Rather than scanning a frequency range, like the original continuous wave spectrometers, modern NMRs use a radio frequency pulse to excite a range of frequencies at once then monitor the decay of the resultant signal with time. After acquiring the signal, the fourier transform is used to process it from the time domain to the more familiar frequency domain. Pulsed fourier transform NMR is much faster than continuous wave NMR, enabling more extensive signal averaging and thus increasing sensitivity per unit time.
