Frequency-swept adiabatic pulses for broadband solid-state MAS NMR

Carvalho, José P.Stockholms universitet,Institutionen för material- och miljökemi (MMK) (författare)

We present a complete description of frequency-swept adiabatic pulses applied to isolated spin-1/2 nuclei with a shift anisotropy in solid materials under magic-angle spinning. Our theoretical framework unifies the existing descriptions of adiabatic pulses in the high-power regime, where the radiofrequency (RF) amplitude is greater than twice the spinning frequency, and the low-power regime, where the RF power is less than the spinning frequency, and so links the short high-powered adiabatic pulse (SHAP) and single-sideband-selective adiabatic pulses (S3AP) schemes used in paramagnetic solid-state NMR. We also identify a hitherto unidentified third regime intermediate between the low- and high-power regimes, and separated from them by rotary resonance conditions. We show that the prevailing benchmark of inversion performance based on (super) adiabatic factors is only applicable in the high- and intermediate-power regimes, but fails to account both for the poor performance at rotary resonance, and the impressive inversion seen in the low-power regime. For low-power pulses, which are non-adiabatic according to this definition of (super) adiabaticity, the effective Floquet Hamiltonian in the jolting frame reveals “hidden” (super) adiabaticity. The theory is demonstrated using a combination of simulation and experiment, and is used to refine the practical recommendations for the experimentalist who wishes to use these pulses.

Pell, Andrew J.Stockholms universitet,Institutionen för material- och miljökemi (MMK),Université de Lyon, France(Swepub:su)apell (författare)
Stockholms universitetInstitutionen för material- och miljökemi (MMK) (creator_code:org_t)

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