Continuous Floquet Theory in Solid-State NMR

This article presents the application of continuous Floquet theory in solid-state NMR. Continuous Floquet theory extends traditional Floquet theory to non-continuous Hamiltonians, enabling the description of observable effects not fully captured by traditional Floquet theory due to its requirement for a periodic Hamiltonian. We present closed-form expressions for computing first and second-order effective Hamiltonians, streamlining integration with traditional Floquet theory and facilitating application in NMR experiments featuring multiple modulation frequencies. Subsequently, we show examples of the practical application of Continuous Floquet theory by investigating several solid-state NMR experiments. These examples illustrate the importance of the duration of the pulse scheme regarding the width of the resonance conditions and the near-resonance behavior.