DOCSLIB.ORG

Characterization of Raman Spectroscopy System Transfer Functions in Intensity, Wavelength, and Time

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Characterization of Raman Spectroscopy System Transfer Functions in Intensity, Wavelength, and Time instruments Article Characterization of Raman Spectroscopy System Transfer Functions in Intensity, Wavelength, and Time Yu-Chung Lin and Joseph V. Sinfield * Lyles School of Civil Engineering, Purdue University, West Lafayette, IN 47907, USA; [email protected] * Correspondence: [email protected] Received: 30 June 2020; Accepted: 29 July 2020; Published: 5 August 2020 Abstract: The emergence of a wide variety of relatively low-cost compact spectrometers has led to an increase in the use of spectroscopic techniques by researchers in a broad array of fields beyond those that have traditionally employed these analytical methods. While the fundamental elements and functions of Raman systems are generally consistent, the specific components that compose a system may vary in number, design, and configuration, and researchers often modify off-the-shelf spectrometers for unique applications. Understanding the effect of instrument design and components on acquired information is thus crucial and provides the prospect to optimize the system to individual needs and to properly compare results obtained with different systems while also reducing the potential for unintended misinterpretation of data. This paper provides a practical treatment of the influences in a typical compact spectroscopy system that can impact the extent to which the output of the system is representative of the observed environment, a relationship that in measurement science is classically termed the system transfer function. For clarity, the transfer function is developed in terms of traditional Raman output parameters, namely intensity, wavelength, and time. Keywords: system; transfer function; Raman spectroscopy; intensity; wavelength; time 1. Introduction Raman spectroscopy is named after physicist C.V. Raman, who discovered the instantaneous inelastic light scattering phenomenon in 1928 [1]. The technique provides rich information to identify and characterize materials and has gained popularity because of both its simplicity and diverse range of applications. In this method, a monochromatic light source, usually a laser, is directed toward the target sample. Interaction between the incident photons and molecules of the sample scatter the incident light. While the majority of these scattered photons leave the sample at the same frequency at which they arrived (referred to as elastic or Rayleigh scattering), a small fraction of the photons may exchange energy with the molecules, leading to inelastic, or Raman scattering. In this latter case, individual incident photons may either lose energy (Stokes-shift; most common) or gain energy (anti-stokes-shift). For any given scattered photon, the amount of energy transferred is indicative of a vibrational and/or rotational energy state of the target molecule bonds and thus offers insight into the composition of the sample. To obtain this information, scattered photons are collected and guided to an instrument that separates spectral constituents. A light-sensitive detector is then used to assess the intensity of the scattered returns as a function of frequency to develop a Raman spectrum that reflects the molecular composition and structure of the sample. The rapid advance of Raman spectroscopy has been driven significantly by innovation in the underlying technologies that compose Raman systems. Developments in semiconductors have fostered the advent of compact, low-cost lasers across a wide range of operating frequencies. Advances in optics production, optical coatings, and fiber optics have enabled greater flexibility and customization in system designs. Developments in light detection and data acquisition have improved Raman Instruments 2020, 4, 22; doi:10.3390/instruments4030022 www.mdpi.com/journal/instruments Instruments 2020, 4, x 2 of 57 Advances in optics production, optical coatings, and fiber optics have enabled greater flexibility and Instruments 2020 4 customization, ,in 22 system designs. Developments in light detection and data acquisition 2have of 52 improved Raman system sensitivity and speed. Collectively, these advances have helped make the systemRaman sensitivityspectroscopic and speed.technique Collectively, more prevalent these advances