FIRST-DATA-POINT PROBLEM AND THE BASE-LINE DISTORTION IN FOURIER-TRANSFORM NMR-SPECTROSCOPY WITH SIMULTANEOUS SAMPLING

The,baseline distortions often arising in spectra after linear phase correction have often been attributed to an improper value of the first acquired data point of the free-induction decay. However, correction of this value by multiplying it by a certain factor depending on the timing of the excitation sequence has not proved to be reliable unless some very specific conditions are met. In this article, the origin of these distortions is thoroughly examined in both the frequency and the time domain. It is shown that the problem can be explained generally as an improper resampling of the original signal as a result of the linear phase correction. A way of avoiding these artifacts is proposed. However, it is shown that generally the proper correction must affect the whole signal in a complex way and that suitable timing of the experiment is highly desirable. (C) 1994 Academic Press, Inc.