Chemistry
Spectroscopy
Spectroscopy is the study of the interaction between matter and electromagnetic radiation. It involves analyzing the way in which different substances absorb or emit light at various wavelengths. By examining these interactions, spectroscopy can provide valuable information about the composition, structure, and properties of substances, making it a powerful tool in chemical analysis and research.
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12 Key excerpts on "Spectroscopy"
eBook - PDF- Khetarpaul, Neelam(Authors)
- 2021(Publication Date)
- Daya Publishing House(Publisher)
Chapter 8 Spectroscopy Spectroscopy was originally the study of the interaction between radiation and matter as a function of wavelength (λ). In fact, historically, Spectroscopy referred to the use of visible light dispersed according to its wavelength, e.g. by a prism. Later the concept was expanded greatly to comprise any measurement of a quantity as a function of either wavelength or frequency. Spectroscopy is the study of light as it breaks into its constituent colors. This is because light is a wave, and different energies have different wavelengths. These different wavelengths correlate to different colors. By examining these different colors, one can determine any number of properties of the object being studied, as the colors of the light reflect the energy states. In other words, spectrophotometry is the study of the reflection or transmission properties of a substance as a function of wavelength. It is the quantitative study of electromagnetic spectra of a material. More technically, Spectroscopy looks at the interaction between any matter and radiation. During the process, the transmittance or reflectance of the substance is measured through the careful geometrical and spectral consideration. Spectrometry is the spectroscopic technique used to assess the concentration or amount of a given chemical (atomic, molecular, or ionic) species. In this case, the instrument that performs such measurements is a spectrometer, spectrophotometer, or spectrograph. The data that is obtained from Spectroscopy is called a spectrum. A spectrum is a plot of the intensity of energy detected versus the wavelength (or mass or momentum or frequency, etc.) of the energy. A spectrum can be used to obtain information about atomic and molecular energy levels, molecular geometries, chemical bonds, interactions of molecules, and related processes. Often, spectra are used to identify the components of a sample (qualitative analysis).
eBook - PDFEngineering Chemistry
Fundamentals and Applications
- Shikha Agarwal(Author)
- 2019(Publication Date)
- Cambridge University Press(Publisher)
17.1 Introduction Spectroscopy is the branch of science which deals with the study of the interaction of electromagnetic radiation with matter. It is the most powerful tool available for the study of structures of atoms and molecules. There are several spectroscopic techniques that help in investigating various aspects of atomic and molecular structure. In this chapter, we will discuss the common spectroscopic techniques like electronic Spectroscopy (which includes UV–visible), infrared Spectroscopy (IR), rotational, microwave, nuclear magnetic resonance (NMR) and Raman Spectroscopy. The chapter deals with the principles, experimental techniques and applications of the various spectroscopic methods. However, before starting it is essential to discuss some basic fundamentals of Spectroscopy. 17.2 Basic Terms and Principles of Spectroscopy Electromagnetic radiations Electromagnetic radiation is a form of radiant energy which has both particle as well as wave nature. In vacuum, it normally travels in a straight line with the speed of light (3 ×10 8 m/s). It has both electric and magnetic field components, which are coplanar and oscillate perpendicular to each other and perpendicular to the direction of wave propagation (Fig. 17.1). Figure 17.1 Planes of electromagnetic waves Spectroscopy Chapter 17 Spectroscopy 969 Properties of electromagnetic radiations The properties of electromagnetic radiation can be described easily by ascribing wave nature to these radiations. (a) Wavelength It is denoted by l (lambda) and is defined as the distance between two adjacent crests (C–C) or troughs (T–T) in a particular wave (Fig. 17.2). It can be expressed in centimeters. The other units for expressing wavelength are given below.
