Artifacts seen in Bruker spectra
Bruker data is often acquired using "sequential" data acquisition (rather than true complex, or "simultaneous" data acquisition) to accomplish quadrature detection. With sequential acquisition, the data is digitized at twice the rate and points are placed into the 2 channels alternately. This means that the nth data point in the 2 channels were not acquired at the same time, and are not a true complex pair.
One consequence of this is that a special type of FT must be performed (known as a Bruker transform). Nuts should correctly identify sequential data, which is identified by setting the Domain parameter to TPPI, and executing an FT should will automatically perform the appropriate type of FT.
Another problem which can occur is that the real and imaginary halves of the data can get exchanged in the course of moving the data to the PC. If the data is complex, this simply reverses the spectrum. If the data is sequential, this results in appearance of artifacts in the spectrum which resemble severe quadrature images. Executing an RI command (switching Real and Imaginary points) before the FT will fix the problem. An entry has been added to the NUTS.INI file which allows the user to automatically perform an RI on Bruker data at the time it is imported into NUTS, so that the user does not have to do this explicitly. The relevant entry in the NUTS.INI file is:
- BRUKER_ASPECT_RI = TRUE
This is the correct spectrum.
This spectrum results from exchanging the real and imaginary halves of the data before FT.
This spectrum results from performing a Complex FT on Bruker sequential data, instead of a Bruker FT.
Special considerations for Bruker data
Last updated: 11/3/97.