Готові списки джерел за темами / Ultrafast Raman Loss Spectroscopic Studies

Добірка наукової літератури з теми "Ultrafast Raman Loss Spectroscopic Studies"

Автор: Grafiati

Опубліковано: 6 вересня 2023

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Статті в журналах з теми "Ultrafast Raman Loss Spectroscopic Studies"

Kayal, Surajit, Khokan Roy, and Siva Umapathy. "Femtosecond coherent nuclear dynamics of excited tetraphenylethylene: Ultrafast transient absorption and ultrafast Raman loss spectroscopic studies." Journal of Chemical Physics 148, no. 2 (January 14, 2018): 024301. http://dx.doi.org/10.1063/1.5008726.

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Kayal, Surajit, Khokan Roy, Y. Adithya Lakshmanna, and Siva Umapathy. "Probing the effect of solvation on photoexcited 2-(2′-hydroxyphenyl)benzothiazole via ultrafast Raman loss spectroscopic studies." Journal of Chemical Physics 149, no. 4 (July 28, 2018): 044310. http://dx.doi.org/10.1063/1.5028274.

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Katturi, Naga Krishnakanth, Sarang Dev G, Nagarjuna Kommu, Gopala Krishna Podagatlapalli, and Venugopal Rao Soma. "Ultrafast Coherent Anti-Stokes Raman spectroscopic studies of nitro/nitrogen rich aryl-tetrazole derivatives." Chemical Physics Letters 756 (October 2020): 137843. http://dx.doi.org/10.1016/j.cplett.2020.137843.

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Kipkemboi, Pius K., and Allan J. Easteal. "Vibrational spectroscopic studies of aqueous solutions of tert-butyl alcohol and tert-butylamine." Canadian Journal of Chemistry 80, no. 7 (July 1, 2002): 789–95. http://dx.doi.org/10.1139/v02-102.

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Raman and FT-IR absorption spectra of aqueous tert-butyl alcohol (t-BuOH) and tert-butylamine (t-BuNH2) in the region of the OH and NH2 stretching and bending modes have been measured as a function of organic co-solvent concentration in the whole co-solvent mole fraction region. The major observed changes of the aqueous binary solution spectra compared with the solvent spectra are a loss or gain of band intensity. In particular, the observed changes in intensities and linewidths of some bands were significantly more pronounced at low concentrations of organic co-solvents in water, where t-BuOH and t-BuNH2 tend to integrate into the water structure. Clear evidence of structural enhancement of the network is obtained in dilute solutions as well as destruction of the network by hydrophobic interactions as the concentration is increased. Generally, the interpretation of the spectra is in agreement with the capacity of the hydrophobic co-solvent to break the structure of water in the more concentrated aqueous solutions and to enhance the structure in dilute solutions. Vibrational intensities and frequency shifts of some bands show definite trends with varying the concentration of the solutions. In the concentration-dependence study, unusual linewidth changes of certain bands were observed.Key words: infrared, Raman spectra, aqueous, tert-butanol, tert-butylamine.

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Sokaras, Dimosthenis, Tsu-Chien Weng, Dennis Nordlund, and Uwe Bergmann. "High Energy Resolution X-ray Spectroscopy at SSRL and LCLS: Instruments and Applications." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C223. http://dx.doi.org/10.1107/s2053273314097769.

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High-resolution hard x-ray spectroscopies (XES, HERFD, RIXS, XRS) are now well-established characterization tools for providing insights of material's electronic and geometric structure. The high brilliance synchrotron radiation beamlines have made feasible the routine study of the electronic structure and ligand environment of metal coordination compounds and active centers in metalloproteins, electrochemical process under in-situ conditions, as well as studies on catalytic systems under ambient conditions. Moreover, the recent availability of Linac Coherent Light Source (LCLS), provides some unique opportunities for the study of ultrafast electronic structure dynamics in various phenomena such as electron transfer processes, transient molecular states, molecular dissociation, etc. At SLAC National Accelerator Laboratory we have developed recently a set of high-resolution x-ray spectroscopic capabilities based on various multicrystal spectrometers. At SSRL we have built three multicrystal Johann spectrometers enabling XES/RIXS/HERDF techniques as well as X-ray Raman Spectroscopy. For LCLS, we have developed an energy dispersive multicrystal von Hamos spectrometer that records simultaneously the overall emission spectrum, enabling shot-by-shot time-resolved studies. Representative examples of application will be shown and discussed from the ongoing spectroscopy programs of SSRL and LCLS.

