Journal articles: 'Raman spectra measurement'

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Zhou, Qian, Zhiyong Zou, and Lin Han. "Deep Learning-Based Spectrum Reconstruction Method for Raman Spectroscopy." Coatings 12, no. 8 (August 22, 2022): 1229. http://dx.doi.org/10.3390/coatings12081229.

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Raman spectroscopy, measured by a Raman spectrometer, is usually disturbed by the instrument response function and noise, which leads to certain measurement error and further affects the accuracy of substance identification. In this paper, we propose a spectral reconstruction method which combines the existing maximum a posteriori (MAP) method and deep learning (DL) to recover the degraded Raman spectrum. The proposed method first employs the MAP method to reconstruct the measured Raman spectra, so as to obtain preliminary estimated Raman spectra. Then, a convolutional neural network (CNN) is trained by using the preliminary estimated Raman spectra and the real Raman spectra to learn the mapping from the preliminary estimated Raman spectra to the real Raman spectra, so as to achieve a better spectral reconstruction effect than merely using the MAP method or a CNN. To prove the effectiveness of the proposed spectral reconstruction method, we employed the proposed method and some traditional spectral reconstruction methods to reconstruct the simulated and measured Raman spectra, respectively. The experimental results show that compared with traditional methods, the estimated Raman spectra reconstructed by the proposed method are closer to the real Raman spectra.

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Narita, Yoshihito, Toshiyasu Tadokoro, Teruki Ikeda, Toshiharu Saiki, Syuji Mononobe, and Motoichi Ohtsu. "Near-Field Raman Spectral Measurement of Polydiacetylene." Applied Spectroscopy 52, no. 9 (September 1998): 1141–44. http://dx.doi.org/10.1366/0003702981945101.

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Two-dimensional near-field Raman spectra and topographic images of the polydiacetylene surface are measured simultaneously by using a near-field Raman spectrometer. The spectra (located 100 nm apart) have different spectral features. The peak intensity ratio of two C=C peaks at 1520 and 1457 cm−1 does not correlate with the topographic image and shows differences in the subwavelength scale. These differences can be interpreted as spatial differences in the number of successive bonds on the polydiacetylene surface. In contrast, the near-field Raman intensity of the C=C bond at 1457 cm−1 correlates strongly with the topographic image. This phenomenon can be interpreted as a change in the efficiency of collecting Raman scattering light.

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Sun, Yuqi, Xiaotian Li, Jiri Galantu, Qihang Chu, Jun Chen, Zhongkai Liu, Xiaotao Mi, Xuefeng Yao, and Pan Li. "Terahertz Raman Measurements Using a Spatial Heterodyne Raman Spectrometer." Applied Sciences 11, no. 17 (August 31, 2021): 8094. http://dx.doi.org/10.3390/app11178094.

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We propose a method of measuring the terahertz (THz) Raman spectra of a material. As Raman spectroscopy is a measurement of the relative frequency spectrum relative to the frequency of the excitation source, sometimes it is not necessary to use an expensive THz source and THz detector. Instead, an ultraviolet, visible, or infrared excitation source and corresponding detector can be used. A combination of prisms and gratings is used to widen the field of view at high resolution. The resolution of the system is 4.945 cm−1 (0.149 THz), and the spectral range is 2531.84 cm−1 (75.963 THz). We measured the THz Raman spectra of solid powder, aqueous solutions, and mixtures, and studied the effects of environment, container material, and time of measurement on the spectra. The results show that the system is not significantly affected by interference from the water environment and has good stability and repeatability. This method can be applied in many fields such as material detection and environmental protection.

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Zhu, Shichao, Zhuoming Song, Shengyu Shi, Mengmeng Wang, and Gang Jin. "Fusion of Near-Infrared and Raman Spectroscopy for In-Line Measurement of Component Content of Molten Polymer Blends." Sensors 19, no. 16 (August 8, 2019): 3463. http://dx.doi.org/10.3390/s19163463.

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Spectral measurement techniques, such as the near-infrared (NIR) and Raman spectroscopy, have been intensively researched. Nevertheless, even today, these techniques are still sparsely applied in industry due to their unpredictable and unstable measurements. This paper put forward two data fusion strategies (low-level and mid-level fusion) for combining the NIR and Raman spectra to generate fusion spectra or fusion characteristics in order to improve the in-line measurement precision of component content of molten polymer blends. Subsequently, the fusion value was applied to modeling. For evaluating the response of different models to data fusion strategy, partial least squares (PLS) regression, artificial neural network (ANN), and extreme learning machine (ELM) were applied to the modeling of four kinds of spectral data (NIR, Raman, low-level fused data, and mid-level fused data). A system simultaneously acquiring in-line NIR and Raman spectra was built, and the polypropylene/polystyrene (PP/PS) blends, which had different grades and covered different compounding percentages of PP, were prepared for use as a case study. The results show that data fusion strategies improve the ANN and ELM model. In particular, mid-level fusion enables the in-line measurement of component content of molten polymer blends to become more accurate and robust.

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Ershova, Ksenia, Svetlana Kochemirovskaya, Natalia P. Kirillova, Vladimir Kochemirovsky, and Mikhail Ryazantsev. "Inﬂuence of Raman spectra measurement conditions on the dating results of writing compositions." Nowa Kodyfikacja Prawa Karnego 60 (February 1, 2022): 61–97. http://dx.doi.org/10.19195/2084-5065.60.5.

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When establishing the age of a document using spectral methods, the result is inﬂuenced not only by the storage conditions, but also by the methods of measuring the spectra and mathematical processing of the results. This work analyzes the inﬂuence the modes of measuring Raman spectra have on the result of measuring the writing composition spec-tra. The analysis area includes the correlation coeﬃcients of the full spectral matrices as a criterion for the reliability of the determination date. The inﬂuence of focusing accuracy, correctness of subtraction of the baseline, sample irradiation time, and varying the number of repetitions is investigated. In the study, chemometric tools for the analysis of Raman spectra were also applied. The inﬂuence of mathematical spectra processing shows that the components PC4, P5, and PC6 are most closely related to the shelf life, although they do not make the maximum contribution to the variance in the system. Taking into account all the requirements for measuring spectra, the PCA method applied to the Raman spectra of writing compositions allows clustering samples by manufacturer’s brands and by the sample shelf life.

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Vlčková, Blanka, Bohuslav Strauch, and Milan Horák. "Measurement and interpretation of infrared and raman spectra of vanadyl acetylacetonate." Collection of Czechoslovak Chemical Communications 52, no. 3 (1987): 686–95. http://dx.doi.org/10.1135/cccc19870686.

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Infrared and Raman spectra of oxobis (2,4-pentandionate) vanadium complex have been studied. A reduction of the number of spectral bands observed in the IR and Raman spectra compared to the theoretical number of normal modes expected for a complex molecule is attributed to the isolation effect of the heavy central metal atom. A simplified model involving the skeleton of the complex and one coordinated ligand has been employed for an empirical interpretation of the vibrational spectra. An exact agreement between the number of modes predicted theoretically on the basis of the simplified model and the number of bands observed experimentally has been obtained.

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Wang, Alian, Jingyi Han, Lihe Guo, Jianyuan Yu, and Pei Zeng. "Database of Standard Raman Spectra of Minerals and Related Inorganic Crystals." Applied Spectroscopy 48, no. 8 (August 1994): 959–68. http://dx.doi.org/10.1366/0003702944029640.

