stored waveform inverse fourier transform A technique to create excitation waveforms for ions in FT-ICR mass spectrometer or Paul ion trap. An excitation waveform in the time-domain is generated by taking the inverse Fourier transform of an appropriate frequency-domain programmed excitation spectrum, in which the resonance frequencies of ions to be excited are included. This technique may be used for selection of precursor ions in MS2 experiments. SWIFT MS:1000284 MS mass spectrometry acquisition method