When recording the non-uniformly sampled spectrum, one needs to indicate which FIDs are to be recorded. In our lab MK and CF rewrote the standard pulse sequences to use an additional file, VDLIST, which does exacly that. These pulseprograms usually have a suffix .NUS and before you launch the data acquisition, you should run a script from within TopSpin, called SPARSE on our 800MHz and 500MHz instruments or SPARSE600 on the 600MHz. These scripts generate the VDLIST file. If the entry in VDLIST is '1u', an FID pair (Re and Im or Echo and AntiEcho) is skipped, if the entry is 3u, it is recorded and stored in the SER file. To be able to process the spectrum you must have the correct VDLIST file.
The first step of the processing is thus rearranging the recorded FIDs and putting them into a new file, similar in structure to SER. Fill out the required fields on the first work page of the MDD program. Most often, you would need to use the prefilled values. You need two input files: SER and VDLIST and one output file SER.SP. Press the INSERT ZEROS button and check the console window for any error messages. Then move to the next page. For the purpose of clarity, this text will assume that the FIDs are now rearranged into SER.SP file.