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1

Optical biopsy: laser autofluorescent and Raman spectroscopies in tumor diagnostics  

NASA Astrophysics Data System (ADS)

This paper presents a review of the studies on using laser autofluorescent and Raman spectroscopies in tumor diagnostics. Peculiarities of spectroscopy by different wavelength lasers and different organs is described. Prospects of the diagnostics method is discussed.

Kazaryan, Airazat M.

2000-02-01

2

Laser tweezers Raman spectroscopy of single cells  

NASA Astrophysics Data System (ADS)

Raman scattering is an inelastic collision between the vibrating molecules inside the sample and the incident photons. During this process, energy exchange takes place between the photon and the scattering molecule. By measuring the energy change of the photon, the molecular vibration mode can be probed. The vibrational spectrum contains valuable information about the disposition of atomic nuclei and chemical bonds within a molecule, the chemical compositions and the interactions between the molecule and its surroundings. In this dissertation, laser tweezers Raman spectroscopy (LTRS) technique is applied for the analysis of biological cells and human cells at single cell level. In LTRS, an individual cell is trapped in aqueous medium with laser tweezers, and Raman scattering spectra from the trapped cell are recorded in real-time. The Raman spectra of these cells can be used to reveal the dynamical processes of cell growth, cell response to environment changes, and can be used as the finger print for the identification of a bacterial cell species. Several biophysical experiments were carried out using LTRS: (1) the dynamic germination process of individual spores of Bacillus thuringiensis was detected via Ca-DPA, a spore-specific biomarker molecule; (2) inactivation and killing of Bacillus subtilis spores by microwave irradiation and wet heat were studied at single cell level; (3) the heat shock activation process of single B. subtilis spores were analyzed, in which the reversible transition from glass-like state at low temperature to liquid-like state at high temperature in spore was revealed at the molecular level; (4) the kinetic processes of bacterial cell lysis of E. coli by lysozyme and by temperature induction of lambda phage were detected real-time; (5) the fixation and rehydration of human platelets were quantitatively evaluated and characterized with Raman spectroscopy method, which provided a rapid way to quantify the quality of freeze-dried therapeutic platelet products for long term preservation; (6) LTRS based depolarized Raman spectroscopy was developed and used to do bacterial cell identification of similar species. From these experiments, several new findings and conclusions have been obtained. (1) single spore dynamic germination was measured for the first time. The result showed the time-to-germinate of a single spore was stochastic and could be discrete. (2) the thermal nature of spore killing in solution by microwaves was identified, Spores killed directly by microwaves showed death marker in Raman spectrum; (3) The Ca-DPA inside the spore core of a spore would undergo a structure modification during heat shock, which was related to the spores' state transition from a glass-like to a rubbery-like state, this structure modification during heat shock was reversible; (4) the kinetic molecular processes of E. coli cell lysis by lysozyme and by temperature induction of bacterial phage were recorded for the first time. The different cellular processes of the lysis were revealed based on the two different mechanisms; (5) LTRS technique was successfully applied to characterize human platelet fixation; a major procedure for long term preservation of therapeutic human platelet products; (6) A depolarization laser tweezers Raman spectroscopy (DLTRS) technique was developed to enhance the ability to discriminate similar bacterial species.

Chen, De

3

Methane detection with single laser photoacoustic Raman spectroscopy  

Microsoft Academic Search

Methane detection with a new arrangement of photoacoustic Raman spectroscopy has been carried out with self seeding of the Stokes beam generation. It employs only one fixed frequency pulsed laser source, the light of which is focused into a Raman cell, filled with the same gas to be detected. Both fundamental and Stokes shifted beams are sent through a carefully

J. Sneider; Z. Bozóki; G. Szabó; Zs. Bor

1999-01-01

4

Application of cheap lasers in shifted excitation Raman difference spectroscopy  

NASA Astrophysics Data System (ADS)

Raman spectroscopy has increasing importance in a wide field of applications: particularly in real time monitoring of chemical processes, testing of foodstuffs, identification of ingredients in unknown material mixtures etc. Many materials of interest have resonance wavelength close to the excitation wavelength. Resonant Raman spectroscopy can be used to advantage in these cases. The disadvantage of this technology is the presence of a strong fluorescence background in the Raman spectrum. A combination of the mechanism of resonant Raman spectroscopy with shifted excitation Raman difference spectroscopy can be used to suppress the fluorescence background. The applicability of inexpensive green lasers for this purpose and their tunability by temperature and current is investigated in this paper. The setup consists of two pigtailed lasers at a wavelength of 532 nm with a small wavelength difference switched by a fiber switch with a frequency up to 50 Hz. Every switching pulse triggers an optical spectrometer to measure the backscattered light. A resonant Raman spectrum with a minimized fluorescence background is obtained by subtraction of the two different spectra. The specific wavelengths of the two lasers were set by thermal tuning. The Raman spectra of Isopropanol and Carbon Tetrachloride have been measured in order to verify the setup.

Wolf, Stefan; Döring, Heinz

2012-05-01

5

Evaluation of near-infrared laser Raman spectroscopy underwater research  

NASA Astrophysics Data System (ADS)

The in-situ chemical detection in deep sea is very important for mineral resources exploitation. Laser Raman Spectroscopy as a powerful tool for chemical analysis has been used in deep sea detection recently. It was found that the fluorescence always exists as the background on Raman spectra detecting in ocean. It is apparent that the fluorescence background could be decrease effectively using near infrared wavelength as excitation source. While near infrared laser has few application underwater due to the absorption of water in this wavelength range. In this paper, a 785nm Raman spectrometer was used to evaluate the near infrared laser Raman spectroscopy for underwater application. It was found that the Raman shift of SO4 2- at 981cm-1 can be easily detected from Qingdao near shore sea water samples without sever fluorescence background. With mixed solution of SO4 2- and HCO3 -, the detection limit achieved for SO4 2- at 981cm-1 and HCO3 - at 1017cm-1 was obtained by 785nm compact Raman spectrometer to be 0.00625mol/l and 0.025mol/l with 10s integration time respectively. The obtained results proved the feasibility of near infrared laser Raman underwater detection.

Guo, Jinjia; Zhang, Bin; Wu, Jianglai; Zheng, Ronger

2009-07-01

6

Application of laser Raman spectroscopy to dental diagnosis  

NASA Astrophysics Data System (ADS)

The aim of this research is related with the diagnosis of caries by use of a laser. We study the fundamental characterization of the diagnosis method using both fluorescence and Raman scattering spectroscopy. We try to evaluate the possibility of the caries diagnosis using Raman spectroscopy and its clinical application. We focus on the PO34- ion that flows out with the dissolution of hydroxyapatite (HAp), and the fluorescence that increases in connection with caries. The Raman line of P-O vibration is overlapped on the continuous, background spectrum by fluorescence. Consequently, we try to find out the correlation between a healthy part and a carious part by analyzing both fluorescence and Raman spectra. It was found that Raman intensity of HAp at carious lesion was weaker than those of healthy parts and the florescence intensity at the same portions was stronger. We have obtained the feasibility to estimate the degree of caries and health condition by deriving the ratio between Raman and florescence intensity. And the trial measurements in vivo were carried out to verify the availability of the method by using a fiber probe type multi channel Raman spectrometer. The process of remineralization is under researching for the development of preventive medicine.

Izawa, Takahiro; Wakaki, Moriaki

2005-03-01

7

Grating-Stabilized External Cavity Diode Lasers for Raman Spectroscopy—A Review  

Microsoft Academic Search

Conventional Raman technique requires a continuous-wave laser with stabilized wavelength, narrow linewidth, and sufficient output power. Because of their miniature size and low cost, diode lasers are good choice as light sources for Raman spectroscopy, especially when compact and portable instruments are needed. However, a solitary multimode diode laser has certain drawbacks that limit its use for Raman application. To

Wenbo Wang; Arkady Major; Jitendra Paliwal

2011-01-01

8

Grating-Stabilized External Cavity Diode Lasers for Raman Spectroscopy—A Review  

Microsoft Academic Search

Abstract: Conventional Raman techniques require a continuous-wave laser with stabilized wavelength, narrow line width, and sufficient output power. Due to their miniature size and low cost, diode lasers are good choice as light sources for Raman spectroscopy, especially when compact and portable instruments are needed. However, a solitary multimode diode laser has certain drawbacks that limit its use for Raman

Wenbo Wang; Arkady Major; Jitendra Paliwal

2012-01-01

9

Optimizing the laser-pulse configuration for coherent Raman spectroscopy.  

PubMed

We introduce a hybrid technique that combines the robustness of frequency-resolved coherent anti-Stokes Raman scattering (CARS) with the advantages of time-resolved CARS spectroscopy. Instantaneous coherent broadband excitation of several characteristic molecular vibrations and the subsequent probing of these vibrations by an optimally shaped time-delayed narrowband laser pulse help to suppress the nonresonant background and to retrieve the species-specific signal. We used this technique for coherent Raman spectroscopy of sodium dipicolinate powder, which is similar to calcium dipicolinate (a marker molecule for bacterial endospores, such as Bacillus subtilis and Bacillus anthracis), and we demonstrated a rapid and highly specific detection scheme that works even in the presence of multiple scattering. PMID:17431177

Pestov, Dmitry; Murawski, Robert K; Ariunbold, Gombojav O; Wang, Xi; Zhi, Miaochan; Sokolov, Alexei V; Sautenkov, Vladimir A; Rostovtsev, Yuri V; Dogariu, Arthur; Huang, Yu; Scully, Marlan O

2007-04-13

10

Optimizing the Laser-Pulse Configuration for Coherent Raman Spectroscopy  

NASA Astrophysics Data System (ADS)

We introduce a hybrid technique that combines the robustness of frequency-resolved coherent anti-Stokes Raman scattering (CARS) with the advantages of time-resolved CARS spectroscopy. Instantaneous coherent broadband excitation of several characteristic molecular vibrations and the subsequent probing of these vibrations by an optimally shaped time-delayed narrowband laser pulse help to suppress the nonresonant background and to retrieve the species-specific signal. We used this technique for coherent Raman spectroscopy of sodium dipicolinate powder, which is similar to calcium dipicolinate (a marker molecule for bacterial endospores, such as Bacillus subtilis and Bacillus anthracis), and we demonstrated a rapid and highly specific detection scheme that works even in the presence of multiple scattering.

Pestov, Dmitry; Murawski, Robert K.; Ariunbold, Gombojav O.; Wang, Xi; Zhi, Miaochan; Sokolov, Alexei V.; Sautenkov, Vladimir A.; Rostovtsev, Yuri V.; Dogariu, Arthur; Huang, Yu; Scully, Marlan O.

2007-04-01

11

Remote cure monitoring of polymeric resins by laser Raman spectroscopy.  

National Technical Information Service (NTIS)

The validity of using Raman spectroscopy to monitor the cure chemistries of amine-cured epoxy is demonstrated by correlating NIR absorbance measurements with Raman measurements for a concentration series of bisphenol-A diglycidylether in its own reaction ...

K. C. Hong T. M. Vess R. E. Lyon M. L. Myrick

1993-01-01

12

Femtosecond laser induced nanostructuring for surface enhanced Raman spectroscopy  

NASA Astrophysics Data System (ADS)

The formation of periodical nanostructures with femtosecond laser pulses was used to create highly efficient substrates for surface-enhanced Raman spectroscopy (SERS). We report about the structuring of silver and copper substrates and their application to the SERS of DNA (herring sperm) and protein molecules (egg albumen). The maximum enhancement factors were found on Ag substrates processed with the second harmonic generation (SHG) of a 1-kHz Ti:sapphire laser and structure periods near the SHG wavelength. In the case of copper, however, the highest enhancement was obtained with long-period ripples induced with at fundamental wavelength. This is explained by an additional significant influence of nanoparticles on the surface. Nanostructured areas in the range of 1.25 mm2 were obtained in 10 s. The surfaces were characterized by scanning electron microscopy, Fast Fourier Transform and Raman spectroscopy. Moreover, the role of the chemical modification of the metal structures is addressed. Thin oxide layers resulting from working in atmosphere which improve the biocompatibility were indicated by vibration spectra. It is expected that the detailed study of the mechanisms of laser-induced nanostructure formation will stimulate further applications of functionalized surfaces like photocatalysis, selective chemistry and nano-biology.

Messaoudi, H.; Das, S. K.; Lange, J.; Heinrich, F.; Schrader, S.; Frohme, M.; Grunwald, R.

2014-03-01

13

Characterization of Phyllosilicates by LIBS and Laser Raman Spectroscopy  

NASA Astrophysics Data System (ADS)

NIR spectral signatures of phyllosilicates were recognized on Mars with wide distributions from orbit by OMEGA (on Mars Express orbiter) and CRISM (on Mars Reconnaissance Orbiter) observations. On the ground, geochemical and spectral features related to phyllosilicates were identified in rocks at two locations on Columbia Hill at Gusev crater using the data obtained by the Mars Exploration Rover (MER) Spirit. Furthermore, Opportunity rover is currently approaching the Cap of York at Endeavour crater on Meridiani Planum, where the signatures of phyllosilicates (and hydrous sulfates) were seen by CRISM. Laser-Induced Breakdown spectroscopy (LIBS) and Laser Raman spectroscopy will be used for the first time in rover missions in ChemCam on the NASA-MSL (Mars Science Laboratory) and in RLS on the ESA-ExoMars, respectively. As demonstrated by our previous studies, they are very powerful tools for characterizing the geochemistry and mineralogy aspects of the secondary minerals from aqueous alterations, especially hydrous sulfates. This study investigates the potential of LIBS and Raman spectroscopy for identifying and characterizing a variety of phyllosilicates, especially clays. Clay standards from the Clay Mineral Society were used. The LIBS measurements were made in a Planetary Environment and Analysis Chamber (PEACh) under Mars atmospheric pressure and composition, using 1064 nm as the excitation laser wavelength, same as ChemCam. The Raman measurements were made in ordinary laboratory environment using 532 nm as the excitation wavelength, same as RLS. The LIBS data were processed using custom automated software. We performed quantitative analysis of the spectra in order to evaluate the effectiveness of our method in: (a) discriminating between phyllosilicates and other silicates; (b) classifying different types of phyllosilicates (i.e., serpentine, chlorites, clays); and (c) correlating the LIBS-derived elemental abundances with the real chemical compositions of phyllosilicates. At this stage, we concentrated on investigating the LIBS peak area ratios of the Si and H emissions at 390.5 and 656.3 nm, respectively. The results from the first set study are encouraging, and we will be able to support the ChemCam investigation on MSL to classify rocks at distances. As for molecular characterization, we found that examining the Raman spectral patterns and spectral peak positions allows to: (1) classify di-octahedral and tri-octahedral phyllosilicates using the position of Si-O-Si peaks near 700 cm-1; (2) identify a variety of phyllosilicates and clays using H2O/OH peaks in 3000-4000 cm-1 and the fundamental vibration modes of polymerized SiO4 in 1150-200 cm-1; (3) characterize the Fe content in phlogopite-biotite-lepidomelane series using the relative intensities of two Raman peaks near 360 cm-1 and 550 cm-1. These results imply that laser spectroscopy (LIBS and Raman) will be powerful tools for identify, classify, and characterize phyllosilicates on Mars.

Wang, A.; Sobron, P.

2011-12-01

14

Joint analyses by laser-induced breakdown spectroscopy (LIBS) and Raman spectroscopy at stand-off distances  

Microsoft Academic Search

Raman spectroscopy and laser-induced breakdown spectroscopy (LIBS) of solid samples have both been shown to be feasible with sample-to-instrument distances of many meters. The two techniques are very useful together, as the combination of elemental compositions from LIBS and molecular vibrational information from Raman spectroscopy strongly complement each other. Remote LIBS and Raman spectroscopy spectra were taken together on a

Roger C. Wiens; Shiv K. Sharma; Justin Thompson; Anupam Misra; Paul G. Lucey

2005-01-01

15

Remote cure monitoring of polymeric resins by laser Raman spectroscopy  

Microsoft Academic Search

The validity of using Raman spectroscopy to monitor the cure chemistries of amine-cured epoxy is demonstrated by correlating NIR absorbance measurements with Raman measurements for a concentration series of bisphenol-A diglycidylether in its own reaction product with diethylamine. The intensity of a normalized Raman peak at 1240 cm{sup -l}, assigned to the epoxide functionality, was found to be linearly related

K. C. Hong; T. M. Vess; R. E. Lyon; M. L. Myrick

1993-01-01

16

Dehydration of Mars Relevant Ferric Sulfates at High Temperatures Studied by Laser Raman Spectroscopy  

NASA Astrophysics Data System (ADS)

We explored the dehydration of Mars relevant ferric sulfates using laser Raman spectroscopy, which provides important clue to uncover the mystery of relatively rarely detected ferric sulfates on martian surface by orbital remote sensing.

Liu, Y.; Wang, A.

2014-06-01

17

Application of laser Raman spectroscopy in concentration measurements of multiple analytes in human body fluids  

Microsoft Academic Search

The primary goal of these studies was to demonstrate that NIR Raman spectroscopy is feasible as a rapid and reagentless analytic method for clinical diagnostics. Raman spectra were collected on human serum and urine samples using a 785 nm excitation laser and a single-stage holographic spectrometer. A partial east squares method was used to predict the analyte concentrations of interest.

Jianan N. Qu; David Suria; Brian C. Wilson

1998-01-01

18

Analysis of Arctic Carbonates Profiles by Raman Spectroscopy using Exomars Raman Laser Spectrometer  

NASA Astrophysics Data System (ADS)

This work details the analysis performed by Raman spectroscopy on carbonate samples from the Svalbard Islands (Norway) in the Arctic. This place is considered a potential Martian analog because the carbonate formation show close similarities with the formation in ALH84001 meteorite. The results obtained illustrate the performances of the Raman instrument included in the Exomars (ESA) mission.

Sansano, A.; López, G.; Medina, J.; Rull, F.

2011-10-01

19

Tunable excitation source for coherent Raman spectroscopy based on a single fiber laser  

NASA Astrophysics Data System (ADS)

We demonstrate a wavelength tunable optical excitation source for coherent Raman scattering (CRS) spectroscopy based on a single femtosecond fiber laser. Electrically controlled wavelength tuning of Stokes optical pulses was achieved with soliton self frequency shift in an optical fiber, and linear frequency chirping was applied to both the pump and the Stokes waves to significantly improve the spectral resolution. The coherent anti-Stokes Raman scattering (CARS) spectrum of cyclohexane was measured and vibrational resonant Raman peaks separated by 70 cm-1 were clearly resolved. Single laser-based tunable excitation may greatly simplify CRS measurements and extend the practicality of CRS microscopy.

Adany, Peter; Arnett, David C.; Johnson, Carey K.; Hui, Rongqing

2011-10-01

20

Tunable excitation source for coherent Raman spectroscopy based on a single fiber laser.  

PubMed

We demonstrate a wavelength tunable optical excitation source for coherent Raman scattering (CRS) spectroscopy based on a single femtosecond fiber laser. Electrically controlled wavelength tuning of Stokes optical pulses was achieved with soliton self frequency shift in an optical fiber, and linear frequency chirping was applied to both the pump and the Stokes waves to significantly improve the spectral resolution. The coherent anti-Stokes Raman scattering (CARS) spectrum of cyclohexane was measured and vibrational resonant Raman peaks separated by 70?cm(-1) were clearly resolved. Single laser-based tunable excitation may greatly simplify CRS measurements and extend the practicality of CRS microscopy. PMID:22121254

Adany, Peter; Arnett, David C; Johnson, Carey K; Hui, Rongqing

2011-10-31

21

Laser Raman Spectroscopy Of Gap Vibration Of Se Impurity In Natural Mineral Cinnabar From Various Mines  

NASA Astrophysics Data System (ADS)

Natural minerals ?-HgS from various mines have been studied by laser Raman-spectroscopy and resonance Raman-spectroscopy. The crystals differ from each other in the content of selenium impurities included in samples from different mines. Based on Raman spectra and factor-group analyze the classification the first order phonons and then the comparison the results with the results from other works are carried out. The Raman spectra analysis of minerals from various mines show the presence of selenium impurity gap vibration at 203 cm-1 and 226 cm-1 frequencies respectively. On the statistical basis of the Raman measurements, one can conclude that the frequencies of impurities of ?-HgS generally may be used for identifying mines. Low resonance has been fixed as well in impure minerals at spectral band frequency 203 cm-1 characterizing vibrationgap of isomorphic Se impurity in cinnabar.

Gotoshia, Sergo V.; Gotoshia, Lamara V.

2011-09-01

22

Miniaturized diode laser-based light sources for in-situ shifted excitation Raman difference spectroscopy  

NASA Astrophysics Data System (ADS)

Weak Raman bands are often covered by pronounced background signals due to fluorescence or Rayleigh scattering. Several techniques to separate Raman lines from the background are known. In this paper, diode laser based light sources will be presented suitable for shifted excitation Raman difference spectroscopy (SERDS). The two wavelengths are realized by varying the injection current, by addressing two micro-integrated ECLs or by temperature tuning. Due to the freedom of choice in the wavelengths using diode lasers, the emission wavelength can be selected with respect to the addressed application (e.g. the required penetration depth) or the plasmonic resonances of the substrates for surface enhanced Raman spectroscopy. Devices were developed for the wavelengths 488 nm, 671 nm, and 785 nm. The two emission wavelengths each were selected to have a spectral distance of 10 cm-1 according to the typical width of Raman lines of solid or liquid samples. Output powers between 20 mW for the shorter wavelength devices and 200 mW for the red emitting lasers were achieved at electrical power consumptions below 1 W. With a footprint of only 25 x 25 mm2 including all collimation and filter elements, these devices are well suited for portable applications. The diode lasers were implemented into Raman measurement systems. The SERDS signal-to-background ratio was improved by several orders of magnitude.

Sumpf, Bernd; Maiwald, Martin; Sowoidnich, Kay; Kronfeldt, Heinz-Detlef

2013-05-01

23

Red emitting monolithic dual wavelength DBR diode lasers for shifted excitation Raman difference spectroscopy  

NASA Astrophysics Data System (ADS)

Raman lines are often obscured by background light or fluorescence especially when investigating biological samples or samples containing impurities. Shifted excitation Raman difference spectroscopy (SERDS) is a technique to overcome this. By exciting the sample with two slightly shifted wavelengths, it is possible to separate the Raman lines and distortions. In this paper, monolithic dual wavelength DBR diode lasers meeting the demands of Raman spectroscopy and SERDS will be presented. The wavelengths are stabilized and selected by using deeply-etched 10th order surface gratings with different periods manufactured using i-line wafer stepper lithography. Two possible resonator concepts, i.e. a mini-array of two parallel DBR RW-lasers and a Y-branch DBR laser, will be compared. Established excitation wavelengths for Raman spectroscopy at 671 nm and 785 nm are chosen. The total laser length is 3 mm; the ridge width is 2.2 ?m for the 785 nm devices and 5 ?m for the 671 nm lasers. The length of the DBR gratings is 500 ?m. The devices at 671 nm reach output powers up to 100 mW having an emission width smaller than 12 pm (FWHM). The 785 nm lasers show output powers up to 200 mW and a narrow emission below 22 pm. For the dual wavelength lasers the spectral distance between the two excitation lines is about 0.5 nm as targeted. The power consumption at both wavelengths is below 1 W. These data proof that the devices are well suited for their application in portable Raman measurement systems such as handheld devices using SERDS.

Sumpf, B.; Maiwald, M.; Müller, A.; Bugge, F.; Fricke, J.; Ressel, P.; Pohl, J.; Erbert, G.; Tränkle, G.

2014-02-01

24

Raman spectroscopy study of laser-shocked tatb-based explosives  

NASA Astrophysics Data System (ADS)

We have developed a nanosecond single-shot Raman spectroscopy experiment to study the initiation and decomposition mechanisms of heterogeneous solid explosives under shock compression. The laser-driven flyer plate technique was used to generate shock waves on TATB-based explosives samples. Photon Doppler Velocimetry (PDV) measurements were performed to estimate the generated shock pressures. The first Raman spectra obtained under shock compression are presented here. The shifts observed for the different Raman peaks are consistent with those observed under static pressure.

Hebert, Philippe; Bouyer, Viviane; Doucet, Michel; Rideau, Joël; Terzulli, Louis-Pierre

2012-03-01

25

Novel probe for laser-induced breakdown spectroscopy and Raman measurements using an imaging optical fiber  

SciTech Connect

A fiber-optic probe designed for remote laser-induced breakdown spectroscopy (LIBS), Raman spectroscopy, and Raman imaging has been developed for the microanalysis of solid samples. The probe incorporates both single-strand optical fibers and an image guide and allows atomic emission and Raman analysis of any spot on a solid sample within a 5 mm diameter field of view. The real-time sample imaging aspects of the probe are demonstrated by measuring LIBS spectra from different regions of a granite sample and by measuring the Raman spectra of individual TiO{sub 2} and Sr(NO{sub 3}){sub 2} particles on a soil substrate. The ability to obtain remote Raman images of the TiO{sub 2} and Sr(NO{sub 3}){sub 2} particles on the soil substrate is also demonstrated. In this paper we discuss the design and implementation of the fiber-optic probe for obtaining LIBS spectra, Raman spectra, and Raman images. {copyright} {ital 1998} {ital Society for Applied Spectroscopy}

Marquardt, B.J.; Stratis, D.N.; Angel, S.M. [Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208 (United States)] [Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208 (United States); Cremers, D.A. [Group CST-1, MS J565. Chemical Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Group CST-1, MS J565. Chemical Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

1998-09-01

26

Surface-enhanced Raman spectroscopy (SERS) using Ag nanoparticle films produced by pulsed laser deposition  

NASA Astrophysics Data System (ADS)

Thin silver nanoparticle films, of thickness 7 nm, were deposited onto glass microslides using pulsed laser deposition (PLD). The films were then characterised using UV-vis spectroscopy and scanning transmission electron microscopy before Rhodamine 6G was deposited onto them for investigation using surface-enhanced Raman spectroscopy (SERS). The sensitivity obtained using SERS was compared to that obtained using a colloidal silver suspension and also to a commercial SERS substrate. The reproducibility of the films is also examined using statistical analysis.

Smyth, C. A.; Mirza, I.; Lunney, J. G.; McCabe, E. M.

2013-01-01

27

Shifted excitation Raman difference spectroscopy using a dual-wavelength DBR diode laser at 671 nm  

NASA Astrophysics Data System (ADS)

Shifted excitation Raman difference spectroscopy (SERDS) using a dual-wavelength laser diode laser as excitation light source at 671 nm is presented. This device has a size of 3 mm x 0.5 mm and contains two laser cavities with wavelengths adjusted by distributed Bragg reflector (DBR) gratings as rear side mirrors. An integrated Y-branch coupler guides the emission into a common output aperture. The two wavelengths are centered at 671 nm with a well-defined spectral spacing of about 10 cm-1. An output power up to 100 mW is achieved. Raman experiments using polystyrene as test sample and ambient light to disturb the Raman signals demonstrate the suitability of such light source for SERDS.

Maiwald, M.; Fricke, J.; Ginolas, A.; Pohl, J.; Sumpf, B.; Erbert, G.; Tränkle, G.

2014-02-01

28

Simultaneous Raman spectroscopy-laser-induced breakdown spectroscopy for instant standoff analysis of explosives using a mobile integrated sensor platform.  

PubMed

A novel experimental design combining Raman spectroscopy and laser-induced breakdown spectroscopy (LIBS) in a unique integrated sensor is described. The sensor presented herein aims to demonstrate the applicability of a hybrid dual Raman-LIBS system as an analytical tool for the standoff analysis of energetic materials. Frequency-doubled 532 nm Nd:YAG nanosecond laser pulses, first expanded and then focused using a 10x beam expander on targets located at 20 m, allowed simultaneous acquisition of Raman-LIBS spectra for 4-mononitrotoluene (MNT), 2,6-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT), cyclotrimethylenetrinitramine (RDX), C4 and H15 (plastic explosives containing 90% and 75% of RDX by weight, respectively), and Goma2-ECO (Spanish denominated dynamite class high explosive mainly composed of ammonium nitrate, nitroglycol, and dinitrotoluene among other compounds), sodium chlorate, and ammonium nitrate. With the use of a Cassegrain telescope, both Raman and LIBS signals from the same laser pulses were collected and conducted through a bifurcated optical fiber into two identical grating spectrographs coupled to intensified charge-coupled device (iCCD) detectors. With the use of the appropriate timing for each detection mode, adjustment of the laser power on the beam focal conditions is not required. The ability of the present single hybrid sensor to simultaneously acquire, in real time, both molecular and multielemental information from the same laser pulses on the same cross section of the sample at standoff distances greatly enhances the information power of this approach. PMID:20085236

Moros, Javier; Lorenzo, Juan Antonio; Lucena, Patricia; Tobaria, Luciano Miguel; Laserna, José Javier

2010-02-15

29

Analysis of RBC damage using laser tweezers Raman spectroscopy (LTRS) during femtosecond laser optical trapping  

Microsoft Academic Search

We monitored cell viability and damage under femtosecond laser irradiation using aser weezers Raman pectroscopy (LTRS) which is becoming a powerful tool for the analysis of biological materials. Femtosecond lasers are more frequently used as a light source for optical tweezers since they enable nonlinear optical phenomena such as two-photon absorption or second harmonic generation trapping. Femtosecond laser optical trapping

Sung-bin Ju; Jin-woo Pyo; Jae-young Jang; Seungduk Lee; Beop-Min Kim

2008-01-01

30

Laser Heated High Density Fluids Probed by Coherent Anti-Stokes Raman Spectroscopy  

SciTech Connect

We describe an integrated experimental method of Coherent Antistoke Raman Spectroscopy (CARS), laser-heating and diamond-anvil cell (DAC) technologies probing molecular vibrations of transparent molecular fluids at the pressure-temperature conditions of energetic detonation and Giant planetary interiors. In this method, we use a microfabricated metal toroid to conductively heat a surrounding transparent sample in a DAC, using a CW Nd:YLF laser. The laser is operated at a TEM{sub 01*} mode to match the shape of the toroid and thus produces a uniform heating area. The CARS probe utilizes two pulsed lasers with similar cavity lengths: a commercial narrow-band mode-locked Q-switched Nd:YAG laser and a home-built broadband dye laser. A strong CARS signal is then produced from the sample in the central region of laser-heated metal toroid where the two laser pulses spatially and temporally coincide. In this paper, we will demonstrate that this technique is capable of producing high quality vibrational spectra from nitrogen fluid above 2000 K and 13 GPa, where the application of spontaneous Raman spectroscopy is limited because of intense thermal radiation.

Baer, B J; Yoo, C

2004-05-19

31

Laser Raman spectroscopy studies of beta-eucryptite crystallization from glass  

NASA Astrophysics Data System (ADS)

In the initial stadium of crystallization of glass composed of Li 2O.Al 2O 3.2SiO 2 along with beta-eucryptite additional intermediate phases appear. They disappear in course of further devitrification giving as the final product the beta-eucryptite phase. This irreversible transition connected with ordering of SiAlO 4 framework was investigated by laser Raman spectroscopy. Obtained results allow for drawing conclusions about both the stoichiometry of the intermediate phases and the coordination number of aluminium forcoming in eucryptite glass. The group theoretical analysis was carried out. An assignment of the Raman bands to the appropriate modes was attempted.

Görlich, E.; Proniewicz, L. M.

32

Three Powerful Research Tools from Single Cells into Single Molecules: AFM, Laser Tweezers, and Raman Spectroscopy  

Microsoft Academic Search

By using three physical techniques (atomic force microscopy (AFM), laser tweezers, and Raman spectroscopy), many excellent\\u000a works in single-cell\\/molecule research have been accomplished. In this review, we present a brief introduction to the principles\\u000a of these three techniques, and their capabilities toward single-cell\\/molecule research are highlighted. Afterward, the advances\\u000a in single-cell\\/molecule research that have been facilitated by these three techniques

Yongkuan Wu; Kun Liu; Kedong Song; Shi Pan

33

New Developments in Raman Spectroscopy with Lasers: Electronic Transitions.  

National Technical Information Service (NTIS)

A discussion is given of the Raman spectra of single crystals of yttrium gallium garnet (YGaG), of ytterbrium gallium garnet (YbGaG), and of Yb:YGaG. From a comparison of the spectra it has been possible to separate the phonon spectra of the host lattices...

J. A. Koningstein

1968-01-01

34

Analysis of RBC damage using laser tweezers Raman spectroscopy (LTRS) during femtosecond laser optical trapping  

NASA Astrophysics Data System (ADS)

We monitored cell viability and damage under femtosecond laser irradiation using aser weezers Raman pectroscopy (LTRS) which is becoming a powerful tool for the analysis of biological materials. Femtosecond lasers are more frequently used as a light source for optical tweezers since they enable nonlinear optical phenomena such as two-photon absorption or second harmonic generation trapping. Femtosecond laser optical trapping similar to thee CW laser optical trapping except that optical damage can be easily induced due to extremely high peak power of femtosecond pulses. We monitored the Raman signal changes as a marker for optical damage. We used red blood cell (RBC) as a target sample and first used the CW laser beams to trap the RBC from the bottom of the chamber. After the trapped RBC is moved to a desired depth, we switched the laser mode to mode-locked mode and monitored the Raman signals as a function of the laser irradiation time. It was observed that the Raman shift at 1543 cm -1 may be a good marker for optical damage both for CW and femtosecond laser trapping.

Ju, Sung-bin; Pyo, Jin-woo; Jang, Jae-young; Lee, Seungduk; Kim, Beop-Min

2008-03-01

35

Remote pulsed laser Raman spectroscopy system for detecting water, ice, and hydrous minerals  

NASA Astrophysics Data System (ADS)

For exploration of planetary surfaces, detection of water and ice is of great interest in supporting existence of life on other planets. Therefore, a remote Raman spectroscopy system was demonstrated at NASA Langley Research Center in collaboration with the University of Hawaii for detecting ice-water and hydrous minerals on planetary surfaces. In this study, a 532 nm pulsed laser is utilized as an excitation source to allow detection in high background radiation conditions. The Raman scattered signal is collected by a 4-inch telescope positioned in front of a spectrograph. The Raman spectrum is analyzed using a spectrograph equipped with a holographic super notch filter to eliminate Rayleigh scattering, and a holographic transmission grating that simultaneously disperses two spectral tracks onto the detector for higher spectral range. To view the spectrum, the spectrograph is coupled to an intensified charge-coupled device (ICCD), which allows detection of very weak Stokes line. The ICCD is operated in gated mode to further suppress effects from background radiation and long-lived fluorescence. The sample is placed at 5.6 m from the telescope, and the laser is mounted on the telescope in a coaxial geometry to achieve maximum performance. The system was calibrated using the spectral lines of a Neon lamp source. To evaluate the system, Raman standard samples such as calcite, naphthalene, acetone, and isopropyl alcohol were analyzed. The Raman evaluation technique was used to analyze water, ice and other hydrous minerals and results from these species are presented.

Garcia, Christopher S.; Abedin, M. Nurul; Sharma, Shiv K.; Misra, Anupam K.; Ismail, Syed; Singh, Upendra N.; Refaat, Tamer F.; Elsayed-Ali, Hani E.; Sandford, Steve P.

2006-09-01

36

Raman spectroscopy of iron oxides and (oxy)hydroxides at low laser power and possible applications in environmental magnetic studies  

Microsoft Academic Search

Raman spectroscopy uses the inelastic scattering of electromagnetic radiation by molecules. Monochromatic light of a laser interacts with phonons, the vibrational modes in the crystal lattice. The energy of the scattered light is shifted by the scattering. The shifts in energy yield the Raman spectrum that is specific for each mineral because the phonons are specific for each mineral. In

Monika Hanesch

2009-01-01

37

Multispectral diode laser based shifted excitation Raman difference spectroscopy for biological sample identification  

NASA Astrophysics Data System (ADS)

Raman spectroscopy is a well established analytical method with applications in many areas, e.g. analysis of biological samples. To overcome the problem of an undesired fluorescence background masking the Raman signals we present a multi-spectral approach using shifted excitation Raman difference spectroscopy (SERDS). For our investigations we applied microsystem diode lasers which realize two slightly shifted excitation wavelengths required to perform SERDS at 488 nm, 671 nm, and 785 nm. The emission at 488 nm with an optical power of up to 30 mW and a spectral shift of 0.3 nm (12 cm-1) is realized by frequency doubling of a 976 nm distributed feedback (DFB) diode laser. The 671 nm laser diode contains two separate laser cavities (spectral shift: 0.7 nm (13 cm-1)) each incorporating a volume Bragg grating as frequency selective element. In that case, optical powers up to 50 mW can be obtained. For investigations at 785 nm we used a DFB laser with a maximum optical power of 110 mW and a spectral shift of 0.5 nm (7 cm-1). Meat, fat tissue, connective tissue and bones from pork and beef were used as test samples to demonstrate the effective background removal using SERDS. For all three wavelengths integration times of only 5 - 10 seconds were necessary showing the possibility of SERDS for rapid sample identification. A comparison with conventional Raman spectra is given pointing out the improvement of spectral quality. The applicability of SERDS for other analytical applications, e.g. medical diagnosis will be discussed.

Sowoidnich, Kay; Kronfeldt, Heinz-Detlef

2012-05-01

38

Broadband coherent anti-Stokes Raman spectroscopy with a modeless dye laser.  

PubMed

We develop a modeless dye laser for broadband coherent anti-Stokes Raman spectroscopy (CARS) and investigate the operational characteristics of the modeless laser. The energy efficiency of the modeless laser is 6%, and the beam divergence is 0.65 mrad. We construct a compact movable CARS system with the modeless laser and a graphite tube furnace to assess the accuracy of the CARS temperature. It is found that the difference between the averaged CARS temperature and the radiation temperature measured with an optical pyrometer is <2% at a temperature range from 1000 to 2400 K. We also measure the averaged CARS temperature drift owing to the variation of the spectral distribution of the modeless laser, which is <1.5% during 5 h of operation. PMID:18259536

Hahn, J W; Park, C W; Park, S N

1997-09-20

39

Laser Raman spectroscopy of calf bone Gla protein.  

PubMed

The Raman spectra of solid calf bone Gla protein in its native state, decarboxylated, with reduced disulfide bond, and as the calcium salt have been obtained. The amide I and III bands are consistent with the presence of alpha-helical, antiparallel beta-sheet, and random-coil regions in all four forms of bone Gla protein. Random coil appears to be the prevailing conformation. The protein conformation in the calcium salt exhibits an increased alpha-helix character compared to the native protein. No significant differences in the backbone conformation are observed among the native, decarboxylated, and reduced forms of bone Gla protein. The Raman band at 504 cm-1, due to the disulfide stretching vibration in native bone Gla protein, is unchanged upon decarboxylation and binding of Ca2+ to the protein, indicating the absence of any changes in the conformation around the disulfide bond in these protein species. The tryptophan and most of the tyrosine residues appear to be 'exposed' rather than 'buried' in the native protein. The environment of at least one of the phenylalanine residues changes when Ca2+ is bound to bone Gla protein. A small change also appears to take place in the environment of at least one of the tyrosine residues upon Ca2+-binding or reduction of the disulfide bond. PMID:6601495

Dendramis, A L; Poser, J W; Schwinn, E W

1983-02-15

40

Determination of beta-turn conformation by laser Raman spectroscopy.  

PubMed Central

To correlate the Raman frequencies of the amide I and III bands to beta-turn structures, three peptides shown to contain beta-turn structure by x-ray diffraction and NMR were examined. The compounds examined were tertiary (formula: see text). The amide I band of these compounds is seen at 1,668, 1,665, and 1,677 cm-1, and the amide III band appears at 1,267, 1,265, and 1,286 cm-1, respectively. Thus, it is concluded that the amide I band for type III beta-turn structure appears in the range between 1,665 and 1,677 cm-1 and the amide III band between 1,265 and 1,286 cm-1.

Ishizaki, H; Balaram, P; Nagaraj, R; Venkatachalapathi, Y V; Tu, A T

1981-01-01

41

Raman spectroscopy study of laser-shocked TATB-based explosives  

NASA Astrophysics Data System (ADS)

We have developed a single-pulse Raman spectroscopy experiment dedicated to the study of laser-shocked explosives. The shocks were generated using the laser-driven flyer technique. The nanosecond pulse of a Nd:YAG laser (? = 1064 nm) was focused on a BK7 substrate coated with an ablation and an aluminium (Al) layer. The Al layer was used as the flyer. Our set-up can provide flyer velocities in the range 1500 to 3000 m/s with 15 ?m thick Al foils which yields to maximum peak pressure of about 20 GPa on TATB samples. Single-shot Raman spectroscopy of shocked samples was performed using the second harmonic of a nanosecond Nd:YAG laser (? = 532 nm) focused on the back side of the samples through a glass window. In order to estimate the pressure of the probed sample, measurements of the particle velocity at the explosive-window interface were performed at the same time using the Photon Doppler Velocimetry system developed at CEA. Hydrodynamic simulations were also carried out. The first results obtained with this set-up on pressed samples of TATB based explosives are presented in this paper.

Hebert, Philippe; Bouyer, Viviane; Rideau, Joel; Doucet, Michel; Terzulli, Louis-Pierre

2011-06-01

42

Characterization of azurite and lazurite based pigments by laser induced breakdown spectroscopy and micro-Raman spectroscopy  

NASA Astrophysics Data System (ADS)

The most commonly used blue pigments in medieval manuscripts are azurite and lapis-lazuli. The first one is a copper-based pigment; the coloring compound of the latter is lazurite, a sodium silico?aluminate in a sulfur matrix. Knowledge of the chemical composition of the materials is essential for the study of illuminated manuscripts. In this paper, micro-Raman and LIBS have been used for the study of azurite and lapis-lazuli, as well as different mixtures of these pigments applied to parchment to simulate an illuminated manuscript. The results of our work show the importance of using more than one technique for a good comprehension of a manuscript. In particular, the opportunity of combining elemental information (obtained from laser induced breakdown spectroscopy) and vibrational spectroscopy information (obtained from Raman) will be fully exploited.

Bicchieri, M.; Nardone, M.; Russo, P. A.; Sodo, A.; Corsi, M.; Cristoforetti, G.; Palleschi, V.; Salvetti, A.; Tognoni, E.

2001-06-01

43

Organic semiconductor distributed feedback laser as excitation source in Raman spectroscopy using free-beam and fibre coupling  

NASA Astrophysics Data System (ADS)

Enabled by the broad spectral gain and the efficient energy conversion in the active material, organic semiconductor lasers are promising for spectroscopic applications and have been recently applied for high resolution absorption and transmission spectroscopy. Here, we present the application of organic semiconductor DFB laser (DFB-OSL) as excitation source in Raman spectroscopy. Utilizing an efficient small molecule blend of tris (8-hydroxyquinoline) aluminum (Alq3) doped with the laser dye 4-(dicyano-methylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM), our encapsulated DFB-OSL achieved a high slope efficiency of 7.6%. The organic lasers were tested in the inverted and upright Raman microscope setups, using free-beam and fibre coupling, respectively. In the free-beam configuration, the emission beam was guided directly into an inverted microscope. Employing a spectrally tunable DFBOSL as the excitation source, we measured the Raman spectra of sulfur and improved the Raman signals for a given optical filter configuration. In the fibre coupling configuration, the organic laser was coupled into a 50 ?m multi-mode optical fibre with an efficiency of 70 %. We utilized a round-to-line fibre-bundle for an efficient collection and transfer of Raman light to a spectrograph, by keeping a sufficient spectral resolution. Raman tests were performed on cadmium sulfide and cyclohexane. Our novel fibre-coupled organic laser provides a modular laboratory Raman system.

Liu, Xin; Lebedkin, Sergei; Mappes, Timo; Köber, Sebastian; Koos, Christian; Kappes, Manfred; Lemmer, Uli

2014-05-01

44

First experimental study of self-forming synthetic lipids by confocal laser tweezers Raman spectroscopy  

NASA Astrophysics Data System (ADS)

We present the first experimental study of self-forming synthetic lipids, trademarked as QuSomesTM, using Raman spectroscopy in the spectral range of 500 to 3100 cm-1. Raman spectra of these new artificial lipids composed of 1,2- dimyristoyl-rac-glycerol-3-dodecaethylene glycol (GDM-12) and 1,2-dioleoyl-rac-glycerol-3-dodecaethylene glycol (GDO-12) have been obtained in pure form and in aqueous suspensions with Phosphate Buffered Saline (PBS) by using an inverted confocal laser-tweezers-Raman-microscopy system. This spectrometer works with an 80 mW diode-pumped solid-state laser, operating at a wavelength of 785 nm in the TEM00 mode. The laser is used both for optical trapping and Raman excitation. The two amphiphiles considered in this study, differ in their hydrophobic chain length and contain similar units of hydrophilic polyethylene glycol (PEG) head groups. Such synthetic PEG coated lipids exist in liquid form at room temperature and spontaneously form liposomes (nano type vesicles) upon hydration. In this work, we have focused on the band assignments for the spectra of single QuSomesTM nano particles in pure form and in aqueous media acquired by means of Raman spectroscopy. In particular, we have found that the most prominent peaks in the studied spectral region are dominated by vibrational modes arising from C-C and C-H bonds. Furthermore, we have noticed that some of the distinct peaks observed below 1800 cm-1 in pure sample are preserved in aqueous environment. These retained intense bands are located at 1449, 1128, 1079, and 1065 cm-1. This effect might be due to the strong chain-chain interactions, because the chains have to orient themselves and become tightly packed in the vesicles wall rather than adopt random orientations in bulk. This technique has proven to be an excellent tool to establish the fingerprint region revealing the molecular structure and conformation of QuSomesTM particles. The Raman spectroscopic data of these novel lipids and its vesicles formed in suspensions confirm high stability and are therefore considered as potential candidate for varieties of future applications including lipid based novel substances and drug delivery systems.

Bista, Rajan K.; Bruch, Reinhard F.

2008-08-01

45

Raman spectroscopy of organic dyes adsorbed on pulsed laser deposited silver thin films  

NASA Astrophysics Data System (ADS)

The results of a surface-enhanced Raman scattering (SERS) study performed on representative organic and inorganic dyes adsorbed on silver nanostructured thin films are presented and discussed. Silver thin films were deposited on glass slides by focusing the beam from a KrF excimer laser (wavelength 248 nm, pulse duration 25 ns) on a silver target and performing the deposition in a controlled Ar atmosphere. Clear Raman spectra were acquired for dyes such as carmine lake, garanza lake and brazilwood overcoming their fluorescence and weak Raman scattering drawbacks. UV-visible absorption spectroscopy measurements were not able to discriminate among the different chromophores usually referred as carmine lake (carminic, kermesic and laccaic acid), as brazilwood (brazilin and brazilein) and as garanza lake (alizarin and purpurin). SERS measurements showed that the analyzed samples are composed of a mixture of different chromophores: brazilin and brazilein in brazilwood, kermesic and carminic acid in carmine lake, alizarin and purpurin in garanza lake. Detection at concentration level as low as 10-7 M in aqueous solutions was achieved. Higher Raman intensities were observed using the excitation line of 632.8 nm wavelength with respect to the 785 nm, probably due to a pre-resonant effect with the molecular electronic transitions of the dyes.

Fazio, E.; Neri, F.; Valenti, A.; Ossi, P. M.; Trusso, S.; Ponterio, R. C.

2013-08-01

46

Monitoring trehalose uptake and conversion by single bacteria using laser tweezers Raman spectroscopy.  

PubMed

Having the ability to monitor metabolic activity at the scale of single bacterial cells noninvasively would enable us to follow changes in the distribution of activity in bacterial systems which is of major importance for topics such as integration of metabolism and development, metabolic engineering, microbial activity and drug resistance, cell-cell interactions, and quorum sensing. Here, we used laser tweezers Raman spectroscopy to monitor the in vivo real-time uptake and conversion of trehalose by single bacterial cells. This approach can be used for the quantitative determination of sugar uptake by a single bacterium and its metabolic response to the sugar application with time. We show that uptake of trehalose can be quantified in single living bacterial cells held in place by an optical trap while simultaneously collecting Raman spectra upon application of sugar to the medium. This technique yields real-time chemical information in a label-free manner, thus eliminating the limitations of toxicity of the isotopic probes common in studying transport processes. It can substitute the laborious and time-consuming analytical evaluation. Although the single-cell Raman spectroscopy method demonstrated here is focused on the study of trehalose uptake by Sinorhizobium meliloti, the demonstrated approach is applicable to many different organisms and carbohydrates in general. PMID:23796054

Avetisyan, Anna; Jensen, John Beck; Huser, Thomas

2013-08-01

47

Quantitative fiber-optic Raman spectroscopy for tissue Raman measurements  

NASA Astrophysics Data System (ADS)

Molecular profiling of tissue using near-infrared (NIR) Raman spectroscopy has shown great promise for in vivo detection and prognostication of cancer. The Raman spectra measured from the tissue generally contain fundamental information about the absolute biomolecular concentrations in tissue and its changes associated with disease transformation. However, producing analogues tissue Raman spectra present a great technical challenge. In this preliminary study, we propose a method to ensure the reproducible tissue Raman measurements and validated with the in vivo Raman spectra (n=150) of inner lip acquired using different laser powers (i.e., 30 and 60 mW). A rapid Raman spectroscopy system coupled with a ball-lens fiber-optic Raman probe was utilized for tissue Raman measurements. The investigational results showed that the variations between the spectra measured with different laser powers are almost negligible, facilitating the quantitative analysis of tissue Raman measurements in vivo.

