ESR signal, decay

The decay of a radical-anion can be followed directly by generating the intermediate within the cavity of an esr spectrometer through application of a controlled potential pulse to the cathode of a thin electrochemical cell [46]. Loss of the radical-anion is then followed by decay of the esr signal. Decay is second order in radical-ion concentration for dimethyl fumarate (k = 160 M s ) and for cin-namonitrile (k = 2.1 x 10 M s ) in dimethylformamide with tetrabutylammonium counter ion. Similar values for these rate constants have been obtained using purely electrochemical techniques [47]. 

Hammond and coworkers (147,349,374) have developed a rotating sector method to measure by ESR the bimolecular decay of radicals produced by photolysis. Calvin and coworkers (148) have also studied the kinetics of ESR signal decay by intermittent UV-irradiation of charge-transfer complexes. A CAT was used by both groups to... 

Table 6.2 ESR Signal Decay and Refractive Index Measurements as a Function of Plasma Type and Deposition Method...

Plasma Method Type of radical ESR signal decay Refractive index... 

While the ESR signal decay showed only a decrease in intensity when A1 was used as the substrate, the complex spectrum observed when PE was used as the substrate continued to ehange its pattern. A decrease the spectral intensity and sharpening of the eentral ESR line were observed (Fig. 6.13). In addition air exposure (7 days) of the coated fibers resulted in a inajor change where only toe eentral line was observed. Similar signals were also observed du 4 P... 

Figure 6.15 Effect of air exposure on the ESR signal obtained by the DC cathodic plasma deposition (5 W, 50 mtorr, 3 min) of TMS (a) ESR signal decay with storage time in air (b) ESR signal intensity from two identical samples one sample was held in vacuum for 72 h showing no decay in vacuum and rapid decay when exposed to air, the other identical sample was exposed to air for 72 h showing decay with time.

Figure 6.20 (a) Comparison of the ESR signal decay after 0.3 and 24h from the plasma coating of 1 min TMS followed by 1 min of plasma treatment of O2, H2, Ar, HFE and the plasma coating of CH4 (b) Comparison of the effect of H2 plasma treatment on plasma pol5mier of TMS and of CH4, where the number in parenthesis indicates the treatment time in minute. 

Fig. 20. Increase of the intensity of the ESR signal during the irradiation and its decay in darkness of a bromine complex of a poly(schiff base) prepared by polycondensation of 4,4 -diacetyldiphenyl sulfide and p-phenyienediamine mole ratio 1 S.8...

Fig. 17. Decay of the ESR signals of 1 (left) and anti,anti,anti-4 (right) in THF.

Fig.Zl (a) Influence of CNT concentration in presence of Kj[Fe(CN)J on intensity of the ESR spectra of the paramagnetic label TEMPON control (without CNT) (7) and adding CNT to blood erythrocytes at 0.01 (2), 0.05 (5), 0.1 (4) and 0.2 (5) mg/mL (b) kinetics of the ESR signal intensity decay of the paramagnetic label in liver homogenate after 4 h inoculation 1 - control (without CNT), 2 - in presence of CNT with concentration 0.2 mg/mL...

The fates of the radicals produced in the second and third equations are matters for conjecture. Since the ESR signals attributed to them decay by second-order processes (12, 13), disproportionation reactions such as... 

Schuh and Fischer [40] have studied the recombination of f-butyl radicals formed by UV photolysis of di-f-butyl ketone in six n-alkanes. The f-butyl radical concentration was 0.1—1.0 jumol dm-3 and reaction of the radicals occurred over times of a few milliseconds by a second-order kinetic mechanism as determined by following the decay of the f-butyl ESR signal. 

Figure 12. Growth and decay of the photoinduced ESR signal in lOH polymer extracts at the different temperatures indicated. Illumination commences at time zero and terminates at the time indicated by the arrow. The spectral range used was from about 570 to 700 nm.

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