Inversion-recovery spin-lattice relaxation

M. Sass and D. Ziessow, "Error analysis for optimized inversion recovery spin-lattice relaxation measurements," J. Magn. Resonance 25, 263-276 (1977). 

Figure Bl.13.4. The inversion-recovery detennination of the carbon-13 spin-lattice relaxation rates in melezitose. (Reproduced by pemiission of Elsevier from Kowalewski J and Maler L 1997 Methods for Structure Elucidation by High-Resolution N R ed Gy Batta, K E Kover and Cs Szantay (Amsterdam Elsevier) pp 325-47.)...

Canet D, Levy G C and Peat I R 1975 Time saving in C spin-lattice relaxation measurements by inversion-recovery J. Magn. Reson. 18 199-204... 

The technique for measurement which is most easily interpreted is the inversion-recovery method, in which the distribution of the nuclear spins among the energy levels is inverted by means of a suitable 180° radiofrequency pulse A negative signal is observed at first, which becomes increasingly positive with time (and hence also with increasing spin-lattice relaxation) and which... 

Figure 2.27. Sequence of measurements to determine the C spin-lattice relaxation times of 2-octanol (42) [(CD3)2C0, 75% v/v, 25 °C, 20 MHz, inversion-recovery sequence, stacked plot]. The times at which the signals pass through zero, xo, have been used to calculate, by equation 10, the T values shown above for the nuclei of 2-octanol...

The most popular, and also a very accurate, experimental method for measuring nonselective spin-lattice relaxation-rates is the inversion recovery (180°-r-90°-AT-PD)NT pulse sequence. Here, t is the variable parameter, the little t between pulses, AT is the acquisition time, PD is the pulse delay, set such that AT-I- PD s 5 x T, and NT is the total number of transients required for an acceptable signal-to-noise ratio. Sequential application of a series of two-pulse sequences, each using a different pulsespacing, t, gives a series of partially relaxed spectra. Values of Rj can... 

Selective, spin-lattice relaxation-rates are measured by the inversion-recovery technique. A rather weak, 180° pulse of very long duration (10-50 ms) inverts a multiplet (single-selective) or two multiplets (double-selective) in the spectrum of asperlin (1 see Fig. 2 ) and the recovery of the... 

Inversion recovery A pulse sequence used to determine spin-lattice relaxation times. 

FIGURE 31. Typical data set for measurement of the spin-lattice relaxation times of the sp2-hybridized carbon atoms of, 6-carotene at 11.7 T. The chemical shift values are shown across the bottom of the figure. The t-value for each spectrum is the delay time in the inversion-recovery pulse sequence. Reprinted with permission from Reference 49. Copyright (1995) American Chemical Society... 

Spin-lattice relaxation times were measured by the fast inversion-recovery method (24) with subsequent data analysis by a non-linear three parameter least squares fitting routine. (25) Nuclear Overhauser enhancement factors were measured using a gated decoupling technique with the period between the end of the data acquisition and the next 90° pulse equal to eibout four times the value. Most of the data used a delay of eibout ten times the Ti value. (26)... 

Polymer Dynamics. 13C spin-lattice relaxation times (Ti) were determined with either an inversion-recovery sequence (16) (for carbons observed by direct polarization) or with a modified cross-polarization experiment (17). 13C rotating-frame relaxation times (Tip(C)) were derived from measurements of the carbon signal that remained after a Tjp(C) hold time of... 

Fig. 1. Pulse sequences for determining spin-lattice relaxation time constants. Thin bars represent tt/2 pulses and thick bars represent tt pulses, (a) The inversion-recovery sequence, (b) the INEPT-enhanced inversion recovery, (c) a two-dimensional proton-detected INEPT-enhanced sequence and (d) the CREPE sequence. T is the waiting period between individual scans. In (b) and (c), A is set to (1 /4) Jm and A is set to (1 /4) Jm to maximize the intensity of IH heteronuclei and to (1/8) Jm to maximize the intensity of IH2 spins. The phase cycling in (c) is as follows 4>i = 8(j/),8(-j/) 3 = -y,y A = 2(x),2(-x) Acq = X, 2 —x), X, —X, 2(x), —x, —x, 2(x), —x, x, 2 —x),x. The one-dimensional version of the proton-detected experiment can be obtained by omitting the f delay. In sequence (d), the phase 4> is chosen as increments of 27r/16 in a series of 16 experiments.