- Prakash Singh Bisen, Anjana Sharma(Authors)
- 2012(Publication Date)
- CRC Press(Publisher)
115 5 Spectroscopy 5.1 INTRODUCTION 5.1.1 D EFINITION AND G ENERAL P RINCIPLES As a useful working definition, Spectroscopy can be defined as the interaction of electromagnetic radiation (EM) with matter, although this does not include mass Spectroscopy. Several factors have led to the branching of Spectroscopy in different directions. Most significant is the order of mag-nitude of the energies involved, but additional factors such as the presence of a magnetic field and instrumentation considerations have led to the techniques of ultraviolet (UV), infrared (IR), nuclear magnetic resonance (NMR), and electron spin resonance (ESR) Spectroscopy. Breakup and analysis of the above definition will be useful before delving into the details of the different spectroscopic techniques mentioned. The definition includes 1. Electromagnetic radiation 2. Interaction of EM with matter 3. Matter EM radiation consists of an electric field perpendicular to a magnetic field and both at right angles to the direction of propagation of light (Figure 5.1). A fundamental property of EM radiation is that it can behave as though it exists as discrete quanta or packets of energy: E h = υ where E = energy h = Planck’s constant = 6.63 × 10 − 34 J·s υ = frequency of radiation in Hertz There are two ways in which EM radiation interacts with matter: absorption and emission. Absorption occurs when incident radiation increases the energy of a system. An increase in energy is manifested as a decrease in intensity of emergent radiation. Emission occurs when there is a decrease in the energy of a system. Decrease in energy may be due to 1. Thermal energy loss: Energy loss by molecular or submolecular motion like a collision, vibration, or rotation. 2. EM emission: This results in phosphorescence and fluorescence. 3. Photochemical reactions: There is a competition between the three processes, also called relaxation processes.
- Bhim Prasad Kaflé(Author)
- 2019(Publication Date)
- Elsevier(Publisher)
Chapter 1Spectrophotometry and its application in chemical analysis
Abstract
In this chapter, we will learn the types of spectrophotometric techniques and their application for qualitative and quantitative determination of an analyte in a given sample. As a spectroscopic technique concerns with the interaction of light with matter, we will also discuss the properties of light and processes (phenomena) that occur after interaction with matter.Keywords
Electromagnetic radiation; Absorption; Reflection and transmittance; Analyte1.1. Spectroscopy and applications (overview)
Spectroscopy is a branch of science (analytical chemistry) which deals with the study of the interaction of electromagnetic radiation with matter. In fact, traditionally, the interactions of analyte were between matter and electromagnetic radiation, but now Spectroscopy has been broadened to include interactions between matter and other forms of energy. Such examples include beams of particles such as ions and electrons. These kinds of analytical methods that are considered to be one of the most powerful tools available for the study of materials’ fundamental properties (e.g., atomic and molecular structure, optical properties) and also used in quantifying the wide range of chemical species prevailing in a given sample. In this method, an analyst carries out measurements of light (or light-induced charged particles) that is absorbed, emitted, reflected or scattered by an analyte chemical or a material. Then these measured data are correlated to identify and quantify the chemical species present in that analyte. Ideally, a spectrometer makes measurements either by scanning a spectrum (point by point) or by simultaneous monitoring several positions in a spectrum; the quantity that is measured is a function of radiant power.Specifically, over all the other analytical methods, the spectroscopic techniques possess the following advantages:- 1. These techniques are less time consuming and much more rapid.
