Design and application of robust rf pulses for toroid cavity NMR spectroscopy

Thomas E. Skinner, Michael Braun, Klaus Woelk, Naum I. Gershenzon, Steffen J. Glaser

Research output: Contribution to journalArticlepeer-review

18 Scopus citations

Abstract

We present robust radio frequency (rf) pulses that tolerate a factor of six inhomogeneity in the B1 field, significantly enhancing the potential of toroid cavity resonators for NMR spectroscopic applications. Both point-to-point (PP) and unitary rotation (UR) pulses were optimized for excitation, inversion, and refocusing using the gradient ascent pulse engineering (GRAPE) algorithm based on optimal control theory. In addition, the optimized parameterization (OP) algorithm applied to the adiabatic BIR-4 UR pulse scheme enabled ultra-short (50 μs) pulses with acceptable performance compared to standard implementations. OP also discovered a new class of non-adiabatic pulse shapes with improved performance within the BIR-4 framework. However, none of the OP-BIR4 pulses are competitive with the more generally optimized UR pulses. The advantages of the new pulses are demonstrated in simulations and experiments. In particular, the DQF COSY result presented here represents the first implementation of 2D NMR spectroscopy using a toroid probe.

Original languageEnglish
Pages (from-to)282-290
Number of pages9
JournalJournal of Magnetic Resonance
Volume209
Issue number2
DOIs
StatePublished - Apr 2011

Keywords

  • B inhomogeneity
  • Composite pulses
  • GRAPE algorithm
  • OP algorithm
  • Optimal control theory
  • Shaped pulses
  • Toroid NMR

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