Systematic evaluation of heteronuclear spin decoupling in solid-state NMR at the rotary-resonance conditions in the regime of fast magic-angle spinning.

Journal of magnetic resonance (San Diego, Calif. : 1997)

PubMedID: 27472380

Sharma K, Madhu PK, Agarwal V. Systematic evaluation of heteronuclear spin decoupling in solid-state NMR at the rotary-resonance conditions in the regime of fast magic-angle spinning. J Magn Reson. 2016;270136-141.
The performance of heteronuclear spin decoupling sequences in solid-state NMR severely degrades when the proton radiofrequency (RF) nutation frequencies (?1) are close to or at multiples of magic-angle spinning (MAS) frequency (?r) that are referred to as rotary-resonance recoupling conditions (?1=n·?r). Recently, two schemes, namely, PISSARRO and rCW(ApA), have been shown to be less affected by the problem of MAS and RF interference, specifically at the n=2 rotary-resonance recoupling condition, especially in the fast MAS regime. Here, we systematically evaluate the loss in intensity of several heteronuclear spin decoupling sequences at the n=1, 2 conditions compared to high-power decoupling in the fast-MAS regime. We propose that in the fast-MAS regime (above 40kHz) the entire discussion about RF and MAS interference can be avoided by using appropriate low-power decoupling sequences which give comparable performance to decoupling sequences with high-power (1)H irradiation of ca. 195kHz.