| 摘要 |
An ion trap mass analyzer is disclosed comprising a segmented rod set. Ions are trapped radially within the mass analyzer by a radial pseudo-potential well. The ions are also confined axially within the ion trap by an axial electric field. The axial electric field is substantially linear across the central section of the ion trap, i.e. has a quadratic potential profile, but the electric field is distorted across both ends of the ion trap (see Figures 7 & 12). A supplemental AC voltage or potential is applied to the electrodes comprising the ion trap mass analyser in order to resonantly or parametrically excite ions within the ion trap 1. The distortions in the electric field at the ends of the ion trap cause the resonant frequency of ions within the ion trap to shift to either a higher or lower frequency (see Figures 8, 10, 13 & 15). If the frequency of the supplemental AC voltage or potential is scanned appropriately then ions are ejected from the ion trap in a shorter/longer period of time leading to an improvement in mass resolution (see Figures 9,11,14 & 16). |
