Cross-polarization dynamic processes

Third, there are clear differences in the images for dissociation at the same wavelength while probing different spin-orbit states. Two effects contribute to these differences. One is the slight difference in energy in the atomic states, most easily seen in the data at 234 nm where the 0(3P2) data clearly has the strong contribution from vibrationally-excited O2 while the other spin-orbit states do not. In this case the threshold for the dynamical process that forms the vibrationally-excited products has been crossed by the 158.265 cm-1 of the spin-orbit excitation. The second effect is that due to the nature of the J-level. It is known that there is a v—J correlation from the angular fits as well as from the fact that when the polarization of the... 

The cross-polarization (CP), i.e. the transfer of I-spin polarization to the dilute spins (S), is a double resonance experiment in which the I and S spins are coupled by a certain interaction, determined by the cross relaxation time tb. From the dynamics of the CP process, usually described with the spin temperature concept, the following equation for the time dependence of S-spin polarization could be derived ... 

Section 6 reviews developments in cross-polarization and spin diffusion/ exchange. This section is closely related to Section 4 because of the interplay between these spin dynamics processes and the recoupling schemes at highspeed spinning, which now is almost invariably used for high resolution. Actually, many recoupling techniques were motivated by effecting crosspolarization and spin diffusion under fast MAS. 

Other important examples of dynamic processes are polarization transfer rates such as cross-relaxation rate and spin diffusion rate which are discussed in the previous two subsections. 

Kupriyanov studied relaxation of spin 1/2 in the scalar coupled spin system AMX with quadrupolar nuclei in the presence of cross correlation effects. Khaneja et a/. presented optimal control of spin dynamics in the presence of relaxation. Eykyn et a/. studied selective cross-polarization in solution state NMR of scalar coupled spin 1/2 and quadrupolar nuclei. Tokatli applied the product operator theory to spin 5/2 nuclei. Mahesh et a/. used strongly coupled spins for quantum information processing. Luy and Glaser " inves-... 

Since the pioneering demonstration that cross-polarization C NMR spectra can be recorded, solid-state NMR spectroscopy has advanced rapidly and is now being used to study the structure and dynamics of a variety of polymer systems. Much of the success of solid-state NMR spectroscopy is due to the evolution of a variety of techniques for studying internuclear distances, anisotropy, torsion angles, atomic orientations, spin diffusion, molecular dynamics, and exchange processes, while maintaining the high resolution and sensitivity necessary for practically useful NMR experiments in polymers. 

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