Friday, November 2, 2007
FID Truncation and Spectral Distortion
Have you ever seen a spectrum like the one in the lower trace of the figure below?
This sin(x)/x distortion at the base of an NMR line is the result of truncation of the FID. The acquisition time was not long enough to capture the entire time domain signal. In addition to the distortion at the base of the lines, there is also a loss in spectral resolution as "sharp" features in a spectrum are defined by later times in the free induction decays. If you see this, you should re-run your spectrum with a longer acquisition time. If you do not have the option of re-running the spectrum, increase the line broadening (LB) and re-transform the data. This will get rid of the distortion but will not help with the resolution.