Modeling dipolar excitation for quadrupole mass filter

The results of modeling AC and DC dipole excitation of ion oscillations in a quadrupole mass filter are presented. The simulation is done by numerical integration of the ion motion equations, ions' initial coordinates and velocities are distributed normally. For AC dipole excitation the instability bands on the (a, q) stability diagram follow along the isolines beta(x)/2 and beta(y)/2, creating regular dips on the transmission contour. We show that AC excitation at frequency Omega/2 makes it possible to control the resolution of the mass filter by either changing the AC amplitude or phase. Instability bands can be used for mass selective excitation in a linear ion trap. Options for the joint use of DC and AC dipole excitation to form the mass peak shape are considered.

Automated summary

This paper presents the results of modeling AC and DC dipole excitation of ion oscillations in a quadrupole mass filter. The simulation was done by numerically integrating the ion motion equations, with ions' initial coordinates and velocities distributed normally. It is shown that AC excitation can control the resolution of the mass filter by changing the AC amplitude or phase. The instability bands can be used for mass selective excitation.