The NMR spectra were taken on a JEOL JNM-MH-100 (CW) spectrometer using tetramethylsilane as an internal standard. 13C spin-lattice relaxation time of the polymer was measured by the inversion-recovery Fourier transform method on a JNM-FX100 FT NMR spectrometer operating at 25 MHz. 

Spin-lattice relaxation times 7j of individual nuclei (13C, H) present in a molecule can be obtained by Fourier transformation of the FID signal following a 180°, r, 90° pulse sequence. The technique is referred to as inversion-recovery method [39, 40, 41] or... 

Fig. 2.30. Determination of 13C spin-lattice relaxation times by inversion-recovery (a), progressive saturation (b), and comparative evaluation of the intensities (c) values from (a) with full, from (b) with empty characters, abscissa on top for C-2, abscissa on bottom for C-1 and C-3) sample propynol, 75% by vol. in hexadeuterioacetone. 25 C, not degassed, 15.08 MHz, 10 scans/ experiment in (a),...

Fig. 4.15. Inversion-recovery experiment for carbon-13 7, determination or2,2 -bipyridine (400 mg in 1 mL hexadeuteriobenzene, 30 °C 15.08 MHz 16 scans for a single experiment [73 i]). The principal axis of (the fastest) molecular rotation passes C-2 (2 ) and C-5 (5 ). This rotation is too fast for optimum dipolar relaxation of C-3, C-4, and C-6 but does not influence the C-5-H bond which is affected by rotation about other axes. These rotations are slower and more effectively contribute to dipolar spin-lattice relaxation of C-5 (5 ) according to Section 3.3.3.3. To conclude, C-5 (5 ) relaxes faster (3 s) than all other CH carbons (6 s) and can be clearly distinguished from C-3 (3 ) with similar shift.

Finally, a coupled and decoupled 13C NMR spectrum of 2,2 -bipyrrole (Fig. 4.14(a,b) and an inversion-recovery series of 2,2 -bi pyridine (Fig. 4.15 [73 i]) illustrate signal assignments of heteroaromatic compounds by means of carbon-proton couplings and spin-lattice relaxation times. These spectra also exemplify the characteristic shift differences between n-excessive (2,2 -bipyrrole) and n-deficient heteroaromatic compounds (2,2 -bipyridine). 

In order to determine the content of this noncrystalline line further, we examined in more detail the behavior of the spin-lattice relaxation. Figure 5 shows the partially relaxed spectra in the course of the inversion recovery pulse sequence (180°-t-90°-FIDdd-10s)i2o with varying x values. The magnetization that was recovered for 10 s in the z direction was turned to negative z direction by 180° pulse and the magnetization recovered in z direction for varying x was measured in the xy plane under H DD. The spectra at different steps of the longitudinal relaxation were obtained by Fourier transform and are shown in Fig. 5. In these spectra the contribution from the crystalline components with Tic s of2,560 and 263 s are eliminated due to the lack of time for recovery at each pulse sequence. Therefore, we observed preferentially the relaxation process of the noncrys-... 

By using the inversion recovery method with the standard pulse sequence (180°-t-90°-T), it is possible to determine the spin-lattice relaxation times in the supercritical state. The values of benzyl-n-butylphthalate have been... 

Relaxation parameters provide valuable information about molecular motions. The spin-lattice relaxation time T is usually determined by the so-called inversion recovery pulse sequence (65). The experiment comprises a set of spectra with different interpulse delays, and Tx is determined by fitting the signal intensities for a given nucleus to Eq. 2, where A and B are constants, x is the respective interpulse delay, and /,is the intensity measured at that delay ... 

Figure 10.5 compares the spin-lattice relaxation time (7)) obtained after inversion-recovery sequences of the APP/PER and the APP/PER-4A systems versus heat treatment temperature (HTT). At every HTT, only one 7) value was obtained and it can be therefore expected that the slow relaxation domains size will be smaller than 10 nm. 

FIGURE 51. Measurement of 29Si spin-lattice relaxation time in 1,1,3,3-tetramethyldisilazane using conventional inversion-recovery (top, measuring time 6.5 h, T = 37.6 1.4 s) and INEPT enhanced version (bottom, measuring time 45 min, T = 38.1 0.9 s) with the phase of penultimate proton pulse +y. Reproduced by permission of Academic Press from Reference 357... 

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