Patent ID: 8334507

Claim:
A method for fragmenting parent ions, comprising: (a) providing a multipole ion guide having an axis within an enclosure having an entrance aperture and an exit aperture; (b) providing an electron source outside the multipole ion guide; (c) providing, within the enclosure, background gas from a controllable gas supply; (d) directing electrons from the electron source with kinetic energies below 10 electron volts to a region proximal to the axis; (e) applying AC and DC voltages to electrodes of the multipole ion guide; (f) applying voltages to the entrance and exit apertures to trap parent ions within the ion guide; and (g) focusing the trapped parent ions to the region proximal to the axis, wherein the electrons and the trapped parent ions interact to cause fragmentation of at least some of said trapped parent ions to produce a population of parent ions and fragment ions within the enclosure.