title: Investigations of low-amplitude radio frequency pulses at and away from rotary resonance conditions for I = 5/2 nuclei.
abstract: Additional experimental evidence of rotary resonance effects for multiple-quantum coherence conversion in a spin-5/2 system is presented. Two-dimensional plots of the relative efficiency of MQ excitation and conversion are given as a function of radio frequency (rf) amplitude and pulse width. Data are presented for the excitation of five-quantum coherence (5QC), as well as for 5QC to three-quantum coherence (3QC) conversion, 5QC to IQC (the central transition coherence) conversion, and 3QC to IQC conversion. A two-fold increase in the signal-to-noise ratio is achieved by substituting low amplitude rf pulses in place of hard rf pulses for 5QC excitation and 5QC to 3QC conversion in a mixed multiple-quantum magic angle spinning (MAS) (MMQMAS) experiment. The anisotropic line shape for the low-amplitude rf pulse version of the MMQMAS experiment was observed to be distorted from the MAS line shape. The cause and implications of the distortion are discussed.
authors.affiliation: Materials Sciences Division, 1 Cyclotron Rd, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: John W
authors.initials: JW
authors.lastname: Logan
authors.forename: Jeffry T
authors.initials: JT
authors.lastname: Urban
authors.forename: Jamie D
authors.initials: JD
authors.lastname: Walls
authors.forename: Kwang Hun
authors.initials: KH
authors.lastname: Lim
authors.forename: Alexej
authors.initials: A
authors.lastname: Jerschow
authors.forename: Alexander
authors.initials: A
authors.lastname: Pines
mesh_terms: D016880:Anisotropy; D003198:Computer Simulation; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation / Q000379:methods*; D008962:Models, Theoretical; D009942:Organometallic Compounds / Q000737:chemistry*; D010422:Pentanones / Q000737:chemistry*; D011789:Quantum Theory; D011846:Radio Waves; D012399:Rotation; D012680:Sensitivity and Specificity
chemical_list: D009942:Organometallic Compounds; D010422:Pentanones; C058508:tris(acetylacetonate) aluminum(III)