title: The coupling effects of hexapole and octopole fields in quadrupole ion traps: a theoretical study.
abstract: A theoretical method, the harmonic balance method, was introduced to study the coupling effects of hexapole and octopole fields on ion motion in a quadrupole ion trap. Ion motion characteristics, such as ion motion center displacement, ion secular frequency shift, nonlinear resonance curve and buffer gas damping effects, have been studied with the presence of both hexapole and octopole fields. It is found that hexapole fields have bigger impacts on ion motion center displacement, while octopole fields dominate ion secular frequency shift. Furthermore, the nonlinear features originated from hexapole and octopole fields could enhance or cancel each other, which provide us more space in a practical ion trap design process. As an example, an ion trap with improved performance was designed using a specific combination of hexapole and octopole fields. In this ion trap, a hexapole field was used to achieve efficient ion directional ejection, while an octopole field was added to correct the chemical mass shift and resolution degradation introduced by the hexapole field.
authors.affiliation: Department of Biomedical Engineering, Beijing Institute of Technology, Beijing, 100081, China.
authors.forename: Yuzhuo
authors.initials: Y
authors.lastname: Wang
authors.forename: Zejian
authors.initials: Z
authors.lastname: Huang
authors.forename: You
authors.initials: Y
authors.lastname: Jiang
authors.forename: Xingchuang
authors.initials: X
authors.lastname: Xiong
authors.forename: Yulin
authors.initials: Y
authors.lastname: Deng
authors.forename: Xiang
authors.initials: X
authors.lastname: Fang
authors.forename: Wei
authors.initials: W
authors.lastname: Xu
keywords: coupling effects; harmonic balance method; hexapole; octopole; quadrupole ion trap