Wenckebach, W.Th., A. Capozzi, S. Patel, and J.H. Ardenkjær-Larsen. “Direct Measurement of the Triple Spin Flip Rate in Dynamic Nuclear Polarization.” Journal of Magnetic Resonance 327 (June 2021): 106982.
https://doi.org/10.1016/j.jmr.2021.106982.
A previous study of the effect of Gadolinium doping on the dynamic polarization (DNP) of 13C using trityls showed that the rate at which the polarization builds up is almost independent of the Gadolinium concentration, while the electron spin–lattice relaxation rate varies over an order of magnitude. In this paper we analyze the polarization build-up in detail and show that in this case DNP is due to the cross-effect (CE) and that the build-up rate can be quantitatively interpreted as the rate of the triple spin flips responsible for the CE. Thus this build-up rate presents a direct measurement of this triple spin flip rate.