  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.
