Cross polarization with high-speed magic-angle spinning

摘要: Abstract Cross-polarization magic-angle-spinning 13 C NMR has become an important analytical method for the study of organic solids. At high field strengths, magic-angle-sample-spinning (MASS) rates required to suppress spinning sidebands can substantially dipolar couplings among abundant protons. This results in dramatic changes cross-polarization (CP) dynamics. For samples with both weak homonuclear and heteronuclear couplings, matching condition is only 1 ∼ 2 kHz wide at 10 MASS rates. The maximum CP signal a sample which fills receiver coil also rather weak, amplitude nearly same as Bloch decay signal. In addition, intensity distortions are observed spectra due resonance-offset effects. this paper it shown that if phases two RF channels simultaneously inverted many times during contact, width be broadened about 8 kHz, S magnetization doubled, significantly reduced. These useful features rapid simultaneous phase-inversion high-speed by theory result spin dynamics different than those encountered static where slower phase inversion employed.