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

2014-03-01

48

Planetary Surface Analysis Using Fast Laser Spectroscopic Techniques: Combined Microscopic Raman, LIBS, and Fluorescence Spectroscopy  

NASA Astrophysics Data System (ADS)

In situ exploration of planetary surfaces has to date required multiple techniques that, when used together, yield important information about their formation histories and evolution. We present a time-resolved laser spectroscopic technique that could potentially collect complementary sets of data providing information on mineral structure, composition, and hydration state. Using a picosecond-scale pulsed laser and a fast time-resolved detector we can simultaneously collect spectra from Raman, Laser Induced Breakdown Spectroscopy (LIBS), and fluorescence emissions that are separated in time due to the unique decay times of each process. The use of a laser with high rep rate (40 KHz) and low pulse energy (1 ?J/pulse) allows us to rapidly collect high signal to noise Raman spectra while minimizing sample damage. Increasing the pulse energy by about an order of magnitude creates a microscopic plasma near the surface and enables the collection of LIBS spectra at an unusually high rep rate and low pulse energy. Simultaneously, broader fluorescence peaks can be detected with lifetimes varying from nanosecond to microsecond. We will present Raman, LIBS, and fluorescence spectra obtained on natural mineral samples such as sulfates, clays, pyroxenes and carbonates that are of interest for Mars mineralogy. We demonstrate this technique using a photocathode-based streak camera detector as well as a newly-developed solid state Single Photon Avalanche Diode (SPAD) sensor array based on Complementary Metal-Oxide Semiconductor (CMOS) technology. We will discuss the impact of system design and detector choice on science return of a potential planetary surface mission, with a specific focus on size, weight, power, and complexity. The research described here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (NASA).

Blacksberg, J.; Rossman, G. R.; Maruyama, Y.; Charbon, E.

2011-12-01

49

Application of Diode-Laser Raman Spectroscopy for In situ Investigation of Meat Spoilage  

Microsoft Academic Search

Raman spectroscopy is well suited for non-invasive and non-destructive analysis. The spectra provide detailed information\\u000a about the composition of the matter like a fingerprint on molecular level. Here, we have applied Raman spectroscopy for the\\u000a characterization of meat spoilage. For this purpose, pork chops (musculus longissimus dorsi) were ice-stored at 5 °C, and\\u000a time-dependent Raman spectra were measured daily up to

Kay Sowoidnich; Heinar Schmidt; Martin Maiwald; Bernd Sumpf; Heinz-Detlef Kronfeldt

2010-01-01

50

Raman Spectroscopy in High Temperature Chemistry  

Microsoft Academic Search

Raman spectroscopy (largely because of advances in laser and detector technology) is assuming a rapidly expanding role in many areas of research. This paper reviews the contribution of Raman spectroscopy in high temperature chemistry including molecular spectroscopy on static systems and gas diagnostic measurements on reactive systems. An important aspect of high temperature chemistry has been the identification and study

M. C. Drake; G. M. Rosenblatt

1979-01-01

51

Fast single-photon avalanche diode arrays for laser Raman spectroscopy.  

PubMed

We incorporate newly developed solid-state detector technology into time-resolved laser Raman spectroscopy, demonstrating the ability to distinguish spectra from Raman and fluorescence processes. As a proof of concept, we show fluorescence rejection on highly fluorescent mineral samples willemite and spodumene using a 128×128 single-photon avalanche diode (SPAD) array with a measured photon detection efficiency of 5%. The sensitivity achieved in this new instrument architecture is comparable to the sensitivity of a technically more complicated system using a traditional photocathode-based imager. By increasing the SPAD active area and improving coupling efficiency, we expect further improvements in sensitivity by over an order of magnitude. We discuss the relevance of these results to in situ planetary instruments, where size, weight, power, and radiation hardness are of prime concern. The potential large-scale manufacturability of silicon SPAD arrays makes them prime candidates for future portable and in situ Raman instruments spanning numerous applications where fluorescence interference is problematic. PMID:21931428

Blacksberg, Jordana; Maruyama, Yuki; Charbon, Edoardo; Rossman, George R

2011-09-15

52

Remote Raman - laser induced breakdown spectroscopy (LIBS) geochemical investigation under Venus atmospheric conditions  

SciTech Connect

The extreme Venus surface temperatures ({approx}740 K) and atmospheric pressures ({approx}93 atm) create a challenging environment for surface missions. Scientific investigations capable of Venus geochemical observations must be completed within hours of landing before the lander will be overcome by the harsh atmosphere. A combined remote Raman - LIBS (Laser Induced Breakdown Spectroscopy) instrument is capable of accomplishing the geochemical science goals without the risks associated with collecting samples and bringing them into the lander. Wiens et al. and Sharma et al. demonstrated that both analytical techniques can be integrated into a single instrument capable of planetary missions. The focus of this paper is to explore the capability to probe geologic samples with Raman - LIBS and demonstrate quantitative analysis under Venus surface conditions. Raman and LIBS are highly complementary analytical techniques capable of detecting both the mineralogical and geochemical composition of Venus surface materials. These techniques have the potential to profoundly increase our knowledge of the Venus surface composition, which is currently limited to geochemical data from Soviet Venera and VEGA landers that collectively suggest a surface composition that is primarily tholeiitic basaltic with some potentially more evolved compositions and, in some locations, K-rich trachyandesite. These landers were not equipped to probe the surface mineralogy as can be accomplished with Raman spectroscopy. Based on the observed compositional differences and recognizing the imprecise nature of the existing data, 15 samples were chosen to constitute a Venus-analog suite for this study, including five basalts, two each of andesites, dacites, and sulfates, and single samples of a foidite, trachyandesite, rhyolite, and basaltic trachyandesite under Venus conditions. LIBS data reduction involved generating a partial least squares (PLS) model with a subset of the rock powder standards to quantitatively determine the major elemental abundance of the remaining samples. PLS analysis suggests that the major element compositions can be determined with root mean square errors ca. 5% (absolute) for SiO{sub 2}, Al{sub 2}O{sub 3}, Fe{sub 2}O{sub 3}(total), MgO, and CaO, and ca. 2% or less for TiO{sub 2}, Cr{sub 2}O{sub 3}, MnO, K{sub 2}O, and Na{sub 2}O. Finally, the Raman experiments have been conducted under supercritical CO{sub 2} involving single-mineral and mixed-mineral samples containing talc, olivine, pyroxenes, feldspars, anhydrite, barite, and siderite. The Raman data have shown that the individual minerals can easily be identified individually or in mixtures.

Clegg, Sanuel M [Los Alamos National Laboratory; Barefield, James E [Los Alamos National Laboratory; Humphries, Seth D [Los Alamos National Laboratory; Wiens, Roger C [Los Alamos National Laboratory; Vaniman, D. T. [Los Alamos National Laboratory; Sharma, S. K. [UNIV OF HAWAII; Misra, A. K. [UNIV OF HAWAII; Dyar, M. D. [MT. HOLYOKE COLLEGE; Smrekar, S. E. [JET PROPULSION LAB.

2010-12-13

53

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

NASA Technical Reports Server (NTRS)

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.

Shirley, John A.

1990-01-01

54

In situ high P-T Raman spectroscopy and laser heating of carbon dioxide  

NASA Astrophysics Data System (ADS)

In situ high P-T Raman spectra of solid CO2 up to 67 GPa and 1660 K have been measured, using a micro-optical spectroscopy system coupled with a Nd:YLF laser heating system in diamond anvil cells. A metallic foil was employed to efficiently absorb the incoming Nd:YLF laser and heat the sample. The average sample temperature was accurately determined by detailed balance from the anti-Stokes/Stokes ratio, and was compared to the temperature of the absorber determined by fitting the thermal radiation spectrum to the Planck radiation law. The transformation temperature threshold and the transformation dynamics from the molecular phases III and II to the polymeric phase V, previously investigated only by means of temperature quench experiments, was determined at different pressures. The P-T range of the transformation, between 640 and 1100 K in the 33-65 GPa pressure interval, was assessed to be a kinetic barrier rather than a phase boundary. These findings lead to a new interpretation of the high P-T phase diagram of carbon dioxide. Furthermore, our approach opens a new way to perform quantitative in situ Raman measurements under extremely high pressures and temperatures, providing unique information about phase relations and structural and thermodynamic properties of materials under these conditions.

Santoro, Mario; Lin, Jung-Fu; Mao, Ho-Kwang; Hemley, Russell J.

2004-08-01

55

In situ high P-T Raman spectroscopy and laser heating of carbon dioxide.  

PubMed

In situ high P-T Raman spectra of solid CO(2) up to 67 GPa and 1,660 K have been measured, using a micro-optical spectroscopy system coupled with a Nd:YLF laser heating system in diamond anvil cells. A metallic foil was employed to efficiently absorb the incoming Nd:YLF laser and heat the sample. The average sample temperature was accurately determined by detailed balance from the anti-Stokes/Stokes ratio, and was compared to the temperature of the absorber determined by fitting the thermal radiation spectrum to the Planck radiation law. The transformation temperature threshold and the transformation dynamics from the molecular phases III and II to the polymeric phase V, previously investigated only by means of temperature quench experiments, was determined at different pressures. The P-T range of the transformation, between 640 and 1,100 K in the 33-65 GPa pressure interval, was assessed to be a kinetic barrier rather than a phase boundary. These findings lead to a new interpretation of the high P-T phase diagram of carbon dioxide. Furthermore, our approach opens a new way to perform quantitative in situ Raman measurements under extremely high pressures and temperatures, providing unique information about phase relations and structural and thermodynamic properties of materials under these conditions. PMID:15281882

Santoro, Mario; Lin, Jung-fu; Mao, Ho-kwang; Hemley, Russell J

2004-08-01

56

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

NASA Astrophysics Data System (ADS)

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.

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

2012-10-01

57

The Detection of Biosignatures by Laser Raman Spectroscopy for Mars Exploration  

NASA Astrophysics Data System (ADS)

Laser Raman spectra of potential biosignature molecules on Mars possess strong bands to distinguish them from each other and from minerals. Tests of the detection limits demonstrated satisfaction of the requirements posted by Mars2020 STD report.

Wei, J.; Wang, A.; Lu, Y.; Connor, K.; Bradley, A.; Marshall, C.; Steele, A.

2014-06-01

58

Raman Spectroscopy of Cocrystals  

NASA Astrophysics Data System (ADS)

Cocrystals are a class of compounds that consist of two or more molecules that are held together by hydrogen bonding. Pharmaceutical cocrystals are those that contain an active pharmaceutical ingredient (API) as one of the components. Pharmaceutical cocrystals are of particular interest and have gained a lot of attention in recent years because they offer the ability to modify the physical properties of the API, like solubility and bioavailability, without altering the chemical structure of the API. The APIs that we targeted for our studies are theophylline (Tp) and indomethacin (Ind). These compounds have been mixed with complementary coformers (cocrystal former) that include acetamide (AcONH2), melamine (MLM), nicotinic acid (Nic-COOH), 4-cyanopyridine (4-CNPy) and 4-aminopyridine (4-NH2Py). Raman spectroscopy has been used to characterize these cocrystals. Spectra of the cocrystals were compared to those of the coformers to analyze for peak shifts, specifically those corresponding to hydrogen bonding. A 0.5 m CCD Spex spectrometer was used, in a micro-Raman setup, for spectral analysis. An Argon ion Coherent laser at 514.5 nm was used as the excitation source. )

Rooney, Frank; Reardon, Paul; Ochoa, Romulo; Abourahma, Heba; Marti, Marcus; Dimeo, Rachel

2010-02-01

59

Nonlinear and Multiorder Raman Spectroscopy  

NASA Astrophysics Data System (ADS)

Two nonlinear forms of Raman spectroscopy are studied in liquids. The first, stimulated Raman scattering (SRS), dramatically increases the intensity of the Raman scattered radiation. Micrometer-size droplets, which possess morphology-dependent resonances and thus act as optical cavities, substantially lower the incident laser intensity necessary to achieve SRS. Because droplets enhance the SRS signal, SRS may prove to be a useful diagnostic spectroscopy for determining chemical species and their relative concentration present in small droplets. Some of the advantages and disadvantages of this technique are discussed. Particularly, the effect of changing the relative index of refraction of a droplet with respect to its surroundings, and the effect of changing the droplet size, on the efficiency of the resonance and the density of modes are calculated. The second form of Raman spectroscopy studied is hyper-Raman scattering, which can provide complementary information to that obtained with other optical spectroscopies, particularly conventional Raman and IR. Hyper-Raman scattering allows the observation of silent vibrational modes, i.e., those not observable with conventional optical spectroscopies, which is particularly important in liquids and solids where intermolecular interaction effect the energy levels. Silent modes are observed in the Stokes and anti-Stokes hyper -Raman spectra of deuterated benzene and in the Stokes hyper -Raman spectra of benzene. The intensity ratio between the anti-Stokes and Stokes peaks in the hyper-Raman spectra of carbon tetrachloride is found to have an intensity dependence which is explained by the concomitant SRS process. Hyper -Rayleigh scattering, the elastic scattering analog to hyper -Raman scattering, is observed for bulk liquids and micrometer -size droplets. The droplet spectra are noted to consist of a series of sharp peaks corresponding to MDR's. Because micrometer-size droplets enhance a number of nonlinear optical effects, and the hyper-Rayleigh spectra exhibited MDR's, third-order optical sum frequency generation was studied in droplets. When a carbon tetrachloride droplet is illuminated by an IR laser, a series of 28 discrete emission peaks is observed in the visible spectral region. These peaks are the result of four-wave mixing of the input radiation and the multiorder SRS radiation in the droplet. The detected third-harmonic intensity from a single droplet is several orders of magnitude larger than that from an optical cell containing the same liquid.

Acker, William Philip

60

Dual-wavelength y-branch distributed bragg reflector diode laser at 785 nanometers for shifted excitation Raman difference spectroscopy.  

PubMed

A dual-wavelength Y-branch distributed Bragg reflector (DBR) diode laser at 785 nm is presented as an excitation light source for shifted excitation Raman difference spectroscopy (SERDS). The monolithic device was realized with deeply etched surface DBR gratings using one-step epitaxy. An optical output power of 140 mW was obtained in continuous-wave (CW) operation for each laser cavity, with emission wavelengths of the device at 784.50 and 785.12 nm. A spectral width of the laser emission of 30 pm (0.5 cm(-1)), including 95% of optical power, was measured. The mean spectral distance of both excitation lines is 0.63 nm (10.2 cm(-1)) over the whole operating range. Raman experiments using polystyrene as the test sample and ambient light as the interference source were carried out and demonstrate the suitability of the dual-wavelength diode laser for SERDS. PMID:25061785

Maiwald, Martin; Eppich, Bernd; Fricke, Jörg; Ginolas, Arnim; Bugge, Frank; Sumpf, Bernd; Erbert, Götz; Tränkle, Günther

2014-08-01

61

In situ laser raman spectroscopy during sequential oxidizing and reducing conditions for a vanadium-phosphorous-oxide catalyst  

SciTech Connect

A VPO catalyst prepared in an organic medium has been studied by in situ laser Raman spectroscopy under reaction conditions for n-butane oxidation to maleic anhydride. Data were obtainable at low laser power and short collection times. Raman characterization during continuous flow (steady state) revealed that the (VO){sub 2}P{sub 2}O{sub 7} phase was present. Sequential oxidizing (10% O{sub 2} in N{sub 2}) and reducing (2% n-butane in N{sub 2}) conditions were explored at 350{degree} and 400{degree}C. Cycling (unsteady state) revealed enhancement of {alpha}{sub II}-VOPO{sub 4}, {beta}-VOPO{sub 4}, {gamma}-VOPO{sub 4}, and {delta}-VOPO{sub 4} during oxidizing conditions; intensity of Raman bands due to (VO){sub 2}P{sub 2}O{sub 7} increased during reducing conditions.

Soejarto, A.D.; Schrader, G.L. [Iowa State Univ. of Science and Technology, Ames, IA (United States); Coulston, G.W. [Du Pont de Nemours (E.I.) and Co., Wilmington, DE (United States). Central Research and Development Dept.

1995-12-31

62

First experimental study of self-forming synthetic lipids by confocal laser tweezers Raman spectroscopy  

Microsoft Academic Search

We present the first experimental study of self-forming synthetic lipids, trademarked as QuSomesTM, using Raman spectroscopy in the spectral range of 500 to 3100 cm-1. Raman spectra of these new artificial lipids composed of 1,2- dimyristoyl-rac-glycerol-3-dodecaethylene glycol (GDM-12) and 1,2-dioleoyl-rac-glycerol-3-dodecaethylene glycol (GDO-12) have been obtained in pure form and in aqueous suspensions with Phosphate Buffered Saline (PBS) by using an

Rajan K. Bista; Reinhard F. Bruch

2008-01-01

63

Assessment of argon ion laser dispersive Raman spectroscopy for hot cell applications  

SciTech Connect

Characterization of high-level waste tank materials at Hanford is conducted to support safety assessments and waste treatment activities. Raman spectroscopy is expected to give chemical species information which may assist in defining layering in tank waste. This report describes the dispersive Raman system used in this year`s investigation and the methology used to collect and evaluate data taken on tank waste samples. The current argon-ion Raman system was found not to be suitable for screening of tank cores, owing to silica interference, fluorescence interferences, and the extensive time required to collect and treat the data. Recommendations are given for further development.

Crawford, B.A.

1995-02-24

64

Tunable sideband laser from cascaded four-wave mixing in thin glass for ultra-broadband femtosecond stimulated Raman spectroscopy  

NASA Astrophysics Data System (ADS)

We demonstrate the generation of broadband up-converted multicolor array (BUMA) in a thin BK7 glass slide using two noncollinear weak near-IR laser pulses with various crossing angles. The BUMA signal arises from cubic nonlinear ?(3):?(3) processes via cascaded four-wave mixing of the two incident beams. Broad and continuous tunability of BUMA is simply achieved by varying the time delay between the two pulses. We implement one of the BUMA sidebands as the probe pulse for femtosecond stimulated Raman spectroscopy and collect a solvent mixture anti-Stokes Raman spectrum with an ultrabroad detection range of ca. 100-4000 cm-1.

Zhu, Liangdong; Liu, Weimin; Fang, Chong

2013-08-01

65

Laser Raman Spectra of Transition Metal Oxides and Catalysts  

Microsoft Academic Search

During recent years the study of the vibrational structure of catalysts by laser Raman spectroscopy (LRS) and of the interfacial properties of adsorbed species on solid surfaces by resonance Raman spectroscopy (RRS) and surface-enhanced Raman spectroscopy (SERS) have comprised one of the major research activities in the area of Raman spectroscopy [1–10] as applied to catalysts [11, 12].

Lalji Dixit; D. L. Gerrard; H. J. Bowley

1986-01-01

66

Raman spectroscopy in nanopolyacetylene  

NASA Astrophysics Data System (ADS)

The evolution of off-resonant and resonant Raman scattering spectra of cis and trans nanopolyacetylene (NPA) with change of frequency and intensity of incident laser light was studied. It was found that laser irradiation with wavelength 514.5 nm in process of Raman scattering spectra recording is accompanied by effective cis trans isomerization of approximately 50% cis - 50% trans NPA-PVB blend. The results obtained allow assuming that NPA in the initial compositions is a mixture of two types of nanoparticles.

Kobryanskii, Valerii M.; Paraschuk, Dmitri Y.; Shchegolikhin, Aleksandr N.; Kuptsov, Albert N.; Melnik, Nikolay N.

2000-09-01

67

Laser Raman micro-spectroscopy of Neoproterozoic - Early Palaeozoic organic-walled palynomorphs: palaeobiological interpretation  

NASA Astrophysics Data System (ADS)

Proterozoic and Palaeozoic organic walled microfossils (palynomorphs) comprise a wide range of organisms (e.g., oceanic photosynthetic microplankton, microzooplankton, and microscopic spores from earliest land plants), which characterize important evolutionary events in Earth's biosphere. For example, the evolutionary patterns and abundance fluctuations of acritarchs in the sedimentary records have been put in relation with changes in ocean chemistry, global glaciations, the diversification of metazoans, and variations in atmospheric CO2 concentration. Palynomorphs also record the transition of life from water (freshwater algae) to land (earliest miospores). Classical morphological comparative analytical methods are limited to those cases in which direct comparisons with extant organisms are available, but in many instances the biological affinities of pre-Devonian palynomorphs remain unknown. Recently, new techniques based on microchemical analysis of individual organic-walled microfossils demonstrated their potential for elucidating the cellular anatomy, composition, and mode of preservation of microfossils, thus offering new insights into their palaeobiology. In this study Laser Raman micro-spectroscopy was applied to a range of exceptionally well-preserved palynomorphs of late Neoproterozoic to early Devonian age, in order to better characterize their chemical composition. Raman spectra were successfully obtained from the studied palynomorphs; all showed characteristic bands attributable to C=C stretching for polycyclic aromatic compounds and contributions from CH2/CH3 bending. As in previously published MicroRaman spectra of organic-walled microfossils of varying age and state of preservation, the spectra reported here are characterized by two main lines at ~1350 and ~1600 cm-1 given by the so-called "D" (disordered) and "G" (graphitic) bands. These spectral features can be attributed to molecular subunits of interlinked aromatic hydrocarbons. It is important of notice that the position and shape of bands can vary between the species within the same sample, showing variability in the exact chemical composition depending on the species studied. For instance, the position of the main peak in the "D" region is placed at 1354 cm-1 in Navifusa majensis and Leiosphaeridia sp., whereas in Valeria lophostriata it is placed at 1375 cm-1. Similarly, the wavenumber of the "G" band is different, being 1600 cm-1 for the first two species and at 1577 cm-1 for Valeria lophostriata. Since these differences are taxon specific we suggest that they relate to the initial chemical and physical differences between the newly synthesised acritarch walls. The differences observed may be the preserved differences in chemistry of the biomacromolecules that comprised the original (not diagenetically modified) acritarch walls. Alternatively, the observed differences may only reflect result from differences between the original wall biomacromolecules, but no longer incorporate them since they have been entirely modified into geomacromolecules over time.

Vecoli, Marco; Dhamelincourt, Marie Claire; Mezzetti, Alberto; Cesari, Christian; Versteegh, Gerard

2010-05-01

68

Hollow Cathode Ion Lasers for Deep Ultraviolet Raman Spectroscopy and Fluorescence Imaging  

Microsoft Academic Search

This article describes the development of hollow cathode ion lasers and thelr use in constructmg an ultraviolet micro-Raman spectrograph with native fluorescence imaging capability. Any one of three excitation wavelengths can be chosen within seconds using flip mirrors and a dichroic mirror slide. Excitation at 224.3 nm is provided by a helium sllver (HeAg) hollow cathode metal ion laser, at

G. D. McDonald; A. I. Tsapin; K. H. Nealson

2001-01-01

69

Investigation on Mars model minerals by in situ laser Raman spectroscopy  

Microsoft Academic Search

For a fundamental understanding of the origin and evolution of planets detailed information on the surface material is required. Identifying structural fossils or chemical traces of extinct or extant life alongside with in depth mineral characterization of the site can be accomplished with Raman spectroscopy. Some beneficial features of this technique are summarized here. The current progress in the development

J. Popp; N. Tarcea; W. Kiefer; M. Hilchenbach; N. Thomas; S. Hofer; T. Stuffler

2001-01-01

70

Stand-off UV Laser Induced Fluorescence and UV Enhanced Raman Spectroscopy for Mineral Analysis  

NASA Astrophysics Data System (ADS)

INO has developed a stand-off Laser Induced Fluorescence and Raman sensor and has measured mineral spectra from a distance of 10 meters. Identification is possible using a 355 nm excitation and analyzing the returned signal in the 390 to 640 nm range.

Babin, F.; Hô, N.; Paradis, P.-F.; Deblois, S.; Châteauneuf, F.

2011-03-01

71

In vivo Molecular Evaluation of Guinea Pig Skin Incisions Healing after Surgical Suture and Laser Tissue Welding Using Raman Spectroscopy  

PubMed Central

The healing process in guinea pig skin following surgical incisions was evaluated at the molecular level, in vivo, by the use of Raman spectroscopy. After the incisions were closed either by suturing or by laser tissue welding (LTW), differences in the respective Raman spectra were identified. The study determined that the ratio of the Raman peaks of the amide III (1247 cm?1) band to a peak at 1326 cm?1 (the superposition of elastin and keratin bands) can be used to evaluate the progression of wound healing. Conformational changes in the amide I band (1633 cm?1 to 1682 cm?1) and spectrum changes in the range of 1450 cm?1 to 1520 cm?1 were observed in LTW and sutured skin. The stages of the healing process of the guinea pig skin following LTW and suturing were evaluated by Raman spectroscopy, using histopathology as the gold standard. LTW skin demonstrated better healing than sutured skin, exhibiting minimal hyperkeratosis, minimal collagen deposition, near-normal surface contour, and minimal loss of dermal appendages. A wavelet decomposition-reconstruction baseline correction algorithm was employed to remove the fluorescence wing from the Raman spectra.

Alimova, A.; Chakraverty, R.; Muthukattil, R.; Elder, S.; Katz, A.; Sriramoju, V.; Lipper, Stanley; Alfano, R. R.

2009-01-01

72

Raman spectroscopy of piezoelectrics  

NASA Astrophysics Data System (ADS)

Raman spectroscopy represents an insightful characterization tool in electronics, which comprehensively suits the technological needs for locally and quantitatively assessing crystal structures, domain textures, crystallographic misalignments, and residual stresses in piezoelectric materials and related devices. Recent improvements in data processing and instrumental screening of large sampling areas have provided Raman spectroscopic evaluations with rejuvenating effectiveness and presently give spin to increasingly wider and more sophisticated experimental explorations. However, the physics underlying the Raman effect represents an issue of deep complexity and its applicative development to non-cubic crystallographic structures can yet be considered in its infancy. This review paper revisits some applicative aspects of the physics governing Raman emission from crystalline matter, exploring the possibility of disentangling the convoluted dependences of the Raman spectrum on crystal orientation and mechanical stress. Attention is paid to the technologically important class of piezoelectric materials, for which working algorithms are explicitly worked out in order to quantitatively extract both structural and mechanical information from polarized Raman spectra. Systematic characterizations of piezoelectric materials and devices are successively presented as applications of the developed equations. The Raman response of complex crystal structures, described here according to a unified formalism, is interpreted as a means for assessing both crystallographic textures and stress-related issues in the three-dimensional space (thus preserving their vectorial and tensorial nature, respectively). Statistical descriptions of domain textures based on orientation distribution functions are also developed in order to provide a link between intrinsic single-crystal data and data collected on polycrystalline (partly textured) structures. This paper aims at providing rigorous spectroscopic foundations to Raman approaches dealing with the analyses of functional behavior and structural reliability of piezoelectric devices.

Pezzotti, Giuseppe

2013-06-01

73

A time-resolved 128x128 SPAD camera for laser Raman spectroscopy  

NASA Astrophysics Data System (ADS)

In this paper we present a time-gated single-photon avalanche diode (SPAD) array, the first of its kind to be integrated with a newly developed time-resolved laser Raman spectrometer. Time-resolved Raman spectra from various highly fluorescent minerals were successfully observed using our SPAD array; these spectra were obscured by an overwhelming fluorescence background when measured using a traditional continuous wave green laser. The system has photon detection efficiency (PDE) of 5 % at 5 V excess bias with on-chip microlenses. The dark count rate (DCR) of this SPAD is 1.8 kHz at 5 V excess bias. However, thanks to the nanosecond scale time-gating, noise rate per frame is effectively reduced to ~10-3 counts at 40 kHz laser repetition rate.

Maruyama, Yuki; Blacksberg, Jordana; Charbon, Edoardo

2012-05-01

74

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

NASA Astrophysics Data System (ADS)

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.

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

75

Crystalline Raman Lasers  

Microsoft Academic Search

In this paper, we review the developments of crystalline Raman lasers over the past five years. Average powers exceeding 5 W and pulse energies above 1 J in the near infrared have been demonstrated for larger scale devices. There has been a rapid development of all-solid-state sources based on the standard diode-pumped lasers, especially intracavity crystalline Raman lasers, which offer

James A. Piper; Helen M. Pask

2007-01-01

76

Ultrashort high repetition rate exposure of dielectric materials: laser bonding of glasses analyzed by micro-Raman spectroscopy  

NASA Astrophysics Data System (ADS)

We report on the joining of different glass types with dissimilar optical, thermal and mechanical properties by ultrashort laser welding at high repetition rates. Femtosecond laser pulses were focused at the interface of two optically contacted transparent samples. Using nonlinear absorption processes and heat accumulation of successive pulses, we achieved strong bonds between the samples. We used a three-point bending test to determine the breaking strength. With this technique, we achieved for instance for a borosilicate glass a breaking strength of up to 95 % of the bulk material. In addition, we even welded different material combinations. Although the welded glasses exhibit different thermal and mechanical properties, we obtained breaking strengths which are comparable to the utilized bulk materials. Using Raman spectroscopy we mapped the laser-processed material along the welded interface. Thereby, we determined that the welds consist of a mixture of both species, which is formed during the laser induced melting of the materials.

Richter, S.; Zimmermann, F.; Döring, S.; Tünnermann, A.; Nolte, S.

2013-01-01

77

Laser irradiation effects on the CdTe/ZnTe quantum dot structure studied by Raman and AFM spectroscopy  

NASA Astrophysics Data System (ADS)

Micro-Raman spectroscopy has been applied to investigate the impact of laser irradiation on semiconducting CdTe/ZnTe quantum dots (QDs) structures. A reference sample (without dots) was also studied for comparison. Both samples were grown by molecular beam epitaxy technique on the p-type GaAs substrate. The Raman spectra have been recorded for different time of a laser exposure and for various laser powers. The spectra for both samples exhibit peak related to the localized longitudinal (LO) ZnTe phonon of a wavenumber equal to 210 cm-1. For the QD sample, a broad band corresponding to the LO CdTe phonon related to the QD-layer appears at a wavenumber of 160 cm-1. With increasing time of a laser beam exposure and laser power, the spectra get dominated by tellurium--related peaks appearing at wavenumbers around 120 cm-1 and 140 cm-1. Simultaneously, the ZnTe surface undergoes rising damage, with the formation of Te aggregates at the pinhole edge as reveal atomic force microscopy observations. Local temperature of irradiated region has been estimated from the anti-Stokes/Stokes ratio of the Te modes intensity and it was found to be close or exceeding ZnTe melting point. Thus, the laser damage can be explained by the ablation process.

Zielony, E.; P?aczek-Popko, E.; Henrykowski, A.; Gumienny, Z.; Kamyczek, P.; Jacak, J.; Nowakowski, P.; Karczewski, G.

2012-09-01

78

Laser irradiation effects on the CdTe/ZnTe quantum dot structure studied by Raman and AFM spectroscopy  

SciTech Connect

Micro-Raman spectroscopy has been applied to investigate the impact of laser irradiation on semiconducting CdTe/ZnTe quantum dots (QDs) structures. A reference sample (without dots) was also studied for comparison. Both samples were grown by molecular beam epitaxy technique on the p-type GaAs substrate. The Raman spectra have been recorded for different time of a laser exposure and for various laser powers. The spectra for both samples exhibit peak related to the localized longitudinal (LO) ZnTe phonon of a wavenumber equal to 210 cm{sup -1}. For the QD sample, a broad band corresponding to the LO CdTe phonon related to the QD-layer appears at a wavenumber of 160 cm{sup -1}. With increasing time of a laser beam exposure and laser power, the spectra get dominated by tellurium-related peaks appearing at wavenumbers around 120 cm{sup -1} and 140 cm{sup -1}. Simultaneously, the ZnTe surface undergoes rising damage, with the formation of Te aggregates at the pinhole edge as reveal atomic force microscopy observations. Local temperature of irradiated region has been estimated from the anti-Stokes/Stokes ratio of the Te modes intensity and it was found to be close or exceeding ZnTe melting point. Thus, the laser damage can be explained by the ablation process.

Zielony, E.; Placzek-Popko, E.; Henrykowski, A.; Gumienny, Z.; Kamyczek, P.; Jacak, J. [Institute of Physics, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland); Nowakowski, P.; Karczewski, G. [Institute of Physics, Polish Academy of Sciences, al. Lotnikow 32/46, 02-668 Warsaw (Poland)

2012-09-15

79

Liquid-Core Waveguide for Enhanced Laser Raman Spectroscopy in Oceanic Applications  

Microsoft Academic Search

Over the past five years, the Brewer Lab Group at MBARI has effectively used DORISS (Deep Ocean Raman In Situ Spectrometer) for oceanic chemistry studies. Laser power limitations have thus far constrained the sensitivity of the system, preventing the observation of the natural trace concentrations of bicarbonate in seawater (2 mmol\\/kg), a crucial indicator of the CO2\\/Carbonic Acid\\/Bicarbonate\\/Carbonate balance in

Jonathan Scholl; Peter Brewer; Edward Peltzer; Peter Walz

2006-01-01

80

Portable Raman spectroscopy using retina-safe (1550 nm) laser excitation  

NASA Astrophysics Data System (ADS)

The use of portable Raman analyzers to identify unknown substances in the field has grown dramatically during the past decade. Measurements often require the laser beam to exit the confines of the sample compartment, which increases the potential of eye or skin damage. This is especially true for most commercial analyzers, which use 785 nm laser excitation. To overcome this safety concern, we have built a portable FT-Raman analyzer using a 1550 nm retina-safe excitation laser. Excitation at 1550 nm falls within the 1400 to 2000 nm retina-safe range, so called because the least amount of damage to the eye occurs in this spectral region. In contrast to wavelengths below 1400 nm, the retina-safe wavelengths are not focused by the eye, but are absorbed by the cornea, aqueous and vitreous humor. Here we compare the performance of this system to measurements of explosives at shorter wavelengths, as well as its ability to measure surface-enhanced Raman spectra of several chemicals, including the food contaminant melamine.

Brouillette, Carl; Smith, Wayne; Donahue, Michael; Huang, Hermes; Shende, Chetan; Sengupta, Atanu; Inscore, Frank; Patient, Michael; Farquharson, Stuart

2012-05-01

81

Theoretical analysis of anharmonic coupling and cascading Raman signals observed with femtosecond stimulated Raman spectroscopy  

Microsoft Academic Search

We present a classical theoretical treatment of a two-dimensional Raman spectroscopy based on the initiation of vibrational coherence with an impulsive Raman pump and subsequent probing by two-pulse femtosecond stimulated Raman spectroscopy (FSRS). The classical model offers an intuitive picture of the molecular dynamics initiated by each laser pulse and the generation of the signal field traveling along the probe

Randy D. Mehlenbacher; Brendon Lyons; Kristina C. Wilson; Yong Du; David W. McCamant

2009-01-01

82

Raman spectroscopy of oral bacteria  

NASA Astrophysics Data System (ADS)

Raman spectroscopy has been employed to measure the varying concentrations of two oral bacteria in simple mixtures. Evaporated droplets of centrifuged mixtures of Streptococcus sanguis and Streptococcus mutans were analyzed via Raman microspectroscopy. The concentration of s. sanguis was determined based upon the measured Raman spectrum, using partial least squares cross-validation, with an r2 value of 0.98.

Berger, Andrew J.; Zhu, Qingyuan; Quivey, Robert G.

2003-10-01

83

Femtosecond Broadband Stimulated Raman Spectroscopy  

Microsoft Academic Search

Femtosecond broadband stimulated Raman spectroscopy (FSRS) is a new technique where a narrow bandwidth picosecond Raman pump pulse and a red-shifted broadband femtosecond Stokes probe pulse (with or without time delay between the pulses) act on a sample to produce a high resolution Raman gain spectrum with high efficiency and speed, free from fluorescence background interference. It can reveal vibrational

Soo-Y. Lee; Sangwoon Yoon; Richard A. Mathies

2006-01-01

84

Raman spectroscopy of natural oxalates  

Microsoft Academic Search

Evidence for the existence of primitive life forms such as lichens and fungi can be based upon the formation of oxalates which are most readily detected using Raman spectroscopy. A comparative study of a suite of natural oxalates including weddellite, whewellite, moolooite, humboldtine, glushinskite, natroxalate and oxammite has been undertaken using Raman spectroscopy. The minerals are characterised by the wavenumber

R. L Frost

2004-01-01

85

Optoacoustic Raman gain spectroscopy of liquids  

Microsoft Academic Search

We report the first optoacoustic Raman gain spectroscopy (OARS) of liquids, using two synchronized pulsed dye lasers, and gated optoacoustic detection of the energy deposited in the liquid due to the stimulated Raman (Stokes) scattering. We demonstrate this sensitive technique with several neat liquids, including benzene, acetone, 1,1,1-trichloroethane, toluene, and n-hexane. This technique seems competitive or superior to other techniques

C. K. N. Patel; A. C. Tam

1979-01-01

86

Ozone Decomposition over Manganese Oxide Supported on ZrO 2 and TiO 2: A Kinetic Study Using in Situ Laser Raman Spectroscopy  

Microsoft Academic Search

Ozone decomposition on ZrO2- and TiO2-supported manganese oxide was studied using in situ laser Raman spectroscopy along with simultaneous steady-state kinetic measurements. The Raman spectra showed the presence of an adsorbed peroxide species for both catalysts under reaction conditions. The experimental data were well represented by a nonuniform surface kinetic treatment that assumed that the activation energies of adsorption and

Rakesh Radhakrishnan; S. Ted Oyama

2001-01-01

87

Micro-Raman spectroscopy of refractive index microstructures in silicone-based hydrogel polymers created by high-repetition-rate femtosecond laser micromachining  

Microsoft Academic Search

Micro-Raman spectroscopy was used to study silicone-based hydrogel polymers after being modified by 800 nm, 27 fs laser pulses from a Ti:sapphire oscillator at 93 MHz repetition rate. When the irradiation con- ditions were below the optical breakdown threshold of the polymers, no significant changes in the Raman spec- tra and background fluorescence were observed even when refractive index changes

Li Ding; Luiz Gustavo Cancado; Lukas Novotny; Wayne H. Knox; Neil Anderson; Dharmendra Jani; Jeffrey Linhardt; Richard I. Blackwell; Jay F. Künzler

2009-01-01

88

Femtosecond coherent Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Femtosecond time-resolved CARS spectroscopy is applied in order to prepare and monitor coherent states of different samples mainly in its electronic ground but also excited states. The time evolution prepared by such methods give information on the dynamics of molecular vibrations. In a first example, the fs CARS transients of iodine are investigated. Depending on the timing of the laser pulses different dynamics are reflected in the transient CARS signal. Second, we report on selective excitation of the vibrational modes in the electronic ground state of polymers of diacetylene by means of a femtosecond time-resolved CARS scheme. Control is achieved by varying the timing and the phase shape of the exciting laser pulses. Finally the electronic ground state dynamics of biologically relevant porphyrine molecules are studied with transient CARS spectroscopy.

Kiefer, Wolfgang; Chen, T.; Heid, M.; Materny, A.; Schmitt, M.; Siebert, T.; Vierheilig, A.

2002-05-01

89

Investigation of synergy effects in selective oxidation catalysts through in situ laser Raman spectroscopy/isotopic labeling technique  

SciTech Connect

Previous studies over two-phase catalysts consisting of a simple molybdate (MnMoO{sub 4}, CdMoO{sub 4}) in close contact with molybdenum oxide (MoO{sub 3}) have shown the existence of a strong synergy effect in partial oxidation of C{sub 4} hydrocarbons to maleic anhydride. In this paper, the authors present results of the investigation of this synergy effect using an isotopic labeling technique coupled with in situ laser Raman spectroscopy. Results from these studies, when integrated with their previous work, provide complementary evidence for the catalytic job distribution of the two phases, in which the MoO{sub 3} phase incorporates its lattice oxygen into the hydrocarbon molecule, while the simple molybdate phase provides the oxygen necessary to regenerate MoO{sub 3} sites through an oxygen spillover mechanism. The in situ Raman spectroscopy experiments combined with structural specificity studies provide further clues about the catalytic sites responsible for selective versus complete oxidation.

Ozkan, U.S.; Smith, M.R.; Driscoll, S.A. (Ohio State Univ., Columbus (United States))

1992-03-01

90

Fourier transform Raman spectroscopy  

SciTech Connect

Bruce Chase of E.I. du Pont de Nemours and Co. describes the logical thought process that led to the design of an FT-Raman spectrometer. FT-Raman spectrometers are found to provide better fluorescence rejection and high-frequency precision than conventional Raman instruments.

Chase, B.

1987-07-15

91

NIR Raman spectroscopy in medicine and biology: results and aspects  

Microsoft Academic Search

Analyses of biomaterial by ‘classical’ Raman spectroscopy with excitation in the visible range has not been possible since the fluorescence of many essential constituents of all animal and plant cells and tissues overlays the Raman spectra completely. Fluorescence, however, is virtually avoided, when Raman spectra are excited with the Nd:YAG laser line at 1064nm. Within seven dissertations we explored different

B. Schrader; B Dippel; I Erb; S Keller; T Löchte; H Schulz; E Tatsch; S Wessel

1999-01-01

92

Stress measurement in alumina scales on high temperature alloys using X-ray stress evaluation and laser Raman spectroscopy.  

PubMed

The effect of silicon and titanium on the spallation resistance of alumina scales grown on NiCrAlY-type alloys has been investigated using model alloys with different additions of Si or Ti. For this purpose cyclic oxidation experiments have been carried out at temperatures between 950 and 1100 degrees C. After various times stresses in selected Si-doped samples have been determined by X-ray stress evaluation (XSE) at ambient temperature. The compressive stresses in the scales have been found to increase with an increasing oxidation time tending to become constant for long times. The development of stress is affected by the presence of Si. Laser Raman spectroscopy (LRS) has been calibrated for strain measurement using XSE results. Then LRS has been applied for strain measurement at higher temperatures. PMID:15045361

Vosberg, V R; Fischer, W; Berger, M G; Clemens, D; Quadakkers, W J; Nickel, H

1996-06-01

93

Metal Surface Raman Spectroscopy: Theory.  

National Technical Information Service (NTIS)

Studies of the Raman and infrared spectra of several molecules adsorbed to metal surfaces indicate that special selection rules govern these spectra. In the case of infrared reflection adsorption spectroscopy (IRS) as in the related techniques of electron...

R. M. Hexter M. G. Albrecht

1978-01-01

94

Laser Raman Tweezer Spectroscopy for the Molecular and Functional Characterization of Single Live Mouse Mammary Tumor-Initiating Cells.  

National Technical Information Service (NTIS)

The purpose of this research is to utilize Raman Spectroscopy (RS) combined with optical tweezer technology (RTS) to isolate and characterize the intracellular molecular profiles of live tumor initiating cells derived from p53 null mouse mammary tumors. T...

F. Behbod

2012-01-01

95

Communication: two-dimensional gas-phase coherent anti-Stokes Raman spectroscopy (2D-CARS): simultaneous planar imaging and multiplex spectroscopy in a single laser shot.  

PubMed

Coherent anti-Stokes Raman spectroscopy (CARS) has been widely used as a powerful tool for chemical sensing, molecular dynamics measurements, and rovibrational spectroscopy since its development over 30 years ago, finding use in fields of study as diverse as combustion diagnostics, cell biology, plasma physics, and the standoff detection of explosives. The capability for acquiring resolved CARS spectra in multiple spatial dimensions within a single laser shot has been a long-standing goal for the study of dynamical processes, but has proven elusive because of both phase-matching and detection considerations. Here, by combining new phase matching and detection schemes with the high efficiency of femtosecond excitation of Raman coherences, we introduce a technique for single-shot two-dimensional (2D) spatial measurements of gas phase CARS spectra. We demonstrate a spectrometer enabling both 2D plane imaging and spectroscopy simultaneously, and present the instantaneous measurement of 15,000 spatially correlated rotational CARS spectra in N2 and air over a 2D field of 40 mm(2). PMID:23781772

Bohlin, Alexis; Kliewer, Christopher J

2013-06-14

96

Communication: Two-dimensional gas-phase coherent anti-Stokes Raman spectroscopy (2D-CARS): Simultaneous planar imaging and multiplex spectroscopy in a single laser shot  

NASA Astrophysics Data System (ADS)

Coherent anti-Stokes Raman spectroscopy (CARS) has been widely used as a powerful tool for chemical sensing, molecular dynamics measurements, and rovibrational spectroscopy since its development over 30 years ago, finding use in fields of study as diverse as combustion diagnostics, cell biology, plasma physics, and the standoff detection of explosives. The capability for acquiring resolved CARS spectra in multiple spatial dimensions within a single laser shot has been a long-standing goal for the study of dynamical processes, but has proven elusive because of both phase-matching and detection considerations. Here, by combining new phase matching and detection schemes with the high efficiency of femtosecond excitation of Raman coherences, we introduce a technique for single-shot two-dimensional (2D) spatial measurements of gas phase CARS spectra. We demonstrate a spectrometer enabling both 2D plane imaging and spectroscopy simultaneously, and present the instantaneous measurement of 15 000 spatially correlated rotational CARS spectra in N2 and air over a 2D field of 40 mm2.

Bohlin, Alexis; Kliewer, Christopher J.

2013-06-01

97

Resonance Raman spectroscopy.  

PubMed

Flavin is a general name given to molecules having the heteroaromatic ring system of 7,8-dimethylisoalloxazine but practically means riboflavin (Rfl), flavin adenine dinucleotide (FAD), and flavin mononucleotide (FMN) in biological systems, whose structures are illustrated in Fig. 1, together with the atomic numbering scheme and ring numbering of the isoalloxazine moiety. As the isoalloxazine skeleton cannot be synthesized in human cells, it is obtained from diet as Rfl (vitamin B2). FAD and FMN can act as cofactors in flavoenzymes but Rfl does not. Most flavoenzymes catalyze redox reactions of substrates (Miura, Chem Rec 1:183-194, 2001). When O2 serves as the oxidant in the oxidation half cycle of an enzymic reaction, the enzyme is called "flavo-oxidase" but when others do, the enzyme is called "flavo-dehydrogenase." The difference between the two types of oxidative catalysis arises from delicate differences in the ?-electron distributions in the isoalloxazine ring, which can be revealed by Raman spectroscopy (Miura, Chem Rec 1:183-194, 2001). Since a flavin is an extremely versatile molecule, the scientific field including chemistry, biochemistry, and enzymology is collectively called "flavonology." It was found recently, however, that the flavin also acts as a chromophore to initiate light-induced DNA repair and signal transductions (Sancar, Chem Rev 103:2203-2237, 2003). PMID:24764099

Li, Jiang; Kitagawa, Teizo

2014-01-01

98

Laser irradiation and Raman spectroscopy of single living cells and chromosomes: Sample degradation occurs with 514.5 nm but not with 660 nm laser light  

Microsoft Academic Search

In Raman spectroscopic measurements of single cells (human lymphocytes) and chromosomes, using a newly developed confocal Raman microspectrometer and a laser excitation wavelength of 514.5 nm, degradation of the biological objects was observed. In the experiments high power microscope objectives were used, focusing the laser beam into a spot ? 0.5 ?m in diameter. At the position of the laser

G. J. Puppels; J. H. F. Olminkhof; G. M. J. Segers-Nolten; C. Otto; Mul de F. F. M; J. Greve

1991-01-01

99

Analysis of natural and artificial ultramarine blue pigments using laser induced breakdown and pulsed Raman spectroscopy, statistical analysis and light microscopy  

NASA Astrophysics Data System (ADS)

Pulsed laser induced breakdown spectroscopy (LIBS) and Raman spectroscopy were performed using a novel laboratory setup employing the same Nd:YAG laser emission at 532 nm for the analysis of five commercially available pigments collectively known as "ultramarine blue", a sodium silicate material of either mineral origin or an artificially produced glass. LIBS and Raman spectroscopy have provided information regarding the elemental and molecular composition of the samples; additionally, an analytical protocol for the differentiation between natural (lapis lazuli) and artificial ultramarine blue pigments is proposed. In particular LIBS analysis has allowed the discrimination between pigments on the basis of peaks ascribed to calcium. The presence of calcite in the natural blue pigments has been confirmed following Raman spectroscopy in specific areas of the samples, and micro-Raman and optical microscopy have further corroborated the presence of calcite inclusions in the samples of natural origin. Finally multivariate analysis of Laser induced breakdown spectra using principal component analysis (PCA) further enhanced the differentiation between natural and artificial ultramarine blue pigments.

Osticioli, I.; Mendes, N. F. C.; Nevin, A.; Gil, Francisco P. S. C.; Becucci, M.; Castellucci, E.

2009-08-01

100

Analysis of natural and artificial ultramarine blue pigments using laser induced breakdown and pulsed Raman spectroscopy, statistical analysis and light microscopy.  

PubMed

Pulsed laser induced breakdown spectroscopy (LIBS) and Raman spectroscopy were performed using a novel laboratory setup employing the same Nd:YAG laser emission at 532 nm for the analysis of five commercially available pigments collectively known as "ultramarine blue", a sodium silicate material of either mineral origin or an artificially produced glass. LIBS and Raman spectroscopy have provided information regarding the elemental and molecular composition of the samples; additionally, an analytical protocol for the differentiation between natural (lapis lazuli) and artificial ultramarine blue pigments is proposed. In particular LIBS analysis has allowed the discrimination between pigments on the basis of peaks ascribed to calcium. The presence of calcite in the natural blue pigments has been confirmed following Raman spectroscopy in specific areas of the samples, and micro-Raman and optical microscopy have further corroborated the presence of calcite inclusions in the samples of natural origin. Finally multivariate analysis of Laser induced breakdown spectra using principal component analysis (PCA) further enhanced the differentiation between natural and artificial ultramarine blue pigments. PMID:19129003

Osticioli, I; Mendes, N F C; Nevin, A; Gil, Francisco P S C; Becucci, M; Castellucci, E

2009-08-01

101

Blood analysis by Raman spectroscopy  

NASA Astrophysics Data System (ADS)

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 (r2 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.

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

2002-11-01

102

Femtosecond Broadband Stimulated Raman Spectroscopy  

NASA Astrophysics Data System (ADS)

Femtosecond broadband stimulated Raman spectroscopy (FSRS) is a new technique where a narrow bandwidth picosecond Raman pump pulse and a red-shifted broadband femtosecond Stokes probe pulse (with or without time delay between the pulses) act on a sample to produce a high resolution Raman gain spectrum with high efficiency and speed, free from fluorescence background interference. It can reveal vibrational structural information and dynamics of stationary or transient states. Here, the quantum picture for femtosecond broadband stimulated Raman spectroscopy (FSRS) is used to develop the semiclassical coupled wave theory of the phenomenon and to derive an expression for the measurable Raman gain in FSRS. The semiclassical theory is applied to study the dependence of lineshapes in FSRS on the pump-probe time delay and to deduce vibrational dephasing times in cyclohexane in the ground state.

