Intermediary free radical species

Marty methods, which include absorption spectroscopy [38], Foirrier-transform spectroscopy [39], electron spin resonance [40], laser magnetic resonance [41], resonance fluorescence [37, 38], MS [42], and other chemical means, require special conditions of radical concentration or are applicable only to certain radicals with special properties [43]. In fact, many radicals have been detected to date, by MS with low-energy electrons [42], radical trapping in a Cl source [44], or photons [45]. However, a nrrmber of interfering factors which are encourrtered in practice 

This section describes a new method for detection and identification of intermediate radical species in the gas phase. This method is based upon the establishment of an alkah ion attachment to radicals through termolecular reaction. It provides mass spectra of quasi-molecular ions formed by lithium ion attachment to the radical species (R) under high pressure. Results are obtained in the form of a mass spec-trometric trace of LT adduct radicals. The advantages of the present method are (i) a measme of mass is a guide to radical identity, (ii) adaptability to a condition of higher pressures, and (hi) direct continuous measurements of any species in dynamic systems can be made. The method is apphed to the study of the microwave (MW) discharge in CH, C, CHy02, or CH4/N2 and was successfully 

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In this section, the development of a LC lAMS is described. Section 5.2.2 summarizes the MS instrumentation for the alkali-metal ion/molecule association reaction a quadmpole mass spectrometer (QMS), combined with the Li+ ion attachment ionization source (model L-241G-I A, Canon Anelva Corp, Tokyo). The performance and response of this equipment and unique features are also presented (Sect. 5.2.3). Finally, the interesting applications are reviewed. There are some interesting and unusual applications of lAMS that broaden MS (i) intermediary free radical species detection, in the gas phase reactions, diagnosis of plasma and diamond film chemical vapor deposition (CVD), (ii) detection of atmospheric and interstellar species, (iii) detection of environmentally important species, and (iv) identification of unfamiliar or unstable species. Restriction of Hazardous Substances Detectives (RoHS) is also discussed. 

In quite a number of these applications, lAMS actually broadens the potential application of MS, enabling the detection of intermediary free radical species, of atmospheric and interstellar species, of environmentally important species, and the identification of unfamiliar or imstable species. Ample examples of this have been summarized in Chap. 5. 

Aminyls ( N ), aminium radicals ( N +H) and nitroxides ( NO ) are the free radical species formed from HAS in oxidative processes. An intermediary formation of aminyls in HAS mechanism was proposed [170] as a result of the reactivity of NH with excited chromophores, acyl- and peracyl radicals, alkylperoxyls or alkylhydroperoxides (Scheme 12). 

The reactivity of metal-ion attachment to organic molecrrles has stimrrlated further interest in alkali-metal ion Cf. Metal ions have been used as special reagents in analytical MS to provide new or improved information for analytical chemistry [43]. The adduct ions can be used to determine relative molecrrlar weight of im-known species and to find numerous applications in the analysis of rrrixtures. The target species includes intermediary free radical arrd other species [44], which are sometimes not found under ordinary conditiorts (see Chap. 5). 

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