Adiabatic J Cross Polarization with and without Localization
Abstract
A theoretical description of heteronuclear adiabatic J cross polarization is presented. The principle of the technique is level-crossing in the rotating frames. Suitable adiabaticity conditions are derived. The transferred polarization for isolated IS spin- {1}/{2} pairs have been treated for different preparation procedures. The objectives are to achieve (i) J cross polarization insensitive to the Hartmann/Hahn mismatch, and (ii) volume-selective J cross polarization in the presence of a gradient of the main magnetic field. The dependence of the transferred polarization on the sweep time is specified, as well as the covered range of coupling constants J and the permitted degree of off-resonance excitation. The theory is discussed in comparison with experimental 13C 1H and 15N 1H data. The formalism also applies to the case when a magnetic fields gradient is present. Cross polarization then becomes slice selective and can be used for localized spectroscopy (AJCP-LOSY). The theoretical slice profile is in good agreement with experimental data recorded with formic acid. Applications of this principle for direct or proton-detected 13C localized spectroscopy or imaging are discussed.
- Publication:
-
Journal of Magnetic Resonance
- Pub Date:
- 1994
- DOI:
- 10.1006/jmra.1994.1199
- Bibcode:
- 1994JMagR.110..136D