Investigations of Low-Amplitude Radio Frequency Pulses at and away from Rotary Resonance Conditions for I = 52 Nuclei
✍ Scribed by John W. Logan; Jeffry T. Urban; Jamie D. Walls; Kwang Hun Lim; Alexej Jerschow; Alexander Pines
- Publisher
- Elsevier Science
- Year
- 2002
- Tongue
- English
- Weight
- 243 KB
- Volume
- 22
- Category
- Article
- ISSN
- 0926-2040
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✦ Synopsis
Additional experimental evidence of rotary resonance effects for multiple-quantum coherence conversion in a spin-5/2 system is presented. Two-dimensional plots of the relative efficiency of MQ excitation and conversion are given as a function of radio frequency (rf) amplitude and pulse width. Data are presented for the excitation of five-quantum coherence (5QC), as well as for 5QC to three-quantum coherence (3QC) conversion, 5QC to IQC (the central transition coherence) conversion, and 3QC to IQC conversion. A two-fold increase in the signal-to-noise ratio is achieved by substituting low amplitude rf pulses in place of hard rf pulses for 5QC excitation and 5QC to 3QC conversion in a mixed multiple-quantum magic angle spinning (MAS) (MMQMAS) experiment. The anisotropic line shape for the low-amplitude rf pulse version of the MMQMAS experiment was observed to be distorted from the MAS line shape. The cause and implications of the distortion are discussed.