Formation and Detection of Metastable Ions in a Double-Focusing Mass Spectrometer

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Abstract
By changing the acceleration voltage independently from the voltage applied to the electrostatic analyzer of a double-focusing mass spectrometer, it is possible to detect “metastable” ions which are formed in the field-free drift region in front of the electrostatic analyzer. The parent and daughter ions of the decomposition can be determined unambiguously. Applying this technique to various compounds it was found that it is also possible to detect ions whose decomposition originates during acceleration by the ion gun as well as during flight through the electrostatic analyzer. Theoretical calculations are presented which verify these assumptions and show the location of decomposition in the electrostatic analyzer. Using this technique, it was also possible to show that doubly charged ions may undergo a metastable transition which leads to another doubly charged ion.