Classical trajectory calculations of the high pressure limiting rate constants and of specific rate constants for the reaction H+O-2 -> HO2: dynamic isotope effects between tritium plus O-2 and muonium plus O-2

Abstract

The potential energy surface of the reaction H + O-2 --> HO2 is characterized by ab initio calculations. Based on these results, classical trajectory calculations of the capture of T, D, H, and muonium by O-2 are made. Thermal rate constants as well as energy- and angular momentum-specific rate constants are determined. The calculated high pressure recombination rate constants at 300 K agree well with the limited experimental information available so far which gives confidence in the computed temperature dependence (calculations over the temperature range 30 to 5000 K). The calculated rate coefficients are represented in comparison to results from phase space theory which leads to the rigidity factors of the reaction. Markedly nonadiabatic dynamics is observed in the case of muonium + O-2 while the reaction T + O-2 approaches adiabatic dynamics. The observed dynamic isotope effect is most pronounced at low temperatures whereas it nearly disappears at high temperatures.