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Establishing a standard Raman spectral database for minerals and related inorganic crystals is a very important basis for further increasing the applications of Raman spectroscopy in the geosciences. However, the Raman spectral pattern of a crystal is a function not only of its composition and structure but also of the scattering geometry during the measurement. Therefore, the standard Raman spectrum of a crystal must be measured under well-defined standard conditions. It would be of great interest to establish a standard measuring configuration with which the characteristic Raman spectra of all mineral crystals could be obtained. Factor-group analysis of the main types of minerals indicates that almost all of them possess a Raman-active totally symmetric (TS) vibrational mode. Therefore, we propose a scheme to measure standard Raman spectra under a scattering geometry set up on the basis of these TS modes. Using this scheme, we were able to establish a database for standard Raman spectra of minerals and related inorganic crystals.

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Liu, Fuchao, and Fan Yi. "Spectrally-Resolved Raman Lidar to Measure Atmospheric Three-Phase Water Simultaneously." EPJ Web of Conferences 237 (2020): 06017. http://dx.doi.org/10.1051/epjconf/202023706017.

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We report on a spectrally-resolved Raman lidar that can simultaneously profile backscattered Raman spectrum signals from water vapor, water droplets and ice crystals as well as aerosol fluorescence in the atmosphere. The lidar emits a 354.8-nm ultraviolet laser radiation and samples echo signals in the 393.0-424.0 nm wavelength range with a 1.0-nm spectral resolution. A spectra decomposition method is developed to retrieve fluorescence spectra, water vapor Raman spectra and condensed (liquid and/or ice) water Raman spectra successively. Based on 8 different clear-sky nighttime measurement results, the entire atmospheric water vapor Raman spectra are for the first time obtained by lidar. The measured normalized water vapor Raman spectra are nearly invariant and can serve as background reference for atmospheric water phase state identification under various weather conditions. For an ice virga event, it’s found the extracted condensed water Raman spectra are highly similar in shape to theoretical ice water Raman spectra reported by Slusher and Derr (1975). In conclusion, the lidar provides an effective way to measure three-phase water simultaneously in the atmosphere and to study of cloud microphysics as well as interaction between aerosols and clouds.

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HIGUCHI, Seiichiro. "Measurement of Raman spectra of optical fibers." Journal of the Spectroscopical Society of Japan 34, no. 6 (1985): 381–82. http://dx.doi.org/10.5111/bunkou.34.381.

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Houhou, Rola, Petra Rösch, Jürgen Popp, and Thomas Bocklitz. "Comparison of functional and discrete data analysis regimes for Raman spectra." Analytical and Bioanalytical Chemistry 413, no. 22 (May 15, 2021): 5633–44. http://dx.doi.org/10.1007/s00216-021-03360-1.

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AbstractRaman spectral data are best described by mathematical functions; however, due to the spectroscopic measurement setup, only discrete points of these functions are measured. Therefore, we investigated the Raman spectral data for the first time in the functional framework. First, we approximated the Raman spectra by using B-spline basis functions. Afterwards, we applied the functional principal component analysis followed by the linear discriminant analysis (FPCA-LDA) and compared the results with those of the classical principal component analysis followed by the linear discriminant analysis (PCA-LDA). In this context, simulation and experimental Raman spectra were used. In the simulated Raman spectra, normal and abnormal spectra were used for a classification model, where the abnormal spectra were built by shifting one peak position. We showed that the mean sensitivities of the FPCA-LDA method were higher than the mean sensitivities of the PCA-LDA method, especially when the signal-to-noise ratio is low and the shift of the peak position is small. However, for a higher signal-to-noise ratio, both methods performed equally. Additionally, a slight improvement of the mean sensitivity could be shown if the FPCA-LDA method was applied to experimental Raman data.

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Ito, Hiroaki, Tomokazu Miyazaki, Naoyuki Uragami, Noboru Yokoyama, and Haruhiro Inoue. "Analysis of serum by Raman spectroscopy finds changes in blood metabolites of cancer patients in 45 seconds." Journal of Global Oncology 5, suppl (October 7, 2019): 57. http://dx.doi.org/10.1200/jgo.2019.5.suppl.57.

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57 Background: Cancer is an important disease that accounts for many of the causes of death worldwide, and early diagnosis is important for improving treatment results. In medical care, blood test is a simple and excellent test method, but there is still no cancer blood diagnosis method with high accuracy that can be performed in general hospitals. We are trying to detect cancer patients by analyzing serum using Raman spectroscopy. Methods: Among the outpatients who underwent upper gastrointestinal endoscopy or colonoscopy, 236 subjects who agreed to participate in the study were included. Raman scattering spectra were measured by irradiating a 1064 nm wavelength laser for 15 seconds with serum collected from the subject before endoscopic examination. The average value measured a total of three times was taken as the measured value, and the three measured values were averaged to obtain the value of each examinee. In the obtained Raman scattering spectra, the scattering spectral intensities of the wavelength originating in the specific molecules were analyzed. Results: We were able to obtain clear Raman scattering spectra of all serum samples. When comparing the Raman scattering spectral intensities of the wavelength originating in specific molecules, a large number of serum measurement values were gathered at the center, and the measurement values of the cancer patients' serum were over low or high. By setting the appropriate cutoff line, cancer patients (gastric cancer or colon cancer) and non-cancerous persons could be relatively clearly distinguished (sensitivity, 100%; Specificity, 75%). Conclusions: Our micro Raman system is able to acquire Raman scattering spectra of serum samples. Furthermore, it has been suggested that cancer diagnosis using serum could be possible by comparing the scattering spectral intensities caused by specific molecules. Clinical trial information: UMIN000034306.

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Thomson, G. A., K. J. Baldwin, and D. N. Batchelder. "Raman spectroscopy with simultaneous measurement of two orthogonally polarized Raman spectra." Journal of Raman Spectroscopy 34, no. 5 (2003): 345–49. http://dx.doi.org/10.1002/jrs.991.

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Kleimeyer, James A., and Joel M. Harris. "Monitoring the Formation and Decay of Transient Photosensitized Intermediates Using Pump-Probe UV Resonance Raman Spectroscopy. II: Kinetic Modeling and Multidimensional Least-Squares Analysis." Applied Spectroscopy 57, no. 4 (April 2003): 448–53. http://dx.doi.org/10.1366/00037020360625998.

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Analysis of transient excited-state Raman spectra is a challenging spectroscopic measurement since transient spectral features are often overlapped with dominant ground-state and solvent bands. In the previous manuscript, resolution of component Raman spectra from the time-resolved amine quenching of excited-triplet benzophenone was accomplished using self-modeling curve resolution, a model-free factor analysis technique that relies on correlation in the data along a changing composition dimension. The results are consistent with the production of diphenylketyl radicals by H-atom abstraction from the amine and subsequent free-radical decay by recombination reactions. A kinetic model for this chemistry is developed in the present work, based on the observed Raman scattering data and the structures of product species confirmed by mass spectral analysis. The model is applied to the analysis of the time-dependent Raman scattering data using multidimensional least-squares methods, and it yielded well-resolved spectra of benzophenone excited-triplet states, diphenyl ketyl radical, and the solvent and ground-state precursors. The best-fit kinetic parameters agree well with the time-dependent triplet-state and ketyl-radical concentration profiles.

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Deckert, V., C. Fickert, D. Gernet, P. Vogt, T. Michelis, and W. Kiefer. "Stray Light Rejection in Double Monochromators with Multichannel Detection." Applied Spectroscopy 49, no. 2 (February 1995): 253–55. http://dx.doi.org/10.1366/0003702953963698.

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There is, of course, a disadvantage because of the slightly increasing measurement time since the number of active elements on the multichannel detector is reduced. However, a combination of measurements with small middle slits in the low-frequency Raman region and middle or even wide slit width in the higher-frequency Raman region combined with the use of the full detector size can yield complete Raman spectra in much shorter times than is possible by means of single-channel detection. Appropriate slit setting could be made computer-controlled during a scanning multichannel measurement.

