The Carbon-13 Intensity Problem: Elimination of the Overhauser Effect with an Added Paramagnetic Species

摘要

The spectral simplification and increase in effective S/n produced by proton 'decoupling' in 13C NMR spectroscopy is frequently accompainied by signal enhancement due to the operation of a 13C-1H Overhauser effect. The magnitude of the Overhauser enhancement ordinarily differs for different 13C nuclei so the simple relationship between resonance intensity and the number of 13C nuclei no longer holds. A theoretical analysis showing that the Overhauser effect should indeed be reduced by paramagnetic species is presented and the criteria which govern the extent of the reduction are included. The existence of such reduction has been confirmed experimentally. (Author)