in both have laboratory helped make and the Ramanfield settings, spectroscopic with techniqueparticularly more strong prevalent growth in in both the laboratory use of compac and fieldt Raman settings, spectroscopy with particularly systems strong and even growth portable in the useinstruments of compact for Ramanchemical spectroscopy analysis in applications systems and such even as portable food security instruments [2,3], art for examination chemical analysis [4–6], in applicationssitu mineral suchdetection as food [7], security explosive [2, 3detection], art examination [8], product [4–6 quality], in situ control mineral [9], detection forensic [ 7science], explosive [10], detectionand environmental [8], product monitoring quality control [11,12]. [9 ], forensic science [10], and environmental monitoring [11,12]. Due to thethe broadbroad arrayarray ofof applicationsapplications forfor whichwhich RamanRaman spectroscopyspectroscopy isis employed,employed, RamanRaman spectroscopic instruments may may encompass encompass a a variety variety of of context-specific context-specific components. components. It Itis isessential essential to toknow know how how each each of ofthese these components components contributes contributes to to variations variations in in the the properties properties of of the optical and electrical signals propagated inin the system and to evaluate and understand the possible output of the system beforebefore interpretinginterpreting results results derived derived from from its it use.s use. One One should should also also understand understand the the significance significance of theseof these possible possible variations variations before before comparing comparing the results the ofresults different of researchers.different researchers. With these perspectivesWith these inperspectives mind, this in paper mind, develops this paper the develops generalized the gene transferralized function transfer of afunction Raman of spectroscopic a Raman spectroscopic system for thesystem parameters for the ofparameters intensity, wavelength,of intensity, andwavele timength, and thenand appliestime and the then generalized applies formulationthe generalized to a specificformulation Raman to a spectroscopic specific Raman system spectroscopic as an example. system as an example. This paper first first introduces introduces several several general general components components in ina Raman a Raman system system and and provides provides an anoverview overview of how of howthe Raman the Raman phenomenon phenomenon is indu isced induced and observed and observed in a typical ina system. typical Transfer system. Transferfunctions functions for output for characterizing output characterizing quantitiesquantities of intensity, of wavelength, intensity, wavelength, and time are and then time developed are then developedby following by the following sequence the of sequencelight propagation of light propagationthrough a system, through from a system,the laser fromsource the to laser the sample, source toand the to sample,the detector and and to thedata detector acquisition and electronics. data acquisition For the electronics. intensity analysis, For the energy intensity losses analysis, when energylight propagates losses when through light different propagates components through in di thfferente system components are of greatest in the concern. system The are wavelength of greatest concern.analysis Thehighlights wavelength changes analysis in the highlights wavelengths changes managed in the wavelengths and/or observed managed as light and/or traverses observed the as lightsystem. traverses Lastly, thethe system. time delay Lastly, analysis the time draws delay attention analysis to draws group attention delay and to signal group spreading delay and which signal spreadingmay occur whichin fiber may optic occur and inelectronic fiber optic components, and electronic respectively. components, respectively. 