Lee, Soo-Y.; Yoon, Sagwoon; Mathies, Richard A.

2006-01-01

103

Raman spectroscopy: the gateway into tomorrow's virology  

Microsoft Academic Search

In the molecular world, researchers act as detectives working hard to unravel the mysteries surrounding cells. One of the researchers' greatest tools in this endeavor has been Raman spectroscopy. Raman spectroscopy is a spectroscopic technique that measures the unique Raman spectra for every type of biological molecule. As such, Raman spectroscopy has the potential to provide scientists with a library

Phelps J Lambert; Audy G Whitman; Ossie F Dyson; Shaw M Akula

2006-01-01

104

Laser Raman probe diagnostics  

NASA Astrophysics Data System (ADS)

The overall objective of this work is to provide a scientific basis for a new non-perturbing, space and time resolved optical probe of gas temperature and constituency in combustion systems. The major part of the effort is focussed on the development of Raman scattering methods to accomplish this goal. Effort is also directed toward the goal of using other compatible measurement techniques (viz., laser velocimetry) in an integrated probe system for flame characterization.

Lapp, M.; Penney, C. M.; Warshaw, S.

1982-11-01

105

Measuring Rocket Engine Temperatures with Hydrogen Raman Spectroscopy  

NASA Technical Reports Server (NTRS)

Laser-based combustion diagnostics, such as single-pulse UV Raman spectroscopy and visible Raman spectroscopy, have been successfully applied to optically-accessible rocket-like test articles. If an independent pressure measurement is available, Raman major species concentration measurements can also provide a temperature measurement. However it is desirable to obtain a Raman-derived temperature measurement without the need for simultaneous pressure measurement, especially when chamber pressure may vary spatially. This report describes Raman temperature measurements obtained by exploiting the variation in shape of the H2 Raman spectrum. Hydrogen is advantageous since it is ubiquitous in H2-O2 systems and its Raman spectrum is simpler than for other diatomics. However the influence of high pressure on the H2 Raman spectrum must be investigated. At moderate pressures, well below those of rocket engines, the Raman spectra of O2 and N2 are known to become featureless due to collisional broadening.

Wehrmeyer, Joseph A.

2002-01-01

106

Liquid jet waveguide for Raman spectroscopy  

NASA Astrophysics Data System (ADS)

An optofluidic jet waveguide for Raman spectroscopy is reported. In this device a micro-channel is used to produce a high speed liquid stream acting at the same time, as the solution to analyse and as an optical waveguide. The liquid waveguide, exploiting total internal reflection, is able to effectively collect the Raman signal produced by the chemical compound under analysis opportunely excited by means of a laser source. Using a self-aligned configuration, the liquid jet is directly coupled with a multimode optical fiber collecting the Raman signal towards the detection system. The waveguiding nature of a liquid jet enables high Raman signal collection and the device configuration allows strong reduction of the background as no confining walls are used to contain the solution to analyse. The performances of the system have been successfully tested on isopropyl alcohol in water solutions showing a detection limit for this chemical compound of 0.8+/-0.1%.

Persichetti, Gianluca; Testa, Genni; Bernini, Romeo

2014-03-01

107

Characterization of Kevlar Using Raman Spectroscopy  

NASA Technical Reports Server (NTRS)

This paper explores the characterization of Kevlar composite materials using Raman spectroscopy. The goal of the research is to develop and understand the Raman spectrum of Kevlar materials to provide a foundation for the development of nondestructive evaluation (NDE) technologies based on the interaction of laser light with the polymer Kevlar. The paper discusses the fundamental aspects of experimental characterization of the spectrum of Kevlar, including the effects of incident wavelength, polarization and laser power. The effects of environmental exposure of Kevlar materials on certain characteristics of its Raman spectrum are explored, as well as the effects of applied stress. This data may provide a foundation for the development of NDE technologies intended to detect the in-situ deterioration of Kevlar materials used for engineering applications that can later be extended to other materials such as carbon fiber composites.

Washer, Glenn; Brooks, Thomas; Saulsberry, Regor

2007-01-01

108

Stimulated Raman Emission and Absorption Spectroscopy.  

National Technical Information Service (NTIS)

Eight reports (some published) on raman spectroscopy are included. The titles of the reports are as follows: Frequency broadening in liquids by a short light pulse; Angular distribution of surface radiation in stimulated raman scattering; Raman linewidths...

B. P. Stoicheff F. Shimizu A. K. McQuillan W. R. L. Clements U. Bachmann

1969-01-01

109

Raman spectroscopy of shocked water  

SciTech Connect

Raman scattering has been used extensively to study the vibrational and rotational properties of molecules under a variety of conditions. Here, interest is in the behavior of water molecules shocked to high pressures and temperatures. Behind the shock front the water molecules undergo changes in bonding and the molecules may become ionized. Raman spectroscopy can be used to determine the molecular species behind the shock front. In addition, changes in Raman spectra can yield information regarding inter- and intramolecular potentials and the temperature behind the shock front.

Holmes, N.C.; Mitchell, A.C.; Nellis, W.J.; Graham, W.B.; Walrafen, G.E.

1983-07-01

110

High fidelity nanohole enhanced Raman spectroscopy.  

SciTech Connect

Surface enhanced Raman spectroscopy (SERS) is a sensitive technique that can even detect single molecules. However, in many SERS applications, the strongly inhomogeneous distribution of intense local fields makes it very difficult for a quantitive assessment of the fidelity, or reproducibility of the signal, which limits the application of SERS. Herein, we report the development of exceptionally high-fidelity hole-enhanced Raman spectroscopy (HERS) from ordered, 2D hexagonal nanohole arrays. We take the fidelity f to be a measure of the percent deviation of the Raman peaks from measurement to measurement. Overall, area averaged fidelities for 12 gold array samples ranged from f {approx} 2-15% for HERS using aqueous R6G molecules. Furthermore, intensity modulations of the enhanced Raman spectra were measured for the first time as a function of polarization angle. The best of these measurements, which focus on static laser spots on the sample, could be consistent with even higher fidelities than the area-averaged results. Nanohole arrays in silver provided supporting polarization measurements and a more complete enhanced Raman fingerprint for phenylalanine molecules. We also carried out finite-difference time-domain calculations to assist in the interpretation of the experiments, identifying the polarization dependence as possibly arising from hole-hole interactions. Our results represent a step toward making quantitative and reproducible enhanced Raman measurements possible and also open new avenues for a large-scale source of highly uniform hot spots.

Bahns, J. T.; Guo, Q.; Gray, S. K.; Jaeger, H. M.; Chen, L.; Montgomery, J. M.; Univ. of Chicago

2009-01-01

111

Effect of pulsed laser irradiation on the structure of GeTe films deposited by metal organic chemical vapor deposition: A Raman spectroscopy study  

SciTech Connect

Phase changes between amorphous and crystallized states were induced by laser irradiation with nanosecond pulses in Ge{sub x}Te{sub y} films grown by metal organic chemical vapor deposition. The different phases were obtained by adjusting the pulse energy and could be distinguished by their different optical reflectivities. The corresponding structural changes were studied by Raman spectroscopy, showing marked differences for the two phases. A clear correlation is found between optical reflectivity levels, crystallographic state and the evolution of Ge-Ge, Te-Te, and Ge-Te Raman bands.

Salicio, O.; Wiemer, C.; Fanciulli, M. [CNR-INFM MDM Laboratory, via C. Olivetti 2, 20041 Agrate Brianza (Italy); Gawelda, W.; Siegel, J.; Afonso, C. N. [Laser Processing Group, Instituto de Optica, CSIC, Serrano 121, E-28006 Madrid (Spain); Plausinaitiene, V.; Abrutis, A. [Department of General and Inorganic Chemistry, Faculty of Chemistry, Vilnius University, Naugarduko 24, LT-2006 VU (Lithuania)

2009-02-01

112

Waterborne pathogen detection using Raman spectroscopy.  

PubMed

Raman spectroscopy is being evaluated as a candidate technology for waterborne pathogen detection. We have investigated the impact of key experimental and background interference parameters on the bacterial species level identification performance of Raman detection. These parameters include laser-induced photodamage threshold, composition of water matrix, and organism aging in water. The laser-induced photodamage may be minimized by operating a 532 nm continuous wave laser excitation at laser power densities below 2300 W/cm(2) for Grampositive Bacillus atrophaeus (formerly Bacillus globigii, BG) vegetative cells, 2800 W/cm(2) for BG spores, and 3500 W/cm(2) for Gram-negative E. coli (EC) organisms. In general, Bacillus spore microorganism preparations may be irradiated with higher laser power densities than the equivalent Bacillus vegetative preparations. In order to evaluate the impact of background interference and organism aging, we selected a biomaterials set comprising Gram-positive (anthrax simulants) organisms, Gram-negative (plague simulant) organisms, and proteins (toxin simulants) and constructed a Raman signature classifier that identifies at the species level. Subsequently, we evaluated the impact of tap water and storage time in water (aging) on the classifier performance when characterizing B. thuringiensis spores, BG spores, and EC cell preparations. In general, the measured Raman signatures of biological organisms exhibited minimal spectral variability with respect to the age of a resting suspension and water matrix composition. The observed signature variability did not substantially degrade discrimination performance at the genus and species levels. In addition, Raman chemical imaging spectroscopy was used to distinguish a mixture of BG spores and EC cells at the single cell level. PMID:18230198

Tripathi, Ashish; Jabbour, Rabih E; Treado, Patrick J; Neiss, Jason H; Nelson, Matthew P; Jensen, Janet L; Snyder, A Peter

2008-01-01

113

A virtual experiment control and data acquisition system for in situ laser heated diamond anvil cell Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Doubled-sided laser heated diamond anvil cell methods allow simultaneous in situ confocal Raman measurements of materials up to megabar pressures and high temperatures. This paper describes a virtual control and data acquisition system developed to automate setups for simultaneous Raman/laser heating experiments. The system enables reduction of experiment time by ~90% in comparison to manual operations, allowing measurements of high quality Raman spectra of even highly reactive or diffusive samples, such as hydrogen at extreme conditions using continuous wave laser heating. These types of measurements are very difficult and often impossible to obtain in a manual operation mode. Complete data archiving and accurate control of various experimental parameters (e.g., on-the-fly temperature determination and self-adjusting data collection time to avoid signal saturation) can be done, and open up possibilities of other types of experiments involving extreme conditions.

Subramanian, N.; Struzhkin, Viktor V.; Goncharov, Alexander F.; Hemley, Russell J.

2010-09-01

114

Laser Raman spectroscopy of THF clathrate hydrate in the temperature range 90-300 K.  

PubMed

In situ Raman and Fourier transform infrared (FTIR-NIR) spectroscopic studies on tetrahydrofuran (THF-C(4)H(8)O) clathrate hydrate (CH) were reported. The Raman results in lattice (64 cm(-1)), ring breathing and C-H stretching mode regions are in conformity with earlier reports, while the FTIR (NIR) studies in second order mode region were reported for the first time. Comparison of the results indicate that the band assigned to ring breathing mode around 922 cm(-1) (in Raman) and corresponding second order mode in NIR around 4295 cm(-1) broadens and shifts in enclathrated THF. The ring breathing mode at lower temperatures (T<120 K) is highly asymmetric and splits into two and are due to different host-guest interactions at lower temperatures. PMID:17728176

Prasad, P S R; Shiva Prasad, K; Thakur, N K

2007-12-15

115

Raman spectroscopy of microbial pigments.  

PubMed

Raman spectroscopy is a rapid nondestructive technique providing spectroscopic and structural information on both organic and inorganic molecular compounds. Extensive applications for the method in the characterization of pigments have been found. Due to the high sensitivity of Raman spectroscopy for the detection of chlorophylls, carotenoids, scytonemin, and a range of other pigments found in the microbial world, it is an excellent technique to monitor the presence of such pigments, both in pure cultures and in environmental samples. Miniaturized portable handheld instruments are available; these instruments can be used to detect pigments in microbiological samples of different types and origins under field conditions. PMID:24682303

Jehli?ka, Jan; Edwards, Howell G M; Oren, Aharon

2014-06-01

116

OPO CARS: coherent anti-Stokes Raman spectroscopy using tunable optical parametric oscillators injection-seeded by external-cavity diode lasers  

Microsoft Academic Search

Coherent anti-Stokes Raman spectroscopy (CARS) is performed on nitrogen gas using the signal wave from a pulsed ?-barium borate optical parametric oscillator (OPO), which has a passive ring cavity and is injection-seeded at its idler wavelength by a single-mode, external-cavity diode laser. The observed CARS linewidths are consistent with an optical bandwidth of 0.01 cm?1 for the continuously tunable OPO

G. W. Baxter; M. J. Johnson; J. G. Haub; B. J. Orr

1996-01-01

117

Filament-driven impulsive Raman spectroscopy.  

PubMed

Vibrational Raman spectroscopy is performed in the gas phase using a femtosecond laser pulse undergoing filamentation as an impulsive excitation source. The molecular coherence induced by the filamentary pulse is subsequently probed using a narrowband, sub-picosecond laser pulse to produce Raman spectra of gas phase species in a few tens of milliseconds (~10 laser shots). Pulse shortening with concomitant spectral broadening during filamentation results in a pulse that is both sufficiently short and of sufficient spectral power density to impulsively excite the highest energy ground state vibrations (up to 4158 cm(-1) corresponding to H(2)). Gas phase detection of chloroform, methylene chloride, cyclohexane, toluene, pentane, triethylamine, ammonia, nitromethane, and gasoline is performed. PMID:21977899

Odhner, Johanan H; McCole, Erin T; Levis, Robert J

2011-11-24

118

Linear Raman spectroscopy on aqueous aerosols: influence of nonlinear effects on detection limits  

Microsoft Academic Search

The influence of stimulated Raman scattering on the characterization of aqueous aerosols by linear Raman spectroscopy was studied experimentally. Raman scattering from a chain of microdroplets was excited by an argon ion laser. Holographic Raman filters, a spectrograph and a cryogenically cooled CCD detector were used to record the spectra. A procedure to estimate the detection limits of Raman instrumentation

R. Vehring

1998-01-01

119

Infrared and Raman Spectroscopy  

Microsoft Academic Search

\\u000a A brief introduction of applications of infrared and Raman spectroscopic techniques to zeolites, zeolite chemistry and the\\u000a chemistry that occurs in zeolite pores and channels is given in this chapter. The basic information, obtained by using these\\u000a techniques, of zeolite frameworks including isomorphous substitution, perturbation of zeolite frameworks by foreign cations,\\u000a and cation locations, zeolite surfaces including OH groups, acid

Xinsheng Liu

2010-01-01

120

Healing and evaluating guinea pig skin incision after surgical suture and laser tissue by welding using in vivo Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Changes in collagen in the wound during the healing process of guinea pig skin following surgical incisions and LTW was evaluated using in vivo, using Raman spectroscopy. Raman spectroscopy provided information regarding the internal structure of the proteins. After the incisions were closed either by suturing or by LTW the ratio of the Raman peaks of the amide III (1247 cm-1) band to a peak at 1326 cm-1 used to evaluate the progression of collagen deposition. Histopathology was used as the gold standard. LTW skin demonstrated better healing than sutured skin, exhibiting minimal hyperkeratosis, minimal collagen deposition, near-normal surface contour, and minimal loss of dermal appendages. This work is important to plastic surgery.

Alimova, A.; Sriramoju, V.; Chakraverty, R.; Muthukattil, R.; Alfano, R. R.

2010-02-01

121

Er:YAG laser treatments on dentine surface: micro-Raman spectroscopy and SEM analysis  

Microsoft Academic Search

Objective. This study aims to give an insight into the chemical and structural modifications occurring in laser treated dentine surface, as a tool to plan a new class of dental materials specific for the dental restoration when laser technologies are used. For this purpose the effect of Er:YAG (Erbium–Yttrium Aluminium Garnet) laser treatments on human dentine surface has been investigated.Methods.

C Camerlingo; M Lepore; G. M Gaeta; R Riccio; C Riccio; A De Rosa; M De Rosa

2004-01-01

122

Remote adjustable focus Raman spectroscopy probe  

DOEpatents

A remote adjustable focus Raman spectroscopy probe allows for analyzing Raman scattered light from a point of interest external probe. An environmental barrier including at least one window separates the probe from the point of interest. An optical tube is disposed adjacent to the environmental barrier and includes a long working length compound lens objective next to the window. A beam splitter and a mirror are at the other end. A mechanical means is used to translated the prove body in the X, Y, and Z directions resulting in a variable focus optical apparatus. Laser light is reflected by the beam splitter and directed toward the compound lens objective, then through the window and focused on the point of interest. Raman scattered light is then collected by the compound lens objective and directed through the beam splitter to a mirror. A device for analyzing the light, such as a monochrometer, is coupled to the mirror.

Schmucker, John E. (Hurt, VA); Blasi, Raymond J. (Harrison City, PA); Archer, William B. (Bethel Park, PA)

1999-01-01

123

Modulated Raman spectroscopy technique for real-time fluorescence rejection  

NASA Astrophysics Data System (ADS)

Raman spectroscopy is a label-free and non-invasive method that measures the inelastic scattered light from a sample giving insight into the vibration eigenmodes of the excited molecules. Raman spectroscopy provides a detailed chemical composition of the sample, constituting a sort of its chemical fingerprint. Although Raman spectroscopy is a useful technique to identify and quantify species in a given matrix, it has been severely limited in its applicability by fluorescence. Spectrally, this fluorescence occurs at the same wavelength as the Raman signal and is often several orders of magnitude more intense that the weak chemical transitions probed by Raman spectroscopy. Often, this fluorescence background and its natural variability make biochemical analysis using Raman spectroscopy impractical. In this work, we present the theory and the implementation of an innovative modulated Raman spectroscopy technique to filter out the Raman spectra from the fluorescence background by modulating of the excitation wavelength. The method is based on the continuous wavelength shift of the Raman peaks with the modulation of the laser wavelength while the fluorescence background remains static. Exploiting this physical property allows us to clearly distinguish between the Raman signal and the fluorescence background. Our method is related to wavelength shifting Raman spectroscopy but incorporates two key novel elements: (i) the use of more than two excitation wavelengths and (ii) multi-channel lock-in detection of the Raman signal for suppression of the fluorescence background. Our results establish a direct and practical approach for fluorescence background suppression in 'real-time' Raman spectroscopy for in-vivo biomedical applications.

Mazilu, Michael; de Luca, Anna Chiara; Riches, Andrew; Herrington, Simon; Dholakia, Kishan

2010-02-01

124

Phage phi X174 probed by laser Raman spectroscopy: evidence for capsid-imposed constraint on DNA secondary structure.  

PubMed

The Raman spectrum of the isometric bacteriophage phi X174 contains a number of well-resolved bands which have been assigned unambiguously to proteins of the capsid or to the single-stranded DNA (ssDNA) genome. Additional Raman bands of protein and DNA, which are partially overlapped in the spectrum of virus, have been resolution enhanced by Fourier deconvolution to permit improved semiquantitative measurement of spectral intensities and frequencies for structural conclusions. Raman conformation markers indicate that the ssDNA molecule within the capsid contains nucleosides of C2'-endo sugar pucker and anti-glycoside bond orientation, but the nucleic acid backbone lacks the geometry characteristic of B-form DNA. The Raman profile of encapsidated phi X DNA indicates a backbone more similar to heat-denatured DNA than to DNA containing hairpinlike secondary structure. This finding suggests limited interbase interactions in the packaged genome, which is presumably the result of constraints imposed by the viral capsid. Thus, the extensive pairing and stacking of bases indicated by Raman profiles from ssRNA viruses are not evident for the phi X174 chromosome. Overall, the proteins of the virion contain extensive beta-sheet and irregular secondary structures. Fourier deconvolution of the Raman amide I band provides an estimate of the percentage of total beta-sheet structure (approximately 60%) in all proteins of the virion. The amide III region of the spectrum confirms that beta-sheet and irregular domains are the predominant protein secondary structures. Samples of phi X174 concentrated for Raman spectroscopy by either ultracentrifugation or ultrafiltration exhibit nearly identical Raman spectra, indicating that either method can be employed to prepare intact virus without significant loss of DNA or protein components. PMID:2954582

Incardona, N L; Prescott, B; Sargent, D; Lamba, O P; Thomas, G J

1987-03-24

125

Raman spectroscopy of bone metastasis  

NASA Astrophysics Data System (ADS)

Raman spectroscopy of bone has been used to characterize chemical changes occurring in diseases such as osteoporosis, osteoarthritis and osteomyelitis. Metastasis of cancer into bone causes changes to bone quality that are similar to those observed in osteoporosis, such as decreased bone strength, but with an accelerated timeframe. In particular, osteolytic (bone degrading) lesions in bone metastasis have a marked effect on patient quality of life because of increased risk of fractures, pain, and hypercalcemia. We use Raman spectroscopy to examine bone from two different mouse models of osteolytic bone metastasis. Raman spectroscopy measures physicochemical information which cannot be obtained through standard biochemical and histological measurements. This study was reviewed and approved by the University of Michigan University Committee on the Care and Use of Animals. Two mouse models of prostate cancer bone metastasis, RM1 (n=3) and PC3-luc (n=4) were examined. Tibiae were injected with RM1 or PC3-luc cancer cells, while the contralateral tibiae received a placebo injection for use as controls. After 2 weeks of incubation, the mice were sacrificed and the tibiae were examined by Raman microspectroscopy (?=785 nm). Spectroscopic markers corresponding to mineral stoichiometry, bone mineralization, and mineral crystallinity were compared in spectra from the cancerous and control tibiae. X-ray imaging of the tibia confirmed extensive osteolysis in the RM1 mice, with tumor invasion into adjoining soft tissue and moderate osteolysis in the PC3-luc mice. Raman spectroscopic markers indicate that osteolytic lesions are less mineralized than normal bone tissue, with an altered mineral stoichiometry and crystallinity.

Esmonde-White, Karen A.; Sottnik, Joseph; Morris, Michael; Keller, Evan

2012-02-01

126

FT-Raman Spectroscopy: A Catalyst for the Raman Explosion?  

ERIC Educational Resources Information Center

The limitations of Fourier transform (FT) Raman spectroscopy, which is used to detect and analyze the scattered radiation, are discussed. FT-Raman has served to revitalize a field that was lagging and the presence of Raman instrumentation as a routine analytical tool is established for the foreseeable future.

Chase, Bruce

2007-01-01

127

Polymer-capped fiber-optic Raman probe for non-invasive Raman spectroscopy.  

PubMed

Advances in fiber optic probe design are moving Raman spectroscopy into the clinic, although there remain important practical problems. While much effort has been devoted to minimizing Raman and fluorescence background from fibers, less attention has been given to the need to generate reference Raman signals that can correct for variations in tissue albedo, which is important in quantifying changes in tissue composition. To address this shortcoming, we have developed a fiber optic probe that incorporates a fluorinated ethylene-propylene copolymer (FEP) cap at the end of each excitation fiber. Transmission of laser light through the transparent cap generates a 732 cm(-1) Raman band whose intensity scales linearly with the laser power delivered to the tissue of interest. In our first design, the FEP cap functions as a waveguide with only a small insertion loss (~5%). Laser transmission through 1 mm of the polymer is sufficient to generate a usable reference Raman signal. We show the application of the probe to quantitative non-invasive Raman spectroscopy of animal tissues using rat leg phantoms as models. Ex-vivo Raman spectroscopy of excised rat tibia supports the use of the probe for spectroscopy of various tissues. These results provide proof of principle that the Raman probe can be used in multiple spectroscopic applications. PMID:22059232

Okagbare, Paul I; Morris, Michael D

2012-01-01

128

Polymer-capped fiber-optic Raman probe for non-invasive Raman spectroscopy  

PubMed Central

Advances in fiber optic probe design are moving Raman spectroscopy into the clinic, although there remain important practical problems. While much effort has been devoted to minimizing Raman and fluorescence background from fibers, less attention has been given to the need to generate reference Raman signals that can correct for variations in tissue albedo, which is important in quantifying changes in tissue composition. To address this shortcoming, we have developed a fiber optic probe that incorporates a fluorinated ethylene-propylene copolymer (FEP) cap at the end of each excitation fiber. Transmission of laser light through the transparent cap generates a 732 cm?1 Raman band whose intensity scales linearly with the laser power delivered to the tissue of interest. In our first design, the FEP cap functions as a waveguide with only a small insertion loss (~5%). Laser transmission through 1 mm of the polymer is sufficient to generate a usable reference Raman signal. We show the application of the probe to quantitative non-invasive Raman spectroscopy of animal tissues using rat leg phantoms as models. Ex-vivo Raman spectroscopy of excised rat tibia supports the use of the probe for spectroscopy of various tissues. These results provide proof of principle that the Raman probe can be used in multiple spectroscopic applications.

Okagbare, Paul I.; Morris, Michael D.

2012-01-01

129

Planetary Surface Exploration Using Raman Spectroscopy on Rovers and Landers  

NASA Astrophysics Data System (ADS)

Planetary surface exploration using laser induced breakdown spectroscopy (LIBS) to probe the composition of rocks has recently become a reality with the operation of the mast-mounted ChemCam instrument onboard the Curiosity rover. Following this success, Raman spectroscopy has steadily gained support as a means for using laser spectroscopy to identify not just composition but mineral phases, without the need for sample preparation. The RLS Raman Spectrometer is included on the payload for the ExoMars mission, and a Raman spectrometer has been included in an example strawman payload for NASA’s Mars 2020 mission. Raman spectroscopy has been identified by the community as a feasible means for pre-selection of samples on Mars for subsequent return to Earth. We present a next-generation instrument that builds on the widely used green-Raman technique to provide a means for performing Raman spectroscopy without the background noise that is often generated by fluorescence of minerals and organics. Microscopic Raman spectroscopy with a laser spot size smaller than the grains of interest can provide surface mapping of mineralogy while preserving morphology. A very small laser spot size 1 µm) is often necessary to identify minor phases that are often of greater interest than the matrix phases. In addition to the difficulties that can be posed by fine-grained material, fluorescence interference from the very same material is often problematic. This is particularly true for many of the minerals of interest that form in environments of aqueous alteration and can be highly fluorescent. We use time-resolved laser spectroscopy to eliminate fluorescence interference that can often make it difficult or impossible to obtain Raman spectra. We will discuss significant advances leading to the feasibility of a compact time-resolved spectrometer, including the development of a new solid-state detector capable of sub-ns time resolution. We will present results on planetary analog minerals to demonstrate the instrument performance including fluorescence rejection.

Blacksberg, Jordana; Alerstam, E.; Maruyama, Y.; Charbon, E.; Rossman, G. R.

2013-10-01

130

Correlation of surface-enhanced Raman spectroscopy and laser desorption-ionization mass spectrometry acquired from silver nanoparticle substrates.  

PubMed

Applying complementary experiments, like laser desorption-ionization mass spectrometry (LDI-MS) and confocal surface-enhanced Raman microscopy, to the same physical sample location has the potential to elucidate the behavior of complex chemical and biochemical systems in ways that are not available to either method applied in isolation. In these experiments surface-enhanced Raman scattering (SERS) and LDI-MS are applied to the same sample spot using a common structure, deposited Ag colloids, both as ionization matrix and simultaneously as enhancing media for surface-enhanced Raman scattering of small organic molecules, dyes and lipids, and the behavior is compared. Three compounds-p-aminothiophenol (ATP), rhodamine 6G and cholesterol-which exhibit different strengths of interaction with Ag are examined in detail by correlated SERS and LDI-MS. The related mechanisms of nanoparticle-assisted desorption-ionization and Raman enhancement are explored by correlating mass and Raman spectra. The correlated spectra highlight the manner in which the different test compounds interact with plasmonic metal nanostructures. These coupled studies yield new insight into the transition of analyte from the metal-solution interface to gaseous ions, including, in the case of organothiols, a rich set of mixed clusters that provide chemical insight into the ion formation process. PMID:22314587

Nie, Bei; Masyuko, Rachel N; Bohn, Paul W

2012-03-21

131

Heterodyne laser spectroscopy system  

DOEpatents

A heterodyne laser spectroscopy system utilizes laser heterodyne techniques for purposes of laser isotope separation spectroscopy, vapor diagnostics, processing of precise laser frequency offsets from a reference frequency, and provides spectral analysis of a laser beam.

Wyeth, Richard W. (Livermore, CA); Paisner, Jeffrey A. (San Ramon, CA); Story, Thomas (Antioch, CA)

1990-01-01

132

Heterodyne laser spectroscopy system  

DOEpatents

A heterodyne laser spectroscopy system utilizes laser heterodyne techniques for purposes of laser isotope separation spectroscopy, vapor diagnostics, processing of precise laser frequency offsets from a reference frequency and the like, and provides spectral analysis of a laser beam.

Wyeth, Richard W. (Livermore, CA); Paisner, Jeffrey A. (San Ramon, CA); Story, Thomas (Antioch, CA)

1989-01-01

133

Raman and Photoluminescence Spectroscopy in Mineral Identification  

NASA Astrophysics Data System (ADS)

Raman spectroscopy is particularly useful for rapid identification of minerals and gemstones. Raman spectrometers also allow PL studies for authentication of samples and geological provenance, diamond type screening and detection of HPHT treatments.

Kuehn, J. W.

2014-06-01

134

Laser wavelength selection for Raman spectroscopy of microbial pigments in situ in Antarctic desert ecosystem analogues of former habitats on Mars  

NASA Astrophysics Data System (ADS)

The vital ultraviolet- (UV-) protective and photosynthetic pigments of cyanobacteria and lichens (microbial symbioses) that dominate primary production in Antarctic desert ecosystems auto-fluoresce at short wavelengths. We therefore use a long-wavelength (1064 nm) infrared laser for non-intrusive in situ Raman spectrometry of their ecologically significant compounds (especially pigments). To confirm that the power loss at this longer wavelength is justified to avoid swamping by background fluorescence, we compared Raman spectra obtained with excitation at 1064, 852, 830, 785, 633 and 515 nm. These are typical of lasers used for Raman spectroscopy. We analysed communities of the cyanobacterium Nostoc commune and the highly pigmented lichens Acarospora chlorophana and Caloplaca saxicola. These require screening compounds (e.g. pigments such as scytonemin in cyanobacteria and rhizocarpic acid in the fungal symbiont of lichens). They are augmented by quenching pigments (e.g. carotenoids) to dissipate the energy of free radicals generated by penetrating UV. We also analysed organisms having avoidance strategies (e.g. endolithic communities within translucent rocks, including the common cyanobacterium Chroococcidiopsis). These require accessory pigments for photosynthesis at very low light intensities. Although some organisms gave useable Raman spectra with short-wavelength lasers, 1064 nm was the only excitation that was consistently excellent for all organisms. We conclude that a 1064 nm Raman spectrometer, miniaturized using an InGaAs detector, is the optimal instrument for in situ studies of pigmented microbial communities at the limits of life on Earth. This has practical potential for the quest for biomolecules residual from any former surface life on Mars.

Edwards, Howell G. M.; Newton, Emma M.; Wynn-Williams, David D.; Dickensheets, David; Schoen, Chris; Crowder, Chelle

2002-10-01

135

Transcutaneous Raman Spectroscopy of Bone  

NASA Astrophysics Data System (ADS)

Clinical diagnoses of bone health and fracture risk typically rely upon measurements of bone density or structure, but the strength of a bone is also dependent upon its chemical composition. One technology that has been used extensively in ex vivo, exposed-bone studies to measure the chemical composition of bone is Raman spectroscopy. This spectroscopic technique provides chemical information about a sample by probing its molecular vibrations. In the case of bone tissue, Raman spectra provide chemical information about both the inorganic mineral and organic matrix components, which each contribute to bone strength. To explore the relationship between bone strength and chemical composition, our laboratory has contributed to ex vivo, exposed-bone animal studies of rheumatoid arthritis, glucocorticoid-induced osteoporosis, and prolonged lead exposure. All of these studies suggest that Raman-based predictions of biomechanical strength may be more accurate than those produced by the clinically-used parameter of bone mineral density. The utility of Raman spectroscopy in ex vivo, exposed-bone studies has inspired attempts to perform bone spectroscopy transcutaneously. Although the results are promising, further advancements are necessary to make non-invasive, in vivo measurements of bone that are of sufficient quality to generate accurate predictions of fracture risk. In order to separate the signals from bone and soft tissue that contribute to a transcutaneous measurement, we developed an overconstrained extraction algorithm that is based upon fitting with spectral libraries derived from separately-acquired measurements of the underlying tissue components. This approach allows for accurate spectral unmixing despite the fact that similar chemical components (e.g., type I collagen) are present in both soft tissue and bone and was applied to experimental data in order to transcutaneously detect, to our knowledge for the first time, age- and disease-related spectral differences in murine bone.

Maher, Jason R.

136

Femtosecond broadband stimulated Raman spectroscopy: Apparatus and methods  

Microsoft Academic Search

The laser, detection system, and methods that enable femtosecond broadband stimulated Raman spectroscopy (FSRS) are presented in detail. FSRS is a unique tool for obtaining high time resolution (<100 fs) vibrational spectra with an instrument response limited frequency resolution of <10 cm?1. A titanium:Sapphire-based laser system produces the three different pulses needed for FSRS: (1) A femtosecond visible actinic pump

David W. McCamant; Philipp Kukura; Sangwoon Yoon; Richard A. Mathies

2004-01-01

137

Femtosecond broadband stimulated Raman spectroscopy: Apparatus and methods  

Microsoft Academic Search

The laser, detection system, and methods that enable femtosecond broadband stimulated Raman spectroscopy (FSRS) are presented in detail. FSRS is a unique tool for obtaining high time resolution (<100 fs) vibrational spectra with an instrument response limited frequency resolution of <10 cm-1. A titanium:Sapphire-based laser system produces the three different pulses needed for FSRS: (1) A femtosecond visible actinic pump

David W. McCamant; Philipp Kukura; Sangwoon Yoon; Richard A. Mathies

2004-01-01

138

Application of Raman Spectroscopy for Nondestructive Evaluation of Composite Materials  

NASA Technical Reports Server (NTRS)

This paper will present an overview of efforts to investigate the application of Raman spectroscopy for the characterization of Kevlar materials. Raman spectroscopy is a laser technique that is sensitive to molecular interactions in materials such as Kevlar, graphite and carbon used in composite materials. The overall goal of this research reported here is to evaluate Raman spectroscopy as a potential nondestructive evaluation (NDE) tool for the detection of stress rupture in Kevlar composite over-wrapped pressure vessels (COPVs). Characterization of the Raman spectra of Kevlar yarn and strands will be presented and compared with analytical models provided in the literature. Results of testing to investigate the effects of creep and high-temperature aging on the Raman spectra will be presented.

Washer, Glenn A.; Brooks, Thomas M. B.; Saulsberry, Regor

2007-01-01

139

Raman spectroscopy at high pressure and high temperature. Phase transitions and thermodynamic properties of minerals  

Microsoft Academic Search

An outline of recent developments in Raman spectroscopy at high pressure, high temperature and combined high pressure and high temperature is presented. The instrumental and technical aspects of Raman spectroscopy, and coupling of diamond anvil cells and miniature furnaces to Raman microspectrometers are discussed. Some potential pitfalls, such as the thermal pressure in laser heated diamond anvil cells or the

P. Gillet

1996-01-01

140

Raman spectroscopy of irradiated organic matter  

NASA Astrophysics Data System (ADS)

Raman spectroscopy of a range of irradiated and nonirradiated natural terrestrial bitumens has revealed that radiolytic alteration is generally associated with an increase in structural disorganisation. An interpretational methodology designed to overcome the considerable difficulties in obtaining reproducible, meaningful parameters of structural disorganisation is also presented, and should prove useful for future Raman applications. Raman investigation of a set of bitumens reported to have formed by the radiolytic polymerisation of light hydrocarbons, such as methane, has revealed excessive structural disorganisation, relative to biogenic complex-hydrocarbon-derived bitumens of similar radioelement concentrations, which may indicate the importance of precursor materials on the organic products of irradiation. Variations in the R1 ratio (D1/G band intensity) are found to be the best guide to variations in structural organisation. Comparisons of Raman spectra of the same sample, but produced by different exciting wavelengths, reveal the importance of the selection of a suitable laser wavelength. The results are discussed in terms of analyses of irradiated organic matter in the solar system, especially cometary nuclei and carbonaceous chondrites.

Court, Richard W.; Sephton, Mark A.; Parnell, John; Gilmour, Iain

2007-05-01

141

Raman accumulator as a fusion laser driver  

DOEpatents

Apparatus for simultaneous laser pulse amplification and compression, using multiple pass Raman scattering in one Raman cell and pulse switchout from the optical cavity through use of a dichroic device associated with the Raman cell.

George, E.V.; Swingle, J.C.

1982-03-31

142

Effect of the laser and light-emitting diode (LED) phototherapy on midpalatal suture bone formation after rapid maxilla expansion: a Raman spectroscopy analysis.  

PubMed

The aim of this study was to analyze the effect of laser or light-emitting diode (LED) phototherapy on the bone formation at the midpalatal suture after rapid maxilla expansion. Twenty young adult male rats were divided into four groups with 8 days of experimental time: group 1, no treatment; group 2, expansion; group 3, expansion and laser irradiation; and group 4, expansion and LED irradiation. In groups 3 and 4, light irradiation was in the first, third, and fifth experimental days. In all groups, the expansion was accomplished with a helicoid 0.020? stainless steel orthodontic spring. A diode laser (?780 nm, 70 mW, spot of 0.04 cm(2), t?=?257 s, spatial average energy fluence (SAEF) of 18 J/cm(2)) or a LED (?850 nm, 150 mW?±?10 mW, spot of 0.5 cm(2), t?=?120 s, SAEF of 18 J/cm(2)) were used. The samples were analyzed by Raman spectroscopy carried out at midpalatal suture and at the cortical area close to the suture. Two Raman shifts were analyzed: ?960 (phosphate hydroxyapatite) and ?1,450 cm(-1) (lipids and protein). Data was submitted to statistical analysis. Significant statistical difference (p???0.05) was found in the hydroxyapatite (CHA) peaks among the expansion group and the expansion and laser or LED groups. The LED group presented higher mean peak values of CHA. No statistical differences were found between the treated groups as for collagen deposition, although LED also presented higher mean peak values. The results of this study using Raman spectral analysis indicate that laser and LED light irradiation improves deposition of CHA in the midpalatal suture after orthopedic expansion. PMID:23430219

Rosa, Cristiane Becher; Habib, Fernando Antonio Lima; de Araújo, Telma Martins; Aragăo, Juliana Silveira; Gomes, Rafael Soares; Barbosa, Artur Felipe Santos; Silveira, Landulfo; Pinheiro, Antonio L B

2014-05-01

143

Improved accuracy of quantification of analytes in human body fluids by near-IR laser Raman spectroscopy with new algorithms  

NASA Astrophysics Data System (ADS)

Near infrared Raman spectroscopy has been successfully used to analyze ethanol and acetaminophen in human urine samples quantitatively. The new algorithms incorporating the intrinsic spectrum of the analyte of interest into the multivariate calibration were examined to improve the accuracy of the predicted concentrations. Comparing with commonly used partial least squares calibration, it was found that the methods using the intrinsic spectrum of the analyte of interest always achieved much higher accuracy, particularly when the interference from other undesired chemicals in the samples are severe.

Qu, Jianan Y.; Yau, On L.; Yau, Sze-Fong M.

1999-07-01

144

Laser Spectroscopy  

NASA Astrophysics Data System (ADS)

Degenerate gases. Probing vortex pair sizes in the Berezinskii-Kosterlitz-Thouless regime on a two-dimensional lattice of Bose-Einstein condensates / V. Schweikhard ... [et al.]. Interacting Bose-Einstein condensates in random potentials / P. Bouyer ... [et al.]. Towards quantum magnetism with ultracold atoms in optical lattices / I. Bloch -- Precision measurement and fundamental physics. T-violation and the search for a permanent electric dipole moment of the mercury atom / E. N. Fortson -- Quantum information and control I. Quantum information processing and ramsey spectroscopy with trapped ions / C. F. Roos ... [et al.]. Quantum non-demolition counting of photons in a cavity / S. Haroche ... [et al.] -- Ultra-fast control and spectroscopy. Frequency-Comb- assisted mid-infrared spectroscopy / P. de Natale ... [et al.] -- Precision measurement and applications. Precision gravity tests by atom interferometry / G. M. Tino ... [et al.] -- Novel spectroscopic applications. On a variation of the proton-electron mass ratio / W. Ubachs ... [et al.] -- Quantum information and control II. Quantum interface between light and atomic ensembles / H. Krauter ... [et al.] -- Degenerate Fermi gases. An atomic Fermi gas near a P-wave Feshbach resonance / D. S. Jin, J. P. Gaebler and J. T. Stewart. Bragg scattering of correlated atoms from a degenerate Fermi gas / R. J. Ballagh, K. J. Challis and C. W. Gardiner -- Spectroscopy and control of atoms and molecules. Stark and Zeeman deceleration of neutral atoms and molecules / S. D. Hogan ... [et al.]. Generation of coherent, broadband and tunable soft x-ray continuum at the leading edge of the driver laser pulse / A. Jullien ... [et al.]. Controlling neural atoms and photons with optical conveyor belts and ultrathin optical fibers / D. Meschede. W. Alt and A. Rauschenbeutel -- Spectroscopy on the small scale. Wide-field cars-microscopy / C. Heinrich ... [et al.]. Atom nano-optics and nano-lithography / V. I. Balykin ... [et al.] -- Pinhead town talk, public lecture and mountainfilm. The quantum revolution - towards a new generation of supercomputers / R. Blatt -- Cold atoms and molecules I. Ultracold & ultrafast: making and manipulating ultracold molecules with time-dependent laser fields / C. P. Koch ... [et al.]. Bose-Einstein condensates on magnetic film microstructures / M. Singh ... [et al.] -- Cold atoms and molecules II. Ultracold metastable Helium-4 and Helium-3 gases / W. Vassen ... [et al.] -- Single atoms and quantum optics I. Recent progress on the manipulation of single atoms in optical tweezers for quantum computing / A. Browaeys ... [et al.]. Progress in atom chips and the integration of optical microcavities / E. A. Hinds ... [et al.] -- Single atoms and quantum optics II. Quantum optics with single atoms and photons / H. J. Kimble -- Optical atomic clocks. Frequency comparison of Al[symbol] and Hg[symbol] optical standards / T. Rosenband ... [et al.]. Sr optical clock with high stability and accuracy / A. Ludlow ... [et al.].

Hollberg, Leo; Bergquist, James Charles; Kasevich, Mark A.

2008-04-01

145

Femtosecond stimulated Raman spectroscopy of ultrafast biophysical reaction dynamics  

Microsoft Academic Search

I have developed the technique of femtosecond stimulated Raman spectroscopy (FSRS), which enables the rapid acquisition of vibrational spectra with <100-fs time-resolution and <15-cm-1 frequency-resolution. FSRS uses three laser pulses: (1) a femtosecond visible actinic pump that initiates the photochemistry, (2) a narrow bandwidth picosecond Raman pump that provides the energy for amplification of the probe, and (3) a femtosecond

David William McCamant

2004-01-01

146

Precise measurement of the depolarization ratio from photoacoustic Raman spectroscopy  

Microsoft Academic Search

A new method for the accurate determination of the Raman depolarization ratio is reported with an improved setup for photoacoustic Raman spectroscopy (PARS). The precise measurement is achieved by measuring the dependence of the acoustic signal intensity on the cross-angle between the polarizations of two incident laser beams. We demonstrate this sensitive and simple method with several gaseous molecules,suchasCH4 andH2.Themeasuredresultsofdepolarizationratiosagreewellwiththetheoretical

Yuanqin Yu; Ke Lin; Xiaoguo Zhou; Hua Wang; Shilin Liu; Xingxiao Ma

2007-01-01

147

Raman Microprobe Spectroscopy of Halloysite  

Microsoft Academic Search

The Raman spectra of a tubular halloysite originating from Matauri Bay, New Zealand, have been obtained using a Renishaw 1000 Raman microscope system. The Raman microprobe enables the Raman spectra of crystals as small as 0.8 p~m diameter to be obtained over the complete wavelength range and allows spectral variations along the different crystal axes to be studied. Three bands

R. L. Frost; H. E SHURVELLt

1997-01-01

148

Raman spectroscopy of graphitic foams  

NASA Astrophysics Data System (ADS)

The recently developed pitch-based graphitic foams have a very high thermal conductivity to weight ratio. This property allows graphitic foams to be used in several thermal management applications, especially in the aeronautics and aerospace industries. Raman spectroscopy studies were performed on the different structural regions of the foam, yelding important information on the structural properties of the graphitic foams, as well as on the physical properties of graphite. The graphitic foam was found to be composed of two intermixed graphitic structures, one with stacked planes and one with a turbostratic structure. This special structure allowed for a simultaneous study of the properties of two-dimensional (2D) and three-dimensional (3D) graphitic structures. The dispersion of the G' band was found to be different for 2D and 3D graphite. The intensity of the D -band Raman feature was used to probe the density of defects in the structure, leading to the conclusion that the defects are mainly localized in the 2D structures. A simple model is proposed to explain the origin of the two different structures within the graphitic foam. Also, the dependence of the G' band on polarization is addressed.

Barros, E. B.; Demir, N. S.; Souza Filho, A. G.; Mendes Filho, J.; Jorio, A.; Dresselhaus, G.; Dresselhaus, M. S.

2005-04-01

149

A study by in situ laser Raman spectroscopy of VPO catalysts for n-butane oxidation to maleic anhydride. 1. Preparation and characterization of pure reference phases  

SciTech Connect

An in situ laser Raman spectroscopy (LRS) cell has been constructed in order to study the evolution of the local structure of the vanadium phosphate catalysts for n-butane oxidation to maleic anhydride in catalytic conditions. The LRS cell is described with the on line disposal for detection of the evolving gases. The first issue concerns the preparation and the physicochemical characterization of the reference phases of the VPO system: (VO){sub 2}P{sub 2}O{sub 7}, {alpha}{sub 11}, {beta}, {gamma}, and {delta} VOPO{sub 4}. Their purity was controlled by X-ray diffraction and {sup 31}P and {sup 51}V solid NMR and their LRS spectra were studied in the 800-1,200 cm{sup {minus}1} range characteristic of the P-0 and V-O bonds. Among these phases only {delta} VOPO{sub 4} is partly transformed (into {alpha}{sub 11} VOPO{sub 4}) in the catalytic conditions. From the evolution of their respective Raman spectra with temperature and with conditions of hydration, new proposals for the structure of {gamma} VOPO{sub 4} are given. They are in agreement with the solid state NMR data. Raman spectra of the phases exhibit features specific enough to allow identification of the different VPO structures.

Abdelouahab, F.B.; Olier, R. (Ecole Centrale de Lyon, Ecully (France)); Guilhaume, N.; Lefebvre, F.; Volta, J.C. (CNRS, Villeurbanne (France))

1992-03-01

150

Electrochemical and laser raman spectroscopy studies of stainless steel in 0. 15M NaC1 solution  

SciTech Connect

This paper reports on potentiodynamic polarization curves measured by Type AISI 304 and 316 stainless steels in 0.15M NaCl solution at 4, 20, and 40[degrees]C. The pitting potentials decreased with increasing temperature. A positive effect on the inhibition of passivity breakdown was found in the presence of molybdenum. Surface enhanced Raman spectroscopy (SERS) was carried out on AISI 316 stainless steel to identify the species present on the electrode surface as a function of potential. Results indicate the corrosion films to be highly disordered and most likely to consist of a mixture of the oxides and hydroxides of the component elements of the stainless steel. The potential dependence of the spectra may reflect the behavior of iron, which is the most abundant component in the alloy and most probably in the film.

erreira, M.G.S.; Mourae Silva, T.; Catarino, A. (Dept. of Chemical Engineering, Inst. Superior Tecnico, 1096 Lisboa Codex (Portugal)); Pankuch, M.; Melendres, C.A. (Materials Science and Chemical Technology Div., Argonne National Lab., Argonne, IL (United States))

1992-11-01

151

Radial profiling of microdroplets using cavity-enhanced Raman spectroscopy  

NASA Astrophysics Data System (ADS)

The composition of 7.7- mu m-radius methanol-water droplets was radially resolved by cavity-enhanced Raman spectroscopy. Optical cavity modes, encompassing well-defined radial zones within each droplet, were sequentially excited by a 514.5-nm laser beam to generate spontaneous Raman scattered light. The cavity-enhanced Raman spectral peaks gave information as to the identity and amount of species present. The measured radial and time dependence of the methanol concentration agreed with a diffusion-limited evaporation mode.

Lin, H.-B.; Campillo, A. J.

1995-08-01

152

In vivo Raman spectroscopy of cervix cancers  

NASA Astrophysics Data System (ADS)

Cervix-cancer is the third most common female cancer worldwide. It is the leading cancer among Indian females with more than million new diagnosed cases and 50% mortality, annually. The high mortality rates can be attributed to late diagnosis. Efficacy of Raman spectroscopy in classification of normal and pathological conditions in cervix cancers on diverse populations has already been demonstrated. Our earlier ex vivo studies have shown the feasibility of classifying normal and cancer cervix tissues as well as responders/non-responders to Concurrent chemoradiotherapy (CCRT). The present study was carried out to explore feasibility of in vivo Raman spectroscopic methods in classifying normal and cancerous conditions in Indian population. A total of 182 normal and 132 tumor in vivo Raman spectra, from 63 subjects, were recorded using a fiberoptic probe coupled HE-785 spectrometer, under clinical supervision. Spectra were acquired for 5 s and averaged over 3 times at 80 mW laser power. Spectra of normal conditions suggest strong collagenous features and abundance of non-collagenous proteins and DNA in case of tumors. Preprocessed spectra were subjected to Principal Component-Linear Discrimination Analysis (PCLDA) followed by leave-one-out-cross-validation. Classification efficiency of ~96.7% and 100% for normal and cancerous conditions respectively, were observed. Findings of the study corroborates earlier studies and suggest applicability of Raman spectroscopic methods in combination with appropriate multivariate tool for objective, noninvasive and rapid diagnosis of cervical cancers in Indian population. In view of encouraging results, extensive validation studies will be undertaken to confirm the findings.

