Dynamic nuclear polarization via the cross effect and thermal mixing: B. Energy transport #DNPNMR

Wenckebach, W.Th. “Dynamic Nuclear Polarization via the Cross Effect and Thermal Mixing: B. Energy Transport.” Journal of Magnetic Resonance 299 (February 2019): 151–67.


The fundamental process of dynamic nuclear polarization (DNP) via the cross effect (CE) and thermal mixing (TM) is a triple spin flip, in which two interacting electron spins and a nuclear spin interacting with one of these electron spins flip together. In the previous article (Wenckebach, 2018) these triple spin flips were treated by first determining the eigenstates of the two interacting electron spins exactly and next investigating transitions involving these exact eigenstates and the nuclear spin states. It was found that two previously developed approaches—the scrambled states approach and the fluctuating field approach—are just two distinct limiting cases of this more general approach. It was also shown that triple spin flips constitute a single process causing two flows of energy: a flow originating in the electron Zeeman energy and a flow originating in the mutual interactions between the electron spins. In order to render their definitions more precise, the former flow was denoted as the CE and the latter as TM.

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