Enhanced triple-quantum excitation in 13C magic-angle spinning NMR.
We describe a new method for exciting triple-quantum coherences in 13C-labelled powder samples under MAS. The proposed method combines selective double-quantum excitation with rotational resonance and frequency-selective composite pulses. The spin dynamics of this new method are described theoretically. Numerical calculations of the spin dynamics are compared to experimental results on fully 13C-labelled L-alanine. The observed triple-quantum filtering efficiency is around 10% for the most intense spectral peak. The method is also demonstrated on other fully 13C-labelled compounds, including a uniformly 13C-labelled amino acid.
Carravetta
Marina
M
Physical Chemistry Division, Stockholm University, S-106 91, Sweden.
Schmedt auf der Günne
Jörn
J
Levitt
Malcolm H
MH
D000409:Alanine / Q000737:chemistry*; D002247:Carbon Isotopes; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D015394:Molecular Structure
D002247:Carbon Isotopes; D000409:Alanine