Hahn-echo spectrum

Figure 2.13 H MAS NMR Hahn-echo spectrum of zeolite HBEA. (a) Experimental spectrum and (b) decomposition of the spectrum into six individual lines. The signals at 5.1 and 4.0 ppm are assigned to bridging Ai(0H)Si hydroxyls, the signal at 2.7 ppm, to AlOH groups and the signals at 2.1 and 1.8 ppm, to silanol groups. Reproduced from Ref. (58).

Fig. 58. Stilbite. (a) 1-D static, one-pulse O NMR spectrum of the original enriched sample processed with linear prediction (b) 1-D static Hahn echo spectrum, FT of the whole echo (c) 1-D static O Hahn echo spectrum, FT from the top of the echo. cant.)...

Fig. 17. NMR spectrum obtained using a single 90° pulse without H decoupling in pure DPPC bilayers at 50 °C and 1 bar (a) and P NMR spectra obtained using a fully phase-cycled Hahn echo sequence with inversely gated H decoupling in pure DPPC bilayers at 50 °C and 1 bar in the LC phase (b), 1 kbar in the GI phase (c), 1.75 kbar in the interdigitated Gi gel phase (d), 2.5 kbar in the GII gel phase (e), 3.7 kbar in the GUI gel phase (f), and 5.1 kbar in the GX gel phase (g) (after Refs. 4, 18).

Figure 38. (left) Solid-echo 2H NMR spectra of glycerol-/ (7 = 189 K) [305]. A collapse of the solid-state spectrum is observed upon heating the corresponding time constants of the a-process are indicated, (right) Hahn-echo 31P NMR spectra of w-tricresyl phosphate (m-TCP, Tg = 210K) determined by the anisotropic chemical shift interaction [324]. 

Figure 6 111.9MHz Sn NMR spectrum of l,l-dimethyl-2,2-bis-(trimcthyl-stannyl)hydrazine (2S°C 2S% in C () recorded by the refocused INEPT pulse sequence with H decoupling and Hahn-echo (HEED) extension [20] (Hahn-echo delay 0.16 s), showing the reduced intensity of the parent line, allowing the straightforward assignment of the N satellites (marked by asterisks /(" Sn, N)=4S.SHz) and the measurement of the isotope induced shift A / N(" Sn) = —0.0365 ppm...

Spectra with the form of the two terms on the right-hand side of Eq. (18) can be obtained by two extra modulation periods of length t in the exchange pulse sequence, one before and one after rm. The sine.sine and cosine.cosine terms of Eq. (18) are selected by suitable choices of the phases of the flip back pulses, labelled a and b in Fig. 38. The spectrum of the form of Eq. (18) is produced by the pulse sequence in Fig. 38(a), for non-spinning samples, while the spectrum of the form 1/2 S is produced using the sequence of Fig. 38(b), which matches that in Fig. 38(a) in terms of pulses and delays and so should produce a matched intensity spectrum, so that when the relevant spectra from the pulse sequence in Fig. 38(a) are subtracted from it, the desired pure-exchange spectrum is obtained. The A periods in both sequences are simply Hahn echoes, implemented to achieve non-distorted powder patterns in both spectral dimensions.2... 

Hydrochloride salts have been popular materials to study, particularly in recent years, as evidenced by the reports of Bryce et al., Chapman and Bryce, and Hamaed et al. (see Figure 11 for an example). Data are summarized in Table 4. To the best of our knowledge, the first chlorine SSNMR report for a powdered hydrochloride salt appears to be that of Pines and co-workers, who studied cocaine hydrochloride in 1995. The study utilized multiple techniques to study the hydrochloride salt, including N NQR. The chlorine-35 SSNMR experiment was carried out at 7.0 T using a Hahn-echo pulse sequence, and a chlorine-35 Cq of 5.027 MHz was reported. To avoid the intensity distortions that result from a finite pulse applied to a broad line shape, a variable frequency offset approach, in which the frequency was stepped in 2 or 4 kHz increments over the entire spectral width, was used to acquire the spectrum. 

A flat basehne is obviously an important merit of a spectrum of any dimension-ahty. There are various reasons for a poor baseline. The baseline will have an offset and curvature if the signal phase at the beginning of the acquisition period or the indirect dimension is not a multiple of 90 and if the samphng delay is not adjusted to zero, i.e. = 1, or to the inverse of twice of the spectral width, i.e. tj, = l/(2sw). The Hahn echo can be used to adjust the initial samphng delay for the acquisition dimension. For the indirect dimensions in two- or higher dimensional... 

