KINETICS OF COLLISION-INDUCED DISSOCIATION IN THE PAUL TRAP - A FIRST-ORDER MODEL

A first-order model describing the kinetics of collision-induced disso ciation (CID) of polyatomic ions as effected via single-frequency reso nance excitation in the Paul ion trap is presented, A mathematical exp ression for the dissociation rate constant associated with the model i s developed from the kinetic theory of ion transport in gases, the for ced, damped harmonic oscillator model for ion-trap resonance excitatio n, 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 chang es due to inelastic ion/helium collisions to be followed as a function of time; dissociation kinetics are included in the simulation by term inating the random walk when the ion internal energy exceeds the minim um required for fragmentation, Validity of the mathematical analysis a nd random walk simulation for the model is confirmed by comparison wit h experimental phenomenology associated with CID kinetics in the Paul trap. The first-order model in its present form, along with refinement s resulting from further detailed comparison with experimental data, s hould therefore be a useful tool in expanding our understanding of pol yatomic ion energetics in the Paul trap.