficient profile is an essential parameter for atmospheric radiation model. It is difficult to get higher signal to noise ratio (SNR) of backscattering lidar from the ground to the tropopause especially in near range. Higher SNR problem can be solved by combining side-scattering and backscattering lidar. Using Raman-scattering lidar, aerosol extinction to backscatter ratio (lidar ratio) can be got. Based on side-scattering, backscattering and Raman-scattering lidar system, aerosol extinction coefficient is retrieved precisely from the earth's surface to the tropopause. Case studies show this method is reasonable and feasible.

Effects of phase and coupling between the vibrational modes on selective excitation in coherent anti-Stokes Raman scattering microscopy

International Nuclear Information System (INIS)

Patel, Vishesha; Malinovsky, Vladimir S.; Malinovskaya, Svetlana

2010-01-01

Coherent anti-Stokes Raman scattering (CARS) microscopy has been a major tool of investigation of biological structures as it contains the vibrational signature of molecules. A quantum control method based on chirped pulse adiabatic passage was recently proposed for selective excitation of a predetermined vibrational mode in CARS microscopy [Malinovskaya and Malinovsky, Opt. Lett. 32, 707 (2007)]. The method utilizes the chirp sign variation at the peak pulse amplitude and gives a robust adiabatic excitation of the desired vibrational mode. Using this method, we investigate the impact of coupling between vibrational modes in molecules on controllability of excitation of the CARS signal. We analyze two models of two coupled two-level systems (TLSs) having slightly different transitional frequencies. The first model, featuring degenerate ground states of the TLSs, gives robust adiabatic excitation and maximum coherence in the resonant TLS for positive value of the chirp. In the second model, implying nondegenerate ground states in the TLSs, a population distribution is observed in both TLSs, resulting in a lack of selectivity of excitation and low coherence. It is shown that the relative phase and coupling between the TLSs play an important role in optimizing coherence in the desired vibrational mode and suppressing unwanted transitions in CARS microscopy.

Two-dimensional electronic femtosecond stimulated Raman spectroscopy

Directory of Open Access Journals (Sweden)

Ogilvie J.P.

2013-03-01

Full Text Available We report two-dimensional electronic spectroscopy with a femtosecond stimulated Raman scattering probe. The method reveals correlations between excitation energy and excited state vibrational structure following photoexcitation. We demonstrate the method in rhodamine 6G.

Near-infrared-excited confocal Raman spectroscopy advances in vivo diagnosis of cervical precancer.

Science.gov (United States)

Duraipandian, Shiyamala; Zheng, Wei; Ng, Joseph; Low, Jeffrey J H; Ilancheran, Arunachalam; Huang, Zhiwei

2013-06-01

Raman spectroscopy is a unique optical technique that can probe the changes of vibrational modes of biomolecules associated with tissue premalignant transformation. This study evaluates the clinical utility of confocal Raman spectroscopy over near-infrared (NIR) autofluorescence (AF) spectroscopy and composite NIR AF/Raman spectroscopy for improving early diagnosis of cervical precancer in vivo at colposcopy. A rapid NIR Raman system coupled with a ball-lens fiber-optic confocal Raman probe was utilized for in vivo NIR AF/Raman spectral measurements of the cervix. A total of 1240 in vivo Raman spectra [normal (n=993), dysplasia (n=247)] were acquired from 84 cervical patients. Principal components analysis (PCA) and linear discriminant analysis (LDA) together with a leave-one-patient-out, cross-validation method were used to extract the diagnostic information associated with distinctive spectroscopic modalities. The diagnostic ability of confocal Raman spectroscopy was evaluated using the PCA-LDA model developed from the significant principal components (PCs) [i.e., PC4, 0.0023%; PC5, 0.00095%; PC8, 0.00022%, (p<0.05)], representing the primary tissue Raman features (e.g., 854, 937, 1095, 1253, 1311, 1445, and 1654 cm(-1)). Confocal Raman spectroscopy coupled with PCA-LDA modeling yielded the diagnostic accuracy of 84.1% (a sensitivity of 81.0% and a specificity of 87.1%) for in vivo discrimination of dysplastic cervix. The receiver operating characteristic curves further confirmed that the best classification was achieved using confocal Raman spectroscopy compared to the composite NIR AF/Raman spectroscopy or NIR AF spectroscopy alone. This study illustrates that confocal Raman spectroscopy has great potential to improve early diagnosis of cervical precancer in vivo during clinical colposcopy.

Raman spectroscopy an intensity approach

CERN Document Server

Guozhen, Wu

2017-01-01

This book summarizes the highlights of our work on the bond polarizability approach to the intensity analysis. The topics covered include surface enhanced Raman scattering, Raman excited virtual states and Raman optical activity (ROA). The first chapter briefly introduces the Raman effect in a succinct but clear way. Chapter 2 deals with the normal mode analysis. This is a basic tool for our work. Chapter 3 introduces our proposed algorithm for the Raman intensity analysis. Chapter 4 heavily introduces the physical picture of Raman virtual states. Chapter 5 offers details so that the readers can have a comprehensive idea of Raman virtual states. Chapter 6 demonstrates how this bond polarizability algorithm is extended to ROA intensity analysis. Chapters 7 and 8 offer details on ROA, showing many findings on ROA mechanism that were not known or neglected before. Chapter 9 introduces our proposed classical treatment on ROA which, as combined with the results from the bond polarizability analysis, leads to a com...

Coherent population transfer and superposition of atomic states via stimulated Raman adiabatic passage using an excited-doublet four-level atom

International Nuclear Information System (INIS)

Jin Shiqi; Gong Shangqing; Li Ruxin; Xu Zhizhan

2004-01-01

Coherent population transfer and superposition of atomic states via a technique of stimulated Raman adiabatic passage in an excited-doublet four-level atomic system have been analyzed. It is shown that the behavior of adiabatic passage in this system depends crucially on the detunings between the laser frequencies and the corresponding atomic transition frequencies. Particularly, if both the fields are tuned to the center of the two upper levels, the four-level system has two degenerate dark states, although one of them contains the contribution from the excited atomic states. The nonadiabatic coupling of the two degenerate dark states is intrinsic, it originates from the energy difference of the two upper levels. An arbitrary superposition of atomic states can be prepared due to such nonadiabatic coupling effect

Ceilometer Aerosol Profiling versus Raman Lidar in the Frame of Interact Campaign of Actris

Directory of Open Access Journals (Sweden)

Madonna F.

2016-01-01

Full Text Available In this paper, multi-wavelength Raman lidar measurements are used to investigate the capability of ceilometers to provide reliable information about atmospheric aerosol properties through the INTERACT (INTERcomparison of Aerosol and Cloud Tracking campaign carried out at the CNR-IMAA Atmospheric Observatory (760 m a.s.l., 40.60 N, 15.72 E, in the framework of ACTRIS (Aerosol Clouds Trace gases Research InfraStructure FP7 project. This work is the first time that three different commercial ceilometers with an advanced Raman lidar are compared over a period of six month. The comparison of the attenuated backscatter coefficient profiles from a multi-wavelength Raman lidar and three ceilometers (CHM15k, CS135s, CT25K reveals differences due to the expected discrepancy in the SNR but also due to effect of changes in the ambient temperature on the stability of ceilometer calibration over short and mid-term. Technological improvements of ceilometers towards their operational use in the monitoring of the atmospheric aerosol in the low and free troposphere are likely needed.

Multivariate reference technique for quantitative analysis of fiber-optic tissue Raman spectroscopy.

Science.gov (United States)

Bergholt, Mads Sylvest; Duraipandian, Shiyamala; Zheng, Wei; Huang, Zhiwei

2013-12-03

We report a novel method making use of multivariate reference signals of fused silica and sapphire Raman signals generated from a ball-lens fiber-optic Raman probe for quantitative analysis of in vivo tissue Raman measurements in real time. Partial least-squares (PLS) regression modeling is applied to extract the characteristic internal reference Raman signals (e.g., shoulder of the prominent fused silica boson peak (~130 cm(-1)); distinct sapphire ball-lens peaks (380, 417, 646, and 751 cm(-1))) from the ball-lens fiber-optic Raman probe for quantitative analysis of fiber-optic Raman spectroscopy. To evaluate the analytical value of this novel multivariate reference technique, a rapid Raman spectroscopy system coupled with a ball-lens fiber-optic Raman probe is used for in vivo oral tissue Raman measurements (n = 25 subjects) under 785 nm laser excitation powers ranging from 5 to 65 mW. An accurate linear relationship (R(2) = 0.981) with a root-mean-square error of cross validation (RMSECV) of 2.5 mW can be obtained for predicting the laser excitation power changes based on a leave-one-subject-out cross-validation, which is superior to the normal univariate reference method (RMSE = 6.2 mW). A root-mean-square error of prediction (RMSEP) of 2.4 mW (R(2) = 0.985) can also be achieved for laser power prediction in real time when we applied the multivariate method independently on the five new subjects (n = 166 spectra). We further apply the multivariate reference technique for quantitative analysis of gelatin tissue phantoms that gives rise to an RMSEP of ~2.0% (R(2) = 0.998) independent of laser excitation power variations. This work demonstrates that multivariate reference technique can be advantageously used to monitor and correct the variations of laser excitation power and fiber coupling efficiency in situ for standardizing the tissue Raman intensity to realize quantitative analysis of tissue Raman measurements in vivo, which is particularly appealing in

A PROFILE ANALYSIS OF RAMAN-SCATTERED O VI BANDS AT 6825 Å AND 7082 Å IN SANDULEAK’S STAR

Energy Technology Data Exchange (ETDEWEB)

Heo, Jeong-Eun; Lee, Hee-Won [Department of Physics and Astronomy, Sejong University, Seoul (Korea, Republic of); Angeloni, Rodolfo [Gemini Observatory, Casilla 603, La Serena (Chile); Mille, Francesco Di [Las Campanas Observatory, Carnegie Observatories, Casilla 601, La Serena (Chile); Palma, Tali, E-mail: jeung6145@gmail.com [Departamento de Ciencias Físicas, Universidad Andrés Bello, Fernández Concha 700, Las Condes, Santiago (Chile)

2016-12-20

We present a detailed modeling of the two broad bands observed at 6825 and 7082 Å in Sanduleak’s star, a controversial object in the Large Magellanic Cloud. These bands are known to originate from Raman scattering of O vi  λ λ 1032 and 1038 photons with atomic hydrogen and are only observed in bona fide symbiotic stars. Our high-resolution spectrum obtained with the Magellan Inamori Kyocera Echelle spectrograph at the Magellan-Clay Telescope reveals, quite surprisingly, that the profiles of the two bands look very different: while the Raman 6825 Å band shows a single broad profile with a redward extended bump, the Raman 7082 Å band exhibits a distinct triple-peak profile. Our model suggests that the O vi emission nebula can be decomposed into a red, blue, and central emission region from an accretion disk, a bipolar outflow, and a further compact, optically thick region. We also perform Monte Carlo simulations with the aim of fitting the observed flux ratio F (6825)/ F (7082) ∼ 4.5, which indicates that the neutral region in Sanduleak’s star is characterized by the column density N{sub Hi} ∼ 1 × 10{sup 23} cm{sup −2}.

Quantitative analysis of sugar composition in honey using 532-nm excitation Raman and Raman optical activity spectra

Czech Academy of Sciences Publication Activity Database

Šugar, Jan; Bouř, Petr

2016-01-01

Roč. 47, č. 11 (2016), s. 1298-1303 ISSN 0377-0486 R&D Projects: GA ČR GA15-09072S Institutional support: RVO:61388963 Keywords : honey * sugar mixtures * spectral decompositions * Raman spectroscopy * Raman optical activity Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.969, year: 2016

Femtosecond time-resolved studies of coherent vibrational Raman scattering in large gas-phase molecules

International Nuclear Information System (INIS)

Hayden, C.C.; Chandler, D.W.

1995-01-01

Results are presented from femtosecond time-resolved coherent Raman experiments in which we excite and monitor vibrational coherence in gas-phase samples of benzene and 1,3,5-hexatriene. Different physical mechanisms for coherence decay are seen in these two molecules. In benzene, where the Raman polarizability is largely isotropic, the Q branch of the vibrational Raman spectrum is the primary feature excited. Molecules in different rotational states have different Q-branch transition frequencies due to vibration--rotation interaction. Thus, the macroscopic polarization that is observed in these experiments decays because it has many frequency components from molecules in different rotational states, and these frequency components go out of phase with each other. In 1,3,5-hexatriene, the Raman excitation produces molecules in a coherent superposition of rotational states, through (O, P, R, and S branch) transitions that are strong due to the large anisotropy of the Raman polarizability. The coherent superposition of rotational states corresponds to initially spatially oriented, vibrationally excited, molecules that are freely rotating. The rotation of molecules away from the initial orientation is primarily responsible for the coherence decay in this case. These experiments produce large (∼10% efficiency) Raman shifted signals with modest excitation pulse energies (10 μJ) demonstrating the feasibility of this approach for a variety of gas phase studies. copyright 1995 American Institute of Physics

Remote measurement of atmospheric temperature profiles in clouds with rotational Raman lidar; Fernmessung atmosphaerischer Temperaturprofile in Wolken mit Rotations-Raman-Lidar

Energy Technology Data Exchange (ETDEWEB)

Behrendt, A. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Physikalische und Chemische Analytik

2000-07-01

The development of a lidar receiver for remote measurements of atmospheric temperature profiles with the rotational Raman method is described. By a new receiver concept, this instrument allowed for the first time remote temperature measurements without any perturbation by the presence of clouds up to a backscatter ratio of 45. In addition, high efficiency of the spectral separation of atmospheric backscatter signals leads to improved measurement resolution: the minimum integration time needed for a statistical uncertainty < {+-}1 K at, e.g., 10 km height and 960 m height resolution is only 5 minutes. The measurement range extends to over 45 km altitude. Results of field campaigns obtained with the instrument are presented and discussed. In winter 1997/98, the instrument was transferred with the GKSS Raman lidar to Esrange (67.9 N, 21.1 E) in northern Sweden, where pioneering remote measurements of local temperatures in orographically induced polar stratospheric clouds could be carried out. (orig.)

Identification of resonant x-ray Raman scattering using SR- and conventional TXRF

International Nuclear Information System (INIS)

Zhu, Q.; Burrow, B.; Baur, K.; Brennan, S.; Pianetta, P.

2000-01-01

Analyzing and control the surface contamination are important steps in the processing of integrated circuits. The need for using non-destructive analysis techniques either as laboratory or in-line inspection tools has increased dramatically in the past. Total reflection x-ray fluorescence (TXRF) spectroscopy is one of the best choices to fill such needs. Earlier works have established the phenomenon of resonant x-ray Raman scattering with excitation energy very close to the Si-K absorption edge (1.74 keV). In this work, similar phenomena are identified in W-silicide and GaAs substrate with the excitation of W-Lβ 9.67 keV) line, a choice of x-ray source for almost all the conventional TXRF systems nowadays. The observation of the resonant Raman peak is clearly the result of close proximity of W-L and As-K absorption edges to the excitation energy. Synchrotron TXRF measurements are performed by tuning the excitation energy. The resonant Raman peak shifts accordingly with the excitation energy, along with the drastic change of its intensity below and above the absorption edge of W-L or As-K in the respective samples. The current analysis provides new perspective for analyzing W- and As-containing samples, which suggests Raman background correction in conventional TXRF with W-Lβ excitation. (author)

Resonance Raman and excitation energy dependent charge transfer mechanism in halide-substituted hybrid perovskite solar cells.

Science.gov (United States)

Park, Byung-wook; Jain, Sagar M; Zhang, Xiaoliang; Hagfeldt, Anders; Boschloo, Gerrit; Edvinsson, Tomas

2015-02-24

Organo-metal halide perovskites (OMHPs) are materials with attractive properties for optoelectronics. They made a recent introduction in the photovoltaics world by methylammonium (MA) lead triiodide and show remarkably improved charge separation capabilities when chloride and bromide are added. Here we show how halide substitution in OMHPs with the nominal composition CH3NH3PbI2X, where X is I, Br, or Cl, influences the morphology, charge quantum yield, and local interaction with the organic MA cation. X-ray diffraction and photoluminescence data demonstrate that halide substitution affects the local structure in the OMHPs with separate MAPbI3 and MAPbCl3 phases. Raman spectroscopies as well as theoretical vibration calculations reveal that this at the same time delocalizes the charge to the MA cation, which can liberate the vibrational movement of the MA cation, leading to a more adaptive organic phase. The resonance Raman effect together with quantum chemical calculations is utilized to analyze the change in charge transfer mechanism upon electronic excitation and gives important clues for the mechanism of the much improved photovoltage and photocurrent also seen in the solar cell performance for the materials when chloride compounds are included in the preparation.

Resonant Raman scattering in Nd2O3 and the electronic structure of Sr2RuO4 studied by synchrotron radiation excitation

International Nuclear Information System (INIS)

Ederer, D. L.

1998-01-01

This paper is intended to illustrate two points. The first being the extensive growth of resonant Raman soft x-ray scattering due to the emergence of third-generation x-ray sources. With these sources, the ubiquitous presence of Raman scattering near the 3d and 4d ionization thresholds has been used to elucidate the excitation process in a number of rare earth and transition metal compounds. Such scattering can produce dramatic changes in the emission spectrum, as we show in our example of inelastic scattering at the 3d threshold of Nd 2 O 3 . Photon-in photon-out soft x-ray spectroscopy is adding a new dimension to soft x-ray spectroscopy by providing many opportunities for exciting research, especially at third-generation synchrotrons light sources. Second, it is very effective to use theory and experiment to characterize the electronic properties of materials. In particular we confirmed in-plane oxygen-ruthenium bonding in Sr 2 RuO 4 , this first copperless perovskite superconductor, by analyses using calculations, soft x-ray emission spectroscopy (SXE) and photoelectron spectroscopy (PES). Measurements of this type illustrate the importance of combining SXE and PES measurements with theoretical calculations

Blood analysis by Raman spectroscopy.

Science.gov (United States)

Enejder, Annika M K; Koo, Tae-Woong; Oh, Jeankun; Hunter, Martin; Sasic, Slobodan; Feld, Michael S; Horowitz, Gary L

2002-11-15

Concentrations of multiple analytes were simultaneously measured in whole blood with clinical accuracy, without sample processing, using near-infrared Raman spectroscopy. Spectra were acquired with an instrument employing nonimaging optics, designed using Monte Carlo simulations of the influence of light-scattering-absorbing blood cells on the excitation and emission of Raman light in turbid medium. Raman spectra were collected from whole blood drawn from 31 individuals. Quantitative predictions of glucose, urea, total protein, albumin, triglycerides, hematocrit, and hemoglobin were made by means of partial least-squares (PLS) analysis with clinically relevant precision (r(2) values >0.93). The similarity of the features of the PLS calibration spectra to those of the respective analyte spectra illustrates that the predictions are based on molecular information carried by the Raman light. This demonstrates the feasibility of using Raman spectroscopy for quantitative measurements of biomolecular contents in highly light-scattering and absorbing media.

Use of the product of mean intensity ratio (PMIR) technique for discriminant analysis of lycopene-rich vegetable juice using a portable NIR-excited Raman spectrometer.

Science.gov (United States)

Hara, Risa; Ishigaki, Mika; Kitahama, Yasutaka; Ozaki, Yukihiro; Genkawa, Takuma

2018-02-15

In this study, a lycopene-content-based discriminant analysis was performed using a portable near-infrared-excited Raman spectrometer. In the vegetable-juice Raman spectra, the peak intensity of the lycopene band increased with increasing lycopene concentration, but scattering decreased the repeatability of the peak intensity. Consequently, developing a lycopene-concentration regression model using peak intensity is not straightforward. Therefore, a new method known as the product of mean intensity ratio (PMIR) analysis was developed to rapidly identify lycopene-rich samples on-site. In the PMIR analysis, Raman spectra are measured with short exposure times, confirming only the peaks of carotenoids with high concentrations, and thus the lycopene concentrations of vegetable juice samples could be determined successfully. Exposure times of 20ms and 100ms could detect lycopene concentrations of ≥5mg/100g and ≥2mg/100g with 93.2% and 97.7% accuracy, respectively; thus, lycopene-content-based discriminant analysis using the PMIR and a portable Raman spectrometer is feasible. Copyright © 2017 Elsevier Ltd. All rights reserved.

Fast Resonance Raman Spectroscopy of Short-Lived Radicals

DEFF Research Database (Denmark)

Pagsberg, Palle Bjørn; Wilbrandt, Robert Walter; Hansen, Karina Benthin

1976-01-01

We report the first application of pulsed resonance Raman spectroscopy to the study of short-lived free radicals produced by pulse radiolysis. A single pulse from a flash-lamp pumped tunable dye laser is used to excite the resonance Raman spectrum of the p-terphenyl anion radical with an initial...

Raman spectroscopy of white wines.

Science.gov (United States)

Martin, Coralie; Bruneel, Jean-Luc; Guyon, François; Médina, Bernard; Jourdes, Michael; Teissedre, Pierre-Louis; Guillaume, François

2015-08-15

The feasibility of exploiting Raman scattering to analyze white wines has been investigated using 3 different wavelengths of the incoming laser radiation in the near-UV (325 nm), visible (532 nm) and near infrared (785 nm). To help in the interpretation of the Raman spectra, the absorption properties in the UV-visible range of two wine samples as well as their laser induced fluorescence have also been investigated. Thanks to the strong intensity enhancement of the Raman scattered light due to electronic resonance with 325 nm laser excitation, hydroxycinnamic acids may be detected and analyzed selectively. Fructose and glucose may also be easily detected below ca. 1000 cm(-1). This feasibility study demonstrates the potential of the Raman spectroscopic technique for the analysis of white wines. Copyright © 2015 Elsevier Ltd. All rights reserved.

Scanning Raman lidar for tropospheric water vapor profiling and GPS path delay correction

Science.gov (United States)

Tarniewicz, Jerome; Bock, Olivier; Pelon, Jacques R.; Thom, Christian

2002-01-01

The design of a ground based and transportable combined Raman elastic-backscatter lidar for the remote sensing of lower tropospheric water vapor and nitrogen concentration is described. This lidar is intended to be used for an external calibration of the wet path delay of GPS signals. A description of the method used to derive water vapor and nitrogen profiles in the lower troposphere is given. The instrument has been tested during the ESCOMPTE campaign in June 2001 and first measurements are presented.

Calculation of the Raman intensity in graphene and carbon nanotubes

Science.gov (United States)

Moutinho, Marcus; Venezuela, Pedro

2014-03-01

Raman spectroscopy is one of the most important experimental techniques for characterization of carbon materials because it can give a lot of information about electronic and phonon structure in a non destructive way. We use a third-order quantum field model to obtain the theoretical Raman intensity for graphene and carbon nanotubes (CNT). The most important Raman peaks in graphitic materials comes from to the iLo and iTo phonon branches near to Γ and K points and, in this work, we focus our attention on some of these peaks, like the G, D and 2D bands, as a function of laser energy. The electronic and phonon dispersion used in our calculations reproduces the graphene ab initio results with GW corrections and the zone folding method is used to obtain the CNT ones. Our results show that the experimental G band Raman excitation profile for CNT can be reproduced if we use the proper electronic and phonon dispersions. We also show that the phonon dispersion may influence the shape of the graphene D band and the dispersive behavior of the 2D band for graphene and CNT. This work was supported by the Brazilian Nanocarbon Institute of Science and Technology (INCT/Nanocarbono), the Brazilian Network on Carbon Nanotube Research and the Brazilian agency CAPES

Triplet State Resonance Raman Spectrum of all-trans-diphenylbutadiene

DEFF Research Database (Denmark)

Wilbrandt, Robert Walter; Grossman, W.E.L.; Killough, P.M

1984-01-01

The resonance Raman spectrum of all-trans-diphenylbutadiene (DPB) in its ground state and the resonance Raman spectrum (RRS) of DPB in its short-lived electronically excited triplet state are reported. Transient spectra were obtained by a pump-probe technique using two pulsed lasers...

Raman spectra of filled carbon nanotubes

International Nuclear Information System (INIS)

Bose, S.M.; Behera, S.N.; Sarangi, S.N.; Entel, P.

2004-01-01

The Raman spectra of a metallic carbon nanotube filled with atoms or molecules have been investigated theoretically. It is found that there will be a three way splitting of the main Raman lines due to the interaction of the nanotube phonon with the collective excitations (plasmons) of the conduction electrons of the nanotube as well as its coupling with the phonon of the filling material. The positions and relative strengths of these Raman peaks depend on the strength of the electron-phonon interaction, phonon frequency of the filling atom and the strength of interaction of the nanotube phonon and the phonon of the filling atoms. Careful experimental studies of the Raman spectra of filled nanotubes should show these three peaks. It is also shown that in a semiconducting nanotube the Raman line will split into two and should be observed experimentally

Micro-Raman scattering in ZnTe thin films

International Nuclear Information System (INIS)

Larramendi, E. M.; Gutierrez Z-B, K.; Hernandez, E.; Melo, O. de; Berth, G.; Wiedemeier, V.; Lischka, K; Schikora, D.; Woggon, U.

2008-01-01

In this work we present micro-raman measurements on ZnTe thin films grown by isothermal closed space sublimation on GaAs(001) substrates in helium and nitrogen atmospheres. Micro-raman spectra were recorded at room temperature using the backscattering geometry (illuminated spot: 3 μm2, 0.3 cm-1 of resolution and the line 532 nm of a DPSSL as power excitation). Up to four order LO-phonon replicas and no peak from TO phonon were observed in the micro-raman spectra as evidence of the epitaxial character and good quality of the films (the TO mode is forbidden according to the selection rules for backscattering along [001] of this heterostructure). The micro-raman spectra also revealed two features at low energy, which have been assigned incorrectly in recent works. We demonstrate that these raman peaks can be associated to the presence of few monolayers of crystalline tellurium or its oxides on the surface of the films. These features were not observed in micro-raman spectra of as grown ZnTe films terminated in a Zn surface. However, they were detected after a prolonged exposure of the samples to air. In addition, it is shown that this effect is accelerated under a high power laser excitation (laser annealing) as used in conventional micro-Raman measurement setups. Preliminary results that suggest the inclusion of nitrogen in ZnTe structure are also shown. (Full text)

Femtosecond pulse laser notch shaping via fiber Bragg grating for the excitation source on the coherent anti-Stokes Raman spectroscopy

Science.gov (United States)

Oh, Seung Ryeol; Kwon, Won Sik; Kim, Jin Hwan; Kim, Kyung-Soo; Kim, Soohyun

2015-03-01

Single-pulse coherently controlled nonlinear Raman spectroscopy is the simplest method among the coherent anti-Stokes Raman spectroscopy systems. In recent research, it has been proven that notch-shaped femtosecond pulse laser can be used to collect the coherent anti-Stokes Raman signals. In this study, we applied a fiber Bragg grating to the notch filtering component on the femtosecond pulse lasers. The experiment was performed incorporating a titanium sapphire femtosecond pulse laser source with a 100 mm length of 780-HP fiber which is inscribed 30 mm of Bragg grating. The fiber Bragg grating has 785 nm Bragg wavelength with 0.9 nm bandwidth. We proved that if the pulse lasers have above a certain level of positive group delay dispersion, it is sufficient to propagate in the fiber Bragg grating without any spectral distortion. After passing through the fiber Bragg grating, the pulse laser is reflected on the chirped mirror for 40 times to make the transform-limited pulse. Finally, the pulse time duration was 37 fs, average power was 50mW, and showed an adequate notch shape. Furthermore, the simulation of third order polarization signal is performed using MATLAB tools and the simulation result shows that spectral characteristic and time duration of the pulse is sufficient to use as an excitation source for single-pulse coherent anti-Stokes Raman spectroscopy. In conclusion, the proposed method is more simple and cost-effective than the methods of previous research which use grating pairs and resonant photonic crystal slab.

Para-hydrogen raman laser and its application to laser induced chemistry

International Nuclear Information System (INIS)

Tashiro, Hideo

1988-01-01

The report outlines the mechanism of the para-hydrogen Raman laser as a infrared light source, and its application to laser induced chemistry. The Stoke's wave number after a Raman shift is equal to the difference between the wave number of the CO 2 laser used for excitation and the rotation Raman wave number of the hydrogen molecule. A Raman laser can serve as an infrared source. CO 2 laser oscillation beam in the range of 9∼11 micrometers is selected and the frequency of infrared beam is varied by changing the wave number of the CO 2 laser beam. A problem with the Raman laser is that the Raman scatterring gain is small due to a large wavelength. In developing equipment, a special mechanism is required to solve this problem. A Raman laser comprises a CO 2 laser for excitation and multi-pulse Raman cells. The combination of a TEA oscillator and amplifiers gives CO 2 pulses with a peak power of about several tens of MW. Many heavy metal compounds including fluorides, carbonyl compounds and other organic compounds, absorb light with wavelengths in the same range as those of the Raman laser. Such compounds can be dissociated directly by applying Raman laser beams. The laser will be helpful for separation of isotopes, etc. (Nogami, K.)

All-solid-state, synchronously pumped, ultrafast BaWO4 Raman laser with long and short Raman shifts generating at 1180, 1225, and 1323 nm

Science.gov (United States)

Frank, Milan; Jelínek, Michal; Kubeček, Václav; Ivleva, Lyudmila I.; Zverev, Petr G.; Smetanin, Sergei

2017-12-01

A lot of attention is currently focused on synchronously pumped, extra-cavity crystalline Raman lasers generating one or two Stokes Raman components in KGW or diamond Raman-active crystals, and also generating additional components of stimulated polariton scattering in lithium niobate crystal having both cubic and quadratic nonlinearities. In this contribution we report on generation of more than two Stokes components of stimulated Raman scattering with different Raman shifts in the all-solid-state, synchronously pumped, extra-cavity Raman laser based on the Raman-active a-cut BaWO4 crystal excited by a mode-locked, 220 nJ, 36 ps, 150 MHz diode sidepumped Nd:GdVO4 laser generating at the wavelength of 1063 nm. Excitation by the pumping radiation polarized along the BaWO4 crystal optical axis resulted in the Raman generation with not only usual (925cm - 1), but also additional (332cm - 1) Raman shift. Besides the 1180-nm first and 1323 nm second Stokes components with the Raman shift of 925cm - 1 from the 1063nm fundamental laser wavelength, we have achieved generation of the additional 1227 nm Raman component with different Raman shift of 332cm - 1 from the 1180nm component. At the 1227 nm component the strongest 12-times pulse shortening from 36ps down to 3ps was obtained due to shorter dephasing time of this additional Raman line (3ps for the 332-cm - 1 line instead of 6.5ps for the 925cm - 1 line). It has to be also noted that the 1225 nm generation is intracavity pumped by the 1179 nm first Stokes component resulting in the strongest pulse shortening close to the 332cm -1 line dephasing time (3ps). Slope efficiency of three Stokes components generation exceeded 20%.

Raman spectroscopy in graphene

International Nuclear Information System (INIS)

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

2009-01-01

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.

Abnormal anti-Stokes Raman emission as a coherent anti-Stokes Raman scattering-like process in disordered media

International Nuclear Information System (INIS)

Baltog, Ioan; Baibarac, Mihaela; Smaranda, Ion; Lefrant, Serge

2011-01-01

In this paper, we demonstrate that, by continuous single beam excitation, one can generate an abnormal anti-Stokes Raman emission (AASRE) whose properties are similar to a coherent anti-Stokes Raman scattering (CARS). The effect has been observed in materials which possess intrinsically nonlinear properties (LiNbO 3 and CdS), which have the electric susceptibility of third order different from zero, χ (3) ≠ 0, as well as in materials that become nonlinear under resonant optical excitation. In the latter case, we used poly-3,4-ethylendioxythiophene (PEDOT) in its undoped state deposited electrochemically on Au support. Raman studies corroborated with images of optical microscopy demonstrate that the production of AASRE is conditioned by the existence of a particular morphology of the sample able to ensure efficient transport of the light inside the sample through a multiple light scattering mechanism. In this context, it was found that LiNbO 3 and CdS in powder form as well as the PEDOT films layered on a rough Au substrate are suitable morphological forms. We explain AASRE as resulting from a wave-mixing mechanism of the incident laser light ω l with a Stokes-shifted Raman light ω S produced by a spontaneous Raman light scattering process, both strongly scattered inside the sample. As a CARS process, AASRE is conditioned by the achievement of phase-matching requirements, which makes the difference between the wave vectors of mixing light close to zero, Δk =/2k l - k S - k CARS /∼ 0. In condensed media, the small dispersion of the refractive index makes Δk ∼ 0 so that the formation of a favourable phase-matching geometry may be accomplished even at a crossing angle θ of travelling scattered light ω l and ω S . For tightly focused beams, the requirement of phase matching relaxes; it is no longer sensitive to the Raman shift, so that a wide intense anti-Stokes Raman spectrum is observed at an angle larger than the Stokes Raman spectrum.

Raman overtone intensities measured for H2

International Nuclear Information System (INIS)

Shelton, D.P.

1990-01-01

The Raman spectra of the vibrational fundamental, first overtone and second overtone transitions of the H 2 molecule were recorded using visible and ultraviolet argon--ion laser excitation. The ratios of transition polarizability matrix elements, α 01,21 /α 01,11 and α 01,31 /α 01,11 , were determined from the measured intensities of the Q(1) Raman lines v,J=0,1→v',1 for v'=1,2,3. The experimentally determined value of the Raman first overtone matrix element is in good agreement with the value from the best ab initio calculation

In Situ Raman Analysis of CO₂-Assisted Drying of Fruit-Slices.

Science.gov (United States)

Braeuer, Andreas Siegfried; Schuster, Julian Jonathan; Gebrekidan, Medhanie Tesfay; Bahr, Leo; Michelino, Filippo; Zambon, Alessandro; Spilimbergo, Sara

2017-05-15

This work explores the feasibility of applying in situ Raman spectroscopy for the online monitoring of the supercritical carbon dioxide (SC-CO₂) drying of fruits. Specifically, we investigate two types of fruits: mango and persimmon. The drying experiments were carried out inside an optical accessible vessel at 10 MPa and 313 K. The Raman spectra reveal: (i) the reduction of the water from the fruit slice and (ii) the change of the fruit matrix structure during the drying process. Two different Raman excitation wavelengths were compared: 532 nm and 785 nm. With respect to the quality of the obtained spectra, the 532 nm excitation wavelength was superior due to a higher signal-to-noise ratio and due to a resonant excitation scheme of the carotenoid molecules. It was found that the absorption of CO₂ into the fruit matrix enhances the extraction of water, which was expressed by the obtained drying kinetic curve.

The Raman and SERS spectra of indigo and indigo-Ag2 complex: DFT calculation and comparison with experiment.

Science.gov (United States)

Ricci, Marilena; Lofrumento, Cristiana; Becucci, Maurizio; Castellucci, Emilio M

2018-01-05

Using time-dependent density functional theory in conjunction with B3LYP functional and LANL2DZ/6-31+g(d,p) basis sets, static and pre-resonance Raman spectra of the indigo-Ag 2 complex have been calculated. Structure optimization, excitation energies and pre-resonance Raman spectra of the indigo molecule have been obtained at the same level of theory. The available experimental Raman spectra at 1064, 785 and 514nm and the SERS spectra at 785 and 514nm have been well reproduced by the calculation. Experimental SERS spectra are confronted with the calculated pre-resonance Raman spectra obtained for the indigo-Ag 2 complex. The Raman activities calculated under the infinite lifetime approximation show a strong dependence upon the proximity to the energy and the oscillator strength of the excitation electronic transition. The comparison of the integrated EFs for indigo and indigo-Ag 2 calculated Raman spectra, gave some hints as to the enhancement mechanisms acting for the different excitation wavelengths. Whereas for excitation at a wavelength corresponding to 785nm, the enhancement mechanism for the Raman spectrum of the metal complex seems the chemical one, the strong increment (ten times) of the integrated EF of the Raman spectra of the complex in the case of 514nm excitation, suggests the onset of other enhancement mechanisms. Assuming that intra-cluster transitions with high oscillator strength can be thought of as to mimic surface plasmons excitations, we suggest the onset of the electromagnetic mechanisms (EM) as the origin of the Raman spectrum enhancement. Nevertheless, other enhancement effects cannot be ruled out, as a new molecular transition gains strength in the proximity of the excitation wavelength, as a consequence of the symmetry lowering of the molecule in the complex. A large variation across vibrational modes, by a factor of at least 10 4 , was found for the EFs. This large variation in the EFs can indicate that B-term Herzberg-Teller scattering

Near IR Scanning Angle Total Internal Reflection Raman Spectroscopy at Smooth Gold Films

Energy Technology Data Exchange (ETDEWEB)

McKee, Kristopher; Meyer, Matthew; Smith, Emily

2012-04-13

Total internal reflection (TIR) Raman and reflectivity spectra were collected for nonresonant analytes as a function of incident angle at sapphire or sapphire/smooth 50 nm gold interfaces using 785 nm excitation. For both interfaces, the Raman signal as a function of incident angle is well-modeled by the calculated interfacial mean square electric field (MSEF) relative to the incident field times the thickness of the layer being probed in the Raman measurement (D{sub RS}). The Raman scatter was reproducibly enhanced at the interface containing a gold film relative to the sapphire interface by a factor of 4.3–4.6 for aqueous pyridine or 2.2–3.7 for neat nitrobenzene, depending on the analyzed vibrational mode. The mechanism for the increased Raman signal is the enhanced MSEF at incident angles where propagating surface plasmons are excited in the metal film. The background from the TIR prism was reduced by 89–95% with the addition of the gold film, and the percent relative uncertainty in peak area was reduced from 15 to 1.7% for the 1347 cm–1 mode of nitrobenzene. Single monolayers of benzenethiol (S/N = 6.8) and 4-mercaptopyridine (S/N = 16.5) on gold films were measured by TIR Raman spectroscopy with 785 nm excitation (210 mW) without resonant enhancement in 1 min.

Raman scattering of rare earth hexaborides

International Nuclear Information System (INIS)

Ogita, Norio; Hasegawa, Takumi; Udagawa, Masayuki; Iga, Fumitoshi; Kunii, Satoru

2009-01-01

Raman scattering spectra were measured for the rare-earth hexaborides RB 6 (R = Ce, Gd, or Dy). All Raman-active phonons due to B 6 vibrations were observed in the range 600 - 1400 cm -1 . Anomalous peaks were detected below 200 cm -1 , which correspond to vibrations of rare-earth ion excited by second-order Raman scattering process. The intensity and energy of the rare-earth mode decrease with decreasing temperature. This suggests that the rare-earth ion vibrates in a shallow and anharmonic potential due to the boron cage. Using the reported values of mean square displacement of rare-earth ion, we estimated the anharmonic contribution for the rare-earth vibrations.

Holographic Raman lidar

International Nuclear Information System (INIS)

Andersen, G.

2000-01-01

Full text: We have constructed a Raman lidar system that incorporates a holographic optical element. By resolving just 3 nitrogen lines in the Resonance Raman spectroscopy (RRS) spectrum, temperature fits as good as 1% at altitudes of 20km can be made in 30 minutes. Due to the narrowband selectivity of the HOE, the lidar provides measurements over a continuous 24hr period. By adding a 4th channel to capture the Rayleigh backscattered light, temperature profiles can be extended to 80km

Detection and characterization of stomach cancer and atrophic gastritis with fluorescence and Raman spectroscopy

Science.gov (United States)

Li, Xiaozhou; Lin, Junxiu; Jia, Chunde; Wang, Rong

2003-12-01

In this paper, we attempt to find a valid method to distinguish gastric cancer and atrophic gastritis. Auto-fluorescence and Raman spectroscopy of laser induced (514.5 nm and 488.0 nm) was measured. The serum spectrum is different between normal and cancer. Average value of diagnosis parameter for normal serum, red shift is less than 12 nm and Raman relative intensity of peak C by 514.5 nm excited is stronger than that of 488.0 nm. To gastric cancer, its red shift of average is bigger than 12 nm and relative intensity of Raman peak C by 514.5 nm excited is weaker than that by 488.0 nm. To atrophic gastritis, the distribution state of Raman peaks is similar with normal serum and auto-fluorescence spectrum's shape is similar to that of gastric cancer. Its average Raman peak red shift is bigger than 12 nm and the relative intensity of peak C by 514.5 excited is stronger than that of by 488.0. We considered it as a criterion and got an accuracy of 85.6% for diagnosis of gastric cancer compared with the result of clinical diagnosis.

Resonance Raman and surface-enhanced resonance Raman spectra of LH2 antenna complex from Rhodobacter sphaeroides and Ectothiorhodospira sp. excited in the Qx and Qy transitions.

Science.gov (United States)

Chumanov, G; Picorel, R; Ortiz de Zarate, I; Cotton, T M; Seibert, M

2000-05-01

Well-resolved vibrational spectra of LH2 complex isolated from two photosynthetic bacteria, Rhodobacter sphaeroides and Ectothiorhodospira sp., were obtained using surface-enhanced resonance Raman scattering (SERRS) exciting into the Qx and the Qy transitions of bacteriochlorophyll a. High-quality SERRS spectra in the Qy region were accessible because the strong fluorescence background was quenched near the roughened Ag surface. A comparison of the spectra obtained with 590 nm and 752 nm excitation in the mid- and low-frequency regions revealed spectral differences between the two LH2 complexes as well as between the LH2 complexes and isolated bacteriochlorophyll a. Because peripheral modes of pigments contribute mainly to the low-frequency spectral region, frequencies and intensities of many vibrational bands in this region are affected by interactions with the protein. The results demonstrate that the microenvironment surrounding the pigments within the two LH2 complexes is somewhat different, despite the fact that the complexes exhibit similar electronic absorption spectra. These differences are most probably due to specific pigment-pigment and pigment-protein interactions within the LH2 complexes, and the approach might be useful for addressing subtle static and dynamic structural variances between pigment-protein complexes from different sources or in complexes altered chemically or genetically.

A combined remote Raman and LIBS instrument for characterizing minerals with 532 nm laser excitation.

Science.gov (United States)

Sharma, Shiv K; Misra, Anupam K; Lucey, Paul G; Lentz, Rachel C F

2009-08-01

The authors have developed an integrated remote Raman and laser-induced breakdown spectroscopy (LIBS) system for measuring both the Raman and LIBS spectra of minerals with a single 532 nm laser line of 35 mJ/pulse and 20 Hz. The instrument has been used for analyzing both Raman and LIBS spectra of carbonates, sulfates, hydrous and anhydrous silicates, and iron oxide minerals in air. These experiments demonstrate that by focusing a frequency-doubled 532 nm Nd:YAG pulsed laser beam with a 10x beam expander to a 529-microm diameter spot on a mineral surface located at 9 m, it is possible to measure simultaneously both the remote Raman and LIBS spectra of calcite, gypsum and olivine by adjusting the laser power electronically. The spectra of calcite, gypsum, and olivine contain fingerprint Raman lines; however, it was not possible to measure the remote Raman spectra of magnetite and hematite at 9 m because of strong absorption of 532 nm laser radiation and low intensities of Raman lines from these minerals. The remote LIBS spectra of both magnetite and hematite contain common iron emission lines but show difference in the minor amount of Li present in these two minerals. Remote Raman and LIBS spectra of a number of carbonates, sulfates, feldspars and phyllosilicates at a distance of 9 m were measured with a 532-nm laser operating at 35 mJ/pulse and by changing photon flux density at the sample by varying the spot diameter from 10 mm for Raman to 530 microm for LIBS measurements. The complementary nature of these spectra is highlighted and discussed. The combined Raman and LIBS system can also be re-configured to perform micro-Raman and micro-LIBS analyses, which have applications in trace/residue analysis and analysis of very small samples in the nano-gram range.

Raman scattering tensors of tyrosine.

Science.gov (United States)

Tsuboi, M; Ezaki, Y; Aida, M; Suzuki, M; Yimit, A; Ushizawa, K; Ueda, T

1998-01-01

Polarized Raman scattering measurements have been made of a single crystal of L-tyrosine by the use of a Raman microscope with the 488.0-nm exciting beam from an argon ion laser. The L-tyrosine crystal belongs to the space group P2(1)2(1)2(1) (orthorhombic), and Raman scattering intensities corresponding to the aa, bb, cc, ab and ac components of the crystal Raman tensor have been determined for each prominent Raman band. A similar set of measurements has been made of L-tyrosine-d4, in which four hydrogen atoms on the benzene ring are replaced by deuterium atoms. The effects of NH3-->ND3 and OH-->OD on the Raman spectrum have also been examined. In addition, depolarization ratios of some bands of L-tyrosine in aqueous solutions of pH 13 and pH 1 were examined. For comparison with these experimental results, on the other hand, ab initio molecular orbital calculations have been made of the normal modes of vibration and their associated polarizability oscillations of the L-tyrosine molecule. On the basis of these experimental data and by referring to the results of the calculations, discussions have been presented on the Raman tensors associated to some Raman bands, including those at 829 cm-1 (benzene ring breathing), 642 cm-1 (benzene ring deformation), and 432 cm-1 (C alpha-C beta-C gamma bending).

Raman laser spectrometer optical head: qualification model assembly and integration verification

Science.gov (United States)

Ramos, G.; Sanz-Palomino, M.; Moral, A. G.; Canora, C. P.; Belenguer, T.; Canchal, R.; Prieto, J. A. R.; Santiago, A.; Gordillo, C.; Escribano, D.; Lopez-Reyes, G.; Rull, F.

2017-08-01

Raman Laser Spectrometer (RLS) is the Pasteur Payload instrument of the ExoMars mission, within the ESA's Aurora Exploration Programme, that will perform for the first time in an out planetary mission Raman spectroscopy. RLS is composed by SPU (Spectrometer Unit), iOH (Internal Optical Head), and ICEU (Instrument Control and Excitation Unit). iOH focuses the excitation laser on the samples (excitation path), and collects the Raman emission from the sample (collection path, composed on collimation system and filtering system). Its original design presented a high laser trace reaching to the detector, and although a certain level of laser trace was required for calibration purposes, the high level degrades the Signal to Noise Ratio confounding some Raman peaks. So, after the bread board campaign, some light design modifications were implemented in order to fix the desired amount of laser trace, and after the fabrication and the commitment of the commercial elements, the assembly and integration verification process was carried out. A brief description of the iOH design update for the engineering and qualification model (iOH EQM) as well as the assembly process are briefly described in this papers. In addition, the integration verification and the first functional tests, carried out with the RLS calibration target (CT), results are reported on.

Alcohol-catalyzed photoreduction of iron-porphyrin complexes revealed by resonance raman and absorption spectroscopies

Science.gov (United States)

Ogura, T.; Fidler, V.; Ozaki, Y.; Kitagawa, T.

1990-06-01

Photoreduction of Fe III(OEP) (2-MeIm) (OEP is octaethylporphyrin; 2-MeIm is 2-methylimidazole) was found to be catalyzed by a trace amount of MeOH present in Ch 2Cl 2 as a stabilizer. The absence of either 2-MeIm or MeOH in the CH 2Cl 2 solution of Fe III(OEP) X (X is Cl -, Br - or I -) leads to no photoreduction. The presence of MeOH in the Fe III(OEP) (2-MeIm) solution results in the appearance of a new absorption band at 585 nm, and when Raman scattering was excited at 590 nm, a new Raman band appeared at 524 cm -. This band exhibited an upshift by 4 cm - with 54Fe(OEP) (2-MeIm)(CH 3OH) and a downshift by 12 cm -1 with 56Fe(OEP)(2-MeIm) (CD 3OD) and was therefore assigned to the Fe III-MeOH stretching vibration. The excitation profile of this band gave a peak around 585 nm and accordingly, the new absorption band at 584 nm was assigned to a charge-transfer (CT) band from MeOH to the Fe III ion. It was most unexpected that the photoreduction did not occur upon laser illumination within the CT band.

Raman spectroscopic analysis of real samples: Brazilian bauxite mineralogy

Science.gov (United States)

Faulstich, Fabiano Richard Leite; Castro, Harlem V.; de Oliveira, Luiz Fernando Cappa; Neumann, Reiner

2011-10-01

In this investigation, Raman spectroscopy with 1064 and 632.8 nm excitation was used to investigate real mineral samples of bauxite ore from mines of Northern Brazil, together with Raman mapping and X-rays diffraction. The obtained results show clearly that the use of microRaman spectroscopy is a powerful tool for the identification of all the minerals usually found in bauxites: gibbsite, kaolinite, goethite, hematite, anatase and quartz. Bulk samples can also be analysed, and FT-Raman is more adequate due to better signal-to-noise ratio and representativity, although not efficient for kaolinite. The identification of fingerprinting vibrations for all the minerals allows the acquisition of Raman-based chemical maps, potentially powerful tools for process mineralogy applied to bauxite ores.