Rubina, S.; Sathe, Priyanka; Dora, Tapas Kumar; Chopra, Supriya; Maheshwari, Amita; Krishna, C. Murali

2014-03-01

153

Time-resolved Raman spectroscopy for in situ planetary mineralogy.  

PubMed

Planetary mineralogy can be revealed through a variety of remote sensing and in situ investigations that precede any plans for eventual sample return. We briefly review those techniques and focus on the capabilities for on-surface in situ examination of Mars, Venus, the Moon, asteroids, and other bodies. Over the past decade, Raman spectroscopy has continued to develop as a prime candidate for the next generation of in situ planetary instruments, as it provides definitive structural and compositional information of minerals in their natural geological context. Traditional continuous-wave Raman spectroscopy using a green laser suffers from fluorescence interference, which can be large (sometimes saturating the detector), particularly in altered minerals, which are of the greatest geophysical interest. Taking advantage of the fact that fluorescence occurs at a later time than the instantaneous Raman signal, we have developed a time-resolved Raman spectrometer that uses a streak camera and pulsed miniature microchip laser to provide picosecond time resolution. Our ability to observe the complete time evolution of Raman and fluorescence spectra in minerals makes this technique ideal for exploration of diverse planetary environments, some of which are expected to contain strong, if not overwhelming, fluorescence signatures. We discuss performance capability and present time-resolved pulsed Raman spectra collected from several highly fluorescent and Mars-relevant minerals. In particular, we have found that conventional Raman spectra from fine grained clays, sulfates, and phosphates exhibited large fluorescent signatures, but high quality spectra could be obtained using our time-resolved approach. PMID:20830184

Blacksberg, Jordana; Rossman, George R; Gleckler, Anthony

2010-09-10

154

Study of virus by Raman spectroscopy  

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

155

Molecular velocimetry using stimulated Raman spectroscopy  

NASA Technical Reports Server (NTRS)

Molecular flow velocity of N2 was measured in a supersonic wind tunnel using inverse Raman spectroscopy. This technique employs the large Doppler shift exhibited by the molecules when the pump and probe laser beams are counter-propagating (backward scattering). A retrometer system is employed to yield a vibration-free optical configuration which has the additional advantage of obtaining both the forward and backward scattered spectra simultaneously. The linebreadths and their relative Doppler shift can be used to determine the static pressure, translational temperature, and molecular flow velocity. A demonstration of the concept was performed in a supersonic wind tunnel and included: (1) measurements over the Mach number range 2.50 to 4.63; (2) static pressure measurements (at Mach 2.50) corresponding to a Reynolds number per foot range of 1 to 5 x 10 to the 6th power; and (3) measurements behind the shock wave of a flat plate model.

Exton, R. J.; Hillard, M. E.

1984-01-01

156

Femtosecond broadband stimulated Raman spectroscopy: Apparatus and methods  

PubMed Central

The laser, detection system, and methods that enable femtosecond broadband stimulated Raman spectroscopy (FSRS) are presented in detail. FSRS is a unique tool for obtaining high time resolution (<100 fs) vibrational spectra with an instrument response limited frequency resolution of <10 cm–1. A titanium:Sapphire-based laser system produces the three different pulses needed for FSRS: (1) A femtosecond visible actinic pump that initiates the photochemistry, (2) a narrow bandwidth picosecond Raman pump that provides the energy reservoir for amplification of the probe, and (3) a femtosecond continuum probe that is amplified at Raman resonances shifted from the Raman pump. The dependence of the stimulated Raman signal on experimental parameters is explored, demonstrating the expected exponential increase in Raman intensity with concentration, pathlength, and Raman pump power. Raman spectra collected under different electronic resonance conditions using highly fluorescent samples highlight the fluorescence rejection capabilities of FSRS. Data are also presented illustrating our ability: (i) To obtain spectra when there is a large transient absorption change by using a shifted excitation difference technique and (ii) to obtain high time resolution vibrational spectra of transient electronic states.

McCamant, David W.; Kukura, Philipp; Yoon, Sangwoon; Mathies, Richard A.

2005-01-01

157

Raman spectroscopy and Raman chemical imaging of apoptotic cells  

NASA Astrophysics Data System (ADS)

Apoptosis, also known as programmed cell death, is a process in which cells initiate a series of events to trigger their own demise. Normal cells use this mechanism in the regulation of their life cycle. On the contrary, abnormal or cancer cells have lost the ability to regulate themselves by this process. Because of this, there is much interest in the study of the apoptotic process. Currently, there are many commercial assays available to detect apoptosis in cells, most of which are fluorescence based. Limitations of such fluorescent assays lead to arbitrary or inclusive results. Raman spectroscopy is a powerful technique that yields specific molecular information on samples under study. The Raman spectra obtained from cell samples are very complex, yet the differences in the complex Raman spectra analyzed using chemometric techniques can identify chemical and physiological information about cells. Furthermore, Raman spectroscopy is a sensitive, rapid, reagentless, low-cost technique, making it a superior alternative to traditional fluorescence based apoptosis assays. In this study, we have employed Raman spectroscopy and Raman chemical imaging, along with chemometric techniques, to distinguish apoptotic cells from non-apoptotic cells in two prostate cancer cell lines, PC3 and LnCAP. Initial results indicate that Raman spectra of apoptotic and non-apoptotic cells are different in both cell lines. Furthermore, chemometric analysis of the data shows that the spectra separate into two distinct populations, apoptotic and non-apoptotic. Traditional fluorescence based apoptotic assays confirm the results. This work provides ample evidence that Raman spectroscopy is a valuable tool in biomedical imaging.

Panza, Janice L.; Maier, John S.

2007-03-01

158

Characterization of Precipitates in Anodic Oxidized Ga1-xAlxAs and Ga1-xInxAs by Laser Raman Spectroscopy  

NASA Astrophysics Data System (ADS)

The effects of adding Al or In to GaAs on precipitates and their distribution in anodic oxides were studied using laser Raman spectroscopy. Crystalline As precipitated from Ga1-xAlxAs (0?x?0.54) and Ga1-xInxAs (0?x?0.15), while no species precipitated from Ga1-xInxAs (0.53?x?1) after annealing in a nitrogen atmosphere at a temperature higher than 430°C. On the other hand, amorphous species precipitated from Ga1-xInxAs (0?x?1) and no species precipitated from Ga1-xAlxAs (0.22?x?0.54) after annealing in a hydrogen atmosphere at a temperature higher than 400°C. The crystalline As is produced by a solid-state interfacial reaction at the oxide/semiconductor interface, while the amorphous species is produced by the reduction of oxides.

Eguchi, Kazuhiro; Katoda, Takashi

1985-08-01

159

Commercial anesthetic-respiratory gas monitor utilizing Raman spectroscopy  

NASA Astrophysics Data System (ADS)

A commercial gas monitor which utilizes Raman Spectroscopy has been developed to monitor anesthetic and respiratory gases in the hospital operating room. The instrument measures all molecular gases administered by the anesthesiologist in real time with fast response of breath waveform. These gases include carbon dioxide, nitrous oxide, oxygen, nitrogen and various volatile halogenated organic anesthetics, e.g. halothane, isoflurane, enflurane, sevoflurane and desflurane. The key feature of this instrument which allows it to produce adequate Raman signals with a low cost argon ion laser is measuring these gases inside the laser resonant cavity.

Gregonis, Donald E.; Van Wagenen, Richard A.; Coleman, D.; Mitchell, John R.

1990-11-01

160

Inverse Raman bands in ultrafast Raman loss spectroscopy.  

PubMed

Ultrafast Raman loss spectroscopy (URLS) is equivalent to anti-Stokes femtosecond stimulated Raman spectroscopy (FSRS), using a broadband probe pulse that extends to the blue of the narrow bandwidth Raman pump, and can be described as inverse Raman scattering (IRS). Using the Feynman dual time-line diagram, the third-order polarization for IRS with finite pulses can be written down in terms of a four-time correlation function. An analytic expression is obtained for the latter in the harmonic approximation which facilitates computation. We simulated the URLS of crystal violet (CV) for various resonance Raman pump excitation wavelengths using the IRS polarization expression with finite pulses. The calculated results agreed well with the experimental results of S. Umapathy et al., J. Chem. Phys. 133, 024505 (2010). In the limit of monochromatic Raman pump and probe pulses, we obtain the third-order susceptibility for multi-modes, and for a single mode we recover the well-known expression for the third-order susceptibility, ?(IRS) ((3)), for IRS. The latter is used to understand the mode dependent phase changes as a function of Raman pump excitation in the URLS of CV. PMID:22047247

Qiu, Xueqiong; Li, Xiuting; Niu, Kai; Lee, Soo-Y

2011-10-28

161

Investigation of optical homogeneity and photorefractive properties of lithium-niobate single crystals by the Raman-spectroscopy and laser-conoscopy methods  

NASA Astrophysics Data System (ADS)

Photorefractive properties and structural and optical homogeneity of (1) LiNbO3:Cu crystals ([Cu] = 0.015 mas %) grown from a congruent melt, (2) nominally pure stoichiometric crystals grown from a melt with 58.6 mol % of Li2O (LiNbO3stoich), and (3) nominally pure congruent crystals (LiNbO3congr) have been studied using the Raman-spectroscopy method with excitation in the UV, visible, and near-IR ranges; the laser-conoscopy method; and the electron paramagnetic resonance-spectroscopy method. In optically uniaxial LiNbO3 crystals, a weak optical biaxiality has been revealed, which is attributed to an insignificant deformation of the optical indicatrix. This deformation can be caused both by the initial structural inhomogeneity of crystals and by the photorefractive effect. It has been shown that, under the action of light, charge exchange of copper cations Cu2+ ? Cu+ takes place in the crystal LiNbO3:Cu ([Cu] = 0.015 mas %). The LiNbO3:Cu crystal exhibits photorefractive properties not only because of the occurrence of intrinsic defects with electrons localized at them, as is the case with the LiNbO3stoich and LiNbO3congr crystals, but also due to the charge exchange of copper cations under the action of the laser radiation.

Sidorov, N. V.; Palatnikov, M. N.; Yanichev, A. A.; Gabain, A. A.; Pikoul, O. Yu.; Smirnov, A. N.

2013-10-01

162

Scanning angle Raman spectroscopy: Investigation of Raman scatter enhancement techniques for chemical analysis  

SciTech Connect

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.

Meyer, Matthew W. [Ames Laboratory

2013-03-14

163

Raman spectroscopy and polarization: Selected case studies  

NASA Astrophysics Data System (ADS)

We show, through several selected case studies, the potential benefits that can be obtained by controlling the polarization states of the exciting and scattered radiations in a Raman scattering experiment. When coupled with polarization control, Raman spectroscopy is thus capable of providing extra information on the structural properties of the materials under investigation. The experimental examples presented in this work are taken from the area of both conventional, i.e., far-field, as well as from near-field Raman spectroscopy. They cover topics such as the stress tensor measurement in strained semiconductor structures, the vibration mode assignment in pentacene thin films and the Raman scattering tensor determination from near-field measurements on azobenzene monolayers. The basic theory necessary for modelling the far- and near-field polarized Raman responses is also given and the model efficiency is illustrated on the experimental data.

Ossikovski, Razvigor; Picardi, Gennaro; Ndong, Gérald; Chaigneau, Marc

2012-10-01

164

Tunable infrared Raman laser using compressed hydrogen  

Microsoft Academic Search

Experiments were conducted on a laser which uses stimulated Raman scattering in compressed hydrogen at pressures of 50-60 atm, and a tunable neodymium laser as the pumping source. A raster focusing system together with an optical waveguide with a square cross section of 1 x 1 sq cm were used for the spatially homogeneous excitation of the Raman laser. Tunable

A. Z. Grasiuk; I. G. Zubarev; A. V. Kotov; S. I. Mikhailov; V. G. Smirnov

1976-01-01

165

Demonstration of a silicon Raman laser  

Microsoft Academic Search

We report the demonstration of the first silicon Raman laser. Experimentally, pulsed Raman laser emission at 1675 nm with 25 MHz repetition rate is demonstrated using a silicon waveguide as the gain medium. The laser has a clear threshold at 9 W peak pump pulse power and a slope efficiency of 8.5%.

Ozdal Boyraz; Bahram Jalali

2004-01-01

166

Standoff detection of explosive molecules using nanosecond gated Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Recently, improvised explosive device (IED) has been a serious threat for many countries. One of the approaches to alleviate this threat is standoff detection of explosive molecules used in IEDs. Raman spectroscopy is a prospective method among many technologies under research to achieve this goal. It provides unique information of the target materials, through which the ingredients used in IEDs can be analyzed and identified. The main problem of standoff Raman spectroscopic detection is the large background noise hindering weak Raman signals from the target samples. Typical background noise comes from both ambient fluorescent lights indoor and sunlight outdoor whose intensities are usually much larger than that of Raman scattering from the sample. Under the proper condition using pulse laser and ICCD camera with nanosecond pulse width and gating technology, we succeed to separate and remove these background noises from Raman signals. For this experiment, we build an optical system for standoff detection of explosive molecules. We use 532 nm, 10 Hz, Q-switching Nd:YAG laser as light source, and ICCD camera triggered by laser Qswitching time with proper gate delay regarding the flight time of Raman from target materials. Our detection system is successfully applied to detect and identify more than 20 ingredients of IEDs including TNT, RDX, and HMX which are located 10 to 54 meters away from the system.

Chung, Jin Hyuk; Cho, Soo Gyeong

2013-06-01

167

Emerging technology: applications of Raman spectroscopy for prostate cancer.  

PubMed

There is a need in prostate cancer diagnostics and research for a label-free imaging methodology that is nondestructive, rapid, objective, and uninfluenced by water. Raman spectroscopy provides a molecular signature, which can be scaled from micron-level regions of interest in cells to macroscopic areas of tissue. It can be used for applications ranging from in vivo or in vitro diagnostics to basic science laboratory testing. This work describes the fundamentals of Raman spectroscopy and complementary techniques including surface enhanced Raman scattering, resonance Raman spectroscopy, coherent anti-Stokes Raman spectroscopy, confocal Raman spectroscopy, stimulated Raman scattering, and spatially offset Raman spectroscopy. Clinical applications of Raman spectroscopy to prostate cancer will be discussed, including screening, biopsy, margin assessment, and monitoring of treatment efficacy. Laboratory applications including cell identification, culture monitoring, therapeutics development, and live imaging of cellular processes are discussed. Potential future avenues of research are described, with emphasis on multiplexing Raman spectroscopy with other modalities. PMID:24510129

Kast, Rachel E; Tucker, Stephanie C; Killian, Kevin; Trexler, Micaela; Honn, Kenneth V; Auner, Gregory W

2014-09-01

168

Surface vibrational spectroscopy using stimulated Raman scattering  

Microsoft Academic Search

We propose a new method for studying surface vibrational spectroscopy based on an extension of the picosecond stimulated Raman gain technique. This technique is extremely surface sensitive and can detect coverages of 1 percent of a monolayer. This technique does not require ultrahigh vacuums (as do electron spectroscopies), is an extremely sensitive probe of surface local fields, has very high

BARRY F. LEVINE; CHARLES V. SHANK; J. P. HERITAGE

1979-01-01

169

Titanium enhanced Raman microcavity laser  

NASA Astrophysics Data System (ADS)

Due to their long photon lifetimes, ultra high quality factor (Q) silica microcavities form an ideal platform for microlaser development. Previous work verified that these devices exhibit Raman lasing, because the high Q compensates for the low Raman gain of silica. However, only devices with Q>1E8 are able to achieve microwatt thresholds, limiting the application space. One approach for overcoming this barrier is to increase the inherent Raman gain of the material without degrading the optical performance of the device. To address this challenge, we synthesize a series of titanium (Ti) doped silica sol-gels with different concentrations of Ti, including a null. The refractive indices of the coatings are characterized using spectroscopic ellipsometry and increase linearly with the concentration of Ti from 1.44 to 1.51. We apply the sol-gel as a conformal coating on silica toroidal microcavities and characterize the basic cavity properties (Q) and the lasing behavior, including the lasing threshold and the slope efficiency. All measurements are performed in ambient conditions. Although the cavity Q's are modest (5E6), comparable lasing thresholds (microwatt) to higher Q silica devices are achieved because of the reduction in mode volume and the increase in Raman gain due to the presence of the Ti. Additionally, the efficiency of the laser increases with increasing Ti concentration.

Deka, Nishita; Maker, Ashley J.; Armani, Andrea M.

2014-03-01

170

Debris of potassium–magnesium silicate glass generated by femtosecond laser-induced ablation in air: An analysis by near edge X-ray absorption spectroscopy, micro Raman and energy dispersive X-ray spectroscopy  

NASA Astrophysics Data System (ADS)

The redeposited material (debris) resulting from ablation of a potassium-magnesium silicate glass upon scanning femtosecond laser pulse irradiation (130 fs, 800 nm) in air environment is investigated by means of three complementary surface analytical methods. Changes in the electronic band structure of the glass constituent Magnesium (Mg) were identified by X-ray Absorption Near Edge Structure spectroscopy (XANES) using synchrotron radiation. An up-shift of ?0.8 eV of a specific Magnesium K-edge absorption peak in the spectrum of the redeposited material along with a significant change in its leading edge position was detected. In contrast, the surface left after laser ablation exhibits a downshift of the peak position by ?0.9 eV. Both observations may be related to a change of the Mg coordinative state of the laser modified/redeposited glass material. The presence of carbon in the debris is revealed by micro Raman spectroscopy (?-RS) and was confirmed by energy dispersive X-ray spectroscopy (EDX). These observations are attributed to structural changes and chemical reactions taking place during the ablation process.

Grehn, M.; Seuthe, T.; Reinhardt, F.; Höfner, M.; Griga, N.; Eberstein, M.; Bonse, J.

2014-05-01

171

Raman spectroscopy characterization of actinide oxides (U 1-yPu y)O 2: Resistance to oxidation by the laser beam and examination of defects  

NASA Astrophysics Data System (ADS)

Structural changes in four (U 1-yPu y)O 2 materials with very different plutonium concentrations (0 ? y ? 1) and damage levels (up to 110 dpa) were studied by Raman spectroscopy. The novel experimental approach developed for this purpose consisted in using a laser beam as a heat source to assess the reactivity and structural changes of these materials according to the power supplied locally by the laser. The experiments were carried out in air and in water with or without hydrogen peroxide. As expected, the material response to oxidation in air depends on the plutonium content of the test oxide. At the highest power levels U 3O 8 generally forms with UO 2 whereas no significant change in the spectra indicating oxidation is observed for samples with high plutonium content ( 239PuO 2). Samples containing 25 wt.% plutonium exhibit intermediate behavior, typified mainly by a higher-intensity 632 cm -1 peak and the disappearance of the 1LO peak at 575 cm -1. This can be attributed to the presence of anion sublattice defects without any formation of higher oxides. The range of materials examined also allowed us to distinguish partly the chemical effects of alpha self-irradiation. The results obtained with water and hydrogen peroxide (a water radiolysis product) on a severely damaged 238PuO 2 specimen highlight a specific behavior, observed for the first time.

Jégou, C.; Caraballo, R.; Peuget, S.; Roudil, D.; Desgranges, L.; Magnin, M.

2010-10-01

172

Cone penetrometer fiber optic raman spectroscopy probe assembly  

DOEpatents

A chemically and mechanically robust optical Raman spectroscopy probe assembly that can be incorporated in a cone penetrometer (CPT) for subsurface deployment. This assembly consists of an optical Raman probe and a penetrometer compatible optical probe housing. The probe is intended for in-situ chemical analysis of chemical constituents in the surrounding environment. The probe is optically linked via fiber optics to the light source and the detection system at the surface. A built-in broadband light source provides a strobe method for direct measurement of sample optical density. A mechanically stable sapphire window is sealed directly into the side-wall of the housing using a metallic, chemically resistant, hermetic seal design. This window permits transmission of the interrogation light beam and the resultant signal. The spectroscopy probe assembly is capable of accepting Raman, Laser induced Fluorescence, reflectance, and other optical probes with collimated output for CPT deployment.

Kyle, Kevin R. (Brentwood, CA); Brown, Steven B. (Livermore, CA)

2000-01-01

173

In Situ Quantitative Analysis of Individual H2O-CO2 Fluid Inclusions by Laser Raman Spectroscopy  

NASA Astrophysics Data System (ADS)

Carbon dioxide-bearing aqueous fluids are common in metamorphic environments, and the relative amount of carbon dioxide in the fluid may have a significant effect on phase equilibria. For example, at a given pressure, the temperature at which calcite + quartz + wollastonite are in equilibrium may vary by several 100 degrees Celsius, depending on the fluid composition. Similarly, CO2-bearing fluids are important in many ore- forming systems where boiling and fluid immiscibility are associated with ore deposition. Previously there has been no direct way to determine the H2O/CO2 ratio in individual fluid inclusions. Here we describe a technique based on Raman spectroscopy that may be applied to determine compositions of individual carbon dioxide-bearing fluid inclusions. -Synthetic H2O-CO2 fluid inclusions containing 2.5 to 50 mole% CO2 were used to develop an empirical calibration curve based on the relationship between the Raman peaks for CO2 (1388 cm- 1) and H2O at (3660 cm-1) and composition. The peak intensity ratio (IR = I CO2/ (I CO2 + I H2O)) is related to the mole percent CO2 in the inclusion according to the relation: Mole % CO2 = e -3.959 IRsquared + 8.0734 IR where ICO2 is the intensity of the 1388 cm-1 peak and IH2O is the intensity of the 3660 cm- 1 peak. The relationship between peak intensity and composition is valid at 350°C for compositions from 2.5 to 50 mole % CO2. The peak area ratio is defined as AR = ACO2 / (A CO2 + A H2O), where A CO2 is the integrated area under the 1388 cm-1 peak and AH2O is the integrated area under the 3660 cm-1 peak. The relationship between peak area (AR) ratio and the CO2 concentration in the inclusions is given as: Mole % CO2 = 312.5 AR The peak area ratio calibration is valid for concentrations between 2.5 and 25 mole % and from 300 to 450°C. The calibration based on the peak intensity ratios has a smaller statistical error than the one based on integrated peak area ratios. Analyses of 12.5 mole % CO2 fluid inclusions over the range 307 to 450°C suggest that CO2-"H2O peak intensity ratios are a negative function of temperature, whereas peak area ratios are essentially constant over this temperature range. The technique has been applied to natural low-salinity CO2-"H2O inclusions from the Butte, Montana, porphyry copper-molybdenum deposit. Carbon dioxide concentrations obtained (3 to 7 mole % CO2-") are in good agreement with concentrations based on microthermometric and petrographic observations.

Azbej, T.; Severs, M. J.; Rusk, B. G.; Bodnar, R. J.

2006-05-01

174

Multiplex coherent raman spectroscopy detector and method  

NASA Technical Reports Server (NTRS)

A multiplex coherent Raman spectrometer (10) and spectroscopy method rapidly detects and identifies individual components of a chemical mixture separated by a separation technique, such as gas chromatography. The spectrometer (10) and method accurately identify a variety of compounds because they produce the entire gas phase vibrational Raman spectrum of the unknown gas. This is accomplished by tilting a Raman cell (20) to produce a high-intensity, backward-stimulated, coherent Raman beam of 683 nm, which drives a degenerate optical parametric oscillator (28) to produce a broadband beam of 1100-1700 nm covering a range of more than 3000 wavenumber. This broadband beam is combined with a narrowband beam of 532 nm having a bandwidth of 0.003 wavenumbers and focused into a heated windowless cell (38) that receives gases separated by a gas chromatograph (40). The Raman radiation scattered from these gases is filtered and sent to a monochromator (50) with multichannel detection.

Chen, Peter (Inventor); Joyner, Candace C. (Inventor); Patrick, Sheena T. (Inventor); Guyer, Dean R. (Inventor)

2004-01-01

175

Serial Raman spectroscopy of particles trapped on a waveguide.  

PubMed

We demonstrate that Raman spectroscopy can be used to characterize and identify particles that are trapped and propelled along optical waveguides. To accomplish this, microscopic particles on a waveguide are moved along the waveguide and then individually addressed by a focused laser beam to obtain their characteristic Raman signature within 1 second acquisition time. The spectrum is used to distinguish between glass and polystyrene particles. After the characterization, the particles continue to be propelled along the straight waveguide. Alternatively, a waveguide loop with a gap is also investigated, and in this case particles are held in the gap for characterization before they are released. PMID:23481754

Lřvhaugen, Pĺl; Ahluwalia, Balpreet Singh; Huser, Thomas R; Hellesř, Olav Gaute

2013-02-11

176

The Micro Raman Spectroscopy for Analysis of the Gypsum Dehydration by Simulated Space Weathering  

NASA Astrophysics Data System (ADS)

Herein, a simulated space weathering of hydrated sulfates (gypsum, CaSO_4.2H_20) by CO_2 low temperature plasma was reported. Gypsum dehydration is a significant process of weathering analyzed by micro-laser Raman spectroscopy.

Wu, Z. C.; Ni, Y. H.; Ling, Z. C.; Wu, H.

2014-06-01

177

Solid state lasers with Raman frequency conversion  

Microsoft Academic Search

Stimulated Raman scattering (SRS) in solid state crystals has become a well-established nonlinear frequency conversion technique with the increasing number of applications. Summary of an experimental investigation of SRS in unique solid state Raman-active materials (BaWO4, KGW, CaCO3) is presented. Examples of picosecond and nanosecond Raman laser development are described in various pump configurations. Comparison of Raman crystal converters is

Helena Jel??nková; Peter G Zverev; Tasoltan T Basiev

2004-01-01

178

UV Raman spectroscopy of hydrocarbons.  

PubMed

In this paper, the UV Raman spectra of a large number of saturated and alkyl-substituted monocyclic, bicyclic and polycyclic aromatic hydrocarbons are obtained at 220 and 233 nm excitation wavelengths. Also included are nitrogen- and sulphur-containing hydrocarbons. The spectra obtained are fluorescence free, even for such highly fluorescent compounds as perylene, consistent with earlier reports of UV Raman spectra of hydrocarbons. The hydrocarbon UV Raman spectra exhibit greatly improved signal-to-noise ratio when in the neat liquid or solution state compared with the neat solid state, suggesting that some surface degradation occurs under the conditions used here. Assignments are given for most of the bands and clear marker bands for the different classes of hydrocarbons are readily observable, although their relative intensities vary greatly. These results are discussed in the context of structure and symmetry to develop a consistent, molecular-based model of vibrational group frequencies. PMID:15482987

Loppnow, G R; Shoute, L; Schmidt, K J; Savage, A; Hall, R H; Bulmer, J T

2004-11-15

179

Two-frequency fibre Raman laser  

SciTech Connect

A new scheme of a fibre Raman laser emitting at two wavelengths is proposed. The scheme uses a one-stage Raman converter with the output Bragg grating with the reflectivity above 99%. Lasing at two wavelengths is achieved due to the overlap of the output emission spectrum with the reflection spectrum of the output Bragg grating. (lasers)

Paramonov, Vladimir M; Kurkov, Andrei S; Medvedkov, O I; Grukh, Dmitrii A; Dianov, Evgenii M [Fiber Optics Research Center, Russian Academy of Sciences, Moscow (Russian Federation)

2004-03-31

180

Shock Tube Diagnostics Utilizing Laser Raman Scattering  

Microsoft Academic Search

With the development of high power lasers, the use of various light scattering techniques has gained acceptance as a diagnostic tool for flowfield analysis. One of the most versatile of these is the spontaneous Raman technique, since by its use the thermodynamic properties of several different species may be measured simultaneously. The application of the spontaneous laser Raman technique in

Joseph W. Glaser

1982-01-01

181

Coherent Raman spectroscopy for supersonic flow measurments  

NASA Technical Reports Server (NTRS)

In collaboration with NASA/Langley Research Center, a truly nonintrusive and nonseeding method for measuring supersonic molecular flow parameters was proposed and developed at Colorado State University. The feasibility of this Raman Doppler Velocimetry (RDV), currently operated in a scanning mode, was demonstrated not only in a laboratory environment at Colorado State University, but also in a major wind tunnel at NASA/Langley Research Center. The research progress of the RDV development is summarized. In addition, methods of coherent Rayleigh-Brillouin spectroscopy and single-pulse coherent Raman spectroscopy are investigated, respectively, for measurements of high-pressure and turbulent flows.

She, C. Y.

1986-01-01

182

Applications of Raman spectroscopy to library heritage.  

PubMed

This work reports some different applications of Raman spectroscopy, a high sensitive non-destructive technique, to the conservation of Library Heritage. By Raman spectroscopy we were able to detect the chemical mechanisms leading to cellulose degradation, identifying the different functional groups formed during the paper ageing. This kind of information is fundamental to choose a suited restoration treatment. A second reported application is the identification of pigments used to decorate paper and parchments. We report some results obtained from analysis of a XV and a XIII century illuminations. PMID:11836947

Bicchieri, M; Nardone, M; Sodo, A

2001-01-01

183

Raman spectroscopy and Raman imaging for early detection of cancer  

NASA Astrophysics Data System (ADS)

Raman spectroscopy is a powerful technique as it provides fundamental information about vibrational modes of a system. Eigenvalues of these modes are very sensitive to the strength of the chemical bonds and perturbations caused by the environment, particularly charge distribution and alterations in the dipole strength of the system. All these parameters are profoundly modified during the tumor formation process nad hence Raman technique could be a unique and also a direct approach for evaluating tumor genesis at early stages. for this pupose the present investigation was carried out. We used cultured wild type and c-ras transformed NIH 3T3 fibroblast. The samples were treated with methyl alcohol solution ina conventional manner and then Raman spectra nad images were obtained by a specially developed confocal Raman microscope. The present results reveal differences between both cell types in the spectral details as well as in the morphology. Raman images are able to detect the exact site where cancer-related changes have taken place. These results clearly indicate the superiority of the present technique over conventional methods such as images obtained by X-rays or Nuclear Magnetic Resonance (NMR). Moreover, unlike other approaches, Raman images detect alterations at the submicron level rather than in the centimeter or millimeter range. Being an optical method it can be applied in vivo as a non-invasive technique potentially useful to early detection of cancer (particularly easy accessible cancers such as those of the skin and the digestive tract). The obtained resulsts suggest the great potential of Raman imaging in premature clinical diagnostic approaches.

Joshi, Narahari V.; Ortega, Angel; Estrela, Jose Maria

2004-06-01

184

Normal and Stimulated Raman Spectroscopy.  

National Technical Information Service (NTIS)

The report is in three parts: (1) gives a detailed account of experiments on the angular dependence of stimulated Raman emission in diamond. The observed cone angles of Stokes and anti-Stokes radiation produced by incident parallel light agree with the mo...

B. O. Stoicheff F. Shimizu A. K. McQuillan W. Clements U. Bachmann

1967-01-01

185

Assessment of bone healing on tibial fractures treated with wire osteosynthesis associated or not with infrared laser light and biphasic ceramic bone graft (HATCP) and guided bone regeneration (GBR): Raman spectroscopy study  

Microsoft Academic Search

The aim of this study was to evaluate, through Raman spectroscopy, the repair of complete tibial fracture in rabbits fixed with wire osteosynthesis - WO, treated or not with infrared laser light (lambda 780nm, 50mW, CW) associated or not to the use of HATCP and GBR. Surgical fractures were created under general anesthesia (Ketamine 0.4ml\\/Kg IP and Xilazine 0.2ml\\/Kg IP),

Fabíola Bastos de Carvalho; Gilberth Tadeu S. Aciole; Jouber Mateus S. Aciole; Landulfo Silveira Jr.; Jean Nunes Dos Santos; Antônio L. B. Pinheiro

2011-01-01

186

Experimental demonstration of mode-selective phonon excitation of 6H-SiC by a mid-infrared laser with anti-Stokes Raman scattering spectroscopy  

SciTech Connect

Mode-selective phonon excitation by a mid-infrared laser (MIR-FEL) is demonstrated via anti-Stokes Raman scattering measurements of 6H-silicon carbide (SiC). Irradiation of SiC with MIR-FEL and a Nd-YAG laser at 14 K produced a peak where the Raman shift corresponds to a photon energy of 119 meV (10.4 ?m). This phenomenon is induced by mode-selective phonon excitation through the irradiation of MIR-FEL, whose photon energy corresponds to the photon-absorption of a particular phonon mode.

Yoshida, Kyohei; Hachiya, Kan; Okumura, Kensuke; Mishima, Kenta; Inukai, Motoharu; Torgasin, Konstantin; Omer, Mohamed [Graduate School of Energy Science, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-8501 (Japan)] [Graduate School of Energy Science, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-8501 (Japan); Sonobe, Taro [Kyoto University Research Administration Office, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-8501 (Japan)] [Kyoto University Research Administration Office, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-8501 (Japan); Zen, Heishun; Negm, Hani; Kii, Toshiteru; Masuda, Kai; Ohgaki, Hideaki [Institute of Advanced Energy, Kyoto University, Gokasyo, Uji, Kyoto 611-0011 (Japan)] [Institute of Advanced Energy, Kyoto University, Gokasyo, Uji, Kyoto 611-0011 (Japan)

2013-10-28

187

Measuring Rocket Engine Temperatures with Hydrogen Raman Spectroscopy  

NASA Technical Reports Server (NTRS)

Optically accessible, high pressure, hot fire test articles are available at NASA Marshall for use in development of advanced rocket engine propellant injectors. Single laser-pulse ultraviolet (UV) Raman spectroscopy has been used in the past in these devices for analysis of high pressure H2- and CH4-fueled combustion, but relies on an independent pressure measurement in order to provide temperature information. A variation of UV Raman (High Resolution Hydrogen Raman Spectroscopy) is under development and will allow temperature measurement without the need for an independent pressure measurement, useful for flows where local pressure may not be accurately known. The technique involves the use of a spectrometer with good spectral resolution, requiring a small entrance slit for the spectrometer. The H2 Raman spectrum, when created by a narrow linewidth laser source and obtained from a good spectral resolution spectrograph, has a spectral shape related to temperature. By best-fit matching an experimental spectrum to theoretical spectra at various temperatures, a temperature measurement is obtained. The spectral model accounts for collisional narrowing, collisional broadening, Doppler broadening, and collisional line shifting of each Raman line making up the H2 Stokes vibrational Q-branch spectrum. At pressures from atmospheric up to those associated with advanced preburner components (5500 psia), collisional broadening though present does not cause significant overlap of the Raman lines, allowing high resolution H2 Raman to be used for temperature measurements in plumes and in high pressure test articles. Experimental demonstrations of the technique are performed for rich H2-air flames at atmospheric pressure and for high pressure, 300 K H2-He mixtures. Spectrometer imaging quality is identified as being critical for successful implementation of technique.

Wehrmeyer, Joseph A.; Osborne, Robin J.; Trinh, Huu P.; Turner, James (Technical Monitor)

2001-01-01

188

Pharmaceutical applications of Mid-IR and Raman spectroscopy.  

PubMed

Mid-IR and Raman spectroscopy are versatile tools in pharmaceutics and biopharmaceutics, with a wide field of applications ranging from characterization of drug formulations to elucidation of kinetic processes in drug delivery. After an introduction to the basic principles of IR and Raman spectroscopy, new developments in applications of these methods for studying drug delivery systems, in particular topical drug delivery, will be reviewed. FTIR-ATR is a well-established standard method used to study drug release in semisolid formulations, drug penetration, and influence of penetration modifiers; it is also capable of in vivo studies. FTIR-PAS has been applied to measure drug content in semisolid and solid formulations, to determine drug penetration into artificial and biological membranes. The big advantage of this technique is the possibility of spectral depth profiling. However, FTIR-PAS is so far limited to in vitro investigations. Raman spectroscopy can be used to characterize the structure of colloidal drug carrier systems. Raman spectroscopy is readily applicable to in vivo studies, but such investigations must fulfill the relevant laser safety guideline. Recently, there has been tremendous technical improvement in vibrational microspectroscopy. FTIR imaging shows great promise in its ability to visualize the drug and excipient distribution in pharmaceutical formulations such as tablets and therapeutic transdermal systems, as well as to reveal the mechanism of drug release. Furthermore, this unique technique offers completely new possibilities to study the lateral diffusion of drugs. PMID:15885850

Wartewig, Siegfried; Neubert, Reinhard H H

2005-06-15

189

Characterizing Shock Metamorphism in Feldspar Using Micro-Raman Spectroscopy  

NASA Astrophysics Data System (ADS)

Here we present preliminary results from our work to use micro-Raman spectroscopy as a tool for refining shock classification schemes. Micro-Raman spectroscopy may provide higher pressure resolution than traditional petrographic techniques.

Jaret, S. J.; Glotch, T. D.; Johnson, J. R.

2014-06-01

190

Combustion Diagnostics Using Laser Spontaneous-Raman Scattering.  

National Technical Information Service (NTIS)

An existing computer-controlled Raman Spectroscopy system, using a pulsed nitrogen laser and a double spectrometer, was upgraded and used to measure the temperatures in the combustion plume of an afterburning J85-5 turbojet engine. The computer-fitted tem...

P. P. Yaney

1979-01-01

191

Gold-decorated titania nanotube arrays as dual-functional platform for surface-enhanced Raman spectroscopy and surface-assisted laser desorption/ionization mass spectrometry.  

PubMed

In this report, we demonstrate gold-decorated titania nanotube arrays (Au-TNA substrate) as a dual-functional platform for surface-enhanced Raman spectroscopy (SERS) and surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). The Au nanoparticles are grown on the substrate using vapor deposition of Au. The resulting substrates perform better than Au colloids in terms of the reproducibility of the SERS measurements, long-term stability of the fabricated structures, and clean surface of the Au. The nanostructure of the Au-TNA substrate was designed to optimize the SALDI-MS and SERS performance. Excellent reproducibility of the SERS measurements using the Au-TNA substrate was obtained, with a standard error less than 6 %. SALDI activity was also demonstrated for the same Au-TNA substrates. Finally, the Au-TNA substrate was used for combined SERS and SALDI-MS analysis (i) to discriminate the structural isomers of pyridine compounds (para-, meta-, and ortho-pyridinecarboxylic acid) and (ii) to detect polycarbamate, a dithiocarbamate fungicide. These results are difficult to obtain using either approach alone. PMID:24731133

Nitta, Syuhei; Yamamoto, Atsushi; Kurita, Masahiro; Arakawa, Ryuichi; Kawasaki, Hideya

2014-06-11

192

Raman spectroscopy of newberyite, hannayite and struvite  

NASA Astrophysics Data System (ADS)

The phosphate minerals hannayite, newberyite and struvite have been studied by Raman spectroscopy using a thermal stage. Hannayite and newberyite are characterised by an intense band at around 980 cm -1 assigned to the v symmetric stretching vibration of the HPO 4 units. In contrast the symmetric stretching mode is observed at 942 cm -1 for struvite. The Raman spectra are characterised by multiple v anti-symmetric stretching bands and v and v bending modes indicating strong distortion of the HPO 4 and PO 4 units. Hannayite and newberyite are defined by bands at 3382 and 3350 cm -1 attributed to HOPO 3 vibrations and hannayite and struvite by bands at 2990, 2973 and 2874 assigned to NH 4+ bands. Raman spectroscopy has proven most useful for the analysis of these 'cave' minerals where complex paragenetic relationships exist between the minerals.

Frost, Ray L.; Weier, Matt L.; Martens, Wayde N.; Henry, Dermot A.; Mills, Stuart J.

2005-11-01

193

Application of Raman Spectroscopy and Surface-Enhanced Raman Scattering to the Analysis of Synthetic Dyes Found in Ballpoint Pen Inks  

Microsoft Academic Search

The applicability of Raman spectroscopy and surface-enhanced Raman scattering (SERS) to the analysis of synthetic dyes com- monly found in ballpoint inks was investigated in a comparative study. Spectra of 10 dyes were obtained using a dispersive system (633 nm, 785 nm lasers) and a Fourier transform system (1064 nm laser) under different analytical conditions (e.g., powdered pigments, solutions, thin

Irina Geiman; Marco Leona; John R. Lombardi

2009-01-01

194

Raman spectroscopy of blue gel pen inks  

Microsoft Academic Search

Raman spectroscopy is becoming a tool of major importance in forensic science. It is a non-invasive, non-destructive analytical method allowing samples to be examined without any preparation. This paper demonstrates the use of the technique as a general tool for gel pen inks analysis. For this purpose, 55 blue gel pen inks, of different brands and models representative of gel

Williams David Mazzella; Patrick Buzzini

2005-01-01

195

Three-wavelength Raman fiber laser with reliable dynamic control  

Microsoft Academic Search

We present a novel concept for a multiwavelength Raman fiber laser based on a chain of Raman cavities. This Raman laser has efficient power control for all generated wavelengths in a large dynamic range.

A. A. Demidov; A. N. Starodumov; X. Li; A. Martinez-Rios; H. Po

2003-01-01

196

Micro-Raman spectroscopy on oral tissues  

NASA Astrophysics Data System (ADS)

Micro-Raman Spectroscopy (?-RS) provides a unique tool in medicine for a not invasive and real time analysis of biological tissue for biopsy and "in vivo" investigation. Based on the evaluation of molecular vibration frequencies, the ?-RS is able to detect the main molecular bonds of protein constituents, as the C-H and C-C ones. Changes in frequency or in the relative intensity of the vibration modes revealed by ?-RS can be related to changes of chemical bond and of protein structure induced by pathology. The ?-RS has been performed on samples of oral tissue from informed patients, affected by pemphigus vulgaris (an oral pathology) in an advanced regression state. The biopsies were thin slices (about 1mm thick) with 6mm diameter. The sample was measured through a 170 ?m thick cover-glass. The experimental set-up was mainly composed by a He-Ne laser and a monochromator equipped with a Peltier cell and with a grating of 1800 grooves/mm. The laser light was focused on the sample surface by means of a long focal length 50X optical objective. The main protein bonds are clearly detectable in the considered samples and this give important information on the integrity and on the state of tissue components (lipids and proteins), and consequently on the occurrence of pathology. The potential application of this method for in vivo analysis is an invaluable alternative to biopsy and pathological examinations for many medical application as screening diagnostic, therapy progress examination, and surgical support.

Zenone, F.; Lepore, M.; Perna, G.; Carmone, P.; Riccio, R.; Gaeta, G. M.; Capozzi, V.

2006-03-01

197

Spatially offset Raman spectroscopy (SORS) for liquid screening  

NASA Astrophysics Data System (ADS)

Recently, Spatially Offset Raman Spectroscopy (SORS) has been discussed as a novel method for the screening of liquids, aerosols and gels (LAGs) at airports and for other security applications. SORS is an optical spectroscopic method which enables the precise chemical identification of substances from a reference list and, due to the rich spectral information, has an inherently high probability of detection and low false alarm rate. The method is generally capable of screening substances inside non-metallic containers such as plastic and glass bottles. SORS is typically successful through opaque plastic and coloured glass, which are often challenging for conventional backscatter Raman spectroscopy. SORS is performed in just a few seconds by shining a laser light onto the container and then measuring the Raman signal at the excitation point but also at one or more offset positions. Each measurement has different relative orthogonal contributions from the container and contents Raman spectra, so that, with no prior knowledge, the pure Raman spectra of both the container and contents can be extracted - either by scaled subtraction or via multivariate statistical methods in an automated process. In this paper, the latest results will be described from a prototype SORS device designed for aviation security and the advantages and limitations of SORS will be discussed.

Loeffen, Paul W.; Maskall, Guy; Bonthron, Stuart; Bloomfield, Matthew; Tombling, Craig; Matousek, Pavel

2011-10-01

198

Optical Coherence Tomography and Raman Spectroscopy of the retina  

SciTech Connect

Imaging the structure and correlating it with the biochemical content of the retina holds promise for fundamental research and for clinical applications. Optical coherence tomography (OCT) is commonly used to image the 3D structure of the retina and while the added functionality of biochemical analysis afforded by Raman scattering could provide critical molecular signatures for clinicians and researchers, there are many technical challenges to combining these imaging modalities. We present an ex vivo OCT microscope combined with Raman spectroscopy capable of collecting morphological and molecular information about a sample simultaneously. The combined instrument will be used to investigate remaining technical challenges to combine these imaging modalities, such as the laser power levels needed to achieve a Raman signal above the noise level without damaging the sample.

Evans, J W; Zawadzki, R J; Liu, R; Chan, J; Lane, S; Werner, J S

2009-01-16

199

FT-Raman spectroscopy study of human breast tissue  

NASA Astrophysics Data System (ADS)

Optical spectroscopy has been extensively studied as a potential in vivo diagnostic tool to provide information about the chemical and morphologic structure of tissue. Raman Spectroscpy is an inelastic scattering process that can provide a wealth of spectral features that can be related to the specific molecular structure of the sample. This article reports results of an in vitro study of the FT-Raman human breast tissue spectra. An Nd:YAG laser at 1064nm was used as the excitation source in the FT-Raman Spectrometer. The neoplastic human breast samples, both Fibroadenoma and ICD, were obtained during therapeutical routine medical procedures required by the primary disease, and the non-diseased human tissue was obtained in plastic surgery. No sample preparation was needed for the FT-Raman spectra collection. The FT-Raman spectra were recorded from normal, benign (Fibroadenomas) and malignant (IDC-Intraductal Carcinoma) samples, adding up 51 different areas. The main spectral differences of a typical FT-Raman spectra of a Normal (Non-diseased), Fibroadenoma, and Infiltrating Ductal Carcinoma (IDC) breast tissue at the interval of 600 to 1800cm-1, which may differentiate diagnostically the sample, were found in the bands of 1230 to 1295cm-1, 1440 to 1460 cm-1 and 1650 to 1680 cm-1, assigned to the vibrational bands of the carbohydrate-amide III, proteins and lipids, and carbohydrate-amide I, respectively.

Bitar Carter, Renata A.; Martin, Airton A.; Netto, Mario M.; Soares, Fernando A.

2004-07-01

200

Prospects of Mid Infrared Silicon Raman Laser  

NASA Astrophysics Data System (ADS)

Mid wave infrared (MWIR) lasers in the wavelength range of 2-5?m form an important tool for free space communications, bio-chemical detection and certain medical applications. Most organic chemicals and biological agents have unique signatures in the MWIR and can be detected using these lasers. The strong water absorption peak at 2.9?m renders such a laser attractive for surgery and dentistry. Solid state lasers comprising OPO-based nonlinear frequency converters and Raman lasers have been the popular choice for these applications. However, the low damage threshold, poor thermal conductivity and high cost limit the commercial availability of these sources. The recent demonstration of the first silicon Raman laser in 2004 combined with excellent transmission of silicon in the mid-IR suggests that silicon should be considered as a MWIR Raman crystal. In the near IR, where current silicon Raman lasers operate, free carriers that are generated by two photon absorption (TPA) create severe losses. TPA vanishes in the MWIR regime (? > 2.25?m), hence eliminating the main problem with silicon Raman lasers. This combined with (i) the unsurpassed quality of commercial silicon crystals, (ii) the low cost and wide availability of the material, (iii) extremely high optical damage threshold of 1-4 GW/cm2 (depending on the crystal resistivity), and (iv) excellent thermal conductivity renders silicon a very attractive Raman crystal. Moreover, integrated waveguide and resonator technologies can lead to device miniaturization. This talk discusses the MWIR silicon laser and its applications.

Jalali, Bahram

2006-03-01

201

Development of a drug assay using surface-enhanced Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Surface-enhanced Raman spectroscopy has been used to detect low levels of several chemical compounds, including the drugs of abuse -cocaine hydrochloride and methamphetamme hydrochloride. Raman spectra of these substances have also been taken over optical fibers using red-wavelength excitation. These measurements demonstrate the feasibility of the remote determination of various target chemicals using diode laser excitation and diode array detection.

Angel, S. M.; Roe, Jeffrey N.; Andresen, Brian D.; Myrick, Michael L.; Milanovich, Fred P.

1990-07-01

202

Detection Of Biochips By Raman And Surface Enhanced Raman Spectroscopies  

NASA Astrophysics Data System (ADS)

Biochips constitute a rapidly increasing research field driven by the versatility of sensing devices and the importance of their applications in the bioanalytical field, drug development, environmental monitoring, food analysis, etc. Common strategies used for creating biochips and for reading them have extensive limitations, motivating development of miniature biochips and label-free formats. To achieve these goals we combined the nano fountain pen method, for printing microscale features with Raman spectroscopy or surface enhanced Raman spectroscopy (SERS) for reading droplets of synthetic receptors. These receptors include molecularly imprinted polymers (MIPs), which are obtained by polymerization of suitable functional and cross-linking monomers around molecular templates. MIPs are characterized by higher physical and chemical stability than biomacromolecules, and therefore are potentially very suitable as recognition elements for biosensors, or biochips. The monitored bands in the Raman and SERS spectra could be related to the taken up compound, allowing direct detection of the template, i.e., the ?-blocking drug propranolol in the imprinted droplets, as well as imaging of individual and multiple dots in an array. This study shows that the combination of nanolithography techniques with SERS might open the possibility of miniaturized arrayed MIP sensors with label-free, specific and quantitative detection.

Kantarovich, Keren; Tsarfati, Inbal; Gheber, Levi A.; Haupt, Karsten; Bar, Ilana

2010-08-01

203

Raman spectroscopy of shocked water  

SciTech Connect

We describe a new technique for recording spontaneous Raman spectra from molecules during the passage of strong shock waves. We have used this technique to study the OH-stretch band of liquid H/sub 2/O shocked to pressure up to 26 GPa and 1700 K. The shape of the band changes over the range 7.5-26 GPa, and is described well by a two-component mixture model, implying changes in the intermolecular coupling of shock compressed water molecules. We discuss the implications of the spectra on the mechanism responsible for the electrical conductivity of shocked H/sub 2/O. 22 refs., 7 figs., 2 tabs.

Holmes, N.C.; Nellis, W.J.; Graham, W.B.; Walrafen, G.E.

