Heteronuclear decoupling under fast MAS by a rotor-synchronized Hahn-echo pulse train.
A new heteronuclear decoupling mechanism under fast magic-angle spinning MAS is introduced. It is based on refocusing the coherences responsible for the dephase of low-gamma nuclei ((13)C, (15)N) transverse spin-polarization in the presence of strongly dipolar-coupled protons, and has the advantage that can be implemented by pulsed techniques, with all the benefits resulting from a reduced duty cycle compared with conventional decoupling by continuous rf irradiation. The decoupling efficiency of a simple rotor-synchronized Hahn-echo pulse train is analyzed both theoretically and experimentally. It was found that a substantial improvement in sensitivity and resolution can be achieved in compounds with small (1)H chemical shielding parameters even at moderate sample spinning, and some interesting applications are shown. It is also shown that much faster spinning frequencies, or alternative refocusing sequences, are needed for applications on rigid organic solids, i.e., in systems with larger (1)H chemical shifts.
Filip
Xenia
X
National Institute for R&D of Isotopic and Molecular Technologies, P.O. Box 700, 400293 Cluj, Romania.
Tripon
Carmen
C
Filip
Claudiu
C
D000465:Algorithms; D003198:Computer Simulation; D008956:Models, Chemical; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D011522:Protons; D012815:Signal Processing, Computer-Assisted; D013113:Spin Labels
D011522:Protons; D013113:Spin Labels