METASTABLE ION CHARACTERISTICS . MEASUREMENTS WITH A MODIFIED TIME-OF-FLIGHT MASS SPECTROMETER

The sensitivity for the measurement of ions produced by metastable decompositions in the flight tube of a time-of-flight mass spectrometer has been increased by a factor of up to 200 by defocusing the interfering normal ions. The method provides unique identification of the precursor ion and the metastable decompositions which it undergoes. A computer technique is described which yields accurate values of daughter ion masses. “Flat-topped” metastables can be observed, and the method appears advantageous for detecting small values of kinetic energy released in the formation of such peaks. The method is particularly valuable for the study of collision-induced metastabletransitions; there is a high probability for reaction in the long drift region, and the neutral decomposition products which can be observed serve as a measure of the drift region pressure. © 1969, American Chemical Society. All rights reserved.