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Quadrupole excitation of ions in linear quadrupole ion traps with added octopole fields

TitleQuadrupole excitation of ions in linear quadrupole ion traps with added octopole fields
Publication TypeJournal Article
Year of Publication2008
AuthorsZhao, XZ, Granot, O, Douglas, DJ
JournalJournal of the American Society for Mass Spectrometry
Volume19
Pagination510-519
Date PublishedApr
Type of ArticleArticle
ISBN Number1044-0305
KeywordsCLOUD, fragmentation, FREQUENCIES, MASS-SPECTROMETRY, OF-FLIGHT SYSTEM, PAUL TRAP, PENNING TRAP, RESONANCES
Abstract

Modeling and experimental studies of quadrupole excitation of ions in linear quadrupole traps with added octopole fields are described. An approximate solution to the equations of motion of ions trapped in a quadrupole with added octopole and dodecapole fields, with quadrupole excitation and damping is given. The solutions give the steady-state or stationary amplitudes of oscillation with different excitation frequencies. Trajectory calculations of the oscillation amplitudes are also presented. The calculations show that there can be large changes in the amplitude of ion oscillation with small changes in excitation frequency, on both the low and high-frequency sides of a resonance. Results of experiments with quadrupole excitation of reserpine ions in linear quadrupole traps with 2.0%, 2.6%, and 4.0% added octopole fields are given. It is found that as the excitation frequency is changed, two resonances are generally observed, which are attributed to the motion in the x and y directions. The two resonances can have quite different intensities. Sudden jumps or sharp sided resonances are not observed, although in some cases asymmetric resonances are seen. The calculated frequency differences between the two resonances are in approximate agreement with the experiments.

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