Patent ID: 6410913
Filing Date: 2002-06-25
Classification: H01J

Abstract:
Method for optimal collisionally induced fragmentation of selected parent ions in an ion trap filled with collision gas, comprising the following steps:a) collecting ions within the ion trap, b) isolating the selected parent ions, c) applying a drive voltage to a ring electrode of the ion trap such that the parent ions oscillate in a preselected range of secular frequencies, d) applying an excitation voltage to end cap electrodes of the ion trap in order to resonantly excite the axial oscillations of the parent ions, the excitation voltage comprising a simultaneous application of a mixture of different discrete frequencies in a predetermined frequency range, or a repeating, temporal frequency sweep through said predetermined frequency range, said predetermined frequency range encompassing said preselected range of secular frequencies, but excluding secular oscillation frequencies of daughter ions that result from fragmentation of the parent ions, e) ramping, in an increasing direction, the voltage of the frequency mixture for the excitation during a fragmentation time, and f) switching off the excitation voltage after the preselected fragmentation time.