Measurement methods nitrate radical

N03 As discussed earlier, the nitrate radical can be measured using visible spectroscopy and its absorption bands, particularly the one at 662 nm. As a result, visible absorption spectroscopy has been the method of measurement used most extensively for NOv As discussed shortly, a matrix isolation technique has also been applied with success in some studies. 

The new methods of measurement and calculation proposed have radically improved the precision and accuracy of determining the thermochemical parameters and, in this way, expanded considerably the potential use of TA in kinetics studies. The methods have been employed to obtain, for the first time, reliable kinetic characteristics and to uncover the mechanism of decomposition of several tens of substances belonging to different classes of inorganic compounds (crystalline hydrates, oxides, hydroxides, nitrides, azides, nitrates, sulfates, carbonates, and oxalates). The results obtained in these studies have been published in the literature in various journals spanning the period from 1981 to 2006). This book draws the work together to make it more accessible for researchers confronted with these issues. 

The heats of formation of alkoxy radicals, RO, have been derived from bond dissociation energies, measured by kinetic methods, in nitrites, nitrates and peroxides, i.e. jD(RO— NO), Z>(RO—NOg) and i>(RO—OR). These bond dissociation energies, taken from Gray s paper 226) shown in Table 5. The heats of formation of... 

Table VIII-D-9 gives the available measurements of the rate coefficient for the reaction of OH with 1-butyl nitrate. Atkinson et al. (1982b), and Atkinson and Aschmann (1989) have used a relative rate method while Nielsen et al. (1991) used both absolute and relative techniques. The absolute and relative rate coefficients of Atkinson and Aschmann (1989) (which supersedes the earlier data of Atkinson et al., 1982b) and Nielsen et al. (1991) are in good agreement. The lUPAC panel preferred value, k= 1.6 X 10 cm molecule" s" with an uncertainty of 20%, is an average of the absolute and relative rate constants of Atkinson and Aschmann (1989) and Nielsen et al. (1991). By analogy with the reaction of the OH radical with 2-propyl nitrate, the temperature dependence of the rate coefficient at temperatures for atmospheric interest is likely to be small (Atkinson et al., 2006).

Using a relative rate method, Treves and Rudich (2(X)3) have measured rate coefficients for reactions of OH radicals with a series of C3-C6 hydroxyalkyl nitrates and two C4 unsaturated hydroxyl nitrates at atmospheric pressure and 296 2 K. Wangberg et al. (1996) have reported the rate coefficient for the OH reaction with 2-nitroxy-l-cyclopentanol also using a relative rate method. The rate coefficient values obtained in both studies are given in table Vlll-G-1. 

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