Patent ID: 7759641

Claim:
A mass spectrometer comprising: an ion source for generating ions; a linear ion trap having multiple rod electrodes for at least two of storing, mass-selectively isolating, mass-selectively dissociating, and mass-selectively removing ions; electric-field forming electrodes for forming an electric field along an axial direction of the linear ion trap, wherein the electric field is an electrostatic potential; a power supply unit for controlling operation of the linear ion trap; and a detector for detecting ions ejected from the linear ion trap, wherein said electric-field forming electrodes are inserted between adjacent rod electrodes of said multiple rode electrodes and the power supply unit includes a first supplemental AC power supply unit applying a supplemental AC voltage to the rod electrodes and a second supplemental AC power supply unit applying a supplemental AC voltage to the electric field forming electrodes, wherein upon application of the supplemental AC voltage to the rod electrodes by the first supplemental AC power supply unit, ions in the linear ion trap are oscillated in a radial direction of the linear ion trap via resonance excitation, and thereby ions having a mass/charge ratio within a first predetermined range are mass-selectively isolated, and wherein upon application of the supplemental AC voltage to the electric field forming electrodes by the second supplemental AC power supply unit, ions in the linear ion trap are oscillated in the axial direction of the linear ion trap by resonance excitation, and thereby ions in the linear ion trap having a mass/charge ratio within a second predetermined range are mass-selectively dissociated.