PMC

A comparison of ¹³C CPMAS spectra of U-¹³C, ¹⁵N-labeled L-Ala obtained under UFMAS at 100 kHz in a high static magnetic field at 17.6 T using (a) a low-power WALTZ-16 decoupling, (b) a cw low-power decoupling, and (c) no decoupling. The decoupling field strength was 5 kHz in (a–b). Even by averaging under UFMAS at 100 kHz, there is notable broadening for protonated carbons in (c).

The flow chart of the whole decoupling process.

The static calibration experiment setup.

(a) ³¹P NMR spectra of the CDA phantom recorded at 17.6 T without (top, 8 scans) and with MAS (bottom, one scan) at a spinning frequency of 10 kHz. The asterisks indicate spinning sidebands. (b) ³¹P spin-echo decay curves of the CDA phantom without MAS (open blue squares) and with MAS (filled blue squares) at a spinning frequency of 10 kHz. The MAS spin echo decay curves obtained applying ¹H CW or ¹H SPINAL64 decoupling (¹H RF-field strength of 100 kHz) during the echo time are shown as filled orange circles and filled green triangles, respectively. The black lines correspond to best fits of experimental data with single exponential decay functions. The corresponding T₂’ values are 15, 20 and 26.7 ms, without ¹H decoupling, with CW and with SPINAL64 decoupling, respectively. The insert shows a zoom of the ³¹P spin echo decay under static conditions without ¹H decoupling (open blue squares), and with CW (open orange circles) or SPINAL64 decoupling (open green triangles).