Dynamics of Nonadiabatic Reactions. 3. Effect of Enhanced Collision Energy in F + Na2 ---> NaF + Na*

Article abstract of DOI:10.1021/j100349a010

A crossed-molecular-beam study has been performed of the three-center reaction F + Na2 ---> NaF + Na(i). The relative cross sections for producing many of the electronic states of Na ( states i ranging from 3²P to 7²P) have been measured at two collision energies 4.7 and 122.8 kcal/mol.The crosss sections decreased rapidly with increasing electronic excitation, the falloff being less steep at higher collision energy.The excitation function for populating the 3²P state was measured and found to increase with increasing collision energy, suggesting tha presence of a barrier to the production of this lowest electronically excited state.The barrier height for this pathway was 4.5 kcal/mol.The excitation function for 3²D, 5²S, and 4²D states could be inferred from the measured relative cross sections; they also increased with increasing collision energy.We have performed phase space and information theory calculations at the same level of approximation to obtain distributions over electronically excited states of sodium reaction products and have compared these with experimental results.Information theory predicts a much more rapid decrease in the cross sections with increassing electronic excitation than does the phase space theory.Comparing the experimental results with phase space theory, we find that, for enhanced reagent collision energy, the distribution of the reaction product over electronically excited states is nonstatistical.In particular the first excited state (3²P) is populated at at rate an order of magnitude greater than would be expected from statistical considerations.Higher states are formed in an approximately statistical distribution.The observed dynamical bias may originate in the fact that only the 3²P state can be accessed by an adiabatic pathway.