Electromagnetic radiation introduction

Figure 6.89 Energies, wavelengths, and frequencies of various categories of electromagnetic radiation. Reprinted, by permission, from W. Callister, Materials Science and Engineering An Introduction, 5th ed., p. 709. Copyright 2000 by John Wiley Sons, Inc.

The depth of introduction can be varied by technical tools as well. Transmission techniques can be applied for bulk analysis, while reflection techniques are appropriate to the study of the interfaces. Transmission and reflection techniques can be applied using a wide range of electromagnetic radiation, from infrared to x-ray ranges. Moreover, particle radiation (e.g., the neutron scattering technique) can also be used for the study of the structure of interfaces. 

As defined by the lUPAC "Photochromism is a reversible transformation of a chemical species induced in one or both directions by the absorption of electromagnetic radiation between two forms A and B, having different absorption spectra" (2). Articles by Exelby and Grinter (25), Dessauer and Paris (26), and Bouas-Laurent and Dlirer (27) give a good introduction to the phenomena. 

Since this chapter is devoted to quantitative analysis of the IRRAS spectra, for completeness of the presentation, we provide fundamentals of reflection of light at interfaces, although this material is available elsewhere [19-21]. The next section consists of a brief introduction to the reflection, refraction, and absorption of electromagnetic radiation at a simple two-phase boundary. The section that follows presents Fresnel equations in the matrix form that describes the reflection and refraction of electromagnetic radiation at a multilayer interface [19]. 

As an introduction to the main topics of this book - atomic structure and the periodicity of atomic properties - the foundations of the subject, which lie in quantum mechanics, and the nature of atomic particles and electromagnetic radiation are described. 

Figure 11.1 Electromagnetic radiation can excite transitions in moiecuies from one rotational energy level of a particular vibrational state v to a different level. The frequency of excitation radiation corresponds to the energy change of the transition, through the relation Ae = hv. Shown here is the absorption band of gas-phase HBr in the infrared region. Source CM Barrow, The Structure of Molecules an Introduction to Molecular Spectroscopy, 2nd printing, WA Benjamin, New York, 1964. Series title The general chemistry monograph series.

Smith GS. An Introduction to Classical Electromagnetic Radiation. Cambridge Cambridge University Press 1997. 

Smith, G.S. (1997) An Introduction of Classical Electromagnetic Radiation, Cambridge University Press, Cambridge, pp. 1-107, Chapter 1. 

Introduction to spectroscopy starts by looking at the properties of electromagnetic radiation. Emission and absorption processes in atomic spectroscopy are revised. The interaction of radiation with a vibrating diatomic molecule is considered for both infrared and Raman spectroscopy. 

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