As per the Stejskal–Tanner equation, the intensities of each peak decrease as the gradient amplitude is increased, allowing the diffusion coefficients to be extracted from the decay pattern via one of many curve-fitting procedures. In the table below, 0 means not observed, + positive, and − negative, and the DEPTQ variant is included for completeness:Ī pseudo-2D NMR experiment, where chemical shifts are presented on the horizontal axis and self-diffusion coefficients corresponding to each peak on the vertical axis (much like the indirect dimension in 2D NMR, hence ‘pseudo-2D’).Ī DOSY experiment consists of a series of 1D diffusion experiments, recorded with different amplitudes of pulsed field gradients (PFGs).

The signs of the peaks may be controlled using the flip angle of the final proton pulse, which is usually appended to the experiment name. The editing feature alters the sign of the carbon resonances according to the number of directly attached protons, allowing the identification of carbon multiplicities. Since 1H has a fourfold larger gyromagnetic ratio compared to 13C, the initial population difference for 1H spins (loosely speaking, the difference between the number of spin-up and spin-down nuclei) is approximately four times larger, which translates into higher sensitivity. The sensitivity gain arises because the experiment is started with proton excitation, with the proton magnetisation subsequently being transferred onto carbon. 1D 13C spectra (including DEPT) are only useful for structural assignment if there is intractable peak overlap in the HSQC, which is rare. Note that the DEPT experiment has largely been superseded by the multiplicity-edited HSQC, which provides more information with greater sensitivity and often in less time. A 1D experiment used for enhancing the sensitivity of carbon observation and for editing of 13C spectra.

Mestrenova multiplet abbreviations