Chemical structure-insensitive method and apparatus for dissociating ions

An ion trap for performing collision-induced dissociation (CID) on a precursor ion, the ion trap comprising:

• a plurality of electrodes defining an interior space therein and forming an electrode structure;
• first circuitry configured to apply a radio-frequency (RF) trapping voltage to the electrode structure at an RF trapping amplitude and RF trapping frequency to generate a quadrupolar trapping field;
• means for superposing a multipole field on the quadrupolar trapping field to generate a nonlinear trapping field;
• second circuitry configured to apply 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 to undergo CID on the precursor ion for allowing sweeping of the secular frequency towards the supplemental AC frequency;
• and
• third circuitry configured to adjust 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, such that the precursor ion absorbs energy from the supplemental AC voltage sufficient to undergo CID when the secular frequency is swept toward the supplemental AC frequency without being in resonance with the supplemental AC voltage.