A tandem mass spectrometer system and method are described, where a composite voltage waveform is applied to so as to trap ion having selected m/z. The trapped ions may be subject to collision induced ionization dissociation (CID) by a selectable discrete frequency voltage waveform positioned so as to be in a notch in a broadband waveform. The resultant ion products may be trapped using a second notch having a center frequency corresponding to the ion product to be trapped. The process may be repeated so as to increase the amount of ions produced, or the process a first resultant ion product to yield a second resultant in product, which may be trapped.