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A Comparison of Ultraviolet and Visible Raman Spectra of Supported Metal Oxide Catalysts
8600 J. Phys. Chem. B 2001, 105, 8600-8606 A Comparison of Ultraviolet and Visible Raman Spectra of Supported Metal Oxide Catalysts Yek Tann Chua,† Peter C. Stair,*,† and Israel E. Wachs*,‡ Department of Chemistry, Center for Catalysis and Surface Science and Institute of EnVironmental Catalysis, Northwestern UniVersity, EVanston, Illinois 60208, and Zettlemoyer Center for Surface Studies and Department of Chemical Engineering, Lehigh UniVersity, Bethlehem, PennsylVania 18015 ReceiVed: April 11, 2001 The recent emergence of ultraviolet-wavelength-excited Raman spectroscopy as a tool for catalyst characterization has motivated the question of how UV Raman spectra compare to visible-wavelength-excited Raman spectra on the same catalyst system. Measurements of Raman spectra from five supported metal oxide systems (Al2O3-supported Cr2O3,V2O5, and MoO3 as well as TiO2-supported MoO3 and Re2O7), using visible (514.5 nm) and ultraviolet (244 nm) wavelength excitation have been compared to determine the similarities and differences in Raman spectra produced at the two wavelengths. The samples were in the form of self-supporting disks. Spectra from the oxides, both hydrated as a result of contact with ambient air and dehydrated as a result of calcination or laser-induced heating, were recorded. A combination of sample spinning and translation to produce a spiral pattern of laser beam exposure to the catalyst disk was found to be most effective in minimizing dehydration caused by laser-induced heating. Strong absorption by the samples in the ultraviolet significantly reduced the number of scatterers contributing to the Raman spectrum while producing only modest increases in the Raman scattering cross section due to resonance enhancement. -
Atomic and Molecular Laser-Induced Breakdown Spectroscopy of Selected Pharmaceuticals
Article Atomic and Molecular Laser-Induced Breakdown Spectroscopy of Selected Pharmaceuticals Pravin Kumar Tiwari 1,2, Nilesh Kumar Rai 3, Rohit Kumar 3, Christian G. Parigger 4 and Awadhesh Kumar Rai 2,* 1 Institute for Plasma Research, Gandhinagar, Gujarat-382428, India 2 Laser Spectroscopy Research Laboratory, Department of Physics, University of Allahabad, Prayagraj-211002, India 3 CMP Degree College, Department of Physics, University of Allahabad, Pragyagraj-211002, India 4 Physics and Astronomy Department, University of Tennessee, University of Tennessee Space Institute, Center for Laser Applications, 411 B.H. Goethert Parkway, Tullahoma, TN 37388-9700, USA * Correspondence: [email protected]; Tel.: +91-532-2460993 Received: 10 June 2019; Accepted: 10 July 2019; Published: 19 July 2019 Abstract: Laser-induced breakdown spectroscopy (LIBS) of pharmaceutical drugs that contain paracetamol was investigated in air and argon atmospheres. The characteristic neutral and ionic spectral lines of various elements and molecular signatures of CN violet and C2 Swan band systems were observed. The relative hardness of all drug samples was measured as well. Principal component analysis, a multivariate method, was applied in the data analysis for demarcation purposes of the drug samples. The CN violet and C2 Swan spectral radiances were investigated for evaluation of a possible correlation of the chemical and molecular structures of the pharmaceuticals. Complementary Raman and Fourier-transform-infrared spectroscopies were used to record the molecular spectra of the drug samples. The application of the above techniques for drug screening are important for the identification and mitigation of drugs that contain additives that may cause adverse side-effects. Keywords: paracetamol; laser-induced breakdown spectroscopy; cyanide; carbon swan bands; principal component analysis; Raman spectroscopy; Fourier-transform-infrared spectroscopy 1. -
Laser Raman Spectroscopy As a Technique for Identification Of
