title: Frequency offset refocused PISEMA-type sequences.
abstract: The popular PISEMA experiment is highly sensitive to the 1H chemical shift dispersion and the choice of the 1H carrier frequency. This is due to the off-resonance 1H irradiation in the FSLG-CP sequence employed during the dipolar evolution period. In the modified approach described in this work, the interfering frequency offset terms are suppressed. In the new pulse schemes, conventional FSLG-CP is intercalated with 180 degrees pulses applied simultaneously to both frequency channels, and with phases set orthogonal to those of the spin-lock fields. The technique is demonstrated on a nematic liquid-crystalline sample. Extensions to amplitude-modulated FSLG-CP recoupling under MAS are also presented.
authors.affiliation: Division of Physical Chemistry, Arrhenius Laboratory, Stockholm University, SE-10691 Stockholm, Sweden. sergey@physc.su.se
authors.forename: Sergey V
authors.initials: SV
authors.lastname: Dvinskikh
authors.forename: Dick
authors.initials: D
authors.lastname: Sandström
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D008956:Models, Chemical; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D012815:Signal Processing, Computer-Assisted