Use of a modified DEFT pulse sequence in13C NMR: Dynamic range improvement for relaxation experiments and dynamic NMR measurements at high resolution

A modification of the DEFT pulse sequence is used for two applications in¹³C NMR spectroscopy. The first application suppresses solvent line resonances for dilute solutions. Unlike other techniques this method allows determination of solute T₁ values with concurrent solvent suppression. Requirements for this application are not overly stringent. The required T₁ ratio for effective peak suppression is ≿4; rf homogeneity must be moderately good. By contrast, the second application for this technique has very exacting requirements—in particular, very high rf homogeneity and accurate pulse timing. In this second application, the modified DEFT sequence is used to measure chemical exchange rates somewhat differently than in usual DNMR experiments. Results for amide bond rotation in N,N-dimethylacetamide are compared with literature values.