ARTICLE IN PRESS CHEMGE-15589; No of Pages 13 Chemical Geology xxx (2008) xxx–xxx Contents lists available at ScienceDirect Chemical Geology journal homepage: www.elsevier.com/locate/chemgeo Laser Raman spectroscopy as a technique for identification of seafloor hydrothermal and cold seep minerals Sheri N. White ⁎ Department of Applied Ocean Physics and Engineering, Woods Hole Oceanographic Institution, Woods Hole, MA 02536, USA article info abstract Article history: In situ sensors capable of real-time measurements and analyses in the deep ocean are necessary to fulfill the Received 8 August 2008 potential created by the development of autonomous, deep-sea platforms such as autonomous and remotely Received in revised form 8 November 2008 operated vehicles, and cabled observatories. Laser Raman spectroscopy (a type of vibrational spectroscopy) is an Accepted 10 November 2008 optical technique that is capable of in situ molecular identification of minerals in the deep ocean. The goals of this Available online xxxx work are to determine the characteristic spectral bands and relative Raman scattering strength of hydrothermally- Editor: R.L. Rudnick and cold seep-relevant minerals, and to determine how the quality of the spectra are affected by changes in excitation wavelength and sampling optics. The information learned from this work will lead to the development Keywords: of new, smaller sea-going Raman instruments that are optimized to analyze minerals in the deep ocean. Raman spectroscopy Many minerals of interest at seafloor hydrothermal and cold seep sites are Raman active, such as elemental sulfur, Mineralogy carbonates, sulfates and sulfides. Elemental S8 sulfur is a strong Raman scatterer with dominant bands at ∼219 and Hydrothermal vents 472 Δcm−1. -
Accessing Excited State Molecular Vibrations by Femtosecond Stimulated Raman Spectroscopy
Accessing Excited State Molecular Vibrations by Femtosecond Stimulated Raman Spectroscopy Giovanni Batignani,y Carino Ferrante,y,z and Tullio Scopigno∗,y,z yDipartimento di Fisica, Universitá di Roma “La Sapienza", Roma, I-00185, Italy z Istituto Italiano di Tecnologia, Center for Life Nano Science @Sapienza, Roma, I-00161, Italy E-mail: [email protected] arXiv:2010.05029v1 [physics.optics] 10 Oct 2020 1 Abstract Excited-state vibrations are crucial for determining photophysical and photochem- ical properties of molecular compounds. Stimulated Raman scattering can coherently stimulate and probe molecular vibrations with optical pulses, but it is generally re- stricted to ground state properties. Working in resonance conditions, indeed, enables cross-section enhancement and selective excitation to a targeted electronic level, but is hampered by an increased signal complexity due to the presence of overlapping spectral contributions. Here, we show how detailed information on ground and excited state vi- brations can be disentangled, by exploiting the relative time delay between Raman and probe pulses to control the excited state population, combined with a diagrammatic formalism to dissect the pathways concurring to the signal generation. The proposed method is then exploited to elucidate the vibrational properties of ground and excited electronic states in the paradigmatic case of Cresyl Violet. We anticipate that the presented approach holds the potential for selective mapping the reaction coordinates pertaining to transient electronic stages implied in photo-active compounds. Graphical TOC Entry 2 Raman spectroscopy is a powerful tool to access the vibrational fingerprints of molecules or solid state compounds and it can be used to extract structural and dynamical information of the samples under investigation. -
Combining Chemical Information from Grass Pollen in Multimodal Characterization
ORIGINAL RESEARCH published: 31 January 2020 doi: 10.3389/fpls.2019.01788 Combining Chemical Information From Grass Pollen in Multimodal Characterization Sabrina Diehn 1,2, Boris Zimmermann 3, Valeria Tafintseva 3, Stephan Seifert 1,2, Murat Bag˘ cıog˘ lu 3, Mikael Ohlson 4, Steffen Weidner 2, Siri Fjellheim 5, Achim Kohler 3,6 and Janina Kneipp 1,2* 1 Department of Chemistry, Humboldt-Universität zu Berlin, Berlin, Germany, 2 BAM Federal Institute for Materials Research and Testing, Berlin, Germany, 3 Faculty of Science and Technology, Norwegian University of Life Sciences, Ås, Norway, 4 Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, Ås, Norway, 5 Faculty of Biosciences, Norwegian University of Life Sciences, Ås, Norway, 6 Nofima AS, Ås, Norway Edited by: Lisbeth Garbrecht Thygesen, fi University of Copenhagen, The analysis of pollen chemical composition is important to many elds, including Denmark agriculture, plant physiology, ecology, allergology, and climate studies. Here, the Reviewed by: potential of a combination of different spectroscopic and spectrometric methods Wesley Toby Fraser, regarding the characterization of small biochemical differences between pollen samples Oxford