title: Relative merits of rCW(A) and XiX heteronuclear spin decoupling in solid-state magic-angle-spinning NMR spectroscopy: A bimodal Floquet analysis.
abstract: We present a bimodal Floquet analysis of the recently introduced refocused continuous wave (rCW) solid-state NMR heteronuclear dipolar decoupling method and compare it with the similar looking X-inverse X (XiX) scheme. The description is formulated in the rf interaction frame and is valid for both finite and ideal π pulse rCW irradiation that forms the refocusing element in the rCW scheme. The effective heteronuclear dipolar coupling Hamiltonian up to first order is described. The analysis delineates the difference between the two sequences to different orders of their Hamiltonians for both diagonal and off-diagonal parts. All the resonance conditions observed in experiments and simulations have been characterised and their influence on residual line broadening is highlighted. The theoretical comparison substantiates the numerical simulations and experimental results to a large extent.
authors.affiliation: Center for Insoluble Protein Structures, Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University, Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark.
authors.forename: Asif
authors.initials: A
authors.lastname: Equbal
authors.affiliation: Weizmann Institute of Science, Department of Materials and Interfaces, Rehovot, Israel. Electronic address: michal.leskes@weizmann.ac.il.
authors.forename: Michal
authors.initials: M
authors.lastname: Leskes
authors.affiliation: Center for Insoluble Protein Structures, Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University, Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark. Electronic address: ncn@inano.au.dk.
authors.forename: Niels Chr
authors.initials: NC
authors.lastname: Nielsen
authors.affiliation: Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India; TIFR Centre for Interdisciplinary Sciences, 21 Brundavan Colony, Narsingi, Hyderabad 500075, India. Electronic address: madhu@tifr.res.in.
authors.forename: P K
authors.initials: PK
authors.lastname: Madhu
authors.affiliation: Weizmann Institute of Science, Department of Chemical Physics, Rehovot, Israel. Electronic address: Shimon.Vega@weizmann.ac.il.
authors.forename: Shimon
authors.initials: S
authors.lastname: Vega
keywords: Bimodal Floquet theory; Heteronuclear dipolar decoupling; Magic-angle spinning; Non-rotor-synchronisation; Solid-state NMR; XiX decoupling; rCW decoupling