In a tandem mass spectrometer using a collision cell for ion fragmentation, the upper limit of the collision energy required for collision induced dissociation (CID) can be extended without reaching or going beyond the upper electrical discharge limit of the system components. The present teachings describe a method of lifting the potential energy of ions to a predetermined level sufficient for CID fragmentation while satisfying a discharge free condition. The present teaching also describes a method of lifting the potential energy of the fragment ions after CID fragmentation so that the product ions have sufficient energy for mass analysis.