14N Population transfers in two-dimensional 13C14N1H triple-resonance magic-angle spinning nuclear magnetic resonance spectroscopy

摘要: Abstract A two-dimensional (2D) experiment has been used to show that 14N irradiation and magic-angle spinning (MAS) results in population transfers between the Zeeman levels. This was applied a sample of N-acetyl- d,l -valine, material where asymmetric doublets resulting from 13C14N dipolar coupling are clearly resolved 13C spectrum at field 7 T for carbon atoms directly bonded nitrogen atom. The transverse magnetization allowed evolve F1 F2 dimensions, spins were irradiated during mixing period. Cross-peaks observed 2D C two peaks CH doublet. Since one peak doublet primarily ¦0〉 state other ¦ − 1〉 + states, changes levels have occurred These consequence time dependence quadrupole splitting Q under MAS conditions irradiation. Level anti-crossings occur zero-crossings Q, continuous slow change will result transfer populations different If these passages adiabatic, then system returns its original after zero-crossings. is consistent with experimental observation intensities cross-peaks greater half rotor period than full