Threshold photoelectron photoion coincidence studies of parallel and sequential dissociation reactions.

Recent advances in threshold photoelectron photoion coincidence (TPEPICO) make possible the analysis of several parallel and sequential dissociations of energy selected ions. The use of velocity focusing optics for the simultaneous collection of threshold and energetic electrons not only improves the resolution, but also permits subtraction of coincidences associated with "hot" electrons, thereby yielding TPEPICO data with no contamination from "hot" electrons. The data analysis takes into account the thermal energy distribution of the sample and uses statistical theory rate constants and energy partitioning in dissociation reactions to model the time of flight distributions and the breakdown diagram. Examples include CH2BrCl and P(C2H5)3. Of particular interest is the ability to extract error limits for rate constants and dissociation energies.