title: Resonator with reduced sample heating and increased homogeneity for solid-state NMR.
abstract: In the application of solid-state NMR to many systems, the presence of radiofrequency (rf) electric fields inside classical solenoidal coils causes heating of lossy samples. In particular, this is critical for proteins in ionic buffers. Rf sample heating increases proportional to frequency which may result in the need to reduce the rf pulse power to prevent partial or total sample deterioration. In the present paper, we propose a multifrequency-tunable NMR resonator where the sample is electrically shielded from the NMR coil by a conductive sheet that increases the magneto-electric ratio. Expressions for the B1 efficiency as function of magnetic and electric filling factors are derived that allow a direct comparison of different resonators. Rf efficiency, homogeneity, signal-to-noise, and rf sample heating are compared. NMR spectra at 700MHz on ethylene glycol, glycine, and a model protein were acquired to compare the resonators under realistic experimental conditions.
authors.affiliation: Bruker Biospin GmbH, Silberstreifen, D-76287 Rheinstetten, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Krahn
authors.forename: Uwe
authors.initials: U
authors.lastname: Priller
authors.forename: Lyndon
authors.initials: L
authors.lastname: Emsley
authors.forename: Frank
authors.initials: F
authors.lastname: Engelke
mesh_terms: D003198:Computer Simulation; D017076:Computer-Aided Design; D055590:Electromagnetic Phenomena / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006358:Hot Temperature; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation* / Q000379:methods; D008962:Models, Theoretical; D013048:Specimen Handling / Q000295:instrumentation* / Q000379:methods; D014159:Transducers