Temperature dependence of the vibrational energy distributions in the reactions F + H2 and F + D2

Abstract

Using chemical laser methods, the behavior of the product vibrational distributions in the reactions ${\mathrm{F+H}}_2\to \mathrm{HF+H}$ and ${\mathrm{F+D}}_2\to \mathrm{DF+D}$ has been studied as a function of reactant temperature. Both the equal‐gain and zero‐gain techniques were employed. In the F + H₂ system, k₃/k₂ and k₂/k₁ increase as temperature decreases, k₂/k₁ showing a much stronger dependence than k₃/k₂. Both the k₃/k₂ and k₂/k₁ temperature dependences fit an Arrhenius‐type form, $k_3{\mathrm{/k}}_2\text{= 0.39\hspace{0.17em}}\exp \text{\hspace{0.17em}(+117/R\hspace{0.17em}T)}$ and $k_2{\mathrm{/k}}_1\text{= 2.14\hspace{0.17em}}\exp \text{\hspace{0.17em}(+254/R\hspace{0.17em}T)}$ . An opposite behavior is observed for the F + D₂ system: k₃/k₂ rises with increasing temperature. These results provide the first quantitative evidence that reaction product vibrational distributions are temperature dependent and they demonstrate the applicability of chemical lasers to such measurements.