Spin-lattice relaxation table

The reference scan is to measure the decay due to spin-lattice relaxation. Compared with the corresponding stimulated echo sequence, the reference scan includes a jt pulse between the first two jt/2 pulses to refocus the dephasing due to the internal field and the second jt/2 pulse stores the magnetization at the point of echo formation. Following the diffusion period tD, the signal is read out with a final detection pulse. The phase cycling table for this sequence, including 2-step variation for the first three pulses, is shown in Table 3.7.2. The output from this pair of experiments are two sets of transients. A peak amplitude is extracted from each, and these two sets of amplitudes are analyzed as described below. 

Table 5.4 A comparison of specific surface area ratio calculated from quadrupole splitting (Aq), spin-lattice relaxation rate (Rf, half-height linewidth (Avj/2) and isotherm data for an unbleached linerboard pulp beaten to various degrees.

TABLE 29. 13C NMR chemical shift values (8), observed and calculated" spin-lattice relaxation... 

TABLE 30. 13C NMR chemical shift values (8), spin-lattice relaxation times (T ) and nuclear Overhauser effects (NOE) for /1-carotene (78) in CDCI3 at various magnetic field strengths ... 

TABLE 31. I3C NMR chemical shift values (5), observed and calculated spin-lattice relaxation times (7i ) and observed nuclear Overhauser effects (NOE) for zinc me.vo-tetrapheny I porphyri n (79) in CDCI3 solution at 9.4 T... 

This change in the triplet decay rate constant was verified by ESE measurements where spin lattice relaxation effects can be minimized from the decay rate constant measurements (14). Observed decay rate constants are given in Table I for the y triplet level... 

Also displayed in Table II are spin-lattice relaxation data for liquidlike (CH2) groups that were observable in DPMAS experiments. Both the dependence on temperature and the particular Ti values suggested rapid segmental motions within long runs of methylene groups, quite similar to the dynamic behavior reported for soft-segment CH2 s in synthetic polyesters (19). 

Now it will be necessary to elucidate the location of the butyl isopropenyl ketone unit in the polymer chain. The spin-lattice relaxation time, Tj., of the protons in the polymer and oligomer was measured. The Ti of methylene protons adjacent to the carbonyl group was nearly the same level as the T of methyl protons in the terminal butyl group or terminal methine proton (Table ) but much longer than the T of the protons in interior sequences of polymer (13). These indicate that the butyl carbonyl group in the polymer or oligomer locates at or near to the forefront or the end of the chain. 

Values of the spin Hamiltonian reported for d4 ions are given in Table XI. The difficulty in detecting the ESR is due most likely to short spin-lattice-relaxation times and large zero-field splittings. In both octahedral and tetrahedral fields the 5 D state of d4 gives degenerate orbital states which,... 

Values for the spin Hamiltonian are given in Table XIV. The 5D state of d6 has three orbital states for the ground state in octahedral symmetry. Since these three states are connected by the spin-orbit coupling, the spin-lattice-relaxation time is quite short and the zero-field splitting very large. In a distorted octahedral field the large zero-field distortion makes detection of ESR difficult. In the case of ZnF2 the forbidden AM = 4 transition was measured and fitted to Eq. (164). 

Table 3.15. Spin-Lattice Relaxation Times 7 and NOE Factors t]c of the 13C Nuclei of Cycloalkanes Containing n Carbon Atoms [160].

Table 3.16. Spin-Lattice Relaxation Times T1 of the 13C Atoms in Benzene Derivatives3.

Table 3.17. 13C Spin-Lattice Relaxation Times 7, of Ribo-nuclease A in Aqueous solutions (cone. 0.019 mol/L 45 °C 15.08 MHz maximum deviation +30% [177]).

In ribonuclease A 13C spin-lattice relaxation of the carbonyl and a and / carbon atoms is slower in the denaturated protein than in the native sample [177]. Apparently, the skeleton of this macromolecule becomes more flexible on denaturation, probably owing to conformational changes. However, the s carbons of lysine in the native protein exhibit relatively large T, values which change only insignificantly on denaturation [177]. This behavior is attributed to a considerable segmental mobility of the lysine side chain (Table 3.17 [177]). 

In weakly solvating solvents interionic interactions between organic molecular ions can lead to fixation of the ionic end of the molecule. The Tl values of pertinent and neighboring 13C nuclei become smaller. In contrast, strongly solvating solvents such as water and alcohols inhibit interionic interaction and lead to an enhanced mobility of the ions solvated by ion-dipole interactions 13C spin-lattice relaxation is consequently slower in such solvents. Thus the T, values of n-butylammonium trifluoroacetate increase with the polarity of the solvent, as shown in Table 3.19 [148]. 

Any change in the medium, i.e. the solvent, the concentration, the pH value, and in the temperature will affect the mobility of the molecules and hence also the spin-lattice relaxation. However, few systematic studies have so far been performed on the concentration dependence or on the precise influence of the macroscopic viscosity, the main reason, in the case of 13C, lying in the need for highly protracted measurements in concentration studies. Moreover, little is known about the pH dependence of 13C relaxation [188], Nevertheless, the concentration dependence of 13C relaxation is apparent in the case of saccharose (Table 3.20) [166], and intramolecular hydrogen bonds can be detected by measuring the concentration dependence of Tx [189]. 

Table 3.20. 13C Spin-Lattice Relaxation Times Ti (s) of Saccharose in H20 and D20 at 42PC [166], "ch2oh...

Table 5.30. 13C Chemical Shifts (<5C in ppm) and Spin-Lattice Relaxation Times (TL in sec) of Pro-Leu-Gly-NH2 and its Dimethyl Derivative [839].

Table 5.33. Selected Carbon-13 Spin-Lattice Relaxation Times (in ms) and Rotational Correlation Times (in ns) of Ribonuclease A(H20 [41]).

Pai and coworkers113 investigated in detail both the 29Si chemical shifts and the first spin-lattice relaxation times reported of these systems (Table 12). The spin-lattice relaxation time (7T) for all 29Si nuclei were measured simultaneously by the... 

Table 4. Spin lattice relaxation time (Ti) of 2H of 90% ethanol and potentized homeopathic drugs in 90% ethanol. Figures in parentheses represent chemical shifts in ppm. Measurements were taken by a AMX-400 NMR spectrometer operating at 61.41 MHz at 22°C. Starting with the control other drugs are given in alphabetical...

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