eBook - PDF- Douglas Skoog, Donald West, F. Holler, Stanley Crouch, Douglas Skoog(Authors)
- 2021(Publication Date)
- Cengage Learning EMEA(Publisher)
M easurements based on light and other forms of electromagnetic radiation are widely used throughout analytical chemistry. The interactions of radiation and matter are the subject of the science called Spectroscopy. Spectroscopic analytical methods are based on measuring the amount of radiation produced or absorbed by molecular or atomic species of interest. 1 We can classify spectroscopic methods according to the region of the electromagnetic spectrum used or produced in the measurement. The g-ray, X-ray, ultraviolet (UV), visible, infrared (IR), microwave, and radio-frequency (RF) regions have been used. Indeed, current usage extends the meaning of Spectroscopy yet further to include techniques such as acoustic, mass, and electron Spectroscopy in which electromagnetic radiation is not a part of the measurement. Spectroscopy has played a vital role in the development of modern atomic theory. In ad- dition, spectrochemical methods have provided perhaps the most widely used tools for the elucidation of molecular structure as well as the quantitative and qualitative determination of both inorganic and organic compounds. This chapter describes the basic principles that are necessary to understand measurements made with electromagnetic radiation, particularly those dealing with the absorption of UV, visible, and IR radiation. The nature of electromagnetic radiation and its interactions with matter are stressed. The next five chapters are devoted to spectroscopic instruments (Chapter 23), molecular absorption Spectroscopy (Chapter 24), molecular fluorescence Spectroscopy (Chapter 25), atomic Spectroscopy (Chapter 26), and mass spectrometry (Chapter 27). Introduction to Spectrochemical Methods CHAPTER 22 1 For further study, see D. A. Skoog, F. J. Holler, and S. R. Crouch, Principles of Instrumental Analysis, 7th ed., Sections 2–3, Boston, MA: Cengage Learning, 2018; F.
eBook - ePub- John Kenkel(Author)
- 2013(Publication Date)
- CRC Press(Publisher)
7 Introduction to Spectrochemical Methods7.1 Introduction
Many instrumental methods of analysis involve the refraction, absorption, or emission of light. These can be referred to as spectrochemical methods . The science that deals with the refraction of light is called refractometry and the instrument used is called the refractometer . The science that deals with the absorption and emission of light is called Spectroscopy or spectrometry . The broad term for the instruments used is spectrometer , whereas a slightly more specific term (when a light sensor known as a phototube is used) is spectrophotometer . In spectrochemical analysis procedures, the degree to which light is refracted or absorbed, or the intensity of light that is emitted, is related to the amount of an analyte present in the sample tested. Thus, the degree of light refraction, absorption, and the intensity of light emission are the critical measurements. The electrical signal readout referred to in Figure 6.2 is an electrical signal that is related to the degree of light refraction, absorption or the intensity of light emission. The instrument readings mentioned in Figure 6.3 are the readings generated by the instrument as a result of this refraction, absorption, or emission (see Figure 7.1 ).In this chapter, we expand the above brief summary so that all aspects of refractometry and Spectroscopy as analytical methods can be clearly understood and practiced. This will mean providing a full discussion of the nature and parameters of light, including energy, wavelength, frequency, and wavenumber. We will address exactly what is meant by light refraction, absorption, and emission. The discussion includes the spectral differences between atoms (atomic Spectroscopy ) and molecules (molecular Spectroscopy
eBook - ePub- Thomas J. Bruno, James W. Robinson, George M. Frame II, Eileen M. Skelly Frame(Authors)
- 2023(Publication Date)
- CRC Press(Publisher)
CHAPTER 3 Introduction to SpectroscopyDOI: 10.1201/9781003188544-33.1 INTERACTION BETWEEN ELECTROMAGNETIC RADIATION AND MATTER
We know from our observation of rainbows that visible light (white light) is composed of a continuum of colors from violet to red. If a beam of white light is passed through a beaker of water, it remains white. If potassium permanganate is added to the water, the white light appears purple after it passes through the solution. The permanganate solution allows the red and blue components of white light to pass through but absorbs the other colors from the original beam of light. This is one example of the interaction of electromagnetic radiation, or light, with matter. In this case, the electromagnetic radiation is visible light and we can see the effect of absorption of some of the light with our eyes. However, interactions between electromagnetic radiation and matter take place in many ways and over a wide range of radiant energies. Most of these interactions are not visible to the human eye but can be measured with suitable instruments.The interaction of electromagnetic radiation and matter is not haphazard but follows well-documented rules with respect to the wavelengths of light absorbed or emitted and the extent of absorption or emission. The subject of Spectroscopy is the study of the interaction of electromagnetic radiation and matter.3.1.1 What Is Electromagnetic Radiation?
