Simulation of ion trajectories through a high pressure radio frequency only quadrupole collision cell by SIMION 6.0

A PC-based simulation to study the transmission properties of ions through quadrupolar collision cells has been developed. The simulation is based on the ion optics software SIMION 6.0, which enables three-dimensional (3D) representations of any geometry of a collision cell to be described. User-written programs simulated the application of both radio frequency and direct current potentials to the adjustable electrodes of the model. Two collision modeling programs were designed and compared, one based on viscous drag cooling which is applicable to ions of high m/z, and the other on discrete ion/neutral collision phenomena for ions of low m/z. The latter approach included an ion scattering model (the theory of which is described here) to simulate changes in trajectory with each binary collision. The models possess the ability to simulate collision induced dissociation experiments, with the user defining the fragment ion m/z of interest. The model was used to simulate ion exit energy distributions for both precursor and fragment ions to demonstrate the implications of collisional focusing on the spatial and energy distributions of the ions exiting the collision cell. Crown Copyright © 1999 National Research Council of Canada.