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Sakai, Tetsu, David N. Whiteman, Felicita Russo, David D. Turner, Igor Veselovskii, S. Harvey Melfi, Tomohiro Nagai, and Yuzo Mano. "Liquid Water Cloud Measurements Using the Raman Lidar Technique: Current Understanding and Future Research Needs." Journal of Atmospheric and Oceanic Technology 30, no. 7 (July 1, 2013): 1337–53. http://dx.doi.org/10.1175/jtech-d-12-00099.1.

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Abstract This paper describes recent work in the Raman lidar liquid water cloud measurement technique. The range-resolved spectral measurements at the National Aeronautics and Space Administration Goddard Space Flight Center indicate that the Raman backscattering spectra measured in and below low clouds agree well with theoretical spectra for vapor and liquid water. The calibration coefficients of the liquid water measurement for the Raman lidar at the Atmospheric Radiation Measurement Program Southern Great Plains site of the U.S. Department of Energy were determined by comparison with the liquid water path (LWP) obtained with Atmospheric Emitted Radiance Interferometer (AERI) and the liquid water content (LWC) obtained with the millimeter wavelength cloud radar and water vapor radiometer (MMCR–WVR) together. These comparisons were used to estimate the Raman liquid water cross-sectional value. The results indicate a bias consistent with an effective liquid water Raman cross-sectional value that is 28%–46% lower than published, which may be explained by the fact that the difference in the detectors' sensitivity has not been accounted for. The LWP of a thin altostratus cloud showed good qualitative agreement between lidar retrievals and AERI. However, the overall ensemble of comparisons of LWP showed considerable scatter, possibly because of the different fields of view of the instruments, the 350-m distance between the instruments, and the horizontal inhomogeneity of the clouds. The LWC profiles for a thick stratus cloud showed agreement between lidar retrievals and MMCR–WVR between the cloud base and 150 m above that where the optical depth was less than 3. Areas requiring further research in this technique are discussed.

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Munro, Calum H., Vasil Pajceni, and Sanford A. Asher. "Dielectric Stack Filters for Ex Situ and In Situ UV Optical-Fiber Probe Raman Spectroscopic Measurements." Applied Spectroscopy 51, no. 11 (November 1997): 1722–29. http://dx.doi.org/10.1366/0003702971939424.

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Dielectric stack interference filters can be used in conjunction with a high-throughput single-stage spectrograph to facilitate the measurement of high signal-to-noise (S/N) ultraviolet (UV) Raman spectra with 228.9-nm and 244-nm excitation wavelengths. Placed between the sample and the spectrograph, these filters reflect Rayleigh scattering while transmitting Stokes-shifted Raman scattering. We have measured UV Raman bands from solid, highly scattering samples down to a 290-cm−1 shift from the Rayleigh line. The high throughput of the filtered single-stage spectrograph enables the measurement of UV Raman spectra from photo-labile samples, including DNA and the energetic materials pentaerythritol tetranitrate (PETN) and trinitrotoluene (TNT), with sufficiently low excitation powers and short accumulation times to minimize photo-alteration. High S/N UV preresonance and resonance Raman are obtained for PETN and TNT within 1 s, indicating the possible application of UV Raman spectroscopy as a rapid, highly selective screening methodology for the detection of trace levels of contraband explosives. Furthermore, the incorporation of these dielectric filters within a UV optical-fiber Raman probe head provides simultaneous Rayleigh rejection and removal of background silica Raman scattering. With the use of a 244-nm UV optical-fiber probe, we measured Raman spectra from 100 nM to 10 μM concentrations of polycyclic aromatic hydrocarbon (PAH) in water, even in the presence of an equimolar concentration of the visible fluorophore rhodamine 6G (R6G). Thus, we demonstrate the potential of UV Raman optical-fiber probes for minimally invasive in situ real-time monitoring at low analyte concentrations and within environments in which fluorescence backgrounds would prevent measurements with visible Raman optical-fiber probes.

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Lampel, J., U. Frieß, and U. Platt. "The impact of vibrational Raman scattering of air on DOAS measurements of atmospheric trace gases." Atmospheric Measurement Techniques Discussions 8, no. 3 (March 31, 2015): 3423–69. http://dx.doi.org/10.5194/amtd-8-3423-2015.

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Abstract. In remote sensing applications, such as differential optical absorption spectroscopy (DOAS), atmospheric scattering processes need to be considered. After inelastic scattering on N2 and O2 molecules, the scattered photons occur as additional intensity at a different wavelength, effectively leading to filling-in of both solar Fraunhofer lines and absorptions of atmospheric constituents. Measured spectra in passive DOAS applications are typically corrected for rotational Raman scattering (RRS), also called Ring effect, which represents the main contribution to inelastic scattering. In contrast to that, vibrational Raman scattering (VRS) of N2 and O2 has often been thought to be negligible, but also contributes. Consequences of VRS are red-shifted Fraunhofer structures in scattered light spectra and filling-in of Fraunhofer lines, additional to RRS. We describe how to calculate VRS correction spectra in analogy to the Ring spectrum. We discuss further the impact of VRS cross-sections for O2 and N2 on passive DOAS measurements. The relevance of VRS is shown for the first time in spectral evaluations of Multi-Axis DOAS data. This measurement data yields in agreement with calculated scattering cross-sections, that the observed VRS cross-section amounts to 2.2 ± 0.4% of the cross-section of RRS under tropospheric conditions. It is concluded, that this phenomenon has to be included in the spectral evaluation of weak absorbers as it reduces the measurement error significantly and can cause apparent differential optical depth of up to 2.5 × 10−4. Its influence on the spectral retrieval of IO, Glyoxal, water vapour and NO2 in the blue wavelength range is evaluated. For measurements with a large Ring signal a significant and systematic bias of NO2 dSCDs up to (−3.8 ± 0.4) × 1014 molec cm−2 at low elevation angles is observed if this effect is not considered.

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Panitz, J. C., F. Zimmermann, F. Fischer, W. Häfner, and A. Wokaun. "Near-Infrared Raman Spectroscopy with High Resolution Using the Scanning Multichannel Technique." Applied Spectroscopy 48, no. 4 (April 1994): 454–57. http://dx.doi.org/10.1366/000370294775268884.

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An experimental setup has been developed for the measurement of Raman spectra with NIR excitation, which combines high resolution with multichannel detection. The instrument is based on a Ti:sapphire laser for excitation, a double monochromator, and a CCD detector. The scanning multichannel technique is used for efficient acquisition of Raman spectra. Principal features of the software designed for control of the spectrometer are described, including definition of problem-adapted resolution elements and spike-removal routines. Raman spectra of several compounds are given, demonstrating the good resolution obtainable with this version of NIR Raman spectroscopy.

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Greve, Tanja M., Kristine B. Andersen, and Ole F. Nielsen. "ATR-FTIR, FT-NIR and near-FT-Raman spectroscopic studies of molecular composition in human skinin vivoand pig ear skinin vitro." Spectroscopy 22, no. 6 (2008): 437–57. http://dx.doi.org/10.1155/2008/969217.

