STATISTICAL MODELING OF COLLISION-INDUCED DISSOCIATION THRESHOLDS

Analysis of the energy dependence of the cross sections for collision- induced dissociation reactions has permitted the determination of quan titative thermodynamic information for a variety of ionic clusters. As such clusters become larger, the rate at which the decomposition occu rs becomes comparable to the instrumental time available for observing the reaction. A method for incorporating statistical theories for ene rgy-dependent unimolecular decomposition in this threshold analysis is reviewed and updated. The revision relies on the fact that for most i onic clusters, the transition state is a loose association of the prod ucts that can be located at the centrifugal barrier. This: permits a s traightforward estimation of the molecular parameters needed in statis tical theories for the transition state. Further, we also discuss seve ral treatments of the adiabatic rotations of the dissociating cluster. The various models developed here and previously are compared and use d to analyze a series of data for Li+(ROH) complexes, where ROH=methan ol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, s-butanol, and t-butanol. The trends in the bond energies derived by these variou s models are compared and their accuracy evaluated by comparison with relative values determined by equilibrium methods. (C) 1997 American I nstitute of Physics.