Cross sections and thermal rate constants for the isotope exchange reaction: D(S2)+OH(Π2)→OD(Π2)+H(S2)

Abstract

We report state-to-state and overall thermal rate constants for the isotope exchange reaction D((2)S)+OH((2)Pi)-->OD((2)Pi)+H((2)S) for 0 K<T<500 K. The reaction cross sections were determined by a statistical capture model which includes the electronic degrees of freedom of the OH(OD) radical. Both the D+OH and OD+H channels are described by four ab initio potential-energy surfaces ((1,3)A' and (1,3)A"). All electronic and spin-orbit couplings are included. We predict a reaction rate constant of 14.22 x 10(-11) cm(3) molecule(-1) s(-1) at T=100 K and 10.78 x 10(-11) cm(3) molecule(-1) s(-1) at T=300 K. At lower temperatures, around 50 K, the value rises to k(T)=15 x 10(-11) cm(3) molecule(-1) s(-1). The predicted rate constants confirm the earlier theoretical and experimental results. A negative temperature dependence in the rate constant is observed. The state-resolved cross sections and rate constants predict a significant propensity toward the formation of the OD (A') Lambda-doublet level and the ground spin-orbit manifold F(1).