Line width, gauss

ESR parameters Humic acid Chlorophenoxy compounds Free radical concentration (spins 10 ) Line width (gauss) Spectroscopic splitting factor (g — values) ... 

Line Catalyst Frequency Line width (gauss) g factor ... 

Carbon black type Concentration (phr) g-value Line width (gauss) (298 K) 77 K... 

The electron spin resonance of the nitroxalkylcorrinoids can be readily observed in aqueous solution at room temperature. Both the cobalamin and cobinamide show nitrogen hyperfine coupling constants of 17.2 gauss. A typical spectrum is shown in Fig. 20. The line widths for the low, intermediate, and high field peaks are 1.87, 1.87, and 2.20... 

Our analysis thus far has assumed that solution of the spin Hamiltonian to first order in perturbation theory will suffice. This is often adequate, especially for spectra of organic radicals, but when coupling constants are large (greater than about 20 gauss) or when line widths are small (so that line positions can be very accurately measured) second-order effects become important. As we see from... 

At either frequency the sensitivity of the instrument is quite remarkable. The exact signal-to-noise ratio depends upon a number of factors including apparent line width (including g and hyperfine anisotropy), ease of saturation, the temperature, and the linear density of the sample in the quartz tube. For a relatively narrow line with peak-to-peak separation of two gauss it is possible to observe the spectrum for concentrations as low as 1014 spins per gram of sample. As the spectrum becomes more anisotropic, the sensitivity of course decreases. Lowering the temperature increases the sensitivity since the population difference An increases [(Eqs. (26) and (3°)]. 

After the sample had been heated to —95°C. for 10 minutes, the spectrum was quantitatively transferred into a singlet with the line width of 17 gauss (Affmsi). This spectrum was interpreted as caused by polyenylic radicals (III). After heating to room temperature, no detectable concentration of radicals was found. In another study (4, 5) of ultraviolet-irradiated polyethylene, the sextet spectrum was also observed together with a singlet. The singlet spectrum was ascribed to peroxy radicals formed by the air present in the sample tube. 

Adding the proton-free solvent carbon tetrachloride to polystyrene, one observes the relationship between line width and temperature as shown in Figures 5a and 5b. For the system polystyrene with 21.5% carbon tetrachloride the absorption curves for various temperatures are plotted against the field strength (2) in gauss. As the temperature decreases, the line broadens, as shown more clearly in... 

The line widths recorded are the distances, in gauss, between the two maxima of the differential curve and thus represented the width of the absorption curve at the level of maximum slope. For a curve of Lorentzian shape, this width is equal to 0.577/T2, where T2 is the spin-spin or transverse relaxation time (12). Since the curves were not strictly Lorentzian (though they were so to well below the region of maximum slope) and in any case were not of identical shape, the recorded line widths do not have this exact theoretical significance, and small differences in width between two samples could be caused by shape differences rather than variations in relaxation phenomena. Nevertheless, since the conclusions drawn later from the observed line widths depend on major differences in level rather than subtle differences in numerical value, they should be perfectly valid. 

Pyrolyzed at 630 C., line width 2.8 gauss, 113.9 X 1018 spins/gram and at 730 C., line width 2.3 gauss, 2.72 X I018 spins/gram. 

Cornelius Steelink. We have found line widths of less than 4.0 gauss for humic acids and model compounds. 

Here, H can be conveniently expressed as the deviation of the field from the center of the resonance in gauss units H=H —H0 yb,ym, and yn are the elementary spectra of the broad, the medium, and the narrow components, respectively. These are considered to be contributed from protons belonging to the crystalline region, and hindered-rotational and micro-Brownian mobile methylene groups in the amorphous region, respectively. pb,pm, and 0n determine the line-width and breadth of the respective elementary spectra wb, wm, and iv designate the respective mass fractions. Each elementary spectrum is normalized as... 

Milled wood lignin is carefully packed into a quartz sample tube and inserted into the ESR cavity. Turn on the instrument and by following the procedure described above, a singlet signal with a g-value of 2.0023 and a line width of 16 gauss will be detected (Fig. 5.5.5) The concentration of this particular lignin... 

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