title: The magnetic field dependence of cross-effect dynamic nuclear polarization under magic angle spinning.
abstract: We develop a theoretical description of Dynamic Nuclear Polarization (DNP) in solids under Magic Angle Spinning (MAS) to describe the magnetic field dependence of the DNP effect. The treatment is based on an efficient scheme for numerical solution of the Liouville-von Neumann equation, which explicitly takes into account the variation of magnetic interactions during the sample spinning. The dependence of the cross-effect MAS-DNP on various parameters, such as the hyperfine interaction, electron-electron dipolar interaction, microwave field strength, and electron spin relaxation rates, is analyzed. Electron spin relaxation rates are determined by electron paramagnetic resonance measurements, and calculations are compared to experimental data. Our results suggest that the observed nuclear magnetic resonance signal enhancements provided by MAS-DNP can be explained by discriminating between "bulk" and "core" nuclei and by taking into account the slow DNP build-up rate for the bulk nuclei.
authors.affiliation: NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, 3584 CH Utrecht, The Netherlands.
authors.forename: Deni
authors.initials: D
authors.lastname: Mance
authors.affiliation: Department of Physics, Huygens-Kamerlingh Onnes Laboratory, Leiden University, PO Box 9504, 2300 RA Leiden, The Netherlands.
authors.forename: Peter
authors.initials: P
authors.lastname: Gast
authors.affiliation: Department of Physics, Huygens-Kamerlingh Onnes Laboratory, Leiden University, PO Box 9504, 2300 RA Leiden, The Netherlands.
authors.forename: Martina
authors.initials: M
authors.lastname: Huber
authors.affiliation: NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, 3584 CH Utrecht, The Netherlands.
authors.forename: Marc
authors.initials: M
authors.lastname: Baldus
authors.affiliation: International Tomography Center, Siberian Branch of the Russian Academy of Science, Institutskaya 3a, Novosibirsk 630090, Russia and Novosibirsk State University, Pirogova 2, Novosibirsk 63009, Russia.
authors.forename: Konstantin L
authors.initials: KL
authors.lastname: Ivanov