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ATR-FTIR, FT-NIR and near-FT-Raman spectroscopy were used to characterize the molecular composition of human skinin vivoand pig ear skinin vitro. Due to different measurement depths the spectroscopic techniques reveal the characteristics of different layers of the skin. Tape stripping was used with the ATR-FTIR technique. Spectral differences concerning lipid content and conformation, protein secondary structure or content of water were found with respect to both gender and species (i.e. human versus pig ear) at all measured skin depths. New assignments of so far unassigned lipid and protein peaks in the FT-NIR and ATR-FTIR spectra of skin were made. PCA and PLS models were used to investigate the division of the recorded spectra into groups. With respect to classification of male and female subjects, the PLS discriminant analysis provided a classification accuracy of 64–93% based on the ATR-FTIR spectra and 83–89% based on the Raman spectra. With respect to classification of human skinin vivoand pig ear skinin vitro, the PLS discriminant analysis provided a classification accuracy of 75–100% based on the Raman spectra and 100% based on the ATR-FTIR spectra.

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Bouř, Petr, Vladimír Baumruk, and Jana Hanzlíková. "Measurement and Calculation of the Raman Optical Activity of α-Pinene and trans-Pinane." Collection of Czechoslovak Chemical Communications 62, no. 9 (1997): 1384–95. http://dx.doi.org/10.1135/cccc19971384.

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Raman scattering and Raman optical activity (ROA) spectra of α-pinene and trans-pinane were measured for both enantiomers. The experiment was performed on a newly built, fully computer-controlled backscattering incident circular polarization ROA instrument. High-quality spectra were obtained and interpreted on the basis of ab initio quantum chemical calculations. Excellent agreement between the calculated and observed spectra was observed in the mid IR region. An approximate distributed origin gauge model for calculation of the polarization tensors was proposed. The shapes of ROA spectra calculated with this model are similar to those obtained with conventional, computationally more demanding ROA computations.

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Kadlečíková, Magdaléna, Juraj Breza, Jozef Liday, Helmut Sitter, and Shaima Al-Baqi. "Raman Spectra of Two Samples of Rubrene Layers." Journal of Electrical Engineering 61, no. 5 (September 1, 2010): 296–98. http://dx.doi.org/10.2478/v10187-010-0044-1.

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Raman Spectra of Two Samples of Rubrene Layers This experimental work deals with measuring Raman spectra of rubrene. The objective is to optimize the measurement procedure of rubrene layers on a substrate. The main outcome of the work is identification of rubrene and of the single-crystalline nature of the measured spots of the rubrene layer.

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Mann, Charles K., and Thomas J. Vickers. "Raman Measurements in the Presence of Fluorescence." Applied Spectroscopy 41, no. 3 (March 1987): 427–30. http://dx.doi.org/10.1366/0003702874449075.

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A method for eliminating the direct effects of fluorescence on Raman spectra is described. It is based upon the differences in widths of Raman and fluorescence peaks and is intended for applications of Raman measurements in chemical analysis. It involves only calculations that are carried out after the measurement has been made and does not require any instrumental enhancement beyond that normally used for Raman measurements. The extent of improvement that can be expected is shown, and the conditions under which its limits are reached are indicated. A technique involving an empirical correction is described which allows extension of these limits in certain cases.

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Kleimeyer, James A., and Joel M. Harris. "Monitoring the Formation and Decay of Transient Photosensitized Intermediates Using Pump-Probe UV Resonance Raman Spectroscopy. I: Self-Modeling Curve Resolution." Applied Spectroscopy 57, no. 4 (April 2003): 439–47. http://dx.doi.org/10.1366/00037020360625989.

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Resolution of transient excited-state Raman scattering from ground-state and solvent bands is a challenging spectroscopic measurement since excited-state spectral features are often of low intensity, overlapping the dominant ground-state and solvent bands. The Raman spectra of these intermediates can be resolved, however, by acquiring time-resolved data and using multidimensional data analysis methods. In the absence of a physical model describing the kinetic behavior of a reaction, resolution of the pure-component spectra from these data can be accomplished using self-modeling curve resolution, a factor analysis technique that relies on the correlation in the data along a changing composition dimension to resolve the component spectra. A two-laser UV pump-probe resonance-enhanced Raman instrument was utilized to monitor the kinetics of amine quenching of excited-triplet states of benzophenone. The formation and decay of transient intermediates were monitored over time, from 15 ns to 100 μs. Factor analysis of the time-resolved spectral data identified three significant components in the data. The time-resolved intensities at each Raman wavenumber shift were projected onto the three significant eigenvectors, and least-squares criteria were developed to find the common plane in the space of the eigenvectors that includes the observed data. Within that plane, the three pure-component spectra were resolved using geometric criteria of convex hull analysis. The resolved spectra were found to arise from benzophenone excited-triplet states, diphenylketyl radicals, and the solvent and ground-state benzophenone.

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Reichardt, Jens, Oliver Behrendt, and Felix Lauermann. "Spectrometric fluorescence and Raman lidar: absolute calibration of aerosol fluorescence spectra and fluorescence correction of humidity measurements." Atmospheric Measurement Techniques 16, no. 1 (January 2, 2023): 1–13. http://dx.doi.org/10.5194/amt-16-1-2023.

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Abstract. RAMSES is the operational spectrometric fluorescence and Raman lidar at the Lindenberg Meteorological Observatory. It employs three spectrometers, with the UVA spectrometer (378–458 nm spectral range) being the latest to be implemented in 2018. The UVA spectrometer extends the fluorescence measurement range to shorter wavelengths than previously accessible, and its water vapor measurements can be corrected for fluorescence effects. First the new experimental setup of the RAMSES near-range receiver, which integrates the UVA spectrometer, is described. Then it is detailed how the fluorescence measurement with the UVA spectrometer is absolutely calibrated and how the fluorescence spectra are merged with those obtained with the second fluorescence spectrometer (440–750 nm spectral range). The second part of this study is dedicated to the effect of aerosol fluorescence on water vapor measurements with Raman lidars. When aerosols are present, a fluorescence-induced error always arises and therefore requires thorough analysis, even though it is particularly significant (in relative terms) only when the atmosphere is dry, the fluorescence signal strong, or the bandwidth of the Raman detection channels wide. For moisture measurements with the UVA spectrometer, a method is introduced that effectively eliminates the systematic fluorescence error. However, the increase in trueness comes at the expense of precision. The investigations further show that an accurate correction for fluorescence is impossible when the Raman lidar is not equipped with a spectrometer but with a single fluorescence receiver channel only, at least for biomass burning aerosol, because for a given fluorescence backscatter coefficient at the wavelength of the auxiliary detection channel, the induced error in humidity can vary widely due to the changing shape of the fluorescence spectrum, which depends on aerosol type and atmospheric state and possibly also on other factors.

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Ootake, Yoshisato, and Serge Kokot. "Discrimination between Glutinous and Non-Glutinous Rice by Vibrational Spectroscopy. I: Comparison of FT-NIR DRIFT, PAS and Raman Spectroscopy." Journal of Near Infrared Spectroscopy 6, no. 1 (January 1998): 241–49. http://dx.doi.org/10.1255/jnirs.143.

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Rice is a major cereal crop in Japan and in Asia. Its taste is determined by such factors as protein and water content as well as stickiness. It has been well established that protein and water content can be estimated by near infrared spectroscopic measurements. However, the measurement of amylose content, which is closely related to rice stickiness, at present, must be carried out by wet chemical methods. Vibrational spectroscopic techniques are possible alternative approaches for the determination of amylose content in rice and, in this paper, we report on the initial steps for the development of methodology for this purpose, namely on the comparison of FT-NIR DRIFT (Diffuse Reflectance Infrared Fourier Transform Spectroscopy), PAS (Photo-Acoustic spectroscopy) and FT-Raman spectroscopy for the discrimination of glutinous and non-glutinous rice. Perkin-Elmer System 2000 FTIR (equipped with DRIFT and PAS accessories) and System 2000 NIR FT-Raman spectrometers were used to collect spectra from ground samples of seven glutinous and 12 non-glutinous rice. When SIMCA (Soft Independent Modelling of Class Analogy) was used to classify raw spectral data, the best discrimination was achieved with the FT-Raman results followed by those from the PAS measurements. FT-Raman spectra of some samples of non-glutinous rice showed strong fluorescence effects. When these samples were excluded from analysis, modelling and classification improved.