Brookes University, United Kingdom was evaluated using multivariate statistical approaches. Pollen samples, collected from Åsmund Rinnan, three populations of the grass Poa alpina, were analyzed using Fourier-transform infrared University of Copenhagen, Denmark (FTIR) spectroscopy, Raman spectroscopy, surface enhanced Raman scattering (SERS), Anna De Juan, and matrix assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS). The University of Barcelona, Spain variation in the sample set can be described in a hierarchical framework comprising three *Correspondence: populations of the same grass species and four different growth conditions of the parent Janina Kneipp [email protected] plants for each of the populations. -
Raman Scattering and Fluorescence
Fluorescence 01 Raman Scattering and Fluorescence Introduction The existence of such virtual states also explains why the non-resonance Raman effect Raman scattering and Fluorescence emission does not depend on the wavelength of the are two competing phenomena, which have excitation, since no real states are involved in similar origins. Generally, a laser photon this interaction mechanism. In fact, the Raman bounces off a molecule and looses a certain spectrum generally does not depend on the amount of energy that allows the molecule to laser excitation. vibrate (Stokes process). The scattered photon is therefore less energetic and the associated However, when the energy of the excitation light exhibits a frequency shift. The various photon gets close to the transition energy frequency shifts associated with different between two electronic states, one then deals molecular vibrations give rise to a spectrum, with resonance Raman or resonance that is characteristic of a specific compound. fluorescence (fig.1, case (d)). The basic difference between these two processes is In contrast, fluorescence or luminescence related to the time scales involved, as well as emission follows an absorption process. For a with the nature of the so-called intermediate better understanding, one can refer to the states. In contrast with resonant fluorescent, diagram below. relaxed fluorescence results from the emission of a photon from the lowest vibrational level of an excited electronic state, following a direct absorption of the photon and relaxation of the molecule from its vibrationally excited level of the electronic state back to the lowest vibrational level of the electronic state. A fluorescence process typically requires more than 10-9 s. -
Venus Elemental and Mineralogical Camera (Vemcam)
EPSC Abstracts Vol. 13, EPSC-DPS2019-827-1, 2019 EPSC-DPS Joint Meeting 2019 c Author(s) 2019. CC Attribution 4.0 license. Venus Elemental and Mineralogical Camera (VEMCam) Samuel M. Clegg (1), Brett S. Okhuysen (1), David S. DeCroix (1), Raymond T. Newell (1), Roger C. Wiens (1), Shiv K. Sharma (2), Sylvestre Maurice (3), Ronald K. Martinez (1), Adriana Reyes-Newell (1), and Melinda D. Dyar (4), (1) Los Alamos National Laboratory, Los Alamos, NM, [email protected], (2) Hawaii Inst. of Geophysics and Planetology, Univ. of Hawaii, Honolulu, USA, (3) L'Institut de Recherche en Astrophysique et Planétologie, Toulouse France, (4) Planetary Science Inst., Tucson, AZ, USA Abstract The Venus Elemental and Mineralogical Camera The Venus Elemental and Mineralogical Camera (VEMCam) is an integrated remote LIBS and Raman (VEMCam) can make thousands of measurements instrument concept designed to operate from within within the first two hours on the surface, providing the safety of the lander. The extreme Venus surface an unprecedented description of the Venus surface. conditions requires rapid analyses and VEMCam can VEMCam is based on the ChemCam instrument on collect over 1000 chemical and mineralogical spectra the Mars Science Laboratory rover and the within the first hour. Here, we discuss the VEMCam SuperCam instrument selected for the Mars 2020 prototype calibration and analysis in which samples rover. VEMCam includes an integrated Raman and are placed in a 2 m long chamber capable of Laser-Induced Breakdown Spectroscopy (LIBS) simulating the Venus surface atmosphere. instrument capable of probing many disparate locations around the lander. VEMCam also includes 1. -
Crystal Structure, Raman Spectroscopy and Dielectric Properties of New Semiorganic Crystals Based on 2-Methylbenzimidazole
