Principles of the NMR experiments

Detailed information on molecular dynamics can be obtained from the determination of the magnetic relaxation times Tu T, and T2. The magnetic relaxation in organic materials usually originates from modulation of dipolar proton-proton couplings, and therefore reflects the dynamics of the internuclear proton-proton vectors. To make an eflTective 

The second moment of the dipolar-broadened NMR spectrum can be used as an alternative parameter for T2. It is in principle invariant with respect to nuclear motion in a solid, provided the statistical distribution of the spins remains unaltered. However, as the rate of motion increases with temperature, the spectrum narrows in the centre and wide skirts develop which become too weak for observation. In practice, therefore, the second moments of the recorded spectra decrease with increase in temperature. 

High-resolution solid-state NMR, which allows the observation of one signal per magnetically non-equivalent carbon, makes it possible to 

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