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Isabelle, M., N. Stone, H. Barr, M. Vipond, N. Shepherd, and K. Rogers. "Lymph node pathology using optical spectroscopy in cancer diagnostics." Spectroscopy 22, no. 2-3 (2008): 97–104. http://dx.doi.org/10.1155/2008/871940.

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Raman and infrared spectroscopy are optical spectroscopic techniques that use light scattering (Raman) and light absorption (infrared) to probe the vibrational energy levels of molecules in tissue samples. Using these techniques, one can gain an insight into the biochemical composition of cells and tissues by looking at the spectra produced and comparing them with spectra obtained from standards such as proteins, nucleic acids, lipids and carbohydrates. As a result of optical spectroscopy being able to measure these biochemical changes, diagnosis of cancer could take place faster than current diagnostic methods, assisting and offering pathologists and cytologists a novel technology in cancer screening and diagnosis.The purpose of this study is to use both spectroscopic techniques, in combination with multivariate statistical analysis tools, to analyze some of the major biochemical and morphological changes taking place during carcinogenesis and metastasis in lymph nodes and to develop a predictive model to correctly differentiate cancerous from benign lymph nodes taken from oesophageal cancer patients.The results of this study showed that Raman and infrared spectroscopy managed to correctly differentiate between cancerous and benign oesophageal lymph nodes with a training performance greater than 94% using principal component analysis (PCA)-fed linear discriminant analysis (LDA). Cancerous nodes had higher nucleic acid but lower lipid and carbohydrate content compared to benign nodes which is indicative of increased cell proliferation and loss of differentiation.With better understanding of the molecular mechanisms of carcinogenesis and metastasis together with use of multivariate statistical analysis tools, these spectroscopic studies will provide a platform for future development of real-time (in surgery) non-invasive diagnostic tools in medical research.

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Towrie, Michael, David C. Grills, Joanne Dyer, Julia A. Weinstein, Pavel Matousek, Robin Barton, Philip D. Bailey, et al. "Development of a Broadband Picosecond Infrared Spectrometer and its Incorporation into an Existing Ultrafast Time-Resolved Resonance Raman, UV/Visible, and Fluorescence Spectroscopic Apparatus." Applied Spectroscopy 57, no. 4 (April 2003): 367–80. http://dx.doi.org/10.1366/00037020360625899.

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We have constructed a broadband ultrafast time-resolved infrared (TRIR) spectrometer and incorporated it into our existing time-resolved spectroscopy apparatus, thus creating a single instrument capable of performing the complementary techniques of femto-/picosecond time-resolved resonance Raman (TR3), fluorescence, and UV/visible/infrared transient absorption spectroscopy. The TRIR spectrometer employs broadband (150 fs, ∼150 cm−1 FWHM) mid-infrared probe and reference pulses (generated by difference frequency mixing of near-infrared pulses in type I AgGaS2), which are dispersed over two 64-element linear infrared array detectors (HgCdTe). These are coupled via custom-built data acquisition electronics to a personal computer for data processing. This data acquisition system performs signal handling on a shot-by-shot basis at the 1 kHz repetition rate of the pulsed laser system. The combination of real-time signal processing and the ability to normalize each probe and reference pulse has enabled us to achieve a high sensitivity on the order of ΔOD ∼ 10−4–10−5 with 1 min of acquisition time. We present preliminary picosecond TRIR studies using this spectrometer and also demonstrate how a combination of TRIR and TR3 spectroscopy can provide key information for the full elucidation of a photochemical process.

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Ho, Junming, Elizabeth Kish, Dalvin D. Méndez-Hernández, Katherine WongCarter, Smitha Pillai, Gerdenis Kodis, Jens Niklas, et al. "Triplet–triplet energy transfer in artificial and natural photosynthetic antennas." Proceedings of the National Academy of Sciences 114, no. 28 (June 26, 2017): E5513—E5521. http://dx.doi.org/10.1073/pnas.1614857114.

