Simulation of the simultaneous dual-frequency resonance excitation of ions in a linear ion trap.

Abstract

The process of ion resonance dipolar excitation in a linear ion trap by 2 ejection waveforms with close frequencies is studied. The physical mechanism of increasing the resolving power using the ion excitation is a nonlinearity of the electric radio frequency fields caused by space charge. Using 2 resonance forces with 2 close frequencies leads to the completion of 2 excitation processes. In the case of the perfect quadrupole electric field, the ion motion equations are linear, and as a result, the respondent ion ensemble is also a linear and valid superposition principle. Nevertheless, the resolution increases (20%) in the case of lack of a space charge in an operating mode with a dual-frequency. The numerical simulations show that the mass shift is removed, and the mass resolution is increased via dual-frequency resonance excitation when the frequency difference (approximately 2.5kHz) is relatively small and the phase difference of 2 harmonic signals is 0-π3 even at a high linear ion density of up to 50000 ions per radius field r0 .