Inversion-recovery technique

H longitudinal relaxation time, measured by the inversion-recovery technique, at 293 K. 

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... 

Extensive 13C and 81P n.m.r. studies have been reported for phosphine oxides and selenides, and the inversion-recovery technique has been used to establish 2J and ZJ values for 18C-31P coupling.52 Shift reagents have been used to establish alkene geometry in the oxides (61).53 Coupling and shift data have been published for the arylphosphine derivatives (62).54... 

The first measurement of steroid 13C Tx values was reported (31) for cholesteryl chloride in 1 m carbon tetrachloride at 42 °C using the conventional 180°-r-90° inversion-recovery technique. The values obtained are given in Fig. 2. 

Fig. 2. Determination of the relaxation times of (V-cyclo-QHja )Ni(Br)P[CH(CHs )ji (7) by the inversion recovery technique (toluene, 35°C, 25.2 MHz). The spectra have been stacked as a function of the time interval between the 180° and 90° pulses.

The spin echo technique is a multipulse sequence used (among other things) to measure true T2 values. The spin inversion-recovery techniques is a multipulse 2D technique for measuring T values. 

Distinguish clearly between a one-dimensional NMR experiment that uses a time increment, such as the inversion-recovery technique (Section 2.9 and Fig. 8.8a), and a two-dimensional NMR experiment, such as NOESY. 

The decay time constants for the polymeric radicals clearly vary from solvent to solvent, ranging over an order of magnitude from about 2 ps in tetrahydrofuran (THF) to 200 ns in methylene chloride. A similar solvent dependence of NMR Ti values has been reported by Spyros et al. They studied poly(naphthyl methacrylate) using the inversion recovery technique and found that the spin-lattice relaxation time of... 

In contrast to the saturation recovery technique, negative z magnetization can be generated, but care must be taken to start from thermodynamic equilibrium. If these techniques are used for generation of T contrast in NMR images, different contrast is obtained because signal is suppressed by the saturation recovery technique while it is preserved but inverted by the inversion recovery technique. 

Rg. 29. A O NMR spectrum of 0.5 mM D- uc( e in H2O at 353 K recorded at 48.8 MHz. (A) Reference spectrum acquired using ttfl pulses. TTie baseline is distorted due to acoustic ringing effects. (B) Combination of the inversion-recovery technique with the RIDE sequence for acoustic ringing elimination. TTie asterisk denotes the water resonance. (From Schulte and Lauterwein with permission.)... 

Relaxation times Ti were obtained using the inversion-recovery technique (7T-T-7r/2-acq), while the F Tip relaxation times were measured by means of the variable-time spin-lock technique, and Tip was obtained via F resonance by a variable spin-lock followed by H F cross polarisation. In all cases decoupling of the complementary nucleus was not implemented during the variable time allowed for relaxation. The F relaxation times all show single-exponential decay of the magnetisation as a function of... 

Quantitative measurements were performed by data accumulation at a recycle time greater than 5Tj of the resonance of interest. The spin lattice relaxation times, Tj, of hydrogen on the metal were determined by the inversion recovery technique [3]. Absolute intensities were obtained by referring to a water sample. The reference sample was sealed in a capillary tube of the length of the catalyst samples to account for field inhomogeneities in the NMR coil [2]. 

The spin-latice relaxation time (Ti) can be determined by the inversion recovery technique. The echo signal grows exponentially with time r between the pulses as... 

As an introduction, our previous studies on the conformations of maleic acid copolymers with aromatic vinyl monomers are summarized. To characterize the compact form and the pH-indueed conformational transition of the maleic acid copolymer with styrene in aqueous NaCl, 400 MHg H-NMR spectra were measured. The spectral form depended on the molecular conformation. Because each of proton resonance peaks could not be separated, the spin-lattice relaxation time T was estimated by using the inversion recovery technique (tf-t-tf/2). The T s for both side chain and backbone protons reflected the transition, and the protons were considered to be in a more restricted motional state in the compact form than in the coil form. Also, from temperature dependence of each Tj, motion of the copolymer in the coil form was described in terms of the local segmental jump (D) combined with the isotropic rotational motion (O), when a ratio between both the correlation times tq and Tq was about 0.07. For the compact form, the ratio was found to be about 10. By referring to theoretical diagram of Tj vs. tq for the methylene protons on the backbone, value of Tn for the compact form was compared with that for the coil form at 35 C. 

Spin-lattice relaxation times (Ti) for the a-carbon region were determined by the inversion-recovery technique [19]. Nuclear Overhauser Enhancements (NOE) were measured by the gated decoupler method [20]. 

It is possible to monitor relaxation times by modulating the microwave amplitude at a rate close to the inverse spin-lattice relaxation time, Tj (Misra, 2004). This is due to the fact that if the microwave amplitude is changed faster than that which the spins can follow as governed by the electron SLR time, the EPR signal is determined predominantly by T. This modulation technique permits measurement of relaxation times in the interval between the values that are slow enough to be measured by the recovery techniques and the values that are too fast to have any significant impact on continuous wave (cw) lineshape. These latter relaxation times can be as short as 10 s, which is substantially shorter than those that can be measured by the saturation/inversion recovery techniques. 

Alger RS. 1968. Electron paramagnetic resonance techniques and applications. New York Interscience Publishers (inversion-recovery technique). 

The following pulse sequence is used in the inversion recovery technique a 180° pulse is followed by a time interval t, then a 90° pulse, acquisition of a FID curve, and Fourier transformation. 

There are a number of methods for the determination of spin-lattice relaxation time,. Only the inversion recovery technique, which is the one most commonly used, will be described here. A 180° pulse is first applied which causes the magnetization along the z-axis to invert to the — z-axis (Figure 3.28). As soon as the pulse is switched off, the magnetization vector begins to relax back along the z-axis by the spin-lattice relaxation processes (Figure... 

Inversion-Recovery Technique on Purified, Partially Monotritiated Compounds... 

For measuring Ti a so-called inversion-recovery technique is often used, where the sample is subjected to sequences of 180° and 90° pulses separated by variable time t. Jeon and Kwak have employed Ti measurements using sohd state NMR to determine miscibility of P(VdF-HFP)/P(EO-EC)-based porous membranes (HFP = hexafluoropropylene), where it was assumed that a single Ti relaxation complies with the condition that... 

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