Routine Prediction
Not everybody remembers how easy it is and how effective it can be to add (or correct) a few points at the beginning of the FID. Two years ago I explained how Linear Prediction works and how we can extrapolate the FID in both directions. This time I will show a simple practical application. I have observed that, in recent years, C-13 spectra acquired on Varian instruments require a much-larger-then-it-used-to-be phase correction. When I say correction, I mean first-order phase correction, because the zero-order correction is merely a different way of representing the same thing (a different perspective). A large first-order phase correction can be substituted with linear prediction. I will show the advantage with a F-19 example, yet the concept is general. The spectrum, after FT and before phase correction, looks well acquired. Now we apply the needed correction, which amounts to no less than 1073 degrees. Have you noticed what happened to the baseline? It's all predictable. When y...