Carr-Purcell sequence

FIG. 9. Phase modulation in proton spectra of 1,1,2-trichloroethane obtained by Fourier transformation of the last half of a spin-echo obtained with 2r = 20 milliseconds. The time scale represents the duration of the Carr-Purcell sequence. From ref. 145. 

Luz and Meiboom (1963) use the equations of McConnell (1958) to solve the Carr-Purcell sequence in the presence of exchange. Certain serious approximations are required in the solution but a simple expression in closed form is derived for the fast-exchange limit. This... 

Carr-Purcell sequence (CPMG) in which all the 180° pulses in the train are phase shifted 90° with respect to the inital 90°... 

Gullion T, Baker DB, Conradi MS (1990) New, compensated Carr-Purcell sequences. J Magn Reson 89 479 84... 

F ure 2A7. Spin-echo sequences for measuring relaxation times, (a) A basic spin-echo, (b) the Carr-Purcell sequence and (c) the Carr-Purcell-Meiboom iU (CPMG) sequence. 

In the presence of radiofrequency irradiation, relaxation of magnetization aligned with the effective magnetic field is characterized by the time constant Tip. On the other hand, the time constant T2p. characterizes the relaxation of magnetization that is perpendicular to the effective field. Michael et showed that T2p can be measured directly with Carr Purcell sequences composed of a train of adiabatic full-passage (AFP) pulses. During adiabatic rotation T2p characterizes the relaxation of the magnetization, which under adiabatic conditions remains approximately perpendicular to the time-dependent effective field. Theory is derived to describe the influence of chemical... 

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