@article {2334,
title = {Quadrupole excitation of ions in linear quadrupole ion traps with added octopole fields},
journal = {Journal of the American Society for Mass Spectrometry},
volume = {19},
number = {4},
year = {2008},
note = {ISI Document Delivery No.: 289ZDTimes Cited: 2Cited Reference Count: 24Zhao, XianZhen Granot, Ori Douglas, D. J.},
month = {Apr},
pages = {510-519},
type = {Article},
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.},
keywords = {CLOUD, fragmentation, FREQUENCIES, MASS-SPECTROMETRY, OF-FLIGHT SYSTEM, PAUL TRAP, PENNING TRAP, RESONANCES},
isbn = {1044-0305},
url = {://000255091500006},
author = {Zhao, X. Z. and Granot, O. and Douglas, D. J.}
}
@article {1200,
title = {Ion excitation in a linear quadrupole ion trap with an added octopole field},
journal = {Journal of the American Society for Mass Spectrometry},
volume = {16},
number = {6},
year = {2005},
note = {ISI Document Delivery No.: 928AZTimes Cited: 17Cited Reference Count: 32},
month = {Jun},
pages = {835-849},
type = {Article},
abstract = {Modeling of ion motion and experimental investigations of ion excitation in a linear quadrupole trap with a 4 \% added octopole field are described. The results are compared with those obtained with a conventional round rod set. Motion in the effective potential of the rod set can explain many of the observed phenomena. The frequencies of ion oscillation in the x and y directions shift with amplitude in opposite directions as the amplitudes of oscillation increase. Excitation profiles for ion fragmentation become asymmetric and in some cases show bistable behavior where the amplitude of oscillation suddenly jumps between high and low values with very small changes in excitation frequency. Experiments show these effects. Ions are injected into a linear trap, stored, isolated, excited for MS/MS, and then mass analyzed in a time-of-flight mass analyzer. Frequency shifts between the x and y motions are observed, and in some cases asymmetric excitation profiles and bistable behavior are observed. Higher MS/MS efficiencies are expected when an octopole field is added. MS/MS efficiencies ((2) collision gas) have been measured for a conventional quadrupole rod set and a linear ion trap with a 4 \% added octopole field. Efficiencies are chemical compound dependent, but when an octopole field is added, efficiencies can be substantially higher than with a conventional rod set, particularly at pressures of 1.4 X 10(-4) torr or less. (c) 2005 American Society for Mass Spectrometry.},
keywords = {EJECTION, MASS-SPECTROMETER, OF-FLIGHT SYSTEM, PAUL TRAP, RESONANT EXCITATION, SCAN, SIMULATION},
isbn = {1044-0305},
url = {://000229244800004},
author = {Michaud, A. L. and Frank, A. J. and Ding, C. and Zhao, X. Z. and Douglas, D. J.}
}
@article {422,
title = {Matrix methods for the calculation of stability diagrams in quadrupole mass spectrometry},
journal = {Journal of the American Society for Mass Spectrometry},
volume = {13},
number = {6},
year = {2002},
note = {ISI Document Delivery No.: 557DZTimes Cited: 24Cited Reference Count: 47},
month = {Jun},
pages = {597-613},
type = {Article},
abstract = {The theory of the computer calculation of the stability of ion motion in periodic quadrupole fields is considered. A matrix approach for the numerical solution of the Hill equation and examples of calculations of stability diagrams are described. The advantage of this method is that it can be used for any periodic waveform. The stability diagrams with periodic rectangular waveform voltages are calculated with this approach. Calculations of the conventional stability diagram of the 3-D ion trap and the first six regions of stability of a mass filter with this method are presented. The stability of the ion motion for the case of a trapping voltage with two or more frequencies is also discussed. It is shown that quadrupole excitation with the rational angular frequency omega = NOmega/P (where N, P are integers and Omega is the angular frequency of the trapping field) leads to splitting of the stability diagram along iso-P lines. Each stable region of the unperturbed diagram splits into P stable bands. The widths of the unstable resonance lines depend on the amplitude of the auxiliary voltage and the frequency. With a low auxiliary frequency splitting of the stability diagram is greater near the boundaries of the unperturbed diagram. It is also shown that amplitude modulation of the trapping RF voltage by an auxiliary signal is equivalent to quadrupole excitation with three frequencies. The effect of modulation by a rational frequency is similar to the case of quadrupole excitation, although splitting of the stability diagram differs to some extent. The methods and results of these calculations will be useful for studies of higher stability regions, resonant excitation, and non-sinusoidal trapping voltages. (J Am Soc Mass Spectrom 2002, 13, 597-613) (C) 2002 American Society for Mass Spectrometry.},
keywords = {CLOUD, EXCITATION, FILTER, FREQUENCY, HIGH-RESOLUTION, ION-TRAP, OPERATION, PARAMETRIC RESONANCES, PAUL TRAP, REGION},
isbn = {1044-0305},
url = {://000175893800003},
author = {Konenkov, N. V. and Sudakov, M. and Douglas, D. J.}
}
@article {4779,
title = {Observation of higher order quadrupole excitation frequencies in a linear ion trap},
journal = {Journal of the American Society for Mass Spectrometry},
volume = {11},
number = {11},
year = {2000},
note = {ISI Document Delivery No.: 367WRTimes Cited: 17Cited Reference Count: 13},
month = {Nov},
pages = {1016-1022},
type = {Article},
abstract = {{The resonant frequencies for quadrupole excitation of ions confined with a buffer gas in a linear quadrupole ion trap with Mathieu parameters a = 0 and q approximate to 0.36 have been measured. The resonances are predicted to occur at angular frequencies omega (K)(n) given by omega (K)(n) = (Omega /K)\n + beta\ without the presence of a buffer gas where Omega is the angular frequency of the trapping radio frequency},
keywords = {CLOUD, PAUL TRAP, RESONANCE EXCITATION, SIMULATION},
isbn = {1044-0305},
url = {://000090084900011},
author = {Collings, B. A. and Douglas, D. J.}
}