Atomic substitution in selected high-temperature superconductors: Elucidating the nature of Raman spectra excitations

Science.gov (United States)

Hewitt, Kevin Cecil

2000-10-01

In this thesis, the effects of atomic substitution on the vibrational and electronic excitations found in the Raman spectra of selected high-temperature superconductors (HTS) are studied. In particular, atomic and isotopic substitution methods have been used to determine the character of features observed in the Raman spectra of Bi2Sr2Ca n-1CunO2 n+4+delta (n = 1 - Bi2201, n = 2 - Bi2212) and YBa2Cu3O7-delta (Y123). In Bi2201, Pb substitution for Bi (and Sr) has led to the reduction and eventual removal of the structural modulation, characteristic of all members of the Bi-family of HTS. The high quality single crystals and our sensitive triple spectrometer enabled identification of a pair of low frequency modes. The modes are determined to arise from shear and compressional rigid-layer vibrations. The normal state of underdoped cuprates is characterized by a pseudogap of unknown origin. In crystals of underdoped Bi2212 a spectral peak found at 590 cm-1, previously attributed to the pairing of quasiparticles (above Tc) and hence to the formation of a normal state pseudogap, has been found to soften by 3.8% with oxygen isotope exchange. In addition, the feature is absent in fully oxygenated and yttrium underdoped crystals. In this study, the first of its kind on underdoped and isotope substituted Bi2212, the feature has been assigned to stretching vibrations of oxygen in the a-b plane. Bi2212 crystals with varying hole concentrations (0.07 Raman scattering experiments that sample the diagonal (B 2g) and principal axes (B1 g) of the BZ have led us to conclude that the superconducting gap possesses dx2-y2 symmetry, in the underdoped and overdoped regimes. It is found that the magnitude of the superconducting gap (Delta(k)) is sensitive to changes in p. Studies of the pair-breaking peak found in the B1g spectra allow us to conclude that the magnitude of the maximum gap (Deltamax) decreases monotonically with increasing hole doping, for p > 0.13. The pair

Feasibility study of Raman spectroscopy for investigating the mouse retina in vivo

Science.gov (United States)

Manna, Suman K.; de Oliveira, Marcos A. S.; Zhang, Pengfei; Maleppat, Ratheesh K.; Chang, Che-Wei; Pugh, Edward N.; Chan, James W.; Zawadzki, Robert J.

2018-02-01

The use of Raman spectroscopy in biochemistry has been very successful, particularly because of its ability to identify elementary chemical species. However, application of this spectroscopic technique for in vivo assessment is often limited by autofluorescence, which make detection of Raman signatures difficult. The mouse eye has been used as an optical testbed for investigation of a variety of disease models and therapeutic pathways. Implementation of in vivo Raman spectroscopy in mice retina would be valuable but needs to be examined in context of the intrinsic auto-fluorescence artifact and potential light damage if high probing beam powers were used. To evaluate feasibility, a Raman system was built on a custom SLO/OCT platform allowing mouse positioning and morphological data acquisition along with the Raman signal from a desired retinal eccentricity. The performance of the Raman system was first assessed with a model eye consisting of polystyrene in the image plane (retina), using excitation wavelengths of 488 nm, 561 nm, and 785 nm to determine whether auto-fluorescence would be reduced at longer wavelengths. To improve the SNR, the combined system is featured with the optical compatibility for these three excitations such that their corresponding spectra from a typical region of interest can be acquired consecutively during single imaging run. Our results include emission spectra acquired over 10 s with excitation energy less than 160 J.s-1.m-2 for all wavelengths and corresponding retinal morphology for different mouse strains including WT, BALB/c and ABCA4-/-.

Electron enhanced Raman scattering and its applications in solution chemistry

International Nuclear Information System (INIS)

Yui, Hiroharu

2007-01-01

The present review describes a new enhancement technique for Raman scattering in aqueous solutions. Raman scattering spectroscopy has an inherent ability to distinguish between molecules with great similarity and provides useful information on local physical and chemical environments at their functional groups' level. Since the Raman scattering signals from water molecules are quite weak, Raman spectroscopy has great advantage for detection or discrimination of a trace amount of analytes in aqueous environments. However, Raman scattering cross-sections are inherently small and it generally requires high power excitation and long acquisition times to obtain high-quality Raman spectra. These conditions create disadvantages for the analyses for living cells and real-time monitoring for environmental analyses. Here, I describe a new Raman enhancement technique, namely electron enhanced Raman scattering (EERS)', where artificially generated electrons additionally affect the polarizability of target molecular systems and enhance their inherent Raman cross-section. Principles of the EERS and its applications to aqueous solution are presented. (author)

Microscopic theoretical study of Raman spectra in charge and spin ordered cuprate systems

International Nuclear Information System (INIS)

Raj, B.K.; Panda, S.K.; Rout, G.C.

2013-01-01

Highlights: • The model calculation treats CDW interaction as pseudogap for cuprates. • The interplay of Raman active CDW-SDW mixed modes are investigated. • Independent CDW and SDW gap values can be determined from experimental data. -- Abstract: Raman scattering is one of the most powerful methods to investigate the electron as well as the phonon excitations in the systems. In this communication, we present a theoretical study of Raman scattering in the normal state of the high-T C systems in the under-doped region displaying the interplay of the spin-density-wave (SDW) and charge-density-wave (CDW) interactions. The SDW order arises from the repulsive Coulomb interaction of electrons, while the CDW order arises due to strong electron–phonon interaction giving rise to Fermi surface instability. We calculate phonon response function in order to examine the possibility of observing the SDW excitation mode in presence of the CDW interaction present in the same conduction band. The Raman scattering intensity is calculated from the imaginary part of the phonon Green’s function assigning an arbitrary spectral width. The spectral density function displays two mixed modes of excitation peaks at energies 2(Δ c ± Δ s ). The evolution of excitation peaks are investigated by varying CDW coupling, SDW coupling and the phonon momentum transfer energy

Microscopic theoretical study of Raman spectra in charge and spin ordered cuprate systems

Energy Technology Data Exchange (ETDEWEB)

Raj, B. K. [Dept. of Physics, Govt. Autonomous College, Angul, Orissa (India); Panda, S. K. [KD Science College, Pochilima, Hinjilicut, 761 101 Ganjam, Orissa (India); Rout, G.C., E-mail: gcr@iopb.res.in [Condensed Matter Physics Group, PG Dept. of Applied Physics and Ballistics, FM University, Balasore 756 019 (India)

2013-09-15

Highlights: • The model calculation treats CDW interaction as pseudogap for cuprates. • The interplay of Raman active CDW-SDW mixed modes are investigated. • Independent CDW and SDW gap values can be determined from experimental data. -- Abstract: Raman scattering is one of the most powerful methods to investigate the electron as well as the phonon excitations in the systems. In this communication, we present a theoretical study of Raman scattering in the normal state of the high-T{sub C} systems in the under-doped region displaying the interplay of the spin-density-wave (SDW) and charge-density-wave (CDW) interactions. The SDW order arises from the repulsive Coulomb interaction of electrons, while the CDW order arises due to strong electron–phonon interaction giving rise to Fermi surface instability. We calculate phonon response function in order to examine the possibility of observing the SDW excitation mode in presence of the CDW interaction present in the same conduction band. The Raman scattering intensity is calculated from the imaginary part of the phonon Green’s function assigning an arbitrary spectral width. The spectral density function displays two mixed modes of excitation peaks at energies 2(Δ{sub c} ± Δ{sub s}). The evolution of excitation peaks are investigated by varying CDW coupling, SDW coupling and the phonon momentum transfer energy.

Interference-free optical detection for Raman spectroscopy

Science.gov (United States)

Fischer, David G (Inventor); Kojima, Jun (Inventor); Nguyen, Quang-Viet (Inventor)

2012-01-01

An architecture for spontaneous Raman scattering (SRS) that utilizes a frame-transfer charge-coupled device (CCD) sensor operating in a subframe burst gating mode to realize time-resolved combustion diagnostics is disclosed. The technique permits all-electronic optical gating with microsecond shutter speeds (<5 .mu.s), without compromising optical throughput or image fidelity. When used in conjunction with a pair of orthogonally-polarized excitation lasers, the technique measures time-resolved vibrational Raman scattering that is minimally contaminated by problematic optical background noise.

Four-Wave Optical Parametric Amplification in a Raman-Active Gas

Directory of Open Access Journals (Sweden)

Yuichiro Kida

2015-08-01

Full Text Available Four-wave optical parametric amplification (FWOPA in a Raman-active medium is experimentally investigated by use of an air-filled hollow fiber. A femtosecond pump pulse shorter than the period of molecular motion excites the coherent molecular motion of the Raman-active molecules during the parametric amplification of a signal pulse. The excited coherent motion modulates the frequency of the signal pulse during the parametric amplification, and shifts it to lower frequencies. The magnitude of the frequency redshift depends on the pump intensity, resulting in intensity-dependent spectral characteristics that are different from those in the FWOPA induced in a noble-gas-filled hollow fiber.

Shot-Noise Limited Time-Encoded Raman Spectroscopy

Directory of Open Access Journals (Sweden)

Sebastian Karpf

2017-01-01

Full Text Available Raman scattering, an inelastic scattering mechanism, provides information about molecular excitation energies and can be used to identify chemical compounds. Albeit being a powerful analysis tool, especially for label-free biomedical imaging with molecular contrast, it suffers from inherently low signal levels. This practical limitation can be overcome by nonlinear enhancement techniques like stimulated Raman scattering (SRS. In SRS, an additional light source stimulates the Raman scattering process. This can lead to orders of magnitude increase in signal levels and hence faster acquisition in biomedical imaging. However, achieving a broad spectral coverage in SRS is technically challenging and the signal is no longer background-free, as either stimulated Raman gain (SRG or loss (SRL is measured, turning a sensitivity limit into a dynamic range limit. Thus, the signal has to be isolated from the laser background light, requiring elaborate methods for minimizing detection noise. Here, we analyze the detection sensitivity of a shot-noise limited broadband stimulated time-encoded Raman (TICO-Raman system in detail. In time-encoded Raman, a wavelength-swept Fourier domain mode locking (FDML laser covers a broad range of Raman transition energies while allowing a dual-balanced detection for lowering the detection noise to the fundamental shot-noise limit.

Raman microscopy of individual living human embryonic stem cells

Science.gov (United States)

Novikov, S. M.; Beermann, J.; Bozhevolnyi, S. I.; Harkness, L. M.; Kassem, M.

2010-04-01

We demonstrate the possibility of mapping the distribution of different biomolecules in living human embryonic stem cells grown on glass substrates, without the need for fluorescent markers. In our work we improve the quality of measurements by finding a buffer that gives low fluorescence, growing cells on glass substrates (whose Raman signals are relatively weak compared to that of the cells) and having the backside covered with gold to improve the image contrast under direct white light illumination. The experimental setup used for Raman microscopy is the commercially available confocal scanning Raman microscope (Alpha300R) from Witec and sub-μm spatially resolved Raman images were obtained using a 532 nm excitation wavelength.

In Situ Raman Analysis of CO2—Assisted Drying of Fruit-Slices

Directory of Open Access Journals (Sweden)

Andreas Siegfried Braeuer

2017-05-01

Full Text Available This work explores the feasibility of applying in situ Raman spectroscopy for the online monitoring of the supercritical carbon dioxide (SC-CO2 drying of fruits. Specifically, we investigate two types of fruits: mango and persimmon. The drying experiments were carried out inside an optical accessible vessel at 10 MPa and 313 K. The Raman spectra reveal: (i the reduction of the water from the fruit slice and (ii the change of the fruit matrix structure during the drying process. Two different Raman excitation wavelengths were compared: 532 nm and 785 nm. With respect to the quality of the obtained spectra, the 532 nm excitation wavelength was superior due to a higher signal-to-noise ratio and due to a resonant excitation scheme of the carotenoid molecules. It was found that the absorption of CO2 into the fruit matrix enhances the extraction of water, which was expressed by the obtained drying kinetic curve.

In Situ Raman Analysis of CO2—Assisted Drying of Fruit-Slices

Science.gov (United States)

Braeuer, Andreas Siegfried; Schuster, Julian Jonathan; Gebrekidan, Medhanie Tesfay; Bahr, Leo; Michelino, Filippo; Zambon, Alessandro; Spilimbergo, Sara

2017-01-01

This work explores the feasibility of applying in situ Raman spectroscopy for the online monitoring of the supercritical carbon dioxide (SC-CO2) drying of fruits. Specifically, we investigate two types of fruits: mango and persimmon. The drying experiments were carried out inside an optical accessible vessel at 10 MPa and 313 K. The Raman spectra reveal: (i) the reduction of the water from the fruit slice and (ii) the change of the fruit matrix structure during the drying process. Two different Raman excitation wavelengths were compared: 532 nm and 785 nm. With respect to the quality of the obtained spectra, the 532 nm excitation wavelength was superior due to a higher signal-to-noise ratio and due to a resonant excitation scheme of the carotenoid molecules. It was found that the absorption of CO2 into the fruit matrix enhances the extraction of water, which was expressed by the obtained drying kinetic curve. PMID:28505120

Unraveling the Raman Enhancement Mechanism on 1T'-Phase ReS2 Nanosheets.

Science.gov (United States)

Miao, Peng; Qin, Jing-Kai; Shen, Yunfeng; Su, Huimin; Dai, Junfeng; Song, Bo; Du, Yunchen; Sun, Mengtao; Zhang, Wei; Wang, Hsing-Lin; Xu, Cheng-Yan; Xu, Ping

2018-04-01

2D transition metal dichalcogenides materials are explored as potential surface-enhanced Raman spectroscopy substrates. Herein, a systematic study of the Raman enhancement mechanism on distorted 1T (1T') rhenium disulfide (ReS 2 ) nanosheets is demonstrated. Combined Raman and photoluminescence studies with the introduction of an Al 2 O 3 dielectric layer unambiguously reveal that Raman enhancement on ReS 2 materials is from a charge transfer process rather than from an energy transfer process, and Raman enhancement is inversely proportional while the photoluminescence quenching effect is proportional to the layer number (thickness) of ReS 2 nanosheets. On monolayer ReS 2 film, a strong resonance-enhanced Raman scattering effect dependent on the laser excitation energy is detected, and a detection limit as low as 10 -9 m can be reached from the studied dye molecules such as rhodamine 6G and methylene blue. Such a high enhancement factor achieved through enhanced charge interaction between target molecule and substrate suggests that with careful consideration of the layer-number-dependent feature and excitation-energy-related resonance effect, ReS 2 is a promising Raman enhancement platform for sensing applications. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of ionizing radiation on in situ Raman scattering and photoluminescence of silica optical fibers

International Nuclear Information System (INIS)

Bilodeau, T.G.; Ewing, K.J.; Nau, G.M.; Aggarwal, I.D.

1995-01-01

Raman fiber optic chemical sensors provide remote situ characterization capability. One application of Raman fiber optic chemical sensors is the characterization of the contents of nuclear waste tanks. In these tanks it is expected that approximately 20 meters of optical fiber will be exposed to radiation levels between 100 and 1,000 rads/hour. In support of this work two silica optical fiber types (one a communications grade fiber and the other nominally radiation resistant) have been tested at the radiation levels expected in the tanks. Luminescence and Raman scattering measurements have been performed in situ with 488-nm excitation on two types of silica optical fiber exposed to a constant low to moderate dose rate of gamma radiation of 880 rads(Si)/hour from a 60 Co source for a total dose of greater than 45 krads. The nominally radiation-resistant fiber was also excited with 514.5-nm and near-infrared 830-nm laser radiation. The rate of the silica Raman signal decrease is more than three times greater for the visible excitation wavelengths than for the 830-nm excitation for the radiation resistant fiber. The behavior of the 650-nm photoluminescence line upon irradiation was different for the two fibers studied, both in terms of the shift of the 650-nm line and rate of increase of the normalized photoluminescence intensity. In all cases the photoluminescence from the fibers was less than the Raman intensity. No radioluminescence was observed in either fiber. The radiation resistant fiber exhibited photo bleaching effects on the Raman transmission when photoannealed with 488-nm laser light

Effect of ionizing radiation on in situ Raman scattering and photoluminescence of silica optical fibers

Science.gov (United States)

Bilodeau, T. G.; Ewing, K. J.; Nau, G. M.; Aggarwai, I. D.

1995-02-01

Raman fiber optic chemical sensors provide remote in situ characterization capability. One application of Raman fiber optic chemical sensors is the characterization of the contents of nuclear waste tanks. In these tanks it is expected that approximately 20 meters of optical fiber will be exposed to radiation levels between 100 and 1000 rads/hour. In support of this work two silica optical fiber types (one a communications grade fiber and the other nominally radiation resistant) have been tested at the radiation levels expected in the tanks. Luminescence and Raman scattering measurements have been performed in situ with 488-nm excitation on two types of silica optical fiber exposed to a constant low to moderate dose rate of gamma radiation of 880 rads(Si)/hour from a /sup 60/Co source for a total dose of greater than 45 krads. The nominally radiation-resistant fiber was also excited with 514.5-nm and near-infrared 830-nm laser radiation. The rate of the silica Raman signal decrease is more than three times greater for the visible excitation wavelengths than for the 830-nm excitation for the radiation resistant fiber. The behavior of the 650-nm photoluminescence line upon irradiation was different for the two fibers studied, both in terms of the shift of the 650-nm line and rate of increase of the normalized photoluminescence intensity. In all cases the photoluminescence from the fibers was less than the Raman intensity. No radioluminescence was observed in either fiber. The radiation resistant fiber exhibited photobleaching effects on the Raman transmission when photoannealed with 488-nm laser light.

Electronic Raman scattering with excitation between localized states observed in the zinc M{sub 2,3} soft x-ray spectra of ZnS

Energy Technology Data Exchange (ETDEWEB)

Zhou, L.; Callcott, T.A.; Jia, J.J. [Univ. of Tennessee, Knoxville, TN (United States)] [and others

1997-04-01

Zn M{sub 2,3} soft x-ray fluorescence (SXF) spectra of ZnS and ZnS{sub .5}Se{sub .5} excited near threshold show strong inelastic scattering effects that can be explained using a simple model and an inelastic scattering theory based on second order perturbation theory. This scattering is often called electronic resonance Raman scattering. Tulkki and Aberg have developed this theory in detail for atomic systems, but their treatment can be applied to solid systems by utilizing electronic states characteristic of solids rather than of atomic systems.

Density functional theory study on Herzberg-Teller contribution in Raman scattering from 4-aminothiophenol-metal complex and metal-4-aminothiophenol-metal junction

Science.gov (United States)

Liu, Shasha; Zhao, Xiuming; Li, Yuanzuo; Zhao, Xiaohong; Chen, Maodu

2009-06-01

Density functional theory (DFT) and time-dependent DFT calculations have been performed to investigate the Raman scattering spectra of metal-molecule complex and metal-molecule-metal junction architectures interconnected with 4-aminothiophenol (PATP) molecule. The simulated profiles of normal Raman scattering (NRS) spectra for the two complexes (Ag2-PATP and PATP-Au2) and the two junctions (Ag2-PATP-Au2 and Au2-PATP-Ag2) are similar to each other, but exhibit obviously different Raman intensities. Due to the lager static polarizabilities of the two junctions, which directly influence the ground state chemical enhancement in NRS spectra, the calculated normal Raman intensities of them are stronger than those of two complexes by the factor of 102. We calculate preresonance Raman scattering (RRS) spectra with incident light at 1064 nm, which is much lower than the S1 electronic transition energy of complexes and junctions. Ag2-PATP-Au2 and Au2-PATP-Ag2 junctions yield higher Raman intensities than those of Ag2-PATP and PATP-Au2 complexes, especially for b2 modes. This effect is mainly attributed to charge transfer (CT) between the metal gap and the PAPT molecule which results in the occurrence of CT resonance enhancement. The calculated pre-RRS spectra strongly depend on the electronic transition state produced by new structures. With excitation at 514.5 nm, the calculated pre-RRS spectra of two complexes and two junctions are stronger than those of with excitation at 1064 nm. A charge difference densities methodology has been used to visually describe chemical enhancement mechanism of RRS spectrum. This methodology aims at visualizing intermolecular CT which provides direct evidence of the Herzberg-Teller mechanism.

Analyzing the fundamental properties of Raman amplification in optical fibers

DEFF Research Database (Denmark)

Rottwitt, Karsten; Povlsen, Jørn Hedegaard

2005-01-01

The Raman response of germanosilicate fibers is presented. This includes not only the material dependence but also the relation between the spatial-mode profile of the light and the Raman response in the time and frequency domain. From the Raman-gain spectrum, information is derived related...

Anomalous lattice vibrations of monolayer MoS 2 probed by ultraviolet Raman scattering

KAUST Repository

Liu, Hsiang Lin; Guo, Huaihong; Yang, Teng; Zhang, Zhidong; Kumamoto, Yasuaki; Shen, Chih Chiang; Hsu, Yu Te; Li, Lain-Jong; Saito, Riichiro; Kawata, Satoshi

2015-01-01

We present a comprehensive Raman scattering study of monolayer MoS2 with increasing laser excitation energies ranging from the near-infrared to the deep-ultraviolet. The Raman scattering intensities from the second-order phonon modes are revealed to be enhanced anomalously by only the ultraviolet excitation wavelength 354 nm. We demonstrate theoretically that such resonant behavior arises from a strong optical absorption that forms near the Γ point and of the band structure and an inter-valley resonant electronic scattering by the M-point phonons. These results advance our understanding of the double resonance Raman scattering process in low-dimensional semiconducting nanomaterials and provide a foundation for the technological development of monolayer MoS2 in the ultraviolet frequency range. © the Owner Societies 2015.

Raman scattering signatures of the unusual vibronic interaction of molecules in liquid helium-3

Energy Technology Data Exchange (ETDEWEB)

Tehver, I., E-mail: imbi.tehver@ut.ee [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); Benedek, G. [Donostia International Physics Center (DIPC) and University of the Basque Country (EHU), Paseo de Lardizabal 4, 20018 Donostia/San Sebastian (Spain); Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, Via Cozzi 53, 20125 Milano (Italy); Hizhnyakov, V. [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia)

2015-10-16

Highlights: • Theory of resonance Raman scattering (RRS) of molecules in {sup 3}He liquid is proposed. • Fermi excitations give essential contribution to RRS. • RRS spectra of glyoxal molecule in {sup 3}He droplets are calculated. - Abstract: Light scattering in quantum liquid helium-3 may involve a unique mechanism – the creation and annihilation of atom excitations across the Fermi level. The density of states of particle–hole excitations in the low-energy limit is strongly enhanced as compared to that of collective excitations of phonons in helium-3. This makes possible to directly observe Fermi excitations in the resonant Raman scattering (RRS) by {sup 3}He droplets doped by impurity molecules. The RRS spectra essentially depend on the excitation frequency. In case of excitation in the anti-Stokes side of absorption the first order RRS is directly determined by the particle–hole excitations in the vicinity of the impurity molecule and the contribution of phonons mainly given by the localized spherical vibration. The calculations are made for a {sup 3}He droplet doped by a glyoxal molecule.

Enhanced Raman scattering assisted by ultrahigh order modes of the double metal cladding waveguide

Energy Technology Data Exchange (ETDEWEB)

Xu, Tian; Huang, Liming; Jin, Yonglong; Fang, Jinghuai, E-mail: cyin.phys@gmail.com, E-mail: fjhuai@ntu.edu.cn [Physics Department, Nantong University, No. 9, Seyuan Road, Nantong, Jiangsu 226007 (China); Yin, Cheng, E-mail: cyin.phys@gmail.com, E-mail: fjhuai@ntu.edu.cn [Jiangsu Key Laboratory of Power Transmission and Distribution Equipment Technology, Hohai University, Changzhou 213022 (China); Huang, Meizhen [Department of Instrument Science and Engineering, Shanghai Jiaotong University, No. 800, DongChuan Road, Shanghai 200240 (China)

2014-10-20

Distinguished from the usual strategy to enhance the Raman scattering such as creating hot spots in the surface-enhanced Raman scattering, this paper takes a quite different approach based on the double metal cladding waveguide. The target analyte is located in the guiding layer of sub-millimeter scale, where several ultrahigh order modes with high intensity are simultaneously excited via a focused laser beam. The experimental setup is simple, and both simulation and experimental results confirm the enhancement mechanism of these oscillating modes. Other appealing features include the large detection area and the ability to excite guided modes via both polarizations. This scheme can be applied to large molecules detection and readily integrated with other Raman enhancement techniques.

Temperature dependence Infrared and Raman studies of III-V/II-VI core-shell nanostructures

Science.gov (United States)

Manciu, Felicia S.; McCombe, Bruce D.; Lucey, Derrick

2005-03-01

The temperature dependence (8 K InP/ZnS sample. Raman scattering (457.9 nm excitation) features were determined without polarization selection in the backscattering geometry. Interesting T-dependent resonant Raman effect of the surface optical phonon modes has been discovered in InP/ZnSe sample. Reasonable agreement is obtained between the Raman and FIR results, as well as with theoretical calculations.

Simulations of the polarisation-dependent Raman intensity of β-carotene in photosystem II crystals

International Nuclear Information System (INIS)

Brose, K.; Zouni, A.; Müh, F.; Mroginski, M.A.; Maultzsch, J.

2013-01-01

Highlights: • First polarisation-dependent Raman spectroscopy on photosystem II crystals. • Orientation-dependent Raman intensity simulations for di- and monomeric crystals. • Simulations account for all β-carotenes (β-Car) in the unit cell for the first time. • Prediction for identificationy of the β-Car cation in side-path electron transport. - Abstract: In order to clarify possibilities to identify the β-carotene (β-Car) radicals in secondary electron transfer (ET) reactions in the photosystem II core complex (PSIIcc), Raman intensities of all 96 β-Car cofactors in the unit cell of PSIIcc-dimer crystals as a function of polarisation and crystal orientation were simulated based on the 2.9 Å resolution structure. The Raman-active symmetry A g in the C 2h group is assigned to the β-Car modes ν 66 and ν 67 . Simulations are in agreement with experiment for off-resonant excitation at 1064 nm. Resonant measurements at 476 and 532 nm excitation can not be explained, which is attributed to mode mixing in the excited state and the existence of different spectral pools. The identity of the β-Car oxidised in secondary ET can not be resolved by Raman measurements on PSIIcc-dimer crystals. Additional simulations show that similar measurements on PSIIcc-monomer crystals could provide a possible route to solve this issue

Simulations of the polarisation-dependent Raman intensity of β-carotene in photosystem II crystals

Energy Technology Data Exchange (ETDEWEB)

Brose, K., E-mail: katharina.brose@gmx.net [Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin (Germany); Zouni, A. [Institut für Chemie, Max-Volmer-Laboratorium, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin (Germany); Müh, F. [Institut für Theoretische Physik, Johannes Kepler Universität Linz, Altenberger Straße 69, 4040 Linz (Austria); Mroginski, M.A. [Institut für Chemie, Max-Volmer-Laboratorium, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin (Germany); Maultzsch, J. [Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin (Germany)

2013-06-03

Highlights: • First polarisation-dependent Raman spectroscopy on photosystem II crystals. • Orientation-dependent Raman intensity simulations for di- and monomeric crystals. • Simulations account for all β-carotenes (β-Car) in the unit cell for the first time. • Prediction for identificationy of the β-Car cation in side-path electron transport. - Abstract: In order to clarify possibilities to identify the β-carotene (β-Car) radicals in secondary electron transfer (ET) reactions in the photosystem II core complex (PSIIcc), Raman intensities of all 96 β-Car cofactors in the unit cell of PSIIcc-dimer crystals as a function of polarisation and crystal orientation were simulated based on the 2.9 Å resolution structure. The Raman-active symmetry A{sub g} in the C{sub 2h} group is assigned to the β-Car modes ν{sub 66} and ν{sub 67}. Simulations are in agreement with experiment for off-resonant excitation at 1064 nm. Resonant measurements at 476 and 532 nm excitation can not be explained, which is attributed to mode mixing in the excited state and the existence of different spectral pools. The identity of the β-Car oxidised in secondary ET can not be resolved by Raman measurements on PSIIcc-dimer crystals. Additional simulations show that similar measurements on PSIIcc-monomer crystals could provide a possible route to solve this issue.

Surface Plasmons and Surface Enhanced Raman Spectra of Aggregated and Alloyed Gold-Silver Nanoparticles

Directory of Open Access Journals (Sweden)

Y. Fleger

2009-01-01

Full Text Available Effects of size, morphology, and composition of gold and silver nanoparticles on surface plasmon resonance (SPR and surface enhanced Raman spectroscopy (SERS are studied with the purpose of optimizing SERS substrates. Various gold and silver films made by evaporation and subsequent annealing give different morphologies and compositions of nanoparticles and thus different position of the SPR peak. SERS measurements of 4-mercaptobenzoic acid obtained from these films reveal that the proximity of the SPR peak to the exciting laser wavelength is not the only factor leading to the highest Raman enhancement. Silver nanoparticles evaporated on top of larger gold nanoparticles show higher SERS than gold-silver alloyed nanoparticles, in spite of the fact that the SPR peak of alloyed nanoparticles is narrower and closer to the excitation wavelength. The highest Raman enhancement was obtained for substrates with a two-peak particle size distribution for excitation wavelengths close to the SPR.

Raman imaging using fixed bandpass filter

Science.gov (United States)

Landström, L.; Kullander, F.; Lundén, H.; Wästerby, P.

2017-05-01

By using fixed narrow band pass optical filtering and scanning the laser excitation wavelength, hyperspectral Raman imaging could be achieved. Experimental, proof-of-principle results from the Chemical Warfare Agent (CWA) tabun (GA) as well as the common CWA simulant tributyl phosphate (TBP) on different surfaces/substrates are presented and discussed.

Polarization Sensitive Coherent Raman Measurements of DCVJ

Science.gov (United States)

Anderson, Josiah; Cooper, Nathan; Lawhead, Carlos; Shiver, Tegan; Ujj, Laszlo

2014-03-01

Coherent Raman spectroscopy which recently developed into coherent Raman microscopy has been used to produce label free imaging of thin layers of material and find the spatial distributions of certain chemicals within samples, e.g. cancer cells.(1) Not all aspects of coherent scattering have been used for imaging. Among those for example are special polarization sensitive measurements. Therefore we have investigated the properties of polarization sensitive CARS spectra of a highly fluorescent molecule, DCVJ.(2) Spectra has been recorded by using parallel polarized and perpendicular polarized excitations. A special polarization arrangement was developed to suppress the non-resonant background scattering from the sample. These results can be used to improve the imaging properties of a coherent Raman microscope in the future. This is the first time coherent Raman polarization sensitive measurements have been used to characterize the vibrational modes of DCVJ. 1: K. I. Gutkowski, et al., ``Fluorescence of dicyanovinyl julolidine in a room temperature ionic liquid '' Chemical Physics Letters 426 (2006) 329 - 333 2: Fouad El-Diasty, ``Coherent anti-Stokes Raman scattering: Spectroscopy and microscopy'' Vibrational Spectroscopy 55 (2011) 1-37

Analysis of albumin Raman scattering in visible and near-infrared ranges

Science.gov (United States)

Lykina, Anastasia A.; Artemyev, Dmitry N.

2018-04-01

In this work the analysis of the shape and intensity of albumin Raman signals in visible and near-IR ranges was carried out. The experimental setup using lasers from the visible region first of all excites the fluorescence of the albumin solution, the main contribution to which is produced by sodium chloride, which is a component of the tested sample. At the same time, lasers from the near-infrared range excited the Raman signal of albumin most effectively. It was found that the highest ratio of Raman scattering to autofluorescence intensities in the detected signal was obtained using a laser with a wavelength of 1064 nm. To determine the albumin solution concentration by type of spectrum, a regression approach with the projection to latent structures method was applied. The lowest predicted error of albumin concentration of 2-3 g/l was obtained by using the near-infrared range lasers.

Feasibility Study of Using High-Temperature Raman Spectroscopy for On-Line Monitoring and Product Control of the Glass Vitrification Process

International Nuclear Information System (INIS)

Windisch, C.F. Jr.; Piepel, G.F.; Li, H.; Elliott, M.L.; Su, Y.

1999-01-01

A pulse-gating Raman spectroscopy setup was developed in this project. The setup was capable of performing in-situ high-temperature Raman measurements for glasses at temperatures as high as 1412 C. In the literature, high-temperature Raman measurements have only been performed on thin films of glass to minimize black-body radiation effects. The pulse-gating Raman setup allows making high-temperature measurements for bulk melts while effectively minimizing black-body radiation effects. A good correlation was found between certain Raman characteristic parameters and glass melt temperature for sodium silicate glasses measured in this project. Comparisons were made between the high-temperature Raman data from this study and literature data. The results suggest that an optimization of the pulse-gating Raman setup is necessary to further improve data quality (i.e., to obtain data with a higher signal-to-noise ratio). An W confocal Raman microspectrometer with continuous wave laser excitation using a 325 nm excitation line was evaluated selectively using a transparent silicate glass ad a deep-colored high-level waste glass in a bulk quantity. The data were successfully collected at temperatures as high as approximately 1500 C. The results demonstrated that the UV excitation line can be used for high-temperature Raman measurements of molten glasses without black-body radiation interference from the melt for both transparent and deep-color glasses. Further studies are needed to select the best laser system that can be used to develop high-temperature Raman glass databases

Laser-induced gratings in the gas phase excited via Raman-active transitions

Energy Technology Data Exchange (ETDEWEB)

Kozlov, D N [General Physics Inst., Russian Academy of Sciences, Moscow (Russian Federation); Bombach, R; Hemmerling, B; Hubschmid, W [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1997-06-01

We report on a new time resolved coherent Raman technique that is based on the generation of thermal gratings following a population change among molecular levels induced by stimulated Raman pumping. This is achieved by spatially and temporally overlapping intensity interference patterns generated independently by two lasers. When this technique is used in carbon dioxide, employing transitions which belong to the Q-branches of the {nu}{sub 1}/2{nu}{sub 2} Fermi dyad, it is possible to investigate molecular energy transfer processes. (author) 2 figs., 10 refs.

Combined fluorescence-Raman spectroscopy measurements with an optical fiber probe for the diagnosis of melanocytic lesions

Science.gov (United States)

Cosci, Alessandro; Cicchi, Riccardo; Rossari, Susanna; De Giorgi, Vincenzo; Massi, Daniela; Pavone, Francesco S.

2012-02-01

We have designed and developed an optical fiber-probe for spectroscopic measurements on human tissues. The experimental setup combines fluorescence spectroscopy and Raman spectroscopy in a multidimensional approach. Concerning fluorescence spectroscopy, the excitation is provided by two laser diodes, one emitting in the UV (378 nm) and the other emitting in the visible (445 nm). These two lasers are used to selectively excite fluorescence from NADH and FAD, which are among the brightest endogenous fluorophores in human tissues. For Raman and NIR spectroscopy, the excitation is provided by a third laser diode with 785 nm excitation wavelength. Laser light is delivered to the tissue through the central optical fiber of a fiber bundle. The surrounding 48 fibers of the bundle are used for collecting fluorescence and Raman and for delivering light to the spectrograph. Fluorescence and Raman spectra are acquired on a cooled CCD camera. The instrument has been tested on fresh human skin biopsies clinically diagnosed as malignant melanoma, melanocytic nevus, or healthy skin, finding an optimal correlation with the subsequent histological exam. In some cases our examination was not in agreement with the clinical observation, but it was with the histological exam, demonstrating that the system can potentially contribute to improve clinical diagnostic capabilities and hence reduce the number of unnecessary biopsies.

Progress report of FY 1997 activities: The application of Kalman filtering to derive water vapor profiles from combined ground-based sensors: Raman lidar, microwave radiometers, GPS, and radiosondes

International Nuclear Information System (INIS)

Edgeworth R. Westwater; Yong Han

1997-01-01

Previously, the proposers have delivered to ARM a documented algorithm, that is now applied operationally, and which derives water vapor profiles from combined remote sensor measurements of water vapor radiometers, cloud-base ceilometers, and radio acoustic sounding systems (RASS). With the expanded deployment of a Raman lidar at the CART Central Facility, high quality, high vertical-resolution, water vapor profiles will be provided during nighttime clear conditions, and during clear daytime conditions, to somewhat lower altitudes. The object of this proposal was to use Kalman Filtering, previously applied to the combination of nighttime Raman lidar and microwave radiometer data, to derive high-quality water vapor profiles, during non-precipitating conditions, from data routinely available at the CART site. Input data to the algorithm would include: Raman lidar data, highly quality-controlled data of integrated moisture from microwave radiometers and GPS, RASS, and radiosondes. The algorithm will include recently-developed quality control procedures for radiometers. The focus of this years activities has been on the intercomparison of data obtained during an intensive operating period at the SGP CART site in central Oklahoma

Surface enhanced Raman scattering spectroscopic waveguide

Science.gov (United States)

Lascola, Robert J; McWhorter, Christopher S; Murph, Simona H

2015-04-14

A waveguide for use with surface-enhanced Raman spectroscopy is provided that includes a base structure with an inner surface that defines a cavity and that has an axis. Multiple molecules of an analyte are capable of being located within the cavity at the same time. A base layer is located on the inner surface of the base structure. The base layer extends in an axial direction along an axial length of an excitation section. Nanoparticles are carried by the base layer and may be uniformly distributed along the entire axial length of the excitation section. A flow cell for introducing analyte and excitation light into the waveguide and a method of applying nanoparticles may also be provided.

Development of a tunable femtosecond stimulated raman apparatus and its application to beta-carotene.

Science.gov (United States)

Shim, Sangdeok; Mathies, Richard A

2008-04-17

We have developed a tunable femtosecond stimulated Raman spectroscopy (FSRS) apparatus and used it to perform time-resolved resonance Raman experiments with Raman excitation, the resonant S1 state modes are enhanced by a factor of approximately 200 compared with 800 nm FSRS experiments. The improved signal-to-noise ratios facilitate the measurement of definitive time constants for beta-carotene dynamics including the 180 fs appearance of the S1 vibrational features due to direct internal conversion from S2 and their characteristic 9 ps decay to S0. By tuning the FSRS system to 590 nm Raman excitation, we are able to selectively enhance vibrational features of the hot ground state S hot 0 and monitor its approximately 5 ps cooling dynamics. This tunable FSRS system is valuable because it facilitates the direct observation of structural changes of selected resonantly enhanced states and intermediates during photochemical and photobiological reactions.

Validating in vivo Raman spectroscopy of bone in human subjects

Science.gov (United States)

Esmonde-White, Francis W. L.; Morris, Michael D.

2013-03-01

Raman spectroscopy can non-destructively measure properties of bone related to mineral density, mineral composition, and collagen composition. Bone properties can be measured through the skin in animal and human subjects, but correlations between the transcutaneous and exposed bone measurements have only been reported for human cadavers. In this study, we examine human subjects to collect measurements transcutaneously, on surgically exposed bone, and on recovered bone fragments. This data will be used to demonstrate in vivo feasibility and to compare transcutaneous and exposed Raman spectroscopy of bone. A commercially available Raman spectrograph and optical probe operating at 785 nm excitation are used for the in vivo measurements. Requirements for applying Raman spectroscopy during a surgery are also discussed.

Resonance Raman spectroscopy in one-dimensional carbon materials

Directory of Open Access Journals (Sweden)

Dresselhaus Mildred S.

2006-01-01

Full Text Available Brazil has played an important role in the development and use of resonance Raman spectroscopy as a powerful characterization tool for materials science. Here we present a short history of Raman scattering research in Brazil, highlighting the important contributions to the field coming from Brazilian researchers in the past. Next we discuss recent and important contributions where Brazil has become a worldwide leader, that is on the physics of quasi-one dimensional carbon nanotubes. We conclude this article by presenting results from a very recent resonance Raman study of exciting new materials, that are strictly one-dimensional carbon chains formed by the heat treatment of very pure double-wall carbon nanotube samples.

Laser remote sensing of water vapor: Raman lidar development

International Nuclear Information System (INIS)

Goldsmith, J.E.M.; Lapp, M.; Bisson, S.E.; Melfi, S.H.; Whiteman, D.N.; Ferrare, R.A.; Evans, K.D.

1994-01-01

The goal of this research is the development of a critical design for a Raman lidar system optimized to match ARM Program needs for profiling atmospheric water vapor at CART sites. This work has emphasized the development of enhanced daytime capabilities using Raman lidar techniques. This abstract touches briefly on the main components of the research program, summarizing results of the efforts. A detailed Raman lidar instrument model has been developed to predict the daytime and nighttime performance capabilities of Raman lidar systems. The model simulates key characteristics of the lidar system, using realistic atmospheric profiles, modeled background sky radiance, and lidar system parameters based on current instrument capabilities. The model is used to guide development of lidar systems based on both the solar-blind concept and the narrowband, narrow field-of-view concept for daytime optimization

Interaction of the modulated electron beam with inhomogeneous plasma: plasma density profile deformation and langmuir waves excitation

International Nuclear Information System (INIS)

Anisimov, I.O.; Kelnyk, O.I.; Soroka, S.V.; Siversky, T.V.

2005-01-01

Nonlinear deformation of the initially linear plasma density profile due to the modulated electron beam is studied via computer simulation. In the initial time period the field slaves to the instantaneous profile of the plasma density. Langmuir waves excitation is suppressed by the density profile deformation. The character of the plasma density profile deformation for the late time period depends significantly on the plasma properties. Particularly, for plasma with hot electrons quasi-periodic generation of ion-acoustic pulses takes place in the vicinity of the initial point of plasma resonance

Quantitative detection of caffeine in human skin by confocal Raman spectroscopy--A systematic in vitro validation study.

Science.gov (United States)

Franzen, Lutz; Anderski, Juliane; Windbergs, Maike

2015-09-01

For rational development and evaluation of dermal drug delivery, the knowledge of rate and extent of substance penetration into the human skin is essential. However, current analytical procedures are destructive, labor intense and lack a defined spatial resolution. In this context, confocal Raman microscopy bares the potential to overcome current limitations in drug depth profiling. Confocal Raman microscopy already proved its suitability for the acquisition of qualitative penetration profiles, but a comprehensive investigation regarding its suitability for quantitative measurements inside the human skin is still missing. In this work, we present a systematic validation study to deploy confocal Raman microscopy for quantitative drug depth profiling in human skin. After we validated our Raman microscopic setup, we successfully established an experimental procedure that allows correlating the Raman signal of a model drug with its controlled concentration in human skin. To overcome current drawbacks in drug depth profiling, we evaluated different modes of peak correlation for quantitative Raman measurements and offer a suitable operating procedure for quantitative drug depth profiling in human skin. In conclusion, we successfully demonstrate the potential of confocal Raman microscopy for quantitative drug depth profiling in human skin as valuable alternative to destructive state-of-the-art techniques. Copyright © 2015 Elsevier B.V. All rights reserved.

Femtosecond time-resolved impulsive stimulated Raman spectroscopy using sub-7-fs pulses: Apparatus and applications

Energy Technology Data Exchange (ETDEWEB)

Kuramochi, Hikaru [Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako 351-0198 (Japan); Takeuchi, Satoshi; Tahara, Tahei, E-mail: tahei@riken.jp [Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako 351-0198 (Japan); Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), 2-1 Hirosawa, Wako 351-0198 (Japan)

2016-04-15

We describe details of the setup for time-resolved impulsive stimulated Raman spectroscopy (TR-ISRS). In this method, snapshot molecular vibrational spectra of the photoreaction transients are captured via time-domain Raman probing using ultrashort pulses. Our instrument features transform-limited sub-7-fs pulses to impulsively excite and probe coherent nuclear wavepacket motions, allowing us to observe vibrational fingerprints of transient species from the terahertz to 3000-cm{sup −1} region with high sensitivity. Key optical components for the best spectroscopic performance are discussed. The TR-ISRS measurements for the excited states of diphenylacetylene in cyclohexane are demonstrated, highlighting the capability of our setup to track femtosecond dynamics of all the Raman-active fundamental molecular vibrations.

Temperature dependence of the hydrated electron's excited-state relaxation. I. Simulation predictions of resonance Raman and pump-probe transient absorption spectra of cavity and non-cavity models

Science.gov (United States)

Zho, Chen-Chen; Farr, Erik P.; Glover, William J.; Schwartz, Benjamin J.

2017-08-01

We use one-electron non-adiabatic mixed quantum/classical simulations to explore the temperature dependence of both the ground-state structure and the excited-state relaxation dynamics of the hydrated electron. We compare the results for both the traditional cavity picture and a more recent non-cavity model of the hydrated electron and make definite predictions for distinguishing between the different possible structural models in future experiments. We find that the traditional cavity model shows no temperature-dependent change in structure at constant density, leading to a predicted resonance Raman spectrum that is essentially temperature-independent. In contrast, the non-cavity model predicts a blue-shift in the hydrated electron's resonance Raman O-H stretch with increasing temperature. The lack of a temperature-dependent ground-state structural change of the cavity model also leads to a prediction of little change with temperature of both the excited-state lifetime and hot ground-state cooling time of the hydrated electron following photoexcitation. This is in sharp contrast to the predictions of the non-cavity model, where both the excited-state lifetime and hot ground-state cooling time are expected to decrease significantly with increasing temperature. These simulation-based predictions should be directly testable by the results of future time-resolved photoelectron spectroscopy experiments. Finally, the temperature-dependent differences in predicted excited-state lifetime and hot ground-state cooling time of the two models also lead to different predicted pump-probe transient absorption spectroscopy of the hydrated electron as a function of temperature. We perform such experiments and describe them in Paper II [E. P. Farr et al., J. Chem. Phys. 147, 074504 (2017)], and find changes in the excited-state lifetime and hot ground-state cooling time with temperature that match well with the predictions of the non-cavity model. In particular, the experiments

Resonance Polarization and Phase-Mismatched CARS of Pheophytin b Excited in the Qy Band

NARCIS (Netherlands)

de Boeij, W.P.; Lucassen, G.W.; Lucassen, Gerald; Otto, Cornelis; Greve, Jan

1993-01-01

Resonance polarization and phase-mismatched coherent anti-Stokes Raman scattering (CARS) measurements were performed on pheophytin b dissolved in acetone excited in the Qy absorption band, where strong broad fluorescence makes spontaneous Raman spectroscopy impossible. The phase-mismatching

Temperature dependence of Raman spectra of Basub(0.25)Srsub(0.75)Nbsub(2)Osub(6) crystal

International Nuclear Information System (INIS)

Rustamov, Kh.Sh.; Gorelik, V.S.; Kuz'minov, Yu.S.; Peregudov, G.V.; Sushchinskij, M.M.

1976-01-01

The nature of the changes is studied in the Raman spectra in a crystal of Basub(x)Srsub(1-x)Nasub(2)Osub(6) (x=0.25) with the temperature range of 80 to 373 K. Normal procedure was applied with the use of an argon laser (Λ=4880 A) and a DFS-12 spectrometer. It has been established that at low temperatures the spectrum becomes more clear-cut; in the low-frequency range some sharp lines appear in the immediate vicinity of the exciting line. On heating of the crystal one observes a redistribution of the intensity in the Raman spectrum and a general displacement of the low-frequency Raman spectrum and a general displacement of the low-frequency Raman spectrum toward the exciting line. The nature of the frequency shifts some Raman maxima was investigated, and certain anomalies were observed in the vicinity of the phase transition point

Surface enhanced raman spectroscopy analytical, biophysical and life science applications

CERN Document Server

Schlücker, Sebastian

2013-01-01

Covering everything from the basic theoretical and practical knowledge to new exciting developments in the field with a focus on analytical and life science applications, this monograph shows how to apply surface-enhanced Raman scattering (SERS) for solving real world problems. From the contents: * Theory and practice of SERS * Analytical applications * SERS combined with other analytical techniques * Biophysical applications * Life science applications including various microscopies Aimed at analytical, surface and medicinal chemists, spectroscopists, biophysicists and materials scientists. Includes a Foreword by the renowned Raman spectroscopist Professor Wolfgang Kiefer, the former Editor-in-Chief of the Journal of Raman Spectroscopy.