The nature of electromagnetic radiation baffled scientists for many years. At times, light appears to behave like a wave; at other times, it behaves as though it were composed of small particles. While we now understand the “wave–particle duality” of all matter, including electromagnetic radiation, in terms of quantum mechanics, it is still convenient to consider electromagnetic radiation as having the properties of waves in many cases.Light waves can be represented as oscillating perpendicular electric and magnetic fields. The fields are at right angles to each other and to the direction of propagation of the light. The oscillations are sinusoidal in shape, as shown in Figure 3.1 . We can easily and accurately measure the wavelength λ defined as the crest-to-crest distance between two successive maxima. The standard unit of wavelength is the SI unit of length, the meter (m), but smaller units such as centimeter (cm), micrometer (μm), and nanometer (nm) are commonly used. The amplitude of the wave is defined as the maximum of the vector from the origin to a point displacement of the oscillation. An example of the electric field portion of a light wave propagating along only one axis is shown in Figure 3.1 . Such a wave, confined to one plane, is called plane-polarized light. The wave shown represents only a single wavelength, λ. Light of only one wavelength is called monochromatic light. Light that consists of more than one wavelength is called polychromatic
eBook - ePubInstrumental Analytical Chemistry
An Introduction
- James W. Robinson, Eileen M. Skelly Frame, George M. Frame II(Authors)
- 2021(Publication Date)
- CRC Press(Publisher)
Introduction to Spectroscopy 2DOI: 10.1201/b21879-22.1 The Interaction Between Electromagnetic Radiation and Matter
We know from our observation of rainbows that visible light (white light) is composed of a continuum of colors from violet to red. If a beam of white light is passed through a beaker of water, it remains white. If potassium permanganate is added to the water, the white light appears purple after it passes through the solution. The permanganate solution allows the red and blue components of white light to pass through but absorbs the other colors from the original beam of light. This is one example of the interaction of electromagnetic radiation, or light, with matter. In this case, the electromagnetic radiation is visible light and we can see the effect of absorption of some of the light with our eyes. However, interactions between electromagnetic radiation and matter take place in many ways and over a wide range of radiant energies. Most of these interactions are not visible to the human eye, but can be measured with suitable instruments.Interaction of electromagnetic radiation and matter is not haphazard, but follows well-documented rules with respect to the wavelengths of light absorbed or emitted and the extent of absorption or emission. The subject of Spectroscopy is the study of the interaction of electromagnetic radiation and matter.2.1.1 What is Electromagnetic Radiation?
The nature of electromagnetic radiation baffled scientists for many years. At times, light appears to behave like a wave; at other times, it behaves as though it were composed of small particles. While we now understand the “wave-particle duality” of all matter, including electromagnetic radiation, in terms of quantum mechanics, it is still convenient to consider electromagnetic radiation as having the properties of waves in many cases.Light waves can be represented as oscillating perpendicular electric and magnetic fields. The fields are at right angles to each other and to the direction of propagation of the light. The oscillations are sinusoidal in shape, as shown in Figure 2.1(a) . We can easily and accurately measure the wavelength λ, defined as the crest-to-crest distance between two successive maxima. The standard unit of wavelength is the SI unit of length, the meter (m ), but smaller units such as the centimeter (cm ), micrometer (µm), and nanometer (nm ) are commonly used. The amplitude of the wave is defined as the maximum of the vector from the origin to a point displacement of the oscillation. An example of the electric field portion of a light wave propagating along only one axis is shown in Figure 2.1(b) . Such a wave, confined to one plane, is called plane-polarized light. The wave shown represents only a single wavelength, λ. Light of only one wavelength is called monochromatic light
eBook - ePubAnalytical Methods in Chemical Analysis
An Introduction
- Shikha Kaushik, Banty Kumar, Shikha Kaushik, Banty Kumar(Authors)