crystals Article Crystal Structure, Raman Spectroscopy and Dielectric Properties of New Semiorganic Crystals Based on 2-Methylbenzimidazole E. V. Balashova 1,* , F. B. Svinarev 1, A. A. Zolotarev 2, A. A. Levin 1, P. N. Brunkov 1, V. Yu. Davydov 1 , A. N. Smirnov 1 , A. V. Redkov 3, G. A. Pankova 4 and B. B. Krichevtsov 1 1 Ioffe Institute, 26 Politekhnicheskaya, St Petersburg 194021, Russian Federation; [email protected]ffe.ru (F.B.S.); [email protected]ffe.ru (A.A.L.); [email protected]ffe.ru (P.N.B.); [email protected]ffe.ru (V.Y.D.); [email protected]ffe.ru (A.N.S.); [email protected]ffe.ru (B.B.K.) 2 Institute of Earth Sciences, Saint-Petersburg State University, 7/9 Universitetskaya Nab., St Petersburg 199034, Russian Federation; [email protected] 3 Institute of Problems of Mechanical Engineering, 61 Bolshoy pr. V.O., St Petersburg 199004, Russian Federation; [email protected] 4 Institute of macromolecular compounds, 31 Bolshoy pr. V.O., St Petersburg 199004, Russian Federation; [email protected] * Correspondence: [email protected]ffe.ru Received: 27 September 2019; Accepted: 29 October 2019; Published: 31 October 2019 Abstract: New single crystals, based on 2-methylbenzimidazole (MBI), of MBI-phosphite (C16H24N4O7P2), MBI-phosphate-1 (C16H24N4O9P2), and MBI-phosphate-2 (C8H16N2O9P2) were obtained by slow evaporation method from a mixture of alcohol solution of MBI crystals and water solution of phosphorous or phosphoric acids. Crystal structures and chemical compositions were determined by single crystal X-ray diffraction (XRD) analysis and confirmed by XRD of powders and elemental analysis. -
High Performance Raman Spectroscopy with Simple Optical Components ͒ ͒ W
High performance Raman spectroscopy with simple optical components ͒ ͒ W. R. C. Somerville, E. C. Le Ru,a P. T. Northcote, and P. G. Etchegoinb The MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, P.O. Box 600, Wellington, New Zealand ͑Received 6 December 2009; accepted 19 April 2010͒ Several simple experimental setups for the observation of Raman scattering in liquids and gases are described. Typically these setups do not involve more than a small ͑portable͒ CCD-based spectrometer ͑without scanning͒, two lenses, and a portable laser. A few extensions include an inexpensive beam-splitter and a color filter. We avoid the use of notch filters in all of the setups. These systems represent some of the simplest but state-of-the-art Raman spectrometers for teaching/ demonstration purposes and produce high quality data in a variety of situations; some of them traditionally considered challenging ͑for example, the simultaneous detection of Stokes/anti-Stokes spectra or Raman scattering from gases͒. We show examples of data obtained with these setups and highlight their value for understanding Raman spectroscopy. We also provide an intuitive and nonmathematical introduction to Raman spectroscopy to motivate the experimental findings. © 2010 American Association of Physics Teachers. ͓DOI: 10.1119/1.3427413͔ I. INTRODUCTION and finish with a higher energy than the original one. This case corresponds to anti-Stokes Raman scattering. The Raman effect was discovered in 1928 by Raman1 and In reality, the photon is usually provided by a laser, which is now a major research tool with applications in physics, has a well defined frequency. -
Ultraviolet Raman Spectrometry Handbook of Vibrational
Ultraviolet Raman Spectrometry Sanford A. Asher Reproduced from: Handbook of Vibrational Spectroscopy John M. Chalmers and Peter R. Griffiths (Editors) John Wiley & Sons Ltd, Chichester, 2002 Ultraviolet Raman Spectrometry Sanford A. Asher University of Pittsburgh, Pittsburgh, PA, USA 1 INTRODUCTION mid-infrared absorption measurements. Raman excitation used Hg arc emission lines and photographic detection. The Raman spectroscopy measures the magnitudes and intensi- use of the Hg arc allowed the first ultraviolet (UV) Raman ties of frequency shifts that occur because of the inelastic measurements, some of which were actually resonance scattering of light from matter.1–4 The observed shifts Raman measurements within the absorption bands of can be used to extract information on molecular structure analyte molecules. and dynamics. In addition, important information can be After 1945 the advent of relatively convenient IR instru- obtained by measuring the change in the electric field ori- mentation decreased enthusiasm for Raman spectroscopy, entation of the scattered light relative to that of the incident and it became a specialized field. Much of the work before exciting light. 1960 centered on examining molecular structure and molec- The experiment is usually performed by illuminating a ular vibration dynamics. Major advances occurred during sample with a high-intensity light beam with a well-defined this period in the theoretical understanding of Raman spec- frequency and a single linear polarization (Figure 1); the troscopy and in the resonance Raman phenomenon, where scattered light is collected over some solid angle and mea- excitation occurs within an electronic absorption band. sured to determine frequency, intensity, and polarization. The first commercial Raman instrument became available The inelastic scattering Raman phenomenon, which leads in 1953. -