Multiwavelength excitation Raman scattering of Cu2ZnSn(SxSe1−x)4 (0 ≤ x ≤ 1) polycrystalline thin films: Vibrational properties of sulfoselenide solid solutions

International Nuclear Information System (INIS)

Dimitrievska, Mirjana; Xie, Haibing; Fairbrother, Andrew; Fontané, Xavier; Saucedo, Edgardo; Izquierdo-Roca, Victor; Gurieva, Galina; 2UB, Departament d'Electrònica, Universitat de Barcelona, C. Martí i Franquès 1, 08028 Barcelona (Spain))" data-affiliation=" (Catalonia Institute for Energy Research (IREC), Jardins de les Dones de Negre 1 2pl., 08930 Sant Adrià del Besòs, Barcelona (Spain); IN2UB, Departament d'Electrònica, Universitat de Barcelona, C. Martí i Franquès 1, 08028 Barcelona (Spain))" >Pérez-Rodríguez, Alejandro; Schorr, Susan

2014-01-01

In this work, Raman spectroscopy and X-ray diffraction were applied together to evaluate the crystal structure and the phonon modes of photovoltaic grade Cu 2 ZnSn(S x Se 1−x ) 4 thin films, leading to a complete characterization of their structural and vibrational properties. Vibrational characterization has been based on Raman scattering measurements performed with different excitation wavelengths and polarization configurations. Analysis of the experimental spectra has permitted identification of 19 peaks, which positions are in good accord with theoretical predictions. Besides, the observation of Cu 2 ZnSnS 4 -like A symmetry peaks related to S vibrations and Cu 2 ZnSnSe 4 -like A symmetry peaks related to Se vibrations, additional Raman peaks, characteristic of the solid solution and previously not reported, are observed, and are attributed to vibrations involving both S and Se anions.

Experimental and ab initio DFT calculated Raman Spectrum of Sudan I, a Red Dye

DEFF Research Database (Denmark)

Kunov-Kruse, Andreas Jonas; Kristensen, Steffen Buus; Liu, Chuan

2011-01-01

The red dye Sudan I was investigated by Raman spectroscopy using different excitation wavelengths (1064, 532 and 244 nm). A calculation of the Raman spectrum based on quantum mechanical ab initio density functional theory (DFT) was made using the RB3LYP method with the 3-21G and 6-311+G(d,p) basis...... of the Sudan I molecule was involved in the majority of the vibrations through N N and C–N stretching and various bending modes. Low-intensity bands in the lower wavenumber range (at about 721, 616, 463 and 218 cm−1) were selectively enhanced by the resonance Raman effect when using the 532 nm excitation line....... Comparison was made with other azo dyes in the literature on natural, abundant plant pigments. The results show that there is a possibility in foodstuff analysis to distinguish Sudan I from other dyes by using Raman spectroscopy with more than one laser wavelength for resonance enhancement of the different...

Temperature and polarization dependent Raman measurements of Ca{sub 2}RuO{sub 4}

Energy Technology Data Exchange (ETDEWEB)

German, Raphael [II. Physikalisches Institut, Univ. Koeln (Germany)

2016-07-01

Ca{sub 2}RuO{sub 4} is a Mott-like insulator, which undergoes a metal-insulator transition at 357 K and antiferromagnetic ordering at T{sub N} = 110 K. Here, we report a temperature and polarization dependent Raman scattering study. Earlier studies claimed a Raman active two-magnon excitation around 100 cm{sup -1}. This, however, is incompatible with the results from recent inelastic neutron scattering measurements, which suggest that this mode might be of single magnon nature. Instead, it is more likely that the feature which appears at ∝ 650 cm{sup -1}, previously claimed to be due to a charge gap, has a two-magnon origin. Another open question in the interpretation of the Raman spectra is the origin of the high-energy peak at ∝1360 cm{sup -1}. We will discuss the origin of the Raman peaks in terms of one- and two-magnon processes; magnon-phonon coupling, and possible crystal field excitations.

Raman tweezers spectroscopy of live, single red and white blood cells.

Directory of Open Access Journals (Sweden)

Aseefhali Bankapur

Full Text Available An optical trap has been combined with a Raman spectrometer to make high-resolution measurements of Raman spectra of optically-immobilized, single, live red (RBC and white blood cells (WBC under physiological conditions. Tightly-focused, near infrared wavelength light (1064 nm is utilized for trapping of single cells and 785 nm light is used for Raman excitation at low levels of incident power (few mW. Raman spectra of RBC recorded using this high-sensitivity, dual-wavelength apparatus has enabled identification of several additional lines; the hitherto-unreported lines originate purely from hemoglobin molecules. Raman spectra of single granulocytes and lymphocytes are interpreted on the basis of standard protein and nucleic acid vibrational spectroscopy data. The richness of the measured spectrum illustrates that Raman studies of live cells in suspension are more informative than conventional micro-Raman studies where the cells are chemically bound to a glass cover slip.

Experimental characterization of Raman overlaps between mode-groups

DEFF Research Database (Denmark)

Christensen, Erik Nicolai; Koefoed, Jacob Gade; Friis, Søren Michael Mørk

2016-01-01

Mode-division multiplexing has the potential to further increase data transmission capacity through optical fibers. In addition, distributed Raman amplification is a promising candidate for multi-mode signal amplification due to its desirable noise properties and the possibility of mode-equalized......Mode-division multiplexing has the potential to further increase data transmission capacity through optical fibers. In addition, distributed Raman amplification is a promising candidate for multi-mode signal amplification due to its desirable noise properties and the possibility of mode......-equalized gain. In this paper, we present an experimental characterization of the intermodal Raman intensity overlaps of a few-mode fiber using backward-pumped Raman amplification. By varying the input pump power and the degree of higher order mode-excitation for the pump and the signal in a 10km long two......-mode fiber, we are able to characterize all intermodal Raman intensity overlaps. Using these results, we perform a Raman amplification measurement and demonstrate a mode-differential gain of only 0.25dB per 10dB overall gain. This is, to the best of our knowledge, the lowest mode differential gain achieved...

[Micro-Raman and fluorescence spectra of several agrochemicals].

Science.gov (United States)

Xiao, Yi-lin; Zhang, Peng-xiang; Qian, Xiao-fan

2004-05-01

Raman and fluorescence spectra from several agrochemicals were measured, which are sold for the use in vegetables, fruits and grains. Characteristic vibration Raman peaks from some of the agrochemicals were recorded, hence the spectra can be used for their identification. Other marketed agrochemicals demonstrated strong fluorescence under 514.5 nm excitation. It was found that the fluorescence spectra of the agrochemicals are very different. According to these results one can detect the trace amount of agrochemicals left on the surface of fruits, vegetables and grains in situ and conveniently.

The Raman and vibronic activity of intermolecular vibrations in aromatic-containing complexes and clusters

International Nuclear Information System (INIS)

Maxton, P.M.; Schaeffer, M.W.; Ohline, S.M.; Kim, W.; Venturo, V.A.; Felker, P.M.

1994-01-01

Theoretical and experimental results pertaining to the excitation of intermolecular vibrations in the Raman and vibronic spectra of aromatic-containing, weakly bound complexes and clusters are reported. The theoretical analysis of intermolecular Raman activity is based on the assumption that the polarizability tensor of a weakly bound species is given by the sum of the polarizability tensors of its constituent monomers. The analysis shows that the van der Waals bending fundamentals in aromatic--rare gas complexes may be expected to be strongly Raman active. More generally, it predicts strong Raman activity for intermolecular vibrations that involve the libration or internal rotation of monomer moieties having appreciable permanent polarizability anisotropies. The vibronic activity of intermolecular vibrations in aromatic-rare gas complexes is analyzed under the assumption that every vibronic band gains its strength from an aromatic-localized transition. It is found that intermolecular vibrational excitations can accompany aromatic-localized vibronic excitations by the usual Franck--Condon mechanism or by a mechanism dependent on the librational amplitude of the aromatic moiety during the course of the pertinent intermolecular vibration. The latter mechanism can impart appreciable intensity to bands that are forbidden by rigid-molecule symmetry selection rules. The applicability of such rules is therefore called into question. Finally, experimental spectra of intermolecular transitions, obtained by mass-selective, ionization-detected stimulated Raman spectroscopies, are reported for benzene--X (X=Ar, --Ar 2 , N 2 , HCl, CO 2 , and --fluorene), fluorobenzene--Ar and --Kr, aniline--Ar, and fluorene--Ar and --Ar 2 . The results support the conclusions of the theoretical analyses and provide further evidence for the value of Raman methods in characterizing intermolecular vibrational level structures

Intracellular degradation of microspheres based on cross-linked dextran hydrogels or amphiphilic block copolymers: A comparative Raman microscopy study

Science.gov (United States)

van Manen, Henk-Jan; van Apeldoorn, Aart A; Verrijk, Ruud; van Blitterswijk, Clemens A; Otto, Cees

2007-01-01

Micro- and nanospheres composed of biodegradable polymers show promise as versatile devices for the controlled delivery of biopharmaceuticals. Whereas important properties such as drug release profiles, biocompatibility, and (bio)degradability have been determined for many types of biodegradable particles, information about particle degradation inside phagocytic cells is usually lacking. Here, we report the use of confocal Raman microscopy to obtain chemical information about cross-linked dextran hydrogel microspheres and amphiphilic poly(ethylene glycol)-terephthalate/poly(butylene terephthalate) (PEGT/PBT) microspheres inside RAW 264.7 macrophage phagosomes. Using quantitative Raman microspectroscopy, we show that the dextran concentration inside phagocytosed dextran microspheres decreases with cell incubation time. In contrast to dextran microspheres, we did not observe PEGT/PBT microsphere degradation after 1 week of internalization by macrophages, confirming previous studies showing that dextran microsphere degradation proceeds faster than PEGT/PBT degradation. Raman microscopy further showed the conversion of macrophages to lipid-laden foam cells upon prolonged incubation with both types of microspheres, suggesting that a cellular inflammatory response is induced by these biomaterials in cell culture. Our results exemplify the power of Raman microscopy to characterize microsphere degradation in cells and offer exciting prospects for this technique as a noninvasive, label-free optical tool in biomaterials histology and tissue engineering. PMID:17722552

Raman spectroscopy as a process analytical technology for pharmaceutical manufacturing and bioprocessing.

Science.gov (United States)

Esmonde-White, Karen A; Cuellar, Maryann; Uerpmann, Carsten; Lenain, Bruno; Lewis, Ian R

2017-01-01

Adoption of Quality by Design (QbD) principles, regulatory support of QbD, process analytical technology (PAT), and continuous manufacturing are major factors effecting new approaches to pharmaceutical manufacturing and bioprocessing. In this review, we highlight new technology developments, data analysis models, and applications of Raman spectroscopy, which have expanded the scope of Raman spectroscopy as a process analytical technology. Emerging technologies such as transmission and enhanced reflection Raman, and new approaches to using available technologies, expand the scope of Raman spectroscopy in pharmaceutical manufacturing, and now Raman spectroscopy is successfully integrated into real-time release testing, continuous manufacturing, and statistical process control. Since the last major review of Raman as a pharmaceutical PAT in 2010, many new Raman applications in bioprocessing have emerged. Exciting reports of in situ Raman spectroscopy in bioprocesses complement a growing scientific field of biological and biomedical Raman spectroscopy. Raman spectroscopy has made a positive impact as a process analytical and control tool for pharmaceutical manufacturing and bioprocessing, with demonstrated scientific and financial benefits throughout a product's lifecycle.

Characterization of Barium Borate Frameworks Using Raman Spectroscopy.

Science.gov (United States)

Gharavi-Naeini, Jafar; Yoo, Kyung W; Stump, Nathan A

2018-04-01

Systematic micro-Raman scattering investigations have been carried out on Sm +2 doped 2(BaO)-n(B 2 O 3 ) matrices for n = 4, 5, 8, and 2(BaO)-(Na 2 O)-9(B 2 O 3 ) using the 364 nm excitation of an Ar + laser. The Raman results have been compared with the known structures of barium tetraborate, barium pentaborate, barium octaborate, and barium sodium nonaborate. An excellent correlation has been found between the BO 4 /BO 3 composition ratios for each product and intensity ratios of the designated BO 4 and BO 3 Raman peaks. Furthermore, the Raman frequencies of both BO 4 and BO 3 groups undergo a systematic blueshift as n increases from four to nine. The shift results from a decrease of the B-O bond lengths for both BO 4 and BO 3 groups as the samples transition from the tetraborate to nonaborate structures. Linear relations (with negative slopes) have been determined between the measured Raman frequencies and B-O bond lengths in the frameworks.

Schwinger–Keldysh canonical formalism for electronic Raman scattering

Energy Technology Data Exchange (ETDEWEB)

Su, Yuehua, E-mail: suyh@ytu.edu.cn

2016-03-01

Inelastic low-energy Raman and high-energy X-ray scatterings have made great progress in instrumentation to investigate the strong electronic correlations in matter. However, theoretical study of the relevant scattering spectrum is still a challenge. In this paper, we present a Schwinger–Keldysh canonical perturbation formalism for the electronic Raman scattering, where all the resonant, non-resonant and mixed responses are considered uniformly. We show how to use this formalism to evaluate the cross section of the electronic Raman scattering off an one-band superconductor. All the two-photon scattering processes from electrons, the non-resonant charge density response, the elastic Rayleigh scattering, the fluorescence, the intrinsic energy-shift Raman scattering and the mixed response, are included. In the mean-field superconducting state, Cooper pairs contribute only to the non-resonant response. All the other responses are dominated by the single-particle excitations and are strongly suppressed due to the opening of the superconducting gap. Our formalism for the electronic Raman scattering can be easily extended to study the high-energy resonant inelastic X-ray scattering.

Raman study of electronic excitations in MgB2 with application of high magnetic field

International Nuclear Information System (INIS)

Machtoub, L.; Takano, Y.; Kito, H.

2006-01-01

We present the first results of Raman scattering with application of magnetic field on magnesium diboride (MgB 2 ). In this work, we have investigated the magnetic field dependence of the 72 meV (E 2g mode) and the pair-breaking peak around 100 cm -1 which corresponds to σ-band gap. Intensity enhancement of Raman features around 800 cm -1 accompanied with broadening in the line shape of E 2g mode has been observed in some polycrystalline samples at 0 GPa. Results are compared with previous Raman study under hydrostatic pressure

Confocal Raman Microspectroscopy: The Measurement of VX Depth Profiles in Hairless Guinea Pig Skin and the Evaluation of RSDL

Science.gov (United States)

2015-02-01

USAMRICD-TR-15-01 Confocal Raman Microspectroscopy: The Measurement of VX Depth Profiles in Hairless Guinea Pig Skin and the Evaluation...5a. CONTRACT NUMBER guinea pig skin and the evaluation of RSDL 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Braue, EH...upper skin layers of hairless guinea pigs and to determine the ability of Reactive Skin Decontamination Lotion (RSDL) to remove or degrade VX from

Depth-profiling by confocal Raman microscopy (CRM): data correction by numerical techniques.

Science.gov (United States)

Tomba, J Pablo; Eliçabe, Guillermo E; Miguel, María de la Paz; Perez, Claudio J

2011-03-01

The data obtained in confocal Raman microscopy (CRM) depth profiling experiments with dry optics are subjected to significant distortions, including an artificial compression of the depth scale, due to the combined influence of diffraction, refraction, and instrumental effects that operate on the measurement. This work explores the use of (1) regularized deconvolution and (2) the application of simple rescaling of the depth scale as methodologies to obtain an improved, more precise, confocal response. The deconvolution scheme is based on a simple predictive model for depth resolution and the use of regularization techniques to minimize the dramatic oscillations in the recovered response typical of problem inversion. That scheme is first evaluated using computer simulations on situations that reproduce smooth and sharp sample transitions between two materials and finally it is applied to correct genuine experimental data, obtained in this case from a sharp transition (planar interface) between two polymeric materials. It is shown that the methodology recovers very well most of the lost profile features in all the analyzed situations. The use of simple rescaling appears to be only useful for correcting smooth transitions, particularly those extended over distances larger than those spanned by the operative depth resolution, which limits the strategy to the study of profiles near the sample surface. However, through computer simulations, it is shown that the use of water immersion objectives may help to reduce optical distortions and to expand the application window of this simple methodology, which could be useful, for instance, to safely monitor Fickean sorption/desorption of penetrants in polymer films/coatings in a nearly noninvasive way.

Templated green synthesis of plasmonic silver nanoparticles in onion epidermal cells suitable for surface-enhanced Raman and hyper-Raman scattering

DEFF Research Database (Denmark)

Palanco, Marta Espina; Mogensen, Klaus Bo; Guehlke, Marina

2016-01-01

We report fast and simple green synthesis of plasmonic silver nanoparticles in the epidermal cells of onions after incubation with AgNO3 solution. The biological environment supports the generation of silver nanostructures in two ways. The plant tissue delivers reducing chemicals for the initial...... for one-and two-photon-excited spectroscopy such as surface enhanced Raman scattering (SERS) and surface enhanced hyper-Raman scattering (SEHRS). Our studies demonstrate a templated green preparation of enhancing plasmonic nanoparticles and suggest a new route to deliver silver nanoparticles as basic...... building blocks of plasmonic nanosensors to plants by the uptake of solutions of metal salts....

Raman spectra of SDW superconductors

Energy Technology Data Exchange (ETDEWEB)

Rout, G.C. [Condensed Matter Physics Group, Department of Physics, Government Science College, Chatrapur, Orissa 761 020 (India)]. E-mail: gcr@iopb.res.in; Bishoyi, K.C. [P.G. Department of Physics, F.M. College (Autonomous), Balasore, Orissa 756 001 (India); Behera, S.N. [Institute of Physics, Bhubaneswar 751 005 (India)

2005-03-15

We report the calculation of the phonon response of the coexistent spin density wave (SDW) and superconducting (SC) state and predict the observation of SC gap in the Raman spectra of rare-earth nickel borocarbide superconductors. The SDW state normally does not couple to the lattice and hence, the phonons in the system are not expected to be affected by the SDW state. But there is a possibility of observing SC gap mode in the Raman spectra of a SDW superconductor due to the coupling of the SC gap excitation to the Raman active phonons in the system via the electron-phonon (e-p) interaction. A theoretical model is used for the coexistent phase and electron-phonon interaction. Phonon Green's function is calculated by Zubarev's technique and the phonon self-energy due to e-p interaction which is given by electron density response function in the coexistent state corresponding to the SDW wave vector q = Q is evaluated. The results so obtained exhibit agreement with the experimental observations.

Raman spectra of SDW superconductors

International Nuclear Information System (INIS)

Rout, G.C.; Bishoyi, K.C.; Behera, S.N.

2005-01-01

We report the calculation of the phonon response of the coexistent spin density wave (SDW) and superconducting (SC) state and predict the observation of SC gap in the Raman spectra of rare-earth nickel borocarbide superconductors. The SDW state normally does not couple to the lattice and hence, the phonons in the system are not expected to be affected by the SDW state. But there is a possibility of observing SC gap mode in the Raman spectra of a SDW superconductor due to the coupling of the SC gap excitation to the Raman active phonons in the system via the electron-phonon (e-p) interaction. A theoretical model is used for the coexistent phase and electron-phonon interaction. Phonon Green's function is calculated by Zubarev's technique and the phonon self-energy due to e-p interaction which is given by electron density response function in the coexistent state corresponding to the SDW wave vector q = Q is evaluated. The results so obtained exhibit agreement with the experimental observations

Following lipids in the food chain: determination of the iodine value using Raman micro-spectroscopy

Czech Academy of Sciences Publication Activity Database

Samek, Ota; Zemánek, Pavel; Bernatová, Silvie; Pilát, Zdeněk; Telle, H.H.

2012-01-01

Roč. 24, č. 3 (2012), s. 18-21 ISSN 0966-0941 R&D Projects: GA ČR GAP205/11/1687; GA MŠk ED0017/01/01 Institutional support: RVO:68081731 Keywords : Raman micro-spectroscopy * Raman laser excitation * lipids Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

Design Considerations for a Portable Raman Probe Spectrometer for Field Forensics

Directory of Open Access Journals (Sweden)

James F. Kelly

2012-01-01

Full Text Available Raman spectroscopy has been shown to be a viable method for explosives detection. Currently most forensic Raman systems are either large, powerful instruments for laboratory experiments or handheld instruments for in situ point detection. We have chosen to examine the performance of certain benchtop Raman probe systems with the goal of developing an inexpensive, portable system that could be used to operate in a field forensics laboratory to examine explosives-related residues or samples. To this end, a rugged, low distortion line imaging dispersive Raman spectrograph was configured to work at 830 nm laser excitation and was used to determine whether the composition of thin films of plastic explosives or small (e.g., ≤10 μm particles of RDX or other explosives or oxidizers can be detected, identified, and quantified in the field. With 300 mW excitation energy, concentrations of RDX and PETN can be detected and reconstructed in the case of thin Semtex smears, but further work is needed to push detection limits of areal dosages to the ~1 μg/cm2 level. We describe the performance of several probe/spectrograph combinations and show preliminary data for particle detection, calibration and detection linearity for mixed compounds, and so forth.

Optimization of Sample Preparation processes of Bone Material for Raman Spectroscopy.

Science.gov (United States)

Chikhani, Madelen; Wuhrer, Richard; Green, Hayley

2018-03-30

Raman spectroscopy has recently been investigated for use in the calculation of postmortem interval from skeletal material. The fluorescence generated by samples, which affects the interpretation of Raman data, is a major limitation. This study compares the effectiveness of two sample preparation techniques, chemical bleaching and scraping, in the reduction of fluorescence from bone samples during testing with Raman spectroscopy. Visual assessment of Raman spectra obtained at 1064 nm excitation following the preparation protocols indicates an overall reduction in fluorescence. Results demonstrate that scraping is more effective at resolving fluorescence than chemical bleaching. The scraping of skeletonized remains prior to Raman analysis is a less destructive method and allows for the preservation of a bone sample in a state closest to its original form, which is beneficial in forensic investigations. It is recommended that bone scraping supersedes chemical bleaching as the preferred method for sample preparation prior to Raman spectroscopy. © 2018 American Academy of Forensic Sciences.

Geometrical relaxation of excitations in one-dimensional conjugated polymers; Giichijigen kyoeki kobunshi reiki jotai no shusa kozo kanwa

Energy Technology Data Exchange (ETDEWEB)

Yoshizawa, M. [Tohoku University, Sendai (Japan). Faculty of Engineering

1995-12-15

Large ultrafast optical nonlinearities in conjugated polymers have attracted much attention because of possible applications to nonlinear optical devices. One-dimensional systems such as conjugated polymers have localized excited states with geometrical relaxation. In this study, photoexcited states in polydiacetylene has been investigated by femtosecond Raman gain spectroscopy with 300-fs resolution. A new photoinduced Raman peak with lifetime of 1.5 ps has been observed at 1200cm{sup -1} for the first time. This peak indicates acetylene-like structure of the main chain relaxes to butatriene-like structure due to the formation of self-trapped exciting with the geometrical relaxation. The formation and decay kinetics of the Raman signals is consistent with the relaxation processes of exciting observed by femtosecond absorption spectroscopy. 8 refs., 5 figs.

Raman Spectroscopy of Two-Dimensional Bi2TexSe3 − x Platelets Produced by Solvothermal Method

Directory of Open Access Journals (Sweden)

Jian Yuan

2015-08-01

Full Text Available In this paper, we report a facile solvothermal method to produce both binary and ternary compounds of bismuth chalcogenides in the form of Bi2TexSe3 − x. The crystal morphology in terms of geometry and thickness as well as the stoichiometric ratio can be well controlled, which offers the opportunities to systematically investigate the relationship between microstructure and phonon scattering by Raman spectroscopy. Raman spectra of four compounds, i.e., Bi2Se3, Bi2Se2Te, Bi2SeTe2 and Bi2Te3, were collected at four different excitation photon energies (2.54, 2.41, 1.96, and 1.58 eV. It is found that the vibrational modes are shifted to higher frequency with more Se incorporation towards the replacement of Te. The dependence of Raman vibrational modes on excitation photon energy was investigated. As the excitation photon energy increases, three Raman vibrational modes (A1g1, Eg2 and A1g2 of the as-produced compounds move to low frequency. Three Infrared-active (IR-active modes were observed in thin topological insulators (TIs crystals.

High resolution resonant Raman scattering in InP and GaAs

International Nuclear Information System (INIS)

Kernohan, E.T.M.

1996-04-01

Previous studies of III-V semiconductors using resonant Raman scattering have concentrated on measuring the variations in scattering intensity under different excitation conditions. The shape of the Raman line also contains important information, but this has usually been lost because the low signal strengths mean that resolution has been sacrificed for sensitivity. It might therefore be expected that further insights into the processes involved in Raman scattering could be obtained by using high resolution methods. In this thesis I have measured single- and multiple- phonon scattering from bulk GaAs and InP with a spectral resolution better than the intrinsic widths of the Raman lines. For scattering in the region of one longitudinal optic (LO) phonon energy, it is found that in InP the scattering in the allowed and forbidden configurations occur at different Raman shifts, above and below the zone-centre phonon energy respectively. These shifts are used to determine the scattering processes involved, and how they differ between InP and GaAs. The lineshapes obtained in multiple-phonon scattering are found to depend strongly on the excitation energy used, providing evidence for the presence of intermediate resonances. The measured spectra are used to provide information about the phonon dispersion of InP, whose dispersion it is difficult to measure in any other way, and the first evidence is found for an upward dispersion of the LO mode. Raman lineshapes are measured for InP in a magnetic field. The field alters the electronic bandstructure, leading to a series of strong resonances in the Raman efficiency due to interband magneto-optical transitions between Landau levels. This allows multiphonon processes up to sixth-order to be investigated. (author)

Raman Tweezers as a Diagnostic Tool of Hemoglobin-Related Blood Disorders

Directory of Open Access Journals (Sweden)

Giulia Rusciano

2008-12-01

Full Text Available This review presents the development of a Raman Tweezers system for detecting hemoglobin-related blood disorders at a single cell level. The study demonstrates that the molecular fingerprint insight provided by Raman analysis holds great promise for distinguishing between healthy and diseased cells in the field of biomedicine. Herein a Raman Tweezers system has been applied to investigate the effects of thalassemia, a blood disease quite diffuse in the Mediterranean Sea region. By resonant excitation of hemoglobin Raman bands, we examined the oxygenation capability of normal, alpha- and beta-thalassemic erythrocytes. A reduction of this fundamental red blood cell function, particularly severe for beta-thalassemia, has been found. Raman spectroscopy was also used to draw hemoglobin distribution inside single erythrocytes; the results confirmed the characteristic anomaly (target shape, occurring in thalassemia and some other blood disorders. The success of resonance Raman spectroscopy for thalassemia detection reported in this review provide an interesting starting point to explore the application of a Raman Tweezers system in the analysis of several blood disorders.

Comparative study of the two-phonon Raman bands of silicene and graphene

International Nuclear Information System (INIS)

Popov, Valentin N; Lambin, Philippe

2016-01-01

We present a computational study of the two-phonon Raman spectra of silicene and graphene within a density-functional non-orthogonal tight-binding model. Due to the presence of linear bands close to the Fermi energy in the electronic structure of both structures, the Raman scattering by phonons is resonant. We find that the Raman spectra exhibit a crossover behavior for laser excitation close to the π-plasmon energy. This phenomenon is explained by the disappearance of certain paths for resonant Raman scattering and the appearance of other paths beyond this energy. Besides that, the electronic joint density of states (DOS) is divergent at this energy, which is reflected on the behavior of the Raman bands of the two structures in a qualitatively different way. Additionally, a number of Raman bands, originating from divergent phonon DOS at the M point and at points, inside the Brillouin zone, is also predicted. The calculated spectra for graphene are in excellent agreement with available experimental data. The obtained Raman bands can be used for structural characterization of silicene and graphene samples by Raman spectroscopy. (paper)

Double-wall carbon nanotubes doped with different Br2 doping levels: a resonance Raman study.

Science.gov (United States)

do Nascimento, Gustavo M; Hou, Taige; Kim, Yoong Ahm; Muramatsu, Hiroyuki; Hayashi, Takuya; Endo, Morinobu; Akuzawa, Noboru; Dresselhaus, Mildred S

2008-12-01

This report focuses on the effects of different Br2 doping levels on the radial breathing modes of "double-wall carbon nanotube (DWNT) buckypaper". The resonance Raman profile of the Br2 bands are shown for different DWNT configurations with different Br2 doping levels. Near the maximum intensity of the resonance Raman profile, mainly the Br2 molecules adsorbed on the DWNT surface contribute strongly to the observed omega(Br-Br) Raman signal.

A quarter century of stimulated Raman scattering

International Nuclear Information System (INIS)

Bloembergen, N.

1987-01-01

To round out a quarter century of SRS the timing of this writing (1986) requires a look ahead of only one year into the future. The proceedings of the 10th International Conference on Raman Spectroscopy present a picture of current activity. Further progress will be made in time-resolved spectroscopy with subpicosecond resolution, in the study of hyper-Raman and other higher order effects with CARS, in extension of resonant Raman excitation in the UV region of spectrum, and in the development of Raman laser sources. During past few years extensive theoretical investigations have been made for four-wave light mixing in the case of one or more very strong light beams. The perturbation approach for those fields ceases to be valid. If only one light field is strong, the usual approach is to make a transformation to a rotating coordinate system so that the strong Hamiltonian for this light field becomes time-independent. Very recently these techniques have been extended to the case of two or more strong fields. CARS-type experiments with strong beams are likely to receive more attention. Extrapolation of the current activities instills confidence in the vitality of stimulated Raman scattering for the foreseeable future

Raman Spectroscopy of Single Nanoparticles in a Double-Nanohole Optical Tweezer System

OpenAIRE

Jones, Steven; Balushi, Ahmed A. Al; Gordon, Reuven

2015-01-01

A double nanohole in a metal film was used to trap nanoparticles (20 nm diameter) and simultaneously record their Raman spectrum using the trapping laser as the excitation source. This allowed for the identification of characteristic Stokes lines for titania and polystyrene nanoparticles, showing the capability for material identification of nanoparticles once trapped. Increased Raman signal is observed for the trapping of multiple nanoparticles. This system combines the benefits of nanoparti...

Synthesis and Raman analysis of SnS nanoparticles synthesized by PVP assisted polyol method

Energy Technology Data Exchange (ETDEWEB)

Baby, Benjamin Hudson; Mohan, D. Bharathi, E-mail: d.bharathimohan@gmail.com [Department of Physics, School of Physical, Chemical and Applied Sciences, Pondicherry University, R.V. Nagar, Kalapet, Puducherry-605014 (India)

2015-06-24

SnS film was prepared by a simple drop casting method after synthesizing SnS nanoparticles by using PVP assisted polyol method. Confocal Raman study was carried out for the as deposited and annealed (150, 300 and 400 °C) films at two different excitation wavelengths 514 and 785 nm. At the excitation wavelength of 514 nm, the Raman modes showed for a mixed phase of SnS and SnS{sub 2} up to 150 °C and then only a pure SnS phase was observed up to 400 °C due to the dissociation of SnS{sub 2} in to SnS by releasing S. The increase in intensity of Raman (A{sub g} and B{sub 3g}) as well as IR (B{sub 3u}) active modes of SnS are observed with increasing annealing temperature at excitation wavelength 785 nm due to the increased crystallinity and inactiveness of SnS{sub 2} modes. X-ray diffraction confirming the formation of a single phase of SnS while the greater homogeneity in both size and shape of SnS nanoparticles were confirmed through surface morphology from SEM.

Observation of excited state charge transfer with fs/ps-CARS

International Nuclear Information System (INIS)

Blom, Alex Jason

2009-01-01

Excited state charge transfer processes are studied using the fs/ps-CARS probe technique. This probe allows for multiplexed detection of Raman active vibrational modes. Systems studied include Michler's Ketone, Coumarin 120, 4-dimethylamino-4(prime)-nitrostilbene, and several others. The vibrational spectrum of the para di-substituted benzophenone Michler's Ketone in the first excited singlet state is studied for the first time. It is found that there are several vibrational modes indicative of structural changes of the excited molecule. A combined experimental and theoretical approach is used to study the simplest 7-amino-4-methylcoumarin, Coumarin 120. Vibrations observed in FTIR and spontaneous Raman spectra are assigned using density functional calculations and a continuum solvation model is used to predict how observed modes are affected upon inclusion of a solvent. The low frequency modes of the excited state charge transfer species 4-dimethylamino-4(prime)-nitrostilbene are studied in acetonitrile. Results are compared to previous work on this molecule in the fingerprint region. Finally, several partially completed projects and their implications are discussed. These include the two photon absorption of Coumarin 120, nanoconfinement in cyclodextrin cavities and sensitization of titania nanoparticles

Observation of excited state charge transfer with fs/ps-CARS

Energy Technology Data Exchange (ETDEWEB)

Blom, Alex Jason [Iowa State Univ., Ames, IA (United States)

2009-01-01

Excited state charge transfer processes are studied using the fs/ps-CARS probe technique. This probe allows for multiplexed detection of Raman active vibrational modes. Systems studied include Michler's Ketone, Coumarin 120, 4-dimethylamino-4'-nitrostilbene, and several others. The vibrational spectrum of the para di-substituted benzophenone Michler's Ketone in the first excited singlet state is studied for the first time. It is found that there are several vibrational modes indicative of structural changes of the excited molecule. A combined experimental and theoretical approach is used to study the simplest 7-amino-4-methylcoumarin, Coumarin 120. Vibrations observed in FTIR and spontaneous Raman spectra are assigned using density functional calculations and a continuum solvation model is used to predict how observed modes are affected upon inclusion of a solvent. The low frequency modes of the excited state charge transfer species 4-dimethylamino-4{prime}-nitrostilbene are studied in acetonitrile. Results are compared to previous work on this molecule in the fingerprint region. Finally, several partially completed projects and their implications are discussed. These include the two photon absorption of Coumarin 120, nanoconfinement in cyclodextrin cavities and sensitization of titania nanoparticles.

Using Deep UV Raman Spectroscopy to Identify In Situ Microbial Activity

Science.gov (United States)

Sapers, H. M.; Wanger, G.; Amend, J.; Orphan, V. J.; Bhartia, R.

2017-12-01

Microbial communities living in close association with lithic substrates play a critical role in biogeochemical cycles. Understanding the interactions between microorganisms and their abiotic substrates requires knowledge of microbial activity. Identifying active cells adhered to complex environmental substrates, especially in low biomass systems, remains a challenge. Stable isotope probing (SIP) provides a means to trace microbial activity in environmental systems. Active members of the community take up labeled substrates and incorporate the labels into biomolecules that can be detected through downstream analyses. Here we show for the first time that Deep UV (248 nm) Raman spectroscopy can differentiate microbial cells labeled with stable isotopes. Previous studies have used Raman spectroscopy with a 532 nm source to identify active bacterial cells by measuring a Raman shift between peaks corresponding to amino acids incorporating 13C compared to controls. However, excitation at 532 nm precludes detection on complex substrates due to high autofluorescence of native minerals. Excitation in the DUV range offers non-destructive imaging on mineral surfaces - retaining critical contextual information. We prepared cultures of E. coli grown in 50 atom% 13C glucose spotted onto Al wafers to test the ability of DUV Raman spectroscopy to differentiate labeled and unlabeled cells. For the first time, we are able to demonstrate a distinct and repeatable shift between cells grown in labeled media and unlabeled media when imaged on Al wafers with DUV Raman spectroscopy. The Raman spectra are dominated by the characteristic Raman bands of guanine. The dominant marker peak for guanine attributed to N7-C8 and C8-N9 ring stretching and C8-H in-plane bending, is visible at 1480 cm-1 in the unlabeled cells and is blue-shifted by 20 wavenumbers to 1461 cm-1 in the labeled cells. The ability of DUV Raman to effectively identify regions containing cells that have incorporated isotopic

Circumventing substrate interference in the Raman spectroscopic identification of blood stains.

Science.gov (United States)

McLaughlin, Gregory; Sikirzhytski, Vitali; Lednev, Igor K

2013-09-10

Raman spectroscopy has demonstrated remarkable capabilities in identifying blood in controlled laboratory conditions. However, substrate interference presents a significant challenge toward characterizing body fluid traces with Raman spectroscopy at a crime scene. Here, several possible solutions are explored, including the selection of laser excitation, isolating the signal of blood using spectral subtraction and using a favorable substrate for collection which minimizes interference. Simulated blood stain evidence was prepared and analyzed using a Raman microscope with variable laser capabilities. It is shown that the best approach for detecting blood depends on the nature of the substrate and the type of interference encountered. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Shape-dependent surface-enhanced Raman scattering in gold–Raman-probe–silica sandwiched nanoparticles for biocompatible applications

International Nuclear Information System (INIS)

Li Ming; Cushing, Scott K; Lankford, Jessica; Wu, Nianqiang; Zhang Jianming; Ma Dongling; Aguilar, Zoraida P

2012-01-01

To meet the requirement of Raman probes (labels) for biocompatible applications, a synthetic approach has been developed to sandwich the Raman-probe (malachite green isothiocyanate, MGITC) molecules between the gold core and the silica shell in gold–SiO 2 composite nanoparticles. The gold–MGITC–SiO 2 sandwiched structure not only prevents the Raman probe from leaking out but also improves the solubility of the nanoparticles in organic solvents and in aqueous solutions even with high ionic strength. To amplify the Raman signal, three types of core, gold nanospheres, nanorods and nanostars, have been chosen as the substrates of the Raman probe. The effect of the core shape on the surface-enhanced Raman scattering (SERS) has been investigated. The colloidal nanostars showed the highest SERS enhancement factor while the nanospheres possessed the lowest SERS activity under excitation with 532 and 785 nm lasers. Three-dimensional finite-difference time domain (FDTD) simulation showed significant differences in the local electromagnetic field distributions surrounding the nanospheres, nanorods, and nanostars, which were induced by the localized surface plasmon resonance (LSPR). The electromagnetic field was enhanced remarkably around the two ends of the nanorods and around the sharp tips of the nanostars. This local electromagnetic enhancement made the dominant contribution to the SERS enhancement. Both the experiments and the simulation revealed the order nanostars > nanorods > nanospheres in terms of the enhancement factor. Finally, the biological application of the nanostar–MGITC–SiO 2 nanoparticles has been demonstrated in the monitoring of DNA hybridization. In short, the gold–MGITC–SiO 2 sandwiched nanoparticles can be used as a Raman probe that features high sensitivity, good water solubility and stability, low-background fluorescence, and the absence of photobleaching for future biological applications. (paper)

Discriminant analysis of Raman spectra for body fluid identification for forensic purposes.

Science.gov (United States)

Sikirzhytski, Vitali; Virkler, Kelly; Lednev, Igor K

2010-01-01

Detection and identification of blood, semen and saliva stains, the most common body fluids encountered at a crime scene, are very important aspects of forensic science today. This study targets the development of a nondestructive, confirmatory method for body fluid identification based on Raman spectroscopy coupled with advanced statistical analysis. Dry traces of blood, semen and saliva obtained from multiple donors were probed using a confocal Raman microscope with a 785-nm excitation wavelength under controlled laboratory conditions. Results demonstrated the capability of Raman spectroscopy to identify an unknown substance to be semen, blood or saliva with high confidence.

Discriminant Analysis of Raman Spectra for Body Fluid Identification for Forensic Purposes

Directory of Open Access Journals (Sweden)

Vitali Sikirzhytski

2010-03-01

Full Text Available Detection and identification of blood, semen and saliva stains, the most common body fluids encountered at a crime scene, are very important aspects of forensic science today. This study targets the development of a nondestructive, confirmatory method for body fluid identification based on Raman spectroscopy coupled with advanced statistical analysis. Dry traces of blood, semen and saliva obtained from multiple donors were probed using a confocal Raman microscope with a 785-nm excitation wavelength under controlled laboratory conditions. Results demonstrated the capability of Raman spectroscopy to identify an unknown substance to be semen, blood or saliva with high confidence.

Cell design and image analysis for in situ Raman mapping of inhomogeneous state-of-charge profiles in lithium-ion batteries

Science.gov (United States)

Fang, Shuyu; Yan, Min; Hamers, Robert J.

2017-06-01

The study of inhomogeneous battery failure processes requires proper tools with high spatial resolving power. Here we describe a simple way to adapt industry-standard coin cells to enable in situ Raman mapping of lithium-ion battery materials. We describe the important cell design parameters and validate that the design achieves a uniform potential distribution within the region probed by Raman. We further validate that the cell yields electrical performance characteristics equivalent to a standard, non-modified coin cell. Using this cell, we probe the local charging profiles of LiNi0.5Mn0.3Co0.2O2 ("NMC") particles during cycling and demonstrate the ability to achieve spatial maps of the Raman spectra. In order to reduce the effects of local topography, we further analyze these data by numerically extracting the local frequency of the A1g vibrational mode, which is sensitive to the local extent of lithiation, and producing spatial maps of the local frequency of the A1g mode. This work demonstrates a way to collect and analyze high quality in situ spectra with an easy-to-implement cell design that can be applied to a wide range of electrode materials.

Raman investigation of molybdenum disulfide with different polytypes

Science.gov (United States)

Lee, Jae-Ung; Kim, Kangwon; Han, Songhee; Ryu, Gyeong Hee; Lee, Zonghoon; Cheong, Hyeonsik

The Raman spectra of molybdenum disulfide (MoS2) with different polytypes are investigated. Although 2H-MoS2 is most common in nature, the 3R phase can exist due to a small difference in the formation energy. However, only a few studies are reported for the 3R phase, and most studies have focused on the 2H phase. We found the 2H, 3R and mixed phases of exfoliated few-layer MoS2 from natural molybdenite crystals. The crystal structures of 2H- and 3R-MoS2 are confirmed by the HR-TEM measurements. By using 3 different excitation energies, we compared the Raman spectra of different polytypes in detail. We show that the Raman spectroscopy can be used to identify not only the number of layers but also the polytypes of MoS2.

Relativistic treatment of Raman free-electro laser in beam frame

International Nuclear Information System (INIS)

Korbacheh, A.; Maraghechi, B.; Aghahosseni, H.

2004-01-01

A relativistic theory for Raman backscattering in the beam frame of electrons is used to find the growth rate of free- electron laser in Raman regime. The electromagnetic effects of the space-charge wave are taken into account by using the electrostatic approximation in the beam frame. The wiggler effects on the linear dispersion relations of the space- charge wave and radiation are included in the analysis. A numerical computation is conducted to compare the growth rate of the excited waves with nonrelativistic treatment

Mapping residual stress fields from Vickers hardness indents using Raman microprobe spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Sparks, R.G.; Enloe, W.S.; Paesler, M.A.

1988-12-01

Micro-Raman spectroscopy is used to map the residual stress fields in the vicinity of Vickers hardness indents. Both 514.5 and 488.0 nm, light is used to excite the effect and the resulting shifted and broadened Raman peaks are analyzed using computer deconvolution. Half-wave plates are used to vary the orientation of the incident later light`s polarization state with respect to crystal orientation. The Raman scattered light is then analyzed for polarization dependences which are indicative of the various components of the Raman scattering tensor. Such studies can yield valuable information about the orientation of stress components in a well known stress field. The results can then be applied to the determination of stress components in machined semiconductor materials.

Quantitative determination of the human breast milk macronutrients by near-infrared Raman spectroscopy

Science.gov (United States)

Motta, Edlene d. C. M.; Zângaro, Renato A.; Silveira, Landulfo, Jr.

2012-03-01

This work proposes the evaluation of the macronutrient constitution of human breast milk based on the spectral information provided by near-infrared Raman spectroscopy. Human breast milk (5 mL) from a subject was collected during the first two weeks of breastfeeding and stocked in -20°C freezer. Raman spectra were measured using a Raman spectrometer (830 nm excitation) coupled to a fiber based Raman probe. Spectra of human milk were dominated by bands of proteins, lipids and carbohydrates in the 600-1800 cm-1 spectral region. Raman spectroscopy revealed differences in the biochemical constitution of human milk depending on the time of breastfeeding startup. This technique could be employed to develop a classification routine for the milk in Human Milk Banking (HMB) depending on the nutritional facts.

Low-energy d-d excitations in MnO studied by resonant x-ray fluorescence spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Butorin, S.M.; Guo, J.; Magnuson, M. [Uppsala Univ. (Sweden)] [and others

1997-04-01

Resonant soft X-ray emission spectroscopy has been demonstrated to possess interesting abilities for studies of electronic structure in various systems, such as symmetry probing, alignment and polarization dependence, sensitivity to channel interference, etc. In the present abstract the authors focus on the feasibility of resonant soft X-ray emission to probe low energy excitations by means of resonant electronic X-ray Raman scattering. Resonant X-ray emission can be regarded as an inelastic scattering process where a system in the ground state is transferred to a low excited state via a virtual core excitation. The energy closeness to a core excitation of the exciting radiation enhances the (generally) low probability for inelastic scattering at these wavelengths. Therefore soft X-ray emission spectroscopy (in resonant electronic Raman mode) can be used to study low energy d-d excitations in transition metal systems. The involvement of the intermediate core state allows one to use the selection rules of X-ray emission, and the appearance of the elastically scattered line in the spectra provides the reference to the ground state.

Low-energy d-d excitations in MnO studied by resonant x-ray fluorescence spectroscopy

International Nuclear Information System (INIS)

Butorin, S.M.; Guo, J.; Magnuson, M.

1997-01-01

Resonant soft X-ray emission spectroscopy has been demonstrated to possess interesting abilities for studies of electronic structure in various systems, such as symmetry probing, alignment and polarization dependence, sensitivity to channel interference, etc. In the present abstract the authors focus on the feasibility of resonant soft X-ray emission to probe low energy excitations by means of resonant electronic X-ray Raman scattering. Resonant X-ray emission can be regarded as an inelastic scattering process where a system in the ground state is transferred to a low excited state via a virtual core excitation. The energy closeness to a core excitation of the exciting radiation enhances the (generally) low probability for inelastic scattering at these wavelengths. Therefore soft X-ray emission spectroscopy (in resonant electronic Raman mode) can be used to study low energy d-d excitations in transition metal systems. The involvement of the intermediate core state allows one to use the selection rules of X-ray emission, and the appearance of the elastically scattered line in the spectra provides the reference to the ground state

Study of hot carrier relaxation in quantum wells by subpicosecond Raman scattering

International Nuclear Information System (INIS)

Kim, Dai-sik; Yu, P.Y.

1990-03-01

Relaxation of hot carriers excited by subpicosecond laser pulses has been studied by Raman scattering in GaAs/AlAs multiple quantum wells with well widths varying between 100 and 1000 Angstrom. The hot phonon population observed by Raman scattering is found to decrease with the well width despite the fact that the hot electron temperature remains constant. The results are explained in terms of confinement of both electrons and optical phonons in quantum wells

Discriminant Analysis of Raman Spectra for Body Fluid Identification for Forensic Purposes

OpenAIRE

Sikirzhytski, Vitali; Virkler, Kelly; Lednev, Igor K.

2010-01-01

Detection and identification of blood, semen and saliva stains, the most common body fluids encountered at a crime scene, are very important aspects of forensic science today. This study targets the development of a nondestructive, confirmatory method for body fluid identification based on Raman spectroscopy coupled with advanced statistical analysis. Dry traces of blood, semen and saliva obtained from multiple donors were probed using a confocal Raman microscope with a 785-nm excitation wave...

Analysis of root surface properties by fluorescence/Raman intensity ratio.

Science.gov (United States)

Nakamura, Shino; Ando, Masahiro; Hamaguchi, Hiro-O; Yamamoto, Matsuo

2017-11-01

The aim of this study is to evaluate the existence of residual calculus on root surfaces by determining the fluorescence/Raman intensity ratio. Thirty-two extracted human teeth, partially covered with calculus on the root surface, were evaluated by using a portable Raman spectrophotometer, and a 785-nm, 100-mW laser was applied for fluorescence/Raman excitation. The collected spectra were normalized to the hydroxyapatite Raman band intensity at 960 cm -1 . Raman spectra were recorded from the same point after changing the focal distance of the laser and the target radiating angle. In seven teeth, the condition of calculus, cementum, and dentin were evaluated. In 25 teeth, we determined the fluorescence/Raman intensity ratio following three strokes of debridement. Raman spectra collected from the dentin, cementum, and calculus were different. After normalization, spectra values were constant. The fluorescence/Raman intensity ratio of calculus region showed significant differences compared to the cementum and dentin (p Raman intensity ratio decreased with calculus debridement. For this analysis, the delta value was defined as the difference between the values before and after three strokes, with the final 2 delta values close to zero, indicating a gradual asymptotic curve and the change in intensity ratio approximating that of individual constants. Fluorescence/Raman intensity ratio was effectively used to cancel the angle- and distance-dependent fluctuations of fluorescence collection efficiency during measurement. Changes in the fluorescence/Raman intensity ratio near zero suggested that cementum or dentin was exposed, and calculus removed.

Raman Imaging of Plant Cell Walls in Sections of Cucumis sativus.