2. The Components in a Raman System A Raman spectroscopy system requires a coherent optical source (usually a laser), a device to selectively examine bands of optical wavelengths composing the scattered return, and a detector to assess the scattering. In a typica typicall lab benchtop Raman spectroscopicspectroscopic system, there are also usually optics to collect, collect, direct, direct, and and focus focus the the light; light; to to elim eliminateinate unwanted unwanted frequencies; frequencies; or to or divert to divert part part of the of thelight light (for (forexample example as a trigger as a trigger for data for acquisition). data acquisition). There is There also usually is also usuallya sample a holder sample that holder contains that containsthe sample the of sample interest of (often interest a cuvette). (often a cuvette).In a portable In a Raman portable system, Raman the system, device the may device directly may focus directly on focusthe environment on the environment of interest of without interest a without container a containerto hold the to target. hold the No target. matter No what matter kind whatof Raman kind ofspectroscopic Raman spectroscopic system, all system, components all components along the along inbound the inboundand return and light return paths light as paths well as as well all asconnections all connections and conduits and conduits between
Load more

Recommended publications
  • DEVELOPMENT of a RAMAN SPECTROMETER to STUDY SURFACE-ENHANCED RAMAN SCATTERING by Nandita Biswas, Ridhima Chadha, Sudhir Kapoor, Sisir K
    BARC/2011/E/003 BARC/2011/E/003 DEVELOPMENT OF A RAMAN SPECTROMETER TO STUDY SURFACE-ENHANCED RAMAN SCATTERING by Nandita Biswas, Ridhima Chadha, Sudhir Kapoor, Sisir K. Sarkar and Tulsi Mukherjee Radiation & Photochemistry Division 2011 BARC/2011/E/003 GOVERNMENT OF INDIA ATOMIC ENERGY COMMISSION BARC/2011/E/003 DEVELOPMENT OF A RAMAN SPECTROMETER TO STUDY SURFACE-ENHANCED RAMAN SCATTERING by Nandita Biswas, Ridhima Chadha, Sudhir Kapoor, Sisir K. Sarkar and Tulsi Mukherjee Radiation & Photochemistry Division BHABHA ATOMIC RESEARCH CENTRE MUMBAI, INDIA 2011 BARC/2011/E/003 BIBLIOGRAPHIC DESCRIPTION SHEET FOR TECHNICAL REPORT (as per IS : 9400 - 1980) 01 Security classification : Unclassified 02 Distribution : External 03 Report status : New 04 Series : BARC External 05 Report type : Technical Report 06 Report No. : BARC/2011/E/003 07 Part No. or Volume No. : 08 Contract No. : 10 Title and subtitle : Development of a Raman spectrometer to study surface-enhanced Raman scattering 11 Collation : 31 p., 15 figs. 13 Project No. : 20 Personal author(s) : Nandita Biswas; Ridhima Chadha; Sudhir Kapoor; Sisir K. Sarkar; Tulsi Mukherjee 21 Affiliation of author(s) : Radiation and Photochemistry Division , Bhabha Atomic Research Centre, Mumbai 22 Corporate author(s) : Bhabha Atomic Research Centre, Mumbai - 400 085 23 Originating unit : Radiation and Photochemistry Division, BARC, Mumbai 24 Sponsor(s) Name : Department of Atomic Energy Type : Government Contd... BARC/2011/E/003 30 Date of submission : January 2011 31 Publication/Issue date : February 2011 40 Publisher/Distributor : Head, Scientific Information Resource Division, Bhabha Atomic Research Centre, Mumbai 42 Form of distribution : Hard copy 50 Language of text : English 51 Language of summary : English, Hindi 52 No.
    [Show full text]
  • Vacuum Ultra Violet Monochromator I Grating & OEM
    Feature Article JY Division nformation Vacuum Ultra Violet Monochromator I Grating & OEM Erick Jourdain Abstract Taking the advantage of Jobin Yvon(JY) leading position in the design and realisation of diffraction grating JY has developed over the last past 30 years some of the most innovative Vacuum Ultra Violet (VUV) monochromators for synchrotron centre. These monochromators, which combine the ultimate advanced diffraction grating technologies and some ultra precise under vacuum mechanics, have been installed in several synchrotron centres and have demonstrated superior performances. Today the development of new compact VUV sources and applications require compact VUV monochromators. Based on diffraction grating capabilities and our large experience acquired in the difficult and demanding market of under vacuum synchrotron monochromators JY is currently developing new compact monochromators for application such as Extreme UV lithography or X-ray Photoemission Spectroscopy. Introduction In the middle of the seventies thank to the development of the aberration corrected holographic toroidal gratings at Jobin Yvon (JY) we introduced on the market a new VUV monochromator concept that drastically enhanced the spectroscopic performances in this field [1]. During the eighties the Toroidal Grating Monochromator (TGM) and its associated toroidal gratings had a large and world wide success. At that time most of the synchrotron VUV beamline got equipped with this monochromator type and even today some recent beamline are still been developed Fig.
