Abstract
The effect of endcap holes on resonance ejection of trapped ions has never been fully examined in the literature. The presence of holes in the electrodes adds higher order negative components to the field inside the trap. The absolute magnitudes of these components that define the field along the central axis of the trap were defined by numerically simulating the fields inside the trap and then using least squares to fit a polynomial expansion of the potential. The absolute value of the field components were found to increase with increasing hole size. The fitted potential was then used to reexamine the amplitude response function. The addition of negative higher order field components produces up to four inflection points in the amplitude response function. The new inflection points may produce multiple jump phenomena in forward scans as well as a jump condition in the reverse scan mode that has not previously been considered. The shape of the amplitude response function is dependent on the hole size and the amplitude of the dipole excitation waveform at constant buffer gas pressure. The shape of the function has interesting implications for the resonance ejection process. This work provides new insights into the resonance excitation process in nonlinear ion traps.