A Typical EPR Spectrum

It may surprise you that ap is larger than but this fact is consistent with the way the unpaired electron is delocalized through the molecule. In particular, another contributing nobond (hyperconjugative) resonance structure for the propyl radical is written with the unpaired electron directly on Hp  

There is no valid resonance structure that places the electron directly on Ha or Hy. 

Just as we did for H NMR, we can neglect hyperfine coupling to the carbons because of the low natural abundance of (Table 2.1).  

Although the sign of a has no effect on the appearance of an EPR spectrum [just as the sign of J has no effect on an NMR spectrum (Section 9.1)], it does have an effect on CIDNP behavior (Section 11.7). 

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Our studies of Ti02 and Zr02 nano-sized particles prepared by a sol-gel precipitation method [101] (titration with NH4OH and further stabilization of the precipitate with HNO3) showed interesting difference between titanium and zirconium dioxides [89, 90]. Fig. 8.1 performs a typical EPR spectrum of the N02 radical adsorbed on the surface of NC Ti02 thermally treated for 1 h at 200° (parameters are listed in Table 8.4). A similar one with lower intensity has been observed in the case of Zr02 [90],... 

Figure 18-3a shows a typical EPR spectrum of a single crystal of adenosine, x-irradiated and observed at 10 K. This spectrum is obviously complex and not easy to resolve. The problem being that there are overlapping spectra from several radicals. It was therefore necessary to use several techniques to improve the spectral resolution. 

Theoretically, the amount of sample required is no more than that needed to form up to a monolayer on the electrode surface—i.e., about 10 to mole per square centimeter. (A typical EPR spectrum requires about 10 to 1(1 times more material )... 

However at neutral pH, solutions of chromium(VI) containing an excess of glutathione (1 10) rapidly develop a green colour,1454 which slowly decays to a purple colour typical of chromium(III) complexes. Concurrent with the green colour the typical EPR spectrum of a chromium(V) species is observed. Chromium(V) has also been observed in the EPR spectrum of frozen glasses obtained from reaction mixtures of chromium(VI) and glutathione.1455... 

Figure 45. (left) The quantity displayed AB285 is a measure of the spectral width which is reduced by the change of the amplitude of the fast dynamics with temperature different EPR probes (as indicated) were chosen to probe the dynamic crossover Tc values reported are 297 2 K (o-terphenyl, OTP) and 221 2K (polybutadiene, PB). (right) Typical EPR spectrum indicated are two parameters characterizing the line width. (From Ref. 369.)... 

To make sure that the trapped H atoms derive from the substituents of the silsesquioxane cages, d72-QgM8 was prepared in a multistep procedure starting from CD3MgI [3] and y-irradiated. After being irradiated in the solid state at ambient temperature, it shows the typical EPR spectrum of atomic deuterium, as depicted in Fig. 2b. Up to now, EPR spectroscopy is the only means of detecting trapped H atoms with sufficient sensitivity. 

Fig. 4.26 The typical appearance of a simple EPR spectrum is shown by the blue line. This is the first derivative of the absorption peak (shown in red).

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