    [Show full text]
  • FT-IR Spectroscopy
    ORIEL ORIEL PRODUCT TRAINING FT-IR Spectroscopy SECTION FOUR FEATURES • Glossary of Terms • Introduction to FT-IR Spectroscopy Stratford, CT • Toll Free 800.714.5393 Fax 203.378.2457 • www.newport.com/oriel • [email protected] GLOSSARY OF TERMS Before we start the technical discussion on FT-IR Spectrometers, we devote a couple of pages to a Glossary, to facilitate the discussion that follows. 100% Line: Calculated by ratioing two background spectra Collimation: The ideal input beam is a cylinder of light. No taken under identical conditions. Ideally, the result is a flat beam of finite dimensions can be perfectly collimated; at best line at 100% transmittance. there is a diffraction limit. In practice the input beam is a Absorbance: Units used to measure the amount of IR cone that is determined by the source size or aperture used. radiation absorbed by a sample. Absorbance is commonly The degree of collimation can affect the S/N and the used as the Y axis units in IR spectra. Absorbance is defined resolution. by Beer’s Law, and is linearly proportional to concentration. Constructive Interference: A phenomenon that occurs when Aliasing: If frequencies above the Nyquist Frequency are not two waves occupy the same space and are in phase with filtered out, energy in these will appear as spectral artefacts each other. Since the amplitudes of waves are additive, the below the Nyquist Frequency. Optical and electronic anti two waves will add together to give a resultant wave which is aliasing can be used to prevent this. Sometimes the higher more intense than either of the individual waves.
    [Show full text]
  • The Term Fluorescence Was Coined by Stokes Circa 1850 to Name A
    Fluorescence primer v4.doc Page 1/11 19/11/2008 Fluorescence The term fluorescence was coined by Stokes circa 1850 to name a phenomenon resulting in the emission of light at longer wavelength than the absorbed light, and his name is still used to describe the wavelength shift (Figure 1A). Figure 1 The following general rules of fluorescence (see Jameson et al., 20031) are of practical importance: 1) In a pure substance existing in solution in a unique form, the fluorescence spectrum is invariant, remaining the same independent of the excitation wavelength. 2) The fluorescence spectrum lies at longer wavelengths than the absorbtion. 3) The fluorescence spectrum is, to a good approximation, a mirror image of the absorption band of least frequency These rules follow from quantum optical considerations depicted in the Perrin-Jablonski diagram (Figure 1B). Note that although the fluorophore may be excited into different singlet state energy levels (S1, S2, etc.) rapid thermal relaxation invariably brings the fluorophore to the lowest vibrational level of the first excited electronic state (S1) and emission occurs from that level. This fact explains the independence of the emission spectrum from the excitation wavelength. The fact that ground state fluorophores (at room temperature) are predominantly in the lowest vibrational level of the ground electronic state accounts for the Stokes shift. Finally, the fact that the spacings of the vibrational energy levels of S0 and S1 are usually similar accounts for the fact that the emission and the absorption spectra are approximately mirror images. The presence of appreciable Stokes shift is principally important for practical applications of fluorescence because it allows to separate (strong) excitation light from (weak) emitted fluorescence using appropriate optics.
    [Show full text]
  • Resonant Raman Spectroscopy of Nanotubes
    10.1098/rsta.2004.1444 Resonant Raman spectroscopy of nanotubes By Christian Thomsen1, Stephanie Reich2 and Janina Maultzsch1 1Technische Universit¨at Berlin, Hardenbergstraße 36, 10623 Berlin, Germany 2Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ, UK ([email protected]) Published online 28 September 2004 Single and double resonances in Raman scattering are introduced and six criteria for the observation and identification of double resonances stated. The experimental situation in carbon nanotubes is reviewed in view of these criteria. The evidence for the D mode and the high-energy mode is found to be overwhelming for a double- resonance process to take place, whereas the nature of the radial breathing-mode Raman process remains undecided at this point. Consequences for the application of Raman scattering to the characterization of nanotubes are discussed. Keywords: carbon nanotubes; double resonance; Raman scattering; defects 1. Introduction Raman scattering in carbon nanotubes has developed into a method of choice in the investigation of their physical properties and their characterization. The study of electronic resonances in the Raman spectra, a method which has been used exten- sively, for example, in work on semiconductors (Cardona 1982), gives us a wealth of information about the electronic band structure of a material. This is also true for the Raman work on carbon nanotubes, where resonance studies have moved into the focus of research. Traditional Raman studies of carbon nanotubes focus on the radial breathing mode (RBM), a mode where all atoms vibrate in phase in the radial direction (Dresselhaus et al. 1995). Its frequency, as can easily be shown (Jishi et al.
    [Show full text]
  • 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.
