Electromagnetic radiation, interaction with

Light-scattering processes involve the interaction of light with gases or particles in such a manner that the direction or frequency of the light is altered. Absorption processes occur when the electromagnetic radiation interacts with gases or particles and is transferred internally to the gas or particle. 

In spectroscopy we study the effect of interaction of electromagnetic radiation on matter. For examples X-rays are produced by bombandment of metal targets with high speed electrons. So the different types of electromagnetic radiation interact with the matter and give different types of spectroscopy. 

In 1900 Max Planck proposed a solution to the problem of black-body radiation described above. He suggested that when electromagnetic radiation interacts with matter, energy can only be absorbed or emitted in certain discrete amounts, called quanta. Planck s theory will not be described here, as it is highly technical. In any case, Planck s proposal was timid compared with the theory that followed. He supposed that quanta were only important in absorption and emission of radiation, but that otherwise the wave theory did not need to be modified. It was Einstein who took a more radical step in 1905 (the year in which he published his first paper on the theory of relativity and on several other unrelated topics). Einstein s analysis of the photoelectric effect is crucial, and has led to a complete change in the way we think of light and other radiation. 

When electromagnetic radiation interacts with matter it causes the electron density in the material to oscillate at the same frequency as the incident light. Since the interaction of light and matter is a time-resolved process involving many photons, it should not be a surprise that the oscillation produced by... 

In most of the examples described in this book, the rotational angular momentum is coupled to other angular momenta within the molecule, and the selection rules for transitions are more complicated than for the simplest example described above. Spherical tensor methods, however, offer a powerftd way of determining selection rules and transition intensities. Let us consider, as an example, rotational transitions in a good case (a) molecule. The perturbation due to the oscillating electric component of the electromagnetic radiation, interacting with the permanent electric dipole moment of the molecule, is represented by the operator... 

Concentrating on metalloenzymes, we have developed a strategy based on stopped flow X-ray absorption spectroscopy (XAS) to elucidate in detail the molecular mechanisms at work during substrate turnover (Fig. 4). Importantly, XAS provides local stmctural and electronic information about the nearest coordination environment surrounding the catalytic metal ion within the active site of a metalloprotein in solution. When the X-rays hit a sample, the electromagnetic radiation interacts with the electrons bound in the metal atom. The radiation can be scattered by these electrons, or it can be absorbed, thereby exciting... 

An understanding of these effects can be simplified by assuming that polarization is a scalar quantity (as opposed to a vector). Following the approach of Williams (43), when electromagnetic radiation interacts with a... 

When electromagnetic radiation interacts with a medium it induces a polarization P which is proportional to the electrical field E due to the radiation ... 

Very detailed information about structure is obtained from investigations in which electromagnetic radiation interacts with matter. An important area of study, known as spectroscopy, is concerned mainly with the extent to which substances absorb radiation at various wavelengths. The information obtained through spectroscopy has contributed greatly to our understanding of chemical structure and is particularly important in biology. 

When electromagnetic radiation interacts with a molecule, certain transitions between states can occur, and others cannot. There are selection rules which tell us which transitions are possible and which are not. The detailed theory underlying these selection rules is fairly complicated, but some important general conclusions can be stated. 

There are three ways in which ionizing (electromagnetic) radiation interacts with matter, viz. 

How does Electromagnetic Radiation interact with Matter ... 

PAS is a technique based on the so-called optoacoustic effect When a short pulse of electromagnetic radiation interacts with condensed matter, the absorbed energy is converted into heat by fast nonradiative relaxation processes. Subsequently, the thermal expansion of the instantaneously heated medium causes an acoustic pulse, which is detected. 

When the electric field of electromagnetic radiation interacts with a material, it induces a dipole moment in the material. The dipole moment induced per unit volume is called "polarization." At low electric fields, the inacroscopic polarization or polarization of the bulk medium. P. is linearly related to the field by the proportionality constant, knovm as the linear electric susceptibility. At high fields, typically those associated with lasers, contribution of the nonlinear (second- and... 

The interaction of light and molecules forms the basis of IR spectroscopy. Here it will be given a short description of the Electromagnetic Radiation, the energy levels of a molecule and the way the Electromagnetic Radiation interacts with molecules and their structure [5,6]. 

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