Temperature dependence of the rate constant of ionic analogs of H + H _2 → H _2 + H reaction by quantum instanton method

摘要

Rate constant ratios k(T)/k(1,500K) for two symmetrical reactions H ~- + H _2 → H _2 + H ~- and H ~+ + H _2 → H _2 + H ~+ are reported. Direct method based on quantum instanton approximation for evaluation of the temperature dependence of the quantum-mechanical reaction rate constant is used. Implementation of the theory involves thermodynamic integration and path integral Monte Carlo method. Results of anionic case shows resemblance to neutral case, whereas cationic case is significantly different and below 1,000K rate constant shows strong deviation form linearity of Arrhenius plot due to high activation barrier.