My question has two parts: One is general and has to do with the Fourier-Transformation, one has to do with Time-Domain NMR. Both parts are interlinked, of course.

I tried to find out, why people do Time-Domain (TD) NMR instead of Fourier-Transform (FT) NMR, which is up to my knowledge by far the standard.

Part 1 on TD-NMR

On my search on TD-NMR, I found a vendor that states on his website

...low magnetic field results in a low resolution, which is insufficient for obtaining Fourier-transformation frequency spectra.

Certainly, for Fourier-approaches, there has to be a certain number of sample points available to get good spectra. On the other hand, fitting the signal in time-domain with few data points is equally problematic. So, why is it done and is TD-NMR done with some kind of special fitting approach?

Part 2, general

The vendor stated that TD-NMR uses low magnetic fields, which also translates to a low signal-to-noise ratio. Is there a reason why signal processing should be done in TD only because of an SNR issue? I imagine, since the FT is a linear transformation, there should be no gain or loss in terms of SNR, right? Hence, it should not impede the choice of the domain that you would like to work in.

  • $\begingroup$ Data processing in the time or the frequency domain are equivalent, both have exactly the same SNR if done correctly. TD techniques are important in magnetic resonance because we are 1) dealing with a quantum system that evolves in the time domain and 2) practical implementations of NMR experiments are much more flexible when they are being done with TD methods. Any good textbook on NMR will contain dozens of TD methods that allow precision measurements on certain aspects of interactions. As for the vendor... it sounds like someone is trying to pull your wallet. Ignore that and get a textbook. $\endgroup$ – CuriousOne Feb 10 '16 at 11:27
  • $\begingroup$ 1) It would be helpful if you defined NMR for the reader. 2) While it is true that a standard FFT should have an output that one can then invert to go back to the time-domain, when processing/converting data it is rarely the case the the software/instrument keeps both the FFT'd result and the original signal. Generally, if one is only given the FFT'd result it is not possible to determine the original time series input. $\endgroup$ – honeste_vivere Apr 13 '16 at 13:14

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