Nuclear magnetic resonance hyperpolarization

L. Prydman, D. Blazina, Ultrafast two-dimensional nuclear magnetic resonance spectroscopy of hyperpolarized solutions, Nat. Phys. 3 (6) (2007) 415—419. http //dx.doi. org/10.1038/ nphys597. 

Rg. 7 Energy levels and transitions of the P neutral donor (D ), donor bound exciton (D°X), and ionized donor (D" ) from Ref. 42. (a) The Zeeman splittings of the (D ) and (D°X) states are shown from magnetic field B = 0 to B = 84.53 mT, along with the dipole-allowed optical transitions, (b) Photoconductive readout spectrum without any DO hyperpolarization, (c) The specific optical transitions (lines 4, 5, and 6) and nuclear magnetic resonance transitions (RF, RF, and RF+) used to hyperpolarize, manipulate, and read out the nuclear spins, (d) Sketches of the spins and charge densities of D+, D° and D°X. From K. Saeedi etal.. Science, 2013,342, 830. Reprinted with permission from AAAS. 

A major limitation for NMR spectroscopy is the intrinsically low sensitivity due to the rather unfavorable Boltzmann distribution for nuclear spins at thermal equilibrium. Thus, considerable effort in magnetic resonance spectroscopy is made towards sensitivity enhancement by hyperpolarization techniques, such as optical polarization, para-hydrogen-induced polarization enhancement, and dynamic nuclear polarization (DNP), a method which exploits the magnetization of unpaired electrons in stable radicals or transition metals to enhance nuclear polarization beyond the Boltzmann limit. In the chapter Dynamic Nuclear Hyperpolarization in Liquids, the fundamental theory for different polarization transfer... 

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