- K. Saalwächter, R. Graf, H. W. Spiess.
Recoupled Polarization Transfer
Heteronuclear Multiple-Quantum Correlation
in Solids under Ultra-fast MAS.
J. Magn. Reson.
140, 471-476 (1999).
A new approach for high-resolution solid-state heteronuclear multiple-quantum
MAS NMR spectroscopy of dipolar-coupled spin-1/2 nuclei is introduced. The
method is a heteronuclear chemical shift correlation technique of abundant
spins, like 1H with rare spins, like 13C in natural abundance. High resolution is provided by
ultra-fast MAS and high magnetic fields, high sensitivity being ensured by a
direct polarization transfer from the abundant protons to 13C. In a rotor-synchronized variant, the method can be
used to probe heteronuclear through-space proximities, while the heteronuclear
dipolar coupling constant can quantitatively be determined by measuring
multiple-quantum spinning-sideband patterns. By means of recoupling, even weak
heteronuclear dipolar interactions are accessible. The capabilities of the
technique are demonstrated by measurements on crystalline L-tyrosine hydrochloride salt.