1985-08-01

204

Coherent Raman spectro-imaging with laser frequency combs  

NASA Astrophysics Data System (ADS)

Advances in optical spectroscopy and microscopy have had a profound impact throughout the physical, chemical and biological sciences. One example is coherent Raman spectroscopy, a versatile technique interrogating vibrational transitions in molecules. It offers high spatial resolution and three-dimensional sectioning capabilities that make it a label-free tool for the non-destructive and chemically selective probing of complex systems. Indeed, single-colour Raman bands have been imaged in biological tissue at video rates by using ultra-short-pulse lasers. However, identifying multiple, and possibly unknown, molecules requires broad spectral bandwidth and high resolution. Moderate spectral spans combined with high-speed acquisition are now within reach using multichannel detection or frequency-swept laser beams. Laser frequency combs are finding increasing use for broadband molecular linear absorption spectroscopy. Here we show, by exploring their potential for nonlinear spectroscopy, that they can be harnessed for coherent anti-Stokes Raman spectroscopy and spectro-imaging. The method uses two combs and can simultaneously measure, on the microsecond timescale, all spectral elements over a wide bandwidth and with high resolution on a single photodetector. Although the overall measurement time in our proof-of-principle experiments is limited by the waiting times between successive spectral acquisitions, this limitation can be overcome with further system development. We therefore expect that our approach of using laser frequency combs will not only enable new applications for nonlinear microscopy but also benefit other nonlinear spectroscopic techniques.

Ideguchi, Takuro; Holzner, Simon; Bernhardt, Birgitta; Guelachvili, Guy; Picqué, Nathalie; Hänsch, Theodor W.

2013-10-01

205

Coherent Raman spectro-imaging with laser frequency combs.  

PubMed

Advances in optical spectroscopy and microscopy have had a profound impact throughout the physical, chemical and biological sciences. One example is coherent Raman spectroscopy, a versatile technique interrogating vibrational transitions in molecules. It offers high spatial resolution and three-dimensional sectioning capabilities that make it a label-free tool for the non-destructive and chemically selective probing of complex systems. Indeed, single-colour Raman bands have been imaged in biological tissue at video rates by using ultra-short-pulse lasers. However, identifying multiple, and possibly unknown, molecules requires broad spectral bandwidth and high resolution. Moderate spectral spans combined with high-speed acquisition are now within reach using multichannel detection or frequency-swept laser beams. Laser frequency combs are finding increasing use for broadband molecular linear absorption spectroscopy. Here we show, by exploring their potential for nonlinear spectroscopy, that they can be harnessed for coherent anti-Stokes Raman spectroscopy and spectro-imaging. The method uses two combs and can simultaneously measure, on the microsecond timescale, all spectral elements over a wide bandwidth and with high resolution on a single photodetector. Although the overall measurement time in our proof-of-principle experiments is limited by the waiting times between successive spectral acquisitions, this limitation can be overcome with further system development. We therefore expect that our approach of using laser frequency combs will not only enable new applications for nonlinear microscopy but also benefit other nonlinear spectroscopic techniques. PMID:24132293

Ideguchi, Takuro; Holzner, Simon; Bernhardt, Birgitta; Guelachvili, Guy; Picqué, Nathalie; Hänsch, Theodor W

2013-10-17

206

Assessment of bone healing on tibial fractures treated with wire osteosynthesis associated or not with infrared laser light and biphasic ceramic bone graft (HATCP) and guided bone regeneration (GBR): Raman spectroscopy study  

NASA Astrophysics Data System (ADS)

The aim of this study was to evaluate, through Raman spectroscopy, the repair of complete tibial fracture in rabbits fixed with wire osteosynthesis - WO, treated or not with infrared laser light (? 780nm, 50mW, CW) associated or not to the use of HATCP and GBR. Surgical fractures were created under general anesthesia (Ketamine 0.4ml/Kg IP and Xilazine 0.2ml/Kg IP), on the tibia of 15 rabbits that were divided into 5 groups and maintained on individual cages, at day/night cycle, fed with solid laboratory pelted diet and had water ad libidum. On groups II, III, IV and V the fracture was fixed with WO. Animals of groups III and V were grafted with hydroxyapatite + GBR technique. Animals of groups IV and V were irradiated at every other day during two weeks (16J/cm2, 4 x 4J/cm2). Observation time was that of 30 days. After animal death the specimens were kept in liquid nitrogen for further analysis by Raman spectroscopy. Raman spectroscopy showed significant differences between groups (p<0.001). It is concluded that IR laser light was able to accelerate fracture healing and the association with HATCP and GBR resulted on increased deposition of calcium hydroxyapatite.

Bastos de Carvalho, Fabíola; Aciole, Gilberth Tadeu S.; Aciole, Jouber Mateus S.; Silveira, Landulfo, Jr.; Nunes Dos Santos, Jean; Pinheiro, Antônio L. B.

2011-02-01

207

Detection of liquid hazardous molecules using linearly focused Raman spectroscopy  

NASA Astrophysics Data System (ADS)

In security, it is an important issue to analyze hazardous materials in sealed bottles. Particularly, prompt nondestructive checking of sealed liquid bottles in a very short time at the checkpoints of crowded malls, stadiums, or airports is of particular importance to prevent probable terrorist attack using liquid explosives. Aiming to design and fabricate a detector for liquid explosives, we have used linearly focused Raman spectroscopy to analyze liquid materials in transparent or semi-transparent bottles without opening their caps. Continuous lasers with 532 nm wavelength and 58 mW/130 mW beam energy have been used for the Raman spectroscopy. Various hazardous materials including flammable liquids and explosive materials have successfully been distinguished and identified within a couple of seconds. We believe that our technique will be one of suitable methods for fast screening of liquid materials in sealed bottles.

Cho, Soo Gyeong; Chung, Jin Hyuk

2013-05-01

208

UV gated Raman spectroscopy for standoff detection of explosives  

NASA Astrophysics Data System (ADS)

Real-time detection and identification of explosives at a standoff distance is a major issue in efforts to develop defense against so-called improvised explosive devices (IED). It is recognized that the only method, which is potentially capable to standoff detection of minimal amounts of explosives is laser-based spectroscopy. LDS technique belongs to trace detection, namely to its micro-particles variety. It is based on commonly held belief that surface contamination was very difficult to avoid and could be exploited for standoff detection. We have applied gated Raman spectroscopy for detection of main explosive materials, both factory and homemade. We developed and tested a Raman system for the field remote detection and identification of minimal amounts of explosives on relevant surfaces at a distance of up to 30 m.

Gaft, M.; Nagli, L.

2008-07-01

209

Proposal for the measuring molecular velocity vector with single-pulse coherent Raman spectroscopy  

NASA Technical Reports Server (NTRS)

Methods for simultaneous measurements of more than one flow velocity component using coherent Raman spectroscopy are proposed. It is demonstrated that using a kilowatt broad-band probe pulse (3-30 GHz) along with a megawatt narrow-band pump pulse (approximately 100 MHz), coherent Raman signal resulting from a single laser pulse is sufficient to produce a high-resolution Raman spectrum for a velocity measurement.

She, C. Y.

1983-01-01

210

Resonant Raman spectroscopy of (Mn,Co)-codoped ZnO films  

Microsoft Academic Search

Resonant Raman spectroscopy studies of (Mn, Co)-codoped ZnO films were carried out using the 325 nm laser as the excitation source. The mixed mode character of the longitudinal optical (LO) phonon reveals that the resonant Raman spectra of the films can be used to test the c-axis orientation degree of their crystallite grains. The ratio of integrated Raman intensities between

C. L. Du; Z. B. Gu; Y. M. You; J. Kasim; T. Yu; Z. X. Shen; Z. H. Ni; Y. Ma; G. X. Cheng; Y. F. Chen

2008-01-01

211

Raman spectroscopy of blood in-vitro  

NASA Astrophysics Data System (ADS)

We present Raman spectra from a sample of 8 volunteers that have different type of blood. The experimental data were carried out using a 785 nm excitation laser and an ocean optics spectrometer of 6 cm-1 resolution, with a used spectral region from 1000 to 1800 cm-1. We find Raman features at 1000 and 1542 cm-1 regarded with hemoglobin and its derivatives. Also we find Raman features at 1248 and 1342 cm-1 that are now regarded with pure fibrin. In this work, we use Principal Component analysis (PCA) to determine all variations of our samples, which allows us to define a classification of the influence of the blood type. Finally, we found vibrational lines of cholesterol, glucose and triglycerides that are reported in literature.

Villanueva-Luna, A. E.; Castro-Ramos, J.; Vazquez-Montiel, S.; Flores-Gil, A.; Ortiz-Lima, C. M.; Delgado-Atencio, J. A.

2012-02-01

212

Confocal micro-Raman spectroscopy of single biological cells using optical trapping and shifted excitation difference techniques  

Microsoft Academic Search

We report on the study of single biological cells with a confocal micro-Raman spectroscopy system that uses optical trapping and shifted excitation Raman difference technique. A tunable diode laser was used to capture a living cell in solution, confine it in the confocal excitation volume, and then excite the Raman scattering. The optical trapping allows us to lift the cell

Changan Xie; Yong-Qing Li

2003-01-01

213

Bright emission from a random Raman laser  

PubMed Central

Random lasers are a developing class of light sources that utilize a highly disordered gain medium as opposed to a conventional optical cavity. Although traditional random lasers often have a relatively broad emission spectrum, a random laser that utilizes vibration transitions via Raman scattering allows for an extremely narrow bandwidth, on the order of 10?cm?1. Here we demonstrate the first experimental evidence of lasing via a Raman interaction in a bulk three-dimensional random medium, with conversion efficiencies on the order of a few percent. Furthermore, Monte Carlo simulations are used to study the complex spatial and temporal dynamics of nonlinear processes in turbid media. In addition to providing a large signal, characteristic of the Raman medium, the random Raman laser offers us an entirely new tool for studying the dynamics of gain in a turbid medium.

Hokr, Brett H.; Bixler, Joel N.; Cone, Michael T.; Mason, John D.; Beier, Hope T.; Noojin, Gary D.; Petrov, Georgi I.; Golovan, Leonid A.; Thomas, Robert J.; Rockwell, Benjamin A.; Yakovlev, Vladislav V.

2014-01-01

214

Bright emission from a random Raman laser.  

PubMed

Random lasers are a developing class of light sources that utilize a highly disordered gain medium as opposed to a conventional optical cavity. Although traditional random lasers often have a relatively broad emission spectrum, a random laser that utilizes vibration transitions via Raman scattering allows for an extremely narrow bandwidth, on the order of 10?cm(-1). Here we demonstrate the first experimental evidence of lasing via a Raman interaction in a bulk three-dimensional random medium, with conversion efficiencies on the order of a few percent. Furthermore, Monte Carlo simulations are used to study the complex spatial and temporal dynamics of nonlinear processes in turbid media. In addition to providing a large signal, characteristic of the Raman medium, the random Raman laser offers us an entirely new tool for studying the dynamics of gain in a turbid medium. PMID:25014073

Hokr, Brett H; Bixler, Joel N; Cone, Michael T; Mason, John D; Beier, Hope T; Noojin, Gary D; Petrov, Georgi I; Golovan, Leonid A; Thomas, Robert J; Rockwell, Benjamin A; Yakovlev, Vladislav V

2014-01-01

215

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

Microsoft Academic Search

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 532nm laser line of 35mJ\\/pulse and 20Hz. 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

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

2009-01-01

216

Detecting changes during pregnancy with Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Preterm labor is the second leading cause of neonatal mortality and leads to a myriad of complications like delayed development and cerebral palsy. Currently, there is no way to accurately predict preterm labor, making its prevention and treatment virtually impossible. While there are some at-risk patients, over half of all preterm births do not fall into any high-risk category. This study seeks to predict and prevent preterm labor by using Raman spectroscopy to detect changes in the cervix during pregnancy. Since Raman spectroscopy has been used to detect cancers in vivo in organs like the cervix and skin, it follows that spectra will change over the course of pregnancy. Previous studies have shown that fluorescence decreased during pregnancy and increased during post-partum exams to pre-pregnancy levels. We believe significant changes will occur in the Raman spectra obtained during the course of pregnancy. In this study, Raman spectra from the cervix of pregnant mice and women will be acquired. Specific changes that occur due to cervical softening or changes in hormonal levels will be observed to understand the likelihood that a female mouse or a woman will enter labor.

Vargis, Elizabeth; Robertson, Kesha; Al-Hendy, Ayman; Reese, Jeff; Mahadevan-Jansen, Anita

2010-02-01

217

Amplifier/compressor fiber Raman lasers.  

PubMed

We show that the chirp from cross-phase modulation (XPM) dominates the operation of fiber Raman lasers (FRL's). Thus a FRL in the anomalous group-velocity regime is best described as a XPM-chirped Raman amplifier followed by a linear fiber compressor. While the output of such a laser is generally a narrow pulse with a broad pedestal, we show both experimentally and by computer simulation that negligible background is achievable. PMID:19741882

Islam, M N; Mollenauer, L F; Stolen, R H; Simpson, J R; Shang, H T

1987-10-01

218

The Impact of Array Detectors on Raman Spectroscopy  

ERIC Educational Resources Information Center

The impact of array detectors in the field of Raman spectroscopy and all low-light-level spectroscopic techniques is examined. The high sensitivity of array detectors has allowed Raman spectroscopy to be used to detect compounds at part per million concentrations and to perform Raman analyses at advantageous wavelengths.

Denson, Stephen C.; Pommier, Carolyn J. S.; Denton, M. Bonner

2007-01-01

219

Theoretical analysis of anharmonic coupling and cascading Raman signals observed with femtosecond stimulated Raman spectroscopy  

NASA Astrophysics Data System (ADS)

We present a classical theoretical treatment of a two-dimensional Raman spectroscopy based on the initiation of vibrational coherence with an impulsive Raman pump and subsequent probing by two-pulse femtosecond stimulated Raman spectroscopy (FSRS). The classical model offers an intuitive picture of the molecular dynamics initiated by each laser pulse and the generation of the signal field traveling along the probe wave vector. Previous reports have assigned the observed FSRS signals to anharmonic coupling between the impulsively driven vibration and the higher-frequency vibration observed with FSRS. However, we show that the observed signals are not due to anharmonic coupling, which is shown to be a fifth-order coherent Raman process, but instead due to cascades of coherent Raman signals. Specifically, the observed vibrational sidebands are generated by parallel cascades in which a coherent anti-Stokes or Stokes Raman spectroscopy (i.e., CARS or CSRS) field generated by the coherent coupling of the impulsive pump and the Raman pump pulses participates in a third-order FSRS transition. Additional sequential cascades are discussed that will give rise to cascade artifacts at the fundamental FSRS frequencies. It is shown that the intended fifth-order FSRS signals, generated by an anharmonic coupling mechanism, will produce signals of ~10-4 ?OD (change in the optical density). The cascading signals, however, will produce stimulated Raman signal of ~10-2 ?OD, as has been observed experimentally. Experiments probing deuterochloroform find significant sidebands of the CCl3 bend, which has an E type symmetry, shifted from the A1 type C-D and C-Cl stretching modes, despite the fact that third-order anharmonic coupling between these modes is forbidden by symmetry. Experiments probing a 50:50 mixture of chloroform and d-chloroform find equivalent intensity signals of low-frequency CDCl3 modes as sidebands shifted from both the C-D stretch of CDCl3 and the C-H stretch of CHCl3. Such intermolecular sidebands are allowed in the cascade mechanism, but are expected to be extremely small in the fifth-order frequency modulation mechanism. Each of these observations indicates that the observed signals are due to cascading third-order Raman signals.

Mehlenbacher, Randy D.; Lyons, Brendon; Wilson, Kristina C.; Du, Yong; McCamant, David W.

2009-12-01

220

NIR Raman spectroscopy in medicine and biology: results and aspects  

NASA Astrophysics Data System (ADS)

Analyses of biomaterial by 'classical' Raman spectroscopy with excitation in the visible range has not been possible since the fluorescence of many essential constituents of all animal and plant cells and tissues overlays the Raman spectra completely. Fluorescence, however, is virtually avoided, when Raman spectra are excited with the Nd : YAG laser line at 1064 nm. Within seven dissertations we explored different fields of potential applications to medical diagnostics. Identification and qualification of tissues and cells is possible. Tumors show small but significant differences to normal tissues; in order to develop a reliable tool for tumor diagnostics more research is necessary, especially a collection of reference spectra in a data bank is needed. Raman spectra of biomineralization structures in teeth and bones show pathological tissues as well as the development of new mineralized structures. NIR Raman spectra of flowers, leaves, and fruit show, without special preparation, their constituents: alkaloids, the essential oils, natural dyes, flavors, spices and drugs. They allow application to taxonomy, optimizing plant breeding and control of food.

Schrader, B.; Dippel, B.; Erb, I.; Keller, S.; Löchte, T.; Schulz, H.; Tatsch, E.; Wessel, S.

1999-05-01

221

In Vivo Blood Glucose Quantification Using Raman Spectroscopy  

PubMed Central

We here propose a novel Raman spectroscopy method that permits the noninvasive measurement of blood glucose concentration. To reduce the effects of the strong background signals produced by surrounding tissue and to obtain the fingerprint Raman lines formed by blood analytes, a laser was focused on the blood in vessels in the skin. The Raman spectra were collected transcutaneously. Characteristic peaks of glucose (1125 cm-1) and hemoglobin (1549 cm-1) were observed. Hemoglobin concentration served as an internal standard, and the ratio of the peaks that appeared at 1125 cm-1 and 1549 cm-1 peaks was used to calculate the concentration of blood glucose. We studied three mouse subjects whose blood glucose levels became elevated over a period of 2 hours using a glucose test assay. During the test, 25 Raman spectra were collected transcutaneously and glucose reference values were provided by a blood glucose meter. Results clearly showed the relationship between Raman intensity and concentration. The release curves were approximately linear with a correlation coefficient of 0.91. This noninvasive methodology may be useful for the study of blood glucose in vivo.

Shao, Jingwei; Lin, Manman; Li, Yongqing; Li, Xue; Liu, Junxian; Liang, Jianpin; Yao, Huilu

2012-01-01

222

Femtosecond stimulated Raman spectroscopy of beta-carotene's ultrafast relaxation processes  

Microsoft Academic Search

We have developed the novel technique of femtosecond stimulated Raman spectroscopy (FSRS) to measure vibrational spectra on the femtosecond time scale. FSRS bypasses the time\\/energy resolution limitations of traditional Raman spectroscopy, simultaneously allowing 100 fs time-resolution and 15 cm-1 frequency resolution. The experiment utilizes three laser pulses: (1) a 40 fs visible pump pulse, used to initiate the photochemistry; (2)

Richard A. Mathies; David McCamant; Philip Kukura

2003-01-01

223

Coherent Raman spectroscopy with frequency-shifted and shaped pulses from a photonic-crystal fiber  

Microsoft Academic Search

We demonstrate spectroscopy of coherent anti-Stokes Raman scattering using a frequency-shifted and pulse-shaped output of photonic-crystal fibers pumped by amplified femtosecond Cr: forsterite laser pulses. A dyad of chirped pulses produced by the photonic-crystal fiber with a specially designed dispersion profile are combined with the second-harmonic output of the Cr: forsterite laser, to coherently probe a doublet of Raman resonances

A. A. Ivanov; Ya. M. Linik; D. A. Akimov; M. V. Alfimov; T. Siebert; W. Kiefer; A. M. Zheltikov

2006-01-01

224

Raman spectroscopy explores molecular structural signatures of hidden materials in depth: Universal Multiple Angle Raman Spectroscopy  

PubMed Central

Non-invasive 3D imaging in materials and medical research involves methodologies such as X-ray imaging, MRI, fluorescence and optical coherence tomography, NIR absorption imaging, etc., providing global morphological/density/absorption changes of the hidden components. However, molecular information of such buried materials has been elusive. In this article we demonstrate observation of molecular structural information of materials hidden/buried in depth using Raman scattering. Typically, Raman spectroscopic observations are made at fixed collection angles, such as, 90°, 135°, and 180°, except in spatially offset Raman scattering (SORS) (only back scattering based collection of photons) and transmission techniques. Such specific collection angles restrict the observations of Raman signals either from or near the surface of the materials. Universal Multiple Angle Raman Spectroscopy (UMARS) presented here employs the principle of (a) penetration depth of photons and then diffuse propagation through non-absorbing media by multiple scattering and (b) detection of signals from all the observable angles.

Sil, Sanchita; Umapathy, Siva

2014-01-01

225

Raman spectroscopy explores molecular structural signatures of hidden materials in depth: Universal Multiple Angle Raman Spectroscopy.  

PubMed

Non-invasive 3D imaging in materials and medical research involves methodologies such as X-ray imaging, MRI, fluorescence and optical coherence tomography, NIR absorption imaging, etc., providing global morphological/density/absorption changes of the hidden components. However, molecular information of such buried materials has been elusive. In this article we demonstrate observation of molecular structural information of materials hidden/buried in depth using Raman scattering. Typically, Raman spectroscopic observations are made at fixed collection angles, such as, 90°, 135°, and 180°, except in spatially offset Raman scattering (SORS) (only back scattering based collection of photons) and transmission techniques. Such specific collection angles restrict the observations of Raman signals either from or near the surface of the materials. Universal Multiple Angle Raman Spectroscopy (UMARS) presented here employs the principle of (a) penetration depth of photons and then diffuse propagation through non-absorbing media by multiple scattering and (b) detection of signals from all the observable angles. PMID:24930768

Sil, Sanchita; Umapathy, Siva

2014-01-01

226

Raman and photothermal spectroscopies for explosive detection  

NASA Astrophysics Data System (ADS)

Detection of explosive residues using portable devices for locating landmine and terrorist weapons must sat- isfy the application criteria of high reproducibility, specificity, sensitivity and fast response time. Vibrational spectroscopies such as Raman and infrared spectroscopies have demonstrated their potential to distinguish the members of the chemical family of more than 30 explosive materials. The characteristic chemical fingerprints in the spectra of these explosives stem from the unique bond structure of each compound. However, these spectroscopies, developed in the early sixties, suffer from a poor sensitivity. On the contrary, MEMS-based chemical sensors have shown to have very high sensitivity lowering the detection limit down to less than 1 picogram, (namely 10 part per trillion) using sensor platforms based on microcantilevers, plasmonics, or surface acoustic waves. The minimum amount of molecules that can be detected depends actually on the transducer size. The selectivity in MEMS sensors is usually realized using chemical modification of the active surface. However, the lack of sufficiently selective receptors that can be immobilized on MEMS sensors remains one of the most critical issues. Microcantilever based sensors offer an excellent opportunity to combine both the infrared photothermal spectroscopy in their static mode and the unique mass sensitivity in their dynamic mode. Optical sensors based on localized plasmon resonance can also take up the challenge of addressing the selectivity by monitoring the Surface Enhanced Raman spectrum down to few molecules. The operating conditions of these promising localized spectroscopies will be discussed in terms of reliability, compactness, data analysis and potential for mass deployment.

Finot, Eric; Brulé, Thibault; Rai, Padmnabh; Griffart, Aurélien; Bouhélier, Alexandre; Thundat, Thomas

2013-06-01

227

Summary report of FY 1995 Raman spectroscopy technology development  

SciTech Connect

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.

Douglas, J.G.

1995-11-01

228

Resolution of organic polymorphic crystals by Raman spectroscopy.  

PubMed

Depending on crystallization conditions, many organic compounds can form crystals of different structure. Their proper characterization is important, for example, in the pharmaceutical industry. While the X-ray diffractometry established as a standard method, alternative techniques are desirable for broader application flexibility and economic reasons. In the present study, Raman spectroscopy combined with the density functional calculations is suggested as a complementary method to the X-ray and other higher resolution techniques. The potential to discriminate structural differences in polymorphic crystalline forms is documented on three model compounds of industrial importance. Methacrylamide, piracetam, and 2-thiobarbituric acid were crystallized under various conditions, and their Raman spectra were recorded using 532 and 1064 nm laser excitations. X-ray diffractometry and nuclear magnetic resonance spectroscopy were used as complementary techniques to verify sample composition and structure. To interpret the observed differences in Raman frequencies and intensities, three computational strategies were explored based on single molecule, a cluster model, and a plane-wave periodic boundary conditions calculation. The single-molecule modeling was found inadequate, whereas the plane-wave approach provides the most realistic spectra. For all compounds, the differences in the Raman spectra of polymorphic forms could be unambiguously assigned to the simulations. The modeling revealed that the spectral differences were caused by the molecular structure itself as well as by crystal packing. The relative importance of these factors significantly varied across the investigated samples. Owing to its simplicity, Raman spectroscopy appears to be a promising technique capable of reliable discriminating between organic crystal polymorphic states. PMID:23721200

Dra?ínský, Martin; Procházková, Eliška; Kessler, Ji?í; Šebestík, Jaroslav; Mat?jka, Pavel; Bou?, Petr

2013-06-20

229

Raman Spectroscopy of Supercooled Water.  

NASA Astrophysics Data System (ADS)

To study hydrogen-bonding network in liquid water under supercooled conditions and to relate it to any structural changes which perhaps contribute to the anomalous behavior and structural enhancement in water, we have used Raman spectroscopic technique to study supercooled liquid water down to a temperature of -20(DEGREES)C. Our results are consistent with an interpretation in terms of two categories of OH (OD) bonds; namely, those that are strongly hydrogen bonded and those that are weakly bonded. We find that hydrogen bonding in liquid water becomes stronger with decreasing temperature resulting in the formation of tetrabonded (or clusters of) water molecules which results in structural enhancement. Based on our measurements, we propose that the 3200 cm('-1) spectral band component which is absent from the OH vibrational spectrum of HOD but which prominently appears in the OH stretching vibrational spectrum of H(,2)O is a coupling band. The weakly hydrogen-bonded OH (OD) oscillators give rise to a spectral shoulder which increases in intensity with increasing temperature. We found that the spectral shoulder is an integral part of the OD (OH) vibrational spectrum and that it is not due to intermolecular coupling. Intermolecular coupling of OD oscillators from HOD in H(,2)O has also been investigated. The data indicate that at concentrations of HOD greater than 10 mole %, the effects of intermolecular coupling of OD. . . OD pairs become noticeable. Data analysis resulted in difference spectra which show a characteristic derivative like feature with an increase in intensity around 2400 cm('-1) as intermolecular coupling increases. This has led us to propose a model for explaining the major features of D(,2)O (H(,2)O) spectrum in the liquid state. In our low frequency work, we observed a limiting value to the width of the 190 cm('-1) band at temperatures below the equilibrium freezing point. This suggests that possibly the local structure of supercooled water is approaching some limiting structure. This could be that of amorphous solid water, H(,2)O (as).

Wiafe-Akenten, John

1984-06-01

230

Applications of Raman Spectroscopy to Virology and Microbial Analysis  

NASA Astrophysics Data System (ADS)

This chapter reports from the utilization of Raman spectroscopic techniques like Raman microscopy, Raman optical activity (ROA), UV-resonance Raman (UVRR)-spectroscopy, surface enhanced Raman spectroscopy (SERS), and tip-enhanced Raman spectroscopy (TERS) for the investigation of viruses and microorganisms, especially bacteria and yeasts for medical and pharmaceutical applications. The application of these Raman techniques allows for the analysis of chemical components of cells and subcellular regions, as well as the monitoring of chemical differences occurring as a result of the growth of microorganisms. In addition, the interaction of microorganisms with active pharmaceutical agents can be investigated. In combination with chemometric methods Raman spectroscopy can also be applied to identify microorganisms both in micro colonies and even on single cells.

Harz, Michaela; Stöckel, Stephan; Ciobot?, Valerian; Cialla, Dana; Rösch, Petra; Popp, Jürgen

231

Mineralogy of Meteorite Chelyabinsk as Determined by Raman Spectroscopy  

NASA Astrophysics Data System (ADS)

Using Raman spectroscopy, we have characterized the mineral phases of meteorite Chelyabinsk, fall 15 February 2013, Chelyabinsk, Russia. Raman spectra are shown for olivine, pyroxene, feldspar, magnetite, pyrrhotite, calcite and, possibly, parisite.

Voropaev, S. A.; Eliseev, A. A.; Petukhov, D. I.

2014-06-01

232

Gate modulated Raman spectroscopy of graphene and carbon nanotubes  

NASA Astrophysics Data System (ADS)

Gate-modulated Raman spectroscopy is a method of making Raman measurements while changing the Fermi energy by applying a gate voltage to the sample. In this review article, we overview the techniques of gate modulated Raman spectroscopy in graphene and carbon nanotubes (1) for assigning the combination phonon modes, (2) for understanding the optical processes involved in Raman spectra, and (3) for understanding the electron-phonon interaction not only for zone-center (q=0) phonons but also for double resonance phonons (q?0). The gate modulated Raman spectra are used in carbon nanotubes, too, especially for understanding electron-electron interaction from the electronic Raman spectra that are observed in metallic carbon nanotubes. Finally we discuss our recent work on gate-modulated Raman spectroscopy on bilayer graphene in which we explain how to get information about the interlayer interactions from gate modulated Raman spectroscopy.

Saito, R.; Sato, K.; Araujo, P. T.; Mafra, D. L.; Dresselhaus, M. S.

2013-12-01

233

Surface enhanced Raman spectroscopy in breast cancer cells  

PubMed Central

Background and aims: Raman spectroscopy is a vibrational technique which provides information about the chemical structure. Nevertheless, since many chemicals are present in a cell at very low concentration, the Raman signal observed from a single cell is extremely weak. In surface enhanced Raman scattering (SERS), Raman signals can be enhanced by many orders of magnitude when nanoparticles are incorporated into the cell. Materials (subjects) and methods: The tumor biopsies were obtained from 5 patients who were clinically diagnosed with breast cancer. Breast cancer cells isolated from the biopsy were washed, centrifuged and seeded out. Cultivation took place in DMEM at 37°C in a humidified of 5% CO2 in air with addition of colloidal silver nanoparticles of 40 nm into the cell by sonication. Immediately, the washed cells were analyzed in phosphate buffered saline (PBS) at pH 7. Raman analysis was carried out on the Jobin-Yvon LabRAM HR800 microscope system, with a NIR 830 nm laser excitation source. Results: The strongly enhanced Raman signals allow Raman measurements of a single cell in the 200–1800 cm?1 range in relatively short collection times (5 second) using 17 mW near-infrared excitation. Observed spectral features differed across the cell, but chemical constituents in the cell nucleus and cytoplasm, such as DNA, RNA, and amino acids tyrosine and phenylalanine can be identified. Conclusions: Particularly strong field enhancement can be observed when nanoparticles form colloidal clusters. The results suggest that SERS could be a new technique for the identification of breast cancer cell.

Gonzalez-Solis, JL; Luevano-Colmenero, GH; Vargas-Mancilla, J

2013-01-01

234

Raman gain from waveguides inscribed in KGd(WO4)2 by high repetition rate femtosecond laser  

NASA Astrophysics Data System (ADS)

We report the formation of waveguides in Raman-active KGd(WO4)2 with a focused, high repetition rate femtosecond laser. Parallel guiding regions, formed to either side of the laser-induced damage track, supported TE and TM modes that coupled efficiently to optical fiber at telecom wavelengths. Micro-Raman spectroscopy of the guiding regions revealed the preservation of the characteristic 768 and 901 cm-1 Raman mode intensities. Raman gain with 6% efficiency was demonstrated for the 768 cm-1 Raman line by pumping the waveguide with an infrared 80 ps source, the first time Raman gain has been reported in laser formed waveguides.

Eaton, S. M.; Merchant, C. A.; Iyer, R.; Zilkie, A. J.; Helmy, A. S.; Aitchison, J. S.; Herman, P. R.; Kraemer, D.; Miller, R. J. D.; Hnatovsky, C.; Taylor, R. S.

2008-02-01

235

The effect of aqueous solution in Raman spectroscopy  

Microsoft Academic Search

In Raman detection, the most popular solution for the samples is tri-distilled water. But the effect of aqueous solution is barely studied in Raman spectroscopy. In fact Raman spectroscopy of solid-state and liquid-state are obvious different. In addition, FWHM of Raman spectral peaks also change evidently. In this paper, several samples were selected for the experiment; including sodium nitrate, sodium

Jian Kang; Xiaojuan Yuan; Xiao Dong; Huaimin Gu

2009-01-01

236

Raman spectroscopy offers great potential for the nondestructive confirmatory identification of body fluids.  

PubMed

Raman spectroscopy was used to compare body fluids commonly found at crime scenes in a nondestructive manner. The dry traces of semen, vaginal fluid, sweat, saliva, and blood were analyzed using confocal Raman microscopy with a 785-nm excitation. The results show that the five fluids can be differentiated from one another by visual comparison of their Raman spectra, and that the laser radiation does not damage the sample. The Raman signature of each body fluid is specific and correlates with the known composition of the fluid. Dry traces of human and canine semen exhibited distinctly different Raman signatures. Overall, this preliminary study demonstrates the great potential of Raman spectroscopy for nondestructive, confirmatory identification of body fluids for forensic purposes. PMID:18818034

Virkler, Kelly; Lednev, Igor K

2008-10-25

237

Confocal Raman spectroscopy of whole hairs.  

PubMed

This paper describes the application of Raman spectroscopy to whole hair fibers. Previously this has proved difficult because the hairs are relatively opaque, and spatial resolution diminishes with depth because of the change in refractive index. A solution is to couple confocal Raman with multivariate curve resolution (MCR) data analysis, which separates spectral differences with depth despite this reduction in resolution. Initially, it is shown that the cuticle can be separated from the cortex, showing the differences in the proteins, which can then be plotted as a function of depth, with the cuticle factor being seen only at the surface as expected. Hairs that had been treated in different ways, e.g., by bleaching, treatment with the active molecule resorcinol followed by rinsing and treatment with a full hair care product, were also examined. In all cases, changes to the hair are identified and are associated with specific parts of the fiber. Since the hair fiber is kept intact, it can be repeatedly treated and measured, hence multistep treatment processes can be followed. This method expands the potential use of Raman spectroscopy in hair research. PMID:24359655

Pudney, Paul D A; Bonnist, Eleanor Y M; Mutch, Kevin J; Nicholls, Rachel; Rieley, Hugh; Stanfield, Samuel

2013-12-01

238

Biomedical applications of laser spectroscopy  

NASA Astrophysics Data System (ADS)

Very soon after the invention of the laser, the use of the thermal effects of the radiation was introduced. Such techniques have been refined and the laser is now routinely used for treatment in many specialities. Photodynamic therapy (PDT) is a non-thermal modality employing the combination of a tumor-seeking agent and activating laser light. During the last 15 years laser spectroscopic techniques have also been developed providing powerful means for non-intrusive medical diagnostics of tissue in real time. At the beginning only few groups were involved in exploratory work, but successively the field has developed now to occupy a large number of research teams, which meet at large specialized conferences. We will here consider three aspects of laser diagnostics: fluorescence, Raman and near-IR, and elastic scattering spectroscopy, and we will also briefly discuss PDT. The activity in the field is very extensive, and rather than trying to give a full overview, illustrations from work performed at the Lund University Medical Laser Center will be given.

Svanberg, Sune

1999-07-01

239

Dual-wavelength cascaded Raman fiber laser  

Microsoft Academic Search

We have investigated the characteristics of a dual-wavelength cascaded Raman laser based on a composite resonator configuration using a fiber WDM coupler and two pairs of fiber Bragg gratings. The WDM coupler, which served to form a ring cavity and acted as an output coupler simultaneously, made the laser system simple and effective. Since the WDM coupler is made by

Do Il Chang; Dong Sung Lim; Min Yong Jeon; Hak Kyu Lee; Kyong Hon Kim

2000-01-01

240

Measuring molecular flows with high-resolution stimulated Raman spectroscopy  

NASA Technical Reports Server (NTRS)

It is proposed to use high-resolution stimulated Raman spectroscopy to directly measure high-speed molecular flow velocities in wind tunnels and in combustive chambers. A feasibility study indicates that flow speeds from Mach 0.04 up may be measured with the proposed method using available laser systems. It is pointed out that the success of the proposed technique will make it possible to measure all interesting flow parameters, i.e., species concentration, temperature, and velocity, in a time of less than 1 microsecond at a repetition rate of 10,000/s using a single experimental arrangement.

She, C. Y.; Fairbank, W. M., Jr.; Exton, R. J.

1981-01-01

241

Searching for minicharged particles via birefringence, dichroism and Raman spectroscopy of the vacuum polarized by a high-intensity laser wave  

SciTech Connect

Absorption and dispersion of probe photons in the field of a high-intensity circularly polarized laser wave are investigated. The optical theorem is applied for determining the absorption coefficients in terms of the imaginary part of the vacuum polarization tensor. Compact expressions for the vacuum refraction indices and the photon absorption coefficients are obtained in various asymptotic regimes of interest. The outcomes of this analysis reveal that, far from the region relatively close to the threshold of the two-photon reaction, the birefringence and dichroism of the vacuum are small and, in some cases, strongly suppressed. On the contrary, in a vicinity of the region in which the photo-production of a pair occurs, these optical properties are manifest with lasers of moderate intensities. We take advantage of such a property in the search of minicharged particles by considering high-precision polarimetric experiments. In addition, Raman-like electromagnetic waves resulting from the inelastic part of the vacuum polarization tensor are suggested as an alternative form for finding exclusion limits on these hypothetical charge carriers. The envisaged parameters of upcoming high-intensity laser facilities are used for establishing upper bounds on the minicharged particles. -- Highlights: •Via dichroism and birefringence of the vacuum by a strong laser wave, minicharged particles can be probed. •The discovery potential is the highest in a vicinity of the first pair production threshold. •As alternative observable, Raman scattered waves are put forward.

Villalba-Chávez, S., E-mail: selymv@gmail.com; Müller, C., E-mail: c.mueller@tp1.uni-duesseldorf.de

2013-12-15

242

Off-axis Raman spectroscopy in semiconductors  

NASA Astrophysics Data System (ADS)

The standard geometry for Raman experiments in semiconductors is the backscattering mode. Due to the large index of refraction in these materials, backscattering selection rules are invoked even in cases when the external angle of incidence of the laser beam is not negligible. Small deviations from the backscattering selection rules, however, provide important structural information. For example, these deviations can be used to determine the stress tensor in stressed silicon.(G.H. Loechelt, N.G. Cave, and J. Menéndez, Appl. Phys. Lett. 66), 3639 (1995) We report here a systematic way to enhance the deviations from the backscattering geometry by using high-index of refraction materials as the incident medium. Specifically, we utilize ZnSe crystals to obtain large internal angles of incidence in strained SiGe/Si layers. In addition, we investigate the possibility of observing evanescent field Raman scattering from diamond using total internal reflection conditions at the ZnSe/diamond interface. -------------------------------------------------------------

Shi, Lingyun; Menéndez, José

1998-03-01

243

In vivo Raman spectroscopy for breast cancer: diagnosis in animal model  

NASA Astrophysics Data System (ADS)

Raman spectroscopy has been well established as a powerful method for studying biological tissues and diagnosing diseases. In this study we have developed a breast cancer animal model and collected in vivo Raman spectra of mammary glands of 27 Sprague-Dawley female rats treated with DMBA and 5 non-treated used as control group. A dispersive Raman spectrometer with a @785 nm laser excitation coupled a fiber optic probe and a CCD detector was used to obtain the spectra. The obtained in vivo transcutaneous Raman spectra have shown important differences between normal and abnormal tissues when acquired from one side to the other side of the lesion.

Bitar, R.; Martins, M. A.; Ribeiro, D.; Carvalho, C.; Santos, E. A. P.; Ramalho, L. N. Z.; Ramalho, F.; Martinho, H.; Martin, A. A.

2008-03-01

244

Shifted-excitation Raman difference spectroscopy for in vitro and in vivo biological samples analysis  

PubMed Central

The contamination of the Raman scattering signal with luminescence is a well-known problem when dealing with biological media excited by visible light. The viability of the shifted-excitation Raman difference spectroscopy (SERDS) technique for luminescence suppression on Raman spectra of biological samples was studied in this work. A tunable Lithrow-configuration diode laser (? = 785 and 830 nm) coupled (directly or by optical fiber) to a dispersive Raman spectrometer was employed to study two sets of human tissues (tooth and skin) in order to determine the set of experimental parameters suitable for luminescence rejection. It was concluded that systematic and reproducible spectra of biological interest can be acquired by SERDS.

da Silva Martins, Mario Augusto; Ribeiro, Dayana Goncalves; Pereira dos Santos, Edson Aparecido; Martin, Airton Abrahao; Fontes, Adriana; da Silva Martinho, Herculano

2010-01-01

245

Single cell Raman spectroscopy for cell sorting and imaging.  

PubMed

Single cell Raman spectroscopy (SCRS) is a non-invasive and label-free technology, allowing in vivo and multiple parameter analysis of individual living cells. A single cell Raman spectrum usually contains more than 1000 Raman bands which provide rich and intrinsic information of the cell (e.g. nucleic acids, protein, carbohydrates and lipids), reflecting cellular genotypes, phenotypes and physiological states. A Raman spectrum serves as a molecular 'fingerprint' of a single cell, making it possible to differentiate various cells including bacterial, protistan and animal cells without prior knowledge of the cells. However, a key drawback of SCRS is the fact that spontaneous Raman signals are naturally weak; this review discusses recent research progress in significantly enhancing and improving the signal of spontaneous Raman spectroscopy, including resonance Raman spectroscopy (RRS), coherent anti-Stokes Raman spectroscopy (CARS), stimulated Raman spectroscopy (SRS) and surface enhanced Raman scattering (SERS). This review focuses on the biotechnological development and the associated applications of SCRS, including Raman activated cell sorting (RACS) and Raman imaging and mapping. PMID:22138495

Li, Mengqiu; Xu, Jian; Romero-Gonzalez, Maria; Banwart, Steve A; Huang, Wei E

2012-02-01

246

Cervical cancer detection based on serum sample Raman spectroscopy.  

PubMed

The use of Raman spectroscopy to analyze the biochemical composition of serum samples and hence distinguish between normal and cervical cancer serum samples was investigated. The serum samples were obtained from 19 patients who were clinically diagnosed with cervical cancer, 3 precancer, and 20 healthy volunteer controls. The imprint was put under an Olympus microscope, and around points were chosen for Raman measurement.All spectra were collected at a Horiba Jobin-Yvon LabRAM HR800 Raman Spectrometer with a laser of 830-nm wavelength and 17-mW power irradiation. Raw spectra were processed by carrying out baseline correction, smoothing, andnormalization to remove noise, florescence, and shot noise and then analyzed using principal component analysis (PCA). The control serum spectrum showed the presence of higher amounts of carotenoids indicated by peaks at 1,002, 1,160, and 1,523 cm(-1)and intense peaks associated with protein components at 754, 853, 938, 1,002, 1,300-1,345, 1,447, 1,523, 1,550, 1,620, and 1,654 cm(-1). The Raman bands assigned to glutathione (446, 828, and 1,404 cm(-1)) and tryptophan (509, 1,208, 1,556, 1,603, and 1,620 cm(-1)) in cervical cancer were higher than those of control samples, suggesting that their presence may also play a role in cervical cancer. Furthermore, weak bands in the control samples attributed to tryptophan (545, 760, and 1,174 cm(-1)) and amide III (1,234-1,290 cm(-1)) seem to disappear and decrease in the cervical cancer samples, respectively. It is shown that the serum samples from patients with cervical cancer and from the control group can be discriminated with high sensitivity and specificity when the multivariate statistical methods of PCA is applied to Raman spectra. PCA allowed us to define the wavelength differences between the spectral bands of the control and cervical cancer groups by confirming that the main molecular differences among the control and cervical cancer samples were glutathione, tryptophan, ? carotene, and amide III. The preliminary results suggest that Raman spectroscopy could be a highly effective technique with a strong potential of support for current techniques as Papanicolaou smear by reducing the number of these tests; nevertheless, with the construction of a data library integrated with a large number of cervical cancer and control Raman spectra obtained from a wide range of healthy and cervical cancer population, Raman-PCA technique could be converted into a new technique for noninvasive real-time diagnosis of cervical cancer from serum samples. PMID:24197519

González-Solís, José Luis; Martínez-Espinosa, Juan Carlos; Torres-González, Luis Adolfo; Aguilar-Lemarroy, Adriana; Jave-Suárez, Luis Felipe; Palomares-Anda, Pascual

2014-05-01

247

Raman spectroscopy study of carbon-doped resorcinol-formaldehyde thin films  

NASA Astrophysics Data System (ADS)

In this work, we investigated the properties of carbon resorcinol-formaldehyde (RF) cryogel thin films. RF cryogels were doped by single-wall carbon nanotubes, graphene and graphene quantum dots. The structure of the deposited films was investigated by Raman spectroscopy, and optical, transmission electron and atomic force microscopy. Raman spectroscopy was performed using three excitation laser energies in the visible range. The effect of glass substrate on the Raman features of investigated carbon cryogel thin films was determined as well. The particle size of the carbon-doped RF cryogel thin films was determined by atomic force microscopy.

Kleut, D. N.; Markovi, Z. M.; Babi?, B. M.; Holclajtner Antunovi?, I. D.; Milosavljevi?, M. S.; Drami?anin, M. D.; Todorovi? Markovi?, B. M.

2013-11-01

248

Laser Raman probe for combustion diagnostics  

NASA Astrophysics Data System (ADS)

The objective of this work is to apply light scattering diagnostics to the study of a well-defined combustion flow. Product gas densities are measured for a turbulent jet diffusion flame through use of vibrational Raman scattering techniques. These are combined with simultaneous temperature data from Raman scattering and near-simultaneous velocity data from laser velocimetry, to give an integrated probe system for basic flame properties.

Lapp, M.; Drake, M. C.; Penney, C. M.; Warshaw, S.

1982-11-01

249

In vivo lipidomics using single-cell Raman spectroscopy  

PubMed Central

We describe a method for direct, quantitative, in vivo lipid profiling of oil-producing microalgae using single-cell laser-trapping Raman spectroscopy. This approach is demonstrated in the quantitative determination of the degree of unsaturation and transition temperatures of constituent lipids within microalgae. These properties are important markers for determining engine compatibility and performance metrics of algal biodiesel. We show that these factors can be directly measured from a single living microalgal cell held in place with an optical trap while simultaneously collecting Raman data. Cellular response to different growth conditions is monitored in real time. Our approach circumvents the need for lipid extraction and analysis that is both slow and invasive. Furthermore, this technique yields real-time chemical information in a label-free manner, thus eliminating the limitations of impermeability, toxicity, and specificity of the fluorescent probes common in currently used protocols. Although the single-cell Raman spectroscopy demonstrated here is focused on the study of the microalgal lipids with biofuel applications, the analytical capability and quantitation algorithms demonstrated are applicable to many different organisms and should prove useful for a diverse range of applications in lipidomics.

Wu, Huawen; Volponi, Joanne V.; Oliver, Ann E.; Parikh, Atul N.; Simmons, Blake A.; Singh, Seema

2011-01-01

250

Stand-off detection of chemicals by UV Raman spectroscopy  

SciTech Connect

Experimental results are reported on a mobile, stand-alone, solar-blind ultraviolet (UV) Raman lidar system for the stand-off detection and identification of liquid and solid targets at ranges of hundreds of meters. The lidar is a coaxial system capable of performing range-resolved measurements of gases and aerosols, as well as solids and liquids. The transmitter is a flash lamp pumped 30 Hz Nd:YAG laser with quadrupled output at 266 nm. The receiver subsystem is comprised of a 40 cm Cassegrain telescope, a holographic UV edge filter for suppressing the elastic channel, a 0.46 m Czerny-Turner spectrometer, and a time gated intensified charge-coupled device (CCD) detector. The rejection of elastic light scattering by the edge filter is better than one part in 10{sup 5}, while the transmittance 500 cm-1 to the red of the laser line is greater than 50%. Raman data are shown for selected solids, neat liquids, and mixtures down to the level of 1% volume ratio. On the basis of the strength of the Raman returns, a stand-off detection limit of {approx}500 g/m2 for liquid spills of common solvents at the range of one half of a kilometer is possible. (c) 2000 Society for Applied Spectroscopy.

Wu, Ming [Department of Advanced Technology, Brookhaven National Laboratory, Upton, New York 11973 (United States)] [Department of Advanced Technology, Brookhaven National Laboratory, Upton, New York 11973 (United States); Ray, Mark [Department of Advanced Technology, Brookhaven National Laboratory, Upton, New York 11973 (United States)] [Department of Advanced Technology, Brookhaven National Laboratory, Upton, New York 11973 (United States); Hang Fung, K. [Department of Advanced Technology, Brookhaven National Laboratory, Upton, New York 11973 (United States)] [Department of Advanced Technology, Brookhaven National Laboratory, Upton, New York 11973 (United States); Ruckman, Mark W. [Department of Advanced Technology, Brookhaven National Laboratory, Upton, New York 11973 (United States)] [Department of Advanced Technology, Brookhaven National Laboratory, Upton, New York 11973 (United States); Harder, David [Department of Advanced Technology, Brookhaven National Laboratory, Upton, New York 11973 (United States)] [Department of Advanced Technology, Brookhaven National Laboratory, Upton, New York 11973 (United States); Sedlacek, Arthur J. III [Department of Advanced Technology, Brookhaven National Laboratory, Upton, New York 11973 (United States)] [Department of Advanced Technology, Brookhaven National Laboratory, Upton, New York 11973 (United States)

2000-06-01

251

Raman Spectroscopy and instrumentation for monitoring soil carbon systems.  