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In photosynthetic organisms, protection against photooxidative stress due to singlet oxygen is provided by carotenoid molecules, which quench chlorophyll triplet species before they can sensitize singlet oxygen formation. In anoxygenic photosynthetic organisms, in which exposure to oxygen is low, chlorophyll-to-carotenoid triplet–triplet energy transfer (T-TET) is slow, in the tens of nanoseconds range, whereas it is ultrafast in the oxygen-rich chloroplasts of oxygen-evolving photosynthetic organisms. To better understand the structural features and resulting electronic coupling that leads to T-TET dynamics adapted to ambient oxygen activity, we have carried out experimental and theoretical studies of two isomeric carotenoporphyrin molecular dyads having different conformations and therefore different interchromophore electronic interactions. This pair of dyads reproduces the characteristics of fast and slow T-TET, including a resonance Raman-based spectroscopic marker of strong electronic coupling and fast T-TET that has been observed in photosynthesis. As identified by density functional theory (DFT) calculations, the spectroscopic marker associated with fast T-TET is due primarily to a geometrical perturbation of the carotenoid backbone in the triplet state induced by the interchromophore interaction. This is also the case for the natural systems, as demonstrated by the hybrid quantum mechanics/molecular mechanics (QM/MM) simulations of light-harvesting proteins from oxygenic (LHCII) and anoxygenic organisms (LH2). Both DFT and electron paramagnetic resonance (EPR) analyses further indicate that, upon T-TET, the triplet wave function is localized on the carotenoid in both dyads.

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Shetty, Karthika, Jayadev, Kalyan Raj, and H. C. Ananda Murthy. "Evaluation of Electrochemical and Anticorrosion Properties of Polyaniline-Fly Ash Nanocomposite." International Journal of Corrosion 2021 (December 20, 2021): 1–10. http://dx.doi.org/10.1155/2021/1547384.

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In India, the thermal station generates approximately 6.9 × 10 7 tons of fly ash (FA) as a waste by-product. As part of this work, little attempt was made to produce useful materials from waste material. In our current research, polyaniline- (PANI-) fly ash (FA) nanocomposite (PFNC) was synthesized using an in situ polymerization method. The synthesized composites were characterized by employing advanced analytical, microscopic, and spectroscopic tools. The results of the X-ray diffraction (XRD) analysis confirm the effective reinforcement of FA into PANI in PFNC. The presence of functional groups in PFNC has been confirmed by Raman and FT-IR spectroscopic techniques. The SEM micrographs of the nanocomposite revealed the presence of agglomerated and fragmented structures in PFNC. The weight loss for PFNC was observed to occur in three stages as revealed by thermogravimetric analysis (TGA). UV-visible spectra for PFNC proved that FA stabilized the PANI in emeraldine form. Electrodynamic polarization studies were conducted to explore the corrosion resistance of nanocomposite-coated mild steel. The corrosion current density ( i corr ) for PFNC-coated mild steel (MS) specimens was found to decrease when compared to the bare substrate, indicating superior corrosion resistance in PFNC-coated substrate. Similarly, Tafel and cyclic polarization studies too confirmed superior anticorrosion property for MS coated with PFNC.

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Al-Hajji, Latifa A., Muhammad A. Hasan, and Mohamed I. Zaki. "Kinetic and characterization studies of the formation of barium monomolybdate in equimolar powder mixture of BaCO3 and MoO3." Journal of Materials Research 18, no. 10 (October 2003): 2339–49. http://dx.doi.org/10.1557/jmr.2003.0328.

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The formation of barium monomolybdate (BaMoO4) in inequimolar powder mixtures of BaCO3 and MoO3 was examined under isothermal and nonisothermal conditions upon heating in air at 25–1200 °C, using thermogravimetry. Concurrence of the observed mass loss (due to the release of CO2) to the occurrence of the formation reaction was evident. Accordingly, the extent of reaction (x) was determined as a function of time (t) or temperature (T). The x-t and x-T data thus obtained were processed using a well-established mathematical apparatus and methods to characterize the nature of the reaction rate-determining step and derive isothermal and nonisothermal kinetic parameters (rate constant, frequency factor, reaction order, and activation energy). Moreover, the reaction mixture quenched at various temperatures (450–575 °C) in the reaction course was analyzed by various spectroscopic (x-ray diffractometry, infrared spectroscopy, and laser Raman spectroscopy) and microscopic (scanning electron microscopy and x-ray energy dispersive spectroscopy) techniques for material characterization. The results obtained indicated that the reaction rate may be controlled by unidirectional diffusion of MoO3 species through the product layer (BaMoO4), which was implied to form on the barium carbonate particles. The nonisothermally determined activation energy (156 kJ/mol) was found to be close to the isothermally determined one (164–166 kJ/mol)

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Дисертації з теми "Ultrafast Raman Loss Spectroscopic Studies"

Mallick, Babita. "Ultrafast Raman Loss Spectroscopic Investigations of Excited State Structural Dynamics of Bis(phenylethynyl)benzene and trans-Stilbene." Thesis, 2017. http://etd.iisc.ernet.in/2005/3610.