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Bai Ying, Lan Yan-Na, and Mo Yu-Jun. "Temperature measurement from the Raman spectra of porous silicon." Acta Physica Sinica 54, no. 10 (2005): 4654. http://dx.doi.org/10.7498/aps.54.4654.

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Watson, Dakota A., Leif O. Brown, Daniel F. Gaskill, Mark Naivar, Steven W. Graves, Stephen K. Doorn, and John P. Nolan. "A flow cytometer for the measurement of Raman spectra." Cytometry Part A 73A, no. 2 (2008): 119–28. http://dx.doi.org/10.1002/cyto.a.20520.

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Dhiman, Abhijeet, Nolan S. Lewis, Ayotomi Olokun, and Vikas Tomar. "Local Shock Properties Measurement Using Time-Resolved Raman Spectroscopy." EPJ Web of Conferences 250 (2021): 01023. http://dx.doi.org/10.1051/epjconf/202125001023.

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In this article, the dynamic response of a heterogeneous microstructure of polymer bonded composite was analyzed to a short duration shock pulse. The composite microstructure studied is a polymerbonded sugar (PBS) with single-crystal sucrose embedded inside the polydimethylsiloxane binder. The shock pulse was created by the impact of the aluminum disk at high speeds using a laser-based projectile launch system. The mechanical response on the microscale domain was measured using ultrafast time-resolved Raman spectroscopy. The in-situ analysis of the change in Raman spectra from PBS during shock compression was captured in the time domain using a streak camera. The results show a steeply rising shock front after the impact where the shock pressure rise time was estimated from the time-resolved Raman spectra. The viscoplastic behavior in the local microscale domain was characterized by quantifying effective shock viscosity measured in the vicinity of the crystal-binder interface.

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Webb, J. D., D. J. Dunlavy, T. Ciszek, R. K. Ahrenkiel, M. W. Wanlass, R. Noufi, and S. M. Vernon. "Room-Temperature Measurement of Photoluminescence Spectra of Semiconductors Using an FT-Raman Spectrophotometer." Applied Spectroscopy 47, no. 11 (November 1993): 1814–19. http://dx.doi.org/10.1366/0003702934066019.

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This paper demonstrates the utility of an FT-Raman accessory for an FT-IR spectrophotometer in obtaining the room-temperature photoluminescence (PL) spectra of semiconductors used in photovoltaic and electro-optical devices. Sample types analyzed by FT-IR/PL spectroscopy included bulk silicon and films of gallium indium arsenide phosphide (GaInAsP), copper indium diselenide (CuInSe2), and gallium arsenide-germanium alloy on various substrates. The FT-IR/PL technique exhibits advantages in speed, sensitivity, and freedom from stray light over conventional dispersive methods, and can be used in some cases to characterize complete semiconductor devices as well as component materials at room temperature. Some suggestions for improving the spectral range of the technique and removing instrumental spectral artifacts are presented.

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Eliasson, C., M. Claybourn, and P. Matousek. "Deep Subsurface Raman Spectroscopy of Turbid Media by a Defocused Collection System." Applied Spectroscopy 61, no. 10 (October 2007): 1123–27. http://dx.doi.org/10.1366/000370207782217770.

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A simple procedure for the recovery of deep subsurface Raman spectra in stratified turbid samples by defocusing a conventional Raman instrument is presented. The method is based on effects present with spatially offset Raman spectroscopy (SORS) and, although not as efficient as the standard SORS approach, it permits a simple way of recovering subsurface Raman spectra from less challenging samples. Demonstration of the effect is performed using a standard SORS device and a commercial Raman instrument on the noninvasive measurement of paracetamol tablets held within a nontransparent white plastic bottle.

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Skonieczny, R., P. Popielarski, W. Bała, K. Fabisiak, K. Paprocki, M. Jancelewicz, M. Kowalska, and M. Szybowicz. "Effect of annealing temperature on optical and electrical properties of metallophthalocyanine thin films deposited on silicon substrate." Materials Science-Poland 34, no. 3 (September 1, 2016): 676–83. http://dx.doi.org/10.1515/msp-2016-0086.

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AbstractThe cobalt phthalocyanine (CoPc) thin films (300 nm thick) deposited on n-type silicon substrate have been studied using micro-Raman spectroscopy, atomic force spectroscopy (AFM) and I-V measurement. The CoPc thin layers have been deposited at room temperature by the quasi-molecular beam evaporation technique. The micro-Raman spectra of CoPc thin films have been recorded in the spectral range of 1000 cm-1 to 1900 cm-1 using 488 nm excitation wavelength. Moreover, using surface Raman mapping it was possible to obtain information about polymorphic forms distribution (before and after annealing) of metallophthalocyanine (α and β form) from polarized Raman spectra. The I-V characteristics of the Au/CoPc/n-Si/Al Schottky barrier were also investigated. The obtained results showed that influence of the annealing process plays a crucial role in the ordering and electrical conductivity of the molecular structure of CoPc thin films deposited on n-type silicon substrate.

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Kim, Jaejin, Jintae Han, Jaegeun Noh, and Hoeil Chung. "Feasibility of a Wide Area Illumination Scheme for Reliable Raman Measurement of Petroleum Products." Applied Spectroscopy 61, no. 7 (July 2007): 686–93. http://dx.doi.org/10.1366/000370207781393253.

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A newly developed Raman collection scheme, a wide area illumination (WAI) scheme, was employed to demonstrate its utility for the analysis of petroleum products. For this purpose, the compositional analysis of simulated naphtha samples was attempted. The WAI scheme utilized a laser beam that illuminated a sample in a circular fashion with a diameter of 6 mm and a focal length of 250 mm. The reproducibility of the Raman measurement can be improved due to decreased sensitivity of the sample position as well as orientation with regard to the focal plane, as shown in a previous study.1 Near-infrared (NIR) spectroscopy, widely adopted in the field of petroleum refining, was also employed to compare with the prediction results obtained using the WAI scheme. Since the Raman spectral feature is more distinct and selective, the resulting calibration accuracy could be improved as long as reproducible Raman spectra could be collected. Overall prediction results using Raman spectroscopy were superior to those from NIR spectroscopy. The feasibility of the WAI scheme for reliable Raman analysis of petroleum products such as naphtha was demonstrated in this paper.

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Tahara, Tahei, and Hiro-O. Hamaguchi. "Picosecond Raman Spectroscopy Using a Streak Camera." Applied Spectroscopy 47, no. 4 (April 1993): 391–98. http://dx.doi.org/10.1366/0003702934335001.

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A Raman measuring system using a streak camera has been constructed. This system consists of a picosecond pulsed laser, an astigmatism-corrected spectrograph, and a streak camera. It enables two-dimensional multichannel detection (time and frequency) of Raman scattering with time resolution as high as 10 ps (without deconvolution). The system was first applied to fluorescence background rejection. Raman spectra of benzene containing a trace amount of Rhodamine 640 were measured. The improvement factor of the Raman-to-fluorescence intensity ratio was estimated as 281, compared with the time-integrated cw measurement. Second, the system was used for picosecond time-resolved Raman spectroscopy. Nanosecond probing laser pulses were used with picosecond pumping. Raman scattering at each delay time was time-resolved and detected by the streak camera. Time-resolved Raman spectra of benzophenone at delay times ranging from −1.25 ns to 1.5 ns were obtained from one single measurement. These results indicate that, if properly designed and properly combined with a suitable optical setup, a streak camera has very high potential for Raman spectroscopy.