SciTech Connect

This work describes developments in the application of Raman scattering and surface-enhanced Raman scattering (SERS) towards the assessment/characterization of carbon in soil. In the past, the nonspecific total carbon mass content of soil samples has generally been determined through mass loss techniques and elemental analysis. However, because of the concern over CO{sub 2} buildup in the atmosphere and its possible role in the ''Greenhouse Effect,'' there is a need for better-defined models of global cycling of carbon. As a means towards this end, there is a need to know more about the structure and functionality of organic materials in soil. Raman spectroscopy may therefore prove to be an exceptional tool in soil carbon analysis. Based on vibrational transitions of irradiated molecules, it provides structural information that is often suitable for sample identification. Furthermore, Raman scattering yields very fine spectral features which offer the potential for multicomponent sample analysis with minimal or no sample pretreatment. Although the intensity of Raman scattering is generally extremely low, the surface-enhanced Raman scattering (SERS) effect can greatly enhance Raman signals (10{sup 6}-10{sup 8} range) through the adsorption of compounds on specially roughened metal surfaces. In our laboratory, we have investigated copper, gold and silver as possible substrate metals in the fabrication of SERS substrates. These substrates have included metal-coated microparticles, metal island films, and redox-roughened metal foils. We have evaluated several laser excitation sources spanning the 515-785 nm range for both Raman and SERS analysis. For this particular study, we have selected fulvic and humic acids as models for establishing the feasibility of using Raman and SERS in soil carbon analysis. Our studies thus far have demonstrated that copper substrates perform best in the SERS detection of humic and fulvic acids, particularly when coupled to electrochemical processes that enhance adsorption of specific compounds. This effect not only yields a stronger signal, but can also impart selectivity in the analysis of complex samples such as soil.

Stokes, D.L.

2003-12-08

252

Average Power and Brightness Scaling of Diamond Raman Lasers.  

National Technical Information Service (NTIS)

Diamond holds substantial promise as a high Raman gain laser material with outstanding power handling capability, yet despite this the highest reported output power from a diamond Raman laser prior to this project was approximately 1 W. This report descri...

R. Mildren

2012-01-01

253

Applications of Microprobe Raman Spectroscopy in Food Science  

Microsoft Academic Search

The Raman microprobe combines the analytical properties of Raman spectroscopy and the visualization capabilities of a high quality microscope, allowing localization and identification of species and phases in time intervals of seconds to a few minutes with a spatial resolution down to 1 µm. This article describes the basic principles of operation of the Raman microprobe and some applications that

A. Celedón; J. M. Aguilera

2002-01-01

254

UTI diagnosis and antibiogram using Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Urinary tract infection diagnosis and antibiogram require a 48 hour waiting period using conventional methods. This results in ineffective treatments, increased costs and most importantly in increased resistance to antibiotics. In this work, a novel method for classifying bacteria and determining their sensitivity to an antibiotic using Raman spectroscopy is described. Raman spectra of three species of gram negative Enterobacteria, most commonly responsible for urinary tract infections, were collected. The study included 25 samples each of E.coli, Klebsiella p. and Proteus spp. A novel algorithm based on spectral ratios followed by discriminant analysis resulted in classification with over 94% accuracy. Sensitivity and specificity for the three types of bacteria ranged from 88-100%. For the development of an antibiogram, bacterial samples were treated with the antibiotic ciprofloxacin to which they were all sensitive. Sensitivity to the antibiotic was evident after analysis of the Raman signatures of bacteria treated or not treated with this antibiotic as early as two hours after exposure. This technique can lead to the development of new technology for urinary tract infection diagnosis and antibiogram with same day results, bypassing urine cultures and avoiding all undesirable consequences of current practice.

Kastanos, Evdokia; Kyriakides, Alexandros; Hadjigeorgiou, Katerina; Pitris, Constantinos

2009-07-01

255

Coronagraphic Notch Filter for Raman Spectroscopy  

NASA Technical Reports Server (NTRS)

A modified coronagraph has been proposed as a prototype of improved notch filters in Raman spectrometers. Coronagraphic notch filters could offer alternatives to both (1) the large and expensive double or triple monochromators in older Raman spectrometers and (2) holographic notch filters, which are less expensive but are subject to environmental degradation as well as to limitations of geometry and spectral range. Measurement of a Raman spectrum is an exercise in measuring and resolving faint spectral lines close to a bright peak: In Raman spectroscopy, a monochromatic beam of light (the pump beam) excites a sample of material that one seeks to analyze. The pump beam generates a small flux of scattered light at wavelengths slightly greater than that of the pump beam. The shift in wavelength of the scattered light from the pump wavelength is known in the art as the Stokes shift. Typically, the flux of scattered light is of the order of 10 7 that of the pump beam and the Stokes shift lies in the wave-number range of 100 to 3,000 cm 1. A notch filter can be used to suppress the pump-beam spectral peak while passing the nearby faint Raman spectral lines. The basic principles of design and operation of a coronagraph offer an opportunity for engineering the spectral transmittance of the optics in a Raman spectrometer. A classical coronagraph may be understood as two imaging systems placed end to end, such that the first system forms an intermediate real image of a nominally infinitely distant object and the second system forms a final real image of the intermediate real image. If the light incident on the first telescope is collimated, then the intermediate image is a point-spread function (PSF). If an appropriately tailored occulting spot (e.g., a Gaussian-apodized spot with maximum absorption on axis) is placed on the intermediate image plane, then the instrument inhibits transmission of light from an on-axis source. However, the PSFs of off-axis light sources are formed off axis - that is, away from the occulting spot - so that they become refocused onto the final image plane.

Cohen, David; Stirbl, Robert

2004-01-01

256

Intracavity and resonant Raman crystal fiber laser  

NASA Astrophysics Data System (ADS)

We demonstrated an efficient, compact, and continuous-wave Raman crystal fiber laser (RCFL) using an intracavity and resonant ?(3) approach. The gain and nonlinear medium was Cr4+:Y3Al5O12 double-clad crystal fiber grown using the codrawing laser-heated pedestal growth technique. The RCFL threshold was only 50 mW, and the slope efficiency reached 14.3% above a pump power of 350 mW. The result is in good agreement with theory, which indicates a near-100% quantum efficiency of resonant stimulated Raman scattering.

Lai, Chien-Chih; Ke, Chih-Peng; Liu, Shih-Kun; Lo, Chia-Yao; Jheng, Dong-Yo; Wang, Shih-Chang; Lin, Si-Rong; Yeh, Pinghui S.; Huang, Sheng-Lung

2012-06-01

257

Remote sensing capacity of Raman spectroscopy in identification of mineral and organic constituents  

NASA Astrophysics Data System (ADS)

We present design, integration and test results for a field Raman spectrometer science payload, integrated into the Mars Analog Research and Technology (MARTE) drilling platform. During the drilling operation, the subsurface Raman spectroscopy inspection system has obtained signatures of organic and mineral compositions. We also performed ground truth studies using both this field unit and a laboratory micro Raman spectrometer equipped with multiple laser excitation wavelengths on series of field samples including Mojave rocks, Laguna Verde salty sediment and Rio Tinto topsoil. We have evaluated laser excitation conditions and optical probe designs for further improvement. We have demonstrated promising potential for Raman spectroscopy as a non-destructive in situ, high throughput, subsurface detection technique, as well as a desirable active remote sensing tool for future planetary and space missions.

Chen, Bin; Stoker, Carol; Cabrol, Nathalie; McKay, Christopher P.

2007-10-01

258

Detection of Cervical Cancer Analyzing Blood Samples with Raman Spectroscopy and Multivariate Analysis  

NASA Astrophysics Data System (ADS)

The use of Raman spectroscopy to analyze blood biochemistry and hence distinguish between normal and abnormal blood was investigated. The blood samples were obtained from 20 patients who were clinically diagnosed with cervical cancer and 10 healthy volunteer. The imprint was put under the Olympus microscope and several points were chosen for Raman measurement. All spectra were collected at a Jobin-Yvon LabRAM HR800 Raman Spectrometer with NIR 830 nm laser. It is shown that the serum samples from patients with cervical cancer and from the control group can be discriminated when the multivariate statistical methods of Principal Component Analysis (PCA) and Linear Discriminated Analysis (LDA) is applied to their Raman spectra. The ratios of some band intensities were analyzed and some band ratios were significant and corresponded to proteins, phospholipids, and polysaccharides. The preliminary results suggest that Raman spectroscopy could be a new technique for the detection using just blood samples.

González-Solís, J. L.; Rodríguez-López, J.; Martínez-Espinosa, J. C.; Frausto-Reyes, C.; Jave-Suárez, L. F.; Aguilar-Lemarroy, A. C.; Vargas-Rodríguez, H.; Martínez-Cano, E.

2010-05-01

259

Stage Determination of Breast Cancer Biopsy Using Raman Spectroscopy and Multivariate Analysis  

NASA Astrophysics Data System (ADS)

The use of Raman spectroscopy to analyze biopsy biochemistry and hence distinguish between the breast cancer stages was investigated. The biopsy samples were obtained from 13 patients who were clinically diagnosed with breast cancer. A preliminary diagnosis of some breast cancer patient was realized by pathologist of the Cancer Institute. The biopsies were put under the microscope and several points were chosen for Raman measurement. All spectra were collected at a Jobin-Yvon LabRAM HR800 Raman Spectrometer with a NIR 830 nm laser. It is shown that the breast cancer stages of biopsies can be discriminated when the Principal Components Analysis (PCA) is applied to their Raman spectra. Ratios of some band intensities were analyzed and corresponded to proteins, phospholipids, and polysaccharides. The preliminary results suggest that Raman spectroscopy could be an excellent technique for stage determination of breast cancer.

González-Solís, J. L.; Aguińaga-Serrano, B. I.; Martínez-Espinosa, J. C.; Oceguera-Villanueva, A.

2011-08-01

260

Theory of stimulated Raman scattering with broad-band lasers  

Microsoft Academic Search

The authors have extended the theory of stimulated Raman scattering to include the effects of laser bandwidths, in both the transient and steady-state regimes. The case of two interacting laser beams, a pump laser and a probe (Stokes) laser, is treated. Using the phase-diffusion model for laser bandwidth, the authors demonstrate that in the absence of dispersion, the forward Raman

M. G. Raymer; J. Mostowski; J. L. Carlsten

1979-01-01

261

Raman and infrared spectroscopy of pyridine under high pressure  

Microsoft Academic Search

We report the structural transitions of pyridine as a function of pressure up to 26 GPa using in situ Raman spectroscopy and infrared absorption spectroscopy. By monitoring changes in the Raman shifts in the lattice region as well as the band profiles in both Raman and IR spectra, a liquid-to-solid transition at 1 GPa followed by solid-to-solid transitions at 2,

Kirill K. Zhuravlev; Katrina Traikov; Zhaohui Dong; Shuntai Xie; Yang Song; Zhenxian Liu

2010-01-01

262

Characterization of a Co–Se thin film by scanning Auger microscopy and Raman spectroscopy  

Microsoft Academic Search

Scanning Auger microscopy and micro-Raman spectroscopy are combined to characterize a Co–Se thin film sample, containing 84at.% Se, which had been modified in localized areas following excitation with an intense focused Ar+ laser (514.5nm). The information obtained helps to establish that a previous assignment for a Co–Se sample of Raman features between 168 and 175cm?1 actually refers to an oxygenated

M. Teo; P. C. Wong; L. Zhu; D. Susac; S. A. Campbell; K. A. R. Mitchell; R. R. Parsons; D. Bizzotto

2006-01-01

263

Calcium oxalate in lichen biodeterioration studied using FT-Raman spectroscopy  

Microsoft Academic Search

The biodeterioration of diverse natural and man-made substrata by Caloplaca aurantia, Lecanora muralis and Acarospora oxytoma has been studied using FT-Raman spectroscopy with 1064 nm laser excitation. Each of the three lichen species produce relatively large amounts of calcium oxalate in encrustations at the thallus—substratum interface during the biodeterioration process; the Raman spectroscopic technique is capable of identifying non-destructively the

H. G. M. Edwards; N. C. Russell; M. R. D. Seaward

1997-01-01

264

Characterisation of thermally annealed diamond like carbon (DLC) and silicon modified DLC films by Raman spectroscopy  

Microsoft Academic Search

Raman spectroscopy has been used to investigate the structural changes in thermally annealed diamond like carbon (a-C:H) and silicon modified diamond like carbon (a-C:H:Si) films prepared by plasma enhanced chemical vapour deposition (PECVD) using a 514.53nm argon ion laser excitation. The changes in the Raman spectra of the films has been used to monitor structural modifications with increasing annealing temperature.

A. A. Ogwu; R. W Lamberton; S. Morley; P. Maguire; J. McLaughlin

1999-01-01

265

Microsystem 671 nm light source for shifted excitation Raman difference spectroscopy.  

PubMed

We present a compact wavelength stabilized diode laser system at 671 nm on a micro-optical bench as a light source for shifted excitation Raman difference spectroscopy (SERDS). The laser system consists of two broad-area gain media in separate laser cavities using two reflection Bragg gratings with slightly different center wavelengths. A spectral width below 100 pm and a constant wavelength shift of 0.57 +/- 0.06 nm is obtained up to output powers of 250 mW. The suitability of this light source for SERDS is demonstrated using Raman spectra of ethanol with increasing concentrations of Cresyl Violet as the fluorescent contaminant. PMID:19458726

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

2009-05-20

266

Raman laser with controllable suppression of parasitics  

DOEpatents

Method and apparatus for switching energy out of a Raman laser optical cavity. Coherent radiation at both the pump and first Stokes wave frequencies are introduced into the optical cavity from the same direction, and a second Stokes wave is utilized to switch the energy out of the cavity.

George, E. Victor (Livermore, CA)

1986-01-01

267

AFM CHARACTERIZATION OF RAMAN LASER INDUCED DAMAGE ON CDZNTECRYSTAL SURFACES  

SciTech Connect

High quality CdZnTe (or CZT) crystals have the potential for use in room temperature gamma-ray and X-ray spectrometers. Over the last decade, the methods for growing high quality CZT have improved the quality of the produced crystals however there are material features that can influence the performance of these materials as radiation detectors. The presence of structural heterogeneities within the crystals, such as twinning, pipes, grain boundaries (polycrystallinity), and secondary phases (SPs) can have an impact on the detector performance. There is considerable need for reliable and reproducible characterization methods for the measurement of crystal quality. With improvements in material characterization and synthesis, these crystals may become suitable for widespread use in gamma radiation detection. Characterization techniques currently utilized to test for quality and/or to predict performance of the crystal as a gamma-ray detector include infrared (IR) transmission imaging, synchrotron X-ray topography, photoluminescence spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM) and Raman spectroscopy. In some cases, damage caused by characterization methods can have deleterious effects on the crystal performance. The availability of non-destructive analysis techniques is essential to validate a crystal's quality and its ability to be used for either qualitative or quantitative gamma-ray or X-ray detection. The work presented herein discusses the damage that occurs during characterization of the CZT surface by a laser during Raman spectroscopy, even at minimal laser powers. Previous Raman studies have shown that the localized annealing from tightly focused, low powered lasers results in areas of higher Te concentration on the CZT surface. This type of laser damage on the surface resulted in decreased detector performance which was most likely due to increased leakage current caused by areas of higher Te concentration. In this study, AFM was used to characterize the extent of damage to the CZT crystal surface following exposure to a Raman laser. AFM data reveal localized surface damage and increased conductivity in the areas exposed to the Raman laser beam.

Teague, L.; Duff, M.

2008-10-07

268

Measurement of clathrate hydrates via Raman spectroscopy  

USGS Publications Warehouse

Raman spectra of clathrate hydrate guest molecules are presented for three known structures (I (sI), II (sII), and H (sH)) in the following systems: CH4 (sI), CO2 (sI), C3H8 (sII), CH4 + CO2 (sI), CD4 + C3H8 (sII), CH4 + N2 (sI), CH4 + THF-d8 (sII), and CH4 + C7D14 (sH). Relative occupancy of CH4 in the large and small cavities of sI were determined by deconvoluting the ??1 symmetric bands, resulting in hydration numbers of 6.04 ?? 0.03. The frequency of the ??1 bands for CH4 in structures I, II, and H differ statistically, so that Raman spectroscopy is a potential tool to identify hydrate crystal structure. Hydrate guest compositions were also measured for two vapor compositions of the CH4 + CO2 system, and they compared favorably with predictions. The large cavities were measured to be almost fully occupied by CH4 and CO2, whereas only a small fraction of the small cavities are occupied by CH4. No CO2 was found in the small cavities. Hydration numbers from 7.27 to 7.45 were calculated for the mixed hydrate.

Sum, A. K.; Burruss, R. C.; Sloan, Jr. , E. D.

1997-01-01

269

Raman spectroscopy of lithographically patterned graphene nanoribbons.  

PubMed

Nanometer-scale graphene objects are attracting much research interest because of newly emerging properties originating from quantum confinement effects. We present Raman spectroscopy studies of graphene nanoribbons (GNRs), which are known to have nonzero electronic bandgap. GNRs of width ranging from 15 to 100 nm have been prepared by e-beam lithographic patterning of mechanically exfoliated graphene followed by oxygen plasma etching. Raman spectra of narrow GNRs can be characterized by an upshifted G band and a prominent disorder-related D band originating from scattering at the ribbon edges. The D-to-G band intensity ratio generally increases with decreasing ribbon width. However, its decrease in width of <25 nm, partly attributed to amorphization at the edges, provides a valuable experimental estimate on D mode relaxation length of <5 nm. The upshift in the G band of the narrowest GNRs can be attributed to confinement effect or chemical doping by functional groups on the GNR edges. Notably, GNRs are much more susceptible to photothermal effects resulting in reversible hole doping caused by atmospheric oxygen than bulk graphene sheets. Finally we show that the 2D band is still a reliable marker in determining the number of layers of GNRs despite its significant broadening for very narrow GNRs. PMID:21452879

Ryu, Sunmin; Maultzsch, Janina; Han, Melinda Y; Kim, Philip; Brus, Louis E

2011-05-24

270

Development of a multiplexing fingerprint and high wavenumber Raman spectroscopy technique for real-time in vivo tissue Raman measurements at endoscopy.  

PubMed

We report on the development of a novel multiplexing Raman spectroscopy technique using a single laser light together with a volume phase holographic (VPH) grating that simultaneously acquires both fingerprint (FP) and high wavenumber (HW) tissue Raman spectra at endoscopy. We utilize a customized VPH dual-transmission grating, which disperses the incident Raman scattered light vertically onto two separate segments (i.e., -150 to 1950??cm?ą; 1750 to 3600??cm?ą) of a charge-coupled device camera. We demonstrate that the multiplexing Raman technique can acquire high quality in vivo tissue Raman spectra ranging from 800 to 3600??cm?ą within 1.0 s with a spectral resolution of 3 to 6??cm?ą during clinical endoscopy. The rapid multiplexing Raman spectroscopy technique covering both FP and HW ranges developed in this work has potential for improving in vivo tissue diagnosis and characterization at endoscopy. PMID:23450298

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

2013-03-01

271

Searching for minicharged particles via birefringence, dichroism and Raman spectroscopy of the vacuum polarized by a high-intensity laser wave  

NASA Astrophysics Data System (ADS)

Absorption and dispersion of probe photons in the field of a high-intensity circularly polarized laser wave are investigated. The optical theorem is applied for determining the absorption coefficients in terms of the imaginary part of the vacuum polarization tensor. Compact expressions for the vacuum refraction indices and the photon absorption coefficients are obtained in various asymptotic regimes of interest. The outcomes of this analysis reveal that, far from the region relatively close to the threshold of the two-photon reaction, the birefringence and dichroism of the vacuum are small and, in some cases, strongly suppressed. On the contrary, in a vicinity of the region in which the photo-production of a pair occurs, these optical properties are manifest with lasers of moderate intensities. We take advantage of such a property in the search of minicharged particles by considering high-precision polarimetric experiments. In addition, Raman-like electromagnetic waves resulting from the inelastic part of the vacuum polarization tensor are suggested as an alternative form for finding exclusion limits on these hypothetical charge carriers. The envisaged parameters of upcoming high-intensity laser facilities are used for establishing upper bounds on the minicharged particles.

Villalba-Chávez, S.; Müller, C.

2013-12-01

272

ExoMars Raman laser spectrometer for Exomars  

NASA Astrophysics Data System (ADS)

The Raman Laser Spectrometer (RLS) is one of the Pasteur Payload instruments, within the ESA's Aurora Exploration Programme, ExoMars mission. ExoMars 2018 main Scientific objective is "Searching for evidence of past and present life on Mars". Raman Spectroscopy is used to analyze the vibrational modes of a substance either in the solid, liquid or gas state. It relies on the inelastic scattering (Raman Scattering) of monochromatic light produced by atoms and molecules. The radiation-matter interaction results in the energy of the exciting photons to be shifted up or down. The shift in energy appears as a spectral distribution and therefore provides an unique fingerprint by which the substances can be identified and structurally analyzed. The RLS is being developed by an European Consortium composed by Spanish, French, German and UK partners. It will perform Raman spectroscopy on crushed powdered samples inside the Rover's Analytical Laboratory Drawer. Instrument performances are being evaluated by means of simulation tools and development of an instrument prototype.

Rull, F.; Sansano, A.; Díaz, E.; Canora, C. P.; Moral, A. G.; Tato, C.; Colombo, M.; Belenguer, T.; Fernández, M.; Manfredi, J. A. R.; Canchal, R.; Dávila, B.; Jiménez, A.; Gallego, P.; Ibarmia, S.; Prieto, J. A. R.; Santiago, A.; Pla, J.; Ramos, G.; Díaz, C.; González, C.

2011-09-01

273

From Femtosecond Dynamics to Breast Cancer Diagnosis by Raman Spectroscopy  

NASA Astrophysics Data System (ADS)

This paper presents new results based on Raman spectroscopy and demonstrates its utilisation as a diagnostic and development tool with the key advantage in breast cancer research. Applications of Raman spectroscopy in cancer research are in the early stages of development. However, research presented here as well as performed in a few other laboratories demonstrate the ability of Raman spectroscopy to accurately characterize cancer tissue and distinguish between normal, malignant and benign types. The main goals of bio-Raman spectroscopy at this stage are threefold. Firstly, the aim is to develop the diagnostic ability of Raman spectroscopy so it can be implemented in a clinical environment, producing accurate and rapid diagnoses. Secondly, the aim is to optimize the technique as a diagnostic tool for the non-invasive real time medical applications. Thirdly, the aim is to formulate some hypothesis based on Raman spectroscopy on the molecular mechanism which drives the transformation of normal human cells into highly malignant derivatives. To the best of our knowledge, this is the most statistically reliable report on Raman spectroscopy-based diagnosis of breast cancers among the world women population.

Abramczyk, H.; Placek, I.; Bro?ek-P?uska, B.; Kurczewski, K.; Morawiec, Z.; Tazbir, M.

2007-12-01

274

Discrimination of normal and colorectal cancer using Raman spectroscopy and fluorescence  

NASA Astrophysics Data System (ADS)

Laser-induced fluorescence spectroscopy (LIF) and Raman spectrum of serum for diagnosis of colon cancer and rectum cancer were investigated in this paper. The aim of this study was that using Raman spectrum and LIF analysis the serum of colon cancer and rectum cancer for found the difference compared to normal, the difference was found. For example: the intensity and red shift both different In this paper we investigated 82 colon cancers, 69 rectum cancers and obtained 80.7%, 82.5% accuracy to rectum cancer and colon cancer separately compared to clinical diagnostic. It is exploring that use Raman spectrum and LIF to detection of cancer.

Li, Xiaozhou; Wang, Deli; Wang, Yue

2007-06-01

275

Au-coated ZnO nanostructures for surface enhanced Raman spectroscopy applications  

SciTech Connect

Thin ZnO nanostructured films were produced by pulsed laser deposition (PLD) for surface enhanced Raman spectroscopy (SERS) studies. The experimental conditions used for preparation of the samples were chosen to obtain different types of ZnO nanostructures. The Raman spectra of rhodamine 6G (R6G) were measured at an excitation wavelength of 785 nm after coating the ZnO nanostructures with a thin Au layer. The influence of the surface morphology on the Raman signal obtained from the samples was investigated. High SERS signal enhancement was observed from all Au-coated ZnO nanostructures.

Dikovska, A O; Nedyalkov, N N; Imamova, S E; Atanasova, G B; Atanasov, P A

2012-03-31

276

Combined In Vivo Confocal Raman Spectroscopy and Confocal Microscopy of Human Skin  

Microsoft Academic Search

In vivo confocal Raman spectroscopy is a noninvasive optical method to obtain detailed information about the molecular composition of the skin with high spatial resolution. In vivo confocal scanning laser microscopy is an imaging modality that provides optical sections of the skin without physically dissecting the tissue. A combination of both techniques in a single instrument is described. This combination

P. J. Caspers; G. W. Lucassen; G. J. Puppels

2003-01-01

277

Characterization of human skin cells for tissue engineering applications by Raman spectroscopy  

Microsoft Academic Search

In the field of cell culture and tissue engineering is an increasing need for non-invasive methods to analyze living cells in vitro. One important application is the cell characterization in tissue engineering products. Raman spectroscopy is a method which analyzes cells without lysis, fixation or the use of any chemicals and do not affect cell vitality adversely if suitable laser

Marieke Pudlas; Steffen Koch; Carsten Bolwien; Heike Walles

2010-01-01

278

Coherent anti-stokes Raman spectroscopy system for point temperature and major species concentration measurement  

SciTech Connect

The Coherent anti-Stokes Raman Spectroscopy system (CARS) has been developed as a laser-based, advanced, combustion-diagnostic technique to measure temperature and major species concentration. Principles of operation, description of the system and its capabilities, and operational details of this instrument are presented in this report.

Singh, J.P.; Yueh, Fang-Yu

1993-10-01

279

Raman investigation of amorphous carbon in diamond film treated by laser  

Microsoft Academic Search

Micro-Raman spectroscopy was employed to investigate the structural changes of diamond films prepared by hot filament chemical vapor deposition and treated by femtosecond (fs) laser and nanosecond (ns) lasers. Breit-Wigner-Fano and Lorentzian line shape simulations were used to fit the spectra. For 266 nm ns laser treated samples, increasing laser power density results in the transformation of amorphous carbons in

Qihong Wu; Lin Yu; Yurong Ma; Yuan Liao; Rongchuan Fang; Ligong Zhang; Xiangli Chen; Kelvin Wang

2003-01-01

280

Polymer-capped fiber-optic Raman probe for in-vivo non-invasive Raman tomography and spectroscopy  

NASA Astrophysics Data System (ADS)

As advances in fiber optic probe design move Raman spectroscopy into the clinic, there remain important practical problems. Most in-vivo non-invasive applications employ specialized fiber optic probes. Much effort has been devoted to minimizing Raman and fluorescence background from fiber. Less attention has been paid to the need to generate reference Raman signals proportional to delivered laser power without direct measurement of tissue albedo. Knowledge of laser power is needed for quantification of changes in tissue composition. The need is especially acute in diffuse Raman tomography, where accurate modeling of light transport through the tissue is required for accurate reconstruction of subsurface features. We describe a fiber optic probe that incorporates a transparent polymer cap at the end of each excitation fiber. As laser light propagates through the cap it generates Raman bands whose intensity can directly measure power delivered to the tissue of interest. Our first implementation uses a fluorinated ethylene-propylene copolymer (FEP) cap that is attached to the ferrule at the distal (delivery) end of each excitation fiber. FEP is transparent and functions as a waveguide with only a small insertion loss, about 5%. Importantly, there are few overlaps between the Raman bands of FEP and the bands of tissue constituents. The cap increases the diameter of the structure in contact with the specimen, but with extensive photon diffusion this makes little difference in performance. We present here latest non-invasive bone spectroscopy results with the calibrator. In addition, extensive enhancement of the calibration signal using a fluorocarbon optical fiber is discussed.

Okagbare, Paul I.; Morris, Michael D.

2012-02-01

281

Mix and match: enhanced Raman spectroscopy instrumentation in field applications  

NASA Astrophysics Data System (ADS)

We present Raman spectroscopy analysis on laboratory and field sample analysis on several expeditions. Our measurements in mineral and organic composition have demonstrated that both mineral and organic species in low concentrations can be identified with Raman spectroscopy with no sample preparations and without instrument probe contact to the samples. Our laboratory studies on cyanobacterial biomat, and Mojave Desert rocks have demonstrated the promising potential for Raman spectroscopy as a nondestructive, in situ, high throughput detection technique, as well as a desirable active remote sensing tool for future planetary and space missions.

Chen, Bin; Cabrol, Nathalie; McKay, Christopher P.; Shi, Chao; Gu, Claire; Newhouse, Rebecca; Zhang, Jin; Lam, Tuling; Pei, Qibing

2008-08-01

282

Sensitivity of Raman spectroscopy to normal patient variability  

NASA Astrophysics Data System (ADS)

Many groups have used Raman spectroscopy for diagnosing cervical dysplasia; however, there have been few studies looking at the effect of normal physiological variations on Raman spectra. We assess four patient variables that may affect normal Raman spectra: Race/ethnicity, body mass index (BMI), parity, and socioeconomic status. Raman spectra were acquired from a diverse population of 75 patients undergoing routine screening for cervical dysplasia. Classification of Raman spectra from patients with a normal cervix is performed using sparse multinomial logistic regression (SMLR) to determine if any of these variables has a significant effect. Results suggest that BMI and parity have the greatest impact, whereas race/ethnicity and socioeconomic status have a limited effect. Incorporating BMI and obstetric history into classification algorithms may increase sensitivity and specificity rates of disease classification using Raman spectroscopy. Studies are underway to assess the effect of these variables on disease.

Vargis, Elizabeth; Byrd, Teresa; Logan, Quinisha; Khabele, Dineo; Mahadevan-Jansen, Anita

2011-11-01

283

Structure and property investigations of TDO in aqueous phase by density functional theory, UV absorption, and Raman spectroscopy.  

PubMed

Density functional theory, UV absorption, and Raman spectroscopy are used to investigate the structure and properties of TDO in aqueous solution. The equilibrium structures, UV absorption spectra, interaction energies, and Raman spectroscopy data of TDO, AIMSA, and 12 TDO or AIMSA clusters are calculated. Raman spectroscopy experiments are carried out by 488 and 208 nm laser excitation. The Raman spectra of TDO in solid and aqueous phases have been compared, and the most possible structure for TDO in aqueous phase was deduced from analysis of the DFT calculations for the examined models, the experimental UV absorption spectrum, and Raman spectra of TDO. The interaction energy results show that TDO's solubility in water is originated from the TDO-water cyclic oligomer. The calculated UV absorption and Raman spectra of the I2·2H2O-cyc cluster model agree with the experimental results of TDO in aqueous solution very well. PMID:24712643

Shao, Jianzhong; Liu, Xiaoyun; Chen, Pin; Wu, Qiuxia; Zheng, Xuming; Pei, Kemei

2014-05-01

284

Femtosecond Coherent Anti-Stokes Raman Spectroscopy (CARS) As Next Generation Nonlinear LIDAR Spectroscopy and Microscopy  

SciTech Connect

Nonlinear spectroscopy using coherent anti-Stokes Raman scattering and femtosecond laser pulses has been successfully developed as powerful tools for chemical analysis and biological imaging. Recent developments show promising possibilities of incorporating CARS into LIDAR system for remote detection of molecular species in airborne particles. The corresponding theory is being developed to describe nonlinear scattering of a mesoscopic particle composed of complex molecules by laser pulses with arbitrary shape and spectral content. Microscopic many-body transform theory is used to compute the third order susceptibility for CARS in molecules with known absorption spectrum and vibrational modes. The theory is combined with an integral scattering formula and Mie-Lorentz formulae, giving a rigorous formalism which provides powerful numerical experimentation of CARS spectra, particularly on the variations with the laser parameters and the direction of detection.

Ooi, C. H. Raymond [School of Engineering, Monash University, Jalan Lagoon Selatan, Bandar Sunway, 46150 Selangor DarulEhsan, Malaysia and Department of Physics, Korea University, Anam-dong, Seongbuk-gu, Seoul, 136-713 (Korea, Republic of)

2009-07-10

285

Laser biomodulation in bone implants: a Raman spectral study  

NASA Astrophysics Data System (ADS)

Healing is important for the success of the insertion of implants and for treating traumatic or pathologic injuries of the bone. Lasertherapy has been suggested as a mean of improving bone healing. Near infrared Raman spectroscopy was used to assess the amount of both inorganic and organic components of irradiated and control bone around dental implants inserted in to the tibia. Fourteen rabbits received a titanium implant on the tibia; eight of them were irradiated with ?830nm laser (Thera Lase, DMC, Sao Carlos, SP, Brazil, 21.5 J/cm2, 10mW, spot size 0.60mm) and six acted as controls. The animals were sacrificed 15, 30 and 45 days after the surgery, and specimens were prepared for Raman spectroscopy, which was collected at every four points from each three thirds of the bone around the implants. The results showed significant differences in the concentration of inorganic components in irradiated specimens between 15 and 30days (p < 0.05), 15 and 45 (p < 0.01); between irradiated and controls 30 and 45 days after surgery (p <0.01). Concentration of organic components was also significantly different between irradiated and controls in periods of 30 to 45 days after surgery. It is concluded that LLLT does improve bone healing and Raman Spectroscopy can safely assess this.

Barbosa Lopes, Cibelle; Sathaiah, Sokki; Barbosa Pinheiro, Antônio L.; Duarte, Janaína; Martins, Maria C.

2003-06-01

286

[Preliminary study on identification of oil products using laser-Raman fingerprint spectrum].  

PubMed

Laser-Raman spectroscopy technology was used for measuring and analyzing properties of oil products. Through comparing with the Raman shifts and relative Raman intensity ratios of the main fingerprint peaks, different kinds of oil products were identified successfully. Furthermore, the Raman spectra of the same type of petroleum products obtained from different private gas stations were measured and the petroleum qualities were detected. The favorable results were obtained in both oil identification and quality test. The present work provides a feasible method for quick, sensitive and nondestructive identification of oil products. PMID:22497144

Lou, Ting-ting; Wang, Yun-qing; Li, Jin-hua; Sun, Pei-yan; Feng, Wei-wei; Gao, Zhen-hui; Chen, Ling-xin

2012-01-01

287

Noninvasive detection of concealed liquid explosives using Raman spectroscopy.  

PubMed

We present a Raman spectroscopic method for the noninvasive detection of liquid explosives within bottles, and other packaging, of substantially higher sensitivity and wider applicability than that currently available via conventional Raman spectroscopy. The approach uses a modification of the spatially offset Raman spectroscopy (SORS) concept, which permits the interrogation of a wide range of containers, including transparent, colored, and diffusely scattering plastic and glass beverage, medicine, and cosmetic bottles, with no change in experimental geometry. The enhanced sensitivity is achieved by the technique's inherent ability to effectively suppress fluorescence and Raman contributions originating from the wall of the container. The application is demonstrated on the noninvasive detection of hydrogen peroxide solution, a critical component of a number of liquid explosives. In contrast to conventional Raman spectroscopy, the modified SORS concept enables the detection of concealed hydrogen peroxide solution in all the studied cases. PMID:17880183

Eliasson, C; Macleod, N A; Matousek, P

2007-11-01

288

High-pressure Raman spectroscopy of phase change materials  

NASA Astrophysics Data System (ADS)

We used high-pressure Raman spectroscopy to study the evolution of vibrational frequencies of the phase change materials (PCMs) Ge2Sb2Te5, GeSb2Te4, and SnSb2Te4. We found that the critical pressure for triggering amorphization in the PCMs decreases with increasing vacancy concentration, demonstrating that the presence of vacancies, rather than differences in the atomic covalent radii, is crucial for pressure-induced amorphization in PCMs. Compared to the as-deposited amorphous phase, the pressure-induced amorphous phase has a similar vibrational spectrum but requires much lower laser power to transform into the crystalline phase, suggesting different kinetics of crystallization, which may have implications for applications of PCMs in non-volatile data storage.

Hsieh, Wen-Pin; Zalden, Peter; Wuttig, Matthias; Lindenberg, Aaron M.; Mao, Wendy L.

2013-11-01

289

Visible and UV coherent Raman spectroscopy of dipicolinic acid  

PubMed Central

We use time-resolved coherent Raman spectroscopy to obtain molecule-specific signals from dipicolinic acid (DPA), which is a marker molecule for bacterial spores. We use femtosecond laser pulses in both visible and UV spectral regions and compare experimental results with theoretical predictions. By exciting vibrational coherence on more than one mode simultaneously, we observe a quantum beat signal that can be used to extract the parameters of molecular motion in DPA. The signal is enhanced when an UV probe pulse is used, because its frequency is near-resonant to the first excited electronic state of the molecule. The capability for unambiguous identification of DPA molecules will lead to a technique for real-time detection of spores.

Pestov, Dmitry; Zhi, Miaochan; Sariyanni, Zoe-Elizabeth; Kalugin, Nikolai G.; Kolomenskii, Alexandre A.; Murawski, Robert; Paulus, Gerhard G.; Sautenkov, Vladimir A.; Schuessler, Hans; Sokolov, Alexei V.; Welch, George R.; Rostovtsev, Yuri V.; Siebert, Torsten; Akimov, Denis A.; Graefe, Stefanie; Kiefer, Wolfgang; Scully, Marlan O.

2005-01-01

290

Chromosomal analysis and identification based on optical tweezers and Raman spectroscopy  

NASA Astrophysics Data System (ADS)

The ability to identify specific chromosomes with certainty has been established by the development of several cytogenetic techniques based on staining. Here, we report the use of a new optical technique, laser tweezers and Raman spectroscopy (LTRS), to capture and manipulate chromosomes in order to obtain their spectral patterns for molecular analysis without the need for staining. The purpose of this study was to obtain Raman spectroscopy patterns for chromosomes number 1, 2, and 3 and to test if the Raman spectroscopy pattern could be used to distinguish these three chromosomes. In our experiment, optical tweezers were used to capture the individual chromosomes and the Raman spectral patterns were collected for the trapped chromosomes. Then, the captured chromosome was manipulated with the optical tweezers and moved to another chamber through a micro - channel, in which the chromosomes were G banded for positive identification as chromosome number 1, 2, or 3. Generalized discriminate analysis (GDA) was used to compare the Raman signatures. This analysis revealed that chromosomes 1, 2, and 3 could be distinguished and identified based on their Raman spectra. Development of this approach will lead to more rapid automatic methods for chromosome analysis and identification without the use of prior staining. Moreover, the Raman spectral patterns may lend themselves to more detailed analysis of chromosomal structure than is currently available with standard staining protocols. Such analysis may some day be useful for rapid, automated screening and diagnosis for certain cancers.

Ojeda, Jenifer F.; Xie, Changan; Li, Yong-Qing; Bertrand, Fred E.; Wiley, John; McConnell, Thomas J.

2006-06-01

291

Configurable three-wavelength Raman fiber laser for Raman amplification and dynamic gain flattening  

Microsoft Academic Search

A three-wavelength Raman fiber laser is presented that is suitable for the generation of a flattened Raman gain curve over a broad range of extended telecommunications bandwidths. This laser utilizes an 1100-nm Yb-doped cladding pumped fiber laser and a cascaded Raman resonator to generate output radiation at 1427, 1454, and 1480 nm. The slope efficiency for conversion from the 1100-

M. D. Mermelstein; C. Headley; J.-C. Bouteiller; P. Steinvurzel; C. Horn; K. Feder; B. J. Eggleton

2001-01-01

292

Coherent Raman spectroscopy with frequency-shifted and shaped pulses from a photonic-crystal fiber  

NASA Astrophysics Data System (ADS)

We demonstrate spectroscopy of coherent anti-Stokes Raman scattering using a frequency-shifted and pulse-shaped output of photonic-crystal fibers pumped by amplified femtosecond Cr: forsterite laser pulses. A dyad of chirped pulses produced by the photonic-crystal fiber with a specially designed dispersion profile are combined with the second-harmonic output of the Cr: forsterite laser, to coherently probe a doublet of Raman resonances in the nonlinear response of a polyvinyl pyrrolidone film, used as a test object.

Ivanov, A. A.; Linik, Ya. M.; Akimov, D. A.; Alfimov, M. V.; Siebert, T.; Kiefer, W.; Zheltikov, A. M.

2006-01-01

293

Imaging of the Ferroelectric Domain Structures by Confocal Raman Spectroscopy  

Microsoft Academic Search

Confocal Raman spectroscopy was performed as an archetype imaging method to study the ferroelectric domain structure of periodically poled lithium niobate. More precisely, the linkage out of spatial resolution and spectral information proved itself as very useful. Here a specific modulation of the Raman lines by the local variation of polarity and a non-symmetric measuring-signal across the domain structure were

Gerhard Berth; Wjatscheslaw Hahn; Volker Wiedemeier; Artur Zrenner; Simone Sanna; Wolf Gero Schmidt

2011-01-01

294

FOURIER TRANSFORM RAMAN SPECTROSCOPY OF KAOLINITE, DICKITE AND HALLOYSITE  

Microsoft Academic Search

The vibrational modes of clay minerals are uniquely accessible to FT Raman spectroscopy, but this potentially powerful technique has found limited application to the study of clay mineral structure. Raman spectra in the 50 to 3800 cm-t region were obtained for a number of kandite clays. The kandite clay minerals are characterised by relatively intense bands centred at 142.7 cm

L. FROST

295

Raman Spectroscopy and Microscopic Raman Imaging with Applications of Volume Holographic Optical Elements  

Microsoft Academic Search

Holographic optical elements are crucial for the development of compact and efficient Raman spectroscopic instrumentation. Holographic optics allow direct coupling of a single-stage spectrograph to a Raman microprobe. The high transmission efficiency and narrow rejection-band characteristics of the holographic beam splitter provide efficient use of low power lasers, while allowing acquisition of low-frequency Raman spectra. The holographic notch filter and

David Mark Pallister

1994-01-01

296

The Examination of Synthetic Organic Pigments in Modern Works of Art by Raman Microscopy and Laser Desorption Ionziation Mass Spectrometry  

NASA Astrophysics Data System (ADS)

Raman spectroscopy in combination with laser desorption ionization mass spectrometry was used to examine samples from modern works of art by artists including Mark Rothko, Barnett Newman, and José de Rivera to identify the pigments present.

Lomax, S. Q.; Lomax, J. F.; De-Luca Westrate, A.

2014-06-01

297

Raman Spectroscopy and Microscopic Raman Imaging with Applications of Volume Holographic Optical Elements.  

NASA Astrophysics Data System (ADS)

Holographic optical elements are crucial for the development of compact and efficient Raman spectroscopic instrumentation. Holographic optics allow direct coupling of a single-stage spectrograph to a Raman microprobe. The high transmission efficiency and narrow rejection-band characteristics of the holographic beam splitter provide efficient use of low power lasers, while allowing acquisition of low-frequency Raman spectra. The holographic notch filter and holographic beamsplitter are essential tools for microscopic Raman imaging. Holographic transmission gratings used in an axial transmissive spectrograph provide high efficiency and low f/n operation. When coupled to a Raman microprobe, this single stage spectrograph can deliver converter-limited Raman signal in seconds. The capability of a matched-pair of holographic transmission gratings was explored as a filter device for Raman imaging. Without optimization, transmission efficiencies of 70% were observed throughout the visible light region and band passes of about 300 cm^{-1 }. This filter device allowed microscopic imaging of samples using isolated Raman bands or fluorescence signal. The echo in transformed images from the Hadamard transform Raman imaging microscope were found to originate from diffraction of light from the Hadamard mask and thermal instability of the optical system. Instabilities of the on-board CCD detector amplifier was shown to be a source of flicker noise. The depth of field characteristics of the Hadamard transform Raman microscope were experimentally determined. A universal illumination method was demonstrated for filter-based Raman imaging. The effects of coherent illumination and quasi-incoherent illumination on microscopic Raman image resolution is experimentally demonstrated. The illumination methods developed in this work improved the quality of our Raman imaging and were crucial to the success of digital confocal Raman imaging. Applications were developed which demonstrate the benefits of the digital confocal Raman microscopy. Digital confocal image restoration techniques and extended field visualization of 3D Raman images were demonstrated.

Pallister, David Mark

298

Raman Spectroscopy for the Investigation of Carbon Based Black Pigments  

NASA Astrophysics Data System (ADS)

Carbon based black pigments play an important role among artists' materials. The disordered structure of these materials is investigated by means of Raman spectroscopy, which helps in the comprehension of their production processes.

Coccato, A.; Jehlicka, J.; Moens, L.; Vandenabeele, P.

2014-06-01

299

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

PubMed

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. PMID:19084470

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

2009-08-01

300

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

NASA Astrophysics Data System (ADS)

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 10× beam expander to a 529-?m 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 ?m 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.

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

2009-08-01

301

ExoMars Raman laser spectrometer breadboard overview  

NASA Astrophysics Data System (ADS)

The Raman Laser Spectrometer (RLS) is one of the Pasteur Payload instruments, within the ESA's Aurora Exploration Programme, ExoMars mission. The RLS Instrument will perform Raman spectroscopy on crushed powdered samples deposited on a small container after crushing the cores obtained by the Rover's drill system. In response to ESA requirements for delta-PDR to be held in mid 2012, an instrument BB programme has been developed, by RLS Assembly Integration and Verification (AIV) Team to achieve the Technology Readiness level 5 (TRL5), during last 2010 and whole 2011. Currently RLS instrument is being developed pending its CoDR (Conceptual Design Revision) with ESA, in October 2011. It is planned to have a fully operative breadboard, conformed from different unit and sub-units breadboards that would demonstrate the end-to-end performance of the flight representative units by 2011 Q4.

Díaz, E.; Moral, A. G.; Canora, C. P.; Ramos, G.; Barcos, O.; Prieto, J. A. R.; Hutchinson, I. B.; Ingley, R.; Colombo, M.; Canchal, R.; Dávila, B.; Manfredi, J. A. R.; Jiménez, A.; Gallego, P.; Pla, J.; Margoillés, R.; Rull, F.; Sansano, A.; López, G.; Catalá, A.; Tato, C.

2011-09-01

302

Optical nanocrystallography with tip-enhanced phonon Raman spectroscopy  

Microsoft Academic Search

Conventional phonon Raman spectroscopy is a powerful experimental technique for the study of crystalline solids that allows crystallography, phase and domain identification on length scales down to ~1 µm. Here we demonstrate the extension of tip-enhanced Raman spectroscopy to optical crystallography on the nanoscale by identifying intrinsic ferroelectric domains of individual BaTiO3 nanocrystals through selective probing of different transverse optical

Samuel Berweger; Catalin C. Neacsu; Yuanbing Mao; Hongjun Zhou; Stanislaus S. Wong; Markus B. Raschke

2009-01-01

303

On the Contribution of Raman Spectroscopy to Forensic Science  

NASA Astrophysics Data System (ADS)

Raman spectroscopy has only recently sparked interest from forensic laboratories. The Raman technique has demonstrated important advantages such as its nondestructive nature, its fast analysis time, and especially the possibility of performing microscopical in situ analyses. In forensic applications, it is a versatile technique that covers a wide spectrum of substances such as trace evidence, illicit drugs and inks. An overview of the recent developments of Raman spectroscopy in forensic science will be discussed. Also, the requirements for an analytical technique for the examination of physical evidence will be described. Examples of casework will be depicted.

Buzzini, Patrick; Massonnet, Genevieve

2010-08-01

304

Polarization Raman spectroscopy of GaN nanorod bundles  

SciTech Connect

We performed polarization Raman spectroscopy on single wurtzite GaN nanorod bundles grown by plasma-assisted molecular beam epitaxy. The obtained Raman spectra were compared with those of GaN epilayer. The spectral difference between the GaN nanorod bundles and epilayer reveals the relaxation of Raman selection rules in these GaN nanorod bundles. The deviation of polarization-dependent Raman spectroscopy from the prediction of Raman selection rules is attributed to both the orientation of the crystal axis with respect to the polarization vectors of incident and scattered light and the structural defects in the merging boundary of GaN nanorods. The presence of high defect density induced by local strain at the merging boundary was further confirmed by transmission electron microscopy. The averaged defect interspacing was estimated to be around 3 nm based on the spatial correlation model.

Tite, T.; Lee, C. J.; Chang, Y.-M. [Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan (China)

2010-08-15

305

Assessment of sensitivity advances in near-field Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Near-field Raman spectroscopy can be used to obtain images with both chemical specificity and the subwavelength spatial resolution of near-field scanning optical microscopy. In the absence of signal intensification factors, such as `surface enhancement' or electronic resonance in the specimen, Raman scattering suffers from a small cross section ((sigma) equals 10-28 cm2 to 10-31 cm2). Since most reports of Raman-NSOM to date involve exploitation of a specimen-specific intensification, an assessment of the general applicability of Raman-NSOM to a wider variety of `un-enhanced' samples is of great interest. We report here on several approaches to increasing the sensitivity of near- field Raman spectroscopy that do not rely on specimen properties. The use of chemically etched aperture probes as an illumination source has been investigated and compared to probes fabricated by the traditional heat and pull method.

Michaels, Chris A.; Dentinger, Claire E.; Richter, Lee J.; Chase, D. B.; Cavanagh, Richard R.; Stranick, Stephan J.

2000-09-01

306

Quantitative Raman spectroscopy in turbid media  

NASA Astrophysics Data System (ADS)

Intrinsic Raman spectra of biological tissue are distorted by the influences of tissue absorption and scattering, which significantly challenge signal quantification. A combined Raman and spatially resolved reflectance setup is introduced to measure the absorption coefficient ?a and the reduced scattering coefficient ?s' of the tissue, together with the Raman signals. The influence of ?a and ?s' on the resonance Raman signal of ?-carotene is measured at 1524 cm-1 by tissue phantom measurements and Monte Carlo simulations for ?a=0.01 to 10 mm-1 and ?s'=0.1 to 10 mm-1. Both methods show that the Raman signal drops roughly proportional to 1/?a for ?a>0.2 mm-1 in the measurement geometry and that the influence of ?s' is weaker, but not negligible. Possible correction functions dependent on the elastic diffuse reflectance are investigated to correct the Raman signal for the influence of ?a and ?s', provided that ?a and ?s' are measured as well. A correction function based on the Monte Carlo simulation of Raman signals is suggested as an alternative. Both approaches strongly reduce the turbidity-induced variation of the Raman signals and allow absolute Raman scattering coefficients to be determined.

Reble, Carina; Gersonde, Ingo; Andree, Stefan; Eichler, Hans Joachim; Helfmann, Jürgen

2010-05-01

307

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

NASA Astrophysics Data System (ADS)

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.

