Hahn echo pulse sequence

Figure 25 H-decoupled 31P NMR powder spectra of DMPC MLV samples as a function of concentration and pH with sorbic acid at (A) pH 4.4 and (B) 7.4 with decanoic acid at (C) pH 4.4 and (D) 7.4, obtained using a Hahn-echo pulse sequence under static condition at 35 °C.The concentrations of the weak acids are 0 (in black), 5 (in light grey) and 10 (in grey) mol %, respectively. Taken from Ref. [101].

B) for the solution blend containing 60 voI% of the same Aerosil (336 phr) [12] FID is measured by Hahn-echo pulse sequence... 

Liquid-state NMR spectra were obtained over an Avance 300 spectrometer. For the data acquisition, a standard Hahn-Echo pulse sequence has been used in concentric... 

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. 

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... 

When using the temperature dependence of the nuclear spin-spin or nuclear spin-lattice relaxation rate to study molecular motion, as is the case with the surface diffusion we are dealing with here, there exist soolled strong and weak collision limits. Different mathematical relationships are needed to describe these limits. Consider the nuclear spin-spin relaxation rate (1 / T2) as measured by a conventional Hahn-echo pulse sequence, and suppose that Aa> is the amplitude of the local field fluctuation responsible for relaxation. Also assume that r is the correlation time for the motion, say a jump, which causes the local field to fluctuate. The strong collision limit is defined such that... 

Basic static Ti SSNMR experiments are performed using a one-pulse or a Hahn-echo pulse sequence. Both experiments employ short-duration rectangular pulses (Fig. 4A and B), which are associated with a finite excitation bandwidth in the frequency domain. In many cases, the... 

Figure 6 The static SSNMR spectra of MgTiOs at a magnetic field of 14.1 T are pictured. The spectrum in (A) was acquired using a Hahn-echo pulse sequence, while that in (B) was acquired using the QCPMG pulse sequence and Fourier transformed. In (C), the individual echoes in the QCPMG FID were coadded together and then Fourier transformed to obtain a smooth powder pattern. In (D), a simulation of the spectra is shown. These spectra are referenced with respect to SrTiOs (see Table 1 and main text). Reprinted with permission from Ref. [49]. Copyright 2002 American Chemical Society.

H MAS spectra are usually registered with a rotor-synchronized Hahn-echo pulse sequence. The principle of Hahn-echo pulse sequence is demonstrated in Fig. 5A. With this sequence, the signal of echo is registered after evolution and refocusing periods at the time 2r equal to an even number n of rotation periods (r = n ). This manner of the spectrum recording is... 

Determination of the quantity of the Bronsted acid sites for zeolite H-ZSM-5 (Si/AI = 13) from the MAS NMR spectrum with the use of adsorbed methane as an internal reference. 200 imol/g of methane was adsorbed in the sample. (A) MAS NMR spectrum of H-ZSM-5 zeolite with adsorbed methane. (B) Deconvolution of the spectrum into separate lines for the calculation of relative signal intensities. The spectrum was recorded using the Hahn-echo pulse sequence (Fig. 5A) and repetition time t= 60s. Asterisks ( ) belong to the spinning sidebands. 

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