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Martin, J. W., M. K. Nieuwoudt, M. J. T. Vargas, O. L. C. Bodley, T. S. Yohendiran, R. N. Oosterbeek, D. E. Williams, and M. Cather Simpson. "Raman on a disc: high-quality Raman spectroscopy in an open channel on a centrifugal microfluidic disc." Analyst 142, no. 10 (2017): 1682–88. http://dx.doi.org/10.1039/c6an00874g.

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Brenan, Colin J. H., and Ian W. Hunter. "Design and Characterization of a Visible-Light Fourier Transform Raman Spectrometer." Applied Spectroscopy 49, no. 8 (August 1995): 1086–93. http://dx.doi.org/10.1366/0003702953965074.

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We demonstrate the feasibility of Fourier transform (FT) Raman spectroscopy with visible wavelength excitation through design, construction, and characterization of a visible-light FT-Raman spectrometer. Our motivation to explore this approach stemmed from the need for a versatile Raman spectrometer for use in a confocal scanning laser Raman microscope we built. We discuss the spectrometer design features which contribute to efficient and reliable microscope operation and evaluate the spectrometer performance on the basis of a series of measurements chosen because of their impact on confocal microscope function. The measurements include the acquisition of representative Raman spectra from both solids and liquids, a demonstration of the independence of resolving power from input aperture diameter, the measurement of the absolute spectrometer optical efficiency curve, and an evaluation of the short- and long-term spectrometer noise processes.

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Torres Filho, Ivo P., James Terner, Roland N. Pittman, Elizabeth Proffitt, and Kevin R. Ward. "Measurement of hemoglobin oxygen saturation using Raman microspectroscopy and 532-nm excitation." Journal of Applied Physiology 104, no. 6 (June 2008): 1809–17. http://dx.doi.org/10.1152/japplphysiol.00025.2008.

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The resonant Raman enhancement of hemoglobin (Hb) in the Q band region allows simultaneous identification of oxy- and deoxy-Hb. The heme vibrational bands are well known at 532 nm, but the technique has never been used to determine microvascular Hb oxygen saturation (So2) in vivo. We implemented a system for in vivo noninvasive measurements of So2. A laser light was focused onto areas of 15–30 μm in diameter. Using a microscope coupled to a spectrometer and a cooled detector, Raman spectra were obtained in backscattering geometry. Calibration was performed in vitro using blood at several Hb concentrations, equilibrated at various oxygen tensions. So2 was estimated by measuring the intensity of Raman signals (peaks) in the 1,355- to 1,380-cm−1 range (oxidation state marker band ν4), as well as from the ν19 and ν10 bands (1,500- to 1,650-cm−1 range). In vivo observations were made in microvessels of anesthetized rats. Glass capillary pathlength and Hb concentration did not affect So2 estimations from Raman spectra. The Hb Raman peaks observed in blood were consistent with earlier Raman studies using Hb solutions and isolated cells. The correlation between Raman-based So2 estimations and So2 measured by CO-oximetry was highly significant for ν4, ν10, and ν19 bands. The method allowed So2 determinations in all microvessel types, while diameter and erythrocyte velocity could be measured in the same vessels. Raman microspectroscopy has advantages over other techniques by providing noninvasive and reliable in vivo So2 determinations in thin tissues, as well as in solid organs and tissues in which transillumination is not possible.

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Tsukamoto, Ikuko, Hisako Nagai, and Katsunosuke Machida. "Intensity measurement of resonance Raman spectra of dye solutions with the divided Raman cell." Journal of Raman Spectroscopy 17, no. 4 (August 1986): 313–16. http://dx.doi.org/10.1002/jrs.1250170403.

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Hurst, Wilbur S., Steven J. Choquette, and Edgar S. Etz. "Requirements for Relative Intensity Correction of Raman Spectra Obtained by Column-Summing Charge-Coupled Device Data." Applied Spectroscopy 61, no. 7 (July 2007): 694–700. http://dx.doi.org/10.1366/000370207781393235.

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The relative intensity correction of Raman spectra requires the measurement of a source of known relative irradiance. Raman spectrometers that employ two-dimensional charge-coupled device (CCD) array detectors may be operated in two distinct modes. One mode directly measures the counts in each CCD pixel, but more commonly for the collection of spectra, the counts in the CCD row pixels are summed for a given column. If distortions in the corrected spectral shapes are to be avoided, operation in the mode where rows are summed places restrictions on the spatial intensity profile of the source of known irradiance that is used for the relative intensity correction procedure and, in some cases, also on the spatial intensity profile of the measured Raman light. Numerical expressions are given from which these restrictions can be derived. Magnitudes of distortions that can arise when intensity-correcting spectra obtained with CCD data where rows in a column are summed are estimated by modeling different cases. Data are given showing the inherent pixel quantum efficiency variation that exists in CCDs. Spectra are given showing the effects of a local area of significant change in pixel quantum efficiency that was found to be present on one CCD detector.

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Lázaro, João Carlos, Marcos Tadeu T. Pacheco, Kátia Calligaris Rodrigues, Carlos José de Lima, Leonardo Marmo Moreira, Antonio Balbin Villaverde, and Landulfo Silveira Jr. "Optimizing the Raman signal for characterizing organic samples: The effect of slit aperture and exposure time." Spectroscopy 23, no. 2 (2009): 71–80. http://dx.doi.org/10.1155/2009/764524.

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The present work is focused on the influence of the slit aperture and time exposure of the infrared light on the Charge Coupled Device (CCD) in relation to their physical effects, in order to improve the Raman spectrum characteristics. Indeed, the alterations in slit aperture and CCD time exposure affect significantly important spectral properties, such as the spectral intensity, Signal to Noise Ratio (SNR) and band width resolution of the Raman spectra. Therefore, the present proposal has the aim of to found the optimum conditions of instrumental arrangement, involving the minimum collection time and maximum signal quality in dispersive Raman spectrometers. Samples of dehydrated human teeth and naphthalene were evaluated with a Raman dispersive spectrometer employing excitation wavelength of 830 nm in several integration times and spectrometer slit apertures. The analysis of the spectral intensity, SNR and band width of selected Raman peaks allowed to infer that these properties of a dispersive Raman spectrum depend directly of the exposure time on the detector as well as spectrograph slit aperture. It is important to register that the higher SNR was obtained with higher exposure time intervals. To the samples evaluated in the present article, the band width has lower values for slit apertures of 100–150 μm, i.e., in this aperture range the spectral resolution is maximum. On the publisher-id hand, the intensity and SNR of the Raman spectra becomes optimal for slit apertures of 150–200 μm, since this aperture does not affect significantly the integrity of the Raman signal. In this way, we can to propose that in approximately 150 μm, it is possible to obtain an optimum condition, involving spectral resolution as well as SNR and spectral intensity. In any case, depending of the priorities of each spectral measurement, the instrumental conditions can be altered according with the necessities of each specific chemical analysis involving a determined sample. The present data are discussed in details in agreement with recent data from literature.

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Li, Nan, Hang Zang, Huimin Sun, Xianzhi Jiao, Kangkang Wang, Timon Cheng-Yi Liu, and Yaoyong Meng. "A Noninvasive Accurate Measurement of Blood Glucose Levels with Raman Spectroscopy of Blood in Microvessels." Molecules 24, no. 8 (April 17, 2019): 1500. http://dx.doi.org/10.3390/molecules24081500.

