A unified description of space charge effects in FT-ICR mass spectrometry
- Pacific Northwest Lab., Richland, WA (United States)
Phenomena arising from the Coulombic interaction due to interactions between different m/Z ion clouds, same m/Z ions, or image charge induced on the trap electrodes, are generically referred to as space charge effects. Trap geometry as well as the shape of the ion cloud determine the maximum number of ions which can be confined in a Penning-like ion trap. The authors consider the two important cases of either spherically or cylindrically shaped ion clouds (i.e. coherently moving ion ensembles with different m/Z). These models exhibit the most important space charge effects in Fourier transform ion cyclotron resonance mass spectrometry including frequency shifts, amplitude and phase modulation and phase-locking. Both positive and negative frequency shifts are possible for spherical ion clouds when their cyclotron radii differ. Due to the Coulombic interaction between ion clouds, cyclotron radius and phase modulation occurs. This modulation increases inversely to the cyclotron frequency difference. Cyclotron phase-locking results when two ion clouds have similar mass to charge ratios and a sufficiently large ion population, at which point a mass spectrum shows only a single peak. Spherical ion clouds are usually more likely to phase-lock than cylindrically shaped clouds. The phase-locking threshold sets {close_quotes} new limits to the maximum resolution, mass accuracy and dynamic range achievable by mass spectrometry. Numerical and analytical methods are applied to two related problems of immense importance to FT-ICR mass spectrometry. The first studies the dynamics of an individual ion cloud in the presence of external perturbing forces which act to destroy cloud coherence. The second problem involves the dynamics of Coulombically interacting in clouds.
- OSTI ID:
- 210668
- Report Number(s):
- CONF-9505261-; TRN: 96:001157-0107
- Resource Relation:
- Conference: 43. American Society of Mass Spectrometry (ASMS) conference on mass spectrometry and allied topics, Atlanta, GA (United States), 21-26 May 1995; Other Information: PBD: 1995; Related Information: Is Part Of Proceedings of the 43rd ASMS conference on mass spectrometry and allied topics; PB: 1411 p.
- Country of Publication:
- United States
- Language:
- English
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