Electromagnetic spectrum properties

Spectroscopy, or the study of the interaction of light with matter, has become one of the major tools of the natural and physical sciences during this century. As the wavelength of the radiation is varied across the electromagnetic spectrum, characteristic properties of atoms, molecules, liquids and solids are probed. In the... 

The scattering of visible light by polymer solutions is our primary interest in this chapter. However, since is a function of the ratio R/X, as we saw in the last section, the phenomena we discuss are applicable to the entire range of the electromagnetic spectrum. Accordingly, a general review of the properties of this radiation and its interactions with matter is worthwhile before a specific consideration of scattering. 

Excimer lasers use gases, but because of their special properties are usually considered as a class of their own. Excimer is short for excited dimer, which consists of two elements, such as argon and fluorine, that can be chemically combined in an excited state only. These lasers typically emit radiation with veiy small wavelengths, in the ultraviolet region of the electromagnetic spectrum. This shorter wavelength is an enormous advantage for many applications. 

The Electromagnetic Spectrum. The optical properties of a material are related to the electromagnetic spectrum (see Ch. 15, Fig. 15.1). The portions of the spectrum of interest are the following ... 

Interrogating the light from stars and the absorption features of atoms and molecules in-between requires some fairly complicated optics in the form of a telescope. However, the telescopes are not restricted to the parts of the electromagnetic spectrum that you can see but use radiation from microwaves to gamma rays to observe the Universe. There is too much to learn about the optics or even adaptive optics of telescopes to be discussed here but there are some properties of telescopes that we must know because they are important for the identification of atoms and molecules. We shall discuss three telescope considerations the atmosphere, the spatial resolution and the spectral resolution. 

Material response in THz frequency region, which corresponds to far- and mid-infrared electromagnetic spectrum, carries important information for the understanding of both electronic and phononic properties of condensed matter. Time-resolved THz spectroscopy has been applied extensively to investigate the sub-picosecond electron-hole dynamics and the coherent lattice dynamics simultaneously. In a typical experimental setup shown in Fig. 3.5, an... 

Transitions between different electronic states result in absorption of energy in the ultraviolet, visible and, for many transition metal complexes, the near infrared region of the electromagnetic spectrum. Spectroscopic methods that probe these electronic transitions can, in favourable conditions, provide detailed information on the electronic and magnetic properties of both the metal ion and its ligands. 

You probably recall that visible light is part of a broader continuum of energy called the electromagnetic spectrum. Figure 3.6 reviews the key properties of the electromagnetic spectrum of energy. 

The existence of an ozone layer was first suggested in 1878 by the French physicist Alfred Cornu (1841-1902), who detected a reduction in the amount of sunlight reaching Earth s surface in the region of the electromagnetic spectrum between 240 and 310 nanometers (nm). Cornu hypothesized that the reduction in sunlight was caused by the presence of some chemical substance in the atmosphere that absorbed the radiation. His suspicions were confirmed two years later when the English chemist Walter Noel Hartley (1846-1913) measured the optical properties of ozone and was able to show that it satisfied the conditions of Cornu s absorber. 

The creation by the Federal Communications Commission (FCC) of new property rights for personal communication services (PCS) is instructional. The new PCS services are thought by investors to be so valuable that their bids for electromagnetic spectrum rights include payments to buy out the current users of that portion of the spectrum and set them up with equivalent personal communications services (Andrews 1992). 

Many classifications of spectra exist those describing the spectral region involved (ultraviolet, infrared) the appearance of the spectra (line, band) the method of observation (absorption, emission) or the species producing the spectra (atoms, molecules). With respect to processes and properties of expls and proplnts, classification by species is most appropriate since information concerning reaction kinetics is frequently provided by spectroscopic techniques, From a spectroscopic viewpoint, it is convenient to divide the electromagnetic spectrum into a number of sections (see Fig 1). 

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