Rate constants for the reaction, H+D2→HD+D, over the temperature range, 724–2061 K, by the flash photolysis-shock tube technique

Abstract

Thermal rate constants measured by the flash photolysis-shock tube (FP-ST) technique are reported for the reaction, H+D2→HD+D, over the temperature range, 724–2061 K. H-atom concentration has been monitored by atomic resonance absorption spectroscopy (aras). The results can be represented by the Arrhenius expression: k1=(3.95±0.35)×10−10 exp(−5919±95 K/T) cm3 molecule−1 s−1, to within ±25% over the temperature range. These results are then combined with lower temperature direct determinations, and a three parameter expression is derived which expresses the rate behavior between 256–2061 K: k1=1.69×10−17T1.10 exp(−3527 K/T) cm3 molecule−1 s−1. The experimental results are then compared to theoretical calculations that utilize ab initio potential energy surfaces that are presumably the most exact that have ever been determined. Thus, the theoretical to experimental comparison constitutes a stringent test of the ab initio surfaces and the dynamical calculations in which they are used. The conclusion from this comparison is that transition state theory supplies a high quality prediction for the rate behavior, being within ±30% of the experimental data over the entire temperature range.