ION STORAGE COMBINED WITH REFLECTRON TIME-OF-FLIGHT MASS-SPECTROMETRY- ION CLOUD MOTIONS AS A RESULT OF JET-COOLED MOLECULES

The storage of molecular ions in a quadrupole ion trap in combination with reflectron time-of-flight mass spectrometry, jet cooling and mult iphoton laser ionization is presented. Jet-cooled molecules are introd uced as neutrals into the ion trap and ionized by multiphoton absorpti on. Varying the storage time causes a dramatic change in the ion inten sities, depending on their m/z ratio. This observation cannot be expla ined by electronic synchronization effects, but is identified as secul ar motions of the stored ions. In this paper it is demonstrated that f or a time span of up to several milliseconds the ions remain coherent in space and kinetic energy. The molecular ions as well as their fragm ent ions are not dispersed in the ion trap but move in close ion cloud s describing Lissajous trajectories. Consequently, the distance betwee n the middle of the ion trap and the ion cloud periodically changes, r esulting in a storage time dependence on mass resolution, flight time and signal intensity. The influences of storage time and other trappin g parameters as well as their effect on the interpretation of the resu lts, which are obtained in investigations of time-resolved ion process es, will be discussed.