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The subject of this thesis is the design and development of a unified set up for femtosecond transient absorption and ultrafast Raman loss spectroscopy and demonstrate its potential in capturing the ultrafast photophysical and photochemical processes with excellent time and frequency resolution. Ultrafast spectroscopy has been serving as a powerful tool for understanding the structural dynamical properties of molecules in the condensed and gas phase. The advent of ultrashort pulses with their high peak power enables the laser spectroscopic community to study molecular reaction dynamics and photophysics that happen at extremely short timescales, ranging from picosecond to femtosecond. These processes can be measured with extremely high time resolution, which helps to resolve the under-lying molecular process. But in order to understand the global mechanism of the underlying molecular processes, we have to resolve the nuclear dynamics with the proper frequency resolution. However, achieving both, time and frequency resolutions simultaneously is not possible according to the Heisenberg uncertainty principle. Later, this limitation was overcome by femtosecond stimulated Raman spectroscopy (FSRS), a third order non-linear Raman spectroscopy. In this thesis we introduced the ultrafast Raman loss spectroscopic (URLS) technique which is analogous to FSRS, offering the modern ultrafast community to resolve molecular processes with better signal-to-noise ratio along with proper time and frequency resolution. We demonstrate the experimental procedure including the single shot detection scheme to measure whitelight background, ground state Ra-man, transient absorption and transient Raman in shot-to-shot detection fashion. URLS has been applied to understand the excited state planarization dynamics of 1,4-bis(phenylethynyl)benzene (BPEB) in different solvents. In addition, excitation wavelength dependent conformational reorganization dynamics of different sub-sets of thermally activated ground state population of BPEB are also discussed. Using the same techniques along with femtosecond transient absorption, we demonstrate the ultrafast vibrational energy transfer and the role of coherent oscillations of low frequency vibrations on the solution phase photo-isomerization of trans-stilbene from an optically excited state. The effects of solvents on the coherent nuclear motion are also discussed in the context of reaction rates. 2

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Тези доповідей конференцій з теми "Ultrafast Raman Loss Spectroscopic Studies"

Yu, Soo-Chang, Xiaobing Xu, Robert Lingle, and J. B. Hopkins. "The Role of Vibrational Energy in the Ultrafast Photodissociation of Chromiumhexacarbonyl — A picosecond Raman Investigation." In International Conference on Ultrafast Phenomena. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/up.1990.md2.

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Photodissociation of Cr(CO)6 results in the loss of CO to form Cr(CO)5. In solution the pentacarbonyl species rapidly coordinates to the solvent and can therefore be used as a probe of solvent dynamics. Recent ultrafast studies of this simple reaction have resulted in controversy(1-6) regarding the dynamics of these various processes. We have used picosecond transient Raman spectroscopy to investigate the detailed dynamics of this reaction.

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Devlen, R. I., J. Kuhl, and K. Ploog. "Plasmon-Phonon Coupling and Hot Carrier Relaxation in GaAs and Low Temperature Grown GaAs." In International Conference on Ultrafast Phenomena. Washington, D.C.: Optica Publishing Group, 1992. http://dx.doi.org/10.1364/up.1992.mc24.

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Within the first picoseconds after photogeneration, hot carriers in bulk GaAs relax predominantly by emitting optical phonons. The emitted phonons exist as a non-thermal phonon population until they decay anharmonically. Previously, the dynamics of the nonthermal phonon population was studied using time resolved anti-Stokes Raman spectroscopy [1]. For a carrier density larger than 1017 cm−3 the plasma frequency is comparable to the phonon frequency and coupling of the two excitations becomes non-negligible. In GaAs plasmon-phonon coupled modes have been observed in both single component plasmas (via doping)[2] and two component plasmas (via optical excitation)[3]. Due to the interaction of the phonons with the carrier plasma there have been no measurements of the phonon population dynamics for carrier densities larger than about 1017 cm−3. However, these non-equilibrium phonons play an important role in theories of hot carrier relaxation at high densities. In particular the existence of a large non-thermal phonon population and its reabsorption by carriers has been used to explain a reduction in the carrier energy loss rate[4].

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