Carr-Purcell-Meiboom-Gill pulse sequence

CPMG pulse sequence Carr-Purcell-Meiboom-Gill pulse sequence. A pulse sequence used for removing broad signals from a spectrum by multiple defocusing and refocusing pulses. 

In electron spin echo relaxation studies, the two-pulse echo amplitude, as a fiinction of tire pulse separation time T, gives a measure of the phase memory relaxation time from which can be extracted if Jj-effects are taken into consideration. Problems may arise from spectral diflfrision due to incomplete excitation of the EPR spectrum. In this case some of the transverse magnetization may leak into adjacent parts of the spectrum that have not been excited by the MW pulses. Spectral diflfrision effects can be suppressed by using the Carr-Purcell-Meiboom-Gill pulse sequence, which is also well known in NMR. The experiment involves using a sequence of n-pulses separated by 2r and can be denoted as [7i/2-(x-7i-T-echo) J. A series of echoes separated by lx is generated and the decay in their amplitudes is characterized by Ty. ... 

Measurement of a true T2 can be obtained using a spin-echo pulse sequence, such as the Carr-Purcell-Meiboom-Gill (CPMG) sequence, which minimizes the loss of phase coherence caused by inhomogeneities (Kemp, 1986). 

T2 measurements usually employ either Carr-Purcell-Meiboom-Gill (CPMG) [7, 8] spin-echo pulse sequences or experiments that measure spin relaxation (Tlp) in the rotating frame. The time delay between successive 180° pulses in the CPMG pulse sequence is typically set to 1 ms or shorter to minimize the effects of evolution under the heteronuc-lear scalar coupling between 1H and 15N spins [3]. 

Figure 10.7 Carr-Purcell-Meiboom Gill (CPMC) sequence and NMR signal. (A) CPMC pulse sequence, (B) CPMC decay signal, and (C) Laplace inversion of the CPMC decay signal.

Spin-spin relaxation times T2 are determined by the Carr-Purcell-Meiboom-Gill spin echo pulse sequence and provide information about slower molecular motions (66,67). 

Values of the spin-spin relaxation-time (Tz) for individual spectral lines may be measured by Fourier transformation of the echoes produced by a Carr-Purcell-Meiboom-Gill type of pulse sequence,174 but only in a simple manner, if there is no homonuclear spin-coupling present.175 Refocusing of the dispersing magnetization-vector by... 

ID, one-dimensional 2D, two-dimensional 3D, three-dimensional AMP, adenosine monophosphate CNDO, complete neglect of differential overlap COSY, correlation spectroscopy CPMG, Carr-Purcell-Meiboom-Gill NMR pulse sequence CT, constant time dAMP, deoxyadenosine monophosphate DFT, density functional... 

The T2 of the mobile phase is determined by a Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence in that work. Based on an easily accessible NMR parameter, i.e., T2, the above empirical correlation, which is claimed by the... 

When NMR was performed the media hydrated with 1 1 H20 D20 were packed in 10 mm NMR tubes to reach a sample height of 8 to 10 mm. A 90° pulse WALTZ sequence was used with acquisition parameters 7.45 to 780 /AS pulse width, 1500 to 20,000 Hz pulse width, 0.012 to 0.166 sec acquisition time and recycle delay > 5Ti. Spin-spin relaxation time (T2) was determined with a Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence with interpulsed spacing (t) ranging from 5 to 500 ms. At least eight different T values were used for each T2 determination. 

NMR molecular mobility Relaxation times ( H NMR Ti and T2) determination was carried out with a Bruker Avance 300 Spectrometer (Bruker Instruments, Billerica, MA, USA). Samples were packed into 5-mm diameter NMR tubes. Ti was measured using an inversion recovery (Derome, 1987) and T2 with a Carr Purcell Meiboom Gill (CPMG Carr and Purcell, 1954 Meiboom and Gill, 1958) pulse sequences. All data were best fit with mono-exponential relaxation with > 0.99 in all samples. 

Phase considerations intrude even in the simplest experiments of observing an FID or an echo. Accurately adjusting the phases of rf pulses can be very important, particularly in experiments involving trains of pulses such as the Carr-Purcell Meiboom-Gill train or the multiple pulse line narrowing sequences. In other sections we have considered how phase shifts originate and how to cope with them. 

NMR studies of metals in sohd state non-metallic materials such as zeolites, inorganic complexes, glasses, coals, polymers, metalloproteins, and RNA have been reviewed. The role of solid state NMR spectroscopy in investigating the structural and functional aspects of these materials with no long range order is evaluated. This overview presents several developments of solid state NMR to the study of a variety of metal containing materials. In particular, the use of the quadrupolar Carr-Purcell-Meiboom-Gill pulse sequence for the acquisition of solid state NMR spectra of quadrupolar nuclei with low natural abundances and low NMR frequencies, and applications of solid state Cd NMR are covered in detail. 

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