title: Decoupling and recoupling using continuous-wave irradiation in magic-angle-spinning solid-state NMR: a unified description using bimodal Floquet theory.
abstract: The application of two or more different time-dependent coherent perturbations with, in general, incommensurable frequencies occurs quite commonly in NMR experiments. Here we develop a unified description of the entire class of experiments using bimodal Floquet theory and van Vleck-Primas perturbation theory. This treatment leads to a time-independent effective Hamiltonian in Hilbert space and can be looked at as a generalization of average Hamiltonian theory to several incommensurate time dependencies. As a prototype experiment we treat the application of continuous-wave (cw) radio-frequency irradiation in combination with magic-angle sample spinning. Practically relevant examples of this type of experiments are heteronuclear spin decoupling and recoupling experiments using cw irradiation, e.g., rotary-resonance recoupling. Perturbations up to the third order must be taken into account to explain all experimentally observed resonance conditions.
authors.affiliation: Physical Chemistry, Eidgenössische Technische Hochschule (ETH) Zurich, CH-8093 Zürich, Switzerland. maer@nmr.phys.chem.ethz.ch
authors.forename: Matthias
authors.initials: M
authors.lastname: Ernst
authors.forename: Ago
authors.initials: A
authors.lastname: Samoson
authors.forename: Beat H
authors.initials: BH
authors.lastname: Meier