Lineshape-based polarimetry of dynamically-polarized in solid-state mixtures

Kuzma, N.N., Hakansson, Par, Pourfathi, M., Ghosh, R.K., Kara, H., Kadlecek, S.J., Pileio, Giuseppe, Levitt, M.H. and Rizi, R.R. (2013) Lineshape-based polarimetry of dynamically-polarized in solid-state mixtures. Journal of Magnetic Resonance, 234, 90-94. (doi:10.1016/j.jmr.2013.06.008).

Abstract

Dynamic nuclear polarization (DNP) of 15N2O, known for its long-lived singlet-state order at low magnetic field, is demonstrated in organic solvent/trityl mixtures at ?1.5 K and 5 T. Both 15N polarization and intermolecular dipolar broadening are strongly affected by the sample’s thermal history, indicating spontaneous formation of N2O clusters. In situ 15N NMR reveals four distinct powder-pattern spectra, attributed to the chemical-shift anisotropy (CSA) tensors of the two 15N nuclei, further split by the intramolecular dipolar coupling between their magnetic moments. 15N polarization is estimated by fitting the free-induction decay (FID) signals to the analytical model of four single-quantum transitions. This analysis implies (10.2±2.2)% polarization after 37 h of DNP, and provides a direct, instantaneous probe of the absolute 15N polarization, without a need for time-consuming referencing to a thermal-equilibrium NMR signal

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Contributors

Author: Giuseppe Pileio

Author: M.H. Levitt

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