person of skill in the art to be a u201c radio frequency u201d signal the ac or rf signal used to fragment an ion species m n may be a single or discrete frequency or may be a signal having a narrower band than the notch in the wideband waveform or a lower amplitude of signal in the notch region that is the amplitude and other characteristics of the signal in the notch region is selected based on the fragmentation process requirements and the amplitude outside of the notch region may be selected on the basis that notch region is being used for isolation and the remaining regions preferably expel other ions a plurality of notches in the broadband waveform and a plurality of discrete frequencies may be provided either simultaneously or sequentially depending on the specific objectives of the measurements to be performed moreover a person of skill in the art would understand that the term u201c broadband u201d means that the frequency and amplitude of the waveform are selected so as to encompass a range of m z such that the ions of undesired m z values are selectively eliminated from the ion trap a notch in the broadband waveform would be understood to be a reduction in the amplitude of the waveform so that the effect of the waveform on an ion of a desired m z is to retain the ion in the ion trap with or without further dissociation the amplitude of the waveform in the notch region is selected to either provide further dissociation of the ion or is sufficiently low as to.