Editing Dynamic nuclear polarization (section)

====Magic angle spinning case====
As in the static case, the MAS-DNP mechanism of cross effect is deeply modified due to the time dependent [[energy level]]. By taking a simple three spin system, it has been demonstrated that the cross-effect mechanism is different in the Static and MAS case. The cross effect is the result of very fast multi-step process involving EPR single quantum transition, electron dipolar anti-crossing and cross effect degeneracy conditions.
In the most simple case the MAS-DNP mechanism can be explained by the combination of a single quantum transition followed by the cross-effect degeneracy condition, or by the electron-dipolar anti-crossing followed by the cross-effect degeneracy condition.<ref name="Mentink-Vigier, F. Akbey, U. Hovav, Y. Vega, S. Oschkinat, H. Feintuch, A. 2012 13–21"/><ref name=tycko12>
{{cite journal
|author =Thurber, K. R. |author2=Tycko, R.
|title = Theory for cross effect dynamic nuclear polarization under magic-angle spinning in solid state nuclear magnetic resonance: the importance of level crossings
|journal = [[J. Chem. Phys.]]
|volume = 137 |pages = 084508
|year = 2012
|doi = 10.1063/1.4747449
|pmid=22938251
|issue = 8 |bibcode = 2012JChPh.137h4508T
|pmc = 3443114}}</ref>

This in turn change dramatically the CE dependence over the static magnetic field which does not scale like B<sub>0</sub><sup>−1</sup> and makes it much more efficient than the solid effect.<ref name=tycko12 />