Science.gov (United States)

Zeise, Ingrid; Heiner, Zsuzsanna; Holz, Sabine; Joester, Maike; Büttner, Carmen; Kneipp, Janina

2018-01-25

Raman microspectra combine information on chemical composition of plant tissues with spatial information. The contributions from the building blocks of the cell walls in the Raman spectra of plant tissues can vary in the microscopic sub-structures of the tissue. Here, we discuss the analysis of 55 Raman maps of root, stem, and leaf tissues of Cucumis sativus , using different spectral contributions from cellulose and lignin in both univariate and multivariate imaging methods. Imaging based on hierarchical cluster analysis (HCA) and principal component analysis (PCA) indicates different substructures in the xylem cell walls of the different tissues. Using specific signals from the cell wall spectra, analysis of the whole set of different tissue sections based on the Raman images reveals differences in xylem tissue morphology. Due to the specifics of excitation of the Raman spectra in the visible wavelength range (532 nm), which is, e.g., in resonance with carotenoid species, effects of photobleaching and the possibility of exploiting depletion difference spectra for molecular characterization in Raman imaging of plants are discussed. The reported results provide both, specific information on the molecular composition of cucumber tissue Raman spectra, and general directions for future imaging studies in plant tissues.

In situ TEM Raman spectroscopy and laser-based materials modification

Energy Technology Data Exchange (ETDEWEB)

Allen, F.I., E-mail: fiallen@lbl.gov [Department of Materials Science and Engineering, University of California, Berkeley, CA 94720 (United States); National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Kim, E. [Department of Mechanical Engineering, University of California, Berkeley, CA 94720 (United States); Andresen, N.C. [Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Grigoropoulos, C.P. [Department of Mechanical Engineering, University of California, Berkeley, CA 94720 (United States); Minor, A.M., E-mail: aminor@lbl.gov [Department of Materials Science and Engineering, University of California, Berkeley, CA 94720 (United States); National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

2017-07-15

We present a modular assembly that enables both in situ Raman spectroscopy and laser-based materials processing to be performed in a transmission electron microscope. The system comprises a lensed Raman probe mounted inside the microscope column in the specimen plane and a custom specimen holder with a vacuum feedthrough for a tapered optical fiber. The Raman probe incorporates both excitation and collection optics, and localized laser processing is performed using pulsed laser light delivered to the specimen via the tapered optical fiber. Precise positioning of the fiber is achieved using a nanomanipulation stage in combination with simultaneous electron-beam imaging of the tip-to-sample distance. Materials modification is monitored in real time by transmission electron microscopy. First results obtained using the assembly are presented for in situ pulsed laser ablation of MoS{sub 2} combined with Raman spectroscopy, complimented by electron-beam diffraction and electron energy-loss spectroscopy. - Highlights: • Raman spectroscopy and laser-based materials processing in a TEM are demonstrated. • A lensed Raman probe is mounted in the sample chamber for close approach. • Localized laser processing is achieved using a tapered optical fiber. • Raman spectroscopy and pulsed laser ablation of MoS{sub 2} are performed in situ.

In situ TEM Raman spectroscopy and laser-based materials modification

International Nuclear Information System (INIS)

Allen, F.I.; Kim, E.; Andresen, N.C.; Grigoropoulos, C.P.; Minor, A.M.

2017-01-01

We present a modular assembly that enables both in situ Raman spectroscopy and laser-based materials processing to be performed in a transmission electron microscope. The system comprises a lensed Raman probe mounted inside the microscope column in the specimen plane and a custom specimen holder with a vacuum feedthrough for a tapered optical fiber. The Raman probe incorporates both excitation and collection optics, and localized laser processing is performed using pulsed laser light delivered to the specimen via the tapered optical fiber. Precise positioning of the fiber is achieved using a nanomanipulation stage in combination with simultaneous electron-beam imaging of the tip-to-sample distance. Materials modification is monitored in real time by transmission electron microscopy. First results obtained using the assembly are presented for in situ pulsed laser ablation of MoS_2 combined with Raman spectroscopy, complimented by electron-beam diffraction and electron energy-loss spectroscopy. - Highlights: • Raman spectroscopy and laser-based materials processing in a TEM are demonstrated. • A lensed Raman probe is mounted in the sample chamber for close approach. • Localized laser processing is achieved using a tapered optical fiber. • Raman spectroscopy and pulsed laser ablation of MoS_2 are performed in situ.

Fingerprints of quantum spin ice in Raman scattering

Science.gov (United States)

Perkins, Natalia

Quantum spin liquids (QSLs) emerging in frustrated magnetic systems have been a fascinating and challenging subject in modern condensed matter physics for over four decades. In these systems the conventional ordering is suppressed and, instead, unusual behaviors strongly dependent on the topology of the system are observed. The difficulty in the experimental observation of QSLs comes from the fact that unlike the states with broken symmetry, the topological order characteristic of cannot be captured by a local order parameter and thus cannot be detected by local measurements. Identifying QSLs therefore requires reconsideration of experimental probes to find ones sensitive to features characteristic of topological order. The fractionalization of excitations associated with this order can offer signatures that can be probed by conventional methods such as inelastic neutron scattering, Raman or Resonant X-ray scattering experiments. In my talk I will discuss the possibility to use Raman scattering to probe the excitations of Quantum Spin Ice, a model which has long been believed to host a U(1) spin liquid ground state. NSF DMR-1511768.

Progress report of FY 1999 activities: The application of Kalman filtering to derive water vapor profiles from combined ground-based sensors: Raman lidar, microwave radiometers, GPS, and radiosondes

International Nuclear Information System (INIS)

Edgeworth R. Westwater; Yong Han

1999-01-01

Previously, the proposers have delivered to ARM a documented algorithm, that is now applied operationally, and which derives water vapor profiles from combined remote sensor measurements of water vapor radiometers, cloud-base ceilometers, and radio acoustic sounding systems (RASS). With the expanded deployment of a Raman lidar at the CART Central Facility, high quality, high vertical-resolution, water vapor profiles will be provided during nighttime clear conditions, and during clear daytime conditions, to somewhat lower altitudes. The object of this effort is to use Kalman Filtering, previously applied to the combination of nighttime Raman lidar and microwave radiometer data, to derive high-quality water vapor profiles, during non-precipitating conditions, from data routinely available at the CART site. Input data to the algorithm would include: Raman lidar data, highly quality-controlled data of integrated moisture from microwave radiometers and GPS, RASS, and radiosondes. While analyzing data obtained during the Water Vapor Intensive Operating Period'97 at the SGP CART site in central Oklahoma, several questions arose about the calibration of the ARM microwave radiometers (MWR). A large portion of this years effort was a thorough analysis of the many factors that are important for the calibration of this instrument through the tip calibration method and the development of algorithms to correct this procedure. An open literature publication describing this analysis has been accepted

Enhancement of Raman scattering from monolayer graphene by photonic crystal nanocavities

Science.gov (United States)

Kimura, Issei; Yoshida, Masahiro; Sota, Masaki; Inoue, Taiki; Chiashi, Shohei; Maruyama, Shigeo; Kato, Yuichiro K.

Monolayer graphene is an atomically thin two-dimensional material that shows strong Raman scattering, while photonic crystal nanocavities with small mode volumes allow for efficient optical coupling at the nanoscale. Here we demonstrate resonant enhancement of graphene Raman G' band by coupling to photonic crystal cavity modes. Hexagonal-lattice photonic crystal L3 cavities are fabricated from silicon-on-insulator substrates. and monolayer graphene sheets grown by chemical vapor deposition are transferred onto the nanocavities. Excitation wavelength dependence of Raman spectra show that the Raman intensity is enhanced when the G' peak is in resonance with the cavity mode. By performing imaging measurements, we confirm that such an enhancement is only observed at the cavity position. Work supported by JSPS KAKENHI Grant Numbers JP16K13613, JP25107002 and MEXT (Photon Frontier Network Program, Nanotechnology Platform).

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

NARCIS (Netherlands)

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

2001-01-01

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

Cell Imaging by Spontaneous and Amplified Raman Spectroscopies

Directory of Open Access Journals (Sweden)

Giulia Rusciano

2017-01-01

Full Text Available Raman spectroscopy (RS is a powerful, noninvasive optical technique able to detect vibrational modes of chemical bonds. The high chemical specificity due to its fingerprinting character and the minimal requests for sample preparation have rendered it nowadays very popular in the analysis of biosystems for diagnostic purposes. In this paper, we first discuss the main advantages of spontaneous RS by describing the study of a single protozoan (Acanthamoeba, which plays an important role in a severe ophthalmological disease (Acanthamoeba keratitis. Later on, we point out that the weak signals that originated from Raman scattering do not allow probing optically thin samples, such as cellular membrane. Experimental approaches able to overcome this drawback are based on the use of metallic nanostructures, which lead to a huge amplification of the Raman yields thanks to the excitation of localized surface plasmon resonances. Surface-enhanced Raman scattering (SERS and tip-enhanced Raman scattering (TERS are examples of such innovative techniques, in which metallic nanostructures are assembled on a flat surface or on the tip of a scanning probe microscope, respectively. Herein, we provide a couple of examples (red blood cells and bacterial spores aimed at studying cell membranes with these techniques.

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

Energy Technology Data Exchange (ETDEWEB)

Tamma, Venkata Ananth [CaSTL Center, Department of Chemistry, University of California, Irvine, California 92697 (United States); Huang, Fei; Kumar Wickramasinghe, H., E-mail: hkwick@uci.edu [Department of Electrical Engineering and Computer Science, 142 Engineering Tower, University of California, Irvine, California 92697 (United States); Nowak, Derek [Molecular Vista, Inc., 6840 Via Del Oro, San Jose, California 95119 (United States)

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.

Double resonance Raman effects in InN nanowires

Energy Technology Data Exchange (ETDEWEB)

Domenech-Amador, N.; Cusco, R.; Artus, L. [Institut Jaume Almera, Consell Superior d' Investigacions Cientifiques (CSIC), Lluis Sole i Sabaris s.n., Barcelona, Catalonia (Spain); Calarco, R. [Institute of Bio- and Nanosystems, Research Center Juelich GmbH, Juelich (Germany); Paul-Drude-Institut fuer Festkoerperelektronik, Berlin (Germany); Yamaguchi, T.; Nanishi, Y. [Faculty of Science and Engineering, Ritsumeikan University, Noji-Higashi, Kusatsu, Shiga 525-8577 (Japan)

2012-04-15

We study the excitation wavelength dependence of the Raman spectra of InN nanowires. The E{sub 1}(LO) phonon mode, which is detected in backscattering configuration because of light entering through lateral faces, exhibits an upward frequency shift that can be explained by Martin's double resonance. The E{sub 1} (LO)/E{sub 2}{sup h} intensity ratio increases with the excitation wavelength more rapidly than the A{sub 1}(LO)/E{sub 2}{sup h} ratio measured in InN thin films. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Ultra violet resonance Raman spectroscopy in lignin analysis: determination of characteristic vibrations of p-hydroxyphenyl, guaiacyl, and syringyl lignin structures.

Science.gov (United States)

Saariaho, Anna-Maija; Jääskeläinen, Anna-Stiina; Nuopponen, Mari; Vuorinen, Tapani

2003-01-01

Raman spectroscopy of wood and lignin samples is preferably carried out in the near-infrared region because lignin produces an intense laser-induced fluorescence background at visible excitation wavelengths. However, excitation of aromatic and conjugated lignin structures with deep ultra violet (UV) light gives resonance-enhanced Raman signals while the overlapping fluorescence is eliminated. In this study, ultra violet resonance Raman (UVRR) spectroscopy was used to define characteristic vibration bands of model compounds of p-hydroxyphenyl, guaiacyl, and syringyl lignin structures at three excitation wavelengths (229, 244, and 257 nm). The intensities of each band, relative to the intensity of the aromatic vibration band at 1600 cm-1, were defined and the most suitable excitation wavelength was suggested for each structure. p-Hydroxyphenyl structures showed intensive characteristic bands at 1217-1214 and 1179-1167 cm-1 with excitation at 244 nm, whereas the bands of guaiacyl structures were more intensive with 257 nm excitation. Most intensive characteristic bands of guaiacyl structures were found at 1289-1279, 1187-1185, 1158-1155, and 791-704 cm-1. Syringyl structures had almost identical spectra with 244 and 257 nm excitations with characteristic bands at 1514-1506, 1333-1330, and 981-962 cm-1. The characteristic bands of the three structural units were also found from the compression wood, softwood, and hardwood samples, indicating that UVRR spectroscopy can be applied for the determination of chemical structures of lignin.

Capability of Raman lidar for monitoring the variation of atmospheric CO2 profile

International Nuclear Information System (INIS)

Zhao Peitao; Hu Shunxing; Su Jia; Cao Kaifa; Hu Huanling; Zhang Yinchao; Wang Lian; Zhao Yuefeng

2008-01-01

Lidar (Light detection and ranging) has special capabilities for remote sensing of many different behaviours of the atmosphere. One of the techniques which show a great deal of promise for several applications is Raman scattering. The detecting capability, including maximum operation range and minimum detectable gas concentration is one of the most significant parameters for lidar remote sensing of pollutants. In this paper, based on the new method for evaluating the capabilities of a Raman lidar system, we present an evaluation of detecting capability of Raman lidar for monitoring atmospheric CO 2 in Hefei. Numerical simulations about the influence of atmospheric conditions on lidar detecting capability were carried out, and a conclusion can be drawn that the maximum difference of the operation ranges caused by the weather conditions alone can reach about 0.4 to 0.5km with a measuring precision within 30ppmv. The range of minimum detectable concentration caused by the weather conditions alone can reach about 20 to 35 ppmv in vertical direction for 20000 shots at a distance of 1 km on the assumption that other parameters are kept constant. The other corresponding parameters under different conditions are also given. The capability of Raman lidar operated in vertical direction was found to be superior to that operated in horizontal direction. During practical measurement with the Raman lidar whose hardware components were fixed, aerosol scattering extinction effect would be a significant factor that influenced the capability of Raman lidar. This work may be a valuable reference for lidar system designing, measurement accuracy improving and data processing

Dual-wavelength external cavity laser device for fluorescence suppression in Raman spectroscopy

Science.gov (United States)

Zhang, Xuting; Cai, Zhijian; Wu, Jianhong

2017-10-01

Raman spectroscopy has been widely used in the detection of drugs, pesticides, explosives, food additives and environmental pollutants, for its characteristics of fast measurement, easy sample preparation, and molecular structure analyzing capability. However, fluorescence disturbance brings a big trouble to these applications, with strong fluorescence background covering up the weak Raman signals. Recently shifted excitation Raman difference spectroscopy (SERDS) not only can completely remove the fluorescence background, but also can be easily integrated into portable Raman spectrometers. Usually, SERDS uses two lasers with small wavelength gap to excite the sample, then acquires two spectra, and subtracts one to the other to get the difference spectrum, where the fluorescence background will be rejected. So, one key aspects of successfully applying SERDS method is to obtain a dual-wavelength laser source. In this paper, a dual-wavelength laser device design based on the principles of external cavity diode laser (ECDL) is proposed, which is low-cost and compact. In addition, it has good mechanical stability because of no moving parts. These features make it an ideal laser source for SERDS technique. The experiment results showed that the device can emit narrow-spectral-width lasers of two wavelengths, with the gap smaller than 2 nanometers. The laser power corresponding to each wavelength can be up to 100mW.

Wavelength Selection For Laser Raman Spectroscopy of Putative Martian Habitats and Biomolecules

Science.gov (United States)

Wynn-Williams, D. D.; Newton, E. M. G.; Edwards, H. G. M.

Pigments are key potential biomarkers for any former life on Mars because of the selective pressure of solar radiation on any biological system that could have evolved at its surface. We have found that the near -Infrared laser Raman spectrometer available to use was eminently suitable for diagnostic analysis of pigments because of their minimal autofluorescence at its 1064 nm excitation wav elength. However, we have now evaluated a diverse range of excitation wavelengths to confirm this choice, to ensure that we have the best technique to seek for pigments and their derivatives from any former surface life on Mars. The Raman is weak relative to fluorescence, which results in elevated baseline and concurrent swamping of Raman bands. We confirm the molecular information available from near-IR FT Raman spectra for two highly pigmented UV-tolerant epilithic Antarctic lichens (Acarospora chlorop hana and Caloplaca saxicola) from Victoria Land, a whole endolithic microbial community and endolithic cyanobacterium Chroococcidiopsis from within translucent sandstone of the Trans -Antarctic Mountains, and the free- living cyanobacterium Nostoc commune from Alexander Island, Antarctic Peninsula region. We also show that much of the information we require on biomolecules is not evident from lasers of shorter wavelengths. A miniature 1064 nm Raman spectrometer with an In-Ga-As detector sensitive to IR is being developed by Montana State University (now existing as a prototype) as the prime instrument for a proposed UK-led Mars rover mission (Vanguard). Preliminary spectra from this system confirm the suitability of the near-IR laser.

Transition from the radiationless resonant Raman scattering to the normal Auger decay in a charge transfer system

International Nuclear Information System (INIS)

Ohno, Masahide

2006-01-01

The transition from the radiationless resonant Raman scattering to the normal Auger decay in resonant Auger-electron spectroscopy (RAES) spectra of charge transfer (CT) systems is discussed by treating the relaxation and the core-hole decay of the excited core-hole state on the same footing by a many-body theory. When the resonantly excited electron remains at the excited atomic site during the core-hole decay, the RAES spectrum shows the characteristic feature of the resonant Auger-Raman effect, whereas when the excited electron has been transferred from the atomic site before the core-hole decays, the RAES spectrum shows the normal Auger decay. The present theory supports the interpretation of the variation with photon energy of the intensity ratio of the latter spectrum to the former one in the RAES spectrum by the Ar 2p → 4s resonance of Ar atoms adsorbed on Ru(0 0 1) surface reported by Keller et al. [C. Keller, M. Stichler, G. Comelli, F. Esch, S. Lizzit, D. Menzel, W. Wurth, Phys. Rev. B 57 (1998) 11951]. The transition from the radiationless resonant Raman scattering to the normal Auger decay in the RAES spectrum of CuO reported by Finazzi et al. [M. Finazzi, G. Ghiringhell, O. Tjernberg, Ph. Ohresser, N.B. Brookes, Phys. Rev. B 61 (2000) 4629] is discussed in terms of the relaxation of the resonantly excited core-hole state to the core-electron ionized main-line state by the hole-particle excitations. The merging of the resonant Raman-Auger-electron kinetic energy into the normal one about 2 eV above the absorption maximum in Cu 2 O reported by Finazzi et al. [M. Finazzi, G. Ghiringhell, O. Tjernberg, Ph. Ohresser, N.B. Brookes, Phys. Rev. B 61 (2000) 4629] is explained in terms of the change in the characteristics of the screening electron in the two-hole final state. The Ti L 23 -M 23 V RAES spectra of TiO 2 and TiO 2-x are also analyzed

Raman spectroscopy of single nanoparticles in a double-nanohole optical tweezer system

International Nuclear Information System (INIS)

Jones, Steven; Al Balushi, Ahmed A; Gordon, Reuven

2015-01-01

A double nanohole in a metal film was used to trap nanoparticles (20 nm diameter) and simultaneously record their Raman spectrum using the trapping laser as the excitation source. This allowed for the identification of characteristic Stokes lines for titania and polystyrene nanoparticles, showing the capability for material identification of nanoparticles once trapped. Increased Raman signal was observed for the trapping of multiple nanoparticles. This system combines the benefits of nanoparticle isolation and manipulation with unique identification. (fast track communication)

Using a portable Raman spectrometer to detect carotenoids of halophilic prokaryotes in synthetic inclusions in NaCl, KCl, and sulfates.

Science.gov (United States)

Jehlička, Jan; Culka, Adam; Mana, Lilly; Oren, Aharon

2018-05-03

Cell suspensions of the haloarchaea Halorubrum sodomense and Halobacterium salinarum and the extremely halophilic bacterium Salinibacter ruber (Bacteroidetes) in saturated solutions of chlorides and sulfates (NaCl, KCl, MgSO 4 ·7H 2 O, K 2 SO 4 , and (NH 4 )Al(SO 4 ) 2 ·12H 2 O) were left to evaporate to produce micrometric inclusions in laboratory-grown crystals. Raman spectra of these pinkish inclusions were obtained using a handheld Raman spectrometer with green excitation (532 nm). This portable instrument does not include any microscopic tool. Acceptable Raman spectra of carotenoids were obtained in the range of 200-4000 cm -1 . This detection achievement was related to the mode of illumination and collection of scattered light as well as due to resonance Raman enhancement of carotenoid signals under green excitation. The position of diagnostic Raman carotenoid bands corresponds well to those specific carotenoids produced by a given halophile. To our best knowledge, this is the first study of carotenoids included in the laboratory in crystalline chlorides and sulfates, using a miniature portable Raman spectrometer. Graphical abstract ᅟ.

Vibrational frequencies and dephasing times in excited electronic states by femtosecond time-resolved four-wave mixing

Science.gov (United States)

Joo, Taiha; Albrecht, A. C.

1993-06-01

Time-resolved degenerate four-wave mixing (TRDFWM) for an electronically resonant system in a phase-matching configuration that measures population decay is reported. Because the spectral width of input light exceeds the vibrational Bohr frequency of a strong Raman active mode, the vibrational coherence produces strong oscillations in the TRDFWM signal together with the usual population decay from the excited electronic state. The data are analyzed in terms of a four-level system: ground and excited electronic states each split by a vibrational quantum of a Raman active mode. Absolute frequencies and their dephasing times of the vibrational modes at ≈590 cm -1 are obtained for the excited as well as the ground electronic state. The vibrational dephasing rate in the excited electronic state is about an order of magnitude faster than that in the ground state, the origin of which is speculated upon.

High-resolution nonresonant x-ray Raman scattering study on rare earth phosphate nanoparticles

NARCIS (Netherlands)

Huotari, Simo; Suljoti, Edlira; Sahle, Christoph J.; Raedel, Stephanie; Monaco, Giulio; de Groot, Frank M. F.

2015-01-01

We report high-resolution x-ray Raman scattering studies of high-order multipole spectra of rare earth 4d -> 4f excitations (the N-4,N-5 absorption edge) in nanoparticles of the phosphates LaPO4, CePO4, PrPO4, and NdPO4. We also present corresponding data for La 5p -> 5d excitations (the O-2,O-3

Condensing Raman spectrum for single-cell phenotype analysis

KAUST Repository

Sun, Shiwei

2015-12-09

Background In recent years, high throughput and non-invasive Raman spectrometry technique has matured as an effective approach to identification of individual cells by species, even in complex, mixed populations. Raman profiling is an appealing optical microscopic method to achieve this. To fully utilize Raman proling for single-cell analysis, an extensive understanding of Raman spectra is necessary to answer questions such as which filtering methodologies are effective for pre-processing of Raman spectra, what strains can be distinguished by Raman spectra, and what features serve best as Raman-based biomarkers for single-cells, etc. Results In this work, we have proposed an approach called rDisc to discretize the original Raman spectrum into only a few (usually less than 20) representative peaks (Raman shifts). The approach has advantages in removing noises, and condensing the original spectrum. In particular, effective signal processing procedures were designed to eliminate noise, utilising wavelet transform denoising, baseline correction, and signal normalization. In the discretizing process, representative peaks were selected to signicantly decrease the Raman data size. More importantly, the selected peaks are chosen as suitable to serve as key biological markers to differentiate species and other cellular features. Additionally, the classication performance of discretized spectra was found to be comparable to full spectrum having more than 1000 Raman shifts. Overall, the discretized spectrum needs about 5storage space of a full spectrum and the processing speed is considerably faster. This makes rDisc clearly superior to other methods for single-cell classication.

Two-magnon Raman scattering in LiMnPO{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Calderon Filho, C.J. [Instituto de Física ”Gleb Wataghin”, UNICAMP, 13083-859, Campinas, São Paulo (Brazil); Gomes, P.F. [Instituto de Física ”Gleb Wataghin”, UNICAMP, 13083-859, Campinas, São Paulo (Brazil); Universidade Federal de Goiás, 75801-615, Jataí, Goiás (Brazil); García-Flores, A.F.; Barberis, G.E. [Instituto de Física ”Gleb Wataghin”, UNICAMP, 13083-859, Campinas, São Paulo (Brazil); Granado, E., E-mail: egranado@ifi.unicamp.br [Instituto de Física ”Gleb Wataghin”, UNICAMP, 13083-859, Campinas, São Paulo (Brazil)

2015-03-01

Two-magnon Raman scattering is observed in the orthophosphate LiMnPO{sub 4}, carrying quantitative information on the magnetic interactions between local Mn{sup 2+} moments. A simulated annealing fitting procedure of the Raman signal to theoretical curves derived from a magnetic Hamiltonian was carried out, taking exchange and anisotropy constants as free fitting parameters. Previously reported inelastic neutron scattering (INS) data [J. Li et al., Phys. Rev. B 79, 144410 (2009)] were also used in the fit. It is shown that the combined application of INS and Raman scattering data in the fit reduces the ambiguity of the determined set of exchange parameters with respect to fitting procedures using INS or Raman data independently. The temperature dependence of the Raman signal does not show a collapse of the two-magnon excitations at the long-range magnetic ordering temperature, T{sub N}=34K, supporting significant short-range spin correlations above T{sub N}. - Highlights: • A two-magnon Raman scattering signal was observed in the orthophosphate LiMnPO{sub 4}. • Calculations under the Fleury–Loudon were carried out to simulate the observed signal. • A combined fit using Raman and neutron data yields a robust set of magnetic parameters. • The nearest-neighbor interaction is largely dominant over the remaining terms. • This work is a step forward in combining techniques to obtain exchange constants.

Raman spectroscopic determination of norbixin and tartrazine in sugar.

Science.gov (United States)

Uhlemann, Ute; Strelau, Katharina K; Weber, Karina; Da Costa Filho, Paulo Augusto; Rösch, Petra; Popp, Jürgen

2012-08-01

In this paper, a method for the detection of norbixin and tartrazine in sugar by means of resonance Raman spectroscopy is presented. The extraction was done in four steps using methanol and the measurements were performed in aqueous solution. The excitation wavelength was 514 nm for norbixin and 488 nm for tartrazine samples. The characteristic resonance Raman signals of the dyes were fitted by different functions. Depending on the R² values of the different fits, each spectrum was classified as positive or negative response. A detection limit of 250 ng g⁻¹ for norbixin and 989 ng g⁻¹ for tartrazine in solid sugar samples could be reached by logistic regression.

Optical diagnosis of dengue virus infection in human blood serum using Raman spectroscopy

International Nuclear Information System (INIS)

Saleem, M; Bilal, M; Anwar, S; Rehman, A; Ahmed, M

2013-01-01

We present the optical diagnosis of dengue virus infection in human blood serum using Raman spectroscopy. Raman spectra were acquired from 18 blood serum samples using a laser at 532 nm as the excitation source. A multivariate regression model based on partial least-squares regression is developed that uses Raman spectra to predict dengue infection with leave-one-sample-out cross validation. The prediction of dengue infection by our model yields correlation coefficient r 2 values of 0.9998 between the predicted and reference clinical results. The model was tested for six unknown human blood sera and found to be 100% accurate in accordance with the clinical results. (letter)

Multifocus confocal Raman microspectroscopy for fast multimode vibrational imaging of living cells.

Science.gov (United States)

Okuno, Masanari; Hamaguchi, Hiro-o

2010-12-15

We have developed a multifocus confocal Raman microspectroscopic system for the fast multimode vibrational imaging of living cells. It consists of an inverted microscope equipped with a microlens array, a pinhole array, a fiber bundle, and a multichannel Raman spectrometer. Forty-eight Raman spectra from 48 foci under the microscope are simultaneously obtained by using multifocus excitation and image-compression techniques. The multifocus confocal configuration suppresses the background generated from the cover glass and the cell culturing medium so that high-contrast images are obtainable with a short accumulation time. The system enables us to obtain multimode (10 different vibrational modes) vibrational images of living cells in tens of seconds with only 1 mW laser power at one focal point. This image acquisition time is more than 10 times faster than that in conventional single-focus Raman microspectroscopy.

QSpec: online control and data analysis system for single-cell Raman spectroscopy

Directory of Open Access Journals (Sweden)

Lihui Ren

2014-06-01

Full Text Available Single-cell phenotyping is critical to the success of biological reductionism. Raman-activated cell sorting (RACS has shown promise in resolving the dynamics of living cells at the individual level and to uncover population heterogeneities in comparison to established approaches such as fluorescence-activated cell sorting (FACS. Given that the number of single-cells would be massive in any experiment, the power of Raman profiling technique for single-cell analysis would be fully utilized only when coupled with a high-throughput and intelligent process control and data analysis system. In this work, we established QSpec, an automatic system that supports high-throughput Raman-based single-cell phenotyping. Additionally, a single-cell Raman profile database has been established upon which data-mining could be applied to discover the heterogeneity among single-cells under different conditions. To test the effectiveness of this control and data analysis system, a sub-system was also developed to simulate the phenotypes of single-cells as well as the device features.

Detection of Explosives on Surfaces Using UV Raman Spectroscopy: Effect of Substrate Color

Science.gov (United States)

2017-10-01

257.23-nm excitation (25 mW at the laser) using 2.5-s integration time and 100 accumulations. Each spectrum is offset by 400 counts from the one...tens of meters have been reported. The testing of UV Raman spectroscopy systems for standoff UV Raman spectroscopy has been generally limited to bare...SP2500A 500-mm focal length monochromator and a PIXIS 400 × 3048 pixel charge-coupled device (CCD) camera (Princeton Instruments, Trenton, NJ). An

Multiwavelength excitation Raman scattering of Cu{sub 2}ZnSn(S{sub x}Se{sub 1−x}){sub 4} (0 ≤ x ≤ 1) polycrystalline thin films: Vibrational properties of sulfoselenide solid solutions

Energy Technology Data Exchange (ETDEWEB)

Dimitrievska, Mirjana; Xie, Haibing; Fairbrother, Andrew; Fontané, Xavier; Saucedo, Edgardo; Izquierdo-Roca, Victor, E-mail: vizquierdo@irec.cat [Catalonia Institute for Energy Research (IREC), Jardins de les Dones de Negre 1 2pl., 08930 Sant Adrià del Besòs, Barcelona (Spain); Gurieva, Galina [Helmholtz Centre Berlin for Materials and Energy, Department Crystallography, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); Pérez-Rodríguez, Alejandro [Catalonia Institute for Energy Research (IREC), Jardins de les Dones de Negre 1 2pl., 08930 Sant Adrià del Besòs, Barcelona (Spain); IN" 2UB, Departament d' Electrònica, Universitat de Barcelona, C. Martí i Franquès 1, 08028 Barcelona (Spain); Schorr, Susan [Helmholtz Centre Berlin for Materials and Energy, Department Crystallography, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); Institute of Geological Sciences, Freie Universität Berlin, Malteserstr. 74-100, 12249 Berlin (Germany)

2014-07-21

In this work, Raman spectroscopy and X-ray diffraction were applied together to evaluate the crystal structure and the phonon modes of photovoltaic grade Cu{sub 2}ZnSn(S{sub x}Se{sub 1−x}){sub 4} thin films, leading to a complete characterization of their structural and vibrational properties. Vibrational characterization has been based on Raman scattering measurements performed with different excitation wavelengths and polarization configurations. Analysis of the experimental spectra has permitted identification of 19 peaks, which positions are in good accord with theoretical predictions. Besides, the observation of Cu{sub 2}ZnSnS{sub 4}-like A symmetry peaks related to S vibrations and Cu{sub 2}ZnSnSe{sub 4}-like A symmetry peaks related to Se vibrations, additional Raman peaks, characteristic of the solid solution and previously not reported, are observed, and are attributed to vibrations involving both S and Se anions.

The Raman Laser Spectrometer for the ExoMars Rover Mission to Mars

Science.gov (United States)

Rull, Fernando; Maurice, Sylvestre; Hutchinson, Ian; Moral, Andoni; Perez, Carlos; Diaz, Carlos; Colombo, Maria; Belenguer, Tomas; Lopez-Reyes, Guillermo; Sansano, Antonio; Forni, Olivier; Parot, Yann; Striebig, Nicolas; Woodward, Simon; Howe, Chris; Tarcea, Nicolau; Rodriguez, Pablo; Seoane, Laura; Santiago, Amaia; Rodriguez-Prieto, Jose A.; Medina, Jesús; Gallego, Paloma; Canchal, Rosario; Santamaría, Pilar; Ramos, Gonzalo; Vago, Jorge L.; RLS Team

2017-07-01

The Raman Laser Spectrometer (RLS) on board the ESA/Roscosmos ExoMars 2020 mission will provide precise identification of the mineral phases and the possibility to detect organics on the Red Planet. The RLS will work on the powdered samples prepared inside the Pasteur analytical suite and collected on the surface and subsurface by a drill system. Raman spectroscopy is a well-known analytical technique based on the inelastic scattering by matter of incident monochromatic light (the Raman effect) that has many applications in laboratory and industry, yet to be used in space applications. Raman spectrometers will be included in two Mars rovers scheduled to be launched in 2020. The Raman instrument for ExoMars 2020 consists of three main units: (1) a transmission spectrograph coupled to a CCD detector; (2) an electronics box, including the excitation laser that controls the instrument functions; and (3) an optical head with an autofocus mechanism illuminating and collecting the scattered light from the spot under investigation. The optical head is connected to the excitation laser and the spectrometer by optical fibers. The instrument also has two targets positioned inside the rover analytical laboratory for onboard Raman spectral calibration. The aim of this article was to present a detailed description of the RLS instrument, including its operation on Mars. To verify RLS operation before launch and to prepare science scenarios for the mission, a simulator of the sample analysis chain has been developed by the team. The results obtained are also discussed. Finally, the potential of the Raman instrument for use in field conditions is addressed. By using a ruggedized prototype, also developed by our team, a wide range of terrestrial analog sites across the world have been studied. These investigations allowed preparing a large collection of real, in situ spectra of samples from different geological processes and periods of Earth evolution. On this basis, we are working

Low-energy excitations of the correlation-gap insulator SmB6: A light-scattering study

International Nuclear Information System (INIS)

Nyhus, P.; Cooper, S.L.; Fisk, Z.; Sarrao, J.

1997-01-01

We present the results of Raman scattering studies of single-crystal SmB 6 for temperatures down to 4 K and in magnetic fields up to 8 T. At temperatures below T * ∼50K the electronic Raman continuum exhibits an abrupt redistribution of scattering intensity around a temperature-independent (open-quotes isobesticclose quotes) energy, Δ c ∼290cm -1 , reflecting the opening of a pseudogap which is larger than previously suggested by transport measurements. Additionally, the Raman response exhibits at least four well-defined excitations within the gap below T * . The field dependencies of some of these in-gap states are consistent with the expected g factor (g eff =2/7) for the Sm 3+ Γ 8 level, suggesting that these gap edge states are crystal-electric-field excitations of the Sm 3+ ion split by magnetoelastic coupling. copyright 1997 The American Physical Society

Fourier-Transform Raman Spectroscopy of Polymers Caractérisation de polymères par spectroscopie Raman à transformée de Fourier

Directory of Open Access Journals (Sweden)

Siesler H. W.

2006-11-01

Full Text Available The recent extension of the Fourier-Transform (FT technique to the Raman effect has launched Raman spectroscopy into a new era of polymer chemical and physical applications. Thus, the increase in signal-to-noise ratio and the improvement in time resolution have largely enhanced the potential of FT-Raman spectroscopy for analytical applications, the characterization of time-dependent phenomena and the on-line combination with other techniques. Primarily the suppression of fluorescence by shifting the excitation line to the near-infrared (NIR region has contributed to the fast acceptance as an industrial routine tool. Furthermore, the application of fiber optics has opened up the areas of process-control and remote sensing. Les applications de la spectroscopie Raman dans le domaine des polymères sont entrées dans une ère nouvelle, grâce aux récents développements de la technique à transformée de Fourier avec excitation dans le proche infrarouge. L'augmentation du rapport signal sur bruit et l'amélioration de la résolution temporelle ont fortement renforcé les potentialités de la technique en ce qui concerne les applications analytiques, la caractérisation de phénomènes qui dépendent du temps et le couplage en ligne avec d'autres techniques. La suppression du phénomène de fluorescence par déplacement de la longueur d'onde de l'excitatrice dans le proche infrarouge a contribué à l'intégration rapide de l'outil en site industriel. L'emploi de fibres optiques a permis l'accroissement des applications dans le domaine du contrôle des procédés et d'analyser à distance.

Circular dichroism and Raman optical activity in antiferromagnetic transition metal fluorides

International Nuclear Information System (INIS)

Hoffman, K.R.; Lockwood, D.J.; Yen, W.M.

2005-01-01

The Raman optical activity (ROA) of magnons in rutile-structure antiferromagnetic FeF 2 (T N = 78 K) has been studied as a function of temperature and applied magnetic field. For exciting light incident along the c axis, ROA is observed for magnons but not for phonons. In zero field, a small splitting (0.09 cm -1 ) of the two acoustic-magnon branches is observed for the first time by inelastic light scattering. The splitting in applied magnetic field is found to reduce with increasing temperature in accordance with theory. No ROA was detected for two-magnon excitations. In optical absorption measurements performed over thirty years ago, a very small circular dichroism (CD) was observed in the magnon sidebands of other simple rutile antiferromagnetic fluorides (MnF 2 and CoF 2 ). The origin of this CD was not understood at the time. The Raman studies of the one-magnon Raman scattering in FeF 2 have demonstrated that in zero field the degeneracy of the antiferromagnetic magnon branches is lifted by a weak magnetic dipole-dipole interaction, as predicted by Pincus and Loudon and by White four decades ago. The source of the observed CD in the magnon sidebands can now be traced to this same magnetic-dipole induced splitting

H α and H β Raman scattering line profiles of the symbiotic star AG Pegasi

Science.gov (United States)

Lee, Seong-Jae; Hyung, Siek

2018-04-01

The H α and H β line profiles of the symbiotic star AG Pegasi, observed in 1998 September (phase ϕ = 10.24), display top narrow double Gaussian components and bottom broad components (FWHM = 200-400 km s-1). The photoionization model indicates that the ionized zone, responsible for the hydrogen Balmer and Lyman lines, is radiation-bounded, with a hydrogen gas number density of nH ˜ 109.85 cm-3 and a gas temperature of Te = 12 000-15 000 K. We have carried out Monte Carlo simulations to fit the Raman scattering broad wings, assuming that the hydrogen Ly β and Ly γ lines emitted within the radiation-bounded H II zone around a white dwarf have the same double Gaussian line profile shape as the hydrogen Balmer lines. The simulation shows that the scattering H I zones are attached to (or located just outside) the inner H II shells. The best fit to the observed broad H I line profiles indicates that the column density of the scattering neutral zone is NH ≃ 3-5 × 1019 cm-2. We have examined whether the geometrical structure responsible for the observed H α and H β line profiles is a bipolar conical shell structure, consisting of the radiation-bounded ionized zone and the outer material bounded neutral zone. The expanding bipolar structure might be two opposite regions of the common envelope or the outer shell of the Roche lobe around the hot white dwarf, formed through the mass inflows from the giant star and pushed out by the fast winds from the hot white dwarf.

Non-destructive NIR-FT-Raman analyses in practice. Part I. Analyses of plants and historic textiles.

Science.gov (United States)

Andreev, G N; Schrader, B; Schulz, H; Fuchs, R; Popov, S; Handjieva, N

2001-12-01

Non-destructive analysis of natural substances in plants as well as of old dyed textiles by Raman spectroscopy has not been possible using conventional techniques. Exciting lines from the visible part of the spectrum produced photochemical and thermal decomposition of the objects as well as strong fluorescence. Using Nd:YAG laser excitation at 1,064 nm together with a special sample arrangement and interferometric recording, various polyacetylenes in Aethusa cynapium and in chamomile (Chamomilla recutita) and the main valuable substances in gentian species (Gentiana lutea and G. punctata), curcuma roots (Curcuma longa), cinnamon (Cinnamomum zeylanicum), fennel (Foeniculum vulgare), clove (Caryophyllus aromaticus), and ginger (Zingiber officinale) were analyzed non-destructively and discussed in comparison with the corresponding pure standard compounds. We further analyzed non-destructively the FT Raman spectra of collections of historical textiles and lakes used for dyeing. It is possible to distinguish the main dye component non-destructively by using Raman bands.

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

Science.gov (United States)

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.

QUANTITATIVE DETECTION OF ENVIRONMENTALLY IMPORTANT DYES USING DIODE LASER/FIBER-OPTIC RAMAN

Science.gov (United States)

A compact diode laser/fiber-optic Raman spectrometer is used for quantitative detection of environmentally important dyes. This system is based on diode laser excitation at 782 mm, fiber optic probe technology, an imaging spectrometer, and state-of-the-art scientific CCD camera. ...

Profilometry of thin films on rough substrates by Raman spectroscopy

KAUST Repository

Ledinský, Martin

2016-12-06

Thin, light-absorbing films attenuate the Raman signal of underlying substrates. In this article, we exploit this phenomenon to develop a contactless thickness profiling method for thin films deposited on rough substrates. We demonstrate this technique by probing profiles of thin amorphous silicon stripes deposited on rough crystalline silicon surfaces, which is a structure exploited in high-efficiency silicon heterojunction solar cells. Our spatially-resolved Raman measurements enable the thickness mapping of amorphous silicon over the whole active area of test solar cells with very high precision; the thickness detection limit is well below 1 nm and the spatial resolution is down to 500 nm, limited only by the optical resolution. We also discuss the wider applicability of this technique for the characterization of thin layers prepared on Raman/photoluminescence-active substrates, as well as its use for single-layer counting in multilayer 2D materials such as graphene, MoS2 and WS2.

Profilometry of thin films on rough substrates by Raman spectroscopy

KAUST Repository

Ledinský , Martin; Paviet-Salomon, Bertrand; Vetushka, Aliaksei; Geissbü hler, Jonas; Tomasi, Andrea; Despeisse, Matthieu; De Wolf, Stefaan; Ballif  , Christophe; Fejfar, Antoní n

2016-01-01

Thin, light-absorbing films attenuate the Raman signal of underlying substrates. In this article, we exploit this phenomenon to develop a contactless thickness profiling method for thin films deposited on rough substrates. We demonstrate this technique by probing profiles of thin amorphous silicon stripes deposited on rough crystalline silicon surfaces, which is a structure exploited in high-efficiency silicon heterojunction solar cells. Our spatially-resolved Raman measurements enable the thickness mapping of amorphous silicon over the whole active area of test solar cells with very high precision; the thickness detection limit is well below 1 nm and the spatial resolution is down to 500 nm, limited only by the optical resolution. We also discuss the wider applicability of this technique for the characterization of thin layers prepared on Raman/photoluminescence-active substrates, as well as its use for single-layer counting in multilayer 2D materials such as graphene, MoS2 and WS2.

Studies of Minerals, Organic and Biogenic Materials through Time-Resolved Raman Spectroscopy

Science.gov (United States)

Garcia, Christopher S.; Abedin, M. Nurul; Ismail, Syed; Sharma, Shiv K.; Misra, Anupam K.; Nyugen, Trac; Elsayed-Ali, hani

2009-01-01

A compact remote Raman spectroscopy system was developed at NASA Langley Research center and was previously demonstrated for its ability to identify chemical composition of various rocks and minerals. In this study, the Raman sensor was utilized to perform time-resolved Raman studies of various samples such as minerals and rocks, Azalea leaves and a few fossil samples. The Raman sensor utilizes a pulsed 532 nm Nd:YAG laser as excitation source, a 4-inch telescope to collect the Raman-scattered signal from a sample several meters away, a spectrograph equipped with a holographic grating, and a gated intensified CCD (ICCD) camera system. Time resolved Raman measurements were carried out by varying the gate delay with fixed short gate width of the ICCD camera, allowing measurement of both Raman signals and fluorescence signals. Rocks and mineral samples were characterized including marble, which contain CaCO3. Analysis of the results reveals the short (approx.10-13 s) lifetime of the Raman process, and shows that Raman spectra of some mineral samples contain fluorescence emission due to organic impurities. Also analyzed were a green (pristine) and a yellow (decayed) sample of Gardenia leaves. It was observed that the fluorescence signals from the green and yellow leaf samples showed stronger signals compared to the Raman lines. Moreover, it was also observed that the fluorescence of the green leaf was more intense and had a shorter lifetime than that of the yellow leaf. For the fossil samples, Raman shifted lines could not be observed due the presence of very strong short-lived fluorescence.

Analysis of thin-film polymers using attenuated total internal reflection-Raman microspectroscopy.

Science.gov (United States)

Tran, Willie; Tisinger, Louis G; Lavalle, Luis E; Sommer, André J

2015-01-01

Two methods commonly employed for molecular surface analysis and thin-film analysis of microscopic areas are attenuated total reflection infrared (ATR-IR) microspectroscopy and confocal Raman microspectroscopy. In the former method, the depth of the evanescent probe beam can be controlled by the wavelength of light, the angle of incidence, or the refractive index of the internal reflection element. Because the penetration depth is proportional to the wavelength of light, one could interrogate a smaller film thickness by moving from the mid-infrared region to the visible region employing Raman spectroscopy. The investigation of ATR Raman microspectroscopy, a largely unexplored technique available to Raman microspectroscopy, was carried out. A Renishaw inVia Raman microscope was externally modified and used in conjunction with a solid immersion lens (SIL) to perform ATR Raman experiments. Thin-film polymer samples were analyzed to explore the theoretical sampling depth for experiments conducted without the SIL, with the SIL, and with the SIL using evanescent excitation. The feasibility of micro-ATR Raman was examined by collecting ATR spectra from films whose thickness measured from 200 to 60 nm. Films of these thicknesses were present on a much thicker substrate, and features from the underlying substrate did not become visible until the thin film reached a thickness of 68 nm.

Noninvasive Monitoring of Blood Glucose with Raman Spectroscopy.

Science.gov (United States)

Pandey, Rishikesh; Paidi, Santosh Kumar; Valdez, Tulio A; Zhang, Chi; Spegazzini, Nicolas; Dasari, Ramachandra Rao; Barman, Ishan

2017-02-21

The successful development of a noninvasive blood glucose sensor that can operate reliably over sustained periods of time has been a much sought after but elusive goal in diabetes management. Since diabetes has no well-established cure, control of elevated glucose levels is critical for avoiding severe secondary health complications in multiple organs including the retina, kidney and vasculature. While fingerstick testing continues to be the mainstay of blood glucose detection, advances in electrochemical sensing-based minimally invasive approaches have opened the door for alternate methods that would considerably improve the quality of life for people with diabetes. In the quest for better sensing approaches, optical technologies have surfaced as attractive candidates as researchers have sought to exploit the endogenous contrast of glucose, notably its absorption, scattering, and polarization properties. Vibrational spectroscopy, especially spontaneous Raman scattering, has exhibited substantial promise due to its exquisite molecular specificity and minimal interference of water in the spectral profiles acquired from the blood-tissue matrix. Yet, it has hitherto been challenging to leverage the Raman scattering signatures of glucose for prediction in all but the most basic studies and under the least demanding conditions. In this Account, we discuss the newly developed array of methodologies that address the key challenges in measuring blood glucose accurately using Raman spectroscopy and unlock new prospects for translation to sustained noninvasive measurements in people with diabetes. Owing to the weak intensity of spontaneous Raman scattering, recent research has focused on enhancement of signals from the blood constituents by designing novel excitation-collection geometries and tissue modulation methods while our attempts have led to the incorporation of nonimaging optical elements. Additionally, invoking mass transfer modeling into chemometric algorithms has

Raman spectroscopy as a PAT for pharmaceutical blending: Advantages and disadvantages.

Science.gov (United States)

Riolo, Daniela; Piazza, Alessandro; Cottini, Ciro; Serafini, Margherita; Lutero, Emilio; Cuoghi, Erika; Gasparini, Lorena; Botturi, Debora; Marino, Iari Gabriel; Aliatis, Irene; Bersani, Danilo; Lottici, Pier Paolo

2018-02-05

Raman spectroscopy has been positively evaluated as a tool for the in-line and real-time monitoring of powder blending processes and it has been proved to be effective in the determination of the endpoint of the mixing, showing its potential role as process analytical technology (PAT). The aim of this study is to show advantages and disadvantages of Raman spectroscopy with respect to the most traditional HPLC analysis. The spectroscopic results, obtained directly on raw powders, sampled from a two-axis blender in real case conditions, were compared with the chromatographic data obtained on the same samples. The formulation blend used for the experiment consists of active pharmaceutical ingredient (API, concentrations 6.0% and 0.5%), lactose and magnesium stearate (as excipients). The first step of the monitoring process was selecting the appropriate wavenumber region where the Raman signal of API is maximal and interference from the spectral features of excipients is minimal. Blend profiles were created by plotting the area ratios of the Raman peak of API (A API ) at 1598cm -1 and the Raman bands of excipients (A EXC ), in the spectral range between 1560 and 1630cm -1 , as a function of mixing time: the API content can be considered homogeneous when the time-dependent dispersion of the area ratio is minimized. In order to achieve a representative sampling with Raman spectroscopy, each sample was mapped in a motorized XY stage by a defocused laser beam of a micro-Raman apparatus. Good correlation between the two techniques has been found only for the composition at 6.0% (w/w). However, standard deviation analysis, applied to both HPLC and Raman data, showed that Raman results are more substantial than HPLC ones, since Raman spectroscopy enables generating data rich blend profiles. In addition, the relative standard deviation calculated from a single map (30 points) turned out to be representative of the degree of homogeneity for that blend time. Copyright © 2017

In situ identification of paper chromatogram spots by surface enhanced Raman scattering

Energy Technology Data Exchange (ETDEWEB)

Tran, C D

1984-01-01

The use of silver hydrosols to enhance the Raman scattering of paper chromatogram spots has been used successfully. This enhancement technique, which is dependent on the interaction between the substrate, silver particles, and paper fibers, has been applied to detection and identification of ng amounts of crystal violet, malachite green, and basic fuchsin with an argon laser of only 4 mW. This technique enhances the resonance of the Raman scattering so that the Raman cross sections of the spots are approximately 9 to 10 orders of magnitude higher than those observed for non-enhanced systems. The limit of detection of the techniques is defined as the amount of dye spot that yields a signal to noise ratio of 2 when excited with the 4MeV.

