A first-order model describing the kinetics of collision-induced dissociation (CID) of polyatomic ions as effected via single-frequency resonance excitation in the Paul ion trap is presented. A mathematical expression for the dissociation rate constant associated with the model is developed from the kinetic theory of ion transport in gases, the forced, damped harmonic oscillator model for ion-trap resonance excitation, and thermal kinetic theory. Ion-trap CID is also simulated using a random walk sequence, corresponding to the processes believed to occur during collisional activation, which allows ion internal energy changes due to inelastic ion/helium collisions to be followed as a function of time; dissociation kinetics are included in the simulation by terminating the random walk when the ion internal energy exceeds the minimum required for fragmentation. Validity of the mathematical analysis and random walk simulation for the model is confirmed by comparison with experimental phenomenology associated with CID kinetics in the Paul trap. The first-order model in its present form, along with refinements resulting from further detailed comparison with experimental data, should therefore be a useful tool in expanding our understanding of polyatomic ion energetics in the Paul trap.
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Goeringer et al. (1996) studied this question.