Angwcheminted, 2000, 39, 2587-2631.Pdf
REVIEWS Femtochemistry: Atomic-Scale Dynamics of the Chemical Bond Using Ultrafast Lasers (Nobel Lecture)** Ahmed H. Zewail* Over many millennia, humankind has biological changes. For molecular dy- condensed phases, as well as in bio- thought to explore phenomena on an namics, achieving this atomic-scale res- logical systems such as proteins and ever shorter time scale. In this race olution using ultrafast lasers as strobes DNA structures. It also offers new against time, femtosecond resolution is a triumph, just as X-ray and electron possibilities for the control of reactivity (1fs 10À15 s) is the ultimate achieve- diffraction, and, more recently, STM and for structural femtochemistry and ment for studies of the fundamental and NMR spectroscopy, provided that femtobiology. This anthology gives an dynamics of the chemical bond. Ob- resolution for static molecular struc- overview of the development of the servation of the very act that brings tures. On the femtosecond time scale, field from a personal perspective, en- about chemistryÐthe making and matter wave packets (particle-type) compassing our research at Caltech breaking of bonds on their actual time can be created and their coherent and focusing on the evolution of tech- and length scalesÐis the wellspring of evolution as a single-molecule trajec- niques, concepts, and new discoveries. the field of femtochemistry, which is tory can be observed. The field began the study of molecular motions in the with simple systems of a few atoms and Keywords: femtobiology ´ femto- hitherto unobserved ephemeral transi- has reached the realm of the very chemistry ´ Nobel lecture ´ physical tion states of physical, chemical, and complex in isolated, mesoscopic, and chemistry ´ transition states 1. -
22 DE88 014566 Introduction
Influence of stimulated Raman scattering on the CONF-880435 — 22 conversion efficiency in four wave mixing DE88 014566 Rainer Wunderlich Max-Planck-Institut fur Kernphysik D6900 Heidelberg l.FRG M. A. Moore, W. R. Garrett and M. G. Payne Chemical Physics Section, Oak Ridge National Laboratory Oak Ridge ,TN 37831 USA Abstract: Secondary nonlinear optical effects following parametric four wave mixing in •odium vapor are investigated. The generated ultraviolet radiation induces stimulated Raman scattering and other four wave mixing process. Population transfer due to Raman transitions strongly influences the phase matching conditions for the primary mixing process. Pulse shortening and a reduction in conversion efficiency are observed. Introduction Tunable light sources in the ultraviolet (UV) and vacuum ultraviolet (VUV) region of the optical spectrum are important tools for the resonant excitation and ionisation of atoms and moleculs whose lowest excited states have energies above 6eV. Below 200nm tunable VUV light is most often produced by four wave mixing (FWM) in phase matched ga» mixtures. The tuning range has been extended belcw lQOnm (Hilber et. al 1987) using Kr as nonlinear medium. The efficiency of UV generation is increased by choosing an active medium with resonance enhancement of the third order nonlinear susceptibilty ,x (wc/v)> at the particular wavelength. Here we are concerned with loss processes of the generated UV due to further nonlinear processes like stimulated electronic Raman scattering and four wave mixing processes initiated by the UV which do not directly involve the generation of the UV itself. Processes which directly limit UV generation depend on the resonance structure of x*3* [uuv) • In case of a two photon resonance pump depletion due to two photon absorption and ionisation, bleaching of x^3' («i/v") due to population transfer (Heinrich et al 1983) and population transfer induced index changes (Puell et al 1980) limit the UV generation.