Reaction of Br(-) with WF6: Competition between Charge Transfer and Association;Influence of Temperature, Pressure, and Vibrational Energy

摘要

The rate coefficient for the reaction of Br(-1) with WF6 was found to be (6 plusor minus 2) x 10 to the minus 10th cm cubed s to the minus 1st, independent of temperature and pressure over the ranges 243 to 433 K and 0.2 to 1.2 Torr. The reaction proceeds by two channels: association to form WF6Br(-1) and charge transfer to form WF6(-1). The association fraction was found to depend strongly on temperature and pressure, varying from more than 90% association at low temperatures and high pressures to less than 10% association at high temperatures and low pressures. The reaction as studied here is in the falloff regime of association reactions. A steep temperature dependence is observed in the association fraction at high temperatures. This steep temperature dependence is a consequence of WF6 having many low frequency vibrational levels. Vibrational energy is here found to promote charge transfer more efficiently than does kinetic energy.