Magnetic relaxation spectra

Thus, the starting parameters for the computer-simulation of spectrum IB were chosen to agree with the value of hyperfine fields at 613 K as measured by Rlste and Tenzer, using neutron scattering measurements (36). In addition, the magnetic relaxation rate depends on temperature, as discussed in the Theory section of this paper. 

On the other hand, in the solid-state high resolution 13C NMR, elementary line shape of each phase could be plausibly determined using magnetic relaxation phenomenon generally for crystalline polymers. When the amorphous phase is in a glassy state, such as isotactic or syndiotactic polypropylene at room temperature, the determination of the elementary line shapes of the amorphous and crystalline-amorphous interphases was not so easy because of the very broad line width of both the elementary line shapes. However, the line-decomposition analysis could plausibly be carried out referring to that at higher temperatures where the amorphous phase is in the rubbery state. Thus, the component analysis of the spectrum could be performed and the information about each phase structure such as the mass fraction, molecular conformation and mobility could be obtained for various polymers, whose character differs widely. 

Aksnes, D.W., Hutchison, S.M. and Packer, K.J. (1968) Nuclear spin relaxation and chemical exchange effects in the 19F nuclear magnetic resonance spectrum of the hexafluoroniobate ion. Mol. Phys., 14, 301-309. 

Cvi is the number of vinyl groups per chain. The direct observation of the decrease in amplitude of the Fourier Transform-Infrared spectroscopy (FT-IR) spectrum of vinyl groups leads to a square root dependence of a(t) on time. The threshold of gelation occurs at a time t0 such that e(t0) is equal to zero. Again, the magnetic relaxation rate is a function of the variable, e (Figure 8.4). 

Fig. 14. Schematic of selective excitation and ID exchange spectroscopy, (a) Typical pulse sequence with a soft selective pulse centered at pulsation a>s with a frequency dispersion AcoP <3C Aoj much smaller than the typical linewidth. After an evolution time te smaller or of the order of the spin-lattice relaxation time, a reading sequence of hard pulses that covers uniformly the whole broad line is applied, (b) Effect of a selective excitation on a homogeneously broaden line, (c) Selective frequency labeling of an inhomogeneously broaden line at the irradiation pulsation cos of the first soft pulse. For a soft n pulse, the magnetizations of all the spins that can exchange energy at this pulsation are reversed. By following the difference spectra between the spectra acquired at different evolution times te and the fully relaxed spectrum AS(te) — S(t -> oo) — S(te), limits or evaluation of the correlation time tc of the motion can be achieved.

K the increase in the thermal population of excited electronic levels causes a rapid decrease in the spin relaxation time and a collapse of the spectrum to a single line. The quadrupole splitting is only detected in the magnetically split spectrum. 

The orthochromite, DyCrOa, is paramagnetic above the Neel temperature of 2-16 K, but at 4-2 K a well-resolved magnetic hyperfine spectrum is seen because of a long paramagnetic relaxation time [107]. The parameters (Table... 

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