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

2012-05-01

308

Evaluation of Raman spectroscopy for the trace analysis of biomolecules for Mars exobiology  

NASA Astrophysics Data System (ADS)

Raman spectroscopy is an ideal technique for the identification of biomolecules and minerals for astrobiological applications. Raman spectroscopic instrumentation has been shown to be potentially valuable for the in-situ detection of spectral biomarkers originating from rock samples containing remnants of terrestrial endolithic colonisation. Within the future payloads designed by ESA and NASA for several missions focussing on life detection on Mars, Raman spectroscopy has been proposed as an important non-destructive analytical tool for the in-situ identification of organic compounds relevant to life detection on planetary and moon surfaces or near sub-surfaces. Portable Raman systems equipped with 785 nm lasers permit the detection of pure organic minerals, aminoacids, carboxylic acids, as well as NH-containing compounds outdoors at -20°C and at an altitude of 3300 m. A potential limitation for the use of Raman spectroscopic techniques is the detection of very low amounts of biomolecules in rock matrices. The detection of beta-carotene and aminoacids has been achieved in the field using a portable Raman system in admixture with crystalline powders of sulphates and halite. Relatively low detection limits less than 1 % for detecting beta-carotene, aminoacids using a portable Raman system were obtained analysing traces of these compounds in crystalline powders of sulphates and halite. Laboratory systems permit the detection of these biomolecules at even lower concentrations at sub-ppm level of the order of 0.1 to 1 mg kg-1. The comparative evaluation of laboratory versus field measurements permits the identification of critical issues for future field applications and directs attention to the improvements needed in the instrumentation . A comparison between systems using different laser excitation wavelengths shows excellent results for 785 nm laser excitation . The results of this study will inform the acquisition parameters necessary for the deployment of robotic miniaturised Raman spectrosocpic instrumentation intended for the detection of spectral signatures of extant or relict life on Mars.

Jehlicka, Jan; Edwards, Howell G. M.; Vitek, Petr; Culka, Adam

2010-05-01

309

Raman spectroscopy for forensic analysis of inks in questioned documents.  

PubMed

The methods for perpetrating forgery and alteration of documents are becoming increasingly more sophisticated. Forensic examinations of questioned documents routinely involve physical and chemical analysis of inks. Raman spectroscopy is a very attractive technique for ink analysis because it combines chemical selectivity with ease and fast analysis and it does not require sample preparation nor leads to destruction of the evidence. However, some limitations of this technique include low sensitivity and the overwhelming phenomenon of fluorescence, which can be solved by resonance Raman spectroscopy and surface-enhanced Raman spectroscopy. This article aims to demonstrate the great potential of the Raman-based techniques by providing an overview of their application to forensic examinations of ink evidence from pens and printers. Moreover, it is also addressed the chemistry of ink-paper interactions and the problematic of intersecting lines. PMID:24053882

Braz, André; López-López, Maria; García-Ruiz, Carmen

2013-10-10

310

Nd:SrWO4 Raman laser  

NASA Astrophysics Data System (ADS)

Properties of the laser operation and simultaneously stimulated Raman scattering in the new SRS-active neodymium doped SrWO4 crystal coherently end-pumped by alexandrite 752 nm laser radiation were investigated. The maximum generated energy 90 mJ from the free-running Nd3+:SrWO4 laser at 1057 nm wavelength was obtained with the output coupler reflectivity 52%. The slope efficiency reached s = 0.52, the beam characteristic parameters M2 and divergence q were 2.5 +/- 0.1, and 1.5 +/- 0.1 mrad, respectively. Maximal output energy of 1.46 mJ for the fundamental wavelength was obtained for Q-switched Nd3+:SrWO4 oscillator with a double Fabry-Perrot as the output coupler (R = 48%), and with the 5% initial transmission of LiF:F2- saturable absorber. Up to 0.74 mJ energy was registered at the first Stokes frequency. The pulse duration was 5 ns and 2.4 ns for the fundamental and Stokes radiation, respectively. The energy of 1.25 mJ at 1170 nm was obtained for closed Raman resonator with special mirrors. For the case of mode-locking, two dye saturable absorbers (ML51 dye in dichlorethan and 3955 dye in ethanol) were used and SRS radiation in the form of pulse train was observed. The influence of the various Raman laser output couplers reflectivity as well as the initial transmissions of passive absorbers were investigated with the goal of the output energy maximization at the Stokes wavelength. In the output, the total measured energy was 1.8 mJ (for ML51 dye) and 2.4 mJ (for 3955 dye). The SRS output at 1170 nm was approximately 20% of total energy.

Jelinkova, Helena; Sulc, Jan; Doroschenko, Maxim E.; Skornyakov, Vadim V.; Kravtsov, Sergey B.; Basiev, Tasoltan T.; Zverev, Peter G.

2004-09-01

311

In situ cell cycle phase determination using Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Raman spectroscopy is a powerful tool for analysis of the chemical composition in living tissue and cells without destructive processes such as fixation, immunostaining, and fluorescence labeling. Raman microspectroscopic technique enables us to obtain a high quality spectrum from a single living cell. We demonstrated in situ cell cycle analysis with Raman microspectroscopy with the excitation wavelength of 532 nm. Cell cycle phases, G0/G1 and G2/M were able to be identified in the present study. The result of in situ Raman analysis was evaluated with flow cytometry analysis. Although the Raman spectra of living cells showed complex patterns during cell cycle, several Raman bands could be useful as markers for the cell cycle identification. A single cell analysis using Raman microspectroscopy predicted a possibility to observe directly molecular dynamics intracellular molecules of proteins, lipids and nucleic acids. Our current study focused on cytoplasm region and resonant Raman signals of cytochrome c in mitochondrion, and discussed how the Raman signals from cellular components contribute to the Raman spectral changes in cell cycle change in the human living cell (lung cancer cell).

Oshima, Yusuke; Takenaka, Tatsuji; Sato, Hidetoshi; Furihata, Chie

2010-02-01

312

Mode-dependent dispersion in Raman line shapes: Observation and implications from ultrafast Raman loss spectroscopy  

SciTech Connect

Ultrafast Raman loss spectroscopy (URLS) enables one to obtain the vibrational structural information of molecular systems including fluorescent materials. URLS, a nonlinear process analog to stimulated Raman gain, involves a narrow bandwidth picosecond Raman pump pulse and a femtosecond broadband white light continuum. Under nonresonant condition, the Raman response appears as a negative (loss) signal, whereas, on resonance with the electronic transition the line shape changes from a negative to a positive through a dispersive form. The intensities observed and thus, the Franck-Condon activity (coordinate dependent), are sensitive to the wavelength of the white light corresponding to a particular Raman frequency with respect to the Raman pump pulse wavelength, i.e., there is a mode-dependent response in URLS.

Umapathy, S.; Mallick, B.; Lakshmanna, A. [Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560012 (India)

2010-07-14

313

Mode-dependent dispersion in Raman line shapes: Observation and implications from ultrafast Raman loss spectroscopy  

NASA Astrophysics Data System (ADS)

Ultrafast Raman loss spectroscopy (URLS) enables one to obtain the vibrational structural information of molecular systems including fluorescent materials. URLS, a nonlinear process analog to stimulated Raman gain, involves a narrow bandwidth picosecond Raman pump pulse and a femtosecond broadband white light continuum. Under nonresonant condition, the Raman response appears as a negative (loss) signal, whereas, on resonance with the electronic transition the line shape changes from a negative to a positive through a dispersive form. The intensities observed and thus, the Franck-Condon activity (coordinate dependent), are sensitive to the wavelength of the white light corresponding to a particular Raman frequency with respect to the Raman pump pulse wavelength, i.e., there is a mode-dependent response in URLS.

Umapathy, S.; Mallick, B.; Lakshmanna, A.

2010-07-01

314

Method And System For Examining Biological Materials Using Low Power Cw Excitation Raman Spectroscopy.  

DOEpatents

A method and system for examining biological materials using low-power cw excitation Raman spectroscopy. A low-power continuous wave (cw) pump laser beam and a low-power cw Stokes (or anti-Stokes) probe laser beam simultaneously illuminate a biological material and traverse the biological material in collinearity. The pump beam, whose frequency is varied, is used to induce Raman emission from the biological material. The intensity of the probe beam, whose frequency is kept constant, is monitored as it leaves the biological material. When the difference between the pump and probe excitation frequencies is equal to a Raman vibrational mode frequency of the biological material, the weak probe signal becomes amplified by one or more orders of magnitude (typically up to about 10.sup.4 -10.sup.6) due to the Raman emission from the pump beam. In this manner, by monitoring the intensity of the probe beam emitted from the biological material as the pump beam is varied in frequency, one can obtain an excitation Raman spectrum for the biological material tested. The present invention may be applied to in the in vivo and/or in vitro diagnosis of diabetes, heart disease, hepatitis, cancers and other diseases by measuring the characteristic excitation Raman lines of blood glucose, cholesterol, serum glutamic oxalacetic transaminase (SGOT)/serum glutamic pyruvic transaminase (SGPT), tissues and other corresponding Raman-active body constituents, respectively.

Alfano, Robert R. (Bronx, NY); Wang, Wubao (Flushing, NY)

2003-05-06

315

Raman forward scattering of chirped laser pulses  

SciTech Connect

Raman scattering of a high-intensity, short duration, frequency-chirped laser pulse propagating in an underdense plasma is examined. The growth of the direct forward scattered light is calculated for a laser pulse with a linear frequency chirp in various spatio-temporal regimes. This includes a previously undescribed regime of strongly-coupled four-wave nonresonant interaction, which is important for relativistic laser intensities. In all regimes of forward scattering, it is shown that the growth rate increases (decreases) for positive (negative) frequency chirp. The effect of chirp on the growth rate is relatively minor, i.e., a few percent chirp yields few percent changes in the growth rates. Numerical solutions based on fully nonlinear cold Maxwell-fluid model are presented which confirm analytical predictions. Relation of these results to recent experiments is discussed.

Schroeder, C.B.; Esarey, E.; Shadwick, B.A.; Leemans, W.P.

2002-12-05

316

Random fiber Bragg grating Raman fiber laser.  

PubMed

We demonstrate for the first time to our knowledge a Raman random fiber laser (RRFL) based on a long random fiber Bragg grating (RFBG-RRFL). Unlike other recently demonstrated random fiber lasers that rely on incoherent Rayleigh scattering feedback, the present scheme uses randomly distributed phase shifts inside a fiber-meter long Bragg grating as a random coherent feedback mechanism. The laser is pumped at 1480 nm and emits a CW signal at 1576 nm. The emission spectrum is dependent on pump intensity and is shown to exhibit single and multi-mode characteristics. The RRFL shows a relatively low threshold (2.2 W) and a ?430 kHz FWHM linewidth. PMID:24784095

Gagné, Mathieu; Kashyap, Raman

2014-05-01

317

Theory of femtosecond coherent anti-Stokes Raman scattering spectroscopy of gas-phase transitions  

NASA Astrophysics Data System (ADS)

A theoretical analysis of coherent anti-Stokes Raman scattering (CARS) spectroscopy of gas-phase resonances using femtosecond lasers is performed. The time-dependent density matrix equations for the femtosecond CARS process are formulated and manipulated into a form suitable for solution by direct numerical integration (DNI). The temporal shapes of the pump, Stokes, and probe laser pulses are specified as an input to the DNI calculations. It is assumed that the laser pulse shapes are 70 fs Gaussians and that the pulses are Fourier-transform limited. A single excited electronic level is defined as an effective intermediate level in the Raman process, and transition strengths are adjusted to match the experimental Raman polarizability. The excitation of the Raman coherence is investigated for different Q-branch rotational transitions in the fundamental 2330 cm-1 band of diatomic nitrogen, assuming that the pump and Stokes pulses are temporally overlapped. The excitation process is shown to be virtually identical for transitions ranging from Q(2) to Q(20). The excitation of the Raman coherences is also very efficient; for laser irradiances of 5×1017 W/m2, corresponding approximately to a 100 ?J, 70 fs pulse focused to 50 ?m, approximately 10% of the population of the ground Raman level is pumped to the excited Raman level during the impulsive pump-Stokes excitation, and the magnitude of the induced Raman coherence reaches 40% of its maximum possible value. The theoretical results are compared with the results of experiments where the femtosecond CARS signal is recorded as a function of probe delay with respect to the impulsive pump-Stokes excitation.

Lucht, Robert P.; Kinnius, Paul J.; Roy, Sukesh; Gord, James R.

2007-07-01

318

Near-infrared Raman spectroscopy for colonic cancer diagnosis  

NASA Astrophysics Data System (ADS)

This study evaluated the diagnostic ability of near-infrared (NIR) Raman spectroscopy for identifying the malignant tumors from normal and benign tissues in the colon. In this work, a rapid NIR Raman system was utilized for tissue Raman studies. A total of 105 colonic specimens were used for Raman studies, including 41 normals, 18 polyps (benign), and 46 malignant tumors (22 of moderately differentiated adenocarcinomas and 24 of poorly differentiated adenocarcinomas). The results showed that high-quality Raman spectra in the 800-1800 cm-1 range can be acquired from human colonic tissues in vitro, and Raman spectra differed significantly between normal and malignant tumor tissue. The diagnostic algorithm using the Raman intensity ratios of I1085/1445 vs. I1002/1445 can yield a diagnostic sensitivity of 100% and specificity of 96.6% for differentiation between between normal, benign and malignant colonic tissue. This work demonstrates that NIR Raman spectroscopy technique has a significant potential for the noninvasive diagnosis of colon cancer in vivo based on the evaluation of changes of molecular vibrations of biomolecules in tissue.

Huang, Zhiwei; Zheng, Wei; Colin, Sheppard

2005-08-01

319

Time-Resolved Suppression of Fluorescence in Raman Spectrometry By Continuous Wave Laser Amplitude Modulation and Phase-Sensitive Detection  

Microsoft Academic Search

Raman spectroscopy applied to biological systems is often dominated by interfering fluorescence background. In this report Raman scattering of benzene in the presence of strong fluorescence was obtained via phase sensitive detection upon sinusoidally modulating the continous wave laser beam at tens of MHz. Extended detectability of the 992 cm frequency was obtained, but the signal enhancement is greatly dependent

Arie van Hoek; Antonie J. W. G. Visser

1985-01-01

320

Remote Continuous Wave and Pulsed Laser Raman Detection of Chemical Warfare Agents Simulants and Toxic Industrial Compounds  

Microsoft Academic Search

This study describes the design, assembly, testing and comparison of two Remote Raman Spectroscopy (RRS) systems intended for standoff detection of hazardous chemical liquids. Raman spectra of Chemical Warfare Agents Simulants (CWAS) and Toxic Industrial Compounds (TIC) were measured in the laboratory at a 6.6 m source-target distance using continuous wave (CW) laser detection. Standoff distances for pulsed measurements were

William Ortiz-Rivera; Leonardo C. Pacheco-Londońo; Samuel P. Hernández-Rivera

2010-01-01

321

Use of Raman spectroscopy in a complex investigation of the firing of serpentinites  

SciTech Connect

In this work, during a study of the firing behavior of serpentinites from the Dznetygarinsk deposits, an attempt was made to carry out an analysis using Raman spectroscopy. The investigation involved the use of waste asbestos products from the Dzhetygarinsk Kustanaiasbest Combine. The study was made using a molecular-optical laser analyser. Raman spectra of the first order were obtained for specimens of starting raw material and material calcined at different temperatures. The investigation was made with back (by 180/sup 0/) scatter geometry, as indivisibly as possibly, since they were studying opaque inclusions randomly accumulated into a continuous matrix. The results showed that the form and arrangement of the inclusions in the specimen do not have any influence on the Raman spectra, since the assembled optical system completely depolarized the scattered light, and the Raman spectra of the first order contain all modes resolved by the selection rules.

Ashimov, U.B.; Arymbaev, O.Z.; Bolotov, Yu.A.; Zaretskaya, N.P.

1987-11-01

322

Collective electronic excitations in magnetically aligned single wall carbon nanotubes studied by Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Samples with magnetically aligned single wall carbon nanotubes (SWNT) have been studied by Raman spectroscopy in the low frequency spectral range: 10 - 700 cm-1. A novel Raman-active electronic collective excitation has been observed. At room temperature the excitation band is at about 30 cm-1. The band dramatically strengthens and softens down to about 15 cm-1 with sample cooling below 50 K. The polarization dependence of the Raman spectra was analyzed for laser excitation energies in resonance with electronic transitions and it was compared to that in the case of non-resonant excitation. Strong anisotropy of Raman response function of the SWNT has been observed: for polarization parallel to the direction of the nanotubes the electronic excitation band is about 4 times stronger than that for the perpendicular direction. The origin of the 1-D electronic excitation in metallic SWNT will be discussed.

Blumberg, G.; Gozar, A.; Dennis, B. S.; Sirenko, A. A.; Eklund, P. C.; Walters, D. A.; Casavant, M. J.; Schmidt, J.; Smalley, R. E.

2001-03-01

323

Remote Raman spectroscopy of minerals at elevated temperature relevant to Venus exploration  

NASA Astrophysics Data System (ADS)

We have used a remote time-resolved telescopic Raman system equipped with 532 nm pulsed laser excitation and a gated intensified CCD (ICCD) detector for measuring Raman spectra of a number of minerals at high temperature to 970 K. Remote Raman measurements were made with samples at 9-meter in side a high-temperature furnace by gating the ICCD detector with 2 micro-sec gate to minimize interference from blackbody emission from mineral surfaces at high temperature as well as interference from ambient light. A comparison of Raman spectra of gypsum (CaSO4.2H2O), dolomite (CaMg(CO3)2), and olivine (Mg2Fe2-xSiO4), as a function of temperature shows that the Raman lines remains sharp and well defined even in the high-temperature spectra. In the case of gypsum, Raman spectral fingerprints of CaSO4.H2O at 518 K were observed due to dehydration of gypsum. In the case of dolomite, partial mineral dissociation was observed at 973 K at ambient pressure indicating that some of the dolomite might survive on Venus surface that is at ~750 K and 92 atmospheric pressure. Time-resolved Raman spectra of low clino-enstatite (MgSiO3) measured at 75 mm from the sample in side the high-temperature furnace also show that the Raman lines remains sharp and well defined in the high temperature spectra. These high-temperature remote Raman spectra of minerals show that time-resolved Raman spectroscopy can be used as a potential tool for exploring Venus surface mineralogy at shorter (75 mm) and long (9 m) distances from the samples both during daytime and nighttime. The remote Raman system could also be used for measuring profiles of molecular species in the dense Venus atmosphere during descent as well as on the surface.

Sharma, Shiv K.; Misra, Anupam K.; Singh, Upendra N.

2008-12-01

324

Dynamics of intramolecular vibrational redistribution in terminal acetylene molecules studies by time-resolved Raman spectroscopy  

NASA Astrophysics Data System (ADS)

We report the first direct investigations of vibrational dynamics in isolated polyatomic molecules by means of Raman spectroscopy. A pump-probe experimental scheme is applied where laser pumping of one mode of a molecule is followed by probing its anti-Stokes Raman spectrum, so that a decrease ofRaman signal with the probe-pump delay time tells us about intramolecular vibrational redistribution (IVR) of the energy from the initially excited mode to the other modes. Experimental results for terminal acetylene molecules are presented and discussed. The principal observation is that IVR times in our studies are much shorter than those estimated previously for the same molecules from high-resolution spectroscopy ofthe cold molecular beams. We analyze this difference assuming that the rotational degrees of freedom, which are highly populated in our case of gas at room temperature, play an important role in mediating IVR in the molecules under consideration.

Malinovsky, Alexander L.; Makarov, Alexander A.; Ryabov, Evgeny A.

2006-12-01

325

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

PubMed

A microsystem light source emitting at 488 nm was tested and applied as a light source for shifted excitation resonance Raman difference spectroscopy (SERRDS). A nonlinear frequency conversion using a distributed feedback (DFB) diode laser emission at 976 nm and a periodically poled lithium niobate (PPLN) waveguide crystal was realized on a micro-optical bench with a footprint of 25 mm x 5 mm. Joint temperature management via the microbench is used for wavelength tuning. Two emission lines at 487.61 nm and 487.91 nm are used for the SERRDS experiments. The Raman spectra of the test sample polystyrene demonstrate that a laser bandpass filter did not need to be implemented. Resonance Raman spectra of Tartrazine (FD&C Yellow 5, E 102) in distilled water are presented to demonstrate the suitability of this light source for SERRDS in, e.g., food safety control. PMID:19891837

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

2009-11-01

326

Raman and Infrared Spectroscopy of Pyridine under High Pressure  

SciTech Connect

We report the structural transitions of pyridine as a function of pressure up to 26 GPa using in situ Raman spectroscopy and infrared absorption spectroscopy. By monitoring changes in the Raman shifts in the lattice region as well as the band profiles in both Raman and IR spectra, a liquid-to-solid transition at 1 GPa followed by solid-to-solid transitions at 2, 8, 11, and 16 GPa were observed upon compression. These transitions were found to be reversible upon decompression from 22 GPa. A further chemical transformation was observed when compressed beyond 22 GPa as evidenced by the substantial and irreversible changes in the Raman and infrared spectra, which could be attributed to the destruction of the ring structure. The observed transformations in pyridine were also compared to those for benzene. The similar transition sequence with well-aligned transition pressures suggests that these isoelectronic aromatics may have similar structures and stabilities under high pressure.

Zhuravlev, K.; Traikov, K; Dong, Z; Xie, S; Song, Y; Liu, Z

2010-01-01

327

Surface Raman spectroscopy as a probe of surface chemistry  

NASA Astrophysics Data System (ADS)

Unenhanced surface Raman spectroscopy has been used to study the chemistry of polymers adsorbed on solid surfaces and the chemical enhancement mechanism of surface-enhanced Raman scattering. The adsorption and reactions of the polyimide monomers pyromellitic dianhydride (PMDA) and oxydianiline on silver, copper and silicon surfaces under ultrahigh vacuum have been investigated. These include both nondissociative physisorption and dissociative chemisorption of the monomers, and the condensation polymerization to form adsorbed polyimide. The intermediate polyamic acid is detected for the first time in a surface experiment. PMDA adsorbed on Cu(111) shows chemical enhancement in the absence of electromagnetic enhancement. High resolution electron energy loss spectroscopy has revealed a strong charge transfer absorption near the Raman excitation frequency. This observation provides strong support for a proposed resonance Raman chemical enhancement mechanism.

Child, C. M.; Foster, Michelle; Ivanecky, J. E.; Perry, Scott S.; Campion, Alan

1995-09-01

328

Micro-Raman Spectroscopy of Atomically-Thin Graphite  

NASA Astrophysics Data System (ADS)

The unique linear energy vs. momentum relationship leads to interesting fundamental physics including massless particles studied in quantum electrodynamics, a unity tunneling paradox, and an anomalous quantum Hall effect. We will use mechanical exfoliation of highly-oriented pyrolytic graphite (HOPG) to produce single and multilayer graphene flakes on Si/S02 substrates. We will analyze the graphene using a combination of microscopy techniques including optical, micro-Raman spectroscopy, and atomic force microscopy (AFM). The Raman spectra exhibit phonon modes common to graphitic carbon, specifically known as the D, G, G'2D. Fitting the peaks with Lorentzian(s) quantifies the number of graphene layers. The peak frequency and intensity of Raman modes provides information about electron-phonon coupling and defects. We compare the Raman spectra of graphene prepared using mechanical exfoliation and CVD growth, both in contact with and suspended above substrate surfaces. Additionally, we will correlate Raman spectral maps with AFM topological contours.

Mead, Kevin; Hasslinger, John; Simpson, Jeff

2010-03-01

329

Subframe Burst Gating for Raman Spectroscopy in Combustion  

NASA Technical Reports Server (NTRS)

We describe an architecture for spontaneous Raman scattering utilizing a frame-transfer CCD sensor operating in a subframe burst-gating mode to realize time-resolved combustion diagnostics. The technique permits all-electronic optical gating with microsecond shutter speeds 5 J.Ls) without compromising optical throughput or image fidelity. When used in conjunction with a pair of orthogonally polarized excitation lasers, the technique measures single-shot vibrational Raman scattering that is minimally contaminated by problematic optical background noise.

Kojima, Jun; Fischer, David; Nguyen, Quang-Viet

2010-01-01

330

Raman spectroscopy with an integrated arrayed-waveguide grating.  

PubMed

An integrated arrayed-waveguide grating fabricated in silicon-oxynitride technology is applied to Raman spectroscopy. After its validation by reproducing the well-known spectrum of cyclohexane, polarized Raman spectra are measured of extracted human teeth containing localized initial carious lesions. Excellent agreement is obtained between the spectra of healthy and carious tooth enamel measured with our integrated device and spectra recorded using a conventional Raman spectrometer. Our results represent a step toward the realization of compact, hand-held, integrated spectrometers, e.g. for the detection of dental caries at an early stage. PMID:22139265

Ismail, N; Choo-Smith, L-P; Wörhoff, K; Driessen, A; Baclig, A C; Caspers, P J; Puppels, G J; de Ridder, R M; Pollnau, M

2011-12-01

331

Pharmaceutical Analysis from Start to Finish by Raman Spectroscopy  

NASA Astrophysics Data System (ADS)

During the past decade Raman spectroscopy has become a widely used analytical tool in the laboratory, process environment and on-line. This is largely due to the fact that virtually every chemical produces a unique Raman signature, sample preparation is generally not required, and analyses can be performed in 1 minute or less. This presentation will describe the value of fluorescent free and x-axis stable Raman spectra in confirming the identity of raw materials, tracking reaction kinetics during drug discovery and product synthesis, monitoring and controlling batch and continuous feed reactors, and determining product properties using chemometrics.

Donahue, Michael; Smith, Wayne; Patient, Michael; Farquharson, Stuart

2010-08-01

332

Determination of doping profiles on bevelled GaAs structures by Raman spectroscopy  

NASA Astrophysics Data System (ADS)

A method for determination of doping concentration profiles of GaAs multilayer structures on a bevelled surface by Raman spectroscopy is presented. By scanning the laser beam along the bevel we obtained micro-Raman spectra in different depth positions in the structure. Calculated ITO/ ILO intensities determine the doping concentration in these points for values above 3×10 16 cm -3. The results are compared with electrochemical capacitance-voltage technique and secondary ion mass spectrometry. Some specific problems are discussed.

Srnanek, R.; Kinder, R.; Sciana, B.; Radziewicz, D.; McPhail, D. S.; Littlewood, S. D.; Novotny, I.

2001-06-01

333

LIGHT INDUCED TELLURIUM ENRICHMENT ON CDZNTE CRYSTALSURFACES DETECTED BY RAMAN SPECTROSCOPY  

SciTech Connect

Synthetic CdZnTe or 'CZT' crystals can be grown under controlled conditions to produce high quality crystals to be used as room temperature radiation detectors. Even the best crystal growth methods result in defects, such as tellurium secondary phases, that affect the crystal's performance. In this study, CZT crystals were analyzed by micro Raman spectroscopy. The growth of Te rich areas on the surface was induced by low powered lasers. The growth was observed versus time with low power Raman scattering and was observed immediately under higher power conditions. The detector response was also measured after induced Te enrichment.

Hawkins, S; Eliel Villa-Aleman, E; Martine Duff, M; Douglas02 Hunter, D

2007-10-29

334

Light-Induced Tellurium Enrichment on CdZnTe Crystal Surfaces Detected by Raman Spectroscopy  

SciTech Connect

CdZnTe (CZT) crystals can be grown under controlled conditions to produce high-quality crystals to be used as room-temperature radiation detectors. Even the best crystal growth methods result in defects, such as tellurium secondary phases, that affect the crystal's performance. In this study, CZT crystals were analyzed by micro-Raman spectroscopy. The growth of Te rich areas on the surface was induced by low-power lasers. The growth was observed versus time with low-power Raman scattering and was observed immediately under higher-power conditions. The detector response was also measured after induced Te enrichment.

Hawkins, Samantha A.; Villa-Aleman, Eliel; Duff, Martine C.; Hunter, Doug B.; Burger, Arnold; Groza, Michael; Buliga, Vladimir; Black, David R. (SRNL); (NIST); (Fisk U)

2008-12-08

335

Characterisation of thermally annealed diamond like carbon (DLC) and silicon modified DLC films by Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Raman spectroscopy has been used to investigate the structural changes in thermally annealed diamond like carbon (a-C : H) and silicon modified diamond like carbon (a-C : H : Si) films prepared by plasma enhanced chemical vapour deposition (PECVD) using a 514.53 nm argon ion laser excitation. The changes in the Raman spectra of the films has been used to monitor structural modifications with increasing annealing temperature. The present investigation indicates that the rate of these structural modifications is dependent on both the annealing temperature and the negative self-bias voltage applied during the film deposition process for a fixed annealing time.

Ogwu, A. A.; Lamberton, R. W.; Morley, S.; Maguire, P.; McLaughlin, J.

1999-09-01

336

Method And System For Examining Biological Materials Using Low Power Cw Excitation Raman Spectroscopy.  

DOEpatents

A method and system for examining biological materials using low-power cw excitation Raman spectroscopy. In accordance with the teachings of the invention, a low-power continuous wave (cw) pump laser beam and a low-power cw Stokes (or anti-Stokes) probe laser beam simultaneously illuminate a biological material and traverse the biological material in collinearity. The pump beam, whose frequency is varied, is used to induce Raman emission from the biological material. The intensity of the probe beam, whose frequency is kept constant, is monitored as it leaves the biological material. When the difference between the pump and probe excitation frequencies is equal to a Raman vibrational mode frequency of the biological material, the weak probe signal becomes amplified by one or more orders of magnitude (typically up to about 10.sup.4 -10.sup.6) due to the Raman emission from the pump beam. In this manner, by monitoring the intensity of the probe beam emitted from the biological material as the pump beam is varied in frequency, one can obtain an excitation Raman spectrum for the biological material tested. The present invention may be applied to in the in vivo and/or in vitro diagnosis of diabetes, heart disease, hepatitis, cancers and other diseases by measuring the characteristic excitation Raman lines of blood glucose, cholesterol, serum glutamic oxalacetic transaminase (SGOT)/serum glutamic pyruvic tansaminase (SGPT), tissues and other corresponding Raman-active body constituents, respectively. For example, it may also be used to diagnose diseases associated with the concentration of Raman-active constituents in urine, lymph and saliva It may be used to identify cancer in the breast, cervix, uterus, ovaries and the like by measuring the fingerprint excitation Raman spectra of these tissues. It may also be used to reveal the growing of tumors or cancers by measuring the levels of nitric oxide in tissue.

Alfano, Robert R. (Bronx, NY); Wang, Wubao (Flushing, NY)

2000-11-21

337

Stability analysis of second order pulsed Raman laser in dispersion managed systems  

NASA Astrophysics Data System (ADS)

Wavelength tunable synchronous pulse sources are highly desirable for spectroscopy and optical diagnostics. The common method to generate short pulses in the fiber is the use of nonlinear induced spectral broadening which result in soliton shaping in anomalous dispersion regime. However, to generate ultra-short pulses, broadband gain mechanism is also required. In recent years, Raman fiber lasers have retrieved strong interest due to their capability of serving as pump sources in gain-flattened amplifiers for optical communication systems. The fixed-wavelength Raman lasers have been widely studied in the last years, but recently, much focus has been on the multi wavelength tunable Raman fiber lasers which generate output Stokes pulses in a broad wavelength range by so called cascaded stimulated Raman scattering. In this paper we investigate synchronous 1st and 2nd order pulsed Raman lasers that can achieve frequency spacing of up to 1000cm-1 that is highly desired for CARS microscopy. In particular, analytical and numerical analysis of pulsed stability derived for Raman lasers by using dispersion managed telecom fibers and pumped by 1530nm fiber lasers. We show the evolution of the 1st and 2nd order Stokes signals at the output for different pump power and SMF length (determines the net anomalous dispersion) combinations. We investigated the stability of dispersion managed synchronous Raman laser up to second order both analytically and numerically. The results show that the stable 2nd order Raman Stokes pulses with 0.04W to 0.1W peak power and 2ps to 3.5ps pulse width can be achieved in dispersion managed system.

Kalyoncu, Salih K.; Gao, Shiming; Tien, En-Kuang; Huang, Yuewang; Yildirim, Dogukan; Adas, Enver; Wabnitz, Stefano; Boyraz, Ozdal

2011-05-01

338

Surface-enhanced Raman spectroscopy of urine by an ingenious near-infrared Raman spectrometer  

NASA Astrophysics Data System (ADS)

This paper demonstrates the potential of an elaborately devised near-infrared Raman system in analysis of urine. The broad band in the long-wavelength region of the electronic absorption spectra of the sol with added adsorbent at certain concentrations has been explained in terms of the aggregation of the colloidal silver particles. We have reported the surface-enhanced Raman (SERS) spectra of urine, and studied the silver solution enhanced effects on the urine Raman scattering. The Raman bands of human's urine was assigned to certain molecule vibrations. We have found that different donators have dissimilar SERS of urine in different physiological condition. Comparatively few studies have explored the ability of Raman spectroscopy for the analysis of urine acid. In the present report, we investigated the ability of surface enhanced Raman spectroscopy to measure uric acid in the human urine. The results suggested that the present Raman system holds considerable promise for practical use. Practical applications such as the quantitative medical examination of urine metabolites may also be feasible in the near future.

Feng, Shangyuan; Chen, Weiwei; Li, Yongzeng; Chen, Guannan; Huang, Zufang; Liao, Xiaohua; Xie, Zhiming; Chen, Rong

2007-10-01

339

Two-dimensional Raman-terahertz spectroscopy of water  

PubMed Central

Two-dimensional Raman-terahertz (THz) spectroscopy is presented as a multidimensional spectroscopy directly in the far-IR regime. The method is used to explore the dynamics of the collective intermolecular modes of liquid water at ambient temperatures that emerge from the hydrogen-bond networks water forming. Two-dimensional Raman-THz spectroscopy interrogates these modes twice and as such can elucidate couplings and inhomogeneities of the various degrees of freedoms. An echo in the 2D Raman-THz response is indeed identified, indicating that a heterogeneous distribution of hydrogen-bond networks exists, albeit only on a very short 100-fs timescale. This timescale appears to be too short to be compatible with more extended, persistent structures assumed within a two-state model of water.

Savolainen, Janne; Ahmed, Saima; Hamm, Peter

2013-01-01

340

Detection and characterization of human tissue lesions with near-infrared Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Near infrared (NIR) Raman spectroscopy provides a powerful method for quantitative histochemistry of human tissue and disease diagnosis. The feasibility and potential of this technique for in situ histochemical analysis of human coronary artery has been demonstrated and presented in other reports from our laboratory. In this work, we review recent results obtained with the NIR Raman spectroscopy on a variety of tissue types studied at the MIT Laser Biomedical Research Center. We have collected NIR Raman spectra from colon, bladder, breast, and carotid artery. For colon, bladder and breast, consistent differences between carcinoma and normal tissue spectra were observed. For colon and bladder, the spectral differences appear to be due to an increased content of nucleic acid in carcinomas, while the spectral changes in malignant breast tissue are associated with an increase of protein content. Spectra from carotid artery have similar features as those from aorta and coronary arteries. We also show some preliminary results obtained with a NIR Raman microspectroscopy setup with 20 micron lateral resolution. The biochemical distributions for normal and diseased regions on the same tissue samples are observed. The potential of using this NIR Raman spectroscopy for detection and characterization of carcinoma and atherosclerosis, is discussed.

Feld, Michael S.; Manoharan, Ramasamy; Salenius, Juha; Orenstein-Carndona, Jacobo; Roemer, Tjeerd J.; Brennan, James F.; Dasari, Ramachandra R.; Wang, Yang

1995-05-01

341

Raman Spectroscopy: A New Proposal for the Detection of Leukemia Using Blood Samples  

SciTech Connect

The use of Raman spectroscopy to analyze blood biochemistry and hence distinguish between normal and abnormal blood was investigated. The blood samples were obtained from 6 patients who were clinically diagnosed with leukemia and 6 healthy volunteer. The imprint was put under the microscope and several points were chosen for Raman measurement. All spectra were collected at confocal Raman micro-spectroscopy (Renishaw) with NIR 830 nm laser. It is shown that the serum samples from patients with leukemia and from the control group can be discriminated when the multivariate statistical methods of principal component analysis (PCA) and linear discriminated analysis (LDA) is applied to their Raman spectra. The ratios of some band intensities were analyzed and some band ratios were significant and corresponded to proteins, phospholipids, and polysaccharides. In addition, currently the degree of damage to the bone marrow is estimated through biopsies and therefore it is a very procedure painful. The preliminary results suggest that Raman spectroscopy could be a new technique to study the bone marrow using just blood samples.

Martinez-Espinosa, J. C.; Gonzalez-Solis, J. L.; Miranda-Beltran, M. L.; Soria-Fregoso, C.; Medina-Valtierra, J.; Sanchez-Gomez, R. [Centro Universitario de Lagos, Universidad de Guadalajara Enrique Diaz de Leon S/N, Paseo de la Montana, CP 47460, Lagos de Moreno, Jalisco (Mexico); Frausto-Reyes, C. [Centro de Investigaciones en Optica, A. C. Prolongacion Constitucion 607, Fracc. Reserva Lomas Bonita, CP 20200, Aguascalientes (Mexico)

2008-08-11

342

UV Resonant Raman Spectrometer with Multi-Line Laser Excitation  

NASA Technical Reports Server (NTRS)

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

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

2013-01-01

343

Transmission resonance Raman spectroscopy: experimental results versus theoretical model calculations.  

PubMed

A laser spectroscopic technique is described that combines transmission and resonance-enhanced Raman inelastic scattering together with low laser power (< 30 mW) and good spatial resolution (< 200 ?m) as operational features. The monitoring of the transmitted inelastic scattering provides an increased signal-to-noise ratio because the low fluorescence background and, on the other hand, the resonant character of the laser excitation, leads to enhanced analytical sensitivity. The spectroscopic technique was applied to investigate the carotenoid content (specifically the ?-carotene concentration) of distinct samples that included fruits, reaching a detection limit of the order of hundreds of picograms in solid samples, which is below the level needed for typical food control analysis. Additional features of the present development are direct sampling, noninvasive character, and fast analysis that is not time consuming. From a theoretical point of view, a model for the Raman signal dependence on the sample thickness is also presented. Essentially, the model considers the sample to be homogeneous and describes the underlying physics using only three parameters: the Raman cross-section, the laser-radiation attenuation cross-section, and the Raman signal attenuation cross-section. The model was applied successfully to describe the sample-size dependence of the Raman signal in both ?-carotene standards and carrot roots. The present technique could be useful for direct, fast, and nondestructive investigations in food quality control and analytical or physiological studies of animal and human tissues. PMID:23031699

Gonzálvez, Alicia G; González Ureńa, Ángel

2012-10-01

344

Dengue blood analysis by Raman spectroscopy  

NASA Astrophysics Data System (ADS)

In this work Raman spectra of normal and dengue infected serum and whole blood were analyzed. In normal whole blood and serum characteristic peaks were observed when excited at 442 and 532 nm. In dengue whole blood and serum all peaks found to be blue shifted with reduced Raman intensity. Dengue whole blood and serum shows two peaks at 1614 and 1750 cm-1 which are due to presence of Immunoglobulin antibodies IgG and IgM. Whole study provides a route of information for diagnosis of dengue viral infection.

Rehman, A.; Anwar, S.; Firdous, S.; Ahmed, M.; Rasheed, R.; Nawaz, M.

2012-06-01

345

Trace vapour detection at room temperature using Raman spectroscopy.  

PubMed

A miniaturized flow-through system consisting of a gold coated silicon substrate based on enhanced Raman spectroscopy has been used to study the detection of vapour from model explosive compounds. The measurements show that the detectability of the vapour molecules at room temperature depends sensitively on the interaction between the molecule and the substrate. The results highlight the capability of a flow system combined with Raman spectroscopy for detecting low vapour pressure compounds with a limit of detection of 0.2 ppb as demonstrated by the detection of bis(2-ethylhexyl)phthalate, a common polymer additive emitted from a commercial polyvinyl chloride (PVC) tubing at room temperature. PMID:24588003

Chou, Alison; Radi, Babak; Jaatinen, Esa; Juodkazis, Saulius; Fredericks, Peter M

2014-04-21

346

Characterization of CO/sub 2/-CH/sub 4/-H/sub 2/O fluid inclusions by microthermometry and laser Raman microprobe spectroscopy: inferences for clathrate and fluid equilibria  

SciTech Connect

Microthermometry (MT) and laser Raman microprobe (LRM) spectroscopy were done on 33 synthetically produced CO/sub 2/-CH/sub 4/-H/sub 2/O fluid inclusions in quartz. At room temperature, the inclusions consist of an aqueous liquid, a CO/sub 2/-CH/sub 4/ supercritical carbonic fluid, and graphite. In all these inclusions, the melting temperature for solid CO/sub 2/ is less than that for the homogenization of the vapor bubble in the carbonic fluid. A method is described whereby MT data for CO/sub 2/-CH/sub 4/-H/sub 2/O inclusions can be projected within the CO/sub 2/-CH/sub 4/ binary phase diagram to infer CO/sub 2/:CH/sub 4/ ratios in the carbonic fluid. This method takes into account the formation of CO/sub 2/-CH/sub 4/ clathrate hydrate during MT analysis. The authors interpretation of the MT data indicates that CH/sub 4/ is preferentially partitioned into the clathrate over the coexisting carbonic fluid, in contradiction to the prediction from PARRISH and PRAUSNITZ'S (1972) model for clathrate equilibria. Comparison of LRM analyses on the bulk carbonic fluid and the residual carbonic fluid confirm the preferential partitioning of CH/sub 4/ into the clathrate. LRM analyses of the clathrate itself indicate that CH/sub 4/ occupies both types of cage sites in the clathrate structure, whereas CO/sub 2/ may only occupy one site. Two by-products of the combined LRM and MT analyses of the same inclusions are derivation of empirical ratios of Raman quantification factors for high-density CO/sub 2/-CH/sub 4/ fluids and the ability to determine CO/sub 2/:CH/sub 4/ ratios of inclusions whose MT data lie near the critical region for CO/sub 2/-CH/sub 4/.

Seitz, J.C.; Pasteris, J.D.; Wopenka, B.

1987-06-01

347

Surface-enhanced Raman spectroscopy using gold-coated horizontally aligned carbon nanotubes  

Microsoft Academic Search

Gold-coated horizontally aligned carbon nanotube (Au-HA-CNT) substrates were fabricated for surface-enhanced Raman spectroscopy (SERS). The Au-HA-CNT substrates, which are granular in nature, are easy-to-prepare with large SERS-active area. Enhancement factors (EFs) of ?107 were achieved using the Au-HA-CNTs as substrates for rhodamine 6G (R6G) molecules. Maximum enhancement was found when the polarization direction (E-field) of the incident laser beam was

X N He; Y Gao; M Mahjouri-Samani; P N Black; J Allen; M Mitchell; W Xiong; Y S Zhou; L Jiang; Y F Lu

2012-01-01

348

The use of four-photon Raman spectroscopy for the remote sensing of natural objects  

NASA Technical Reports Server (NTRS)

The results of the laboratory simulation of optical Kerr effect/Raman spectroscopy for the purpose of remote sensing are presented. The experimental setup is described, and measurements of the vibrational spectra of various liquids obtained. Attention is paid to the possibility of using the proposed method to detect trace hydrocarbons in water, and the spectrum of petroleum is obtained. Full-scale measurements using a laser spectrometer were made on the Black Sea.

Bunkin, A. F.; Galumyan, A. S.; Zhumanov, Kh. A.; Maltsev, D. V.

1988-01-01

349

Developments of widely tunable light sources for picosecond time-resolved resonance Raman spectroscopy  

Microsoft Academic Search

Two systems of widely tunable light sources for picosecond time-resolved resonance Raman (ps-TR3) spectroscopy have been constructed using a 1 kHz ps-Ti:sapphire laser\\/regenerative amplifier system. Performance of the systems was examined in terms of pulse duration, spectral width, pulse energy, and shot-to-shot stability. One system, consisting of white light continuum seeder and ?-barium borate optical parametric amplifier, demonstrated tunability in

Yuki Uesugi; Yasuhisa Mizutani; Teizo Kitagawa

1997-01-01

350

Investigation of optical fibers for coherent anti-Stokes Raman scattering (CARS) spectroscopy in reacting flows  

Microsoft Academic Search

The objective of this work is to investigate the feasibility of intense laser-beam propagation through optical fibers for\\u000a temperature and species concentration measurements in gas-phase reacting flows using coherent anti-Stokes Raman scattering\\u000a (CARS) spectroscopy. In particular, damage thresholds of fibers, nonlinear effects during beam propagation, and beam quality\\u000a at the output of the fibers are studied for the propagation of

Paul S. Hsu; Anil K. Patnaik; James R. Gord; Terrence R. Meyer; Waruna D. Kulatilaka; Sukesh Roy

2010-01-01

351

Rapid viscosity determination of waterborne automotive paint emulsion system by FT-Raman spectroscopy  

Microsoft Academic Search

The feasibility of physical property assessment of waterborne automotive paint emulsion system using Fourier transform Raman spectroscopy (FT-Raman spectroscopy) was examined for viscosity as an example trait. The experiment was performed under the same temperature both in conventional and Raman spectroscopic methods aiming the online control. Raman spectroscopic data and the partial least squares (PLS) regression revealed highly significant correlation

Kazuhiro Ito; Tadaya Kato; Toshihiro Ona

2004-01-01

352

LASERS: Spectral characteristics of a Raman laser with intracavity frequency conversion  

Microsoft Academic Search

The spectral characteristics of the radiation emitted by a Raman laser with intracavity frequency conversion were investigated. This laser was found to suffer from frequency chirp both of the pump radiation and of the Raman frequencies. The integral width of the spectrum at the pump and Raman frequencies could exceed 1 cm-1.

Nikolai V. Kravtsov; Nikolai I. Naumkin

1994-01-01

353

Spectral broadening in continuous-wave intracavity Raman lasers.  

PubMed

Spectral broadening of the fundamental field in intracavity Raman lasers is investigated. The mechanism for the spectral broadening is discussed and the effect is compared in two lasers using Raman crystals with different Raman linewidths. The impact of the spectral broadening on the effective Raman gain is analyzed, and the use of etalons to limit the fundamental spectral width is explored. It was found that an improvement in output power could be obtained by using etalons to limit the fundamental spectrum to a single narrow peak. PMID:24718123

Bonner, Gerald M; Lin, Jipeng; Kemp, Alan J; Wang, Jiyang; Zhang, Huaijin; Spence, David J; Pask, Helen M

2014-04-01

354

Raman spectroscopy of garnet-group minerals  

USGS Publications Warehouse

The Raman spectra of the natural end members of the garnet-group minerals, which include pyrope, almandine and spessarite of Fe-Al garnet series and grossularite, andradite and uvarovite of Ca-Fe garnet series, have been studied. Measured Raman spectra of these minerals are reasonably and qualitatively assigned to the internal modes, translational and rotatory modes of SiO4 tetrahedra, as well as the translational motion of bivalent cations in the X site. The stretch and rotatory Alg modes for the Fe-Al garnet series show obvious Raman shifts as compared with those for the Ca-Fe garnet series, owing to the cations residing in the X site connected with SiO4 tetrahedra by sharing the two edges. The Raman shifts of all members within either of the series are attributed mainly to the properties of cations in the X site for the Fe-Al garnet series and in the Y site for the Ca-Fe garnet series. ?? 1994 Institute of Geochemistry, Chinese Academy of Sciences.

Mingsheng, P.; Mao, H. K.; Dien, L.; Chao, E. C. T.

1994-01-01

355

Calculations of nonlinear Raman spectroscopy of Xe  

NASA Astrophysics Data System (ADS)

The polarization dependence and temporal profile of the third-order and fifth-order Raman response functions of liquid Xe are studied both numerically and analytically. Many-body effects reduce the intensity of the anisotropic part of the dipole-induced-dipole tensor whereas the isotropic part of the effective dipole-induced-dipole tensor arises primarily from the three-body interaction and is short-ranged. To analyze polarization selectivity, we decompose the third-order Raman response into an isotropic component and an anisotropic component with the coefficients determined by the tensor properties of the dipole-dipole interaction. Based on the symmetry of an isotropic sample, the fifth-order Raman response function is decomposed into seven independent components. The decomposition coefficients are calculated explicitly based on the tensor property and rotational symmetry, and are used to characterize different coupling mechanisms in liquids. The temporal profiles of the third-order and fifth-order Raman response functions in Xe are formulated within hydrodynamic theory.

Cao, Jianshu

2002-03-01

356

Non-destructive Analysis of the Nuclei of Transgenic Living Cells Using Laser Tweezers and Near-infrared Raman Spectroscopic Technique  

Microsoft Academic Search

Transgenic cell lines of loblolly pine (Pinus taeda L.) were analyzed by a compact laser-tweezers-Raman-spectroscopy (LTRS) system in this investigation. A low power diode laser at 785 nm was used for both laser optical trapping of single transgenic cells and excitation for near-infrared Raman spectroscopy of the nuclei of synchronized cells, which were treated as single organic particles, at the

Wei Tang; Ronald J. Newton; Chang-An Xie; Yong-Qing Li; Nicki Whitley

357

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

NASA Astrophysics Data System (ADS)

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 ?mol·l-1 of E102 enables SERRDS at 488 nm for trace detection in e.g. food safety control as an appropriate contactless spectroscopic technique.

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

2010-04-01

358

Vibrational characterization of pheomelanin and trichochrome F by Raman spectroscopy  

NASA Astrophysics Data System (ADS)

We characterize for the first time the vibrational state of natural pheomelanin using Raman spectroscopy and model pigment synthesized from 5-S-cysteinyldopa. The shape of the Raman spectrum was very different from that of eumelanin. Four Raman bands were visible in the 500-2000 cm-1 wavenumber region about 500, 1150, 1490 and 2000 cm-1, which we assigned to the out-of-plane deformation and the stretching vibration of the phenyl rings, to the stretching vibration of C-N bonds or the stretching and wagging vibration of CH2, and to overtone or combination bands. Interestingly, we also show that the Raman spectrum of synthetic trichochrome F, a pigment that may be produced along with pheomelanin during pheomelanogenesis, is different from that of pheomelanin and similar to the spectrum of eumelanin. We could detect Raman signal of both eumelanin and pheomelanin in feathers and hairs where both pigments simultaneously occur without the need of isolating the pigment. This indicates that Raman spectroscopy represents a non-invasive method to detect pheomelanin and distinguish it from other pigments. This may be especially relevant to detect pheomelanin in animal skin including humans, where it has been associated with animal appearance and classification, human phototypes, prevention of skin diseases and cancer risk.

