Exploring various modulation-sideband recoupling conditions of SHA+ sequence at fast MAS

Abstract

We explore modulation-sideband recoupling conditions of the (13)C-(13)C Second-order Hamiltonian among Analogous nuclei plus pulse sequence (SHA+), and found that this sequence can be used in two different recoupling regimes. The first regime, νR>Δνiso(max), is recommended for broad-band recoupling to avoid any rotational resonance broadening. In this regime, the spinning speed should be only slightly larger than Δνiso(max), to obtain the best transfer efficiency. The second regime, νR<Δνiso(max), can be used to observe long-range constraints with lower spinning speed, which increases the transfer efficiency, and may allow using bigger rotors to increase the S/N ratio.

Keywords: Bio-molecules; Fast MAS; Homo-nuclear correlation; Modulation sidebands; Solid-state NMR.