A collision or reaction device for a mass spectrometer is disclosed comprising a first device arranged and adapted to cause first ions to collide or react with charged particles and/or neutral particles or otherwise dissociate so as to form second ions. A second device is arranged and adapted to apply a broadband excitation with one or more frequency notches to the first device so as to cause the second ions and/or ions derived from the second ions to be substantially ejected from the collision or reaction region. The collision or reaction device further comprises a device arranged and adapted to determine the time when the second ions and/or ions derived from the second ions are substantially ejected from the first device.