Commissioning of the KATRIN Raman system for monitoring of the WGTS gas composition

Energy Technology Data Exchange (ETDEWEB)

Fischer, Sebastian; Bornschein, Beate; James, Timothy M.; Off, Andreas; Rupp, Simone; Seitz-Moskaliuk, Hendrik; Sturm, Michael; Wecker, Matthias [Karlsruhe Institute of Technology (Germany); Schloesser, Magnus [Universidad Complutense de Madrid (Spain); Karlsruhe Institute of Technology (Germany); Telle, Helmut H. [Universidad Complutense de Madrid (Spain)

2015-07-01

The Karlsruhe Tritium Neutrino (KATRIN) Experiment aims at determining the neutrino mass by the investigation of the endpoint energy-region of the tritium β-spectrum. Tritium in its molecular form ({sup 3}H{sub 2}) is injected into the Windowless Gaseous Tritium Source (WGTS) of KATRIN, and thus molecular effects, e.g. ro-vibrational excitations levels, have to be considered in the neutrino mass analysis in order to reach the design sensitivity of 200 meV/c{sup 2} (90% C.L.). As the source gas also contains impurities of the other hydrogen isotopes protium and deuterium - giving rise to different molecular excitation levels - continuous and precise monitoring of the source gas composition is required. Raman spectroscopy is the method of choice for this task as it is an inline and non-contact analysis method. In this talk, results from the recently performed commissioning phase of the KATRIN Raman system are presented: over the course of more than 50 days, consecutive Raman spectra (recorded with acquisition times of 60 s) of circulating tritium gas were acquired and analysed in real-time. In addition, valuable information on the system performance during long-term operation was gained.

Using narrowband excitation to confirm that the S∗ state in carotenoids is not a vibrationally-excited ground state species

Science.gov (United States)

Jailaubekov, Askat E.; Song, Sang-Hun; Vengris, Mikas; Cogdell, Richard J.; Larsen, Delmar S.

2010-02-01

The hypothesis that S∗ is a vibrationally-excited ground-state population is tested and discarded for two carotenoid samples: β-carotene in solution and rhodopin glucoside embedded in the light harvesting 2 protein from Rhodopseudomonas acidophila. By demonstrating that the transient absorption signals measured in both systems that are induced by broadband (1000 cm -1) and narrowband (50 cm -1) excitation pulses are near identical and hence bandwidth independent, the impulsive stimulated Raman scattering mechanism proposed as the primary source for S∗ generation is discarded. To support this conclusion, previously published multi-pulse pump-dump-probe signals [17] are revisited to discard secondary mechanisms for S∗ formation.

Hong-Ou-Mandel Interference between Two Deterministic Collective Excitations in an Atomic Ensemble

Science.gov (United States)

Li, Jun; Zhou, Ming-Ti; Jing, Bo; Wang, Xu-Jie; Yang, Sheng-Jun; Jiang, Xiao; Mølmer, Klaus; Bao, Xiao-Hui; Pan, Jian-Wei

2016-10-01

We demonstrate deterministic generation of two distinct collective excitations in one atomic ensemble, and we realize the Hong-Ou-Mandel interference between them. Using Rydberg blockade we create single collective excitations in two different Zeeman levels, and we use stimulated Raman transitions to perform a beam-splitter operation between the excited atomic modes. By converting the atomic excitations into photons, the two-excitation interference is measured by photon coincidence detection with a visibility of 0.89(6). The Hong-Ou-Mandel interference witnesses an entangled NOON state of the collective atomic excitations, and we demonstrate its two times enhanced sensitivity to a magnetic field compared with a single excitation. Our work implements a minimal instance of boson sampling and paves the way for further multimode and multiexcitation studies with collective excitations of atomic ensembles.

Two-photon-excited fluorescence spectroscopy of atomic fluorine at 170 nm

Science.gov (United States)

Herring, G. C.; Dyer, Mark J.; Jusinski, Leonard E.; Bischel, William K.

1988-01-01

Two-photon-excited fluorescence spectroscopy of atomic fluorine is reported. A doubled dye laser at 286-nm is Raman shifted in H2 to 170 nm (sixth anti-Stokes order) to excite ground-state 2P(0)J fluorine atoms to the 2D(0)J level. The fluorine atoms are detected by one of two methods: observing the fluorescence decay to the 2PJ level or observing F(+) production through the absorption of an additional photon by the excited atoms. Relative two-photon absorption cross sections to and the radiative lifetimes of the 2D(0)J states are measured.

Near-infrared Raman spectroscopy using a diode laser and CCD detector for tissue diagnostics

International Nuclear Information System (INIS)

Gustafsson, U.

1993-09-01

This paper surveys the possibility to observe high-quality NIR Raman spectra of both fluorescent and non-fluorescent samples with the use of a diode laser, a fibre optic sample, a single spectrometer and a charge-coupled device (CCD) detector. A shifted excitation difference technique was implemented for removing the broad-band fluorescence emission from Raman spectra of the highly fluorescent samples. Raman spectra of 1.4-dioxane, toluene, rhodamine 6G, and HITCI in the 640 to 1840 cm -1 spectral region and 1.4-dioxane and toluene in the 400 to 3400 cm -1 spectral region have been recorded. The results open the field of sensitive tissue characterisation and the possibility of optical biopsy in vivo by using NIR Raman spectroscopy with fibre optic sampling, a single spectrometer, and a CCD detector

Sandwiched gold/PNIPAm/gold microstructures for smart plasmonics application: towards the high detection limit and Raman quantitative measurements.

Science.gov (United States)

Elashnikov, R; Mares, D; Podzimek, T; Švorčík, V; Lyutakov, O

2017-08-07

A smart plasmonic sensor, comprising a layer of a stimuli-responsive polymer sandwiched between two gold layers, is reported. As a stimuli-responsive material, a monolayer of poly(N-isopropylacrylamide) (PNIPAm) crosslinked globules is used. A quasi-periodic structure of the top gold layer facilitates efficient excitation and serves as a support for plasmon excitation and propagation. The intermediate layer of PNIPAm efficiently entraps targeted molecules from solutions. The sensor structure was optimized for efficient light focusing in the "active" PNIPAm layer. The optimization was based on the time-resolved finite-element simulations, which take into account the thickness of gold layers, size of PNIPAm globules and Raman excitation wavelength (780 nm). The prepared structures were characterized using SEM, AFM, UV-Vis refractometry and goniometry. Additional AFM scans were performed in water at two temperatures corresponding to the collapsed and swollen PNIPAm states. The Raman measurements demonstrate a high detection limit and perfect reproducibility of the Raman scattering signal for the prepared sensor. In addition, the use of created SERS structures for the detection of relevant molecules in the medical, biological and safety fields was demonstrated.

In vivo Raman spectroscopy detects increased epidermal antioxidative potential with topically applied carotenoids

International Nuclear Information System (INIS)

Lademann, J; Richter, H; Patzelt, A; Darvin, M; Sterry, W; Fluhr, J W; Caspers, P J; Van der Pol, A; Zastrow, L

2009-01-01

In the present study, the distribution of the carotenoids as a marker for the complete antioxidative potential in human skin was investigated before and after the topical application of carotenoids by in vivo Raman spectroscopy with an excitation wavelength of 785 nm. The carotenoid profile was assessed after a short term topical application in 4 healthy volunteers. In the untreated skin, the highest concentration of natural carotenoids was detected in different layers of the stratum corneum (SC) close to the skin surface. After topical application of carotenoids, an increase in the antioxidative potential in the skin could be observed. Topically applied carotenoids penetrate deep into the epidermis down to approximately 24 μm. This study supports the hypothesis that antioxidative substances are secreted via eccrine sweat glands and/or sebaceous glands to the skin surface. Subsequently they penetrate into the different layers of the SC

Detection of pigments of halophilic endoliths from gypsum: Raman portable instrument and European Space Agency's prototype analysis

Science.gov (United States)

Culka, Adam; Osterrothová, Kateřina; Hutchinson, Ian; Ingley, Richard; McHugh, Melissa; Oren, Aharon; Edwards, Howell G. M.; Jehlička, Jan

2014-01-01

A prototype instrument, under development at the University of Leicester, for the future European Space Agency (ESA) ExoMars mission, was used for the analysis of microbial pigments within a stratified gypsum crust from a hypersaline saltern evaporation pond at Eilat (Israel). Additionally, the same samples were analysed using a miniaturized Raman spectrometer, featuring the same 532 nm excitation. The differences in the position of the specific bands, attributed to carotenoid pigments from different coloured layers, were minor when analysed by the ESA prototype instrument; therefore, making it difficult to distinguish among the different pigments. The portable Delta Nu Advantage instrument allowed for the discrimination of microbial carotenoids from the orange/green and purple layers. The purpose of this study was to complement previous laboratory results with new data and experience with portable or handheld Raman systems, even with a dedicated prototype Raman system for the exploration of Mars. The latter is equipped with an excitation wavelength falling within the carotenoid polyene resonance region. The ESA prototype Raman instrument detected the carotenoid pigments (biomarkers) with ease, although further detailed distinctions among them were not achieved. PMID:25368354

Detection of pigments of halophilic endoliths from gypsum: Raman portable instrument and European Space Agency's prototype analysis.

Science.gov (United States)

Culka, Adam; Osterrothová, Kateřina; Hutchinson, Ian; Ingley, Richard; McHugh, Melissa; Oren, Aharon; Edwards, Howell G M; Jehlička, Jan

2014-12-13

A prototype instrument, under development at the University of Leicester, for the future European Space Agency (ESA) ExoMars mission, was used for the analysis of microbial pigments within a stratified gypsum crust from a hypersaline saltern evaporation pond at Eilat (Israel). Additionally, the same samples were analysed using a miniaturized Raman spectrometer, featuring the same 532 nm excitation. The differences in the position of the specific bands, attributed to carotenoid pigments from different coloured layers, were minor when analysed by the ESA prototype instrument; therefore, making it difficult to distinguish among the different pigments. The portable Delta Nu Advantage instrument allowed for the discrimination of microbial carotenoids from the orange/green and purple layers. The purpose of this study was to complement previous laboratory results with new data and experience with portable or handheld Raman systems, even with a dedicated prototype Raman system for the exploration of Mars. The latter is equipped with an excitation wavelength falling within the carotenoid polyene resonance region. The ESA prototype Raman instrument detected the carotenoid pigments (biomarkers) with ease, although further detailed distinctions among them were not achieved. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

[Research Progress of Raman Spectroscopy on Dyestuff Identification of Ancient Relics and Artifacts].

Science.gov (United States)

He, Qiu-ju; Wang, Li-qin

2016-02-01

As the birthplace of Silk Road, China has a long dyeing history. The valuable information about the production time, the source of dyeing material, dyeing process and preservation status were existed in organic dyestuff deriving from cultural relics and artifacts. However, because of the low contents, complex compositions and easily degraded of dyestuff, it is always a challenging task to identify the dyestuff in relics analyzing field. As a finger-print spectrum, Raman spectroscopy owns unique superiorities in dyestuff identification. Thus, the principle, characteristic, limitation, progress and development direction of micro-Raman spectroscopy (MRS/µ-Raman), near infrared reflection and Fourier transform Raman spectroscopy (NIR-FT-Raman), surface-enhanced Raman spectroscopy (SERS) and resonance raman spectroscopy (RRS) have been introduced in this paper. Furthermore, the features of Raman spectra of gardenia, curcumin and other natural dyestuffs were classified by MRS technology, and then the fluorescence phenomena of purpurin excitated with different wavelength laser was compared and analyzed. At last, gray green silver colloidal particles were made as the base, then the colorant of madder was identified combining with thin layer chromatography (TLC) separation technology and SERS, the result showed that the surface enhancement effect of silver colloidal particles could significantly reduce fluorescence background of the Raman spectra. It is pointed out that Raman spectroscopy is a rapid and convenient molecular structure qualitative methodology, which has broad application prospect in dyestuff analysis of cultural relics and artifacts. We propose that the combination of multi-Raman spectroscopy, separation technology and long distance transmission technology are the development trends of Raman spectroscopy.

The disorder-induced Raman scattering in Au/MoS{sub 2} heterostructures

Energy Technology Data Exchange (ETDEWEB)

Gołasa, K., E-mail: Katarzyna.Golasa@fuw.edu.pl; Grzeszczyk, M.; Binder, J.; Bożek, R.; Wysmołek, A.; Babiński, A. [Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warszawa (Poland)

2015-07-15

The Raman scattering has been studied in heterostructures composed of a thin MoS{sub 2} flake and a 1-1.5 nm layer of thermally evaporated gold (Au). There have been Au nanoislands detected in the heterostructure. It has been found that their surface density and the average size depend on the MoS{sub 2} thickness. The Raman scattering spectrum in the heterostructure with a few monolayer MoS{sub 2} only weakly depends on the excitation (resonant vs. non-resonant) mode. The overall Raman spectrum corresponds to the total density of phonon states, which is characteristic for disordered systems. The disorder in the MoS{sub 2} layer is related to the mechanical strain induced in the MoS{sub 2} layer by the Au nanoislands. The strain results in the localization of phonon modes, which leads to the relaxation of the momentum conservation rule in the scattering process. The relaxation allows phonons from the whole MoS{sub 2} Brillouin zone to interact with electronic excitations. Our results show that the Au nanoislands resulted from thermal evaporation of a thin metal layer introduce substantial disorder into the crystalline structure of the thin MoS{sub 2} layers.

Normal state Raman spectra of high-Tc cuprates

International Nuclear Information System (INIS)

Bishoyi, K.C.; Rout, G.C.; Behera, S.N.

2003-01-01

We present a microscopic theory to explain Raman spectra of high-T c cuprates R 2-x M x CuO 4 in the normal state. We used electronic Hamiltonian prescribed by Fulde in presence of anti-ferromagnetism. Phonon interaction to the hybridization between the conduction electrons of the system and the f-electrons has been incorporated in the calculation. The phonon spectral density is calculated by the Green function technique of Zubarev at zero wave vector and finite (room) temperature limit. Parameter dependence of Raman active phonon frequencies are studied by varying model parameters of the system i.e. the position of f-level (ε f ), the effective electron-phonon coupling strength (g), the staggered magnetic field (h 1 ), and the hybridization parameter (v). The four Raman active peaks (P 1 to P 4 ) represent the electronic states of the atomic sub-systems of the cuprate systems. They show up as phonon excitations due to the coupling of the phonon to the electrons and the anti-ferromagnetic gap. (author)

Intricate Resonant Raman Response in Anisotropic ReS2.

Science.gov (United States)

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

2017-10-11

The strong in-plane anisotropy of rhenium disulfide (ReS 2 ) offers an additional physical parameter that can be tuned for advanced applications such as logic circuits, thin-film polarizers, and polarization-sensitive photodetectors. ReS 2 also presents advantages for optoelectronics, as it is both a direct-gap semiconductor for few-layer thicknesses (unlike MoS 2 or WS 2 ) 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 ReS 2 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 ReS 2 . In addition, we correct an unrecognized error in the calculation of the optical interference enhancement of the Raman signal of transition metal dichalcogenides on SiO 2 /Si substrates that has propagated through various reports. For ReS 2 , 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 ReS 2 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.

In situ Raman study of redox state changes of mitochondrial cytochromes in a perfused rat heart

DEFF Research Database (Denmark)

Brazhe, Nadezda; Treiman, Marek; Faricelli, Barbara

2013-01-01

We developed a Raman spectroscopy-based approach for simultaneous study of redox changes in c-and b-type cytochromes and for a semiquantitative estimation of the amount of oxygenated myoglobin in a perfused rat heart. Excitation at 532 nm was used to obtain Raman scattering of the myocardial...... surface of the isolated heart at normal and hypoxic conditions. Raman spectra of the heart under normal pO2 demonstrate unique peaks attributable to reduced c-and b-type cytochromes and oxymyoglobin (oMb). The cytochrome peaks decreased in intensity upon FCCP treatment, as predicted from uncoupling...

Mechanisms for the control of two-mode transient stimulated Raman scattering in liquids

International Nuclear Information System (INIS)

Spanner, Michael; Brumer, Paul

2006-01-01

Recent adaptive feedback control experiments demonstrated control of transient (i.e. nonimpulsive) Stokes emission from two closely spaced Raman-active modes in liquid methanol [e.g., B. J. Pearson et al., Phys. Rev. A 63, 063412 (2001)]. Optimally shaped pulses were found that selectively excited one of the two Stokes lines alone, optimized emission from both modes together, or completely suppressed all Stokes emission. Here, two general control mechanisms capable of affecting the ratio of intensities of the Stokes lines are identified. The first is operational when the duration of the pump pulse (t p ) is on the order of the collisional dephasing time (t d ). The ratio of the peak heights of the two Stokes lines can then be controlled by simply varying the duration and/or intensity of the pump pulse. The second operates when 1/t p is on the order of the energy separation of the two Raman modes, and hence when the two Raman modes are coupled due to overlapping nonlinear polarizations that drive the stimulated Raman scattering. In this regime, asymmetry in the spectral amplitudes within the pump pulse can control the asymmetry in the peak heights of the Stokes emission. Both these mechanisms have the same clear physical interpretation: shaping the pump pulse controls the nonlinear optical response of the medium, which in turn controls the stimulated Stokes emission, itself a χ (3) nonlinear effect. In neither mechanism does the ratio of peak heights in the Stokes spectrum reflect directly the ratio of excited-state populations associated with the two Raman modes, as was assumed in the experiments, nor does the control involve coherent quantum interference effects

Raman scattering in the atmospheres of the major planets

International Nuclear Information System (INIS)

Cochran, W.D.; Trafton, L.M.

1978-01-01

A method is developed for calculating the rate at which photons are Raman scattered as a function of frequency and depth in an inhomogeneous anisotropically scattering atmosphere. This method is used to determine the effects of Raman scattering by H 2 in the atmospheres of the major planets. Raman scattering causes an insufficient decrease in the blue and ultraviolet to explain the albedos of all of the planets; an additional source of extinction is necessary in this spectral region. Approximately 0.5-2.0% of the blue continuum photons have undergone Raman scattering in the shallow atmospheres of Jupiter and Saturn, while in the deep atmospheres of Uranus and Neptune Raman scattering accounts for abount 10-15% of the blue continuum intensity. The filling in of the cores of solar lines and the production of Raman-shifted ghosts of the Fraunhofer spectrum will be detectable effects in all of the major planets. Raman scattering has a significant influence on the formation and profiles of the strong red and near-infrared CH 4 bands on Uranus and Neptune. The residual intensity in the cores of these bands may be fully explained as a result of Raman scattering by H 2 . This scattering of photons into the cores of saturated absorption bands will cause an underestimate of the abundance of the absorber unless the effects of Raman scattering by H 2 in an inhomogeneous atmosphere are properly included in the analysis

Raman scattering in a Heisenberg S = 1/2 antiferromagnet on the anisotropic triangular lattice

International Nuclear Information System (INIS)

Perkins, Natalia; Brenig, Wolfram

2009-01-01

We investigate two-magnon Raman scattering from the S = 1/2 Heisenberg antiferromagnet on the triangular lattice (THAF), considering both isotropic and anisotropic exchange interactions. We find that the Raman intensity for the isotropic THAF is insensitive to the scattering geometry, while both the line profile and the intensity of the Raman response for the anisotropic THAF shows a strong dependence on the scattering geometry. For the isotropic case we present an analytical and numerical study of the Raman intensity including both the effect of renormalization of the one-magnon spectrum by 1 = S corrections and final-state magnonmagnon interactions. The bare Raman intensity displays two peaks related to one-magnon van-Hove singularities. We find that 1 = S self-energy corrections to the one-magnon spectrum strongly modify this intensity profile. The central Raman-peak is significantly enhanced due to plateaus in the magnon dispersion, the high frequency peak is suppressed due to magnon damping, and the overall spectral support narrows considerably. Additionally we investigate final-state interactions by solving the Bethe-Salpeter equation to O(1 = S). In contrast to collinear antiferromagnets, the non-collinear nature of the magnetic ground state leads to an irreducible magnon scattering which is retarded and non-separable already to lowest order. We show that final-state interactions lead to a rather broad Raman-continuum centered around approximately twice the 'roton'-energy.

Red-Shift Effects in Surface Enhanced Raman Spectroscopy: Spectral or Intensity Dependence of the Near-Field?

KAUST Repository

Colas, Florent; Cottat, Maximilien; Gillibert, Raymond; Guillot, Nicolas; Djaker, Nadia; Lidgi-Guigui, Nathalie; Toury, Timothé e; Barchiesi, Dominique; Toma, Andrea; Di Fabrizio, Enzo M.; Gucciardi, Pietro Giuseppe; de la Chapelle, Marc Lamy

2016-01-01

Optimum amplification in Surface Enhanced Raman Scattering (SERS) from individual nanoantennas is expected when the excitation is slightly blue-shifted with respect to the Localized Surface Plasmon Resonance (LSPR), so that the LSPR peak falls in the middle between the laser and the Stokes Raman emission. Recent experiments have shown when moving the excitation from the visible to the near-infrared that this rule of thumb is no more valid. The excitation has to be red-shifted with respect to the LSPR peak, up to 80nm, to obtain highest SERS. Such discrepancy is usually attributed to a Near-Field (NF) to Far-Field (FF) spectral shift. Here we critically discuss this hypothesis for the case of gold nanocylinders. By combining multi-wavelength excitation SERS experiments with numerical calculations, we show that the red-shift of the excitation energy does not originate from a spectral shift between the extinction (FF) and the near-field distribution (NF), which is found to be not larger than 10nm. Rather, it can be accounted for by looking at the peculiar spectral dependence of the near-field intensity on the cylinders diameter, characterized by an initial increase, up to 180nm diameter, followed by a decrease and a pronounced skewness.

Red-Shift Effects in Surface Enhanced Raman Spectroscopy: Spectral or Intensity Dependence of the Near-Field?

KAUST Repository

Colas, Florent

2016-06-06

Optimum amplification in Surface Enhanced Raman Scattering (SERS) from individual nanoantennas is expected when the excitation is slightly blue-shifted with respect to the Localized Surface Plasmon Resonance (LSPR), so that the LSPR peak falls in the middle between the laser and the Stokes Raman emission. Recent experiments have shown when moving the excitation from the visible to the near-infrared that this rule of thumb is no more valid. The excitation has to be red-shifted with respect to the LSPR peak, up to 80nm, to obtain highest SERS. Such discrepancy is usually attributed to a Near-Field (NF) to Far-Field (FF) spectral shift. Here we critically discuss this hypothesis for the case of gold nanocylinders. By combining multi-wavelength excitation SERS experiments with numerical calculations, we show that the red-shift of the excitation energy does not originate from a spectral shift between the extinction (FF) and the near-field distribution (NF), which is found to be not larger than 10nm. Rather, it can be accounted for by looking at the peculiar spectral dependence of the near-field intensity on the cylinders diameter, characterized by an initial increase, up to 180nm diameter, followed by a decrease and a pronounced skewness.

Excited states configurations of the quantum Toda lattice

International Nuclear Information System (INIS)

Matsuyama, A.

2001-01-01

Excited states configurations of the quantum Toda lattice are studied by the direct diagonalization of the Hamiltonian. The most probable configurations of one-hole and one-particle excitations are shown to be similar to the profiles of classical phonon and soliton excitations, respectively. One-hole excitation states, which are always ground states of definite E m -symmetry of the dihedral group D N , change those structures abruptly with the potential range varied. One-particle excitations, which are buried in complicated excitation spectra, have well-defined configurations similar to the conoidal profile of the classical periodic Toda lattice. The relationship that the hole (particle) excitations in quantum mechanics correspond to the phonon (soliton) excitations in classical mechanics, which has been suggested based on the similarity of dispersion relations, is confirmed in a geometrically understandable way. Based on the study of one-soliton and two-soliton states, the structure of multi-soliton states in quantum mechanics can be conjectured

Microscopic theory of cavity-enhanced single-photon emission from optical two-photon Raman processes

Science.gov (United States)

Breddermann, Dominik; Praschan, Tom; Heinze, Dirk; Binder, Rolf; Schumacher, Stefan

2018-03-01

We consider cavity-enhanced single-photon generation from stimulated two-photon Raman processes in three-level systems. We compare four fundamental system configurations, one Λ -, one V-, and two ladder (Ξ -) configurations. These can be realized as subsystems of a single quantum dot or of quantum-dot molecules. For a new microscopic understanding of the Raman process, we analyze the Heisenberg equation of motion applying the cluster-expansion scheme. Within this formalism an exact and rigorous definition of a cavity-enhanced Raman photon via its corresponding Raman correlation is possible. This definition for example enables us to systematically investigate the on-demand potential of Raman-transition-based single-photon sources. The four system arrangements can be divided into two subclasses, Λ -type and V-type, which exhibit strongly different Raman-emission characteristics and Raman-emission probabilities. Moreover, our approach reveals whether the Raman path generates a single photon or just induces destructive quantum interference with other excitation paths. Based on our findings and as a first application, we gain a more detailed understanding of experimental data from the literature. Our analysis and results are also transferable to the case of atomic three-level-resonator systems and can be extended to more complicated multilevel schemes.

Towards optical fibre based Raman spectroscopy for the detection of surgical site infection

Science.gov (United States)

Thompson, Alex J.; Koziej, Lukasz; Williams, Huw D.; Elson, Daniel S.; Yang, Guang-Zhong

2016-03-01

Surgical site infections (SSIs) are common post-surgical complications that remain significant clinical problems, as they are associated with substantial mortality and morbidity. As such, there is significant interest in the development of minimally invasive techniques that permit early detection of SSIs. To this end, we are applying a compact, clinically deployable Raman spectrometer coupled to an optical fibre probe to the study of bacteria, with the long term goal of using Raman spectroscopy to detect infection in vivo. Our system comprises a 785 nm laser diode for excitation and a commercial (Ocean Optics, Inc.) Raman spectrometer for detection. Here we discuss the design, optimisation and validation of this system, and describe our first experiences interrogating bacterial cells (Escherichia coli) in vitro.

Energy profile, spectroscopic (FT-IR, FT-Raman and FT-NMR) and DFT studies of 4-bromoisophthalic acid

Science.gov (United States)

Arjunan, V.; Thirunarayanan, S.; Mohan, S.

2018-04-01

The stable conformer of 4-bromoisophthalic acid (BIPA) has been identified by potential energy profile analysis. All the structural parameters of 4-bromoisophthalic acid are determined by B3LYP method with 6-311++G**, 6-31G** and cc-pVTZ basis sets. The fundamental vibrations are analysed with the use of FT-IR (4000-400 cm-1) and FT-Raman (4000-100 cm-1) spectra. The harmonic vibrational frequencies are theoretically calculated and compared with experimental FTIR and FT-Raman frequencies. The 1H and 13C NMR spectra have been analysed and compared with theoretical 1H and 13C NMR chemical shifts calculated by gauge independent atomic orbital (GIAO) method. The electronic properties, such as HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) energies are determined by B3LYP/cc-pVTZ method. The electron density distribution and site of chemical reactivity of BIPA molecule have been obtained by mapping electron density isosurface with molecular electrostatic potential (MEP). Stability of the molecules arising from hyperconjugative interactions, charge delocalizations have been analysed by using natural bond orbital (NBO) analysis. The thermodynamic properties and atomic natural charges of the compound are analysed and the reactive sites of the molecule are identified. The global and local reactivity descriptors are evaluated to analyse the chemical reactivity and site selectivity of molecule through Fukui functions.

Identifying a common origin of toner printed counterfeit banknotes by micro-Raman spectroscopy.

Science.gov (United States)

Skenderović Božičević, Martina; Gajović, Andreja; Zjakić, Igor

2012-11-30

This study explores the applicability of micro-Raman spectroscopy as a non-destructive technique for the analysis of color toner printed counterfeits. The main aim of the research paper was to find out whether Raman spectroscopy is a suitable method for establishing the connection between different specimens of counterfeits suspected to be printed with the same toner on the same machine. Specimens of different types of toners printed on different types of paper are analyzed by means of the micro-Raman spectroscopy system with the excitation line at 514.5 nm. For each specimen cyan, magenta and yellow toners are analyzed separately. The yellow toners displayed the most distinctive Raman spectra. The results show that micro-Raman spectroscopy can be successfully applied as a method for the analysis of color toner printed counterfeits, such as banknotes and documents, in order to establish links between more or less different specimens of counterfeits by measuring the properties of a color toner. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Digital micromirror devices in Raman trace detection of explosives

Science.gov (United States)

Glimtoft, Martin; Svanqvist, Mattias; Ågren, Matilda; Nordberg, Markus; Östmark, Henric

2016-05-01

Imaging Raman spectroscopy based on tunable filters is an established technique for detecting single explosives particles at stand-off distances. However, large light losses are inherent in the design due to sequential imaging at different wavelengths, leading to effective transmission often well below 1 %. The use of digital micromirror devices (DMD) and compressive sensing (CS) in imaging Raman explosives trace detection can improve light throughput and add significant flexibility compared to existing systems. DMDs are based on mature microelectronics technology, and are compact, scalable, and can be customized for specific tasks, including new functions not available with current technologies. This paper has been focusing on investigating how a DMD can be used when applying CS-based imaging Raman spectroscopy on stand-off explosives trace detection, and evaluating the performance in terms of light throughput, image reconstruction ability and potential detection limits. This type of setup also gives the possibility to combine imaging Raman with non-spatially resolved fluorescence suppression techniques, such as Kerr gating. The system used consists of a 2nd harmonics Nd:YAG laser for sample excitation, collection optics, DMD, CMOScamera and a spectrometer with ICCD camera for signal gating and detection. Initial results for compressive sensing imaging Raman shows a stable reconstruction procedure even at low signals and in presence of interfering background signal. It is also shown to give increased effective light transmission without sacrificing molecular specificity or area coverage compared to filter based imaging Raman. At the same time it adds flexibility so the setup can be customized for new functionality.

Structural Evolution in Photoactive Yellow Protein Studied by Femtosecond Stimulated Raman Spectroscopy

Directory of Open Access Journals (Sweden)

Yoshizawa M.

2013-03-01

Full Text Available Ultrafast structural evolution in photoactive yellow protein (PYP is studied by femtosecond stimulated Raman spectroscopy. A comparison between wild-type PYP and E46Q mutant reveals that the hydrogen-bonding network surrounding the chromophore of PYP is immediately rearranged in the electronic excited state.

Significant Contributions of the Albrecht's A Term to Nonresonant Raman Scattering Processes.

Science.gov (United States)

Gong, Zu-Yong; Tian, Guangjun; Duan, Sai; Luo, Yi

2015-11-10

The Raman intensity can be well described by the famous Albrecht's Raman theory that consists of A and B terms. It is well-known that the contribution from Albrecht's A term can be neglected without any loss of accuracy for far-off resonant Raman scattering processes. However, as demonstrated in this study, we have found that this widely accepted long-standing assumption fails drastically for totally symmetric vibration modes of molecules in general off-resonant Raman scattering. Perturbed first-principles calculations for water molecule show that strong constructive interference between the A and B terms occurs for the Raman intensity of the symmetric O-H stretching mode, which can account for ∼40% of the total intensity. Meanwhile, a minor destructive interference is found for the angle bending mode. The state-to-state mapping between Albrecht's theory and perturbation theory allows us to verify the accuracy of the widely employed perturbation method for the dynamic/resonant Raman intensities. The model calculations rationalized from water molecule with the bending mode show that the perturbation method is a good approximation only when the absolute energy difference between the first excited state and the incident light is more than five times greater than the vibrational energy in the ground state.

Ultraviolet resonance Raman spectroscopy for the detection of cocaine in oral fluid

Science.gov (United States)

D'Elia, Valentina; Montalvo, Gemma; Ruiz, Carmen García; Ermolenkov, Vladimir V.; Ahmed, Yasmine; Lednev, Igor K.

2018-01-01

Detecting and quantifying cocaine in oral fluid is of significant importance for practical forensics. Up to date, mainly destructive methods or biochemical tests have been used, while spectroscopic methods were only applied to pretreated samples. In this work, the possibility of using resonance Raman spectroscopy to detect cocaine in oral fluid without pretreating samples was tested. It was found that ultraviolet resonance Raman spectroscopy with 239-nm excitation allows for the detection of cocaine in oral fluid at 10 μg/mL level. Further method development will be needed for reaching the practically useful levels of cocaine detection.

Theory of Two-Magnon Raman Scattering in Iron Pnictides and Chalcogenides

Energy Technology Data Exchange (ETDEWEB)

Chen, C. C.

2011-08-15

Although the parent iron-based pnictides and chalcogenides are itinerant antiferromagnets, the use of local moment picture to understand their magnetic properties is still widespread. We study magnetic Raman scattering from a local moment perspective for various quantum spin models proposed for this new class of superconductors. These models vary greatly in the level of magnetic frustration and show a vastly different two-magnon Raman response. Light scattering by two-magnon excitations thus provides a robust and independent measure of the underlying spin interactions. In accord with other recent experiments, our results indicate that the amount of magnetic frustration in these systems may be small.

Coherent anti-Stokes Raman scattering (CARS) detection or hot atom reaction product internal energy distributions

International Nuclear Information System (INIS)

Quick, C.R. Jr.; Moore, D.S.

1983-01-01

Coherent anti-Stokes Raman spectroscopy (CARS) is being utilized to investigate the rovibrational energy distributions produced by reactive and nonreactive collisions of translationally hot atoms with simple molecules. Translationally hot H atoms are produced by ArF laser photolysis of HBr. Using CARS we have monitored, in a state-specific and time-resolved manner, rotational excitation of HBr (v = 0), vibrational excitation of HBr and H 2 , rovibrational excitation of H 2 produced by the reaction H + HBr → H 2 + Br, and Br atom production by photolysis of HBr

Boxcar detection for high-frequency modulation in stimulated Raman scattering microscopy

Science.gov (United States)

Fimpel, P.; Riek, C.; Ebner, L.; Leitenstorfer, A.; Brida, D.; Zumbusch, A.

2018-04-01

Stimulated Raman scattering (SRS) microscopy is an important non-linear optical technique for the investigation of unlabeled samples. The SRS signal manifests itself as a small intensity exchange between the laser pulses involved in coherent excitation of Raman modes. Usually, high-frequency modulation is applied in one pulse train, and the signal is then detected on the other pulse train via lock-in amplification. While allowing shot-noise limited detection sensitivity, lock-in detection, which corresponds to filtering the signal in the frequency domain, is not the most efficient way of using the excitation light. In this manuscript, we show that boxcar averaging, which is equivalent to temporal filtering, is better suited for the detection of low-duty-cycle signals as encountered in SRS microscopy. We demonstrate that by employing suitable gating windows, the signal-to-noise ratios achievable with lock-in detection can be realized in shorter time with boxcar averaging. Therefore, high-quality images are recorded at a faster rate and lower irradiance which is an important factor, e.g., for minimizing degradation of biological samples.

Enhanced Raman scattering and nonlinear conductivity in Ag-doped hollow ZnO microspheres

Energy Technology Data Exchange (ETDEWEB)

Tringe, Joseph W.; Levie, Harold W.; McCall, Scott K.; Teslich, Nick E.; Wall, Mark A.; Orme, Christine A.; Matthews, Manyalibo J. [Lawrence Livermore National Laboratory, Livermore, CA (United States)

2012-10-15

Hollow spherical ZnO particles doped with Ag were synthesized with a two-step oxidation and sublimation furnace annealing process. Ag nanoparticle precipitates, as observed by transmission electron microscopy, were present in the polycrystalline ZnO matrix at Ag concentrations below 0.02 mol%, significantly below the 0.8 mol% solubility limit for Ag in ZnO. Enhanced Raman scattering of ZnO phonon modes is observed, increasing with Ag nanoparticle concentration. A further enhancement in Raman scattering due to resonance effects was observed for LO phonons excited by 2.33-eV photons as compared with Raman scattering under 1.96-eV excitation. Room-temperature photoluminescence spectra showed both a near-band-edge emission due to free exciton transitions and a mid-gap transition due to the presence of singly ionized oxygen vacancies. ZnO:Ag particles were measured electrically in a packed column and in monolithic form, and in both cases displayed nonlinear current-voltage characteristics similar to those previously observed in sintered ZnO:Ag monoliths where Ag-enhanced disorder at grain boundaries is thought to control current transport. We demonstrate therefore that Ag simultaneously modifies the electrical and optical properties of ZnO particles through the introduction of vacancies and other defects. (orig.)

Revealing silent vibration modes of nanomaterials by detecting anti-Stokes hyper-Raman scattering with femtosecond laser pulses.

Science.gov (United States)

Zeng, Jianhua; Chen, Lei; Dai, Qiaofeng; Lan, Sheng; Tie, Shaolong

2016-01-21

We proposed a scheme in which normal Raman scattering is coupled with hyper-Raman scattering for generating a strong anti-Stokes hyper-Raman scattering in nanomaterials by using femtosecond laser pulses. The proposal was experimentally demonstrated by using a single-layer MoS2 on a SiO2/Si substrate, a 17 nm-thick MoS2 on an Au/SiO2 substrate and a 9 nm-thick MoS2 on a SiO2-SnO2/Ag/SiO2 substrate which were confirmed to be highly efficient for second harmonic generation. A strong anti-Stokes hyper-Raman scattering was also observed in other nanomaterials possessing large second-order susceptibilities, such as silicon quantum dots self-assembled into "coffee" rings and tubular Cu-doped ZnO nanorods. In all the cases, many Raman inactive vibration modes were clearly revealed in the anti-Stokes hyper-Raman scattering. Apart from the strong anti-Stokes hyper-Raman scattering, Stokes hyper-Raman scattering with small Raman shifts was detected during the ablation process of thick MoS2 layers. It was also observed by slightly defocusing the excitation light. The detection of anti-Stokes hyper-Raman scattering may serve as a new technique for studying the Raman inactive vibration modes in nanomaterials.

Combining Raman and laser induced breakdown spectroscopy by double pulse lasing.

Science.gov (United States)

Lednev, Vasily N; Pershin, Sergey M; Sdvizhenskii, Pavel A; Grishin, Mikhail Ya; Fedorov, Alexander N; Bukin, Vladimir V; Oshurko, Vadim B; Shchegolikhin, Alexander N

2018-01-01

A new approach combining Raman spectrometry and laser induced breakdown spectrometry (LIBS) within a single laser event was suggested. A pulsed solid state Nd:YAG laser running in double pulse mode (two frequency-doubled sequential nanosecond laser pulses with dozens microseconds delay) was used to combine two spectrometry methods within a single instrument (Raman/LIBS spectrometer). First, a low-energy laser pulse (power density far below ablation threshold) was used for Raman measurements while a second powerful laser pulse created the plasma suitable for LIBS analysis. A short time delay between two successive pulses allows measuring LIBS and Raman spectra at different moments but within a single laser flash-lamp pumping. Principal advantages of the developed instrument include high quality Raman/LIBS spectra acquisition (due to optimal gating for Raman/LIBS independently) and absence of target thermal alteration during Raman measurements. A series of high quality Raman and LIBS spectra were acquired for inorganic salts (gypsum, anhydrite) as well as for pharmaceutical samples (acetylsalicylic acid). To the best of our knowledge, the quantitative analysis feasibility by combined Raman/LIBS instrument was demonstrated for the first time by calibration curves construction for acetylsalicylic acid (Raman) and copper (LIBS) in gypsum matrix. Combining ablation pulses and Raman measurements (LIBS/Raman measurements) within a single instrument makes it an efficient tool for identification of samples hidden by non-transparent covering or performing depth profiling analysis including remote sensing. Graphical abstract Combining Raman and laser induced breakdown spectroscopy by double pulse lasing.

Resonance Raman investigation of the radical cation of 1,3,5-hexatriene

DEFF Research Database (Denmark)

Keszhelyi, T.; Wilbrandt, R.; Cave, R.J.

1994-01-01

The resonance Raman spectrum of the 1,3,5-hexatriene radical cation generated by gamma-irradiation in a Freon glass is reported. The spectrum is excited at 395 nm in resonance with the second absorption band. Identical spectra are obtained from ionized (E)- and (Z)-1,3,5-hexatriene. The presence...

Development of a photon-cell interactive monte carlo simulation for non-invasive measurement of blood glucose level by Raman spectroscopy.

Science.gov (United States)

Sakota, Daisuke; Kosaka, Ryo; Nishida, Masahiro; Maruyama, Osamu

2015-01-01

Turbidity variation is one of the major limitations in Raman spectroscopy for quantifying blood components, such as glucose, non-invasively. To overcome this limitation, we have developed a Raman scattering simulation using a photon-cell interactive Monte Carlo (pciMC) model that tracks photon migration in both the extra- and intracellular spaces without relying on the macroscopic scattering phase function and anisotropy factor. The interaction of photons at the plasma-cell boundary of randomly oriented three-dimensionally biconcave red blood cells (RBCs) is modeled using geometric optics. The validity of the developed pciMCRaman was investigated by comparing simulation and experimental results of Raman spectroscopy of glucose level in a bovine blood sample. The scattering of the excitation laser at a wavelength of 785 nm was simulated considering the changes in the refractive index of the extracellular solution. Based on the excitation laser photon distribution within the blood, the Raman photon derived from the hemoglobin and glucose molecule at the Raman shift of 1140 cm(-1) = 862 nm was generated, and the photons reaching the detection area were counted. The simulation and experimental results showed good correlation. It is speculated that pciMCRaman can provide information about the ability and limitations of the measurement of blood glucose level.

Generalized oscillator strengths for the valence-shell excitations of argon

International Nuclear Information System (INIS)

Zhu Linfan; Cheng Huadong; Yuan Zhensheng; Liu Xiaojing; Sun Jianmin; Xu Kezun

2006-01-01

The generalized oscillator strengths for the valence-shell excitations to 3p 5 (4s,4s ' ) and 3p 5 (4p,4p ' ) of argon were measured by an angle-resolved fast-electron energy-loss spectrometer at an incident electron energy of 2500 eV. The transition multipolarities for these excitations were elucidated with the help of the calculated intermediate coupling coefficients using the COWAN code. The generalized oscillator strength profiles for the electric dipole excitations to 3p 5 (4s,4s ' ), the electric quadrupole and monopole excitations to 3p 5 (4p,4p ' ) were analyzed and their positions of the extrema were determined. Furthermore, the generalized oscillator strength of the electric quadrupole excitation in 3p→4p was determined and its profile is in general agreement with the theoretical calculations. However, the generalized oscillator strength profile of the electric monopole excitation in 3p→4p is different from the theoretical calculations

Raman spectroscopy of sputtered metal-graphene and metal-oxide-graphene interfaces

Science.gov (United States)

Chen, Ching-Tzu; Gajek, Marcin; Freitag, Marcus; Kuroda, Marcelo; Perebeinos, Vasili; Raoux, Simone

2012-02-01

In this talk, we report our recent development in sputtering deposition of magnetic and non-magnetic metal and metal-oxide thin films on graphene for applications in spintronics and nanoeleoctronics. TEM and SEM images demonstrate homogeneous coverage, uniform thickness, and good crystallinity of the sputtered films. Raman spectroscopy shows that the structure of the underlying graphene is well preserved, and the spectral weight of the defect D mode is comparable to that of the e-beam evaporated samples. Most significantly, we report the first observation of graphene-enhanced surface excitations of crystalline materials. Specifically, we discover two pronounced dispersive Raman modes at the interface of graphene and the nickel-oxide and cobalt-oxide films which we attribute to the strong light absorption and high-order resonant scattering process in the graphene layer. We will present the frequency-dependent, polarization-dependent Raman data of these two modes and discuss their microscopic origin.

Tracking the distribution of "ecstasy" tablets by Raman composition profiling: a large scale feasibility study.

Science.gov (United States)

Bell, Steven E J; Barrett, Lindsay J; Burns, D Thorburn; Dennis, Andrew C; Speers, S James

2003-11-01

Here we report the results of the largest study yet carried out on composition profiling of seized "ecstasy" tablets by Raman spectroscopy. Approximately 1500 tablets from different seizures in N. Ireland were analysed and even though practically all the tablets contained MDMA as active constituent, there were very significant differences in their Raman spectra, which were due to variations in both the nature and concentration of the excipients used and/or the degree of hydration of the MDMA. The ratios of the peak heights of the prominent drug bands at 810 cm(-1) and 716 cm(-1) (which vary with hydration state of the drug), and the drug band at 810 cm(-1) against the largest clearly discernible excipient band in the spectrum were measured for all the samples. It was found that there was sufficient variation in composition in the general sample population to make any matches between batches of tablets taken from different seizures significant, rather than the result of random chance. Despite the large number of different batches of tablets examined in this study, only two examples of indistinguishable sets of tablets were found and in only one of these had the two batches of tablets been seized at different times. Finally, the fact that there are many examples of batches of tablets (particularly in different batches taken from single seizures) in which the differences between each set are sufficiently small that they appear to arise only from random variations within a standard manufacturing method implies that, with more extensive data, it may be possible to recognize the "signature" of tablets prepared by major manufacturers.

Silicon Nitride Background in Nanophotonic Waveguide Enhanced Raman Spectroscopy

Directory of Open Access Journals (Sweden)

Ashim Dhakal

2017-02-01

Full Text Available Recent studies have shown that evanescent Raman spectroscopy using a silicon nitride (SiN nanophotonic waveguide platform has higher signal enhancement when compared to free-space systems. However, signal-to-noise ratio from the waveguide at a low analyte concentration is constrained by the shot-noise from the background light originating from the waveguide itself. Hence, understanding the origin and properties of this waveguide background luminescence (WGBL is essential to developing mitigation strategies. Here, we identify the dominating component of the WGBL spectrum composed of a broad Raman scattering due to momentum selection-rule breaking in amorphous materials, and several peaks specific to molecules embedded in the core. We determine the maximum of the Raman scattering efficiency of the WGBL at room temperature for 785 nm excitation to be 4.5 ± 1 × 10−9 cm−1·sr−1, at a Stokes shift of 200 cm−1. This efficiency decreases monotonically for higher Stokes shifts. Additionally, we also demonstrate the use of slotted waveguides and quasi-transverse magnetic polarization as some mitigation strategies.

Tunable optical setup with high flexibility for spectrally resolved coherent anti-Stokes Raman scattering microscopy

International Nuclear Information System (INIS)

Bergner, G; Akimov, D; Bartelt, H; Dietzek, B; Popp, J; Schlücker, S

2011-01-01

A simplified setup for coherent anti-Stokes Raman scattering (CARS) microscopy is introduced, which allows for recording CARS images with 30 cm -1 excitation bandwidth for probing Raman bands between 500 and 900 cm -1 with minimal requirements for alignment. The experimental arrangement is based on electronic switching between CARS images recorded at different Raman resonances by combining a photonic crystal fiber (PCF) as broadband light source and an acousto-optical programmable dispersive filter (AOPDF) as tunable wavelength filter. Such spatial light modulator enables selection of a narrow-band spectrum to yield high vibrational contrast and hence chemical contrast in the resultant CARS images. Furthermore, an experimental approach to reconstruct spectral information from CARS image contrast is introduced

Confocal Raman spectroscopy to trace lipstick with their smudges on different surfaces.

