Radiation-chemical processes spectroscopy

Tripathi GNR (1983) Time resolved resonance Raman spectroscopy of radiation-chemical processes. In Talmi Y (ed) Multichannel Image detectors, vol 2 ACS Symposium Series No. 236, American Chemical Society, Washington D.C. 

Time-Resolved Resonance Raman Spectroscopy of Radiation-Chemical Processes... 

Time resolved electronic absorption and emission spectroscopy has been extensively used for solution phase kinetic studies of fast chemical processes initiated by ionizing radiation. A wealth of information on rate parameters and reaction mechanisms on a variety of chemical reactions has been obtained by this technique. As valuable as these techniques are, they have limitations. In particular, the electronic spectra in solution are often broad and featureless and offer little structural information. As a consequence, the identification of a reaction intermediate is based on chemical intuition and not on its spectral characteristics. Moreover, when more than one transient is present in the system with overlapping electronic absorption, the kinetic monitoring of the individual concentration becomes difficult. Vibra-... 

A review of spectroscopy as a tool for polymerization process monitoring and control is given in this chapter. Initially, fundamental principles of spectroscopy are reviewed, including a brief discussion about the nature and properties of the electromagnetic wave and its interaction with matter, followed by a more detailed discussion about NIR radiation. In the second part of this chapter, cafibration techniques used most frequently for the development and implementation of control applications are briefly discussed. Several applications of spectroscopy to other fields and to other control of polymerization reactors are also included in order to illustrate the versatility of spectroscopic methods for the development of monitoring and control strategies of chemical processes. The final part of the chapter presents relevant applications of the spectroscopic methods for in-situ and in-line monitoring and control of solution, suspension, and emulsion polymerization processes. 

In absorption spectroscopy a beam of electromagnetic radiation passes through a sample. Much of the radiation is transmitted without a loss in intensity. At selected frequencies, however, the radiation s intensity is attenuated. This process of attenuation is called absorption. Two general requirements must be met if an analyte is to absorb electromagnetic radiation. The first requirement is that there must be a mechanism by which the radiation s electric field or magnetic field interacts with the analyte. For ultraviolet and visible radiation, this interaction involves the electronic energy of valence electrons. A chemical bond s vibrational energy is altered by the absorbance of infrared radiation. A more detailed treatment of this interaction, and its importance in deter-... 

Finally, and apart from the importance of micelles in the solubilization of chemical species, mention should also be made of their intervention in the displacement of equilibria and in the modification of kinetics of reactions, as well as in the alteration of physicochemical parameters of certain ions and molecules that affect electrochemical measurements, processes of visible-ultraviolet radiation, fluorescence and phosphorescence emission, flame emission, and plasma spectroscopy, or in processes of extraction, thin-layer chromatography, or high-performance liquid chromatography [2-4, 29-33],... 

MECHANISMS OF SECONDARY REACTIONS. The primary processes involved in absorption of radiation in polymers lead to the expectation of free radical and ionic mechanisms for the secondary chemical reactions. Electron spin resonance (ESR) spectroscopy has proved extremely valuable for observation of free radical reactions in polymers, where various radicals are stabilized in the solid matrix at different temperatures. 

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