Patent ID: 6114691
Filing Date: 2000-09-05
Classification: H01J

Abstract:
A method of operating a multipole mass spectrometer having an entrance end and an exit end and having a plurality of pairs of rod-like electrodes extending along an axis, comprising:(a) supplying ions into the entrance end of the mass spectrometer(b) applying an RF drive voltage to said pairs of rods, while applying either no DC drive voltage or a very low DC drive voltage to said pairs of rods, to generate a substantially RF-only field in which a range of ion masses is stable and pass through said spectrometer while other ion masses are rejected,(c) applying an auxiliary RF voltage to said rods at a selected q to radially excite ions which are in resonance with said auxiliary RF field but at an amplitude low enough that a plurality of such excited ions do not strike said electrodes but instead are transmitted through said spectrometer,(d) at the exit end of the mass spectrometer, for ions that have been transmitted through the mass spectrometer, discriminating between said plurality of excited ions and other ions; and(e) detecting and analyzing at least some of said plurality of excited ions.