    [Show full text]
  • 1. What Is the Difference Between Slit and Monochromator? a Slit Is A
    1. What is the difference between slit and monochromator? A slit is a mechanical opening in a black painted metallic sheet, with a circular or triangular hole through which incident rays pass which lead to a monochromator. The slit permits passage of only a small fraction of incident radiation, which is selected for further processing such as wavelength selection and detection etc. Usually the output of the radiation is in the image of the slit. When the slit is wide relative to the wavelength, diffraction is difficult to observe. But when the wavelength and slit opening are of the same order of magnitude, diffraction is observed easily. Here the slit behaves as if it is a source of radiation. The output in this case occurs in a series of 1800 arcs. The plot of the frequency of the radiation as a function of peak transmittance is in the form of a Gaussian curve with maximum intensity being the midpoint of the frequency range. In contrast, monochromator may be defined as a device to select different wavelength of the original source radiation. Usually monochromators used in a UV-Visible/Fluorescence/AAS refer to the combination of slits, lenses, mirrors, windows, prisms and gratings. The output of monochromator is also a narrow band of continuous radiation. The band width is an inverse measure of the quality of the monochromator device. The band widths obtained from filters, prisms, gratings etc., become progressively narrower in each case. 2. Where is the monochromator being placed between source and sample or sample and detector in UV visible spectrophotometer? In a UV- Visible spectrophotometer, the monochromator is placed between the source of light and the sample.
    [Show full text]
  • Stokes Shift
    Stokes shift ticular molecular structure. If a material has a direct bandgap in the range of visible light, the light shining on it is absorbed, causing electrons to become excited to a higher energy state. The electrons remain in the ex- cited state for about 10−8 seconds. This number varies over several orders of magnitude depending on the sam- ple, and is known as the fluorescence lifetime of the sam- ple. After losing a small amount of energy in some way (hence the longer wavelength), the molecule returns to the ground state and energy is emitted. 2 References Absorption and emission spectra of Rhodamine 6G with ~25 nm [1] Gispert, J.R. (2008). Coordination Chemistry. Wiley- Stokes shift VCH. p. 483. ISBN 3-527-31802-X. [2] Albani, J.R. (2004). Structure and Dynamics of Macro- Not to be confused with Stark shift. molecules: Absorption and Fluorescence Studies. Elsevier. p. 58. ISBN 0-444-51449-X. Stokes shift is the difference (in wavelength or frequency [3] Lakowicz, J.R. 1983. Principles of Fluorescence Spec- units) between positions of the band maxima of the troscopy, Plenum Press, New York. ISBN 0-387-31278- absorption and emission spectra (fluorescence and Raman 1. being two examples) of the same electronic transition.[1] [4] Guilbault, G.G. 1990. Practical Fluorescence, Second It is named after Irish physicist George G. Stokes.[2][3][4] Edition, Marcel Dekker, Inc., New York. ISBN 0-8247- When a system (be it a molecule or atom) absorbs a 8350-6. photon, it gains energy and enters an excited state.
    [Show full text]
  • Fiber Amplifiers and Fiber Lasers Based on Stimulated Raman
    micromachines Review Fiber Amplifiers and Fiber Lasers Based on Stimulated Raman Scattering: A Review Luigi Sirleto * and Maria Antonietta Ferrara National Research Council (CNR), Institute of Applied Sciences and Intelligent Systems, Via Pietro Castellino 111, 80131 Naples, Italy; [email protected] * Correspondence: [email protected] Received: 10 January 2020; Accepted: 24 February 2020; Published: 26 February 2020 Abstract: Nowadays, in fiber optic communications the growing demand in terms of transmission capacity has been fulfilling the entire spectral band of the erbium-doped fiber amplifiers (EDFAs). This dramatic increase in bandwidth rules out the use of EDFAs, leaving fiber Raman amplifiers (FRAs) as the key devices for future amplification requirements. On the other hand, in the field of high-power fiber lasers, a very attractive option is provided by fiber Raman lasers (FRLs), due to their high output power, high efficiency and broad gain bandwidth, covering almost the entire near-infrared region. This paper reviews the challenges, achievements and perspectives of both fiber Raman amplifier and fiber Raman laser. They are enabling technologies for implementation of high-capacity optical communication systems and for the realization of high power fiber lasers, respectively. Keywords: stimulated raman scattering; fiber optics; amplifiers; lasers; optical communication systems 1. Introduction Optical communication systems require optoelectronic devices, such as sources, detectors and so on, and utilize fiber optics to transmit the light carrying the signals impressed by modulators. Optical fibers are affected by chromatic dispersion, losses, and nonlinearity. Dispersion control is, usually, achieved via fiber geometry and material composition. Losses limit the transmission distance in modern long haul fiber-optic communication systems, so in order to boost a weak signal, optical amplifiers have been developed.
