| 摘要 |
An improved field comprising two quadrupole trapping fields is established i n a region (16) defined by the ring (11) and end (12, 13) electrodes of a three-dimensional quadrupole ion trap, and the amplitude of an RF (and/or DC) component (and/or the frequency of the RF component) of one or both trapping fields is changed to sequentially excite trapped ions. Alternatively, a trapping field cap able of storing ions having mass-to-charge ratio within a selected range is establis hed, a supplemental field is superimposed with the trapp ing field to eject unwanted ions having mass-to-charge ratio within a second selected range, the supplemental field having frequency component s in a frequency range except for a notch frequency band within the range, and an improved field is then established by superimposing the trapping field with a second trapping field of substantially identical spati al form.
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