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

Area of Science:

• Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy.
• Quantum control of spin systems.

Background:

• Adiabatic pulses are crucial for manipulating spins in solid-state NMR.
• Existing theories describe high-power and low-power regimes separately, using schemes like SHAP and S³AP.
• A unified understanding of adiabatic pulse behavior across different power regimes is lacking.

Purpose of the Study:

• To provide a complete theoretical description of frequency-swept adiabatic pulses for spin-1/2 nuclei under magic-angle spinning.
• To unify existing descriptions of adiabatic pulses in high- and low-power regimes.
• To identify and characterize a previously unrecognized intermediate power regime.

Main Methods:

• Development of a theoretical framework unifying adiabatic pulse descriptions.
• Analysis of the effective Floquet Hamiltonian in the jolting frame.
• Validation through a combination of numerical simulations and experimental data.

Main Results:

• A unified theory encompassing high-, low-, and a new intermediate-power regime for adiabatic pulses.
• Demonstration that standard (super) adiabatic factors are insufficient across all regimes.
• Identification of "hidden" adiabaticity in low-power pulses, explaining their effectiveness.

Conclusions:

• The new theoretical framework provides a comprehensive understanding of adiabatic pulses in solid-state NMR.
• Existing performance benchmarks require revision, especially for low-power and rotary resonance conditions.
• Refined practical recommendations for experimentalists using adiabatic pulses are provided.