- 2023(Publication Date)
- De Gruyter(Publisher)
Section III: Spectrochemical methods of analysisChapter 4 UV–visible Spectroscopy
Neeta AzadAbstract
Spectroscopy is one of the important techniques used for the structural analysis of compounds, and it finds its application in all fields of science like Chemistry, Biochemistry, Biology, and Medicines. Spectroscopy deals with the interaction of matter with electromagnetic radiations (EMR). EMR can be categorized into different regions on the basis of their frequencies/wavelengths, and these are gamma rays (γ, highest frequency/lowest wavelength), X-rays, ultraviolet–visible (UV–vis), infrared (IR), microwaves, and radio waves (lowest frequency/longest wavelength). The characteristics of radiations associated with different EM regions are completely different due to their frequencies, as frequency is the measures of energy associated with the EMR. This chapter focuses on UV–visible region of the EM spectrum which falls in wavelength region from 190 to 800 nm. The interaction of matter with radiations in UV–visible region shows wide applicability in our daily life; for example, characterization of colors is done on the basis of their wavelength. Everything around us looks colorful because of visible light. In chemical analysis of compounds, the different color of solutions refers to different concentrations. Similarly, in case of conjugated organic compounds, electronic transitions between various energy states are responsible for their UV–visible spectra. This phenomenon can be studied using Beer–Lambert’s law, which signifies the relation between absorbance of radiations in UV–visible region and concentration of solution under study.The prime concern of this chapter is to present concepts of UV–visible Spectroscopy in a very simple manner, which can be easily understood by undergraduate students. EM spectrum along with the importance of UV–visible region has been discussed in detail with simple examples so that students can correlate the concepts with their daily life. The highlights of this chapter are properties of EMR, origin of spectra, interaction of radiations with matter, and fundamental laws of Spectroscopy. After reading this chapter, questions like how absorption and emission of EMR give rise to emission and absorption Spectroscopy, and how these two are different, can be answered. Along with the explanation of role of transmittance and absorbance in Beer–Lambert’s law, its mathematical treatment has also been elaborated. Important terms and symbols used in absorption measurements and basic principles of instrumentation (choice of source, monochromator, and detector) for single and double beam instrument have also been taken into consideration so that one can apply these concepts while working in laboratory. What are the important instrumental techniques of recording UV–visible spectrum and how to analyze the recorded spectrum? What kinds of compounds are active in UV and visible range? All these concepts are summed up in this chapter.
- Robert A. Scott, Charles M. Lukehart, Robert A. Scott, Charles M. Lukehart(Authors)
- 2013(Publication Date)
- Wiley-Interscience(Publisher)
Many aspects of the large range of electronic Spectroscopy techniques that are available to chemists are well established and relatively routine. Most often, measurements involve the use of solution samples at ambient temperatures. Practically all laboratories are equipped with instruments capable of measuring at least some of these optical phenomena. Companion articles in this volume deal with a number of electronic spectroscopies including Photoluminescence and Electroluminescence (see Photoluminescence and Electroluminescence, Solid State), circular dichroism (CD) (see Circular Dichroism (CD) Spectroscopy), magnetic circular dichroism (MCD) (see Magnetic Circular Dichroism (MCD) Spectroscopy) and Resonance Raman spectroscopies. Any particular spectroscopic technique, once its theoretical and practical framework has been established, can be useful and adapted to relatively routine analytical or diagnostic purposes. The cornerstone analytical techniques of chemistry are perhaps increasingly Mass Spectrometry, nuclear magnetic resonance (NMR) (see Nuclear Magnetic Resonance (NMR) Spectroscopy of Inorganic/Organometallic Molecules ; Nuclear Magnetic Resonance (NMR) Spectroscopy of Metallobiomolecules) and X-ray crystallography. It is often possible to identify the composition and provide the structure of a substance using these techniques alone. Electronic absorption spectra of solutions at room temperature do not usually exhibit the spectral resolution or distinctiveness required of an analytic technique. Most chemical species luminesce only weakly and in this respect electronic spectroscopies play a more specialized and relatively minor role. A combination of spectral techniques is often brought to bear on the complex and interesting systems now under study in modern chemistry