Science.gov (United States)

López-López, Maria; Özbek, Nil; García-Ruiz, Carmen

2014-06-01

Lipsticks are very popular cosmetic products that can be transferred by contact to different surfaces, being important forensic evidence with an intricate analysis if they are found in a crime scene. This study evaluates the use of confocal Raman microscopy at 780 nm excitation wavelength for the nondestructive identification of 49 lipsticks of different brands and colors, overcoming the lipstick fluorescence problem reported by previous works using other laser wavelengths. Although the lipsticks samples showed some fluorescence, this effect was not so intense to completely overwhelm the Raman spectra. Lipsticks smudges on twelve different surfaces commonly stained with these samples were also analyzed. In the case of the surfaces, some of them provided several bands to the smudge spectra compromising the identification of the lipstick. For these samples spectral subtraction of the interfering bands from the surface was performed. Finally, five different red lipsticks with very similar color were measured on different surfaces to evaluate the lipstick traceability with their smudges even on interfering surfaces. Although previous spectral subtraction was needed in some cases, all the smudged were linked to their corresponding lipsticks even when they are smeared on the interfering surfaces. As a consequence, confocal Raman microscopy using the 780 nm excitation laser is presented as a nondestructive powerful tool for the identification of these tricky samples. Copyright © 2014 Elsevier B.V. All rights reserved.

Parametric Raman crystalline anti-Stokes laser at 503 nm with collinear beam interaction at tangential phase matching

Science.gov (United States)

Smetanin, S. N.; Jelínek, M.; Kubeček, V.

2017-07-01

Stimulated-Raman-scattering in crystals can be used for the single-pass frequency-conversion to the Stokes-shifted wavelengths. The anti-Stokes shift can also be achieved but the phase-matching condition has to be fulfilled because of the parametric four-wave mixing process. To widen the angular-tolerance of four-wave mixing and to obtain high-conversion-efficiency into the anti-Stokes, we developed a new scheme of the parametric Raman anti-Stokes laser at 503 nm with phase-matched collinear beam interaction of orthogonally-polarized Raman components in calcite oriented at the phase-matched angle under 532 nm 20 ps laser excitation. The excitation laser beam was split into two orthogonally-polarized components entering the calcite at the certain incidence angles to fulfill the nearly collinear phase-matching and also to compensate walk-off of extraordinary waves for collinear beam interaction. The phase matching of parametric Raman interaction is tangential and insensitive to the angular mismatch if the Poynting vectors of the biharmonic pump and parametrically generated (anti-Stokes) waves are collinear. For the first time it allows to achieve experimentally the highest conversion efficiency into the anti-Stokes wave (503 nm) up to 30% from the probe wave and up to 3.5% from both pump and probe waves in the single-pass picosecond parametric calcite Raman laser. The highest anti-Stokes pulse energy was 1.4 μJ.

Spatial and spectral resolution of carbonaceous material from hematite (α-Fe2O3) using multivariate curve resolution-alternating least squares (MCR-ALS) with Raman microspectroscopic mapping: implications for the search for life on Mars.

Science.gov (United States)

Smith, Joseph P; Smith, Frank C; Booksh, Karl S

2017-08-21

The search for evidence of extant or past life on Mars is a primary objective of both the upcoming Mars 2020 rover (NASA) and ExoMars 2020 rover (ESA/Roscosmos) missions. This search will involve the detection and identification of organic molecules and/or carbonaceous material within the Martian surface environment. For the first time on a mission to Mars, the scientific payload for each rover will include a Raman spectrometer, an instrument well-suited for this search. Hematite (α-Fe 2 O 3 ) is a widespread mineral on the Martian surface. The 2LO Raman band of hematite and the Raman D-band of carbonaceous material show spectral overlap, leading to the potential misidentification of hematite as carbonaceous material. Here we report the ability to spatially and spectrally differentiate carbonaceous material from hematite using multivariate curve resolution-alternating least squares (MCR-ALS) applied to Raman microspectroscopic mapping under both 532 nm and 785 nm excitation. For this study, a sample comprised of hematite, carbonaceous material, and substrate-adhesive epoxy in spatially distinct domains was constructed. Principal component analysis (PCA) reveals that both 532 nm and 785 nm excitation produce representative three-phase systems of hematite, carbonaceous material, and substrate-adhesive epoxy in the analyzed sample. MCR-ALS with Raman microspectroscopic mapping using both 532 nm and 785 nm excitation was able to resolve hematite, carbonaceous material, and substrate-adhesive epoxy by generating spatially-resolved chemical maps and corresponding Raman spectra of these spatially distinct chemical species. Moreover, MCR-ALS applied to the combinatorial data sets of 532 nm and 785 nm excitation, which contain hematite and carbonaceous material within the same locations, was able to resolve hematite, carbonaceous material, and substrate-adhesive epoxy. Using multivariate analysis with Raman microspectroscopic mapping, 785 nm excitation more effectively

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

Energy Technology Data Exchange (ETDEWEB)

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.

Summary report of FY 1995 Raman spectroscopy technology development

International Nuclear Information System (INIS)

Douglas, J.G.

1995-11-01

US DOE is sponsoring development of remote, fiber-optic Raman spectroscopy for rapid chemical characterization of Hanford high-level radioactive tank waste. Deployment targets for this technology are analytical hot cells and, via the Light-Duty Utility Arm and cone penetrometer, the waste tanks themselves. Perceived benefits of fiber-optic Raman spectroscopy are (1) rapid generation of tank-waste safety-related data, (2) reduced personnel exposure to highly radioactive waste, (3) reduced tank-waste sampling and analysis costs, and (4) reduced radioactive analytical waste. This document presents the results from the investigation of two dispersive, transmission-grating Raman systems and four fiber-optic Raman probe designs with non-radioactive tank waste simulants. One Raman system used a 532-nm, 400 mW, solid-state laser; the other used a 785-nm, 500 mW, solid-state diode laser. We found (1) the transmission-grating systems had better wavelength stability than previously tried Czerny-Turner-Based systems and (2) the 785-nm system's specie detection limits in the spectral fingerprint regiion were at least as good as those for the 532-nm system. Based on these results, and the fact that some tank wastes luminesce with 514.5nm excitation, we selected the 785-nm system for hot-cell use. Of the four probes tested, three had a ''six-around-on'' fiber probe design; the fourth probe was a one-fiber-in-one-fiber-out, diffuse-relectance design. Comparison of the four probes' signal-to-noise rations, rations, transmission/collection efficiencies, and probe-silica Raman backgrounds showed that the best probe for use with Hanford-Site tank waste should (1) be filtered as close to the probe tip as possible to reduce the probe-silica Raman background and (2) have multiple collection fibers. The responses of all the probes tested showed a strong dependence on probe-sample distance, and the presence of a probe window appeared to increase the probe's silica Raman background

Diamagnetic Raman Optical Activity of Chlorine, Bromine, and Iodine Gases

Czech Academy of Sciences Publication Activity Database

Šebestík, Jaroslav; Kapitán, J.; Pačes, Ondřej; Bouř, Petr

2016-01-01

Roč. 55, č. 10 (2016), s. 3504-3508 ISSN 1433-7851 R&D Projects: GA ČR GA13-03978S; GA ČR(CZ) GA14-00431S; GA ČR(CZ) GA16-05935S Institutional support: RVO:61388963 Keywords : angular momentum theory * diamagnetic molecules * excited electronic states * magnetic field * Raman optical activity Subject RIV: CC - Organic Chemistry Impact factor: 11.994, year: 2016

Raman and fluorescent scattering by molecules embedded in small particles

International Nuclear Information System (INIS)

Chew, H.W.; McNulty, P.J.

1983-01-01

We have formulated a model for fluorescent and Raman scattering by molecules embedded in or in the vicinity of small particles. The model takes into account the size, shape, refractive index, and morphology of the host particles. Analytic and numerical results have been obtained for spherical (one and more layers, including magnetic dipole transitions) cylindrical and spheroidal particles. Particular attention has been given to the spherical case with fluorescent/Raman scatterers uniformly distributed in the particles radiating both coherently and incohorently. Depolarization effects have been studied with suitable averaging process, and good agreement with experiment has been obtained. Analytic and numerical results have been obtained for the elastic scattering of evanescent waves; these results are useful for the study of fluorescent under excitation by evanescent waves

Raman spectroscopy applied to identify metabolites in urine of physically active subjects.

Science.gov (United States)

Moreira, Letícia Parada; Silveira, Landulfo; da Silva, Alexandre Galvão; Fernandes, Adriana Barrinha; Pacheco, Marcos Tadeu Tavares; Rocco, Débora Dias Ferraretto Moura

2017-11-01

Raman spectroscopy is a rapid and non-destructive technique suitable for biological fluids analysis. In this work, dispersive Raman spectroscopy has been employed as a rapid and nondestructive technique to detect the metabolites in urine of physically active subjects before and after vigorous 30min pedaling or running compared to sedentary subjects. For so, urine samples from 9 subjects were obtained before and immediately after physical activities and submitted to Raman spectroscopy (830nm excitation, 250mW laser power, 20s integration time) and compared to urine from 5 sedentary subjects. The Raman spectra of urine from sedentary showed peaks related to urea, creatinine, ketone bodies, phosphate and other nitrogenous compounds. These metabolic biomarkers presented peaks with different intensities in the urine of physically active individuals after exercises compared to before, measured by the intensity of selected peaks the Raman spectra, which means different concentrations after training. These peaks presented different intensity values for each subject before physical activity, also behaving differently compared to the post-training: some subjects presented increase while others decrease the intensity. Raman spectroscopy may allow the development of a rapid and non-destructive test for metabolic evaluation of the physical training in active and trained subjects using urine samples, allowing nutrition adjustment with the sport's performance. Copyright © 2017 Elsevier B.V. All rights reserved.

Surface-enhanced raman spectroscopic studies of ellagic acid in silver colloids

Energy Technology Data Exchange (ETDEWEB)

Lee, Seung Jang; Cheong, Byeong Seo; Cho, Han Gook [Dept. of Chemistry, Incheon National University, Incheon (Korea, Republic of)

2015-06-15

Surface-enhanced Raman scattering (SERS) spectroscopy has been applied for the vibrational characterization of ellagic acid (EA), a natural organic dye, using citrate-reduced silver colloids. The infrared and FT-Raman spectra of EA in the solid state were examined for comparison. Spectral assignments of the observed bands were aided by density functional theory (DFT) calculations employing the B3LYP functional. The variations in the SERS spectrum with pH and excitation wavelength were analyzed to gain information on the adsorption- and pH-dependent behaviors of the natural dye on the metal surface. On the basis of the observed spectral features and DFT calculations, the adsorption configuration of EA on the silver metal surface is proposed.

Raman spectroscopy for diagnosis of glioblastoma multiforme

Science.gov (United States)

Clary, Candace Elise

Glioblastoma multiforme (GBM), the most common and most fatal malignant brain tumor, is highly infiltrative and incurable. Although improved prognosis has been demonstrated by surgically resecting the bulk tumor, a lack of clear borders at the tumor margins complicates the selection decision during surgery. This dissertation investigates the potential of Raman spectroscopy for distinguishing between normal and malignant brain tissue and sets the groundwork for a surgical diagnostic guide for resection of gross malignant gliomas. These studies revealed that Raman spectroscopy was capable of discriminating between normal scid mouse brain tissue and human xenograft tumors induced in those mice. The spectra of normal and malignant tissue were normalized by dividing by the respective magnitudes of the peaks near 1440 cm -1. Spectral differences include the shape of the broad peaks near 1440 cm-1 and 1660 cm-1 and the relative magnitudes of the peaks at 1264 cm-1, 1287 cm-1, 1297 cm-1, 1556 cm -1, 1586 cm-1, 1614 cm-1, and 1683 cm-1. From these studies emerged questions regarding how to objectively normalize and compare spectra for future automation. Some differences in the Raman spectra were shown to be inherent in the disease states of the cells themselves via differences in the Raman spectra of normal human astrocytes in culture and cultured cells derived from GBM tumors. The spectra of astrocytes and glioma cells were normalized by dividing by the respective magnitudes of the peaks near 1450 cm-1. The differences between the Raman spectra of normal and transformed cells include the ratio of the 1450 cm-1/1650 cm-1 peaks and the relative magnitudes of the peaks at 1181 cm-1, 1191 cm-1, 1225 cm-1, 1263 cm -1, 1300 cm-1, 1336 cm-1, 1477 cm-1, 1494 cm-1, and 1695 cm -1. Previous Raman spectroscopic studies of biological cells have shown that the magnitude of the Raman signal decreases over time, indicating sample damage. Cells exposed to laser excitation at similar power

Theoretical study of NMR, infrared and Raman spectra on triple-decker phthalocyanines

Energy Technology Data Exchange (ETDEWEB)

Suzuki, Atsushi; Oku, Takeo [Department of Materials Science, The University of Shiga Prefecture 2500 Hassaka, Hikone, Shiga, 522-8533 (Japan)

2016-02-01

Electronic structures and magnetic properties of multi-decker phthalocyanines were studied by theoretical calculation. Electronic structures, excited processes at multi-states, isotropic chemical shifts of {sup 13}C, {sup 14}N and {sup 1}H-nuclear magnetic resonance (NMR), principle V-tensor in electronic field gradient (EFG) tensor and asymmetry parameters (η), vibration mode in infrared (IR) and Raman spectra of triple-decker phthalocyanines were calculated by density functional theory (DFT) and time-dependent DFT using B3LYP as basis function. Electron density distribution was delocalized on the phthalocyanine rings with electron static potential. Considerable separation of chemical shifts in {sup 13}C, {sup 14}N and {sup 1}H-NMR was originated from nuclear spin interaction between nitrogen and carbon atoms, nuclear quadrupole interaction based on EFG and η of central metal under crystal field. Calculated optical absorption at multi-excited process was derived from overlapping π-orbital on the phthalocyanine rings. The vibration modes in IR and Raman spectra were based on in-plane deformation and stretching vibrations of metal-ligand coordination bond on the deformed structure.

Raman scattering and attenuated-total-reflection studies of surface-plasmon polaritons

International Nuclear Information System (INIS)

Kurosawa, K.; Pierce, R.M.; Ushioda, S.; Hemminger, J.C.

1986-01-01

We have made in situ measurements of attenuated total reflection (ATR) and Raman scattering from a layered structure consisting of a glass prism, a thin silver film, an MgF 2 spacer, and a liquid mixture whose refractive index is matched to that of MgF 2 . When the incident angle of the laser beam coincides with the ATR angle, the surface-plasmon polariton (SPP) of the silver film is excited resonantly and the Raman scattering intensity of the liquid shows a maximum. The same effect is observed at the frequency of the Stokes scattered light. By measuring the decrease of the Raman scattering intensity of the liquid with increase of the thickness of the MgF 2 spacer layer, we have determined the decay length (l/sub d/) of the SPP field into the liquid. The measured value of l/sub d/ = 1539 A agrees with the calculated value, 1534 A

Methodology of mycobacteria tuberculosis bacteria detection by Raman spectroscopy

Science.gov (United States)

Zyubin, A.; Lavrova, A.; Manicheva, O.; Dogonadze, M.; Tsibulnikova, A.; Samusev, I.

2018-01-01

We have developed a methodology for the study of deactivated strains of Mycobacterium tuberculosis. Strains of the Beijing species obtained from pulmonary patient secrete (XDR strain) and reference strain (H37Rv) were investigated by Raman spectrometry with He-Ne (632,8 nm) laser excitation source. As a result of the research, the optimal experimental parameters have been obtained to get spectra of mycolic acids, which are part of the cell wall of mycobacteria.

Ultra-violet resonance Raman spectroscopy for the rapid discrimination of urinary tract infection bacteria.

Science.gov (United States)

Jarvis, Roger M; Goodacre, Royston

2004-03-19

The ability to identify pathogenic organisms rapidly provides significant benefits to clinicians; in particular, with respect to best prescription practices and tracking of recurrent infections. Conventional bioassays require 3-5 days before identification of an organism can be made, thus compromising the effectiveness with which patients can be treated for bacterial infections. We analysed 20 clinical isolates of urinary tract infections (UTI) by ultra-violet resonance Raman (UVRR) spectroscopy, utilising 244 nm excitation delivering approximately 0.1 mW laser power at the sample, with typical spectral collection times of 120 s. UVRR results in resonance-enhanced Raman signals for certain chromophoric segments of macromolecules, intensifying those selected bands above what would otherwise be observed for a normal Raman experiment. Utilising the whole-organism 'fingerprints' obtained by UVRR we were able to discriminate successfully between UTI pathogens using chemometric cluster analyses. This work demonstrates significant improvements in the speed with which spectra can be obtained by Raman spectroscopic techniques for the discrimination of clinical bacterial samples.

Measurement of the Raman scattering cross section of the breathing mode in KDP and DKDP crystals.

Science.gov (United States)

Demos, Stavros G; Raman, Rajesh N; Yang, Steven T; Negres, Raluca A; Schaffers, Kathleen I; Henesian, Mark A

2011-10-10

The spontaneous Raman scattering cross sections of the main peaks (related to the A1 vibrational mode) in rapid and conventional grown potassium dihydrogen phosphate and deuterated crystals are measured at 532 nm, 355 nm, and 266 nm. The measurement involves the use of the Raman line of water centered at 3400 cm-1 as a reference to obtain relative values of the cross sections which are subsequently normalized against the known absolute value for water as a function of excitation wavelength. This measurement enables the estimation of the transverse stimulated Raman scattering gain of these nonlinear optical materials in various configurations suitable for frequency conversion and beam control in high-power, large-aperture laser systems.

Periodic driving control of Raman-induced spin-orbit coupling in Bose-Einstein condensates: The heating mechanisms

Science.gov (United States)

Gomez Llorente, J. M.; Plata, J.

2016-06-01

We focus on a technique recently implemented for controlling the magnitude of synthetic spin-orbit coupling (SOC) in ultracold atoms in the Raman-coupling scenario. This technique uses a periodic modulation of the Raman-coupling amplitude to tune the SOC. Specifically, it has been shown that the effect of a high-frequency sinusoidal modulation of the Raman-laser intensity can be incorporated into the undriven Hamiltonian via effective parameters, whose adiabatic variation can therefore be used to tune the SOC. Here, we characterize the heating mechanisms that can be relevant to this method. We identify the main mechanism responsible for the heating observed in the experiments as basically rooted in driving-induced transfer of population to excited states. Characteristics of that process determined by the harmonic trapping, the decay of the excited states, and the technique used for preparing the system are discussed. Additional heating, rooted in departures from adiabaticity in the variation of the effective parameters, is also described. Our analytical study provides some clues that may be useful in the design of strategies for curbing the effects of heating on the efficiency of the control methods.

Optimally shaped narrowband picosecond pulses for femtosecond stimulated Raman spectroscopy.

Science.gov (United States)

Hoffman, David P; Valley, David; Ellis, Scott R; Creelman, Mark; Mathies, Richard A

2013-09-09

A comparison between a Fabry-Pérot etalon filter and a conventional grating filter for producing the picosecond (ps) Raman pump pulses for femtosecond stimulated Raman spectroscopy (FSRS) is presented. It is shown that for pulses of equal energy the etalon filter produces Raman signals twice as large as that of the grating filter while suppressing the electronically resonant background signal. The time asymmetric profile of the etalon-generated pulse is shown to be responsible for both of these observations. A theoretical discussion is presented which quantitatively supports this hypothesis. It is concluded that etalons are the ideal method for the generation of narrowband ps pulses for FSRS because of the optical simplicity, efficiency, improved FSRS intensity and reduced backgrounds.

Analysis of soda-lime glasses using non-negative matrix factor deconvolution of Raman spectra

OpenAIRE

Woelffel , William; Claireaux , Corinne; Toplis , Michael J.; Burov , Ekaterina; Barthel , Etienne; Shukla , Abhay; Biscaras , Johan; Chopinet , Marie-Hélène; Gouillart , Emmanuelle

2015-01-01

International audience; Novel statistical analysis and machine learning algorithms are proposed for the deconvolution and interpretation of Raman spectra of silicate glasses in the Na 2 O-CaO-SiO 2 system. Raman spectra are acquired along diffusion profiles of three pairs of glasses centered around an average composition of 69. 9 wt. % SiO 2 , 12. 7 wt. % CaO , 16. 8 wt. % Na 2 O. The shape changes of the Raman spectra across the compositional domain are analyzed using a combination of princi...

Raman spectroscopy on simple molecular systems at very high density

International Nuclear Information System (INIS)

Schiferl, D.; LeSar, R.S.; Moore, D.S.

1988-01-01

We present an overview of how Raman spectroscopy is done on simple molecular substances at high pressures. Raman spectroscopy is one of the most powerful tools for studying these substances. It is often the quickest means to explore changes in crystal and molecular structures, changes in bond strength, and the formation of new chemical species. Raman measurements have been made at pressures up to 200 GPa (2 Mbar). Even more astonishing is the range of temperatures (4-5200/degree/K) achieved in various static and dynamic (shock-wave) pressure experiments. One point we particularly wish to emphasize is the need for a good theoretical understanding to properly interpret and use experimental results. This is particularly true at ultra-high pressures, where strong crystal field effects can be misinterpreted as incipient insulator-metal transitions. We have tried to point out apparatus, techniques, and results that we feel are particularly noteworthy. We have also included some of the /open quotes/oral tradition/close quotes/ of high pressure Raman spectroscopy -- useful little things that rarely or never appear in print. Because this field is rapidly expanding, we discuss a number of exciting new techniques that have been informally communicated to us, especially those that seem to open new possibilities. 58 refs., 18 figs

Micro-Raman investigations of InN-GaN core-shell nanowires on Si (111) substrate

OpenAIRE

P. Sangeetha; K. Jeganathan; V. Ramakrishnan

2013-01-01

The electron-phonon interactions in InN-GaN core-shell nanowires grown by plasma assisted- molecular beam epitaxy (MBE) on Si (111) substrate have been analysed using micro-Raman spectroscopic technique with the excitation wavelength of 633, 488 and 325 nm. The Raman scattering at 633 nm reveals the characteristic E2 (high) and A1 (LO) phonon mode of InN core at 490 and 590 cm−1 respectively and E2 (high) phonon mode of GaN shell at 573 cm−1. The free carrier concentration of InN core is foun...

Effect of pressure on the second-order Raman scattering intensities of zincblende semiconductors

Energy Technology Data Exchange (ETDEWEB)

Trallero-Giner, C.; Syassen, K. [Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, 70569 Stuttgart (Germany)

2010-01-15

A microscopic description of the two-phonon scattering intensities in direct-gap zincblende-type semiconductors as a function of hydrostatic pressure and for non-resonant excitation is presented. The calculations were performed according to the electron-two-phonon deformation potential interaction for the {gamma}{sub 1} and {gamma}{sub 15} components of the Raman tensor. It is shown that the effect of pressure on the Raman scattering cross-section exhibits a complex behavior according to the contribution of the acoustical or optical phonons to the overtones and combinations. Second-order scattering intensities via acoustical modes could decrease or increase with increasing hydrostatic pressure, while for combinations or overtones of optical phonons a decreasing intensity is obtained. Calculations of the effect of pressure on second-order Raman intensities are compared to experimental results for ZnTe. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

Bacterioruberin and salinixanthin carotenoids of extremely halophilic Archaea and Bacteria: A Raman spectroscopic study

Science.gov (United States)

Jehlička, J.; Edwards, H. G. M.; Oren, A.

2013-04-01

Laboratory cultures of a number of red extremely halophilic Archaea (Halobacterium salinarum strains NRC-1 and R1, Halorubrum sodomense, Haloarcula valismortis) and of Salinibacter ruber, a red extremely halophilic member of the Bacteria, have been investigated by Raman spectroscopy using 514.5 nm excitation to characterize their carotenoids. The 50-carbon carotenoid α-bacterioruberin was detected as the major carotenoid in all archaeal strains. Raman spectroscopy also detected bacterioruberin as the main pigment in a red pellet of cells collected from a saltern crystallizer pond. Salinibacter contains the C40-carotenoid acyl glycoside salinixanthin (all-E, 2'S)-2'-hydroxy-1'-[6-O-(methyltetradecanoyl)-β-D-glycopyranosyloxy]-3',4'-didehydro-1',2'-dihydro-β,ψ-carotene-4-one), for which the Raman bands assignments of are given here for the first time.

Determination of human coronary artery composition by Raman spectroscopy.

Science.gov (United States)

Brennan, J F; Römer, T J; Lees, R S; Tercyak, A M; Kramer, J R; Feld, M S

1997-07-01

We present a method for in situ chemical analysis of human coronary artery using near-infrared Raman spectroscopy. It is rapid and accurate and does not require tissue removal; small volumes, approximately 1 mm3, can be sampled. This methodology is likely to be useful as a tool for intravascular diagnosis of artery disease. Human coronary artery segments were obtained from nine explanted recipient hearts within 1 hour of heart transplantation. Minces from one or more segments were obtained through grinding in a mortar and pestle containing liquid nitrogen. Artery segments and minces were excited with 830 nm near-infrared light, and Raman spectra were collected with a specially designed spectrometer. A model was developed to analyze the spectra and quantify the amounts of cholesterol, cholesterol esters, triglycerides and phospholipids, and calcium salts present. The model provided excellent fits to spectra from the artery segments, indicating its applicability to intact tissue. In addition, the minces were assayed chemically for lipid and calcium salt content, and the results were compared. The relative weights obtained using the Raman technique agreed with those of the standard assays within a few percentage points. The chemical composition of coronary artery can be quantified accurately with Raman spectroscopy. This opens the possibility of using histochemical analysis to predict acute events such as plaque rupture, to follow the progression of disease, and to select appropriate therapeutic interventions.

Analysis of polymer surfaces and thin-film coatings with Raman and surface enhanced Raman scattering

International Nuclear Information System (INIS)

McAnally, Gerard David

2001-01-01

This thesis investigates the potential of surface-enhanced Raman scattering (SERS) for the analysis and characterisation of polymer surfaces. The Raman and SERS spectra from a PET film are presented. The SERS spectra from the related polyester PBT and from the monomer DMT are identical to PET, showing that only the aromatic signals are enhanced. Evidence from other compounds is presented to show that loss of the carbonyl stretch (1725 cm -1 ) from the spectra is due to a chemical interaction between the silver and surface carbonyl groups. The interaction of other polymer functional groups with silver is discussed. A comparison of Raman and SERS spectra collected from three faces of a single crystal shows the SERS spectra are depolarised. AFM images of the silver films used to obtain SERS are presented. They consist of regular islands of silver, fused together to form a complete film. The stability and reproducibility and of these surfaces is assessed. Band assignments for the SERS spectrum of PET are presented. A new band in the spectrum (1131 cm -1 ) is assigned to a complex vibration using a density functional calculation. Depth profiling through a polymer film on to the silver layer showed the SERS signals arise from the silver surface only. The profiles show the effects of refraction on the beam, and the adverse affect on the depth resolution. Silver films were used to obtain SERS spectra from a 40 nm thin-film coating on PET, without interference from the PET layer. The use of an azo dye probe as a marker to detect the coating is described. Finally, a novel method for the synthesis of a SERS-active vinyl-benzotriazole monomer is reported. The monomer was incorporated into a thin-film coating and the SERS spectrum obtained from the polymer. (author)

Anharmonic effects in IR, Raman, and Raman optical activity spectra of alanine and proline zwitterions.

Science.gov (United States)

Danecek, Petr; Kapitán, Josef; Baumruk, Vladimír; Bednárová, Lucie; Kopecký, Vladimír; Bour, Petr

2007-06-14

The difference spectroscopy of the Raman optical activity (ROA) provides extended information about molecular structure. However, interpretation of the spectra is based on complex and often inaccurate simulations. Previously, the authors attempted to make the calculations more robust by including the solvent and exploring the role of molecular flexibility for alanine and proline zwitterions. In the current study, they analyze the IR, Raman, and ROA spectra of these molecules with the emphasis on the force field modeling. Vibrational harmonic frequencies obtained with 25 ab initio methods are compared to experimental band positions. The role of anharmonic terms in the potential and intensity tensors is also systematically explored using the vibrational self-consistent field, vibrational configuration interaction (VCI), and degeneracy-corrected perturbation calculations. The harmonic approach appeared satisfactory for most of the lower-wavelength (200-1800 cm(-1)) vibrations. Modern generalized gradient approximation and hybrid density functionals, such as the common B3LYP method, provided a very good statistical agreement with the experiment. Although the inclusion of the anharmonic corrections still did not lead to complete agreement between the simulations and the experiment, occasional enhancements were achieved across the entire region of wave numbers. Not only the transitional frequencies of the C-H stretching modes were significantly improved but also Raman and ROA spectral profiles including N-H and C-H lower-frequency bending modes were more realistic after application of the VCI correction. A limited Boltzmann averaging for the lowest-frequency modes that could not be included directly in the anharmonic calculus provided a realistic inhomogeneous band broadening. The anharmonic parts of the intensity tensors (second dipole and polarizability derivatives) were found less important for the entire spectral profiles than the force field anharmonicities (third

Identification of color development potential of quartz by Raman spectroscopy

International Nuclear Information System (INIS)

Alkmim, Danielle G.; Lameiras, Fernando S.; Almeida, Frederico O.T.

2013-01-01

Colorless quartz is usually exposed to ionizing radiation (gamma rays or high energy electron beams) to acquire different colors for jewelry. Color development is due to the presence of traces of some elements such as aluminum, iron, hydrogen, lithium, or sodium. Most quartz crystals are extracted colorless from nature and it is necessary to separate those that can develop colors from those that cannot. Irradiation tests can be used to accomplish this separation, but they take a long time. Infrared signature of colorless quartz can also be used. However, infrared spectroscopy is quite expensive, especially when using portable devices. Raman spectroscopy is now available as an inexpensive and portable technique that could provide identification of the samples of colorless quartz still in the field, facilitating the prediction for their economic exploitation. In addition, Raman spectroscopy usually requires a minimum or no sample preparation. This paper presents an investigation of the feasibility of using Raman spectroscopy as a substitute for infrared spectroscopy to predict the potential for color development of quartz. A band at 3595 cm -1 in the Raman shift spectrum was observed only along the c axis of a prasiolite excited by a high power 514 nm laser. This band was not observed in quartz samples that do not develop color after irradiation. Further studies are required to identify the potential for color development by Raman spectroscopy of other types of colorless quartz. (author)

Raman spectral properties of squamous cell carcinoma of oral tissues and cells

Science.gov (United States)

Su, L.; Sun, Y. F.; Chen, Y.; Chen, P.; Shen, A. G.; Wang, X. H.; Jia, J.; Zhao, Y. F.; Zhou, X. D.; Hu, J. M.

2012-01-01

Early diagnosis is the key of the improved survival rates of oral cancer. Raman spectroscopy is sensitive to the early changes of molecular composition and structure that occur in benign lesion during carcinogenesis. In this study, in situ Raman analysis provided distinct spectra that can be used to discriminate between normal and malignant tissues, as well as normal and cancer cells. The biochemical variations between different groups were analyzed by the characteristic bands by comparing the normalized mean spectra. Spectral profiles of normal, malignant conditions show pronounced differences between one another, and multiple Raman markers associated with DNA and protein vibrational modes have been identified that exhibit excellent discrimination power for cancer sample identification. Statistical analyses of the Raman data and classification using principal component analysis (PCA) are shown to be effective for the Raman spectral diagnosis of oral mucosal diseases. The results indicate that the biomolecular differences between normal and malignant conditions are more obviously at the cellular level. This technique could provide a research foundation for the Raman spectral diagnosis of oral mucosal diseases.

Detecting Kerogen as a Biosignature Using Colocated UV Time-Gated Raman and Fluorescence Spectroscopy.

Science.gov (United States)

Shkolyar, Svetlana; Eshelman, Evan J; Farmer, Jack D; Hamilton, David; Daly, Michael G; Youngbull, Cody

2018-04-01

The Mars 2020 mission will analyze samples in situ and identify any that could have preserved biosignatures in ancient habitable environments for later return to Earth. Highest priority targeted samples include aqueously formed sedimentary lithologies. On Earth, such lithologies can contain fossil biosignatures as aromatic carbon (kerogen). In this study, we analyzed nonextracted kerogen in a diverse suite of natural, complex samples using colocated UV excitation (266 nm) time-gated (UV-TG) Raman and laser-induced fluorescence spectroscopies. We interrogated kerogen and its host matrix in samples to (1) explore the capabilities of UV-TG Raman and fluorescence spectroscopies for detecting kerogen in high-priority targets in the search for possible biosignatures on Mars; (2) assess the effectiveness of time gating and UV laser wavelength in reducing fluorescence in Raman spectra; and (3) identify sample-specific issues that could challenge rover-based identifications of kerogen using UV-TG Raman spectroscopy. We found that ungated UV Raman spectroscopy is suited to identify diagnostic kerogen Raman bands without interfering fluorescence and that UV fluorescence spectroscopy is suited to identify kerogen. These results highlight the value of combining colocated Raman and fluorescence spectroscopies, similar to those obtainable by SHERLOC on Mars 2020, to strengthen the confidence of kerogen detection as a potential biosignature in complex natural samples. Key Words: Raman spectroscopy-Laser-induced fluorescence spectroscopy-Mars Sample Return-Mars 2020 mission-Kerogen-Biosignatures. Astrobiology 18, 431-453.

Label-Free Raman Imaging to Monitor Breast Tumor Signatures.

Science.gov (United States)

Manciu, Felicia S; Ciubuc, John D; Parra, Karla; Manciu, Marian; Bennet, Kevin E; Valenzuela, Paloma; Sundin, Emma M; Durrer, William G; Reza, Luis; Francia, Giulio

2017-08-01

Although not yet ready for clinical application, methods based on Raman spectroscopy have shown significant potential in identifying, characterizing, and discriminating between noncancerous and cancerous specimens. Real-time and accurate medical diagnosis achievable through this vibrational optical method largely benefits from improvements in current technological and software capabilities. Not only is the acquisition of spectral information now possible in milliseconds and analysis of hundreds of thousands of data points achieved in minutes, but Raman spectroscopy also allows simultaneous detection and monitoring of several biological components. Besides demonstrating a significant Raman signature distinction between nontumorigenic (MCF-10A) and tumorigenic (MCF-7) breast epithelial cells, our study demonstrates that Raman can be used as a label-free method to evaluate epidermal growth factor activity in tumor cells. Comparative Raman profiles and images of specimens in the presence or absence of epidermal growth factor show important differences in regions attributed to lipid, protein, and nucleic acid vibrations. The occurrence, which is dependent on the presence of epidermal growth factor, of new Raman features associated with the appearance of phosphothreonine and phosphoserine residues reflects a signal transduction from the membrane to the nucleus, with concomitant modification of DNA/RNA structural characteristics. Parallel Western blotting analysis reveals an epidermal growth factor induction of phosphorylated Akt protein, corroborating the Raman results. The analysis presented in this work is an important step toward Raman-based evaluation of biological activity of epidermal growth factor receptors on the surfaces of breast cancer cells. With the ultimate future goal of clinically implementing Raman-guided techniques for the diagnosis of breast tumors (e.g., with regard to specific receptor activity), the current results just lay the foundation for

Raman microspectroscopy, surface-enhanced Raman scattering microspectroscopy, and stable-isotope Raman microspectroscopy for biofilm characterization.

Science.gov (United States)

Ivleva, Natalia P; Kubryk, Patrick; Niessner, Reinhard

2017-07-01

Biofilms represent the predominant form of microbial life on our planet. These aggregates of microorganisms, which are embedded in a matrix formed by extracellular polymeric substances, may colonize nearly all interfaces. Detailed knowledge of microorganisms enclosed in biofilms as well as of the chemical composition, structure, and functions of the complex biofilm matrix and their changes at different stages of the biofilm formation and under various physical and chemical conditions is relevant in different fields. Important research topics include the development and improvement of antibiotics and medical devices and the optimization of biocides, antifouling strategies, and biological wastewater treatment. Raman microspectroscopy is a capable and nondestructive tool that can provide detailed two-dimensional and three-dimensional chemical information about biofilm constituents with the spatial resolution of an optical microscope and without interference from water. However, the sensitivity of Raman microspectroscopy is rather limited, which hampers the applicability of Raman microspectroscopy especially at low biomass concentrations. Fortunately, the resonance Raman effect as well as surface-enhanced Raman scattering can help to overcome this drawback. Furthermore, the combination of Raman microspectroscopy with other microscopic techniques, mass spectrometry techniques, or particularly with stable-isotope techniques can provide comprehensive information on monospecies and multispecies biofilms. Here, an overview of different Raman microspectroscopic techniques, including resonance Raman microspectroscopy and surface-enhanced Raman scattering microspectroscopy, for in situ detection, visualization, identification, and chemical characterization of biofilms is given, and the main feasibilities and limitations of these techniques in biofilm research are presented. Future possibilities of and challenges for Raman microspectroscopy alone and in combination with other

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

International Nuclear Information System (INIS)

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 4 to 10 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

Influence of the ac Stark effect on stimulated hyper-Raman profiles in sodium vapor

International Nuclear Information System (INIS)

Moore, M.A.; Garrett, W.R.; Payne, M.G.

1988-08-01

When pumping near the two-photon 3d resonance in pure sodium vapor and observing the backward hyper-Raman emission to the 3p substates, an asymmetry in ratios of 3p/sub 1/2/, 3p/sub 3/2/ associated emissions was observed dependent upon the direction of the initial laser detuning from the resonance. It has been determined that this asymmetry can be attributed to the ac Stark effect induced by the hyper-Raman emission itself. 3 refs., 3 figs

In-situ Raman microprobe studies of plant cell walls: macromolecular organization and compositional variability in the secondary wall of Picea mariana (Mill.) B.S.P.

Science.gov (United States)

U.P. Agarwal; R.H. Atalla

1986-01-01

Native-state organization and distribution of cell-wall components in the secondary wall of woody tissue from P. mariana (Black Spruce) have been investigated using polarized Raman microspectroscopy. Evidence for orientation is detected through Raman intensity variations resulting from rotations of the exciting electric vector with respect to cell-wall geometry....

Depth profile of strain and composition in Si/Ge dot multilayers by microscopic phonon Raman spectroscopy

International Nuclear Information System (INIS)

Tan, P.H.; Bougeard, D.; Abstreiter, G.; Brunner, K.

2005-01-01

We characterized strain and Ge content depending on depth in a self-assembled Si/Ge dot multilayer by scanning a microscopic Raman probe at a (110) cleavage plane. The multilayer structure was deposited by molecular-beam epitaxy on a (001) Si substrate and consisted of 80 periods, each of them composed by 25 nm Si spacers and 8 monolayer Ge forming laterally and vertically uncorrelated islands with a height of 2 nm and a lateral diameter of about 20 nm. An average biaxial strain of -3.5% within the core regions of islands is determined from the splitting of longitudinal and transversal optical Ge-Ge phonon modes observed in polarized Raman measurements. The absolute mode frequencies further enable analysis of a Ge content of 0.82. The analyzed strain and composition of islands are nearly independent from depths below the sample surface. This indicates well-controlled deposition parameters and negligible intermixing during deposition of subsequent layers. These Raman results are in agreement with x-ray diffraction data. Small, local Raman frequency shifts were observed and discussed with respect to partial elastic strain relaxation of the multilayer stack after cleavage, undefined Raman-scattering geometries at the sample edge, and local heating by the laser probe

Probing channel temperature profiles in Al{sub x}Ga{sub 1−x}N/GaN high electron mobility transistors on 200 mm diameter Si(111) by optical spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Kyaw, L. M., E-mail: a0048661@nus.edu.sg [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore); Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology, and Research), Singapore 117602 (Singapore); Bera, L. K.; Dolmanan, S. B.; Tan, H. R.; Bhat, T. N.; Tripathy, S., E-mail: tripathy-sudhiranjan@imre.a-star.edu.sg [Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology, and Research), Singapore 117602 (Singapore); Liu, Y.; Bera, M. K.; Singh, S. P.; Chor, E. F. [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore)

2014-08-18

Using micro-Raman and photoluminescence (PL) techniques, the channel temperature profile is probed in Al{sub x}Ga{sub 1-x}N/GaN high electron mobility transistors (HEMTs) fabricated on a 200 mm diameter Si(111) substrate. In particular, RuO{sub x}-based gate is used due to the semitransparent nature to the optical excitation wavelengths, thus allowing much accurate thermal investigations underneath the gate. To determine the channel temperature profile in devices subjected to different electrical bias voltages, the GaN band-edge PL peak shift calibration with respect to temperature is used. PL analyses show a maximum channel temperature up to 435 K underneath the gate edge between gate and drain, where the estimated thermal resistance in such a HEMT structure is about 13.7 KmmW{sup −1} at a power dissipation of ∼10 W/mm. The temperature profiles from micro-Raman measurements are also addressed from the E{sub 2}-high optical phonon peak shift of GaN, and this method also probes the temperature-induced peak shifts of optical phonon from Si thus showing the nature of thermal characteristics at the AlN/Si substrate interface.

Micro-Raman investigations of InN-GaN core-shell nanowires on Si (111) substrate

Science.gov (United States)

Sangeetha, P.; Jeganathan, K.; Ramakrishnan, V.

2013-06-01

The electron-phonon interactions in InN-GaN core-shell nanowires grown by plasma assisted- molecular beam epitaxy (MBE) on Si (111) substrate have been analysed using micro-Raman spectroscopic technique with the excitation wavelength of 633, 488 and 325 nm. The Raman scattering at 633 nm reveals the characteristic E2 (high) and A1 (LO) phonon mode of InN core at 490 and 590 cm-1 respectively and E2 (high) phonon mode of GaN shell at 573 cm-1. The free carrier concentration of InN core is found to be low in the order ˜ 1016 cm-3 due to the screening of charge carriers by thin GaN shell. Diameter of InN core evaluated using the spatial correlation model is consistent with the transmission electron microscopic measurement of ˜15 nm. The phonon-life time of core-shell nanowire structure is estimated to be ˜0.4 ps. The micro-Raman mapping and its corresponding localised spectra for 325 nm excitation exhibit intense E2 (high) phonon mode of GaN shell at 573 cm-1 as the decrease of laser interaction length and the signal intensity is quenched at the voids due to high spacing of NWs.

Micro-Raman investigations of InN-GaN core-shell nanowires on Si (111 substrate

Directory of Open Access Journals (Sweden)

P. Sangeetha

2013-06-01

Full Text Available The electron-phonon interactions in InN-GaN core-shell nanowires grown by plasma assisted- molecular beam epitaxy (MBE on Si (111 substrate have been analysed using micro-Raman spectroscopic technique with the excitation wavelength of 633, 488 and 325 nm. The Raman scattering at 633 nm reveals the characteristic E2 (high and A1 (LO phonon mode of InN core at 490 and 590 cm−1 respectively and E2 (high phonon mode of GaN shell at 573 cm−1. The free carrier concentration of InN core is found to be low in the order ∼ 1016 cm−3 due to the screening of charge carriers by thin GaN shell. Diameter of InN core evaluated using the spatial correlation model is consistent with the transmission electron microscopic measurement of ∼15 nm. The phonon-life time of core-shell nanowire structure is estimated to be ∼0.4 ps. The micro-Raman mapping and its corresponding localised spectra for 325 nm excitation exhibit intense E2 (high phonon mode of GaN shell at 573 cm−1 as the decrease of laser interaction length and the signal intensity is quenched at the voids due to high spacing of NWs.

Micro-Raman investigations of InN-GaN core-shell nanowires on Si (111) substrate

International Nuclear Information System (INIS)

Sangeetha, P.; Ramakrishnan, V.; Jeganathan, K.

2013-01-01

The electron-phonon interactions in InN-GaN core-shell nanowires grown by plasma assisted- molecular beam epitaxy (MBE) on Si (111) substrate have been analysed using micro-Raman spectroscopic technique with the excitation wavelength of 633, 488 and 325 nm. The Raman scattering at 633 nm reveals the characteristic E 2 (high) and A 1 (LO) phonon mode of InN core at 490 and 590 cm −1 respectively and E 2 (high) phonon mode of GaN shell at 573 cm −1 . The free carrier concentration of InN core is found to be low in the order ∼ 10 16 cm −3 due to the screening of charge carriers by thin GaN shell. Diameter of InN core evaluated using the spatial correlation model is consistent with the transmission electron microscopic measurement of ∼15 nm. The phonon-life time of core-shell nanowire structure is estimated to be ∼0.4 ps. The micro-Raman mapping and its corresponding localised spectra for 325 nm excitation exhibit intense E 2 (high) phonon mode of GaN shell at 573 cm −1 as the decrease of laser interaction length and the signal intensity is quenched at the voids due to high spacing of NWs.

Effect of hormonal variation on in vivo high wavenumber Raman spectra improves cervical precancer detection

Science.gov (United States)

Duraipandian, Shiyamala; Zheng, Wei; Ng, Joseph; Low, Jeffrey J. H.; Ilancheran, A.; Huang, Zhiwei

2012-03-01

Raman spectroscopy is a unique analytical probe for molecular vibration and is capable of providing specific spectroscopic fingerprints of molecular compositions and structures of biological tissues. The aim of this study is to improve the classification accuracy of cervical precancer by characterizing the variations in the normal high wavenumber (HW - 2800-3700cm-1) Raman spectra arising from the menopausal status of the cervix. A rapidacquisition near-infrared (NIR) Raman spectroscopic system was used for in vivo tissue Raman measurements at 785 nm excitation. Individual HW Raman spectrum was measured with a 5s exposure time from both normal and precancer tissue sites of 15 patients recruited. The acquired Raman spectra were stratified based on the menopausal status of the cervix before the data analysis. Significant differences were noticed in Raman intensities of prominent band at 2924 cm-1 (CH3 stretching of proteins) and the broad water Raman band (in the 3100-3700 cm-1 range) with a peak at 3390 cm-1 in normal and dysplasia cervical tissue sites. Multivariate diagnostic decision algorithm based on principal component analysis (PCA) and linear discriminant analysis (LDA) was utilized to successfully differentiate the normal and precancer cervical tissue sites. By considering the variations in the Raman spectra of normal cervix due to the hormonal or menopausal status of women, the diagnostic accuracy was improved from 71 to 91%. By incorporating these variations prior to tissue classification, we can significantly improve the accuracy of cervical precancer detection using HW Raman spectroscopy.

In vitro quantitation of human femoral artery atherosclerosis using near-infrared Raman spectroscopy

Science.gov (United States)

Dykes, Ava C.; Anastasiadis, Pavlos; Allen, John S., III; Sharma, Shiv K.

2012-06-01

Near-infrared Raman spectroscopy has been used in vitro to identify calcified atherosclerotic plaques in human femoral arteries. Raman techniques allow for the identification of these plaques in a nondestructive manner, which may allow for the diagnosis of coronary artery disease in cardiac patients in the future. As Raman spectroscopy also reveals chemical information about the composition of the arteries, it can also be used as a prognostic tool. The in vivo detection of atherosclerotic plaques at risk for rupture in cardiac patients will enhance treatment methods while improving clinical outcomes for these procedures. Raman spectra were excited by an Invictus 785-nm NIR laser and measured with a fiber-coupled micro-Raman RXN system (Kaiser Optical Systems, Inc., Ann Arbor, MI) equipped with a 785 nm CW laser and CCD detector. Chemical mapping of arteries obtained post mortem allowed for the discrete location of atherosclerotic plaques. Raman peaks at 961 and 1073 cm-1 reveal the presence of calcium hydroxyapatite and carbonate apatite, which are known to be present in calcified plaques. By mapping the locations of these peaks the boundaries of the plaques can be precisely determined. Areas of varying degrees of calcification were also identified. Because this can be useful in determining the degree of plaque calcification and vessel stenosis, this may have a significant impact on the clinical treatment of atherosclerotic plaques in the future.

Quantum well effect in bulk PbI(2) crystals revealed by the anisotropy of photoluminescence and Raman spectra.

Science.gov (United States)

Baltog, I; Baibarac, M; Lefrant, S

2009-01-14

On subjecting a bulk 2H-PbI(2) crystal to vacuum annealing at 500 K followed by a sudden cooling at liquid nitrogen temperature stacking faults are generated that separate distinct layers of nanometric thickness in which different numbers of I-Pb-I atomic layers are bundled together. Such structures, containing two, three, four, five etc I-Pb-I atomic layers, behave as quantum wells of different widths. The signature of such a transformation is given by a shift towards higher energies of the fundamental absorption edge, which is experimentally revealed by specific anisotropies in the photoluminescence and Raman spectra. The quantum confining effect is made visible by specific variations of a wide extra-excitonic band (G) at 2.06 eV that originates in the radiative recombination of carriers (electrons and holes), trapped on the surface defects. The excitation spectrum of the G band, with p polarized exciting light, reveals a fine structure comprised of narrow bands at 2.75, 2.64, 2.59 and 2.56 eV, which are associated with the PbI(2) quantum wells formed from two, three, four and five I-Pb-I atomic layers of 0.7 nm thickness. Regardless of the polarization state of the laser exciting light of 514.5 nm (2.41 eV), which is close to the band gap energy of PbI(2) (2.52 eV), the Raman scattering on bulk as-grown PbI(2) crystals has the character of a resonant process. For p polarized exciting light, the Raman scattering process on vacuum annealed PbI(2) becomes non-resonant. This originates from the quantum well structures generated inside the crystal, whose band gap energies are higher than the energy of the exciting light.

