Data processing
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Modern NMR data is recorded in the time domain (TD) in the form of free induction decay traces. Once acquired, time domain data almost always needs to be converted to the frequency the domain (FD).
Fourier transformation is the most frequently used method for such conversion.
Term NMR data processing applies to the transformation of the TD data to FD and additional steps that might be taked before and after the transformation.
Some of the steps taken prior to the TD→FD transformation are:
processing step | how it's done in software | meaning of transformation |
zero filling | nmrPipe | appending a certain number of zero values to the end of each fid; once Fourier-transformed such data has more points per unit frequency - and therefore appears smoother. |
fid shift | the process involves shifting data points to the left or right - this is typically done to remove 'bad' data points | |
linear prediction | a process to manipulate the data points by predicting their placement - this is typically used for removing artifacts and distortions in the beginning of an FID or to expand truncated data | |
apodization | multiplication of data vectors with exponential, sine-bell, etc. functions to enhance shape of frequency domain data |