eBook - PDF- Gary D. Christian, Purnendu K. Dasgupta, Kevin A. Schug(Authors)
- 2013(Publication Date)
- Wiley(Publisher)
Chapter Sixteen SPECTROCHEMICAL METHODS Chapter 16 URLs “I cannot pretend to be impartial about colours. I rejoice with the brilliant ones and am genuinely sorry for the poor browns.” —Sir Winston Churchill Learning Objectives WHAT ARE SOME OF THE KEY THINGS WE WILL LEARN FROM THIS CHAPTER? ● Wavelength, frequencies, and photon energy (key equations: 16.1 to 16.3), pp. 479 ● How molecules absorb electromagnetic radiation, p. 480 ● UV–visible absorption and molecular structure, p. 484 ● IR absorption and molecular structure, p. 489 ● Near-IR spectrometry, p. 491 ● Spectral databases, p. 493 ● Beer’s law calculations (key equations: 16.10, 16.13), p. 494 ● Mixture calculations (key equations: 16.16 and 16.17)—use of spreadsheets for calculations, pp. 498, 500 ● Using spreadsheets to calculate unknown concentrations, and their standard deviations from the calibration curve, p. 502 ● Spectrometers (components) for UV, visible, and IR regions, p. 504 ● FTIR spectrometers, p. 523 ● Spectrometric error, p. 526 ● Fluorometry, p. 530 ● Chemiluminescence, p. 538 ● Fiber-optic sensors, p. 540 Spectrometry, particularly in the visible region of the electromagnetic spectrum, Visible spectrometry is probably the most widely used analytical technique. is one of the most widely used methods of analysis. It is widely used in clinical chemistry and environmental laboratories because many substances can be selectively converted to a colored derivative. The instrumentation is also readily available; miniature UV-visible spectrometers are relatively inexpensive and easy to operate. In this chapter, we (1) describe the absorption of radiation by molecules and its relation to molecular structure; (2) make quantitative calculations, relating the amount of radiation absorbed to the concentration of an absorbing analyte; and (3) describe the instrumentation required for making measurements. Measurements can be made in the infrared, visible, and ultraviolet regions of the spectrum.
eBook - PDF- Satinder Ahuja, Neil Jespersen(Authors)
- 2006(Publication Date)
- Elsevier Science(Publisher)
Comprehensive Analytical Chemistry 47 S. Ahuja and N. Jespersen (Eds) Volume 47 ISSN: 0166-526X DOI: 10.1016/S0166-526X(06)47005-7 r 2006 Elsevier B.V. All rights reserved. 111 James Clerk Maxwell predicted the existence of electromagnetic waves in 1864 and developed the classical sine (or cosine) wave descrip-tion of the perpendicular electric and magnetic components of these waves. The existence of these waves was demonstrated by Heinrich Hertz 3 years later. Diffraction of light by transmission and reflection gratings was used to demonstrate the existence of light waves and led to the development of the diffraction equation. n l ¼ d sin y incident sin y reflected ð Þ (5.3) where n represents the order of diffraction and d stands for the spacing between grooves in a diffraction grating. Finally, in the early 20th century Albert Einstein explained the photoelectric effect based on quantized packets of electromagnetic ra-diation called photons. These quickly led to the familiar relationships of the energy of a photon, E ¼ h n ¼ h c l (5.4) and the particle–wave duality expressed by DeBroglie in 1938 l ¼ h m n (5.5) Use of Spectroscopy for chemical analysis most probably can be related to alchemists’ use of flame tests for the qualitative determination of elemental composition. Comparison of colors of solutions, colorimetry, also emerged at that time. Development of light sources, dispersing devices, optics, detectors, modern transducers and digital technology has led to continuing improvement of spectroscopic instrumentation. Modern instrumentation for spectroscopic analysis in the ultraviolet, visible and infrared spectral regions is based on sophisticated principles and engineering, yet is often simple enough to produce accurate results with a minimum of training. 5.1.1 Spectral regions This chapter covers ultraviolet, visible and infrared spectroscopies, the most commonly used range of wavelengths employed by chemists today.
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