Reactive scattering studies of nonadiabatic multichannel reaction dynamics: Oxygen atoms + unsaturated hydrocarbons

We have investigated the reaction dynamics of ground state oxygen atoms with unsaturated hydrocarbons (acetylene, ethylene, allene and methylacetylene) using the crossed molecular beams method with “universal” mass spectrometric detection. By exploiting “soft” electron-ionization we have probed all energetically allowed channels and determined how the dynamics, branching ratios and extent of inter-system-crossing (ISC) from triplet to singlet potential energy surfaces (PESs) vary with collision energy. ISC is found to increase strongly with molecular complexity and to depend on molecular structure. Experimental results are compared with those of available statistical calculations for all systems and with those of quasiclassical-trajectory surface-hopping computations carried out in a synergic fashion by the group of Bowman on coupled ab initio triplet and singlet PESs for the benchmark multichannel nonadiabatic reaction O + ethylene.