Spin signals, characteristics

Such a short spin-equilibrium relaxation time raises the question of whether discrete spin state isomers exist. Their existence is affirmed by two observations. One is the persistence of electronic spectral bands typical of the low-spin 2E state over a wide temperature range in solid samples (98). The other is the observation of EPR signals characteristic of the 2E state in both solids and solutions between 4 and 293 K (98,139). At very low temperatures EPR signals of both spin states can be observed simultaneously (98). At low temperatures hyperfine splitting into eight lines is observed from coupling with the 1 = 7/2 Co nucleus. As the temperature is raised the spectral features broaden and the hyperfine resolution is lost. This implies a relaxation process on the EPR time scale of 1010 sec-1, or a relaxation time of the order 0.1 nsec, consistent with the upper limit set by the ultrasonic experiments. 

Notable exceptions to this observation on deposition rates are found for acrylic acid and tetrafluoroethylene. In order to visualize the overall effect of a pulsed discharge, one should refer to the data given in the following tables polymerization parameter in Table 7.8a, pressure parameters in Table 7.8b, deposition rates of polymers in Table 7.9, characteristics of ESR spin signals in Table 7.10, and contact angles of water in Table 7.11. 

Early experiments determined that the spin signal was a bulk and not a surface effect (Brodsky and Title, 1969), although there are some surface contributions (Suzuki et al., 1980). In measurements of very pure films made under ultrahigh vacuum (UHV) conditions, Thomas et al. (1974) showed that the characteristic ESR signal is an intrinsic property of the films and not due to the presence of impurities. 

The radical ions formed should show an ESR (electron-spin resonance) signal, but frequently a signal characteristic of only one species is observed. 

A very important characteristic of spin-spin splitting is that protons that have the same chemical shift do not split each other s signal Ethane for example shows only a single sharp peak m its NMR spectrum Even though there is a vicinal relationship between the protons of one methyl group and those of the other they do not split each other s signal because they are equivalent... 

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