Patent ID: 7842918

Claim:
A method for exciting a precursor ion in an ion trap, the method comprising: trapping the precursor ion in a nonlinear trapping field including a quadrupolar field and a multipole field, the quadrupolar field generated by applying a radio-frequency (RF) trapping voltage to an electrode structure of the ion trap at an RF trapping amplitude and RF trapping frequency; applying a supplemental alternating-current (AC) voltage to the electrode structure at a supplemental AC amplitude and supplemental AC frequency, the supplemental AC frequency differing from the secular frequency of the precursor ion by an offset amount insufficient for collision induced dissociation of the precursor ion for allowing sweeping of the secular frequency towards the supplemental AC frequency to result in collision induced dissociation of the precursor ion; and adjusting the ion secular frequency by adjusting at least one of a plurality of operating parameters of the ion trap, the operating parameters including the RF trapping amplitude, the RF trapping frequency, and the supplemental AC frequency, whereby the precursor ion absorbs energy from the supplemental AC voltage sufficient to undergo collision-induced dissociation (CID) without being in resonance with the supplemental AC voltage.