Fig. 2.27 (a) Spin-lattice time Ti, (b) phase memory time Tm, and (c) field sweep pulsed ESR measured at room temperature on an X-irradiated K2S2O6 polycrystaUine sample, (a) Ti measurement was performed using an inversion recovery pulse sequence, (b) Tm measurement was performed using a Hahn echo sequence, (c) The pulsed ESR spectrum was obtained by measuring the Hahn echo intensity as a function of the magnetic field. The data were provided by Dr. H. Gustafsson... 

The ID F spectrum (by direct polarization or rotor-synchronized Hahn-echo pulse sequence with MAS), 2D HETCOR [67] and relaxation times have demonstrated to be very useful for identifying correlations, interactions, amorphous contents in tablets or for investigating mixtures [68-71]. The 2D experiments that involve F are CPLG-HETCOR and f CP-DARR (which is based m... 

Figure 1.15 (A) Experimental and calculated Zn static Hahn echo NMR spectrum of Zn3Al2Fn2[HAmTAZ]6. (B) Representation of a cluster showing the environments of the Al + and Zn " " cations. Reprinted with permission from Ref. [31]. Copyright 2012 Royal Society of Chemistry.

Figure 5 Various static SSNMR spectrum of Y2T1207 at a magnetic field 14.1 T are shown. In (A), a static Hahn-echo was employed, and the spectrum in (B) was obtained after correcting (A) for probe response (i.e., background signal). In (C), a simulation of the Ti powder pattern is shown. For comparison of experimental methods, a static stepped-echo or point-by-point Ti SSNMR spectrum of Y2T1207 is shown. Note the differences in resolution and the overall shape of the powder pattern in (D) versus (B). These spectra are referenced with respect to SrTi03 (see Table 1 and main text). Reprinted with permission from Ref. [49]. Copyright 2002 American Chemicai Society.

Figure 8 Using a Hahn-echo sequence and a magnetic field of 9.4 T, Bastow and Whitfield were able to acquire the depicted static SSNMR spectra. The spectrum in (A) is of pure anatase Ti02, while those in (B)-(E) are of TiOj gels that had been annealed at temperatures of (B) 200 °C, (C) 500 °C, (D) 520 °C (E) 550 °C, (F) 580 °C, (G) 600 °C, and (H) 670 °C. The spectrum in (H) corresponds to that of rutile Ti02. Reprinted with permission from Ref. [107]. Copyright 1999 American Chemical Society.

Figure 15 The static Hahn-echo ss jyip spectra at 14.1 T for mixed-stoichiometry BaSrTiOs compounds are shown. In (A), the sample is BaxSri.xTiOs, where 0

Figure 3 SSNMR spectra of Cp2ZrCl2, acquired using the Hahn-echo, QCPMG, DFS/Hahn echo, DFS/QCPMG, RAPT/Hahn echo, and RAPT-QCPMG pulse sequences, under (A) static and (B) MAS conditions. The same number of transients were recorded for all experiments, but MAS experiments were acquired with 10 times fewer scans than their spin-echo counterparts, integrated intensities are located to the right of each spectrum. Reprinted with permission from Ref [45]. Copyright 2004 American Chemical Society.

Figure 6 Zr Hahn-echo SSNMR spectra of (A) BaZr03, (B) SrZrOs, (Q BajZrO/ (D) ZrSi04, (E) Z1O2 doped with 5 mol% CaO, and (F) Z1O2 doped with 4.5 mol% MgO acquired at a field of 7.05 T. All spectra were acquired under static (nonspinning) conditions, except (A), which is an MAS spectrum. Reprinted with permission from Ref. [31]. Copyright 1991 Elsevier.

Figure 7 Static SSNMR spectra of hexagonally close-packed Zr metal, acquired at a field of 9.4 T using (A) a set of stepped-echo experiments where signal intensity is plotted against transmitter frequency, and (B) a standard Hahn-echo experiment at a fixed transmitter frequency. Note the lack of broadband excitation in (B). The simulated Zr spectrum is shown in (C). Reprinted with permission from Ref. [38]. Copyright 1992 Elsevier.

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