Ion cyclotron resonance spectroscopy has been adopted for the detection of gaseous ions formed within an analyzer cell of new design. Ions formed by electron impact have been trapped within the analyzer cell for as long as 0.10 sec and detected with a half‐height mass resolution of 5000. Even at pressures of 10−5Torr ion‐molecule reactions of high kinetic order may be observed. An important feature of the trapped ion analyzer cell is that it retains the capability of the ICR double resonance experiment for elucidating the reaction sequence occurring in a complex mixture of primary ions and high order product ions. A pulsed magnetic field detection scheme accurately limits the residence time of the ions within the trapped ion analyzer cell.