A Raman-Based Portable Fuel Analyzer

Science.gov (United States)

Farquharson, Stuart

2010-08-01

Fuel is the single most import supply during war. Consider that the US Military is employing over 25,000 vehicles in Iraq and Afghanistan. Most fuel is obtained locally, and must be characterized to ensure proper operation of these vehicles. Fuel properties are currently determined using a deployed chemical laboratory. Unfortunately, each sample requires in excess of 6 hours to characterize. To overcome this limitation, we have developed a portable fuel analyzer capable of determine 7 fuel properties that allow determining fuel usage. The analyzer uses Raman spectroscopy to measure the fuel samples without preparation in 2 minutes. The challenge, however, is that as distilled fractions of crude oil, all fuels are composed of hundreds of hydrocarbon components that boil at similar temperatures, and performance properties can not be simply correlated to a single component, and certainly not to specific Raman peaks. To meet this challenge, we measured over 800 diesel and jet fuels from around the world and used chemometrics to correlate the Raman spectra to fuel properties. Critical to the success of this approach is laser excitation at 1064 nm to avoid fluorescence interference (many fuels fluoresce) and a rugged interferometer that provides 0.1 cm-1 wavenumber (x-axis) accuracy to guarantee accurate correlations. Here we describe the portable fuel analyzer, the chemometric models, and the successful determination of these 7 fuel properties for over 100 unknown samples provided by the US Marine Corps, US Navy, and US Army.

Design and performance of an ultraviolet resonance Raman spectrometer for proteins and nucleic acids.

Science.gov (United States)

Russell, M P; Vohník, S; Thomas, G J

1995-04-01

We describe an ultraviolet resonance Raman (UVRR) spectrometer appropriate for structural studies of biological macromolecules and their assemblies. Instrument design includes the following features: a continuous wave, intracavity doubled, ultraviolet laser source for excitation of the Raman spectrum; a rotating cell (or jet source) for presentation of the sample to the laser beam; a Cassegrain optic with f/1.0 aperture for collection of the Raman scattering; a quartz prism dispersing element for rejection of stray light and Rayleigh scattering; a 0.75-m single grating monochromator for dispersion of the Raman scattering; and a liquid-nitrogen-cooled, charge-coupled device for detection of the Raman photons. The performance of this instrument, assessed on the basis of the observed signal-to-noise ratios, the apparent resolution of closely spaced spectral bands, and the wide spectrometer bandpass of 2200 cm-1, is believed superior to previously described UVRR spectrometers of similar design. Performance characteristics of the instrument are demonstrated in UVRR spectra obtained from standard solvents, p-ethylphenol, which serves as a model for the tyrosine side chain, the DNA nucleotide deoxyguanosine-5'-monophosphate, and the human tumor necrosis factor binding protein, which is considered representative of soluble globular proteins.

Micro-raman and tip-enhanced raman spectroscopy of carbon allotropes

NARCIS (Netherlands)

Hoffmann, G.G.; With, de G.; Loos, J.

2008-01-01

Raman spectroscopic data are obtained on various carbon allotropes like diamond, amorphous carbon, graphite, graphene and single wall carbon nanotubes by micro-Raman spectroscopy, tip-enhanced Raman spectroscopy and tip-enhanced Raman spectroscopy imaging, and the potentials of these techniques for

Evolution of magnetic and superconducting fluctuations with doping of high-Tc superconductors. An electronic Raman scattering study

International Nuclear Information System (INIS)

Blumberg, G.

1998-01-01

For YBa 2 Cu 3 O 6+δ and Bi 2 Sr 2 CaCu 2 O 3±δ superconductors, electronic Raman scattering from high- and low-energy excitations has been studied in relation to the hole doping level, temperature, and energy of the incident photons. For underdoped superconductors, it is concluded that short range antiferromagnetic (AF) correlations persist with hole doping and doped single holes are incoherent in the AF environment. Above the superconducting (SC) transition temperature T c the system exhibits a sharp Raman resonance of B 1g symmetry and about 75 meV energy and a pseudogap for electron-hole excitations below 75 meV, a manifestation of a partially coherent state forming from doped incoherent quasi-particles. The occupancy of the coherent state increases with cooling until phase ordering at T c produces a global SC state

In-situ characterization of meat aging with diode-laser Raman spectroscopy

Science.gov (United States)

Schmidt, Heinar; Blum, Jenny; Sowoidnich, Kay; Sumpf, Bernd; Schwägele, Fredi; Kronfeldt, Heinz-Detlef

2009-05-01

Due to the narrow linewidth signals and its fingerprinting nature, Raman spectra provide information about the molecular structure and composition of the samples. In this paper, the applicability of Raman spectroscopy is shown for the in-situ characterization of the aging of meat. Miniaturized diode lasers are utilized as light sources with excitation wavelengths of 671 nm and 785 nm with a view to the development of a portable field device for meat. As test sample, musculus longissimus dorsi from pork was taken. The chops were stored refrigerated at 5 °C and Raman spectra were measured daily from slaughter up to three weeks. Throughout the entire period of one month, the Raman spectra preserve the basic spectral features identifying the samples as meat. More specific, the spectra exhibit gradual changes of the Raman signals and they show a time-dependent modification of the background signal which arises from a laser-induced fluorescence (LIF). To analyze the time-correlation of the complex spectra, multivariate statistical methods are employed. By means of principal components analysis (PCA) a distinction of spectra is found on the time scale between day 8 and 10. This corresponds to the transition from ripened meat to meat at and beyond the limit of inedibility. After ca. 10 days of storage at 5 °C the microbial load is overwhelming and LIF increases. The results of the Raman measurements depending on the storage time of meat are discussed in the context of reference analyses which have been performed in parallel.

Influence of a photoexcited electron-hole plasma on the Raman scattering spectra of YBa2Cu3Ox single crystals

International Nuclear Information System (INIS)

Goncharov, A.F.; Denisov, V.N.; Mavrin, B.N.; Podobedov, V.B.

1988-01-01

The Raman spectra of tetragonal YBa 2 Cu 3 O x crystals in the region of ∼500 cm -1 were determined using different power densities I 0 of the exciting radiation of wavelengths 4,880, 5,145, 5,321, and 6,471 angstrom at temperatures 80-300 K. An increase in I 0 revealed changes in the spectra due to interference of the electron continuum with a 470 cm -1 phonon and also due to activation of 560-590 cm -1 dipole vibrations because of interaction of photocarriers with the crystal lattice. An analysis of the spectra yielded the electron-phonon interaction constant. The changes in the spectra were of resonant nature, but they were absent in the case of the excitation wavelengths 5,321 and 6,471 angstrom. A triple multichannel Raman spectrometer, developed by the authors, made it possible to record simultaneously a spectral interval of 500 cm -1 in the range ≥ 25 cm -1 on excitation with cw laser radiation

Line-scan macro-scale Raman chemical imaging for authentication of powdered foods and ingredients

Science.gov (United States)

Adulteration and fraud for powdered foods and ingredients are rising food safety risks that threaten consumers’ health. In this study, a newly developed line-scan macro-scale Raman imaging system using a 5 W 785 nm line laser as excitation source was used to authenticate the food powders. The system...

Raman scattering study of filled skutterudite compounds

International Nuclear Information System (INIS)

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

2007-01-01

Raman scattering of skutterudite compounds RT 4 X 12 (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 RRu 4 P 12 (R=La and Sm) and ROs 4 Sb 12 (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 RFe 4 Sb 12 and RRu 4 Sb 12 . 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 PrRu 4 P 12 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

Aggregation of nanoparticles in endosomes and lysosomes produces surface-enhanced Raman spectroscopy

Science.gov (United States)

Lucas, Leanne J.; Chen, Xiaoke K.; Smith, Aaron J.; Korbelik, Mladen; Zeng, Haishan; Lee, Patrick W. K.; Hewitt, Kevin Cecil

2015-01-01

The purpose of this study was to explore the use of surface-enhanced Raman spectroscopy (SERS) to image the distribution of epidermal growth factor receptor (EGFR) in cells. To accomplish this task, 30-nm gold nanoparticles (AuNPs) tagged with antibodies to EGFR (1012 per mL) were incubated with cells (106 per mL) of the A431 human epidermoid carcinoma and normal human bronchial epithelial cell lines. Using the 632.8-nm excitation line of a He-Ne laser, Raman spectroscopy measurements were performed using a point mapping scheme. Normal cells show little to no enhancement. SERS signals were observed inside the cytoplasm of A431 cells with an overall enhancement of 4 to 7 orders of magnitude. Raman intensity maps of the 1450 and 1583 cm-1 peaks correlate well with the expected distribution of EGFR and AuNPs, aggregated following uptake by endosomes and lysosomes. Spectral features from tyrosine and tryptophan residues dominate the SERS signals.

Raman micro-spectroscopy analysis of different sperm regions: a species comparison.

Science.gov (United States)

Amaral, S; Da Costa, R; Wübbeling, F; Redmann, K; Schlatt, S

2018-04-01

Is Raman micro-spectroscopy a valid approach to assess the biochemical hallmarks of sperm regions (head, midpiece and tail) in four different species? Non-invasive Raman micro-spectroscopy provides spectral patterns enabling the biochemical characterization of the three sperm regions in the four species, revealing however high similarities for each region among species. Raman micro-spectroscopy has been described as an innovative method to assess sperm features having the potential to be used as a non-invasive selection tool. However, except for nuclear DNA, the identification and assignment of spectral bands in Raman-profiles to the different sperm regions is scarce and controversial. Raman spectra from head, midpiece and tail of four different species were obtained. Sperm samples were collected and smeared on microscope slides. Air dried samples were subjected to Raman analysis using previously standardized procedures. Sperm samples from (i) two donors attending the infertility clinic at the Centre of Reproductive Medicine and Andrology; (ii) two C57BL/6 -TgN (ACTbEGFP) 1Osb adult mice; (iii) two adult Cynomolgus monkeys (Macaca fascicularis) and (iv) two sea urchins (Arbacia punctulata) were used to characterize and compare their spectral profiles. Differences and similarities were confirmed by principal component analysis (PCA). Several novel region-specific peaks were identified. The three regions could be differentiated by distinctive Raman patterns irrespective of the species. However, regardless of the specie, their main spectral pattern remains mostly unchanged. These results were corroborated by the PCA analysis and suggest that the basic constituents of spermatozoa are biochemically similar among species. Further research should be performed in live sperm to validate the detected spectral bands and their use as markers of distinctive regions. Raman peaks that have never been described in the sperm cell were detected. Particularly important are those that

Measuring the One-Particle Excitations of Ultracold Fermionic Atoms by Stimulated Raman Spectroscopy

International Nuclear Information System (INIS)

Dao, T.-L.; Georges, Antoine; Dalibard, Jean; Salomon, Christophe; Carusotto, Iacopo

2007-01-01

We propose a Raman spectroscopy technique which is able to probe the one-particle Green function, the Fermi surface, and the quasiparticles of a gas of strongly interacting ultracold atoms. We give quantitative examples of experimentally accessible spectra. The efficiency of the method is validated by means of simulated images for the case of a usual Fermi liquid as well as for more exotic states: specific signatures of, e.g., a d-wave pseudogap are clearly visible

Three-beam double stimulated Raman scatterings: Cascading configuration

Science.gov (United States)

Rao, B. Jayachander; Cho, Minhaeng

2018-03-01

present a theoretical expression and numerical simulation results for the full-width-at-half-maximum of SRS imaging point spread function, assuming that the pump and Stokes beam profiles are Gaussian and the second Stokes beam has a doughnut-shaped spatial profile. It is clear that the spatial resolution with the present 3-beam cascading SRS method can be enhanced well beyond the diffraction limit. We anticipate that the present work will provide a theoretical framework for a super-resolution stimulated Raman scattering microscopy that is currently under investigation.

Ultraviolet resonance Raman studies of N-methylacetamide

International Nuclear Information System (INIS)

Mayne, L.C.; Ziegler, L.D.; Hudson, B.

1985-01-01

Resonance Raman spectra of the simple peptide model compound N-methylacetamide have been obtained with 218- and 200-nm laser radiation. A large enhancement of the amide II vibration is observed relative to that of Raman spectra obtained with visible radiation. Replacement of the amide hydrogen by deuterium results in a spectrum with most of its intensity in the amide II' mode. Excitation of this deuterated species with 200-nm radiation results in intensity in the overtones of this modes, a feature characteristic of resonance enhanced spectra. Isotopic substitution of the amide carbon and nitrogen by 13 C and 15 N results in a spectral shift to lower frequency by nearly the amount expected for a normal mode consisting primarily of the motion of the amide C and N atoms. These results, taken together, demonstrate that the geometry change of N-methylacetamide upon electronic excitation to the π-π/sup */ state is dominated by a change in the C-N bond length. Studies of mixtures of the deuterio and protio forms show that a significant normal mode rotation occurs on isotopic substitution such that the amide II' of the deuterio form becomes approximately equally distributed between the amide II and III vibrations of the protio form. The amide I and I' vibrations are very diffuse in aqueous solutions at the dilutions used. These bands become sharp in acetonitrile. This behavior is interpreted in terms of a range of frequencies for this vibration due to a distribution of hydrogen-bonded species. 23 references, 5 figures

Raman spectra, electrochemical redox potentials and intramolucular reorganization due to ionization and excitation of benzodifuranone chromophore

Czech Academy of Sciences Publication Activity Database

Luňák, S. Jr.; Frumarová, Božena; Mikysek, T.; Vyňuchal, J.

2013-01-01

Roč. 570, 10 May (2013), s. 50-55 ISSN 0009-2614 Institutional support: RVO:61389013 Keywords : benzodifuranone * DFT calculations * Raman spectroscopy Subject RIV: CA - Inorganic Chemistry Impact factor: 1.991, year: 2013

Theory of two-magnon Raman scattering in alkaline iron selenide superconductors

Energy Technology Data Exchange (ETDEWEB)

Liu, C.S. [Department of Physics, Yanshan University, Qinhuangdao 006004 (China); Department of Physics, National Taiwan Normal University, Taipei 11677, Taiwan (China); Zhang, A.M. [Department of Physics, Renmin University of China, Beijing 100872 (China); Xu, T.F. [Department of Physics, Yanshan University, Qinhuangdao 006004 (China); Wu, W.C., E-mail: wu@phy.ntnu.edu.tw [Department of Physics, National Taiwan Normal University, Taipei 11677, Taiwan (China)

2014-11-15

Highlights: • Two-magnon Raman scattering is theoretically studied for alkaline iron selenides. • Underlying spin interactions of the √(5)×√(5) AF superstructure are investigated in details. • Optimal set of exchange parameters is revealed when fitting to experiments. - Abstract: Motivated by the recent experiment of two-magnon Raman scattering in alkaline iron selenide superconductors (Zhang et al., 2012), we investigate in details the underlying spin interactions of the √(5)×√(5) antiferromagnetic superstructure. Based on the linear spin wave approximation, the Fleury-London (FL) two-magnon Raman cross-sections are calculated. By comparing theoretical results with the Raman data in both A{sub g} and B{sub g} channels, an optimal set of exchange parameters which are consistent with the fitting to the neutron scattering data are obtained. It reveals that the experimentally observed broad and asymmetric peaks around 1600 cm{sup −1} are dominantly originated from quasiparticle excitations in two nearly degenerate magnon bands in the (0,±π) and (±π,0) directions. The result thus supports that the magnetic properties in alkaline iron selenide AFe{sub 1.6+x}Se{sub 6} superconductors can be basically described by the quantum spin model with up to third nearest-neighbor exchange couplings.

Spatially resolved Raman spectroscopy study of transformed zones in magnesia-partially-stabilized zirconia

International Nuclear Information System (INIS)

Davskardt, R.H.; Veirs, D.K.; Ritchie, R.O.

1989-01-01

Raman vibrational spectroscopy provides an effective phase characterization technique in materials systems containing particle dispersions of the tetragonal and monoclinic polymorphs of zirconia, each of which yields a unique Raman spectrum. An investigation is reported to assess a novel, spatially resolved Raman spectroscopy system in the study of transformed zones surrounding cracks in partially stabilized MgO-ZrO 2 (PSZ). The experimental arrangement uses an imaging (two-dimensional) photomultiplier tube to produce a one-dimensional Raman profile of phase compositions along a slitlike laser beam without translation of either the sample or the laser beam and without scanning the spectrometer. Results from phase characterization studies of the size, frontal morphology, and extent of transformation of transformation zones surrounding cracks produced under monotonic and cyclic loading conditions are presented

Spin-orbit excitations and electronic structure of the putative Kitaev magnet $\\alpha$-RuCl$_3$

OpenAIRE

Sandilands, Luke J.; Tian, Yao; Reijnders, Anjan A.; Kim, Heung-Sik; Plumb, Kemp W.; Kee, Hae-Young; Kim, Young-June; Burch, Kenneth S.

2015-01-01

Mott insulators with strong spin-orbit coupling have been proposed to host unconventional magnetic states, including the Kitaev quantum spin liquid. The 4$d$ system $\\alpha$-RuCl$_3$ has recently come into view as a candidate Kitaev system, with evidence for unusual spin excitations in magnetic scattering experiments. We apply a combination of optical spectroscopy and Raman scattering to study the electronic structure of this material. Our measurements reveal a series of orbital excitations i...

A novel non-imaging optics based Raman spectroscopy device for transdermal blood analyte measurement

Directory of Open Access Journals (Sweden)

Chae-Ryon Kong

2011-09-01

Full Text Available Due to its high chemical specificity, Raman spectroscopy has been considered to be a promising technique for non-invasive disease diagnosis. However, during Raman excitation, less than one out of a million photons undergo spontaneous Raman scattering and such weakness in Raman scattered light often require highly efficient collection of Raman scattered light for the analysis of biological tissues. We present a novel non-imaging optics based portable Raman spectroscopy instrument designed for enhanced light collection. While the instrument was demonstrated on transdermal blood glucose measurement, it can also be used for detection of other clinically relevant blood analytes such as creatinine, urea and cholesterol, as well as other tissue diagnosis applications. For enhanced light collection, a non-imaging optical element called compound hyperbolic concentrator (CHC converts the wide angular range of scattered photons (numerical aperture (NA of 1.0 from the tissue into a limited range of angles accommodated by the acceptance angles of the collection system (e.g., an optical fiber with NA of 0.22. A CHC enables collimation of scattered light directions to within extremely narrow range of angles while also maintaining practical physical dimensions. Such a design allows for the development of a very efficient and compact spectroscopy system for analyzing highly scattering biological tissues. Using the CHC-based portable Raman instrument in a clinical research setting, we demonstrate successful transdermal blood glucose predictions in human subjects undergoing oral glucose tolerance tests.

Non-invasive in vivo determination of the carotenoids beta-carotene and lycopene concentrations in the human skin using the Raman spectroscopic method

International Nuclear Information System (INIS)

Darvin, M E; Gersonde, I; Meinke, M; Sterry, W; Lademann, J

2005-01-01

Resonance Raman spectroscopy was used as a fast and non-invasive optical method of measuring the absolute concentrations of beta-carotene and lycopene in living human skin. Beta-carotene and lycopene have different absorption values at 488 and 514.5 nm and, consequently, the Raman lines for beta-carotene and lycopene have different scattering efficiencies at 488 and 514.5 nm excitations. These differences were used for the determination of the concentrations of beta-carotene and lycopene. Using multiline Ar + laser excitation, clearly distinguishable carotenoid Raman spectra can be obtained which are superimposed on a large fluorescence background. The Raman signals are characterized by two prominent Stokes lines at 1160 and 1525 cm -1 , which have nearly identical relative intensities. Both substances were detected simultaneously. The Raman spectra are obtained rapidly, i.e. within about 10 s, and the required laser light exposure level is well within safety standards. The disturbance of the measurements by non-homogeneous skin pigmentation was avoided by using a relatively large measuring area of 35 mm 2 . It was shown that beta-carotene and lycopene distribution in human skin strongly depends upon the skin region studied and drastically changed inter-individually. Skin beta-carotene and lycopene concentrations are lower in smokers than in non-smokers and higher in the vegetarian group

Non-invasive in vivo determination of the carotenoids beta-carotene and lycopene concentrations in the human skin using the Raman spectroscopic method

Energy Technology Data Exchange (ETDEWEB)

Darvin, M E [Center of Experimental and Applied Cutaneous Physiology (CCP), Department of Dermatology, Charite University Hospital, Berlin (Germany); Gersonde, I [Institute of Medical Physics and Laser Medicine, Charite University Hospital, Berlin (Germany); Meinke, M [Institute of Medical Physics and Laser Medicine, Charite University Hospital, Berlin (Germany); Sterry, W [Center of Experimental and Applied Cutaneous Physiology (CCP), Department of Dermatology, Charite University Hospital, Berlin (Germany); Lademann, J [Center of Experimental and Applied Cutaneous Physiology (CCP), Department of Dermatology, Charite University Hospital, Berlin (Germany)

2005-08-07

Resonance Raman spectroscopy was used as a fast and non-invasive optical method of measuring the absolute concentrations of beta-carotene and lycopene in living human skin. Beta-carotene and lycopene have different absorption values at 488 and 514.5 nm and, consequently, the Raman lines for beta-carotene and lycopene have different scattering efficiencies at 488 and 514.5 nm excitations. These differences were used for the determination of the concentrations of beta-carotene and lycopene. Using multiline Ar{sup +} laser excitation, clearly distinguishable carotenoid Raman spectra can be obtained which are superimposed on a large fluorescence background. The Raman signals are characterized by two prominent Stokes lines at 1160 and 1525 cm{sup -1}, which have nearly identical relative intensities. Both substances were detected simultaneously. The Raman spectra are obtained rapidly, i.e. within about 10 s, and the required laser light exposure level is well within safety standards. The disturbance of the measurements by non-homogeneous skin pigmentation was avoided by using a relatively large measuring area of 35 mm{sup 2}. It was shown that beta-carotene and lycopene distribution in human skin strongly depends upon the skin region studied and drastically changed inter-individually. Skin beta-carotene and lycopene concentrations are lower in smokers than in non-smokers and higher in the vegetarian group.

Theory of Raman scattering in coupled electron-phonon systems

Science.gov (United States)

Itai, K.

1992-01-01

The Raman spectrum is calculated for a coupled conduction-electron-phonon system in the zero-momentum-transfer limit. The Raman scattering is due to electron-hole excitations and phonons as well. The phonons of those branches that contribute to the electron self-energy and the correction of the electron-phonon vertex are assumed to have flat energy dispersion (the Einstein phonons). The effect of electron-impurity scattering is also incorporated. Both the electron-phonon interaction and the electron-impurity interaction cause the fluctuation of the electron distribution between different parts of the Fermi surface, which results in overdamped zero-sound modes of various symmetries. The scattering cross section is obtained by solving the Bethe-Salpeter equation. The spectrum shows a lower threshold at the smallest Einstein phonon energy when only the electron-phonon interaction is taken into consideration. When impurities are also taken into consideration, the threshold disappears.

Laser-Induced, Local Oxidation of Copper Nanoparticle Films During Raman Measurements

Science.gov (United States)

Hight Walker, Angela R.; Cheng, Guangjun; Calizo, Irene

2011-03-01

The optical properties of gold and silver nanoparticles and their films have been thoroughly investigated as surface enhanced Raman scattering (SERS) substrates and chemical reaction promoters. Similar to gold and silver nanoparticles, copper nanoparticles exhibit distinct plasmon absorptions in the visible region. The work on copper nanoparticles and their films is limited due to their oxidization in air. However, their high reactivity actually provides an opportunity to exploit the laser-induced thermal effect and chemical reactions of these nanoparticles. Here, we present our investigation of the local oxidation of a copper nanoparticle film induced by a visible laser source during Raman spectroscopic measurements. The copper nanoparticle film is prepared by drop-casting chemically synthesized copper colloid onto silicon oxide/silicon substrate. The local oxidation induced by visible lasers in Raman spectroscopy is monitored with the distinct scattering peaks for copper oxides. Optical microscopy and scanning electron microscopy have been used to characterize the laser-induced morphological changes in the film. The results of this oxidation process with different excitation wavelengths and different laser powers will be presented.

Raman spectroscopy

Science.gov (United States)

Raman spectroscopy has gained increased use and importance in recent years for accurate and precise detection of physical and chemical properties of food materials, due to the greater specificity and sensitivity of Raman techniques over other analytical techniques. This book chapter presents Raman s...

Mechanism for the Excited-State Multiple Proton Transfer Process of Dihydroxyanthraquinone Chromophores.

Science.gov (United States)

Zhou, Qiao; Du, Can; Yang, Li; Zhao, Meiyu; Dai, Yumei; Song, Peng

2017-06-22

The single and dual cooperated proton transfer dynamic process in the excited state of 1,5-dihydroxyanthraquinone (1,5-DHAQ) was theoretically investigated, taking solvent effects (ethanol) into account. The absorption and fluorescence spectra were simulated, and dual fluorescence exhibited, which is consistent with previous experiments. Analysis of the calculated IR and Raman vibration spectra reveals that the intramolecular hydrogen bonding interactions (O 20 -H 21 ···O 24 and O 22 -H 23 ···O 25 ) are strengthened following the excited proton transfer process. Finally, by constructing the potential energy surfaces of the ground state, first excited singlet state, and triplet state, the mechanism of the intramolecular proton transfer of 1,5-DHAQ can be revealed.

Raman Signatures of Polytypism in Molybdenum Disulfide.

Science.gov (United States)

Lee, Jae-Ung; Kim, Kangwon; Han, Songhee; Ryu, Gyeong Hee; Lee, Zonghoon; Cheong, Hyeonsik

2016-02-23

Since the stacking order sensitively affects various physical properties of layered materials, accurate determination of the stacking order is important for studying the basic properties of these materials as well as for device applications. Because 2H-molybdenum disulfide (MoS2) is most common in nature, most studies so far have focused on 2H-MoS2. However, we found that the 2H, 3R, and mixed stacking sequences exist in few-layer MoS2 exfoliated from natural molybdenite crystals. The crystal structures are confirmed by HR-TEM measurements. The Raman signatures of different polytypes are investigated by using three different excitation energies that are nonresonant and resonant with A and C excitons, respectively. The low-frequency breathing and shear modes show distinct differences for each polytype, whereas the high-frequency intralayer modes show little difference. For resonant excitations at 1.96 and 2.81 eV, distinct features are observed that enable determination of the stacking order.

Evidence of localized amorphous silicon clustering from Raman depth-probing of silicon nanocrystals in fused silica

International Nuclear Information System (INIS)

Barba, D; Martin, F; Ross, G G

2008-01-01

Silicon nanocrystals (Si-nc) and amorphous silicon (α-Si) produced by silicon implantation in fused silica have been studied by micro-Raman spectroscopy. Information regarding the Raman signature of the α-Si phonon excitation was extracted from Raman depth-probing measurements using the phenomenological phonon confinement model. The spectral deconvolution of the Raman measurements recorded at different laser focusing depths takes into account both the Si-nc size variation and the Si-nc spatial distribution within the sample. The phonon peak associated with α-Si around 470 cm -1 is greatest for in-sample laser focusing, indicating that the formation of amorphous silicon is more important in the region containing a high concentration of silicon excess, where large Si-nc are located. As also observed for Si-nc systems prepared by SiO x layer deposition, this result demonstrates the presence of α-Si in high excess Si implanted Si-nc systems

Excitation of autoionizing states of helium by 100 keV proton impact: II. Excitation cross sections and mechanisms of excitation

Energy Technology Data Exchange (ETDEWEB)

Godunov, A.L. [Department of Physics, Tulane University, New Orleans, LA 70118-5698 (United States); Ivanov, P.B.; Schipakov, V.A. [Troitsk Institute of Innovation and Fusion Research Troitsk, Moscow region, 142092 (Russian Federation); Moretto-Capelle, P.; Bordenave-Montesquieu, D.; Bordenave-Montesquieu, A. [Laboratoire Collisions, Agregats, Reactivite, IRSAMC, UMR 5589, CNRS-Universite Paul Sabatier, 31062 Toulouse Cedex (France)

2000-03-14

Mechanisms of two-electron excitation of the (2s{sup 2}){sup 1} S, (2p{sup 2} ){sup 1} D and (2s2p){sup 1} P autoionizing states of helium are studied both experimentally and theoretically. It is shown that an explicit introduction of a kinematic factor, with a process-specific phase leads to a productive parametrization of experimental cross sections of ionization, allowing one to extract cross sections of excitation of autoionizing states. Using a new fitting procedure together with the proposed parametrization made it possible to obtain the excitation cross sections and magnetic sublevel population from electron spectra as well as, for the first time, to resolve the contribution of resonance and interference components to resonance profiles. Interference with direct ionization is shown to contribute significantly into resonance formation even for backward ejection angles. We demonstrate theoretically that the excitation cross sections thus extracted from experimental electron spectra hold information about the interaction of autoionizing states with an adjacent continuum. (author)

Two-Dimensional Raman Correlation Analysis of Diseased Esophagus in a Rat

Science.gov (United States)

Takanezawa, Sota; Morita, Shin-ichi; Maruyama, Atsushi; Murakami, Takurou N.; Kawashima, Norimichi; Endo, Hiroyuki; Iijima, Katsunori; Asakura, Tohru; Shimosegawa, Tooru; Sato, Hidetoshi

2010-07-01

Generalized two-dimensional (2D) Raman correlation analysis effectively distinguished a benign tumor from normal tissue. Line profiling Raman spectra of a rat esophagus, including a benign tumor, were measured and the generalized 2D synchronous and asynchronous spectra were calculated. In the autocorrelation area of the amide I band of proteins in the asynchronous map, a cross-like pattern was observed. A simulation study indicated that the pattern was caused by a sharp band component in the amide I band region. We considered that the benign tumor corresponded to the sharp component.

Hyper-Rayleigh scattering and hyper-Raman scattering of dye-adsorbed silver nanoparticles induced by a focused continuous-wave near-infrared laser

International Nuclear Information System (INIS)

Itoh, Tamitake; Ozaki, Yukihiro; Yoshikawa, Hiroyuki; Ihama, Takashi; Masuhara, Hiroshi

2006-01-01

We report that hyper-Rayleigh scattering, surface-enhanced hyper-Raman scattering, and two-photon excited luminescence occur intermittently by focusing a continuous-wave near-infrared (cw-NIR) laser into a colloidal silver solution including rhodamine 6G (R6G) and sodium chloride (NaCl). On the other hand, continuous hyper-Rayleigh scattering is observed from colloidal silver free from R6G and NaCl, demonstrating that hyper-Raman scattering and two-photon excited luminescence are attributed to R6G and their intermittent features are dependent on the colloidal dispersion. These results suggest that the cw-NIR laser has three roles; the source of the nonlinear response, optical trapping of nanoparticles, and making nanoparticle aggregates possessing the high activity for the nonlinear response

Raman Plus X: Biomedical Applications of Multimodal Raman Spectroscopy.

Science.gov (United States)

Das, Nandan K; Dai, Yichuan; Liu, Peng; Hu, Chuanzhen; Tong, Lieshu; Chen, Xiaoya; Smith, Zachary J

2017-07-07

Raman spectroscopy is a label-free method of obtaining detailed chemical information about samples. Its compatibility with living tissue makes it an attractive choice for biomedical analysis, yet its translation from a research tool to a clinical tool has been slow, hampered by fundamental Raman scattering issues such as long integration times and limited penetration depth. In this review we detail the how combining Raman spectroscopy with other techniques yields multimodal instruments that can help to surmount the translational barriers faced by Raman alone. We review Raman combined with several optical and non-optical methods, including fluorescence, elastic scattering, OCT, phase imaging, and mass spectrometry. In each section we highlight the power of each combination along with a brief history and presentation of representative results. Finally, we conclude with a perspective detailing both benefits and challenges for multimodal Raman measurements, and give thoughts on future directions in the field.

Resonant Inelastic X-ray Scattering: From band mapping to inter-orbital excitations

International Nuclear Information System (INIS)

Luning, J.; Hague, C.F.

2008-01-01

Resonant inelastic X-ray scattering (also known as resonant X-ray Raman spectroscopy when only valence and conduction states are involved in the final state excitation) has developed into a major tool for understanding the electronic properties of complex materials. Presently it provides access to electron excitations in the few hundred meV range with element and bulk selectivity. Recent progress in X-ray optics and synchrotron radiation engineering have opened up new perspectives for this powerful technique to improve resolving power and efficiency. We briefly present the basics of the method and illustrate its potential with examples chosen from the literature. (authors)

Pressure-induced crystallization and phase transformation of amorphous selenium: Raman spectroscopy and x-ray diffraction studies

International Nuclear Information System (INIS)

Yang Kaifeng; Cui Qiliang; Hou Yuanyuan; Liu Bingbing; Zhou Qiang; Hu Jingzhu; Mao, H-K; Zou Guangtian

2007-01-01

High-pressure Raman spectroscopy studies have been carried out on amorphous Se (a-Se) at room temperature in a diamond anvil cell with an 830 nm exciting line. Raman evidence for the pressure-induced crystallization of a-Se and the coexistence of the unknown high-pressure phase with the hexagonal phase is presented for the first time. Further experimental proof of high-pressure angle-dispersive x-ray diffraction studies for a-Se indicates that the unknown high-pressure phase is also a mixture phase of the tetragonal I4 1 /acd and Se IV structure. Our Raman and x-ray diffraction results suggest that hexagonal Se I undergoes a direct transition to triclinic Se III at about 19 GPa, which is in good agreement with the theoretical prediction

Investigation of L(+)-Ascorbic Acid with Raman Spectroscopy in Visible and UV Light

DEFF Research Database (Denmark)

Berg, Rolf W.

2015-01-01

Abstract: Raman spectroscopy investigations of l(+)-ascorbic acid and its mono- and di-deprotonated anions (AH(-) and A(2-)) are reviewed and new measurements reported with several wavelengths, 229, 244, 266, 488, and 532nm. Results are interpreted, assisted by new DFT/B3LYP quantum chemical calc......). Relatively weak preresonance enhancement was seen for A(2-) when excitation was done with 229nm UV light, allowing water bands to become observable as for normal visible light Raman spectra....... calculations with 6-311++G(d,p) basis sets for several conformations of ascorbic acid and the anions. Raman spectra were measured during titration with NaOH base in an oxygen-poor environment to avoid fluorescence when solutions were alkaline. The ultraviolet (UV) absorption band for ascorbic acid in aqueous......cm(-1). Finally, for the ascorbate di-anion, absorption was found at similar to 298.4nm with molar absorptivity of similar to 7,000 L mol(-1) cm(-1) and below similar to 220nm. With UV light (244 and 266nm), strongly basic solutions gave pronounced Raman resonance enhancement at similar to 1556cm(-1...

Micro-Raman investigations of InN-GaN core-shell nanowires on Si (111) substrate

Energy Technology Data Exchange (ETDEWEB)

Sangeetha, P.; Ramakrishnan, V. [Department of Laser Studies, School of Physics, Madurai Kamaraj University, Madurai-625 021 (India); Jeganathan, K. [Centre for Nanoscience and Nanotechnology, School of Physics, Bharathidasan University, Tiruchirappalli-620 024 (India)

2013-06-15

The electron-phonon interactions in InN-GaN core-shell nanowires grown by plasma assisted- molecular beam epitaxy (MBE) on Si (111) substrate have been analysed using micro-Raman spectroscopic technique with the excitation wavelength of 633, 488 and 325 nm. The Raman scattering at 633 nm reveals the characteristic E{sub 2} (high) and A{sub 1} (LO) phonon mode of InN core at 490 and 590 cm{sup -1} respectively and E{sub 2} (high) phonon mode of GaN shell at 573 cm{sup -1}. The free carrier concentration of InN core is found to be low in the order {approx} 10{sup 16} cm{sup -3} due to the screening of charge carriers by thin GaN shell. Diameter of InN core evaluated using the spatial correlation model is consistent with the transmission electron microscopic measurement of {approx}15 nm. The phonon-life time of core-shell nanowire structure is estimated to be {approx}0.4 ps. The micro-Raman mapping and its corresponding localised spectra for 325 nm excitation exhibit intense E{sub 2} (high) phonon mode of GaN shell at 573 cm{sup -1} as the decrease of laser interaction length and the signal intensity is quenched at the voids due to high spacing of NWs.

"Anomalous" excitation in hydrogen-bonded molecular crystals - a Raman scattering study of specifically deuterated acetanilide (C 6D 5-CONH-CD 3)

Science.gov (United States)

Sauvajol, J. L.; De Nunzio, G.; Almairac, R.; Moret, J.; Barthés, M.; Bataillon, Place E.

1991-01-01

The focus of experimental and theoretical works about crystalline Acetanilide has been the "anomalous" temperature-dependent ir absorption and Raman peaks at about 1650 cm -1 and the multiband structure in the N-H stretch region. A lively discussion about the assignment of these "anomalous" bands has arisen and is still in progress. The present Raman experiments should be placed in this context as an attempt to identify the molecular degrees of freedom which originate the "anomalous" bands. In this aim Raman experiments have been performed on specifically deuterated Acetanilide [C 6D 5-CONH-CD 3] single crystal in the low-frequency (phonon) and C=O stretching regions. On cooling a distinct band at about 1495 cm -1 increases in intensity. We assign this peak to the equivalent of the 1650 cm -1 band in Acetanilide. The temperature dependence of this Raman line was studied. The results are discussed in the light of the models proposed to explain the anomalous behaviour of the 1650 cm -1 Raman line in Acetanilide.

Depth profiling of calcifications in breast tissue using picosecond Kerr-gated Raman spectroscopy.

Science.gov (United States)

Baker, Rebecca; Matousek, Pavel; Ronayne, Kate Louise; Parker, Anthony William; Rogers, Keith; Stone, Nicholas

2007-01-01

Breast calcifications are found in both benign and malignant lesions and their composition can indicate the disease state. Calcium oxalate (dihydrate) (COD) is associated with benign lesions, however calcium hydroxyapatite (HAP) is found mainly in proliferative lesions including carcinoma. The diagnostic practices of mammography and histopathology examine the morphology of the specimen. They can not reliably distinguish between the two types of calcification, which may indicate the presence of a cancerous lesion during mammography. We demonstrate for the first time that Kerr-gated Raman spectroscopy is capable of non-destructive probing of sufficient biochemical information from calcifications buried within tissue, and this information can potentially be used as a first step in identifying the type of lesion. The method uses a picosecond pulsed laser combined with fast temporal gating of Raman scattered light to enable spectra to be collected from a specific depth within scattering media by collecting signals emerging from the sample at a given time delay following the laser pulse. Spectra characteristic of both HAP and COD were obtained at depths of up to 0.96 mm, in both chicken breast and fatty tissue; and normal and cancerous human breast by utilising different time delays. This presents great potential for the use of Raman spectroscopy as an adjunct to mammography in the early diagnosis of breast cancer.

Scanning angle Raman spectroscopy: Investigation of Raman scatter enhancement techniques for chemical analysis

Energy Technology Data Exchange (ETDEWEB)

Meyer, Matthew W. [Iowa State Univ., Ames, IA (United States)

2013-01-01

This thesis outlines advancements in Raman scatter enhancement techniques by applying evanescent fields, standing-waves (waveguides) and surface enhancements to increase the generated mean square electric field, which is directly related to the intensity of Raman scattering. These techniques are accomplished by employing scanning angle Raman spectroscopy and surface enhanced Raman spectroscopy. A 1064 nm multichannel Raman spectrometer is discussed for chemical analysis of lignin. Extending dispersive multichannel Raman spectroscopy to 1064 nm reduces the fluorescence interference that can mask the weaker Raman scattering. Overall, these techniques help address the major obstacles in Raman spectroscopy for chemical analysis, which include the inherently weak Raman cross section and susceptibility to fluorescence interference.

Raman study of InAs/InP quantum wires

Science.gov (United States)

Angelova, T.; Cros, A.; Cantarero, A.; Fuster, D.; González, Y.; González, L.

2007-04-01

We present a Raman study of the vibrational modes in InAs/InP (001) quantum wires. The energy of the observed phonon modes evidences the confinement properties of the wires, their strain anisotropy and the effect of atomic intermixing. Resonance effects in confined and interface phonons are discussed for excitation in the vicinity of the E1 critical point. The observed vibrations and their variation with sample characteristics are in agreement with the conclusions of previous structural and optical characterization performed in the same samples.

Raman lidar for remote control explosives in the subway

Science.gov (United States)

Grishkanich, Aleksandr; Redka, Dmitriy; Vasiliev, Sergey; Tishkov, Victor; Zhevlakov, Aleksandr

2017-10-01

Laser sensing can serve as a highly effective method of searching and monitoring of explosives in the subway. The first method is essence consists in definition the explosives concentration by excitation and registration ramans shifts at wavelength of λ = 0.261 - 0.532 μm at laser sounding. Preliminary results of investigation show the real possibility to register of 2,4,6-trinitrophenylmethylnitramine with concentration on surface at level of 108÷109 cm-3 on a safe distance 50 m from the object.

Spectral watermarking in femtosecond stimulated Raman spectroscopy: resolving the nature of the carotenoid S-star state

Czech Academy of Sciences Publication Activity Database

Kloz, Miroslav; Weissenborn, J.; Polívka, T.; Frank, H.A.; Kennis, J.T.M.

2016-01-01

Roč. 18, č. 21 (2016), s. 14619-14628 ISSN 1463-9076 R&D Projects: GA MŠk EF15_008/0000162; GA MŠk LQ1606 Grant - others:ELI Beamlines(XE) CZ.02.1.01/0.0/0.0/15_008/0000162 Institutional support: RVO:68378271 Keywords : beta-carotene * excited-state * ultrafast dynamics * resonance Raman * excitation * conversion * pathway * laser * S-1 Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 4.123, year: 2016

Raman Lidar Profiles–Temperature (RLPROFTEMP) Value-Added Product

Energy Technology Data Exchange (ETDEWEB)

Newsom, RK; Sivaraman, C; McFarlane, SA

2012-10-31

The purpose of this document is to describe the Raman Lidar Profiles–Temperature (RLPROFTEMP) value-added product (VAP) and the procedures used to derive atmospheric temperature profiles from the raw RL measurements. Sections 2 and 4 describe the input and output variables, respectively. Section 3 discusses the theory behind the measurement and the details of the algorithm, including calibration and overlap correction.

A Study on the use of Gafchromic{sup TM} EBT3 Film for Microdosimetry by Raman Spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Mirza, Jamal Ahmad; Heo, Taemin; Park, Hyeonsuk; Ye, Sung-Joon [Seoul National University, Seoul (Korea, Republic of)

2015-10-15

This concept is explained in microdosimetry, which deals with the spatial, temporal and energy spectral distributions of energy imparted in cellular and subcellular biological structures and associated biological effects. We at Seoul National University (SNU) are investigating on the use of unlaminated Gafchromic{sup TM} EBT3 film for microdosimetry. Our goal is to determine absorbed dose on EBT3 film with spatial distribution of as low as 10 micron using Raman spectroscopy. Data acquired using Raman is reproducible and temporally stable. Proper placement of film on stage and with right orientation is very important. The peak saturation problem can be avoided by decreasing laser exposure time. Raman intensity decreases with increase or decrease of depths beyond the surface active layer. Depth profile of film for each dose level maybe used to find the maximum signal, which is useful in finding the dose profile. Raman spectroscopy can be used for the determination of absorbed dose by exploiting the idea that C ≡ C and/or C=C in EBT3 film increases with increasing dose due to polymerization of diacetylene monomer.

Raman Lidar Calibration for the DMSP SSM/T-2 Microwave Water Vapor Sensor

National Research Council Canada - National Science Library

Wessel, J

2000-01-01

Campaigns were conducted at the Pacific Missile Range Facility, Barking Sands, Kauai, investigating Raman lidar as a method to improve calibration of the DMSP SSM/T-2 microwave water vapor profiling instrument...

Near-infrared Raman spectroscopy for assessing biochemical changes of cervical tissue associated with precarcinogenic transformation.

Science.gov (United States)

Duraipandian, Shiyamala; Mo, Jianhua; Zheng, Wei; Huang, Zhiwei

2014-11-07

Raman spectroscopy measures the inelastically scattered light from tissue that is capable of identifying native tissue biochemical constituents and their changes associated with disease transformation. This study aims to characterize the Raman spectroscopic properties of cervical tissue associated with the multi-stage progression of cervical precarcinogenic sequence. A rapid-acquisition fiber-optic near-infrared (NIR) Raman diagnostic system was employed for tissue Raman spectral measurements at 785 nm excitation. A total of 68 Raman spectra (23 benign, 29 low-grade squamous intraepithelial lesions (LSIL) and 16 high grade squamous intraepithelial lesions (HSIL)) were measured from 25 cervical tissue biopsy specimens, as confirmed by colposcopy-histopathology. The semi-quantitative biochemical modeling based on the major biochemicals (i.e., DNA, proteins (histone, collagen), lipid (triolein) and carbohydrates (glycogen)) in cervical tissue uncovers the stepwise accumulation of biomolecular changes associated with progressive cervical precarcinogenesis. Multi-class partial least squares-discriminant analysis (PLS-DA) together with leave-one tissue site-out, cross-validation yielded the diagnostic sensitivities of 95.7%, 82.8% and 81.3%; specificities of 100.0%, 92.3% and 88.5%,for discrimination among benign, LSIL and HSIL cervical tissues, respectively. This work suggests that the Raman spectral biomarkers have identified the potential to be used for monitoring the multi-stage cervical precarcinogenesis, forming the foundation of applying NIR Raman spectroscopy for the early diagnosis of cervical precancer in vivo at the molecular level.

In vivo Raman spectroscopy for biochemical monitoring of the human cervix throughout pregnancy.

Science.gov (United States)

O'Brien, Christine M; Vargis, Elizabeth; Rudin, Amy; Slaughter, James C; Thomas, Giju; Newton, J Michael; Reese, Jeff; Bennett, Kelly A; Mahadevan-Jansen, Anita

2018-05-01

The cervix must undergo significant biochemical remodeling to allow for successful parturition. This process is not fully understood, especially in instances of spontaneous preterm birth. In vivo Raman spectroscopy is an optical technique that can be used to investigate the biochemical composition of tissue longitudinally and noninvasively in human beings, and has been utilized to measure physiology and disease states in a variety of medical applications. The purpose of this study is to measure in vivo Raman spectra of the cervix throughout pregnancy in women, and to identify biochemical markers that change with the preparation for delivery and postpartum repair. In all, 68 healthy pregnant women were recruited. Raman spectra were measured from the cervix of each patient monthly in the first and second trimesters, weekly in the third trimester, and at the 6-week postpartum visit. Raman spectra were measured using an in vivo Raman system with an optical fiber probe to excite the tissue with 785 nm light. A spectral model was developed to highlight spectral regions that undergo the most changes throughout pregnancy, which were subsequently used for identifying Raman peaks for further analysis. These peaks were analyzed longitudinally to determine if they underwent significant changes over the course of pregnancy (P Raman peaks indicative of extracellular matrix proteins (1248 and 1254 cm -1 ) significantly decreased (P Raman spectroscopy was successfully used to biochemically monitor cervical remodeling in pregnant women during prenatal visits. This foundational study has demonstrated sensitivity to known biochemical dynamics that occur during cervical remodeling, and identified patient variables that have significant effects on Raman spectra throughout pregnancy. Raman spectroscopy has the potential to improve our understanding of cervical maturation, and be used as a noninvasive preterm birth risk assessment tool to reduce the incidence, morbidity, and mortality

Probing Pharmaceutical Mixtures during Milling: The Potency of Low-Frequency Raman Spectroscopy in Identifying Disorder.

Science.gov (United States)

Walker, Greg; Römann, Philipp; Poller, Bettina; Löbmann, Korbinian; Grohganz, Holger; Rooney, Jeremy S; Huff, Gregory S; Smith, Geoffrey P S; Rades, Thomas; Gordon, Keith C; Strachan, Clare J; Fraser-Miller, Sara J

2017-12-04

This study uses a multimodal analytical approach to evaluate the rates of (co)amorphization of milled drug and excipient and the effectiveness of different analytical methods in detecting these changes. Indomethacin and tryptophan were the model substances, and the analytical methods included low-frequency Raman spectroscopy (785 nm excitation and capable of measuring both low- (10 to 250 cm -1 ) and midfrequency (450 to 1800 cm -1 ) regimes, and a 830 nm system (5 to 250 cm -1 )), conventional (200-3000 cm -1 ) Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), and X-ray powder diffraction (XRPD). The kinetics of amorphization were found to be faster for the mixture, and indeed, for indomethacin, only partial amorphization occurred (after 360 min of milling). Each technique was capable of identifying the transformations, but some, such as low-frequency Raman spectroscopy and XRPD, provided less ambiguous signatures than the midvibrational frequency techniques (conventional Raman and FTIR). The low-frequency Raman spectra showed intense phonon mode bands for the crystalline and cocrystalline samples that could be used as a sensitive probe of order. Multivariate analysis has been used to further interpret the spectral changes. Overall, this study demonstrates the potential of low-frequency Raman spectroscopy, which has several practical advantages over XRPD, for probing (dis-)order during pharmaceutical processing, showcasing its potential for future development, and implementation as an in-line process monitoring method.