    [Show full text]
  • Theoretical Investigation of Stokes Shifts and Reaction Pathways
    Theoretical Investigation of Stokes Shifts and Reaction Pathways by Laken M. Top - ARI IVS Associate of Arts, Science Option Yakima Valley Community College, 2007 Bachelor of Science, Chemistry and Mathematics RES University of Idaho, 2009 SUBMITTED TO THE DEPARTMENT OF CHEMISTRY IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN CHEMISTRY AT THE MASSACHUSETTS INSTITUTE OF TECHNOLOGY SEPTEMBER 2012 @ 2012 Massachusetts Institute of Technology. All rights reserved. 1 1-/ Signature of Author: Department of Chemistry July 12, 2012 Certified by: I Troy Van Voorhis ,1 Associate Professor of Chemistry Thesis Supervisor I / Certified by: f -y Jeffrey C. Grossman Associate Professor of Materials Science and Engineering Thesis Supervisor Accepted by: Robert W. Field Professor of Chemistry Chairman, Department Committee on Graduate Theses 1 Theoretical Investigation of Stokes Shifts and Reaction Pathways by Laken M. Top Submitted to the Department of Chemistry on July 12, 2012, in partial fulfillment of the requirements for the degree of Master of Science in Chemistry Abstract Solar thermal fuels and fluorescent solar concentrators provide two ways in which the energy from the sun can be harnessed and stored. While much progress has been made in recent years, there is still much more to learn about the way that these applications work and more efficient materials are needed to make this a feasible source of renewable energy. Theoretical chemistry is a powerful tool which can provide insight into the processes involved and the properties of materials, allowing us to predict substances that might improve the efficiency of these devices. In this work, we explore how the delta self-consistent field method performs for the calculation of Stokes shifts for conjugated dyes.
    [Show full text]
  • Article Intends to Provide a for the Necessary Virtual Electronic Brief Overview of the Differences and Transition
    ADVANCES IN RAMAN TECHNIQUES Laser requirements and advances for Raman techniques Andreas Isemann Laser Quantum GmbH, 78467 Konstanz, Germany INTRODUCTION 473 nm and 1064 nm, a narrow Raman scattering as a probe of bandwidth output of few tens of GHz vibrational transitions has made or below 1 MHz if needed within the leaps and bounds since its discovery, linewidth of vibrational transitions and various schemes based on this for high resolution, low noise (less phenomenon have been developed than 0.02%) and excellent beam with great success. quality (fundamental transversal Applications range from basic electromagnetic mode TEM00) scientific research, to medical and provides optimised performance industrial instrumentation. Some for the resolution of the Raman schemes utilise linear Raman measurement needed. scattering, whilst others take advantage The wavelength is chosen based of high peak-power fields to probe on the sample under investigation, nonlinear Raman responses. with 532 nm being commonly used This article intends to provide a for the necessary virtual electronic brief overview of the differences and transition. In the following section, benefits, together with the laser source four examples from different areas of requirements and the advancements Raman applications show the diverse in techniques enabled by recent applications of linear Raman and what developments in lasers. advances have been achieved. An example of studying a real-world LINEAR RAMAN application, the successful control of Figure 1 An example of the RR microfluidic device counting of The advent of the laser in providing a food quality using Raman spectroscopy photosynthetic microorganisms. As the cells of the model strain high-intensity coherent light source and multivariate analysis, is described Synechocystis sp.
    [Show full text]
  • 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.
    [Show full text]