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Raman spectra of human skin obtained by laser excitation have been used to non-invasively detect blood glucose. In previous reports, however, Raman spectra thus obtained were mainly derived from the epidermis and interstitial fluid as a result of the shallow penetration depth of lasers in skin. The physiological process by which glucose in microvessels penetrates into the interstitial fluid introduces a time delay, which inevitably introduces errors in transcutaneous measurements of blood glucose. We focused the laser directly on the microvessels in the superficial layer of the human nailfold, and acquired Raman spectra with multiple characteristic peaks of blood, which indicated that the spectra obtained predominantly originated from blood. Incorporating a multivariate approach combining principal component analysis (PCA) and back propagation artificial neural network (BP-ANN), we performed noninvasive blood glucose measurements on 12 randomly selected volunteers, respectively. The mean prediction performance of the 12 volunteers was obtained as an RMSEP of 0.45 mmol/L and R2 of 0.95. It was no time lag between the predicted blood glucose and the actual blood glucose in the oral glucose tolerance test (OGTT). We also applied the procedure to data from all 12 volunteers regarded as one set, and the total predicted performance was obtained with an RMSEP of 0.27 mmol/L and an R2 of 0.98, which is better than that of the individual model for each volunteer. This suggested that anatomical differences between volunteer fingernails do not reduce the prediction accuracy and 100% of the predicted glucose concentrations fall within Region A and B of the Clarke error grid, allowing acceptable predictions in a clinically relevant range. The Raman spectroscopy detection of blood glucose from microvessels is of great significance of non-invasive blood glucose detection of Raman spectroscopy. This innovative method may also facilitate non-invasive detection of other blood components.

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Reichardt, Jens. "Cloud and Aerosol Spectroscopy with Raman Lidar." Journal of Atmospheric and Oceanic Technology 31, no. 9 (September 1, 2014): 1946–63. http://dx.doi.org/10.1175/jtech-d-13-00188.1.

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Abstract A spectrometer for height-resolved measurements of the Raman backscatter-coefficient spectrum of water in its gaseous and condensed phases is presented. The spectrometer is fiber coupled to the far-range receiver of the Raman Lidar for Atmospheric Moisture Sensing (RAMSES) of the German Meteorological Service and consists of a Czerny–Turner spectrograph (500-mm focal length) and a 32-channel single-photon-counting detection system based on a multianode photomultiplier. During a typical measurement (transmitter wavelength of 355 nm), the spectrum between 385 and 410 nm is recorded with a spectral resolution of 0.79 nm; the vertical resolution is 15 m and the height range is 15 km. The techniques outlined are those that are applied to calibrate the spectrum measurement and to monitor fluorescence by atmospheric aerosols that have the potential to interfere with the water observation. For the first time, Raman spectra of liquid-water, mixed-phase, and cirrus clouds are reported, and their temperature dependence is investigated by means of band decomposition. The spectrum-integrated condensed-water Raman backscatter coefficient strongly depends on cloud particle volume, but it is not tightly correlated with the cloud optical properties (particle extinction and backscatter coefficient), which implies that retrieval of cloud water content from optical proxies is likely impossible. Aerosol measurements are also discussed. Depending on type, aerosols may show no backscattering in the spectrometer range at all, or a featureless spectrum that stems quite likely from fluorescence. Finally, the example of a cloud forming in an aerosol layer demonstrates that the new instrument not only opens up new perspectives in cloud research but also contributes to studies of cloud–aerosol interaction.

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Sakurai, Toshimitsu, Hiroshi Ohno, Shinichiro Horikawa, Yoshinori Iizuka, Tsutomu Uchida, and Takeo Hondoh. "A Technique for Measuring Microparticles in Polar Ice Using Micro-Raman Spectroscopy." International Journal of Spectroscopy 2010 (August 18, 2010): 1–7. http://dx.doi.org/10.1155/2010/384956.

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We describe in detail our method of measuring the chemical forms of microparticles in polar ice samples through micro-Raman spectroscopy. The method is intended for solid ice samples, an important point because melting the ice can result in dissociation, contamination, and chemical reactions prior to or during a measurement. We demonstrate the technique of measuring the chemical forms of these microparticles and show that the reference spectra of those salts expected to be common in polar ice are unambiguously detected. From our measurements, Raman intensity of sulfate salts is relatively higher than insoluble dust due to the specific Raman scattering cross-section of chemical forms of microparticles in ice.

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Perez-Pueyo, R., M. J. Soneira, M. Castanys, and S. Ruiz-Moreno. "Fuzzy Approach for Identifying Artistic Pigments with Raman Spectroscopy." Applied Spectroscopy 63, no. 8 (August 2009): 947–57. http://dx.doi.org/10.1366/000370209788964412.

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In this work, a fuzzy approach for automatically identifying artistic pigments from their Raman spectra is presented. The uncertainty introduced during the Raman spectrum measurement of pigments is considered in the design of the fuzzy system. The position of the Raman bands in the unknown spectrum can be subject to small displacements due to noise, misalignments in the calibration, etc. Fuzzy logic allows us to work with this uncertainty and to design a system based on the comparison between the Raman band positions in an unknown spectrum recorded from an artwork and the Raman band positions in spectra recorded from reference pigments gathered in databases. The fuzzy system provides the reference pigments whose Raman band positions match those of the unknown pigment analyzed and gives guidance to the decision-making process in the final identification.

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JIA, TING-JIAN, GE SONG, PENG-WEI LI, TING-CHAO HE, YU-JUN MO, and YU-TING CUI. "VIBRATIONAL MODES STUDY OF METHYL ORANGE USING SERS-MEASUREMENT AND THE DFT METHOD." Modern Physics Letters B 22, no. 29 (November 20, 2008): 2869–79. http://dx.doi.org/10.1142/s0217984908017345.

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This paper experimentally observes the Normal Raman spectrum (NRS) and infrared absorption spectrum of methyl orange (MO) and presents theoretical vibrational spectra calculated from a density functional theory (DFT) method on the basis of B3LYP with 6–31 basis set. The calculated results show very good agreement with the experimentally observed IR and Raman frequencies. We also report the surface enhanced Raman spectrum (SERS) of MO adsorbed on silver nanoparticles surface. Finally, the possible adsorbed state of MO on the silver nanoparticles surface is discussed.

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Vlčková, Blanka, Bohuslav Strauch, and Milan Horák. "Measurement and interpretation of infrared and raman spectra of bis(2,4-pentandionate)complexes of Cu(II) and Pd(II)." Collection of Czechoslovak Chemical Communications 50, no. 2 (1985): 306–16. http://dx.doi.org/10.1135/cccc19850306.

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Infrared and Raman spectra of Cu(II) bis(2,4-pentandionate) and Pd(II) bis(2,4-pentandionate) complexes have been measured and interpreted. The coincidence of numerous bands in the IR and Raman spectra has been explained by the isolation effect of the heavy central metal atom which prevents the vibrational interaction of the two ligands in the chelate molecule with each other. An 11-particle model consisting of all the atoms of one ligand (both CH3 groups are taken as the point masses), a central metal atom and two oxygen atoms of the other ligand has been proved to be most adequate for the empirical interpretation of the spectra.

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Sinjab, Faris, Giovanna Sicilia, Dustin W. Shipp, Maria Marlow, and Ioan Notingher. "Label-Free Raman Hyperspectral Imaging of Single Cells Cultured on Polymer Substrates." Applied Spectroscopy 71, no. 12 (August 22, 2017): 2595–607. http://dx.doi.org/10.1177/0003702817715042.