Galván, Ismael; Jorge, Alberto; Solano, Francisco; Wakamatsu, Kazumasa

2013-06-01

359

Classification of colonic tissues using Raman spectroscopy and multivariate techniques  

NASA Astrophysics Data System (ADS)

The purpose of this study was to explore the feasibility of using near-infrared (NIR) Raman spectroscopy and multivariate techniques for distinguishing cancer from normal and benign tissue in the colon. A total of 105 colonic specimens were used for Raman studies including 41 normal, 18 polyps, and 46 malignant tumors. The multivariate statistical techniques such as PCA-SVM were utilized to extract the significant Raman features and to develop effective diagnostic algorithms for tissue classification. The results showed that high-quality Raman spectra in the 800-1800 cm-1 range can be acquired from human colonic tissues in vitro, and Raman spectra differed significantly between normal, benign and malignant tumor tissue. PCA-SVM yielded a diagnostic sensitivity of 100%, 100%, and 97.7%, and specificity of 99.8%, 100%, and 100%, respectively, for differentiation between normal, polyp, and malignant tissue. Therefore, NIR Raman spectroscopy associated with multivariate techniques provides a significant potential for the noninvasive diagnosis of colonic cancers in vivo based on optical evaluation of biomolecules.

Huang, Zhiwei; Zheng, Wei; Widjaja, Effendi; Mo, Jianhua; Sheppard, Colin

2006-03-01

360

Monitoring of aqueous humor metabolites using Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Laser Raman scattering has been used to monitor glucose and lactate metabolites within aqueous humor specimens obtained from nine human eyes during cataract surgery. Nine postmortem rabbit eyes were also investigated. Raman measurements were obtained using a single grating Raman spectrometer with a liquid nitrogen cooled CCD. A 514.5 nm line from an argon laser was used to illuminate capillaries containing several microliters of aqueous humor. A water background was subtracted from each of the aqueous humor Raman spectra. This experimental system was calibrated so that each metabolite in water could be measured down to 0.1 weight percent. Raman peaks indicative of the stretching vibrations of methylene and methyl groups associated with glucose and lactate, respectively, were observed in the human specimens. A second stretching mode characteristic of lactate between the carbon atom and either the carboxylic acid group or carboxylate ion group was also observed providing a distinguishing feature between the glucose and lactate Raman peaks. Similar structure was observed from the rabbit specimens, but these samples have recently been found to have been contaminated during euthanasia.

Wicksted, James P.; Erckens, Roel J.; Motamedi, Massoud; March, Wayne F.

1994-05-01

361

Ultraviolet resonant Raman spectroscopy of nucleic acid components.  

PubMed Central

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

Blazej, D C; Peticolas, W L

1977-01-01

362

Non-resonant and non-enhanced Raman correlation spectroscopy.  

PubMed

We present the first non-resonant and non-enhanced Raman correlation spectroscopy experiments. They are conducted on a confocal microscope combined with a Raman spectrometer. The thermal fluctuations of the Raman intensities scattered by dispersions of polystyrene particles of sub-micrometric diameters are measured and analysed by deriving the autocorrelation functions (ACFs) of the intensities. We show that for particles of diameter down to 200 nm, RCS measurements are successfully obtained in spite of the absence of any source of amplification of the Raman signal. For particles of diameter ranging from 200 to 750 nm, the ACFs present a time-decay behaviour in accordance with the model of free Brownian particles. For particles of 1000 nm in diameter, the AFCs present a different behaviour with a much smaller characteristic time. This results from the dynamics of a single-Brownian particle trapped in the confocal volume by the optical forces of the focus spot. PMID:23842329

Barbara, A; Dubois, F; Quémerais, P; Eng, L

2013-07-01

363

Tip Enhanced Raman Spectroscopy and Imaging: an Apical Illumination Geometry  

PubMed Central

Results are presented illustrating the use of tip enhanced Raman spectroscopy and imaging in a top-illumination geometry. A radially polarized beam is used to generate an electric field component in the direction of beam propagation, normal to the surface, resulting in a 5× increased enhancement compared to a linearly polarized beam. This multiplicative enhancement facilitates a discrimination of the near field signal from the far field Raman background. The top illumination configuration facilitates the application of TERS for investigating molecules on a variety of surfaces, such as Au, glass, and Si. The near field Raman spectrum is presented of Si(100), rhodamine B, brilliant cresyl blue, and single wall carbon nanotubes. Sufficient enhancement is obtained to permit a sub-diffraction limited resolution Raman imaging of the surface distribution of large bundles of carbon nanotubes of various diameters.

Schultz, Zachary D.; Stranick, Stephan J.; Levin, Ira W.

2009-01-01

364

Predicting tenderness of fresh ovine semimembranosus using Raman spectroscopy.  

PubMed

A hand held Raman probe was used to predict shear force (SF) of fresh lamb m. semimembranosus (topside). Eighty muscles were measured at 1 day PM and after a further 4 days ageing (5 days PM). At 1 day PM sarcomere length (SL) and particle size (PS) were measured and at 5 days PM, SF, PS, cooking loss (CL) and pH were also measured. SF values were regressed against Raman spectra using partial least squares regression and against traditional predictors (e.g. SL) using linear regression. The best prediction of SF used spectra at 1 day PM which gave a root mean square error of prediction (RMSEP) of 11.5 N (Null = 13.2) and the squared correlation between observed and cross validated predicted values (R(2)cv) was 0.27. Prediction of SF based on the traditional predictors had smaller R(2) values than using Raman spectra justifying further study on Raman spectroscopy. PMID:24785653

Fowler, Stephanie M; Schmidt, Heinar; van de Ven, Remy; Wynn, Peter; Hopkins, David L

2014-08-01

365

Raman spectroscopy and microscopy based on mechanical force detection  

NASA Astrophysics Data System (ADS)

The Raman effect is typically observed by irradiating a sample with an intense light source and detecting the minute amount of frequency shifted scattered light. We demonstrate that Raman molecular vibrational resonances can be detected directly through an entirely different mechanism--namely, a force measurement. We create a force interaction through optical parametric down conversion between stimulated, Raman excited, molecules on a surface and a cantilevered nanometer scale probe tip brought very close to it. Spectroscopy and microscopy on clusters of molecules have been performed. Single molecules within such clusters are clearly resolved in the Raman micrographs. The technique can be readily extended to perform pump probe experiments for measuring inter- and intramolecular couplings and conformational changes at the single molecule level.

Rajapaksa, I.; Kumar Wickramasinghe, H.

2011-10-01

366

Raman mapping of laser-induced changes and ablation of InAs nanowires  

NASA Astrophysics Data System (ADS)

Indium arsenic (InAs) nanowires were irradiated with a focused laser beam, followed by in situ Raman spectroscopy mapping and scanning electron microscopy imaging to investigate the changes of the nanowires due to laser irradiation. It was found that laser irradiation with the power intensity above a certain threshold causes arsenic (As) atoms to disintegrate from InAs and accumulate on the surface of the nanowire; the accumulated As atoms evaporate under the continued laser irradiation. This process reduces the As content in the nanowire. The reduction of As content, in turn, lowers the melting temperature of the nanowire locally and facilitates laser ablation, which eventually fractures the nanowire. The laser irradiation induced changes of the InAs nanowires are attributed to the local temperature rises due to the irradiation, as confirmed by the Raman peak shifts. The results from this work show that in situ Raman spectroscopy mapping can provide detailed information about the entire process of laser-induced change and ablation of InAs nanowires and has the potential to become a powerful tool for the characterization of laser modification of nanowires and other nanometer-sized objects.

He, Jiayu; Chen, Pingping; Lu, Wei; Dai, Ning; Zhu, Da-Ming

2013-08-01

367

Raman mapping of laser-induced changes and ablation of InAs nanowires  

NASA Astrophysics Data System (ADS)

Indium arsenic (InAs) nanowires were irradiated with a focused laser beam, followed by in situ Raman spectroscopy mapping and scanning electron microscopy imaging to investigate the changes of the nanowires due to laser irradiation. It was found that laser irradiation with the power intensity above a certain threshold causes arsenic (As) atoms to disintegrate from InAs and accumulate on the surface of the nanowire; the accumulated As atoms evaporate under the continued laser irradiation. This process reduces the As content in the nanowire. The reduction of As content, in turn, lowers the melting temperature of the nanowire locally and facilitates laser ablation, which eventually fractures the nanowire. The laser irradiation induced changes of the InAs nanowires are attributed to the local temperature rises due to the irradiation, as confirmed by the Raman peak shifts. The results from this work show that in situ Raman spectroscopy mapping can provide detailed information about the entire process of laser-induced change and ablation of InAs nanowires and has the potential to become a powerful tool for the characterization of laser modification of nanowires and other nanometer-sized objects.

He, Jiayu; Chen, Pingping; Lu, Wei; Dai, Ning; Zhu, Da-Ming

2014-06-01

368

THz-Raman spectroscopy for explosives, chemical, and biological detection  

NASA Astrophysics Data System (ADS)

Raman and Terahertz spectroscopy are both widely used for their ability to safely and remotely identify unknown materials. Each approach has its advantages and disadvantages. Traditional Raman spectroscopy typically measures molecular energy transitions in the 200-5000cm-1 region corresponding to sub-molecular stretching or bending transitions, while Terahertz spectroscopy measures molecular energy transitions in the 1-200cm-1 region (30GHz - 6THz) that correspond to low energy rotational modes or vibrational modes of the entire molecule. Many difficult to detect explosives and other hazardous chemicals are known to have multiple relatively strong transitions in this "Terahertz" (<200cm-1, <6THz) regime, suggesting this method as a powerful complementary approach for identification. However, THz signal generation is often expensive, many THz spectroscopy systems are limited to just a few THz range, and strong water absorption bands in this region can act to mask certain transitions if great care isn't taken during sample preparation. Alternatively, low-frequency or "THz-Raman" spectroscopy, which covers the ~5cm-1 to 200cm-1 (150GHz - 6 THz) regions and beyond, offers a powerful, compact and economical alternative to probe these low energy transitions. We present results from a new approach for extending the range of Raman spectroscopy into the Terahertz regime using an ultra-narrow-band volume holographic grating (VHG) based notch filter system. An integrated, compact Raman system is demonstrated utilizing a single stage spectrometer to show both Stokes and anti-Stokes measurements down to <10cm-1 on traditionally difficult to detect explosives, as well as other chemical and biological samples.

Carriere, James T. A.; Havermeyer, Frank; Heyler, Randy A.

2013-05-01

369

A high efficiency architecture for cascaded Raman fiber lasers.  

PubMed

We demonstrate a new high efficiency architecture for cascaded Raman fiber lasers based on a single pass cascaded amplifier configuration. Conversion is seeded at all intermediate Stokes wavelengths using a multi-wavelength seed source. A lower power Raman laser based on the conventional cascaded Raman resonator architecture provides a convenient seed source providing all the necessary wavelengths simultaneously. In this work we demonstrate a 1480nm laser pumped by an 1117nm Yb-doped fiber laser with maximum output power of 204W and conversion efficiency of 65% (quantum-limited efficiency is ~75%). We believe both the output power and conversion efficiency (relative to quantum-limited efficiency) are the highest reported for cascaded Raman fiber lasers. PMID:23546098

Supradeepa, V R; Nichsolson, Jeffrey W; Headley, Clifford E; Yan, Man F; Palsdottir, Bera; Jakobsen, Dan

2013-03-25

370

Principle, system, and applications of tip-enhanced Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Raman spectroscopy is a powerful technique in chemical information characterization. However, this spectral method is subject to two obstacles in nano-material detection. One is diffraction limited spatial resolution, and the other is its inherent small Raman cross section and weak signaling. To resolve these problems, a new approach has been developed, denoted as tip-enhanced Raman spectroscopy (TERS). TERS is capable of high-resolution and high-sensitivity detection and demonstrated to be a promising spectroscopic and micro-topographic method to characterize nano-materials and nanostructures. In this paper, the principle and experimental system of TERS are discussed. The latest application of TERS in molecule detection, biological specimen identification, nanao-material characterization, and semi-conductor material determination with some specific experimental examples are presented.

Zhang, MingQian; Wang, Rui; Wu, XiaoBin; Wang, Jia

2012-08-01

371

Graphene: a platform for surface-enhanced Raman spectroscopy.  

PubMed

Surface-enhanced Raman spectroscopy (SERS) imparts Raman spectroscopy with the capability of detecting analytes at the single-molecule level, but the costs are also manifold, such as a loss of signal reproducibility. Despite remarkable steps having been taken, presently SERS still seems too young to shoulder analytical missions in various practical situations. By the virtue of its unique molecular structure and physical/chemical properties, the rise of graphene opens up a unique platform for SERS studies. In this review, the multi-role of graphene played in SERS is overviewed, including as a Raman probe, as a substrate, as an additive, and as a building block for a flat surface for SERS. Apart from versatile improvements of SERS performance towards applications, graphene-involved SERS studies are also expected to shed light on the fundamental mechanism of the SERS effect. PMID:23529788

Xu, Weigao; Mao, Nannan; Zhang, Jin

2013-04-22

372

A Rheumatoid arthritis study using Raman spectroscopy  

Microsoft Academic Search

Rheumatoid arthritis (RA) is characterized by chronic inflammation of the joints and can lead to a progressive destruction\\u000a of articular cartilage and bone. In this study, the specificity and sensitivity of the RA diagnostic methods based on the\\u000a receiver-operating characteristic curves for monitoring C-reactive protein (CRP) and rheumatoid factor (RF) were compared\\u000a with the Raman spectroscopic diagnostic method developed in

C. S. Carvalho; A. A. Martin; A. M. E. Santo; L. E. C. Andrade; M. M. Pinheiro; M. A. G. Cardoso; L. Raniero

373

Raman spectroscopy and oral exfoliative cytology  

NASA Astrophysics Data System (ADS)

Early detection of oral cancers can substantially improve disease-free survival rates. Ex vivo and in vivo Raman spectroscopic (RS) studies on oral cancer have demonstrated the applicability of RS in identifying not only malignant and premalignant conditions but also cancer-field-effects: the earliest events in oral carcinogenesis. RS has also been explored for cervical exfoliated cells analysis. Exfoliated cells are associated with several advantages like non-invasive sampling, higher patient compliance, transportation and analysis at a central facility: obviating need for on-site instrumentation. Thus, oral exfoliative cytology coupled with RS may serve as a useful adjunct for oral cancer screening. In this study, exfoliated cells from healthy controls with and without tobacco habits, premalignant lesions (leukoplakia and tobacco-pouch-keratosis) and their contralateral mucosa were collected using a Cytobrush. Cells were harvested by vortexing and centrifugation at 6000 rpm. The cellular yield was ascertained using Neubauer's chamber. Cell pellets were placed on a CaF2 window and Raman spectra were acquired using a Raman microprobe (40X objective) coupled HE-785 Raman spectrometer. Approximately 7 spectra were recorded from each pellet, following which pellet was smeared onto a glass slide, fixed in 95% ethanol and subjected to Pap staining for cytological diagnosis (gold standard). Preliminary PC-LDA followed by leave-one-out cross validation indicate delineation of cells from healthy and all pathological conditions. A tendency of classification was also seen between cells from contralateral, healthy tobacco and site of premalignant lesions. These results will be validated by cytological findings, which will serve as the basis for building standard models of each condition.

Sahu, Aditi; Shah, Nupur; Mahimkar, Manoj; Garud, Mandavi; Pagare, Sandeep; Nair, Sudhir; Krishna, C. Murali

2014-03-01

374

Nd:Glass-Raman laser for water vapor dial  

NASA Technical Reports Server (NTRS)

A tunable solid-state Raman shifted laser which was used in a water vapor Differential Absorption Lidar (DIAL) system at 9400 A is described. The DIAL transmitter is based on a tunable glass laser operating at 1.06 microns, a hydrogen Raman cell to shift the radiation to 1.88 microns, and a frequency doubling crystal. The results of measurements which characterize the output of the laser with respect to optimization of optical configuration and of Raman parameters were reported. The DIAL system was also described and preliminary atmospheric returns shown.

Kagann, R. H.; Petheram, J. C.; Rosenberg, A.

1986-01-01

375

Differential diagnosis between experimental endophthalmitis and uveitis in vitreous with Raman spectroscopy and principal components analysis.  

PubMed

Raman spectroscopy has been used for the diagnosis of various eye diseases. A diagnostic tool based on Raman spectroscopy has been developed to discriminate endophthalmitis from uveitis in vitreous tissues of rabbits' eyes in vitro. Twenty-two New Zealand rabbits suffering from endophthalmitis induced by Staphylococcus aureus (n=10), non-infectious uveitis induced by lipopolysaccharide from Escherichia coli (LPS) (n=10 animals) and control (n=2) were included in the study. After eye inoculation, vitreous tissues were dissected and a fragment was submitted to dispersive Raman spectroscopy using near-infrared laser excitation (830 nm, 100 mW) and spectrograph/CCD camera for detection of Raman signal with integration time of 50 s. A routine was developed to classify the spectra of endophthalmitis and uveitis using principal components analysis (PCA) and Mahalanobis distance. The mean Raman spectra of tissues with uveitis and endophthalmitis showed several bands in the region of 800-1800 cm(-1), which have been attributed to nucleic acids, amino acids and proteins from inflamed tissue and proliferating bacteria. The bands at 1004, 1258, 1339, 1451 and 1635 cm(-1) showed statistically significant differences between both diseases. It was observed that principal components PC1, PC3 and PC4 showed statistically significant differences for the two tissue types, indicating that these PCs can be used to discriminate between the two groups. The diagnostic model showed 94% sensitivity, 95% specificity and 95% accuracy using PC3×PC4. The Raman spectroscopy technique has been shown to be useful in differentiating uveitis and endophthalmitis in vitreous tissues in vitro, and these results may be clinically relevant for differentiating vitreous tissues to optimise the diagnosis of inflammatory and infectious vitreoretinal diseases. PMID:22209031

Rossi, Eglas Emanuel; Pinheiro, Antonio Luiz B; Baltatu, Ovidiu C; Pacheco, Marcos Tadeu T; Silveira, Landulfo

2012-02-01

376

Laser Spectroscopy of Transuranium Elements  

Microsoft Academic Search

The present paper aims to discuss the prospects for nuclear structure investigation of the transuranium elements by laser spectroscopy. The authors lay stress on two peculiarities of the nuclear structure in this region: the deformed shell closure at neutron number N = 152 and the appearance of superdeformed isomeric states. A laser spectroscopic experimental method is proposed for studying these

Yu. P. Gangrsky; D. V. Karaivanov; K. P. Marinova; B. N. Markov; Yu. E. Penionshkevich; S. G. Zemlyanoi

2005-01-01

377

Fourier transform IR and Raman spectroscopy and structure of carbohydrates  

Microsoft Academic Search

To determine the role of the skeletal base configuration of carbohydrate molecules, a comparative study was made, using IR and Raman spectroscopy, of theoretical calculations of the vibrational spectra of a series of carbohydrates differing in the configuration of CO (CH) bonds in various positions of the pyranose ring. The normal vibrations of carbohydrate molecules have, with few exceptions, close

R. G Zhbankov; V. M Andrianov; M. K Marchewka

1997-01-01

378

Raman Spectroscopy of Hydrogen Molecules in Crystalline Silicon  

Microsoft Academic Search

We report on a Raman spectroscopy study of float-zone crystalline silicon after exposure to a hydrogen plasma. New lines measured at 3601 and 2622 cm -1 are attributed to vibrational excitations of H2 and D2 molecules, respectively, positioned at the tetrahedral interstitial site within the Si lattice. These results correct a recent identification of molecular hydrogen in Si and confirm

A. W. R. Leitch; V. Alex; J. Weber

1998-01-01

379

Dispersions of graphene sheets characterized by Raman spectroscopy  

Microsoft Academic Search

Using expertise garnered on carbon nanotube separation, work is underway to demonstrate quality graphene dispersions and low defect sheets in the liquid phase. Several combinations of surfactants, solutions, starting graphite material, and separation protocols are being explored to determine the optimal chemical and physical environments. Raman spectroscopy is used as the quality indicator both for the numbers of layers and

Angela Hight Walker; Irene Calizo; Guangjun Cheng; Xiaomin Tu; Jeff Simpson; Ming Zheng

2010-01-01

380

Raman Spectroscopy of Carbonaceous Materials in Hydrothermal Ore Deposits  

NASA Astrophysics Data System (ADS)

In this study, we explore the potential of Raman spectroscopy of sp^2 hybridized carbonaceous materials as a geothermometer to shed light on the temperature of ore-forming fluids for the formation of the McArthur river Pb-Zn-Ag orebody.

Marshall, C. P.; Olcott Marshall, A.

2014-06-01

381

Developing Raman spectroscopy for in-situ determinations  

Microsoft Academic Search

Raman spectroscopy produces highly characteristic responses from all molecular species. It uses ultraviolet, visible or near-infrared radiation and thus is well suited for use with relatively inexpensive low-loss fiber optics. Because it is a scattering measurement it is readily applied to samples in a variety of forms, including aqueous solutions, solids and slurries, and to samples in hostile environments. This

Thomas J. Vickers; Charles K. Mann

1993-01-01

382

Raman spectroscopy for less invasive and online medical applications  

Microsoft Academic Search

Applications of optical spectroscopy techniques, such as Fourier Transform Infrared (FTIR), Raman, and fluorescence, in biology and medicine have been actively pursued in recent times. Since optical spectroscopic techniques are very sensitive to biochemical composition of the sample under study, they are being pursued as non invasive analytical methodologies. Early transformation from healthy to diseased states is attributed to biochemical

C. M. Krishna

2010-01-01

383

Stress Analysis of SiC MEMS Using Raman Spectroscopy  

NASA Astrophysics Data System (ADS)

During the fabrication of Micro-Electro-Mechanical Systems (MEMS), residual stress is often induced in the thin films that are deposited to create these systems. These stresses can cause the device to fail due to buckling, curling, or fracture. Industry is looking for ways to characterize the stress during the deposition of thin films in order to reduce or eliminate device failure. Micro-Raman spectroscopy has been successfully used to characterize poly-Si MEMS devices made with the MUMPS® process. Raman spectroscopy was selected because it is nondestructive, fast and has the potential for in situ stress monitoring. This research attempts to use Raman spectroscopy to analyze the stress in SiC MEMS made with the MUSiC® process. Raman spectroscopy is performed on 1-2-micron-thick SiC thin films deposited on silicon, silicon nitride, and silicon oxide substrates. The most common poly-type of SiC found in thin film MEMS made with the MUSiC® process is 3C-SiC. Research also includes baseline spectra of 6H, 4H, and 15R poly-types of bulk SiC.

Ness, Stanley J.; Marciniak, M. A.; Lott, J. A.; Starman, L. A.; Busbee, J. D.; Melzak, J. M.

2003-03-01

384

Raman and photoluminescence spectroscopy of free-standing GaN separated from sapphire substrates by 532 nm Nd:YAG laser lift-off  

Microsoft Academic Search

Gallium nitride (GaN) thin-films grown on sapphire substrates were lifted onto silicon wafer using a laser lift-off (LLO) process. The pulsed second harmonic (532nm) Nd:YAG laser used in our LLO experiments had a photon energy (2.33eV) much smaller than the band gap energy of hexagonal GaN (3.41eV). The free carriers in GaN absorbed the laser subsequently heated up the material.

H. P Ho; K. C Lo; G. G Siu; C Surya; K. F Li; K. W Cheah

2003-01-01

385

Saturation Raman spectroscopy of the excited states of metalloporphyrins  

Microsoft Academic Search

The application is discussed of saturation resonance Raman technique with nanosecond lasers both in spontaneous and coherent regimes to the investigations of the excited states of metalloporphyrins. It is shown that saturation technique enables us to obtain new information about transient states, additional to the data of direct kinetic measurements. For nickel octaethylporphyrin (OEP) complex, we present spectroscopic evidences for

Sergei G. Kruglik; Pavel A. Apanasevich; Vladimir V. Kvach; Valentin A. Orlovich

1995-01-01

386

Combining optical trapping in a microfluidic channel with simultaneous micro-Raman spectroscopy and motion detection  

NASA Astrophysics Data System (ADS)

Since their invention by Ashkin optical tweezers have demonstrated their ability and versatility as a non-invasive tool for micromanipulation. One of the most useful additions to the basic optical tweezers system is micro-Raman spectroscopy, which permits highly sensitive analysis of single cells or particles. We report on the development of a dual laser system combining two spatial light modulators to holographically manipulate multiple traps (at 1064nm) whilst undertaking Raman spectroscopy using a 532nm laser. We can thus simultaneously trap multiple particles and record their Raman spectra, without perturbing the trapping system. The dual beam system is built around micro-fluidic channels where crystallisation of calcium carbonate occurs on polymethylmethacrylate (PMMA) beads. The setup is designed to simulate at a microscopic level the reactions that occur on items in a dishwasher, where permanent filming of calcium carbonate on drinking glasses is a problem. Our system allows us to monitor crystal growth on trapped particles in which the Raman spectrum and changes in movement of the bead are recorded. Due to the expected low level of crystallisation on the bead surfaces this allows us to obtain results quickly and with high sensitivity. The long term goal is to study the development of filming on samples in-situ with the microfl.uidic system acting as a model dishwasher.

Lawton, Penelope F.; Saunter, Christopher D.; Girkin, John M.

2014-03-01

387

Integrated waveguide and nanostructured sensor platform for surface-enhanced Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Limitations of current sensors include large dimensions, sometimes limited sensitivity and inherent single-parameter measurement capability. Surface-enhanced Raman spectroscopy can be utilized for environment and pharmaceutical applications with the intensity of the Raman scattering enhanced by a factor of 10. By fabricating and characterizing an integrated optical waveguide beneath a nanostructured precious metal coated surface a new surface-enhanced Raman spectroscopy sensing arrangement can be achieved. Nanostructured sensors can provide both multiparameter and high-resolution sensing. Using the slab waveguide core to interrogate the nanostructures at the base allows for the emission to reach discrete sensing areas effectively and should provide ideal parameters for maximum Raman interactions. Thin slab waveguide films of silicon oxynitride were etched and gold coated to create localized nanostructured sensing areas of various pitch, diameter, and shape. These were interrogated using a Ti:Sapphire laser tuned to 785-nm end coupled into the slab waveguide. The nanostructured sensors vertically projected a Raman signal, which was used to actively detect a thin layer of benzyl mercaptan attached to the sensors.

Pearce, Stuart J.; Pollard, Michael E.; Oo, SweZin; Chen, Ruiqi; Kalsi, Sumit; Charlton, Martin D. B.

2014-01-01

388

Assessment of thermal coagulation in ex-vivo tissues using Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Raman spectroscopy is used to study the effects of heating on specific molecular bonds present in albumen-based coagulation phantoms and ex-vivo tissues. Thermal coagulation is induced by submerging albumen-based phantoms in a 75°C water bath to achieve target temperatures of 45, 55, 65, and 75°C. Laser photocoagulation is performed on ex-vivo bovine muscle samples, yielding induced temperatures between 46 and 90°C, as reported by implanted microthermocouples. All phantoms and tissue samples are cooled to room temperature, and Raman spectra are acquired at the microthermocouple locations. Shifts in major Raman bands are observed with laser heating in bovine muscle, specifically from the amide-1 ?-helix group (~1655 cm-1), the CH2/CH3 group (~1446 cm-1), the C?-H stretch group (~1312 cm-1), and the CN stretch group (~1121cm-1). Raman bands at 1334 cm-1 (tryptophan), 1317 cm-1 [?(C?-H)], and 1655 cm-1 (amide-1 ?-helix) also show a decrease in intensity following heating. The results suggest that Raman band locations and relative intensities are affected by thermal denaturation of proteins, and hence, may be a useful tool for monitoring the onset and progression of coagulation during thermal therapies.

Rodrigues, Matthew; Weersink, Robert A.; Whelan, William M.

2010-11-01

389

Next generation hazard detection via ultrafast coherent anti-Stokes Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Multiplex coherent anti-Stokes Raman spectroscopy (MCARS) is used to detect an explosive precursor material and two chemical warfare simulants. The spectral bandwidth of the femtosecond laser pulse used in these studies is sufficient to coherently and simultaneously drive all the vibrational modes in the molecule of interest. The research performed here demonstrates that MCARS has the capability to detect an explosive precursor (e.g., acetone) and hazardous materials, such as dimethyl methylphosphonate and 2-chloroethyl methyl sulfide (a sarin and a mustard gas chemical warfare simulant, respectively), with high specificity. Evidence shows that MCARS is capable of overcoming common the sensitivity limitations of spontaneous Raman scattering, thus allowing for the detection of the target material in milliseconds with standard USB spectrometers as opposed to seconds with intensified spectrometers. The exponential increase in the number of scattered photons suggests that the MCARS technique may be capable of overcoming range detection challenges common to spontaneous Raman scattering.

Brady, John J.; Pellegrino, Paul M.

2013-05-01

390

Histochemical analysis of human coronary artery using near-infrared Raman spectroscopy  

NASA Astrophysics Data System (ADS)

We are developing a method to quantitatively analyze the biochemical composition of human coronary artery in situ using near-infrared Raman spectroscopy. Samples of normal artery (intima/media and adventitia) and noncalcified and calcified plaque from coronary arteries, obtained from explanted recipient hearts during heart transplantation, were illuminated with 830 nm excitation light from a CW Ti:sapphire laser. Raman spectra were collected in seconds using a spectrograph and a cooled, deep-depletion CCD detector, and calibration and background corrections were made. Artery samples in different stages of atherosclerosis exhibited distinct spectral features, providing clear histochemical indicators for characterizing the type and extent of the lesion. Spectra were analyzed by means of a Raman biochemical assay model to determine the relative weight fractions of cholesterols, triacylglycerol, proteins and calcium minerals. Such information, when obtained clinically, promises to be useful in diagnosing and studying human atherosclerosis, its progression and response to drug therapy.

Brennan, James F.; Romer, Tjeerd J.; Wang, Yang; Fitzmaurice, Maryann; Lees, Robert S.; Kramer, John R.; Feld, Michael S.

1995-01-01

391

Looking behind the scenes: Raman spectroscopy of top-gated epitaxial graphene through the substrate  

NASA Astrophysics Data System (ADS)

Raman spectroscopy is frequently used to study the properties of epitaxial graphene grown on silicon carbide (SiC). In this work, we present a confocal micro-Raman study of epitaxial graphene on SiC(0001) in top-down geometry, i.e. in a geometry where both the primary laser light beam as well as the back-scattered light is guided through the SiC substrate. Compared to the conventional top-up configuration, in which confocal micro-Raman spectra are measured from the air side, we observe a significant intensity enhancement in top-down configuration, indicating that most of the Raman-scattered light is emitted into the SiC substrate. The intensity enhancement is explained in terms of dipole radiation at a dielectric surface. The new technique opens the possibility to probe graphene layers in devices where the graphene layer is covered by non-transparent materials. We demonstrate this by measuring gate-modulated Raman spectra of a top-gated epitaxial graphene field effect device. Moreover, we show that these measurements enable us to disentangle the effects of strain and charge on the positions of the prominent Raman lines in epitaxial graphene on SiC.

Fromm, F.; Wehrfritz, P.; Hundhausen, M.; Seyller, Th

2013-11-01

392

Diagnosis of atherosclerosis in human carotid artery by FT-Raman spectroscopy: Principal Components Analysis algorithm  

NASA Astrophysics Data System (ADS)

FT- Raman Spectroscopy (FT-Raman) could allow identification and evaluation of human atherosclerotic lesions. A Raman spectrum can provide biochemical information of arteries which can help identifying the disease status and evolution. In this study, it is shown the results of FT-Raman for identification of human carotid arteries in vitro. Fragments of human carotid arteries were analyzed using a FT-Raman spectrometer with a Nd:YAG laser at 1064nm operating at an excitation power of 300mW. Spectra were obtained with 250 scans and spectral resolution of 4 cm-1. Each collection time was approximately 8 min. A total of 75 carotid fragments were spectroscopically scanned and FT-Raman results were compared with histopathology. Principal Components Analysis (PCA) was used to model an algorithm for tissue classification into three categories: normal, atherosclerotic plaque without calcification and atherosclerotic plaque with calcification. Non-atherosclerotic (normal) artery, atherosclerotic plaque and calcified plaque exhibit different spectral signatures related to biochemicals presented in each tissue type, such as, bands of collagen and elastin (proteins), cholesterol and its esters and calcium hydroxyapatite and carbonate apatite respectively. Results show that there is 96% match between classifications based on PCA algorithm and histopathology. The diagnostic applied over all 75 samples had sensitivity and specificity of about 89% and 100%, respectively, for atherosclerotic plaque and 100% and 98% for calcified plaque.

Nogueira, Grazielle V.; Silveira, Landulfo, Jr.; Martin, Airton A.; Zangaro, Renato A.; Pacheco, Marcos T.; Chavantes, Maria C.; Zampieri, Marcelo; Pasqualucci, Carlos A. G.

2004-07-01

393

Laser-Induced Instabilities in Raman-Active Media.  

National Technical Information Service (NTIS)

Laser-induced instabilities in Raman-active media are studied. The stimulated Raman scattering process is found to be important in benzene even for a Stokes conversion rate of a few percent. Growth rates are obtained by numerical analysis, using equations...

K. A. Brueckner S. S. Rangnekar

1968-01-01

394

Coherent control of stimulated Raman scattering using chirped laser pulses  

Microsoft Academic Search

A novel method for the control of stimulated Raman scattering and hot electron production in short-pulse laser-plasma interactions is proposed. It relies on the use of a linear frequency chirp in nonbandwidth limited pulses. Theoretical calculations show that a 12% bandwidth will eliminate Raman forward scattering for a plasma density that is 1% of the critical density. The predicted changes

Evan S. Dodd; Donald Umstadter

2001-01-01

395

Quantitative monitoring of yeast fermentation using Raman spectroscopy.  

PubMed

Compared to traditional IR methods, Raman spectroscopy has the advantage of only minimal interference from water when measuring aqueous samples, which makes this method potentially useful for in situ monitoring of important industrial bioprocesses. This study demonstrates real-time monitoring of a Saccharomyces cerevisiae fermentation process using a Raman spectroscopy instrument equipped with a robust sapphire ball probe. A method was developed to correct the Raman signal for the attenuation caused by light scattering cell particulate, hence enabling quantification of reaction components and possibly measurement of yeast cell concentrations. Extinction of Raman intensities to more than 50 % during fermentation was normalized with approximated extinction expressions using Raman signal of water around 1,627 cm(-1) as internal standard to correct for the effect of scattering. Complicated standard multi-variant chemometric techniques, such as PLS, were avoided in the quantification model, as an attempt to keep the monitoring method as simple as possible and still get satisfactory estimations. Instead, estimations were made with a two-step approach, where initial scattering correction of attenuated signals was followed by linear regression. In situ quantification measurements of the fermentation resulted in root mean square errors of prediction (RMSEP) of 2.357, 1.611, and 0.633 g/L for glucose, ethanol, and yeast concentrations, respectively. PMID:24996999

Iversen, Jens A; Berg, Rolf W; Ahring, Birgitte K

2014-08-01

396

Raman spectroscopy for the characterization of algal cells  

NASA Astrophysics Data System (ADS)

Raman spectroscopy can elucidate fundamental questions about intercellular variability and what governs it. Moreover, knowing the metabolic response on single cell level this can significantly contribute to the study and use of microalgae in systems biology and biofuel technology. Raman spectroscopy is capable to measure nutrient dynamics and metabolism in vivo, in real-time, label free making it possible to monitor/evaluate population variability. Also, degree of unsaturation of the algae oil (iodine value) can be measured using Raman spectra obtained from single microalgae. The iodine value is the determination of the amount of unsaturation contained in fatty acids (in the form of double bonds). Here we demonstrate the capacity of the spatially resolved Raman microspectroscopy to determine the effective iodine value in lipid storage bodies of individual living algal cells. We employed the characteristic peaks in the Raman scattering spectra at 1,656 cm-1 (cis C=C stretching mode) and 1,445 cm-1 (CH2 scissoring mode) as the markers defining the ratio of unsaturated-to-saturated carbon-carbon bonds of the fatty acids in the algal lipids.

Samek, Ota; Jonáš, Alexandr; Pilát, Zden?k; Zemánek, Pavel; Nedbal, Ladislav; T?íska, Jan; Kotas, Petr; Trtílek, Martin

2010-09-01

397

Transcutaneous Raman Spectroscopy of Murine Bone In Vivo  

PubMed Central

Raman spectroscopy can provide valuable information about bone tissue composition in studies of bone development, biomechanics, and health. In order to study the Raman spectra of bone in vivo, instrumentation that enhances the recovery of subsurface spectra must be developed and validated. Five fiber-optic probe configurations were considered for transcutaneous bone Raman spectroscopy of small animals. Measurements were obtained from the tibia of sacrificed mice, and the bone Raman signal was recovered for each probe configuration. The configuration with the optimal combination of bone signal intensity, signal variance, and power distribution was then evaluated under in vivo conditions. Multiple in vivo transcutaneous measurements were obtained from the left tibia of 32 anesthetized mice. After collecting the transcutaneous Raman signal, exposed bone measurements were collected and used as a validation reference. Multivariate analysis was used to recover bone spectra from transcutaneous measurements. To assess the validity of the transcutaneous bone measurements cross-correlations were calculated between standardized spectra from the recovered bone signal and the exposed bone measurements. Additionally, the carbonate-to-phosphate height ratios of the recovered bone signals were compared to the reference exposed bone measurements. The mean cross-correlation coefficient between the recovered and exposed measurements was 0.96, and the carbonate-to-phosphate ratios did not differ significantly between the two sets of spectra (p > 0.05). During these first systematic in vivo Raman measurements, we discovered that probe alignment and animal coat color influenced the results and thus should be considered in future probe and study designs. Nevertheless, our noninvasive Raman spectroscopic probe accurately assessed bone tissue composition through the skin in live mice.

Schulmerich, Matthew V.; Cole, Jacqueline H.; Kreider, Jaclynn M.; Esmonde-White, Francis; Dooley, Kathryn A.; Goldstein, Steven A.; Morris, Michael D.

2009-01-01

398

Quantitative polarized Raman spectroscopy in highly turbid bone tissue  

PubMed Central

Polarized Raman spectroscopy allows measurement of molecular orientation and composition and is widely used in the study of polymer systems. Here, we extend the technique to the extraction of quantitative orientation information from bone tissue, which is optically thick and highly turbid. We discuss multiple scattering effects in tissue and show that repeated measurements using a series of objectives of differing numerical apertures can be employed to assess the contributions of sample turbidity and depth of field on polarized Raman measurements. A high numerical aperture objective minimizes the systematic errors introduced by multiple scattering. We test and validate the use of polarized Raman spectroscopy using wild-type and genetically modified (oim?oim model of osteogenesis imperfecta) murine bones. Mineral orientation distribution functions show that mineral crystallites are not as well aligned (p<0.05) in oim?oim bones (28±3 deg) compared to wild-type bones (22±3 deg), in agreement with small-angle X-ray scattering results. In wild-type mice, backbone carbonyl orientation is 76±2 deg and in oim?oim mice, it is 72±4 deg (p>0.05). We provide evidence that simultaneous quantitative measurements of mineral and collagen orientations on intact bone specimens are possible using polarized Raman spectroscopy.

Raghavan, Mekhala; Sahar, Nadder D.; Wilson, Robert H.; Mycek, Mary-Ann; Pleshko, Nancy; Kohn, David H.; Morris, Michael D.

2010-01-01

399

Background-free stimulated Raman spectroscopy and microscopy.  

PubMed

We propose a three-color, double-modulation scheme for the background-free detection of stimulated Raman scattering (SRS). We call the scheme stimulated Raman gain and opposite loss detection (SRGOLD). It exploits the symmetric nature of potential parasitic signals (cross phase modulation, two-photon absorption, and thermal effects) to the end of suppressing them. Conversely, the antisymmetric nature of SRS provides for a twofold increase in the magnitude of the SRS signal. We experimentally demonstrate SRGOLD spectroscopy and microscopy on test samples as well as on mice skin samples. PMID:24580595

Berto, Pascal; Andresen, Esben Ravn; Rigneault, Hervé

2014-02-01

400

Stimulated Raman scattering of intense laser pulses in air  

Microsoft Academic Search

Stimulated rotational Raman scattering (SRRS) is known to be one of the processes limiting the propagation of high-power laser beams in the atmosphere. In this paper, SRRS, Kerr nonlinearity effects, and group velocity dispersion of short laser pulses and pulse trains are analyzed and simulated. Fully time-dependent, three-dimensional, nonlinear propagation equations describing the Raman interaction, optical Kerr nonlinearity due to

J. R. Peńano; P. Sprangle; P. Serafim; B. Hafizi; A. Ting

2003-01-01

401

Determination of octane numbers and Reid vapor pressure in commercial gasoline using dispersive fiber-optic Raman spectroscopy  

Microsoft Academic Search

Dispersive fiber-optic Raman spectroscopy utilizing CCD detection and near-IR DBR diode laser excitation is used to remotely analyze 205 petroleum fuels of varying composition for pump octane number, motor octane number (MON), research octane number (RON), and Reid vapor pressure (RVP). Partial least squares regression analysis in tandem with several preprocessing techniques was used to model pump octane, MON, RON,

Philip E. Flecher; William T. Welch; Sacharia Albin; John B. Cooper

1997-01-01

402

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

NASA Astrophysics Data System (ADS)

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.

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

2012-02-01

403

Raman spectroscopy study on free-standing GaN separated from sapphire substrates by 532 nm Nd:YAG laser lift-off  

Microsoft Academic Search

Gallium nitride (GaN) thin films grown on sapphire substrates were successfully lifted onto silicon wafers using a laser lift-off (LLO) process induced by a 532 nm, Nd:YAG pulsed laser. Although the photon energy (2.33 eV) is much lower than the band gap of hexagonal GaN (3.41 eV), free-carriers absorption can heat up and consequently causes detachment of the GaN film

H. P. Ho; K. C. Lo; G. G. Siu; C. Surya

2002-01-01

404

Registration pollution of water by method of modulation intracavity laser spectroscopy  

Microsoft Academic Search

In this work, the method of the modulation intracavity laser spectroscopy is shown to be candidate for investigation and quantitative analysis of organic pollutions in water. The test specimen is placed into the cavity of the multimode dye laser. When the Raman scattering line coincides with amplification spectrum of the active medium of the multimode laser the additional gain appears

Sergey Bojko; Vladimir F. Gamalii

1995-01-01

405

Interference-free optical detection for Raman spectroscopy  

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

406

Plasmonic DNA-Origami Nanoantennas for Surface-Enhanced Raman Spectroscopy.  

PubMed

We report that plasmonic nanoantennas made by DNA origami can be used as reliable and efficient probes for surface-enhanced Raman spectroscopy (SERS). The nanoantenna is built up by two gold nanoparticles that are linked together by a three-layered DNA origami block at a separation distance of 6 nm in order to achieve plasmonic coupling and the formation of a plasmonic "hot spot". The plasmonic properties of the hybrid structure are optically characterized by dark-field imaging and polarization-dependent spectroscopy. SERS measurements on molecules that are embedded in the DNA origami that bridges the nanoantenna gap were performed in order to demonstrate the excellent performance of these structures for enhancing spectroscopic signals. A strong enhancement of the Raman signal was recorded from measurements on single hot spots compared to measurements in bulk. Finally, we show that the laser polarization with respect to the dimer orientation has a strong impact on the SERS performance. PMID:24754830

Kühler, Paul; Roller, Eva-Maria; Schreiber, Robert; Liedl, Tim; Lohmüller, Theobald; Feldmann, Jochen

2014-05-14

407

Raman and surface-enhanced Raman spectroscopy of tempyo spin labelled ovalbumin  

NASA Astrophysics Data System (ADS)

Tempyo labelled ovalbumin at different pH values was prepared and investigated using Raman and SERS spectroscopy. Raman spectra of tempyo labelled ovalbumin in the pH range from 6.7 to 11 were compared to those of the corresponding free ovalbumin. In the basic pH range from 6.7 to 11 the molecular conformation was found to be unaffected by the tempyo presence. Adsorption versatility to the colloidal Ag particles of pure- and tempyo labelled ovalbumin was also found to be unchanged in this basic pH range. As the SERS binding site of protein the ?-helix conformation is favourable.

C??ntÖP??nzaru, S.; Cavalu, S.; Leopold, N.; Petry, R.; Kiefer, W.

2001-05-01

408

Raman-shifted dye laser for water vapor DIAL measurements  

NASA Astrophysics Data System (ADS)

For improved DIAL measurements of water vapor in the upper troposphere or lower stratosphere, narrowband (about 0.03/cm) laser radiation at 720- and 940-nm wavelengths was generated by stimulated Raman scattering (SRS), using the narrow linewidth (about 0.02/cm) output of a Nd:YAG-pumped dye laser. For a hydrogen pressure of 350 psi, the first Stokes conversion efficiencies to 940 nm were 20 percent and 35 percent, when using a conventional and waveguide Raman cell, respectively. The linewidth of the first Stokes line at high cell pressures, and the inferred collisional broadening coefficients, agree well with those previously measured in spontaneous Raman scattering.

Grossmann, B. E.; Singh, U. N.; Cotnoir, L. J.; Wilkerson, T. D.; Higdon, N. S.; Browell, E. V.

1987-05-01

409

Raman-shifted dye laser for water vapor DIAL measurements.  

PubMed

For improved DIAL measurements of water vapor in the upper troposphere or lower stratosphere, we have generated narrowband (~0.03-cm(-1)) laser radiation at 720- and 940-nm wavelengths by stimulated Raman scattering (SRS) using the narrow linewidth (~0.02-cm(-1)) output of a Nd:YAG-pumped dye laser. For a hydrogen pressure of 350 psi, the first Stokes conversion efficiencies to 940 nm were 20% and 35% when using a conventional and waveguide Raman cell, respectively. We measured the linewidth of the first Stokes line at high cell pressures and inferred collisional broadening coefficients that agree well with those previously measured in spontaneous Raman scattering. PMID:20454378

Grossmann, B E; Singh, U N; Higdon, N S; Cotnoir, L J; Wilkerson, T D; Browell, E V

1987-05-01

410

Raman-shifted dye laser for water vapor DIAL measurements  

NASA Technical Reports Server (NTRS)

For improved DIAL measurements of water vapor in the upper troposphere or lower stratosphere, narrowband (about 0.03/cm) laser radiation at 720- and 940-nm wavelengths was generated by stimulated Raman scattering (SRS), using the narrow linewidth (about 0.02/cm) output of a Nd:YAG-pumped dye laser. For a hydrogen pressure of 350 psi, the first Stokes conversion efficiencies to 940 nm were 20 percent and 35 percent, when using a conventional and waveguide Raman cell, respectively. The linewidth of the first Stokes line at high cell pressures, and the inferred collisional broadening coefficients, agree well with those previously measured in spontaneous Raman scattering.

Grossmann, B. E.; Singh, U. N.; Cotnoir, L. J.; Wilkerson, T. D.; Higdon, N. S.; Browell, E. V.

1987-01-01

411

Laser Raman sensor for measurement of trace-hydrogen gas  

NASA Technical Reports Server (NTRS)

A new optical hydrogen sensor based on spontaneous Raman scattering of laser light has been designed and constructed for rugged field use. It provides good sensitivity, rapid response, and the inherent Raman characteristics of linearity and background gas independence of the signal. Efficient light collection and discrimination by using fast optics and a bandpass interference filter compensate for the inefficiency of the Raman-scattering process. A multipass optical cavity with a Herriott-type configuration provides intense illumination from an air-cooled CW gas laser. The observed performance is in good agreement with the theoretical signal and noise level predictions.

Adler-Golden, Steven M.; Goldstein, Neil; Bien, Fritz; Matthew, Michael W.; Gersh, Michael E.; Cheng, Wai K.; Adams, Frederick W.

1992-01-01

412

Er:YAG laser irradiation on dentin: FT-Raman and SEM studies  

NASA Astrophysics Data System (ADS)

This study evaluated the molecular and morphological changes on dentin elements after the Er:YAG laser irradiation. Six human third molars were selected and the occlusal one-third of the crown was removed. The dentin surface was schematically divided into areas corresponding to four surface treatments groups: Control (Group C): 37% phosphoric acid etching; Group I: Er:YAG laser 80mJ; Group II: Er:YAG laser 120mJ; Group III: Er:YAG laser 180mJ. The characterization was performed by Scanning Electron Microscopy (SEM) and Fourier-Transformed Raman Spectroscopy (FT-Raman) before and after the treatments. A reduction of the relative intensity for the spectra was observed in the Group II and III samples. The SEM photomicrographies revealed open dentin tubules in the control group specimens. The groups I, II and III presented partially open dentin tubules. SEM images showed that the laser-irradiated dentin surface was not favorable to the diffusion of monomers. The chemical information obtained by Raman spectroscopy showed that higher laser energies (180 mJ) affected more the phosphate, carbonate and the organic components of dentin.

Soares, Luís Eduardo Silva; Bitar, Renata Andrade; Brugnera, Aldo; Zanin, Fatima A. A.; Resende, Erick B. P. S.; Jara, Walter A. A.; Martin, Airton A.

2007-02-01

413

Verifying of endocrine disruptor chemical affect to the mouse testes: can raman spectroscopy support histology study?  

NASA Astrophysics Data System (ADS)

One of suspect environmental endocrine disruptors that affect mouse male reproduction by altering the morphology of Sertoli cells and spermatogenic cells is phthalate. The effects of mono(2-ethylhexyl)phthalate (MEHP), one of metabolites of di(2-ethylhexyl)phthalate , on immature mouse testes in vivo were examined. W