@article {2581, title = {Optically-pumped dynamic nuclear hyperpolarization in 13C enriched diamond}, journal = {Phys. Rev. B Rapid Communications}, year = {2018}, abstract = {
We investigate nuclear spin hyperpolarization from optically polarized nitrogen vacancy centers in isotopically enriched diamonds with 13C concentrations up to 100\%.\ 13C enrichment leads to hyperfine structure of the nitrogen vacancy electron spin resonance spectrum and dynamic nuclear polarization enhancement profile. We show that strongly-coupled \cthirt spins in the first shell surrounding a nitrogen vacancy center generate resolved hyperfine splittings, but do not act as an intermediary in the transfer of hyperpolarization of bulk nuclear spins. High levels of \cthirt enrichment are desirable to increase the efficiency of hyperpolarization for magnetic resonance signal enhancement, imaging contrast agents, and as a platform for quantum sensing and many-body physics.
}, url = {https://journals.aps.org/prb/accepted/0707cOeaT9fE2916845f0be02a174d447e77534ff}, author = {Parker, AJ and Jeong, K and Avalos, CE and Hausmann, BJM and Vassiliou, CC and Pines, A and King, JP} } @article {2979, title = {Orientation independent room-temperature optical 13C hyperpolarization in powdered diamond}, journal = {Science Advances}, volume = {4}, year = {2018}, month = {05/2018}, abstract = {Dynamic nuclear polarization via contact with electronic spins has emerged as an attractive route to enhance the sensitivity of nuclear magnetic resonance beyond the traditional limits imposed by magnetic field strength and temperature. Among the various alternative implementations, the use of nitrogen vacancy (NV) centers in diamond\—a paramagnetic point defect whose spin can be optically polarized at room temperature\—has attracted widespread attention, but applications have been hampered by the need to align the NV axis with the external magnetic field. We overcome this hurdle through the combined use of continuous optical illumination and a microwave sweep over a broad frequency range. As a proof of principle, we demonstrate our approach using powdered diamond with which we attain bulk 13C spin polarization in excess of 0.25\% under ambient conditions. Remarkably, our technique acts efficiently on diamond crystals of all orientations and polarizes nuclear spins with a sign that depends exclusively on the direction of the microwave sweep. Our work paves the way toward the use of hyperpolarized diamond particles as imaging contrast agents for biosensing and, ultimately, for the hyperpolarization
of nuclear spins in arbitrary liquids brought in contact with their surface.
Scalar couplings of the form JI(1) . I(2) between nuclei impart valuable information about molecular structure to nuclear magnetic-resonance spectra. Here we demonstrate direct detection of J-spectra due to both heteronuclear and homonuclear J-coupling in a zero-field environment where the Zeeman interaction is completely absent. We show that characteristic functional groups exhibit distinct spectra with straightforward interpretation for chemical identification. Detection is performed with a microfabricated optical atomic magnetometer, providing high sensitivity to samples of microliter volumes. We obtain 0.1 Hz linewidths and measure scalar-coupling parameters with 4-mHz statistical uncertainty. We anticipate that the technique described here will provide a new modality for high-precision\" J spectroscopy\" using small samples oil microchip devices for multiplexed Screening, assaying, and sample identification in chemistry and biomedicine. (C) 2009 Elsevier Inc. All rights reserved.
}, keywords = {cells}, isbn = {1090-7807}, doi = {Doi 10.1016/J.Jmr.2009.03.008}, url = {Hyperpolarized Xe-129 NMR spectroscopy can detect the presence of specific low-concentration biomolecular analytes by means of a xenon biosensor that consists of a water-soluble, targeted cryptophane-A cage that encapsulates the xenon. In this work, we use the prototypical biotinylated xenon biosensor to determine the relationship between the molecular composition of the xenon biosensor and the characteristics of protein-bound resonances. The effects of diastereomer overlap, dipole-dipole coupling, chemical-shift anisotropy, xenon exchange, and biosensor conformotional exchange on the protein-bound biosensor signal were assessed. It was found that an optimal protein-bound biosensor signal can be obtained by minimizing the number of biosensor diastereomers and using a flexible linker of appropriate length. Both the line width and sensitivity of chemical shift to protein binding of the xenon biosensor were found to be inversely proportional to linker length.
}, keywords = {complexes}, isbn = {1439-4227}, doi = {Doi 10.1002/Cbic.200500327}, url = {By applying magnetic field gradients to alkali vapor cells, images of the spatial distribution of spin-polarized Rb atoms were obtained. Optical pumping is used to produce precessing spin-polarization in the ground state. Detection of the coherent spin transients is performed in the time-domain by a single optical probe beam covering the whole sample cell. Spatial resolution of better than 1 mm has been achieved by a projection-reconstruction method.
}, keywords = {xe-129}, isbn = {0375-9601}, doi = {Doi 10.1016/S0375-9601(96)00927-9}, url = {The orientation and motion of tetrahydrofuran (THF) in the ternary graphite intercalation compounds Cs-(THF)(1.3)C-24 and K(THF)(2.5)C-24 have been studied by proton NMR. Simulations of the NMR spectra indicate that the THF molecules in CS(THF)(1.3)C-24 have their mean planes oriented parallel to the layers of the host lattice, while the THF molecules in K(THF)(2.5)C-24 have their mean planes oriented at an angle between 50 degrees and 75 degrees from the graphite layers. The proton NMR spectra of both compounds show evidence that the THF molecules rotate about the normal to the graphite layers and confirm X-ray diffraction studies showing a degree of orientational disorder in the samples, corresponding to a mosaic spread in the graphite layer orientation. The conformation of the intercalated THF was studied by simulating the experimental NMR spectra using models for the conformational motion of THF. Simulations indicate that the conformation of intercalated THF is different than gas or liquid phase THF, which has been found to have a ring puckering amplitude of 0.38-0.44 Angstrom and to undergo nearly free pseudorotation through a series of conformations. Best agreement between simulated and experimental NMR spectra of Cs(THF)(1.3)C-24 was Obtained with THF interconverting between two conformations of C-s symmetry and a puckering amplitude of 0.30 Angstrom. Free or slightly hindered pseudorotation of THF (observed in liquid or gaseous THF) in this compound produces simulated spectra that differ significantly from the experimental spectra. Simulated proton NMR spectra of K(THF)(2.5)C-24 using conformations of C-s symmetry or free or slightly hindered pseudorotation of THF do not fit the experimental spectra sufficiently well to allow distinction between the conformational motions or to exclude other possible motions.
}, keywords = {system}, isbn = {0022-3654}, doi = {Doi 10.1021/J100026a020}, url = {