Statistical Rice-Ramsperger-Kassel-Marcus quasiequilibrium theory calculations in mass spectrometry

Abstract

The statistical theory [Rice-Ramsperger-Kassel-Marcus quasiequilibrium theory (RRKM/QET)] for calculating dissociation rate constants is explained and its implementation is outlined with sample computer programs. The energy deposition involved in various types of ionization processes is discussed and related to the appearance of the mass spectrum. The RRKM/QET calculations are used to explain the kinetic shift and its effect on the observed onset for fragmentations in the halobenzene ions. Direct dissociation versus rearrangement reactions are discussed in terms of the dissociation rates and the observation of metastable ions. Finally, it is shown how an average rate constant can be obtained from metastable peak intensities as a function of the ion extraction voltage in a conventional mass spectrometer.