Carr-Purcell-Meiboom-Gill sequence

Since the present NMR-SIM version also consider transverse relaxation as a proper process, it is possible to simulate the common T2 measurement experiment using the Carr-Purcell-Meiboom-Gill sequence. 

CPMG Carr-Purcell Meiboom-Gill sequence... 

Loria JP, Ranee M, Palmer AG (1999) A relaxation-compensated Carr-Purcell-Meiboom-Gill sequence for characterizing chemical exchange by NMR spectroscopy. J Am Chem Soc 121 2331-2332... 

The quadrupolar-echo experiment represents the most widely used experiment for the observation of quadrupolar nuclei.For half-integer nuelei, it may be tuned to observe only the central transition (1/2-1/2), which is perturbed by the quadrupolar interaction only to second order, thus allowing the observation of less dominant anisotropic interactions. A significant improvement in sensitivity can be obtained by ncorporating a spin-echo method such as the Carr-Purcell-Meiboom-Gill sequence into the detection period. " The powder line-shape splits into a manifold of sidebands, from which information on the homogeneous and inhomogeneous interactions can be extracted from the line-shape of the sidebands and their envelope, respectively. 

Maudsley, A. A. 1986. Modified Carr-Purcell-Meiboom-Gill sequence for NMR Fourier imaging applications. 

The spin-spin relaxation parameters were obtained from a combination of FID (Free Induction Decay) and CPMG (Carr-Purcell-Meiboom-Gill) Sequence. In total, 5000 pulses were applied with a pulse spacing of t = 0.05 ms. The dead time between the rf pulse excitation and the data acquisition was determined to be 9 ps. 

Spin dynamic studies, including saturation and inversion recovery, Hahn echo and stimulated echo decay, as well as Carr-Purcell-Meiboom-Gill sequences, can be performed, yielding relaxation times. When rapid reaction kinetics are being measured, information is also gained on transient phenomena such as chemically induced electron polarization (CIDEP). 

The NMR measurement consists of a series of steps called the CPMG (Carr, Purcell, Meiboom, Gill) sequence (Carr and Purcell, 1954 Meiboom and Gill, 1958) in which two magnetic fields are applied ... 

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. ... 

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. 

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... 

When a spectrum has severely broadened resonances in the presence of less broadened resonances, it is possible to use a Carr-Purcell-Meiboom-Gill spin-echo sequence to remove the broadened resonances, facilitating the interpretation of the remaining signals. By setting certain parameters of the sequence, it is possible to progressively remove peaks with less and less broadening. ... 

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... 

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