ELECTRON-SPIN-RESONANCE STUDY OF THE REACTION OF H WITH D2 AT 274-K-364-K

The electron spin resonance technique has been used to study the reaction H + D2 → HD + D (1) in a flow system at 274-364 K. The decay of H atoms was measured with a range of concentrations, flow rates, and flow patterns for reactants and unreactive gases to check for possible competing reactions or systematic errors. The rate constants obtained indicate that the Arrhenius plot for reaction 1 is less curved then suggested by an earlier study. A transition-state model incorporating tunneling through an Eckart barrier was fit to the present data and earlier data. The fitted barrier height was found to be 40.4 ± 0.8 kJ mol-1; the transition-state bending term value, 723 ± 146 cm-1; and the characteristic tunneling temperature, 213 ± 32 K. These parameters agree with the results of ab initio calculations. © 1990 American Chemical Society.