CAESURA: measurement of slow molecular dynamics by solid-state nuclear magnetic resonance chemical shift anisotropy modulation amplification.

An alternative magic angle spinning (MAS) exchange NMR experiment based on chemical shift anisotropy (CSA) amplification is described. The CSA amplification experiment correlates a standard MAS spectrum in the omega(2) dimension with a sideband pattern in omega(1) in which the intensities are identical to those expected for a sample spinning at some fraction 1N of the actual rate omega(r). In common with 2D-PASS, the isotropic shift appears only in the omega(2) dimension, and long acquisition times can be avoided without loss of resolution of different chemical sites. The new CSA amplification exchange experiment provides information about the time scale and geometry of molecular motions via their effect on the sideband intensities in a one-dimensional pattern. The one-dimensional patterns from different chemical sites are separated across two frequency dimensions according to the isotropic shifts.