Carr-Purcell pulse sequences

Methods for measuring Ti and T2 are discussed in Chapter 5 of reference 21. Suffice it to say here that understanding the method for measuring T2 (the Carr-Purcell pulse sequence or spin-echo method) becomes important for discussing two-dimensional NMR spectra. When spin-spin coupling is present, a modulation of spin echoes is produced, and it is this fact that is important in 2-D NMR spectroscopy. Nuclear relaxation rates and mechanisms become important when discussing the effect of paramagnetic metal centers on NMR spectroscopy. 

Fig. 10a and b. H T pulse sequence free induction decay following a 90° pulse (a) Carr-Purcell pulse sequence (b)... 

Fig. 14. Dependence of the relaxation times T2. and the fractions of protons with different mobility (f.) for unsaturated polyester on the curing time, as measured from broad line NMR ( ), Hahn spin-echo ( ) and Carr-Purcell pulse sequence (O)- Symbol x indicates the initial distribution of styrene and unsaturated polyester protons (adapted from Ref. S5))...

CPMG Carr-Purcell pulse sequence. Meiboom-Gill modification... 

The use of the Carr-Purcell pulse sequence for T.2 has only recently been studied but it does have the advantage of the new variable, pulse separation. 

The technique for obtaining reliable values of Tj involves the application of fmlher short rf-pulses to the nuclear spin system such that spin echoes are obtained. In this review, we shall discuss briefly the Carr-Purcell pulse sequence for producing spin echoes with the modification introduced by Maiboom and Gill . After the initial 90° pulse along the x-direction in the rotating frame (cf. first section of this chapter), pulses with cc = = 180° are applied along the... 

NMR measurements were performed using a Bruker pulsed spectron ter operating at 60 MHz. The protons transverse magnetic relaxation function was analysed from spin echoes which were formed by applying Carr-Purcell pulse sequences to the spin system. 

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