Numerical simulation of autoresonant ions oscillations in an anharmonic electrostatic trap

TL;DR

This paper models ion dynamics in an anharmonic electrostatic trap used in mass spectrometry, revealing how autoresonant interactions enable selective ion extraction and how harmonic effects can influence selectivity.

Contribution

It provides a numerical simulation of ion behavior in an anharmonic trap, highlighting the role of harmonics in ion extraction selectivity.

Findings

Ion extraction occurs at fundamental and harmonic frequencies.

Harmonics can cause cross-contamination of ion detection.

Autoresonant interaction increases ion oscillation amplitudes.

Abstract

This work presents the results of modelling the ion dynamics in the ART-MS (Autoresonant Trap Mass Spectrometry) device in the quasi-static approximation. This instrument utilizes an anharmonic, purely electrostatic trap for ion confinement and a radio frequency (RF) voltage source with decrementally varying frequency for selective ion extraction. The autoresonant interaction between the oscillatory motion of the ion and the RF voltage causes an increase in the amplitude of certain confined ions, allowing their selective extraction. Numerical modelling shows that the extraction of ions with a given mass occurs not only at the fundamental frequency but also at its harmonics. This effect reduces the selective properties of devices of this type because along with the main mass component for a given frequency, it is possible to enter the detector channel of ions with another mass, for which this frequency corresponds to the second or higher harmonics, even a superposition of some of these harmonics of different ions.