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While Raman hyperspectral imaging has been widely used for label-free mapping of biomolecules in cells, these measurements require the cells to be cultured on weakly Raman scattering substrates. However, many applications in biological sciences and engineering require the cells to be cultured on polymer substrates that often generate large Raman scattering signals. Here, we discuss the theoretical limits of the signal-to-noise ratio in the Raman spectra of cells in the presence of polymer signals and how optical aberrations may affect these measurements. We show that Raman spectra of cells cultured on polymer substrates can be obtained using automatic subtraction of the polymer signals and demonstrate the capabilities of these methods in two important applications: tissue engineering and in vitro toxicology screening of drugs. Apart from their scientific and technological importance, these applications are examples of the two most common measurement configurations: (1) cells cultured on an optically thick polymer substrate measured using an immersion/dipping objective; and (2) cells cultured on a transparent polymer substrate and measured using an inverted optical microscope. In these examples, we show that Raman hyperspectral data sets with sufficient quality can be successfully acquired to map the distribution of common biomolecules in cells, such as nucleic acids, proteins, and lipids, as well as detecting the early stages of apoptosis. We also discuss strategies for further improvements that could expand the application of Raman hyperspectral imaging on polymer substrates even further in biomedical sciences and engineering.

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Reichardt, Jens, Christine Knist, Natalia Kouremeti, William Kitchin, and Taras Plakhotnik. "Accurate Absolute Measurements of Liquid Water Content (LWC) and Ice Water Content (IWC) of Clouds and Precipitation with Spectrometric Water Raman Lidar." Journal of Atmospheric and Oceanic Technology 39, no. 2 (February 2022): 163–80. http://dx.doi.org/10.1175/jtech-d-21-0077.1.

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Abstract A detailed description is given of how the liquid water content (LWC) and the ice water content (IWC) can be determined accurately and absolutely from the measured water Raman spectra of clouds. All instrumental and spectroscopic parameters that affect the accuracy of the water-content measurement are discussed and quantified; specifically, these are the effective absolute differential Raman backscattering cross section of water vapor , and the molecular Raman backscattering efficiencies ηliq and ηice of liquid and frozen microparticles, respectively. The latter two are determined following rigorous theoretical approaches combined with Raman Lidar for Atmospheric Moisture Sensing (RAMSES) measurements. For ηice, this includes a new experimental method that assumes continuity of the number of water molecules across the vertical extent of the melting layer. Examples of water-content measurements are presented, including supercooled liquid-water clouds and melting layers. Error sources are discussed; one effect that stands out is interfering fluorescence by aerosols. Aerosol effects and calibration issues are the main reasons why spectral Raman measurements are required for quantitative measurements of LWC and IWC. The presented study lays the foundation for cloud microphysical investigations and for the evaluation of cloud models or the cloud data products of other instruments. As a first application, IWC retrieval methods are evaluated that are based on either lidar extinction or radar reflectivity measurements. While the lidar-based retrievals show unsatisfactory agreement with the RAMSES IWC measurements, the radar-based IWC retrieval which is used in the Cloudnet project performs reasonably well. On average, retrieved IWC agrees within 20% to 30% (dry bias) with measured IWC.

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Bandeliuk, Oleksandra, Ali Assaf, Marine Bittel, Marie-Jose Durand, and Gérald Thouand. "Development and Automation of a Bacterial Biosensor to the Targeting of the Pollutants Toxic Effects by Portable Raman Spectrometer." Sensors 22, no. 12 (June 8, 2022): 4352. http://dx.doi.org/10.3390/s22124352.

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Water quality monitoring requires a rapid and sensitive method that can detect multiple hazardous pollutants at trace levels. This study aims to develop a new generation of biosensors using a low-cost fiber-optic Raman device. An automatic measurement system was thus conceived, built and successfully tested with toxic substances of three different types: antibiotics, heavy metals and herbicides. Raman spectroscopy provides a multiparametric view of metabolic responses of biological organisms to these toxic agents through their spectral fingerprints. Spectral analysis identified the most susceptible macromolecules in an E. coli model strain, providing a way to determine specific toxic effects in microorganisms. The automation of Raman analysis reduces the number of spectra required per sample and the measurement time: for four samples, time was cut from 3 h to 35 min by using a multi-well sample holder without intervention from an operator. The correct classifications were, respectively, 99%, 82% and 93% for the different concentrations of norfloxacin, while the results were 85%, 93% and 81% for copper and 92%, 90% and 96% for 3,5-dichlorophenol at the three tested concentrations. The work initiated here advances the technology needed to use Raman spectroscopy coupled with bioassays so that together, they can advance field toxicological testing.

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Zolotoukhina, Tatiana, Momoko Yamada, and Shingo Iwakura. "Vibrational Spectra of Nucleotides in the Presence of the Au Cluster Enhancer in MD Simulation of a SERS Sensor." Biosensors 11, no. 2 (January 29, 2021): 37. http://dx.doi.org/10.3390/bios11020037.

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Surface-enhanced Raman scattering (SERS) nanoprobes have shown tremendous potential in in vivo imaging. The development of single oligomer resolution in the SERS promotes experiments on DNA and protein identification using SERS as a nanobiosensor. As Raman scanners rely on a multiple spectrum acquisition, faster imaging in real-time is required. SERS weak signal requires averaging of the acquired spectra that erases information on conformation and interaction. To build spectral libraries, the simulation of measurement conditions and conformational variations for the nucleotides relative to enhancer nanostructures would be desirable. In the molecular dynamic (MD) model of a sensing system, we simulate vibrational spectra of the cytosine nucleotide in FF2/FF3 potential in the dynamic interaction with the Au20 nanoparticles (NP) (EAM potential). Fourier transfer of the density of states (DOS) was performed to obtain the spectra of bonds in reaction coordinates for nucleotides at a resolution of 20 to 40 cm−1. The Au20 was optimized by ab initio density functional theory with generalized gradient approximation (DFT GGA) and relaxed by MD. The optimal localization of nucleotide vs. NP was defined and the spectral modes of both components vs. interaction studied. Bond-dependent spectral maps of nucleotide and NP have shown response to interaction. The marker frequencies of the Au20—nucleotide interaction have been evaluated.

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Zolotoukhina, Tatiana, Momoko Yamada, and Shingo Iwakura. "Influence of the Au Cluster Enhancer on Vibrational Spectra of Nucleotides in MD Simulation of a SERS Sensor." Proceedings 60, no. 1 (November 2, 2020): 25. http://dx.doi.org/10.3390/iecb2020-07076.

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Surface-enhanced Raman scattering (SERS) nanoprobes have shown tremendous potential in in vivo imaging. The development of single oligomer resolution in the SERS promotes experiments on DNA and protein identification using SERS as a nanobiosensor. As Raman scanners rely on a multiple spectrum acquisition, the faster imaging in real-time is required. SERS weak signal requires averaging of the acquired spectra that erases information on conformation and interaction. To build spectral libraries, the simulation of measurement conditions and conformational variations for the nucleotides relative to enhancer nanostructures would be desirable. In the molecular dynamic (MD) model of a sensing system, we simulate vibrational spectra of the cytosine nucleotide in FF2/FF3 potential in the dynamic interaction with the Au20 nanoparticles (NP) (EAM potential). Fourier transfer of the density of states (DOS) was performed to obtain the spectra of bonds in reaction coordinates for nucleotides at a resolution 20 to 40 cm−1. The Au20 was optimized by ab initio DFT GGA and relaxed by MD. The optimal localization of nucleotide vs. NP was defined and spectral modes of both components vs. interaction studied. Bond-dependent spectral maps of nucleotide and NP have shown response to interaction. The marker frequencies of the Au20—nucleotide interaction have been evaluated.

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Journal articles on the topic 'Raman spectra measurement'

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