title: Broadband adiabatic inversion pulses for cross polarization in wideline solid-state NMR spectroscopy.
abstract: Efficient acquisition of ultra-wideline solid-state NMR powder patterns is a continuing challenge. In particular, when the breadth of the powder pattern is much larger than the cross-polarization (CP) excitation bandwidth, transfer efficiencies suffer and experimental times are greatly increased. Presented herein is a CP pulse sequence with an excitation bandwidth that is up to ten times greater than that available from a conventional spin-locked CP pulse sequence. The pulse sequence, broadband adiabatic inversion CP (BRAIN-CP), makes use of the broad, uniformly large frequency profiles of chirped inversion pulses, to provide these same characteristics to the polarization transfer process. A detailed theoretical analysis is given, providing insight into the polarization transfer process involved in BRAIN-CP. Experiments on spin-1/2 nuclei including (119)Sn, (199)Hg and (195)Pt nuclei are presented, and the large bandwidth improvements possible with BRAIN-CP are demonstrated. Furthermore, it is shown that BRAIN-CP can be combined with broadband frequency-swept versions of the Carr-Purcell-Meiboom-Gill experiment (for instance with WURST-CPMG, or WCPMG for brevity); the combined BRAIN-CP/WCPMG experiment then provides multiplicative signal enhancements of both CP and multiple-echo acquisition over a broad frequency region.
authors.affiliation: Department of Chemistry, University of Windsor, Windsor, Ontario, Canada.
authors.forename: Kristopher J
authors.initials: KJ
authors.lastname: Harris
authors.forename: Adonis
authors.initials: A
authors.lastname: Lupulescu
authors.forename: Bryan E G
authors.initials: BE
authors.lastname: Lucier
authors.forename: Lucio
authors.initials: L
authors.lastname: Frydman
authors.forename: Robert W
authors.initials: RW
authors.lastname: Schurko
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008956:Models, Chemical