Large Variations of the Raman Signal in the Spectra of Twisted Bilayer Graphene on a BN Substrate.

Science.gov (United States)

Kalbac, Martin; Frank, Otakar; Kong, Jing; Sanchez-Yamagishi, Javier; Watanabe, Kenji; Taniguchi, Takashi; Jarillo-Herrero, Pablo; Dresselhaus, Mildred S

2012-03-15

We report an unusual enhancement of the Raman signal of the G mode in a twisted graphene bilayer (2-LG) on a hexagonal single-crystalline boron nitride substrate. We used an isotopically engineered 2-LG, where the top layer was composed of (13)C atoms and the bottom layer of (12)C atoms. Consequently, it was possible by Raman spectroscopy to distinguish between the enhancement coming from the top and bottom layers. The enhancement of the G mode was, however, found to be similar for the top and bottom layers, and this enhancement effect was observed only at certain locations on the substrate. The experiment with two different laser excitation energies showed that the location of the enhanced spots is dependent on the laser excitation energy. Therefore our results suggest that the enhancement comes from new states in the electronic structure, which are a consequence of a local specific rotation of the grains in graphene layers.

Imaging chemical interfaces perpendicular to the optical axis with focus-engineered coherent anti-Stokes Raman scattering microscopy

International Nuclear Information System (INIS)

Krishnamachari, Vishnu Vardhan; Potma, Eric Olaf

2007-01-01

In vibrational microscopy, it is often necessary to distinguish between chemically distinct microscopic objects and to highlight the 'chemical interfaces' present in the sample under investigation. Here we apply the concept of focus engineering to enhance the sensitivity of coherent anti-Stokes Raman scattering (CARS) microscopy to these interfaces. Based on detailed numerical simulations, we show that using a focused Stokes field with a sharp phase jump along the longitudinal direction leads to the suppression of the signal from bulk regions and improves the signal contrast from vibrational resonant interfaces oriented perpendicular to the axis of beam propagation. We also demonstrate that the CARS spectral response from chemical interfaces exhibits a clean, Raman-like band-shape with such a phase-shaped excitation. This phenomenon of interface highlighting is a consequence of the coherent nature of CARS signal generation and it involves a complex interplay of the spectral phase of the sample and the spatial phase of the excitation fields

Macro and micro Raman spectroscopy of YBa2Cu3O7 films and microbridges

International Nuclear Information System (INIS)

Bock, A.

1993-01-01

In the present work Raman spectroscopy is used as a method to characterize the properties of YBa 2 Cu 3 O 7 -films. This is done in the usual (macro-)Raman set-up as well as in the micro-Raman set-up where the spatial resolution is about one micron. To obtain comparable results the Raman spectra have to be corrected for the spectral response of the spectrometer. Therefore a calibration of the set-up was performed. The calibration can be used to determine spot temperatures by comparing Stokes and Anti-Stokes spectra. Two different methods are developed to correct for the straylight which is additionally observed in Raman-spectra of YBa 2 Cu 3 O 7 -films. Macro- as well as micro-Raman measurements are used to characterize the film properties, where care has been taken to avoid damages by the laser itself. The macro-Raman set-up is used to identify the properties of the film, such as orientation, oxygen-content and morphology. Outgrowths and other particles on the surface are on the other hand investigated by micro-Raman spectroscopy. The surface morphology is additionally characterized by scanning-electron-microscopy. This is compared to the Raman data. Raman spectra of epitaxial YBa 2 Cu 3 O 7 -films are taken as a function of the temperature and exciting wavelength. The influence on the phonons and on the electronic background is discussed separately. The obtained results are analyzed by comparison with single-crystal measurements. The investigation of YBa 2 Cu 3 O 7 -microbridges in the macro-Raman set-up allows a correlation between the local optical and electrical properties of the bridge. A method is presented which can account for the heating in the laser spot with high accuracy. This method allows to determine local critical current densities as well as local critical temperatures on the microbridge. It provides also the possibility to take Raman spectra at precise spot temperatures. (orig./WL)

Multi-metal, Multi-wavelength Surface-Enhanced Raman Spectroscopy Detection of Neurotransmitters.

Science.gov (United States)

Moody, Amber S; Sharma, Bhavya

2018-04-05

The development of a sensor for the rapid and sensitive detection of neurotransmitters could provide a pathway for the diagnosis of neurological diseases, leading to the discovery of more effective treatment methods. We investigate the use of surface enhanced Raman spectroscopy (SERS) based sensors for the rapid detection of melatonin, serotonin, glutamate, dopamine, GABA, norepinephrine, and epinephrine. Previous studies have demonstrated SERS detection of neurotransmitters; however, there has been no comprehensive study on the effect of the metal used as the SERS substrate or the excitation wavelength used for detection. Here, we present the detection of 7 neurotransmitters using both silver and gold nanoparticles at excitation wavelengths of 532, 633, and 785 nm. Over the range of wavelengths investigated, the SERS enhancement on the silver and gold nanoparticles varies, with an average enhancement factor of 10 5 -10 6 . The maximum SERS enhancement occurs at an excitation wavelength of 785 nm for the gold nanoparticles and at 633 nm for the silver nanoparticles.

Micro-Raman and micro-photoluminescence study of bio-conjugated core–shell CdSe/ZnS nanocrystals

Energy Technology Data Exchange (ETDEWEB)

Borkovska, L., E-mail: bork@isp.kiev.ua [V. Lashkaryov Institute of Semiconductor Physics of NASU, pr. Nauky 41, 03028 Kyiv (Ukraine); Korsunska, N.; Stara, T.; Kolomys, O.; Strelchuk, V. [V. Lashkaryov Institute of Semiconductor Physics of NASU, pr. Nauky 41, 03028 Kyiv (Ukraine); Rachkov, O. [The Institute of Molecular Biology and Genetics of NASU, Zabolotnogo Str. 150, 03680 Kyiv (Ukraine); Kryvko, A. [Instituto Politécnico Nacional – ESIME, Av. IPN, Ed. Z4, U.P.A.L.M., 07738 Mexico D.F. (Mexico)

2014-11-15

The micro-Raman and micro-photoluminescence spectra of non-conjugated and conjugated with antibody against S6K2 commercial CdSe/ZnS quantum dots (QDs) were investigated under different excitation wavelengths and at different temperatures. In the photoluminescence (PL) spectra, the additional PL band shifted on 0.6–0.65 eV to higher energies from the CdSe/ZnS QD exciton PL band is revealed. The relative intensity of this band is found to be several times larger in bio-conjugated QDs, than in the non-conjugated ones. The characteristics of both PL bands (the PL intensity, spectral position and half-width of the PL band) vary similarly under continuous laser light irradiation, storage of the QD samples in the atmospheric ambience as well as during the temperature change. In the Raman spectra recorded under excitation resonant with the high-energy PL band, the additional Raman peaks at about 300 cm{sup −1} and 600 cm{sup −1}, which are close to the frequency of LO and 2LO phonons of bulk CdS, are found. It is proposed that alloyed QDs with chemical composition close to CdS are responsible for the additional high-energy PL band. The possible reasons for the formation of the alloyed QDs are discussed.

Water-Vapor Raman Lidar System Reaches Higher Altitude

Science.gov (United States)

Leblanc, Thierry; McDermid, I. Stewart

2010-01-01

A Raman lidar system for measuring the vertical distribution of water vapor in the atmosphere is located at the Table Mountain Facility (TMF) in California. Raman lidar systems for obtaining vertical water-vapor profiles in the troposphere have been in use for some time. The TMF system incorporates a number of improvements over prior such systems that enable extension of the altitude range of measurements through the tropopause into the lower stratosphere. One major obstacle to extension of the altitude range is the fact that the mixing ratio of water vapor in the tropopause and the lower stratosphere is so low that Raman lidar measurements in this region are limited by noise. Therefore, the design of the TMF system incorporates several features intended to maximize the signal-to-noise ratio. These features include (1) the use of 355-nm-wavelength laser pulses having an energy (0.9 J per pulse) that is high relative to the laser-pulse energy levels of prior such systems, (2) a telescope having a large aperture (91 cm in diameter) and a narrow field of view (angular width .0.6 mrad), and (3) narrow-bandpass (wavelength bandwidth 0.6 nm) filters for the water-vapor Raman spectral channels. In addition to the large-aperture telescope, three telescopes having apertures 7.5 cm in diameter are used to collect returns from low altitudes.

Defining the temperature range for cooking with extra virgin olive oil using Raman spectroscopy

Science.gov (United States)

Ahmad, Naveed; Saleem, M.; Ali, H.; Bilal, M.; Khan, Saranjam; Ullah, Rahat; Ahmed, M.; Mahmood, S.

2017-09-01

Using the potential of Raman spectroscopy, new findings regarding the effects of heating on extra virgin olive oil (EVOO) during frying/cooking are presented. A temperature range from 140 to 150 °C has been defined within which EVOO can be used for cooking/frying without much loss of its natural molecular composition. Raman spectra from the EVOO samples were recorded using an excitation laser at 785 nm in the range from 540 to 1800 cm-1. Due to heating, prominent variations in intensity are observed at Raman bands from 540 to 770 cm-1, 790 to 1170 cm-1 and 1267 and 1302 cm-1. The Raman bands at 1267 and 1302 cm-1 represent cis unsaturated fats and their ratio is used to investigate the effects of temperature on the molecular composition of EVOO. In addition, principal component analysis has been applied on all the groups of data to classify the heated EVOO samples at different temperatures and for different times. In addition, it has been found that use of EVOO for frying twice does not have any prominent effect on its molecular composition.

Identification of bacteria causing acute otitis media using Raman microspectroscopy

Science.gov (United States)

Ayala, Oscar D.; Wakeman, Catherine A.; Skaar, Eric P.; Mahadevan-Jansen, Anita

2016-03-01

Otitis media (OM) is the leading cause of acute physician visits and prescription of antibiotics for children. Current standard techniques to diagnose acute otitis media (AOM) are limited by their ability to probe only changes in symptoms of the bacterial infection that cause AOM. Furthermore, they are not able to detect the presence of or identify bacteria causing AOM, which is important for diagnosis and proper antibiotic treatment. Our goal is to detect the presence of and identify the pathogens involved in causing AOM based on their biochemical profile using Raman spectroscopy (RS). An inVia confocal Raman microscope (Renishaw) at 785 nm was used to detect bacteria causing AOM in vitro. The three main bacteria that cause AOM, Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pneumoniae were cultured in chocolate agar and Mueller-Hinton agar to determine which agar type would minimize Raman signal from the growth agar. Preliminary results identified specific Raman spectral features characteristic of S. pneumoniae. RS has the potential to accurately diagnose AOM, which will help in identifying the antibiotic that will be most beneficial for the patient and ultimately decrease the course of infection.

Time resolved resonance Raman spectra of anilino radical and aniline radical cation

International Nuclear Information System (INIS)

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

1987-01-01

We report, in this paper, submicrosecond time resolved resonance Raman spectra of anilino radical and its radical cation as observed in pulse radiolytic studies of the oxidation of aniline in aqueous solution. By excitation in resonance with the broad and weak electronic transition of anilino radical at 400 nm (ε--1250 M -1 cm -1 ) we have observed, for the first time, the vibrational features of this radical. The Wilson ν 8 /sub a/ ring stretching mode at 1560 cm -1 is most strongly resonance enhanced. The ν 7 /sub a/ CN stretching band at 1505 cm -1 , which is shifted to higher frequency by 231 cm -1 with respect to aniline, is also prominent. The frequency of this latter mode indicates that the CN bond in the radical has considerable double bond character. The Raman spectrum of aniline radical cation, excited in resonance with the --425 nm electronic absorption (ε--4000 M -1 cm -1 ), shows features which are similar to phenoxyl radical. Most of the observed frequencies of this radical in solution are in good agreement with vibrational energies determined by recent laser photoelectron spectroscopic studies in the vapor phase. The bands most strongly enhanced in the resonance Raman spectrum are, however, weak in the photoelectron spectrum. While the vibrational frequencies observed for anilino radical and its isoelectronic cation are quite similar, the resonance enhancement patterns are very different. In particular the ν 14 b 2 mode of anilino radical observed at 1324 cm -1 is highly resonance enhanced because of strong vibronic coupling between the 400 nm 2 A 2 -- 2 B 1 and the higher 2 B 1 -- 2 B 1 electronic transitions

Thermally generated metals for plasmonic coloring and surface-enhanced Raman sensing

Science.gov (United States)

Huang, Zhenping; Chen, Jian; Liu, Guiqiang; Wang, Yan; Liu, Yi; Tang, Li; Liu, Zhengqi

2018-03-01

Spectral coloring glass and its application on the surface-enhanced Raman scattering are demonstrated experimentally via a simple and moderate heat-treating of the top ultrathin gold film to create discrete nanoparticles, which can produce localized surface plasmon resonances and strong plasmonic near-field coupling effects. Ultrathin metal films with a wide range of thicknesses are investigated by different heat-treatment processes. The annealed metal films have been demonstrated with a series of spectral coloring responses. Moreover, the microscopy images of the metal film structures confirm the formation of distinct geometry features in these operation procedures. Densely packed nanoparticles are observed for the ultrathin metal film with the single-digit level of thickness. With increasing the film thickness over 10 nm, metallic clusters and porous morphologies can be obtained. Importantly, the metallic resonators can provide enhanced Raman scattering with the detection limit down to 10 - 7 molL - 1 of Rhodamine 6G molecules due to the excitation of plasmon resonances and strong near-field coupling effects. These features hold great potential for large-scale and low-cost production of colored glass and Raman substrate.

Raman spectroscopy study of the doping effect of the encapsulated terbium halogenides on single-walled carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Kharlamova, M.V.; Kramberger, C.; Mittelberger, A. [University of Vienna, Faculty of Physics, Vienna (Austria)

2017-04-15

In the present work, the doping effect of terbium chloride, terbium bromide, and terbium iodide on single-walled carbon nanotubes (SWCNTs) was compared by Raman spectroscopy. A precise investigation of the doping-induced alterations of the Raman modes of the filled SWCNTs was conducted. The shifts of the components of the Raman modes and modification of their profiles allowed concluding that the inserted terbium halogenides have acceptor doping effect on the SWCNTs, and the doping efficiency increases in the line with terbium iodide, terbium bromide, and terbium chloride. (orig.)

Discrimination of Aspergillus lentulus from Aspergillus fumigatus by Raman spectroscopy and MALDI-TOF MS.

Science.gov (United States)

Verwer, P E B; van Leeuwen, W B; Girard, V; Monnin, V; van Belkum, A; Staab, J F; Verbrugh, H A; Bakker-Woudenberg, I A J M; van de Sande, W W J

2014-02-01

In 2005, a new sibling species of Aspergillus fumigatus was discovered: Aspergillus lentulus. Both species can cause invasive fungal disease in immune-compromised patients. The species are morphologically very similar. Current techniques for identification are PCR-based or morphology-based. These techniques are labour-intense and not sufficiently discriminatory. Since A. lentulus is less susceptible to several antifungal agents, it is important to correctly identify the causative infectious agent in order to optimize antifungal therapy. In this study we determined whether Raman spectroscopy and/or MALDI-TOF MS were able to differentiate between A. lentulus and A. fumigatus. For 16 isolates of A. lentulus and 16 isolates of A. fumigatus, Raman spectra and peptide profiles were obtained using the Spectracell and MALDI-TOF MS (VITEK MS RUO, bioMérieux) respectively. In order to obtain reliable Raman spectra for A. fumigatus and A. lentulus, the culture medium needed to be adjusted to obtain colourless conidia. Only Raman spectra obtained from colourless conidia were reproducible and correctly identified 25 out of 32 (78 %) of the Aspergillus strains. For VITEK MS RUO, no medium adjustments were necessary. Pigmented conidia resulted in reproducible peptide profiles as well in this case. VITEK MS RUO correctly identified 100 % of the Aspergillus isolates, within a timeframe of approximately 54 h including culture. Of the two techniques studied here, VITEK MS RUO was superior to Raman spectroscopy in the discrimination of A. lentulus from A. fumigatus. VITEK MS RUO seems to be a successful technique in the daily identification of Aspergillus spp. within a limited timeframe.

Raman Scattering as a Probe of the Magnetic State of BEDT-TTF Based Mott Insulators

Directory of Open Access Journals (Sweden)

Nora Hassan

2018-05-01

Full Text Available Quasi-two-dimensional Mott insulators based on BEDT-TTF molecules have recently demonstrated a variety of exotic states, which originate from electron–electron correlations and geometrical frustration of the lattice. Among those states are a triangular S = 1/2 spin liquid and quantum dipole liquid. In this article, we show the power of Raman scattering technique to characterize magnetic and electronic excitations of these states. Our results demonstrate a distinction between a spectrum of magnetic excitations in a simple Mott insulator with antiferromagnetic interactions, and a spectrum of an insulator with an additional on-site charge degree of freedom.

Spectroscopy and Raman imaging of inhomogeneous materials

International Nuclear Information System (INIS)

Maslova, Olga

2014-01-01

This thesis is aimed at developing methodologies in Raman spectroscopy and imaging. After reviewing the statistical instruments which allow treating giant amount of data (multivariate analysis and classification), the study is applied to two families of well-known materials which are used as models for testing the limits of the implemented developments. The first family is a series of carbon materials pyrolyzed at various temperatures and exhibiting inhomogeneities at a nm scale which is suitable for Raman-X-ray diffraction combination. Another results concern the polishing effect on carbon structure. Since it is found to induce Raman artifacts leading to the overestimation of the local structural disorder, a method based on the use of the G band width is therefore proposed in order to evaluate the crystallite size in both unpolished and polished nano-graphites. The second class of materials presents inhomogeneities at higher (micrometric) scales by the example of uranium dioxide ceramics. Being well adapted in terms of spatial scale, Raman imaging is thus used for probing their surfaces. Data processing is implemented via an approach combining the multivariate (principal component) analysis and the classical fitting procedure with Lorentzian profiles. The interpretation of results is supported via electron backscattering diffraction (EBSD) analysis which enables us to distinguish the orientation effects of ceramic grains from other underlying contributions. The last ones are mainly localized at the grain boundaries, that is testified by the appearance of a specific Raman mode. Their origin seems to be caused by stoichiometric oxygen variations or impurities, as well as strain inhomogeneities. The perspectives of this work include both the implementation of other mathematical methods and in-depth analysis of UO 2 structure damaged by irradiation (anisotropic effects, role of grain boundaries). (author) [fr

Damping of vibrational excitations in glasses at terahertz frequency: The case of 3-methylpentane

KAUST Repository

Baldi, Giacomo

2017-10-24

We report a compared analysis of inelastic X ray scattering (IXS) and of low frequency Raman data of glassy 3-methylpentane. The IXS spectra have been analysed allowing for the existence of two distinct excitations at each scattering wavevector obtaining a consistent interpretation of the spectra. In particular, this procedure allows us to interpret the linewidth of the modes in terms of a simple model which relates them to the width of the first sharp diffraction peak in the static structure factor. In this model, the width of the modes arises from the blurring of the dispersion curves which increases approaching the boundary of the first pseudo-Brillouin zone. The position of the boson peak contribution to the density of vibrational states derived from the Raman scattering measurements is in agreement with the interpretation of the two excitations in terms of a longitudinal mode and a transverse mode, the latter being a result of the mixed character of the transverse modes away from the center of the pseudo-Brillouin zone.

Damping of vibrational excitations in glasses at terahertz frequency: The case of 3-methylpentane

KAUST Repository

Baldi, Giacomo; Benassi, Paola; Fontana, Aldo; Giugni, Andrea; Monaco, Giulio; Nardone, Michele; Rossi, Flavio

2017-01-01

We report a compared analysis of inelastic X ray scattering (IXS) and of low frequency Raman data of glassy 3-methylpentane. The IXS spectra have been analysed allowing for the existence of two distinct excitations at each scattering wavevector obtaining a consistent interpretation of the spectra. In particular, this procedure allows us to interpret the linewidth of the modes in terms of a simple model which relates them to the width of the first sharp diffraction peak in the static structure factor. In this model, the width of the modes arises from the blurring of the dispersion curves which increases approaching the boundary of the first pseudo-Brillouin zone. The position of the boson peak contribution to the density of vibrational states derived from the Raman scattering measurements is in agreement with the interpretation of the two excitations in terms of a longitudinal mode and a transverse mode, the latter being a result of the mixed character of the transverse modes away from the center of the pseudo-Brillouin zone.

Instant detection and identification of concealed explosive-related compounds: Induced Stokes Raman versus infrared.

Science.gov (United States)

Elbasuney, Sherif; El-Sherif, Ashraf F

2017-01-01

The instant detection of explosives and explosive-related compounds has become an urgent priority in recent years for homeland security and counter-terrorism applications. Modern techniques should offer enhancement in selectivity, sensitivity, and standoff distances. Miniaturisation, portability, and field-ruggedisation are crucial requirements. This study reports on instant and standoff identification of concealed explosive-related compounds using customized Raman technique. Stokes Raman spectra of common explosive-related compounds were generated and spectrally resolved to create characteristic finger print spectra. The scattered Raman emissions over the band 400:2000cm -1 were compared to infrared absorption using FTIR. It has been demonstrated that the two vibrational spectroscopic techniques were opposite and completing each other. Molecular vibrations with strong absorption in infrared (those involve strong change in dipole moments) induced weak signals in Raman and vice versa. The tailored Raman offered instant detection, high sensitivity, and standoff detection capabilities. Raman demonstrated characteristic fingerprint spectra with stable baseline and sharp intense peaks. Complete correlations of absorption/scattered signals to certain molecular vibrations were conducted to generate an entire spectroscopic profile of explosive-related compounds. This manuscript shades the light on Raman as one of the prevailing technologies for instantaneous detection of explosive-related compounds. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Comparison of Surface-enhanced Raman Scattering Spectra of Two Kinds of Silver Nanoplate Films

Institute of Scientific and Technical Information of China (English)

TAO Jin-long; TANG Bin; XU Shu-ping; PAN Ling-yun; XU Wei-qing

2012-01-01

Surface-enhanced Raman scattering(SERS) spectra of different silver nanoplate self-assembled films at different excitation wavelengths were fairly compared.Shape conversion from silver nanoprisms to nanodisks on slides was in situ carried out.The SERS spectra of 4-mercaptopyridine(4-MPY) on these anisotropic silver nanoparticle self-assembled films present that strong enhancement appeared when the excitation line and the surface plasmon resonance(SPR) band of silver substrate overlapped.In this model,the influence of the crystal planes of silver nanoplates on SERS enhancement could be ignored because the basal planes were nearly unchanged in two kinds of silver nanoplate self-assembled films.

The miniaturized Raman system and detection of traces of life in halite from the Atacama Desert: some considerations for the search for life signatures on Mars.

Science.gov (United States)

Vítek, Petr; Jehlička, Jan; Edwards, Howell G M; Hutchinson, Ian; Ascaso, Carmen; Wierzchos, Jacek

2012-12-01

Raman spectroscopy is being adopted as a nondestructive instrumentation for the robotic exploration of Mars to search for traces of life in the geological record. Here, miniaturized Raman spectrometers of two different types equipped with 532 and 785 nm lasers for excitation, respectively, were compared for the detection of microbial biomarkers in natural halite from the hyperarid region of the Atacama Desert. Measurements were performed directly on the rock as well as on the homogenized, powdered samples prepared from this material-the effects of this sample preparation and the excitation wavelength employed in the analysis are compared and discussed. From these results, 532 nm excitation was found to be superior for the analysis of powdered specimens due to its high sensitivity toward carotenoids and hence a higher capability for their detection at relatively low concentration in bulk powdered specimens. For the same reason, this wavelength was a better choice for the detection of carotenoids in direct measurements made on the rock samples. The 785 nm excitation wavelength, in contrast, proved to be more sensitive toward the detection of scytonemin.

Next generation in-situ optical Raman sensor for seawater investigations

Science.gov (United States)

Kolomijeca, A.; Kwon, Y.-H.; Ahmad, H.; Kronfeldt, H.-D.

2012-04-01

We introduce the next generation of optical sensors based on a combination of surfaced enhanced Raman scattering (SERS) and shifted excitation Raman difference spectroscopy (SERDS) suited for investigations of tiny concentrations of pollutions in the seawater. First field measurements were carried out in the Arctic area which is of global interest since it is more affected by global warming caused climatic changes than any other areas of our planet and it is a recipient for many toxic organic pollutants. A significant long-range atmospheric transport of pollutants to Svalbard is mainly originated from industrialized countries in Europe and North America during the last decades. Therefore, the main interest is to investigate the Arctic water column and also the sediments. Standard chemical methods for water/sediment analysis are extremely accurate but complex and time-consuming. The primary objective of our study was to develop a fast response in-situ optical sensor for easy to use and quick analysis. The system comprises several components: a handheld measurement head containing a 671 nm microsystem diode laser and the Raman optical bench, a laser driver electronics board, a custom-designed miniature spectrometer with an optical resolution of 8 cm-1 and a netbook to control the spectrometer as well as for data evaluation. We introduced for the first time the portable Raman sensor system on an Artic sea-trial during a three week cruise on board of the James Clark Ross research vessel in August 2011. Numerous Raman and SERS measurements followed by SERDS evaluations were taken around locations 78° N and 9° E. Different SERS substrates developed for SERS measurements in sea-water were tested for their capability to detect different substances (PAHs) in the water down to very small (nmol/l) concentrations. Stability tests of the substrates were carried out also for the applicability of our system e.g. on a mooring. Details of the in-situ Raman sensor were presented

Multi-gap superconductivity in MgB2: Magneto-Raman spectroscopy

International Nuclear Information System (INIS)

Blumberg, G.; Mialitsin, A.; Dennis, B.S.; Zhigadlo, N.D.; Karpinski, J.

2007-01-01

Electronic Raman scattering studies on MgB 2 single crystals as a function of excitation and polarization have revealed three distinct superconducting features: a clean gap below 37 cm -1 and two coherence peaks at 109 and 78 cm -1 which we identify as the superconducting gaps in π- and σ-bands and as the Leggett's collective mode arising from the fluctuation in the relative phase between two superconducting condensates residing on corresponding bands. The temperature and field dependencies of the superconducting features have been established. A phononic Raman scattering study of the E 2g boron stretching mode anharmonicity and of superconductivity induced self-energy effects is presented. We show that anharmonic two phonon decay is mainly responsible for the unusually large linewidth of the E 2g mode. We observe ∼2.5% hardening of the E 2g phonon frequency upon cooling into the superconducting state and estimate the electron-phonon coupling strength associated with this renormalization

High-pressure Raman study of vibrational spectra in crystalline acetanilide

Science.gov (United States)

Sakai, Masamichi; Kuroda, Noritaka; Nishina, Yuichiro

1993-01-01

We have studied the effect of pressure on the low-frequency lattice modes and the amide-I (N-CO stretching) vibrational modes in crystalline acetanilide (C6H5NHCOCH3) in the temperature range 80-300 K by means of Raman spectroscopy. The Raman intensity of the 1650-cm-1 band, which appears upon cooling, is enhanced by applying pressure. The energy difference between the amide-I phonon (Ag mode) and the 1650-cm-1 bands does not change appreciably under pressure up to at least 4 GPa. These results are analyzed in terms of the self-trapped model in which a single lattice mode couples with the amide-I excitation by taking into account the effect of pressure on the low-frequency lattice modes and on the dipole-dipole interactions associated with the amide-I vibration. A band is observed at 30 cm-1 below the amide-I phonon band at low temperatures with a pressure above ~2 GPa.

Evidence for anisotropic excitonlike enhancement of the Raman scattering from La2CuO4

International Nuclear Information System (INIS)

Weber, W.H.; Peters, C.R.; Wanklyn, B.M.; Chen, C.; Watts, B.E.

1988-01-01

Polarized Raman studies on oriented single crystals of La 2 CuO 4 yield α/sub z//sub z/ spectra with narrow lines at 429 and 228 cm/sup -1/ that are identified as the two A 1 /sub g/ modes expected for the tetragonal K 2 NiF 4 structure; α/sub x//sub z/ spectra with one line at 228 cm/sup -1/ that has E/sub g/ symmetry; and α/sub x//sub x/ spectra with numerous peaks that are due to normally forbidden phonon excitations. The α/sub x//sub x/ spectra also show strong second-order features, suggesting a highly anisotropic, excitonlike enhancement of the Raman scattering

Mechanism of Exciplex Formation Between Cu-Porphyrin and Calf-thymus DNA as Revealed by Saturation Resonance Raman Spectroscopy

NARCIS (Netherlands)

Shvedko, A.G.; Kruglik, S.; Kruglik, S.G.; Ermolenkov, V.V.; Turpin, P.Y.; Greve, Jan; Otto, Cornelis

1999-01-01

The excited-state complex (exciplex) formation that results from the photoinduced interaction of water-soluble cationic copper(II) 5,10,15,20-tetrakis[4-(N-methylpyridyl)]porphyrin [Cu(TMpy-P4)] with calf-thymus DNA has been studied in detail by resonance Raman (RR) spectroscopy using both ~10 ns

Resonance Raman spectroscopy in the picosecond time scale: the carboxyhemoglobin photointermediate

International Nuclear Information System (INIS)

Terner, J.; Spiro, T.G.; Nagumo, M.; Nicol, M.F.; El-Sayed, M.A.

1980-01-01

A picosecond resonance Raman detection technique is described. The technique is described as specifically applied to the analysis of carboxyhemoglobin (COHb). Irradiaton of COHb with a tightly focused laser produced three distinct bands between 1540 and 1620cm -1 that are distinct from bands of COHb or deoxyHb, and the bands are attributed to an intermediate in the photolysis of COHb which develops within 30ps of the excitation. Computer subtraction of the COHb spectrum yielded a spectrum of the photointermediate

Raman Spectra and Bulk Modulus of Nanodiamond in a Size Interval of 2-5 nm

Science.gov (United States)

Popov, Mikhail; Churkin, Valentin; Kirichenko, Alexey; Denisov, Viktor; Ovsyannikov, Danila; Kulnitskiy, Boris; Perezhogin, Igor; Aksenenkov, Viktor; Blank, Vladimir

2017-10-01

Nanodiamond in a 2-5-nm size interval (which is typical for an appearance of quantum confinement effect) show Raman spectra composed of 3 bands at 1325, 1600, and 1500 cm-1 (at the 458-nm laser excitation) which shifts to 1630 cm-1 at the 257-nm laser excitation. Contrary to sp2-bonded carbon, relative intensities of the bands do not depend on the 458- and 257-nm excitation wavelengths, and a halfwidth and the intensity of the 1600 cm-1 band does not change visibly under pressure at least up to 50 GPa. Bulk modulus of the 2-5-nm nanodiamond determined from the high-pressure study is around 560 GPa. Studied 2-5-nm nanodiamond was purified from contamination layers and dispersed in Si or NaCl.

Comparison of in situ ionizing radiation effects on Raman and photoluminescence intensity of high OH, low OH silica, and fluoride core fibers

Science.gov (United States)

Bilodeau, T. G.; Ewing, K. J.; Nau, G. M.; Aggarwal, I. D.

1995-06-01

An in situ study of the effects of ionizing radiation on the strength of the Raman and photoluminescence signal of high OH, low OH, and fluoride core fibers has been performed with 514.5 nm laser excitation. The fibers were irradiated with a 60Co source at a constant dose rate of 560 rads/h. The high OH fiber displayed a much slower decay of the fiber Raman intensity than the other two fibers during irradiation. The fluoride fiber exhibited the quickest decline in Raman signal with the intensity dropping by a factor of 1000 in less than 20 min. The Raman intensity of the low OH silica fiber recovered to greater than 90% of its pre-irradiation value after a post-irradiation photoanneal with 488 nm laser light. The silica fibers displayed an increase in intensity of a broad photoluminescence feature centered at 650 nm. However the fiber photoluminescence intensity remained much weaker than the Raman intensity throughout the irradiations.

Surface-enhanced resonance Raman scattering spectroscopy of single R6G molecules

Institute of Scientific and Technical Information of China (English)

Zhou Zeng-Hui; Liu Li; Wang Gui-Ying; Xu Zhi-Zhan

2006-01-01

Surface-enhanced resonance Raman scattering (SERRS) of Rhodamine 6G (R6G) adsorbed on colloidal silver clusters has been studied. Based on the great enhancement of the Raman signal and the quench of the fluorescence, the SERRS spectra of R6G were recorded for the samples of dye colloidal solution with different concentrations. Spectral inhomogeneity behaviours from single molecules in the dried sample films were observed with complementary evidences, such as spectral polarization, spectral diffusion, intensity fluctuation of vibrational lines and even "breathing" of the molecules. Sequential spectra observed from a liquid sample with an average of 0.3 dye molecules in the probed volume exhibited the expected Poisson distribution for actually measuring 0, 1 or 2 molecules. Difference between the SERRS spectra of R6G excited by linearly and circularly polarized light were experimentally measured.

[Fluorescent and Raman scattering by molecules embedded in small particles]: Annual report, 1983

International Nuclear Information System (INIS)

Chew, H.; McNulty, P.J.

1983-01-01

An overview is given of the model formulated for fluorescent and Raman scattering by molecules embedded in or in the vicinity of small particles. The model takes into account the size, shape, refractive index, and morphology of the host particles. Analytic and numerical results have been obtained for spherical (one and more layers, including magnetic dipole transitions), cylindrical, and spheroidal particles. Particular attention has been given to the spherical case with fluorescent/Raman scatterers uniformly distributed in the particles radiating both coherently and incoherently. Depolarization effects have been studied with suitable averaging process, and good agreement with experiment has been obtained. Analytic and numerical results have been obtained for the elastic scattering of evanescent waves; these results are useful for the study of fluorescence under excitation by evanescent waves

Radiation from an excited vortex in the Abelian Higgs model

Science.gov (United States)

Arodź, H.; Hadasz, L.

1996-09-01

An excited vortex in the Abelian Higgs model is investigated with the help of a polynomial approximation. The excitation consists of the longitudinal component of a vector field trapped by the vortex. The energy and profile of the excitation as well as its back reaction on the vortex are found in the case of small κ. It turns out that the width of the excited vortex oscillates in time. Moreover, the vector field has a radiative long range component. Also, an upper bound on the amplitude of the excitation is found.

Fe-Ti-Cr-Oxides in Martian Meteorite EETA79001 Studied by Point-counting Procedure Using Raman Spectroscopy

Science.gov (United States)

Wang, Alian; Kuebler, Karla E.; Jolliff, Bradley L.; Haskin, Larry A.

2003-01-01

Fe-Ti-Cr-Oxide minerals contain much information about rock petrogenesis and alteration. Among the most important in the petrology of common intrusive and extrusive rocks are those of the FeO-TiO2-Cr2O3 compositional system chromite, ulv spinel-magnetite, and ilmenite-hematite. These minerals retain memories of oxygen fugacity. Their exsolution into companion mineral pairs give constraints on formation temperature and cooling rate. Laser Raman spectroscopy is anticipated to be a powerful technique for characterization of materials on the surface of Mars. A Mars Microbeam Raman Spectrometer (MMRS) is under development. It combines a micro sized laser beam and an automatic point-counting mechanism, and so can detect minor minerals or weak Raman-scattering phases such as Fe- Ti-Cr-oxides in mixtures (rocks & soils), and provide information on grain size and mineral mode. Most Fe-Ti-Cr-oxides produce weaker Raman signals than those from oxyanionic minerals, e.g. carbonates, sulfates, phosphates, and silicates, partly because most of them are intrinsically weaker Raman scatters, and partly because their dark colors limit the penetration depth of the excitation laser beam (visible wavelength) and of the Raman radiation produced. The purpose of this study is to show how well the Fe-Ti-Cr-oxides can be characterized by on-surface planetary exploration using Raman spectroscopy. We studied the basic Raman features of common examples of these minerals using well-characterized individual mineral grains. The knowledge gained was then used to study the Fe-Ti-Cr-oxides in Martian meteorite EETA79001, especially effects of compositional and structural variations on their Raman features.

Intermolecular interaction of photoexcited Cu(/TMpy-P4) with water studied by transient resonance Raman and picosecond absorption spectroscopies

NARCIS (Netherlands)

Kruglik, S.; Kruglik, Sergei G.; Ermolenkov, Vladimir V.; Shvedko, Alexander G.; Orlovich, Valentine A.; Galievsky, Victor A.; Chirvony, Vladimir S.; Otto, Cornelis; Turpin, Pierre-Yves

1997-01-01

photoinduced complex between Cu(TMpy-P4) and water molecules, reversibly axially coordinated to the central metal, was observed in picosecond transient absorption and nanosecond resonance Raman experiments. This complex is rapidly created (τ1 = 15 ± 5 ps) in the excited triplet (π, π*) state of

Combined raman and IR fiber-based sensor for gas detection

Science.gov (United States)

Carter, Jerry C; Chan, James W; Trebes, James E; Angel, Stanley M; Mizaikoff, Boris

2014-06-24

A double-pass fiber-optic based spectroscopic gas sensor delivers Raman excitation light and infrared light to a hollow structure, such as a hollow fiber waveguide, that contains a gas sample of interest. A retro-reflector is placed at the end of this hollow structure to send the light back through the waveguide where the light is detected at the same end as the light source. This double pass retro reflector design increases the interaction path length of the light and the gas sample, and also reduces the form factor of the hollow structure.

Structural dynamics of a noncovalent charge transfer complex from femtosecond stimulated Raman spectroscopy.

Science.gov (United States)

Fujisawa, Tomotsumi; Creelman, Mark; Mathies, Richard A

2012-09-06

Femtosecond stimulated Raman spectroscopy is used to examine the structural dynamics of photoinduced charge transfer within a noncovalent electron acceptor/donor complex of pyromellitic dianhydride (PMDA, electron acceptor) and hexamethylbenzene (HMB, electron donor) in ethylacetate and acetonitrile. The evolution of the vibrational spectrum reveals the ultrafast structural changes that occur during the charge separation (Franck-Condon excited state complex → contact ion pair) and the subsequent charge recombination (contact ion pair → ground state complex). The Franck-Condon excited state is shown to have significant charge-separated character because its vibrational spectrum is similar to that of the ion pair. The charge separation rate (2.5 ps in ethylacetate and ∼0.5 ps in acetonitrile) is comparable to solvation dynamics and is unaffected by the perdeuteration of HMB, supporting the dominant role of solvent rearrangement in charge separation. On the other hand, the charge recombination slows by a factor of ∼1.4 when using perdeuterated HMB, indicating that methyl hydrogen motions of HMB mediate the charge recombination process. Resonance Raman enhancement of the HMB vibrations in the complex reveals that the ring stretches of HMB, and especially the C-CH(3) deformations are the primary acceptor modes promoting charge recombination.

Assessing the Temperature Dependence of Narrow-Band Raman Water Vapor Lidar Measurements: A Practical Approach

Science.gov (United States)

Whiteman, David N.; Venable, Demetrius D.; Walker, Monique; Cardirola, Martin; Sakai, Tetsu; Veselovskii, Igor

2013-01-01

Narrow-band detection of the Raman water vapor spectrum using the lidar technique introduces a concern over the temperature dependence of the Raman spectrum. Various groups have addressed this issue either by trying to minimize the temperature dependence to the point where it can be ignored or by correcting for whatever degree of temperature dependence exists. The traditional technique for performing either of these entails accurately measuring both the laser output wavelength and the water vapor spectral passband with combined uncertainty of approximately 0.01 nm. However, uncertainty in interference filter center wavelengths and laser output wavelengths can be this large or larger. These combined uncertainties translate into uncertainties in the magnitude of the temperature dependence of the Raman lidar water vapor measurement of 3% or more. We present here an alternate approach for accurately determining the temperature dependence of the Raman lidar water vapor measurement. This alternate approach entails acquiring sequential atmospheric profiles using the lidar while scanning the channel passband across portions of the Raman water vapor Q-branch. This scanning is accomplished either by tilt-tuning an interference filter or by scanning the output of a spectrometer. Through this process a peak in the transmitted intensity can be discerned in a manner that defines the spectral location of the channel passband with respect to the laser output wavelength to much higher accuracy than that achieved with standard laboratory techniques. Given the peak of the water vapor signal intensity curve, determined using the techniques described here, and an approximate knowledge of atmospheric temperature, the temperature dependence of a given Raman lidar profile can be determined with accuracy of 0.5% or better. A Mathematica notebook that demonstrates the calculations used here is available from the lead author.

Growth mechanism and magnon excitation in NiO nanowalls

Directory of Open Access Journals (Sweden)

Yang Chun

2011-01-01

Full Text Available Abstract The nanosized effects of short-range multimagnon excitation behavior and short-circuit diffusion in NiO nanowalls synthesized using the Ni grid thermal treatment method were observed. The energy dispersive spectroscopy mapping technique was used to characterize the growth mechanism, and confocal Raman scattering was used to probe the antiferromagnetic exchange energy J 2 between next-nearest-neighboring Ni ions in NiO nanowalls at various growth temperatures below the Neel temperature. This study shows that short spin correlation leads to an exponential dependence of the growth temperatures and the existence of nickel vacancies during the magnon excitation. Four-magnon configurations were determined from the scattering factor, revealing a lowest state and monotonic change with the growth temperature. PACS: 75.47.Lx; 61.82.Rx; 75.50.Tt; 74.25.nd; 72.10.Di

Growth mechanism and magnon excitation in NiO nanowalls

Science.gov (United States)

2011-01-01

The nanosized effects of short-range multimagnon excitation behavior and short-circuit diffusion in NiO nanowalls synthesized using the Ni grid thermal treatment method were observed. The energy dispersive spectroscopy mapping technique was used to characterize the growth mechanism, and confocal Raman scattering was used to probe the antiferromagnetic exchange energy J2 between next-nearest-neighboring Ni ions in NiO nanowalls at various growth temperatures below the Neel temperature. This study shows that short spin correlation leads to an exponential dependence of the growth temperatures and the existence of nickel vacancies during the magnon excitation. Four-magnon configurations were determined from the scattering factor, revealing a lowest state and monotonic change with the growth temperature. PACS: 75.47.Lx; 61.82.Rx; 75.50.Tt; 74.25.nd; 72.10.Di PMID:21824408

Optical diagnostic of hepatitis B (HBV) and C (HCV) from human blood serum using Raman spectroscopy

International Nuclear Information System (INIS)

Anwar, Shahzad; Firdous, Shamaraz

2015-01-01

Hepatitis is the second most common disease worldwide with half of the cases arising in the developing world. The mortality associated with hepatitis B and C can be reduced if the disease is detected at the early stages of development. The aim of this study was to investigate the potential of Raman spectroscopy as a diagnostic tool to detect biochemical changes accompanying hepatitis progression. Raman spectra were acquired from 20 individuals with six hepatitis B infected patients, six hepatitis C infected patients and eight healthy patients in order to gain an insight into the determination of biochemical changes for early diagnostic. The human blood serum was examined at a 532 nm excitation laser source. Raman characteristic peaks were observed in normal sera at 1006, 1157 and 1513 cm −1 , while in the case of hepatitis B and C these peaks were found to be blue shifted with decreased intensity. New Raman peaks appeared in HBV and HCV infected sera at 1194, 1302, 844, 905, 1065 and 1303 cm −1 respectively. A Mat lab subroutine and frequency domain filter program is developed and applied to signal processing of Raman scattering data. The algorithms have been successfully applied to remove the signal noise found in experimental scattering signals. The results show that Raman spectroscopy displays a high sensitivity to biochemical changes in blood sera during disease progression resulting in exceptional prediction accuracy when discriminating between normal and malignant. Raman spectroscopy shows enormous clinical potential as a rapid non-invasive diagnostic tool for hepatitis and other infectious diseases. (letter)

Optical diagnostic of hepatitis B (HBV) and C (HCV) from human blood serum using Raman spectroscopy

Science.gov (United States)

Anwar, Shahzad; Firdous, Shamaraz

2015-06-01

Hepatitis is the second most common disease worldwide with half of the cases arising in the developing world. The mortality associated with hepatitis B and C can be reduced if the disease is detected at the early stages of development. The aim of this study was to investigate the potential of Raman spectroscopy as a diagnostic tool to detect biochemical changes accompanying hepatitis progression. Raman spectra were acquired from 20 individuals with six hepatitis B infected patients, six hepatitis C infected patients and eight healthy patients in order to gain an insight into the determination of biochemical changes for early diagnostic. The human blood serum was examined at a 532 nm excitation laser source. Raman characteristic peaks were observed in normal sera at 1006, 1157 and 1513 cm-1, while in the case of hepatitis B and C these peaks were found to be blue shifted with decreased intensity. New Raman peaks appeared in HBV and HCV infected sera at 1194, 1302, 844, 905, 1065 and 1303 cm-1 respectively. A Mat lab subroutine and frequency domain filter program is developed and applied to signal processing of Raman scattering data. The algorithms have been successfully applied to remove the signal noise found in experimental scattering signals. The results show that Raman spectroscopy displays a high sensitivity to biochemical changes in blood sera during disease progression resulting in exceptional prediction accuracy when discriminating between normal and malignant. Raman spectroscopy shows enormous clinical potential as a rapid non-invasive diagnostic tool for hepatitis and other infectious diseases.

Airborne detection of oceanic turbidity cell structure using depth-resolved laser-induced water Raman backscatter

Science.gov (United States)

Hoge, F. E.; Swift, R. N.

1983-01-01

Airborne laser-induced, depth-resolved water Raman backscatter is useful in the detection and mapping of water optical transmission variations. This test, together with other field experiments, has identified the need for additional field experiments to resolve the degree of the contribution to the depth-resolved, Raman-backscattered signal waveform that is due to (1) sea surface height or elevation probability density; (2) off-nadir laser beam angle relative to the mean sea surface; and (3) the Gelbstoff fluorescence background, and the analytical techniques required to remove it. When converted to along-track profiles, the waveforms obtained reveal cells of a decreased Raman backscatter superimposed on an overall trend of monotonically decreasing water column optical transmission.

Effect of a Nitrogen Impurity on the Fundamental Raman Band of Diamond Single Crystals

Science.gov (United States)

Gusakov, G. A.; Samtsov, M. P.; Voropay, E. S.

2018-05-01

The effect of nitrogen defects in natural and synthetic diamond single crystals on the position and half-width of the fundamental Raman band was investigated. Samples containing the main types of nitrogen lattice defects at impurity contents of 1-1500 ppm were studied. The parameters of the Stokes and anti-Stokes components in Raman spectra of crystals situated in a cell with distilled water to minimize the influence of heating by the exciting laser radiation were analyzed to determine the effect of a nitrogen impurity in the diamond crystal lattice. It was shown that an increase of impurity atoms in the crystals in the studied concentration range resulted in broadening of the Raman band from 1.61 to 2.85 cm-1 and shifting of the maximum to lower frequency from 1332.65 to 1332.3 cm-1. The observed effect was directly proportional to the impurity concentration and depended on the form of the impurity incorporated into the diamond lattice. It was found that the changes in the position and half-width of the fundamental Raman band for diamond were consistent with the magnitude of crystal lattice distortions due to the presence of impurity defects and obeyed the Gruneisen law.

Rapid detection of bacterial contamination in cell or tissue cultures based on Raman spectroscopy

Science.gov (United States)

Bolwien, Carsten; Sulz, Gerd; Becker, Sebastian; Thielecke, Hagen; Mertsching, Heike; Koch, Steffen

2008-02-01

Monitoring the sterility of cell or tissue cultures is an essential task, particularly in the fields of regenerative medicine and tissue engineering when implanting cells into the human body. We present a system based on a commercially available microscope equipped with a microfluidic cell that prepares the particles found in the solution for analysis, a Raman-spectrometer attachment optimized for non-destructive, rapid recording of Raman spectra, and a data acquisition and analysis tool for identification of the particles. In contrast to conventional sterility testing in which samples are incubated over weeks, our system is able to analyze milliliters of supernatant or cell suspension within hours by filtering relevant particles and placing them on a Raman-friendly substrate in the microfluidic cell. Identification of critical particles via microscopic imaging and subsequent image analysis is carried out before micro-Raman analysis of those particles is then carried out with an excitation wavelength of 785 nm. The potential of this setup is demonstrated by results of artificial contamination of samples with a pool of bacteria, fungi, and spores: single-channel spectra of the critical particles are automatically baseline-corrected without using background data and classified via hierarchical cluster analysis, showing great promise for accurate and rapid detection and identification of contaminants.