title: Lineshape-based polarimetry of dynamically-polarized (15)N2O in solid-state mixtures.
abstract: Dynamic nuclear polarization (DNP) of (15)N2O, 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 (15)N polarization and intermolecular dipolar broadening are strongly affected by the sample's thermal history, indicating spontaneous formation of N2O clusters. In situ (15)N NMR reveals four distinct powder-pattern spectra, attributed to the chemical-shift anisotropy (CSA) tensors of the two (15)N nuclei, further split by the intramolecular dipolar coupling between their magnetic moments. (15)N 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 (15)N polarization, without a need for time-consuming referencing to a thermal-equilibrium NMR signal.
authors.affiliation: Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104, United States. kuzma@upenn.edu
authors.forename: N N
authors.initials: NN
authors.lastname: Kuzma
authors.forename: P
authors.initials: P
authors.lastname: Håkansson
authors.forename: M
authors.initials: M
authors.lastname: Pourfathi
authors.forename: R K
authors.initials: RK
authors.lastname: Ghosh
authors.forename: H
authors.initials: H
authors.lastname: Kara
authors.forename: S J
authors.initials: SJ
authors.lastname: Kadlecek
authors.forename: G
authors.initials: G
authors.lastname: Pileio
authors.forename: M H
authors.initials: MH
authors.lastname: Levitt
authors.forename: R R
authors.initials: RR
authors.lastname: Rizi
mesh_terms: D001499:Bayes Theorem; D016001:Confidence Intervals; D007202:Indicators and Reagents; D060526:Magnetic Fields; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D009587:Nitrogen Isotopes; D009609:Nitrous Oxide / Q000737:chemistry*; D015203:Reproducibility of Results; D012997:Solvents
chemical_list: D007202:Indicators and Reagents; D009587:Nitrogen Isotopes; D012997:Solvents; D009609:Nitrous Oxide
keywords: Amorphous solid; Chemical shift anisotropy; Dipolar interaction; Dynamic nuclear polarization; Magnetic resonance imaging; Molecular imaging; Nitrous oxide; Singlet state; Trityl radical