Longitudinal relaxation processes

There are two relaxation processes. The spin-lattice or longitudinal relaxation process, designated by... 

In summary, then, all relaxation processes can ultimately be described as some linear combination of such spectral density functions. We have here only explicitly considered longitudinal relaxation processes in the laboratory frame, but a similar case can be made for transverse relaxation, relaxation processes in the rotating frame and cross-relaxation processes. The spectral densities... 

However, the division into transverse and longitudinal relaxation processes reflects the anisotropy of structure and local interactions that actually exists in chains and becomes apparent in various phenomena. 

If a 0, we have the noninertial response. This is treated by Shliomis and Stepanov [9], who were able to factorize the joint distribution of the dipole and easy axis orientations in the Fokker Planck equation into the product of the two separate distributions. Thus as far as the internal relaxation process is concerned, the axially symmetric treatment of Brown [50] applies. Hence no intrinsic coupling between the transverse and longitudinal modes exists that is, the eigenvalues of the longitudinal relaxation process are independent of a. The distribution function of the easy axis orientations n is simply that of a free Brownian rotator excluding inertial effects. 

Some difficulties in interpretation have been encountered due to the existence of complex decay in transverse relaxation but simple decay in longitudinal relaxation. More recent experiments have shown that longitudinal relaxation processes are also complex when accurate measurements are made (10). 

Figure 3.153 In a typical NMR experiment, when an ensemble of protons is placed in an external magnetic field Bo, a net magnetization along Bo is caused. After applying a 90° RF pulse, the net magnetization is flipped to the xy plane. The longitudinal relaxation process T )...

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